Liquid flow rate measurement apparatus, dissolved oxygen measurement apparatus, method of operating a liquid flow rate measurement apparatus, and method of cleaning a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus

Abstract

There is provided a liquid flow rate measurement apparatus, comprising: a first, working, electrode configured to be placed in a liquid flow system; and a second electrode configured to be placed in the liquid flow system and electrically connected to the first, working, electrode, the liquid flow rate measurement apparatus configured to hold the first, working, electrode at a first electrode potential value, and the second electrode configured to provide a second potential value such that the liquid flow rate measurement apparatus has a system potential: wherein, in use, when a liquid flows over the first, working, electrode, the apparatus is configured to execute a flow rate measurement step, comprising: obtaining calibration data indicative of a correlation between a current value(s) of the apparatus and a flow rate(s) of the liquid, measuring a first current response value of the apparatus, and obtaining, using the calibration data, a flow rate value determined from the first current response value, and wherein the apparatus is configured to output the flow rate determined by processing the current response value.

Description

[0001] LIQUID FLOW RATE MEASUREMENT APPARATUS, DISSOLVED OXYGEN MEASUREMENT APPARATUS, METHOD OF OPERATING A LIQUID FLOW RATE MEASUREMENT APPARATUS, AND METHOD OF CLEANING A LIQUID FLOW RATE MEASUREMENT APPARATUS AND / OR A DISSOLVED OXYGEN MEASUREMENT APPARATUS

[0002] FIELD

[0003] The present application relates to a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus.

[0004] More particularly, but not exclusively, the present application relates to liquid flow rate measurement apparatuses, dissolved oxygen measurement apparatuses, methods of measuring a liquid flow rate using a liquid flow rate measurement apparatus, and methods of cleaning a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus.

[0005] BACKGROUND

[0006] Electrochemical sensors operate through detecting the quantity of species, e.g., particles, coming into contact with them. In particular, when particles come into contact with the electrochemical sensor, the sensor may produce a current response which is measured.

[0007] For electroactive species in a solution, the concentration of a species can be measured by applying a constant potential to an electrode and measuring the current response. The resulting current response is proportional to the concentration of the species in the solution local to the electrode.

[0008] Generally, the primary aim of an electrochemical sensor is to detect the concentration of chemicals. Therefore, liquid flow rate is usually controlled or compensated for to isolate the concentration of particles, for example, providing a separate flow measurement, using a stationary liquid, or controlling the liquid flow rate. This control and / or compensation may not be feasible in flow processes with, e.g., variable liquid flow rates. Additionally, this control and / or compensation may not be feasible where liquid flow rate measurements are desired.

[0009] It is desirable to provide a sensor (e.g., an apparatus) that can utilise the rate of reaction at an electrode surface to calculate the flow rate of a liquid.

[0010] Additionally, dissolved oxygen is an electroactive species of interest; the concentration of dissolved oxygen in water is a valuable indicator of water quality.

[0011] I42354WOWithout intervention, the accuracy with which the concentration of chemicals and / or dissolved oxygen can be measured may deteriorate significantly overtime, due to deposition of contaminants onto the electrode surface.

[0012] It is desirable to provide an electrochemical sensor, e.g., an electrochemical apparatus, that can measure a flow rate of a liquid. It is also desirable to provide an electrochemical apparatus that can measure a dissolved oxygen concentration of a liquid in a flow system. It is also desirable to efficiently clean the electrochemical sensor to mitigate measurement accuracy deterioration.

[0013] It is an aim of the present application to provide the aforementioned desiderata.

[0014] BRIEF DESCRIPTION OF THE INVENTION

[0015] There is provided a liquid flow rate measurement apparatus, comprising:

[0016] a first, working, electrode configured to be placed in a liquid flow system; and a second electrode configured to be placed in the liquid flow system and electrically connected to the first, working, electrode,

[0017] the liquid flow rate measurement apparatus configured to hold the first, working, electrode at a first electrode potential value, and

[0018] the second electrode configured to provide a second potential value such that the liquid flow rate measurement apparatus has a system potential:

[0019] wherein, in use, when a liquid flows over the first, working, electrode, the apparatus is configured to execute a flow rate measurement step, comprising:

[0020] obtaining calibration data indicative of a correlation between a current value(s) of the apparatus and a flow rate(s) of the liquid, measuring a first current response value of the apparatus, and obtaining, using the calibration data, a flow rate value determined from the first current response value, and

[0021] wherein the apparatus is configured to output the flow rate determined by processing the current response value.

[0022] The liquid flow system may be a macro-fluidic liquid flow system. The liquid flow rate measurement apparatus may be configured for use in the macro-fluidic liquid flow system. The first, working, electrode may be configured to be placed in the macro-fluidic liquid flow system. The second electrode may be configured to be placed in the macro-fluidic liquid flow system.

[0023] The liquid flow rate measurement apparatus may be further configured execute a cleaning step, comprising holding the first, working, electrode at a third potential value. The third potential value may be a positive potential and is optionally greater than +1.4 volts. The liquid flow rate measurement apparatus may be configured, after determining the flow rate determined by

[0024] I42354WOprocessing the current response value, to hold the first, working, electrode at the third potential value for a cleaning time period. The liquid flow rate measurement apparatus may be further configured to hold the first, working, electrode at a fourth potential value for a second cleaning time period, wherein the fourth potential value is a negative potential value and is optionally equal to or more negative than -0.9 volts.

[0025] The liquid flow rate measurement apparatus may comprise a controller configured to execute the flow rate measurement step.

[0026] The liquid flow rate measurement apparatus may further comprise a third, counter, electrode electrically connected to the first, working, electrode and the second electrode and configured to be held at a counter potential value.

[0027] The liquid flow rate measurement apparatus may be configured to automatically set the electrode potential of the first, working, electrode; measure the current response value; and / or output the flow rate based on a predetermined programme.

[0028] The liquid flow rate measurement apparatus may be configured to execute the following in order:

[0029] hold the first, working, electrode at the first electrode potential value for a first time period;

[0030] after the first time period, during a second time period, measure a current response value of the apparatus;

[0031] obtain calibration data indicative of a correlation between a current value(s) of the apparatus and a flow rate(s) of the liquid, compare the current response value to the calibration data, the calibration data providing a liquid flow rate of the liquid corresponding to the current response value at the first electrode potential value of the first, working, electrode, and

[0032] output the flow rate determined by processing the current response value.

[0033] The liquid flow rate measurement apparatus may be further configured to hold the first, working, electrode at a third potential value. The third potential value may be equal to or greater than +1.4 volts. The first, second, and / or third potential values may be provided as a potential difference from a reference electrode value. The first, second, and / or third potential values may be provided as a potential difference from a silver / silver-chloride reference electrode value. The third potential value may be equal to or greater than +1.4 volts compared to a reference electrode value. The third potential value may be equal to or greater than +1.4 volts compared to a silver / silver-chloride reference electrode value.

[0034] I42354WOThe liquid flow rate measurement apparatus may be configured, after determining the flow rate determined by processing the current response value, to hold the first, working, electrode at the third potential value for a cleaning time period.

[0035] The liquid flow rate measurement apparatus may further include a modem configured to transmit the first current response value and / or flow rate to a remote database and / or server. The liquid flow rate measurement apparatus may further include a modem configured to transmit the first current response value and / or flow rate to a remote database and / or server.

[0036] The liquid flow rate measurement apparatus may be configured to output the first current response value and / or flow rate to a readable medium.

[0037] The liquid flow rate measurement apparatus may be to correlate the first current response value to a liquid flow rate using an empirically derived calibration curve representative of liquid flow rate versus current response value. The step of obtaining, using the calibration data, a flow rate value determined from the first current response value may comprise correlating the first current response value with the liquid flow rate using an empirically derived calibration curve representative of liquid flow rate versus current response value.

[0038] The first, working, electrode may be cylindrical in shape. The first, working, electrode may have a diameter of 0.5 to 2.0 mm. The first, working, electrode may have a diameter of 0.8 to 1.2 mm. The first, working, electrode may have a diameter of 1 mm.

[0039] The first, working, electrode and / or the second electrode may be hemispherical, cuboid, conical, or tubular, in shape. The first, working, electrode and / or the second electrode may be a film sensor having a cross or disc shape. The first, working, electrode and / or the second electrode may be a microdisk electrode.

[0040] The first, working, electrode and the second electrode may be parallel electrodes. The first, working, electrode and / or the second electrode may be concentric rings. The first, working, electrode and / or the second electrode may be an interdigitated array.

[0041] The first, working, electrode may be a platinum electrode. The first, working, electrode may be titanium, gold, silver, glassy carbon, stainless steel or another viable electrode material.

[0042] The second electrode may be a silver / silver-chloride electrode. The second electrode may be a reference electrode. The second electrode may be a silver / silver-chloride reference electrode.

[0043] I42354WOThe second electrode may be a silver electrode. The second electrode may be a pseudo-reference electrode. The second electrode may be a silver pseudo-reference electrode.

[0044] The first electrode potential value may be equal to or between -0.5 volts to -1.5 volts. The first electrode potential value may be equal to or between -0.5 volts to -1.5 volts compared to a reference electrode value. The first electrode potential value may be equal to or between -0.5 volts to -1.5 volts compared to a silver / silver-chloride reference electrode value.

[0045] When the apparatus has output the flow rate determined by processing the current response value, the apparatus may be configured to repeat the flow rate measurement step. The apparatus may be configured to output the flow rate determined by processing the current response value obtained by the repeated flow rate measurement step.

[0046] There is also provided a dissolved oxygen measurement apparatus, comprising:

[0047] a first, working, electrode configured to be placed in a liquid flow system; and a second electrode configured to be placed in the liquid flow system and electrically connected to the first, working, electrode,

[0048] the dissolved oxygen measurement apparatus configured to hold the first, working, electrode at a first electrode potential value, and

[0049] the second electrode is configured to provide a second potential value such that the dissolved oxygen measurement apparatus has a system potential,

[0050] wherein, in use, when a liquid flows over the first, working, electrode, the apparatus is configured to execute a dissolved oxygen measurement step, comprising:

[0051] obtaining calibration data indicative of a correlation between a current value(s) of the apparatus and a dissolved oxygen content of the liquid, measuring a first current response value of the apparatus, and obtaining, using the calibration data, a dissolved oxygen content value determined from the first current response value, and wherein the apparatus is configured to output the dissolved oxygen content of the liquid flow determined by processing the current response value.

[0052] The liquid flow system may be a macro-fluidic liquid flow system. The dissolved oxygen measurement apparatus may be configured for use in a macro-fluidic liquid flow system. The first, working, electrode may be configured to be placed in the macro-fluidic liquid flow system. The second electrode may be configured to be placed in the macro-fluidic liquid flow system.

[0053] The apparatus may further be configured to execute:

[0054] an oxygen evolution cleaning step, comprising setting the first, working, electrode to an oxygen evolution cleaning potential, holding the first, working, electrode at

[0055] I42354WOthe oxygen evolution cleaning potential for a oxygen evolution period of time, wherein the second cleaning potential is positive; and

[0056] a hydrogen evolution cleaning step, comprising setting the first, working, electrode to a hydrogen evolution cleaning potential, holding the first, working, electrode at the hydrogen evolution cleaning potential for a hydrogen evolution period of time, wherein the hydrogen evolution cleaning potential is a negative potential.

[0057] The apparatus may be further configured to execute a preliminary cleaning step prior to the oxygen evolution potential cleaning step, comprising setting the first, working, electrode to a preliminary cleaning potential, holding the first, working, electrode at the preliminary cleaning potential for a first period of time, wherein the preliminary cleaning potential is a positive potential, and wherein the oxygen evolution positive cleaning potential is more positive than the preliminary cleaning potential.

[0058] The first, working, electrode may be cylindrical in shape. The first, working, electrode may have a diameter of 0.5 to 2.0 mm. The first, working, electrode may have a diameter of 0.8 to 1.2 mm. The first, working, electrode may have a diameter of 1 mm.

[0059] The dissolved oxygen measurement apparatus may be configured to execute:

[0060] a rest step, comprising setting the first, working, electrode to a rest potential, holding the first, working, electrode at the rest potential for a rest period of time.

[0061] The dissolved oxygen measurement apparatus may further comprise a controller configured to execute:

[0062] the dissolved oxygen measurement step; and / or

[0063] the preliminary cleaning step; and / or

[0064] the oxygen evolution cleaning step; and / or

[0065] the hydrogen evolution cleaning step; and / or

[0066] the rest step, if present.

[0067] The preliminary cleaning potential may be equal to or between +0.7 volts to +1.2 volts. The oxygen evolution cleaning potential may be equal to or greater than +1.4 volts. The hydrogen evolution cleaning potential may be equal to or more negative than -0.9 volts. The rest potential may be equal to or between +0.1 volts to +0.7 volts. The preliminary cleaning potential, oxygen evolution cleaning potential, hydrogen evolution cleaning potential, and / or rest potential may have a potential as described herein in relation to reference electrode, such as a silver / silver-chloride reference electrode. The preliminary cleaning potential may be equal to or between +0.7 volts to +1.2 volts compared to a reference electrode value, such as a silver / silver-chloride reference electrode value. The oxygen evolution cleaning potential may be equal to or greater than +1.4 volts compared to a reference electrode value, such as a silver / silver-chloride reference electrode value. The hydrogen

[0068] I42354WOevolution cleaning potential may be equal to or more negative than -0.9 volts compared to a reference electrode value, such as a silver / silver-chloride reference electrode value. The rest potential may be equal to or between +0.1 volts to +0.7 volts compared to a reference electrode value, such as a silver / silver-chloride reference electrode value.

[0069] The dissolved oxygen measurement apparatus may further include a third, counter, electrode electrically connected to the first, working, electrode and the second electrode, the third, counter, electrode configured to be held at a counter potential value.

[0070] The dissolved oxygen measurement apparatus may be configured to automatically:

[0071] set the electrode potential of the first, working, electrode to the first electrode potential; and / or set the electrode potential of the first, working, electrode to the oxygen evolution, preliminary, and / or hydrogen evolution cleaning potential(s), if present; and / or

[0072] set the electrode potential of the first, working, electrode to the rest potential measure the current response value; and / or

[0073] output the dissolved oxygen content of the liquid,

[0074] based on a predetermined programme.

[0075] There is also provided a method of operating a liquid flow rate measurement apparatus, the liquid flow rate measurement apparatus comprising:

[0076] a first, working, electrode configured to be placed in a liquid flow system;

[0077] a second electrode configured to be placed in the liquid flow system and electrically connected to the first, working, electrode; wherein:

[0078] the first, working, electrode is configured to be held at a measurement electrode potential value, and

[0079] the second electrode is configured to provide a counter potential value such that the liquid flow rate measurement apparatus has a system potential,

[0080] the method comprising:

[0081] flowing a liquid over the first, working, electrode;

[0082] a measurement step, comprising:

[0083] holding the first, working, electrode at the measurement potential value for a first time period;

[0084] after the first time period, measuring a first current response value of the apparatus;

[0085] a flow rate determination step, comprising:

[0086] obtaining calibration data indicative of a correlation between a current value(s) of the apparatus and a flow rate(s) of the liquid,

[0087] obtaining, using the calibration data, a flow rate value determined from the first current response value, and

[0088] I42354WOoutputting the flow rate of the liquid.

[0089] The method may include placing the liquid flow rate measurement apparatus into a macro-fluidic liquid flow system. The first, working, electrode may be configured to be placed in a macro-fluidic liquid flow system. The second electrode may be configured to be placed in the macro-fluidic liquid flow system.

[0090] The measurement potential of the first, working, electrode may be a negative potential.

[0091] The measurement potential of the first, working, electrode may be between -0.9 volts and -1.8 volts.

[0092] The method may further comprise a resting step. The resting step may comprise:

[0093] holding the first, working, electrode at a resting potential value for a resting time period. The resting potential value may be a positive potential.

[0094] The resting potential value may be equal to or between +0.1 volts and +0.7 volts. The resting potential value may be equal to or between +0.1 volts and +0.7 volts compared to a reference electrode value, such as a silver / silver-chloride reference electrode value.

[0095] The method may further include a cleaning step. The cleaning step may comprise:

[0096] holding the first, working, electrode at a cleaning electrode potential for a cleaning time period. The cleaning electrode potential may be a positive potential. The cleaning potential may be a potential greater than the resting potential value, if present.

[0097] The cleaning electrode potential may be equal to or greater than +1.4 volts. The cleaning electrode potential may be equal to or greater than +1.4 volts compared to a reference electrode value, such as a silver / silver-chloride reference electrode value.

[0098] The method may comprise the following steps, in order:

[0099] a) the measurement step;

[0100] b) the flow rate determination step;

[0101] c) the resting step; and

[0102] d) the cleaning step.

[0103] Steps (a) to (d) may be repeated at least once.

[0104] The method may further comprise a second cleaning step, wherein the second cleaning step comprises: holding the first, working, electrode at a second cleaning electrode potential for a second

[0105] I42354WOcleaning time period. The second cleaning electrode potential may be a negative potential. The second cleaning electrode potential may be equal to or more negative than -0.9 volts

[0106] a) The measurement step; and / or

[0107] b) the flow rate determination step; and / or

[0108] c) the resting step, if present; and / or

[0109] d) the cleaning step, if present,

[0110] may be executed automatically by the liquid flow rate measurement apparatus.

[0111] There is also provided a method of cleaning a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus, the liquid flow rate measurement apparatus and / or the dissolved oxygen measurement apparatus comprising:

[0112] a first, working, electrode configured to be placed in a liquid flow system;

[0113] a second electrode configured to be placed in the liquid flow system and electrically connected to the first, working, electrode; wherein:

[0114] the first, working, electrode is configured to be held at a first electrode potential value, and

[0115] the second electrode is configured to provide a second potential value such that the liquid flow rate measurement apparatus and / or the dissolved oxygen measurement apparatus has a system potential,

[0116] the method comprising:

[0117] (a) an oxygen evolution cleaning step, comprising:

[0118] holding the first, working, electrode at an oxygen evolution cleaning potential for an oxygen evolution period of time, wherein the oxygen evolution cleaning potential is positive;

[0119] (b) a hydrogen evolution cleaning step, comprising

[0120] holding the first, working, electrode a hydrogen evolution cleaning potential for a hydrogen evolution period of time, wherein the third cleaning potential is a negative potential.

[0121] The method may further comprise:

[0122] a preliminary cleaning step, comprising:

[0123] holding the first, working, electrode at a preliminary cleaning potential for a preliminary period of time, wherein the preliminary cleaning potential is a positive potential, and wherein the oxygen evolution potential is more positive than the preliminary cleaning potential.

[0124] The method may further include:

[0125] (d) a rest step.

[0126] I42354WOThe rest step may comprise:

[0127] holding the first, working, electrode at a rest potential for a resting period of time.

[0128] The rest potential may be a less positive potential than the first cleaning potential.

[0129] The method may further comprise:

[0130] (e) a dissolved oxygen measurement step.

[0131] The dissolved oxygen measuring step may comprise:

[0132] holding the first, working, electrode at a dissolved oxygen measurement potential for a dissolved oxygen measurement period of time, wherein the measurement potential is less negative than the hydrogen evolution cleaning potential;

[0133] obtaining calibration data indicative of a correlation between a current value(s) of the apparatus and a dissolved oxygen content of the liquid;

[0134] obtaining, using the calibration data, a dissolved oxygen content value determined from the current response value, and

[0135] outputting the dissolved oxygen content of the liquid.

[0136] The measurement potential may be less negative than the hydrogen evolution cleaning potential.

[0137] The dissolved oxygen measuring step may comprise:

[0138] measuring the current response value of the apparatus, correlating the current response value of the apparatus and outputting the dissolved oxygen content determined by processing the current response value.

[0139] The method may further comprise:

[0140] (f) a flow rate measurement step.

[0141] The flow rate measurement step may comprise:

[0142] holding the first, working, electrode at a flow rate measurement potential value for a flow rate measurement period of time, wherein the flow rate measurement potential is a negative potential;

[0143] measuring a current response value of the apparatus;

[0144] obtaining calibration data indicative of a correlation between a current value(s) of the apparatus and a flow rate(s) of the liquid;

[0145] obtaining, using the calibration data, a flow rate value determined from the current response value, and

[0146] outputting the flow rate of the liquid.

[0147] I42354WOThe flow rate measurement potential may be a negative potential.

[0148] The flow rate measurement potential and the hydrogen evolution cleaning potential may be equivalent. The flow rate measurement step may be performed during the hydrogen evolution cleaning step.

[0149] The first cleaning potential may be equal to or between +0.7 volts and +1 .2 volts. The first cleaning potential may be equal to or between +0.7 volts and +1.2 volts compared to a reference electrode value, such as a silver / silver-chloride reference electrode value.

[0150] The second cleaning potential may be equal to or more positive than +1.4 volts. The second cleaning potential may be equal to or more positive than +1.4 volts compared to a reference electrode value, such as a silver / silver-chloride reference electrode value.

[0151] The third cleaning potential may be equal to or more negative than -0.9 volts. The third cleaning potential may be equal to or more negative than -0.9 volts compared to a reference electrode value, such as a silver / silver-chloride reference electrode value.

[0152] The rest potential, if present, may be equal to or between +0.1 volts and +0.7 volts. The rest potential, if present, may be equal to or between +0.1 volts and +0.7 volts compared to a reference electrode value, such as a silver / silver-chloride reference electrode value.

[0153] The dissolved oxygen measurement potential may be equal to or between -0.4 volts and -0.8 volts. The dissolved oxygen measurement potential may be equal to or between -0.4 volts and -0.8 volts compared to a reference electrode value, such as a silver / silver-chloride reference electrode value.

[0154] The flow rate measurement potential may be equal to or between -0.9 volts and -1.8 volts. The flow rate measurement potential may be equal to or between -0.9 volts and -1.8 volts compared to a reference electrode value, such as a silver / silver-chloride reference electrode value.

[0155] The method may be executed in the following order:

[0156] (a) the preliminary cleaning step;

[0157] (b) the oxygen evolution cleaning step;

[0158] (c) the hydrogen evolution cleaning step;

[0159] (d) the rest step, if present; and

[0160] (e) the dissolved oxygen measurement step, if present, and / or

[0161] (f) the flow rate measurement step, if present.

[0162] I42354WOThere is also provided a computer readable medium having instructions stored thereon which, when executed by a processor, cause the performance of a method of operating a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus as described herein.

[0163] There is also provided a computer program comprising instructions which, when executed by a processor, cause the performance of a method of operating a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus as described herein.

[0164] There is also provided a system comprising at least one processor and a computer readable medium, wherein the computer readable medium has instructions stored thereon which, when executed by the at least one processor, cause the system to perform a method of operating a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus as described herein.

[0165] There is also provided a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus comprising at least one processor and a computer readable medium, wherein the computer readable medium has instructions stored thereon which, when executed by the at least one processor, cause the liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus to perform a method of operating a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus as described herein.

[0166] BRIEF DESCRIPTION OF THE FIGURES

[0167] In orderthatthe present disclosure may be more readily understood, preferable embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0168] FIGURE 1 is a side cutaway view of a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus in a flow system, embodying the present disclosure;

[0169] FIGURE 2 is a side view of a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus, embodying the present disclosure;

[0170] FIGURE 3 is a side cutaway view of a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus in a flow system, embodying the present disclosure;

[0171] FIGURE 4 is a side view of a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus in a flow system, embodying the present disclosure;

[0172] FIGURE 5 is a block diagram of a method of operating a liquid flow rate measurement apparatus, embodying the present disclosure;

[0173] FIGURE 6 is a block diagram of a method of operating a liquid flow rate measurement apparatus, embodying the present disclosure;

[0174] I42354WOFIGURE 7 is a block diagram of a method of cleaning a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus, embodying the present disclosure; and FIGURE 8 is a side view of a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus in a flow system, embodying the present disclosure.

[0175] DETAILED DESCRIPTION OF THE DISCLOSURE

[0176] Liquid flow rate measurement apparatus 10

[0177] As shown in Figures 1 to 4 and 8, there is provided a liquid flow rate measurement apparatus 10. The liquid flow rate measurement apparatus 10 may be considered to be a liquid flow sensor. Accordingly, there is also provided a liquid flow rate measurement apparatus 10 as described herein for carrying out the method of operating (and / or cleaning) a liquid flow rate measurement apparatus 10, as described in more detail herein. The liquid flow rate measurement apparatus 10 comprises a first, working, electrode 12 configured to be placed in a liquid flow system 2 and a second electrode 14 configured to be placed in the liquid flow system 2 and electrically connected to the first, working, electrode 12.

[0178] As will be appreciated, the first, working, electrode 12 and the second electrode 14 may form a complete electrical circuit across the liquid. Additionally, the first, working, electrode 12 and the second electrode 14 may be placed in close proximity to one-another, e.g., adjacent or close-to-adjacent to one-another (e.g., up to 5cm). Such close proximity may improve the electrical connection between the first, working, electrode 12 and the second electrode 14. As will also be appreciated, the first, working, electrode 12 and the second electrode 14 need not be directly adjacent one-another, but may instead be located a certain distance away from each other, e.g., up to ten times the distance corresponding to a diameter of the first, working, electrode 12 (e.g., up to 10 cm), as long as the electrical circuit is complete.

[0179] The liquid flow rate measurement apparatus 10 is configured to hold the first, working, electrode 12 at a first electrode potential value, and the second electrode 14 is configured to provide a second potential value such that the liquid flow rate measurement apparatus 10 has a system potential. The second electrode 14 may therefore be used to calibrate the first, working, electrode 12 potential value (e.g., taking into account the system potential). In otherwords, the second electrode 14 may provide a baseline and / or reference point for determining the first, working, electrode 12 potential value. In particular, the second electrode 14 may provide the starting point for the measurement of the potential of the first, working, electrode 12, such that the potential of the first, working, electrode 12 may be determined relative to the starting point.

[0180] In use, when a liquid flows overthe first, working, electrode 12, the apparatus is configured to execute a flow rate measurement step, comprising obtaining calibration data indicative of a correlation

[0181] I42354WObetween a current value(s) of the apparatus and a flow rate(s) of the liquid, measuring a first current response value of the apparatus 10, and obtaining, using the calibration data, a flow rate value determined from the first current response value. As will be appreciated, and as described in more detail herein, the current response value of the liquid flow rate measurement apparatus 10 may be measured by an ammeter 22 electrically connected within the apparatus, e.g., connected between the first, working, electrode 12 and the second electrode 14. Therefore, the current response value of the liquid flow rate measurement apparatus 10 may be measured between the first, working, electrode 12 and the second electrode 14.

[0182] The apparatus 10 is configured to output the flow rate determined by processing the current response value. As described in more detail herein, the liquid flow rate measurement apparatus 10 may be configured to repeat the aforementioned steps, i.e., the flow rate measurement step and / or the step of outputting the flow rate (and / or cleaning step(s), described herein).

[0183] As shown in Figure 1 , the liquid flow rate measurement apparatus 10 may comprise a controller 30. The controller 30 may be configured to execute the flow rate measurement step. The controller 30 may be electrically connected to the first, working, electrode 12 and the second electrode 14 (and, if present, as described in more detail herein, a third, counter, electrode 16). The controller 30 may be wirelessly connected to the liquid flow rate measurement apparatus 10 for controlling the first, working, electrode 12 and the second electrode 14 (and, if present, as described in more detail herein, a third, counter, electrode 16). Accordingly, the controller 30 may hold the first, working, electrode 12 at the first electrode potential and / or the controller 30 may hold the second electrode 14 at the second potential value. The controller 30 may hold the third, counter, electrode 16, if present, at a counter potential as described in more detail herein. The controller 30 may execute the step(s) (e.g., holding the first, working, electrode 12 at the potential value(s) as described herein) automatically.

[0184] The liquid flow rate measurement apparatus 10 may include the controller 30 for processing the measured current response value, and therefore for measuring the flow rate of a liquid using the current response value of the apparatus 10. As described herein, the controller 30 may also control the setting of potential(s) of the first, working, electrode 12, the second electrode 14, and / orthe third electrode 16, if present.

[0185] The liquid flow rate measurement apparatus 10 may provide a processing device (e.g., the controller 30) to determine, from the calibration data and the measured first current response value of the apparatus 10, a flow rate value of the liquid. The liquid flow rate measurement apparatus 10 may provide a measurement device (e.g., an ammeter 22 as described in more detail herein) to measure the current response value of the liquid flow rate measurement apparatus 10. The liquid flow rate

[0186] I42354WOmeasurement apparatus 10 may provide a data set including the calibration data indicative of a correlation between a current value(s) of the apparatus and a flow rate(s) of the liquid.

[0187] As described herein, the calibration data may be based on the first electrode potential value of the first, working, electrode 12. Additionally or alternatively, the data set may include a plurality of data sets, e.g., multiple sets of calibration data indicative of flow rate of a number of different liquids at multiple potentials of the first, working, electrode 12. The controller 30 may select calibration data based on the liquid of the flow system. The controller 30 may select calibration data based on an input from an operator.

[0188] As will be appreciated, the controller 30 may carry out any, any combination of, or all of the method step(s) as described herein, particularly with reference to the method of operating a liquid flow rate measurement apparatus 10, and / or the method of operating the dissolved oxygen measurement apparatus 100, and / or the method of cleaning a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus, as described herein.

[0189] The liquid flow rate measurement apparatus 10 may comprise any of, any combination of, or all of the features and advantages of the dissolved oxygen measurement apparatus 100 as described herein. Accordingly, as shown in Figures 1 to 4, the liquid flow rate measurement apparatus 10 and the dissolved oxygen measurement apparatus 100 may share features and / or advantages.

[0190] As will be appreciated, when the liquid flow rate measurement apparatus 10 is placed in a liquid flow system 2, the first, working, electrode 12 may therefore include an electroactive surface that may be positioned adjacent to the flow to be measured.

[0191] As described herein, the liquid may be water. The liquid may be drinking (potable) water, raw water, wastewater, cooling water, etc. Alternatively, the liquid may include water, and may include other components, e.g., the liquid may be a water-based liquid, such as a carbonated beverage. Alternatively, the liquid may be a solution absent of water. Flow of liquid (or fluids) other than water may be measured, for example when the solution contains a known concentration of an electroactive substance, and / or where the response of the electroactive species may be predictable against flow, and / or wherein other components of the solution may be predictable and possible to control against. Such concentrations, responses, or predictions as described herein may be known or may be measured and combined with the measured current response from the apparatus, e.g., to remove their respective impact on the output (i.e., the flow rate) of the liquid flow rate measurement step. The liquid may be part of a large-scale, or macro-fluidic scale, system.

[0192] Microfluidic flow systems and / or flow environments may utilise typical channel diameters (e.g., microfluidic pipe diameters) of between 10 micrometres to 100 micrometres; in such microfluidic flow

[0193] I42354WOsystems, flow rates may have a typical flow rate ranging between nanolitre-per-minute-scale to microlitre-per-minute scale. The liquid flow rate measurement apparatus 10 (and / or the dissolved oxygen measurement apparatus 100) as described herein may be used in large-scale fluid processes such as macro-fluidic liquid flow systems, for example water distribution networks, water treatment processes, and / or soft drink processing. Therefore, the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 as described herein may be placed (and used) in a macro-fluidic fluid environment or system, e.g., flow environments or systems having greater flow rates than, e.g., microfluidic fluid environments (i.e., macro-fluidic liquid flow processes, such as raw water systems, wastewater systems, cooling water systems, carbonated beverage production systems, etc.).

[0194] For example, liquid flow rates in macro-fluidic liquid flow systems and / or environments may at least 0.1 litres per minute. Liquid flow rates in macro-fluidic liquid flow systems and / or environments may be at least 1 litre per minute. Liquid flow rates in macro-fluidic liquid flow systems and / or environments (for example large-scale fluid systems) may be up to 2,500 litres per minute. Liquid flow rates in particularly large-scale macro-fluidic liquid flow systems and / or environments may be up to 46,000 litres per minute. For example, an industrial water system may have particularly large liquid flow rates of up to 46,000 litres per minute. As described above, smaller scale macro-fluidic liquid flow systems and / or environments may have a liquid flow rate of at least 1 litre per minute; or at least 0.1 litres per minute (for example in a domestic water system). Therefore, liquid flow rates in macro-fluidic liquid flow systems may range from 0.1 litre per minute to 46,000 litres per minute. As will be appreciated, in macro-fluidic liquid flow systems, particularly large-scale macro-fluidic liquid flow systems, the liquid flow rate measurement apparatus 10 may be configured to be placed in a portion, e.g., a pipe, of such a system (the portion or pipe having a flow rate a proportion of the total liquid flow rate of the macro-fluidic liquid flow system). In particular, as described herein, the first, working electrode 12, second electrode 14, and / or third, counter, electrode 16 (if present) may be configured to be placed in the macro-fluidic liquid flow system (or a portion, such as a pipe, of the macro-fluidic liquid flow system). Accordingly, as will be appreciated, reference to the macro-fluidic liquid flow system herein may refer to a flow system (or flow pathway such as a pipe) capable of macro-fluidic liquid flow rates as described herein, for example a portion of a larger system, where the macro-fluidic liquid flow system (or portion) is capable of the macro-fluidic liquid flow rates as described herein. In macro-fluidic liquid flow systems and / or environments, the velocity of the liquid (e.g., water) may be the principal transport mechanism of an electroactive substance (e.g., water molecules) rather than diffusion (e.g., as in microfluidic environments). For example, a liquid flow rate of 0.1 litres per minute in a pipe of a macro-fluidic liquid flow system having a 15 mm diameter may have a flow velocity of approximately 0.01 metres per second. Accordingly, the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 as described herein may be configured to be placed in a pipe of a flow system having a liquid flow rate (or flow rate capacity) of at least 0.1 litres per minute. The liquid flow rate measurement apparatus 10 and / or

[0195] I42354WOthe dissolved oxygen measurement apparatus 100 as described herein may be configured to be placed in a pipe of a flow system having a liquid flow rate (or a flow rate capacity) of (or of at least) 0.1 litres per minute; or 1 litre per minute; or 10 litres per minute; or 100 litres per minute; or 1000 litres per minute; or 2000 litres per minute; or 3000 litres per minute; or 5000 litres per minute.

[0196] As described herein, the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 as described herein may be particularly suitable for macro-scale liquid flow systems. The liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 as described herein may be particularly suitable for placement in pipe sizes corresponding to macro-scale liquid flow systems, for example, pipes greater than 0.5 cm in diameter; or greater than 1 cm in diameter; or greater than 1.5 cm in diameter; or greater than 2 cm in diameter. The liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 as described herein may be particularly suitable for use with (e.g., configured to be placed in) pipe diameter sizes up to 150 cm; or up to 100 cm; or up to 90 cm; or up to 80 cm; or up to 70 cm; or up to 60 cm; or up to 50 cm; or up to 40 cm; or up to 30 cm; or up to 20 cm; or up to 10 cm; or up to 5 cm; or up to 4 cm; or up to 3 cm, for example.

[0197] The macro-fluidic liquid flow system may additionally or alternatively be or include (e.g., large scale) open and / or natural bodies of water, for example aqueducts, rivers, streams, etc. Further, since the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 as described herein may be particularly suitable for macro-scale liquid flow systems, the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 as described herein may additionally or alternatively be particularly suitable for other macro-scale liquid systems where the sensor is moved through a large body of water, for example, when the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 is, e.g., formed of, placed on, or mounted on a vehicle (such as a boat) moving through a body of water (such as a lake, stream, river, ocean, etc.). Therefore, in such macro-fluidic liquid systems where the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 is moved through the system, the velocity of the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 through the liquid (e.g., water) may be the principal transport mechanism of an electroactive substance (e.g., water molecules) to the electrodes rather than diffusion (e.g., as in microfluidic environments). Accordingly, the liquid flow rate measurement apparatus 10 may measure velocity (or relative velocity) of the sensor (e.g., attached to a vehicle) moving through a body of water in a similar manner to that described herein with respect to measuring the flow rate of the liquid in flow systems. Similarly, the liquid flow rate measurement apparatus 10 may correlate the current response value as described herein (in liquid flow systems) to a liquid flow velocity in a similar manner to that described herein with respect to measuring the flow rate of the liquid in flow systems. Further, the dissolved oxygen measurement apparatus 100

[0198] I42354WOmay measure dissolved oxygen content of a body of water as the apparatus 100 is moved through the body of water.

[0199] Known or measured values relating to a concentration of an electroactive substance, and / or other components of the solution that may be predictable and possible to control against, and / or where the response of the electroactive species may be predictable against flow, may be included in a calculation as part of the liquid flow rate measurement step, e.g., included in the calibration data. Examples may include known or measured concentrations of liquid components, mixing ratios, and / or dilutions of liquid components that may be included in the flow rate measurement step. In particular, the values, responses, and / or calculations may be included in the current-liquid flow rate relationship, e.g., calibration data, as described in more detail herein. Such parameters may be known, for example, based on processes that combine known amounts of fluids into one flow stream, and / or may be measured, for example, such as in processes that regularly analyse the liquid content.

[0200] For example, when the flow rate measurement step results in hydrogen evolution in the liquid, liquids containing ethanol may be expected to provide a lower current response value during the measurement step than a liquid with a larger concentration of water. For example, hydrogen evolution during the flow rate measurement step may be reduced in the ethanol containing liquid due to a lower concentration of water in the total volume of liquid. Accordingly, for example, the effect of the ethanol concentration on the expected (e.g., proportional) change in the expected current response value of the first, working, electrode, e.g., when compared to water alone, may be included in the calibration data and / or step of determining the flow rate determined from the measured first current response value.

[0201] Therefore, parameters of liquid flow, e.g., concentration of water, mixing ratios, dilutions, etc., may be accounted for in order to provide an accurate flow rate.

[0202] As will be appreciated, such considerations may equally be applied to determination of dissolved oxygen content of a liquid using the dissolved oxygen measurement apparatus 100 as described herein.

[0203] Further, as described in more detail herein, the first electrode potential value may be a potential value sufficient to induce hydrogen evolution in the liquid at the surface of the first, working, electrode 12.

[0204] In a liquid flow system 2, the rate of reaction at the first, working, electrode 12 may be greater than that of a stationary solution and dependent on the rate of fluid flow. Accordingly, the fluid flow rate may be the primary variable affecting the rate of reaction and the rate of reaction may be the primary dependence for the steady state current response. Therefore, the magnitude of steady-state current response, i.e., the current response value of the liquid flow apparatus may indicate flow rate of the

[0205] I42354WOliquid in the liquid flow system 2. In particular, the fluid flow rate (and velocity) may be the primary variable for macro-fluidic liquid flow systems and / or environments as described herein.

[0206] In particular, the reduction of water to hydrogen gas and hydroxyl ions is a reaction that may be chiefly dependent on the rate of the solution moving over the electrode (e.g., particularly in macrofluidic liquid flow systems), as the concentration of water (i.e., water molecules) in water (i.e., the bulk solution) may be typically constant. It will be appreciated that other liquids may be used with the system as described herein. For example, as described herein, suitable liquids may include soft drinks (e.g., carbonated or nitrogenated liquids), alcoholic drinks (e.g., drinks containing alcohol, such as ethanol), for example.

[0207] A current response of the apparatus 10, indicating the reaction rate of these species, can therefore be used to measure the flow rate using the liquid flow rate measurement apparatus 10 as described herein. As part of the measurement as described herein, other factors may be accounted for and / or corrected for e.g., temperature, conductivity as described in more detail herein.

[0208] Accordingly, the liquid flow rate measurement apparatus 10 as described herein may provide advantages. In particular, as described herein, flow rate of a liquid in a system may often be accounted for and / or mitigated in order to be able to measure a rate of reaction. On the contrary, the present liquid flow rate measurement apparatus 10 as described herein may utilize flow of a liquid itself and measure the current response of a flow system 2 directly in order to measure a flow rate.

[0209] The current response of the liquid flow rate measurement apparatus 10 may increase as a greater volume of fluid passes over the first, working, electrode 12; higher current may therefore indicate higher flow rate. For example, a greater volume of fluid passing over the first, working, electrode 12 will have a greater fluid velocity, which may be the principal transport mechanism of electroactive substances (e.g., water molecules) in macro-fluidic liquid flow systems and / or environments. It will be appreciated that there may be a non-zero current at zero flow. Additionally, it will be appreciated that a linear increase in flow rate of the liquid may not result in a linear increase in the current response value.

[0210] The current response value of the liquid flow rate measurement apparatus 10 may be measured by an ammeter 22 electrically connected within the apparatus, e.g., connected between the first, working, electrode 12 and the second electrode 14. Accordingly, the current response value of the liquid flow rate measurement apparatus 10 may be measured between the first, working, electrode 12 and the second electrode 14. The current response value may be measured by a multimeter, for example (such as an ammeter 22 as part of a multimeter). The potential of the first, working, electrode 12, may be measured by a voltmeter 20. The potential of the first, working, electrode 12 may be measured by a multimeter, for example (such as a voltmeter 20 as part of a multimeter). The

[0211] I42354WOvoltmeter 20 may be electrically connected to the first, working, electrode 12, and the second electrode 14. When three electrodes are present, as described in more detail herein, the ammeter 22 (and / or multimeter) may be electrically connected to the first, working, electrode 12, the third, counter, electrode 16, and / or the second (reference or pseudo reference) electrode 14, and / or the voltmeter 20 (and / or multimeter) may be electrically connected to the first, working, electrode 12 and the second electrode 14 (e.g., a reference (or pseudo reference) electrode), and / or the third, counter, electrode 16. The potential and / or current response value of the liquid flow rate measurement apparatus 10 may be controlled and / or measured by a potentiostat electrically connected to the first, working, electrode 12, the second electrode 14, and, if present, the third, counter, electrode 16. As will be appreciated, the ammeter 22 and / or voltmeter 20 described herein may be embedded electronic equipment, logic controllers, controllers (e.g., controller 30), or processors configured to perform the function of measuring and / or outputting potential and / or current. In particular, the ammeter 22 and / or voltmeter 20 may be embedded electronic(s) within the housing 18 of the liquid flow rate measurement apparatus 10, for example, as part of a logic controller and / or processor.

[0212] The between the current response value and the liquid flow rate (e.g., a current- liquid flow rate relationship), e.g., the calibration data, may vary based on the liquid in the liquid flow system 2. Accordingly, the liquid flow rate measurement apparatus 10 may include a database of current- liquid flow rate relationship(s) (e.g., calibration data) corresponding to various liquids.

[0213] The current- liquid flow rate relationship for the or each liquid may be empirically derived. The currentliquid flow rate relationship may be represented by an equation, e.g., a quadratic equation. The current-liquid flow rate relationship may be represented by a second order polynomial, a third order polynomial, or fourth order polynomial, a fifth order polynomial. Accordingly, the order of polynomial may be 2, 3, 4, 5, 6, 7, 8, 9, or 10, for example. The relationship may also be exponential or logarithmic in form, or be approximated through the use of a neural network or other generalisable mathematical model, or a combination of the aforementioned methods.

[0214] The liquid flow rate measurement apparatus 10 may further include a third, counter, electrode 16 (e.g., configured to be placed into the liquid flow system 2) electrically connected to the first, working, electrode 12 and the second electrode 14 and configured to be held at a counter potential value. The counter potential value may correspond to an inverse value of the potential value of the first, working electrode 12, e.g., the first electrode potential value, (e.g., an inverse value of the potential at which the first, working, electrode 12 is held), as described in more detail herein.

[0215] As will be appreciated, the first, working, electrode 12, and / or the second electrode 14, and / or the third, counter, electrode 16 may be placed in proximity to one-another, such that the first, working, electrode 12, the second electrode 14, and the third, counter, electrode 16 form a complete electrical circuit (across the liquid). As will be appreciated, the first, working, electrode 12, the second

[0216] I42354WOelectrode 14, and the third, counter, electrode 16 may form a complete electrical circuit across the liquid. Additionally, the first, working, electrode 12, the second electrode 14, and / or the third electrode 16 may be placed in close proximity to one-another, e.g., adjacent or close-to-adjacent to one-another (e.g., up to 5cm). Such close proximity may improve the electrical connection between the first, working, electrode 12, the second electrode 14, and / or the third electrode 16. As will also be appreciated, the first, working, electrode 12, the second electrode 14, and / or the third electrode 16 need not be directly adjacent one-another, but may instead be located a certain distance away from each other, e.g., up to one-hundred times the distance corresponding to a diameter of the first, working, electrode 12 (e.g., up to 10 cm), as long as the electrical circuit is complete.

[0217] When a third, counter, electrode 16 is provided, the second electrode 14 may solely act as a reference (or pseudo-reference) electrode. Accordingly, wear on the second electrode 14 may be reduced. In particular, when two electrodes are present, the second electrode 14 may act as both a counter electrode and a reference (or pseudo reference) electrode. Accordingly, fouling and / or unwanted coating (e.g., unwanted deposition of a material) on the surface of the electrode may occur at the second electrode 14 at a slower rate if three electrodes are present in the liquid flow rate measurement apparatus 10. Accordingly, providing a liquid flow rate measurement apparatus 10 including three electrodes may increase the longevity of the liquid flow rate measurement apparatus 10.

[0218] The liquid flow rate measurement apparatus 10 may be configured to automatically set the electrode potential of the first, working, electrode 12; measure the current response value; and / or output the flow rate of the liquid based on a predetermined programme. In other words, the liquid flow rate measurement apparatus 10 may be configured to automatically execute one of, some of, or all of the steps (e.g., measurement steps, cleaning steps, resting steps) as described in more detail in relation to the method of operating a liquid flow rate measurement apparatus 10 as described in more detail herein.

[0219] The liquid flow rate measurement apparatus 10 may include a processor configured to automatically set the electrode potential of the first, working, electrode 12; measure the current response value; and / or output the flow rate based on a predetermined programme. The liquid flow rate measurement apparatus 10 may include (and / or provide) the predetermined programme. Accordingly, the liquid flow rate measurement apparatus 10 may include a processor that may execute the method steps of operating the liquid flow rate measurement apparatus 10 as described herein. The controller 30 as described herein may include the processor.

[0220] The liquid flow rate measurement apparatus 10 may be configured to detect liquid presence on the first, working, electrode 12, and / orthe second electrode 14 (and / orthe third electrode 16, if present). Accordingly, the liquid flow rate measurement apparatus 10 may be configured, on detecting liquid

[0221] I42354WO(e.g., liquid flow), to execute the measurement steps as described herein. Additionally or alternatively, the liquid flow rate measurement apparatus 10 may be configured to output a signal indicating liquid presence (e.g., output the signal to a remote location wirelessly). The signal may be output by a wireless (e.g., cellular) modem.

[0222] The liquid flow rate measurement apparatus 10 may be configured to execute the following steps in order: hold the first, working, electrode 12 at the first electrode potential value for a first time period; after the first time period, during a second time period, measure a current response value of the apparatus; obtain calibration data indicative of a correlation between a current value(s) of the apparatus and a flow rate(s) of the liquid, compare the current response value to the calibration data (e.g., current-flow rate relationship data), the calibration data providing a liquid flow rate of the liquid corresponding to the current response value at the first electrode potential value of the first, working, electrode 12, and output the flow rate determined by processing the current response value. As described herein, the liquid flow rate measurement apparatus 10 may be configured to repeat the aforementioned steps. As described herein, the liquid flow rate measurement apparatus 10 may be configured to execute (and / or repeat) the aforementioned steps automatically (e.g., using a processor and / or controller 30 configured to execute instructions).

[0223] The first time period may be considered to be a settling time period. The first time period may be 1 to 5 seconds. The first time period may be up to 90 seconds. In particular, the first time period may be 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds, 80 seconds, or 90 seconds. The second time period may be 1 to 5 seconds. The second time period may be 0.5 seconds.

[0224] The liquid flow rate measurement apparatus 10 may be configured to execute a rest step, comprising setting the first, working, electrode 12 to a rest potential and holding the first, working, electrode 12 at the rest potential for a rest time period. The rest step may be executed prior to, and / or after the step of holding the first, working, electrode 12 at the first electrode potential value for a first time period. The rest time period may be up to 86400 seconds, i.e., 24 hours. As will be appreciated, the rest time period may be equivalent to a period of ‘down time’ of the liquid flow rate measurement apparatus 10. Accordingly, the rest time period, may be any period of time suitable as a rest period between desired measurement steps. Accordingly, if only one measurement is required per day, the rest time period may therefore be up to a day. The rest time period may be 0 seconds, such that no rest time period is used, e.g., for continuous measurement. Additionally or alternatively, the first time period may be 0 seconds, such that no first time period is used, e.g., for continuous measurement. The second time period may be indefinite, e.g., for continuous measurement. The first and / or second and / or rest time periods may be adjusted or reconfigured during use of the liquid flow rate measurement apparatus 10.

[0225] I42354WOThe liquid flow rate measurement apparatus 10 may be further configured to hold the first, working, electrode 12 at a third potential value. The third potential value may be equal to or greater than +1.0 volts. The third potential value may be equal to or greater than +1.4 volts.

[0226] Reference to potential value(s) as described herein may be interpreted as a difference from a reference electrode potential value (or a pseudo-reference electrode potential value). For example, +1 .0 volts may be interpreted as +1 .0 volts from a reference electrode potential value. Accordingly, the ‘true’ potential (e.g., from 0 volts) may be less than, equal to, or greater than the potential values given herein.

[0227] In particular, as described herein, the potential value(s), such as in relation to the first, working, electrode 12 and / or the third, counter, electrode 16 as provided herein may be considered to be a potential difference from a silver / silver-chloride reference electrode potential value (which itself, may be considered to be offset +0.2 volts from a standard hydrogen electrode potential value as described in more detail herein). As described in more detail herein, the second electrode 14 may be or act as a reference (or pseudo-reference) electrode. The second electrode 14 may, therefore, provide the reference (or pseudo-reference) electrode potential value. The potential values as given herein may be considered to correspond to the potential difference of a platinum first, working, electrode 12 from a potential value of a silver / silver-chloride reference electrode (e.g., a silver / silver-chloride second electrode 14).

[0228] Accordingly, it will be appreciated that the potential value(s) as described herein may vary (e.g., may be ‘shifted’ more positive or more negative) based on the material of a reference electrode (e.g., the second electrode 14, which may provide the function of a reference electrode as described in more detail herein) and / or the material of the first, working, electrode 12.

[0229] The third potential value may correspond to a cleaning step. As described herein, the first electrode potential value (e.g., measurement potential value as described herein) may correspond to a potential of the first, working, electrode 12 sufficient to induce hydrogen evolution at the surface of the first, working, electrode 12. Therefore, deposition of species, e.g., limescale and / or platinum oxide, on the surface of the first, working, electrode 12 may occur. The third potential value may therefore cause the adsorbed species on the surface of the first, working, electrode 12 to be removed. The cleaning step may induce oxygen evolution on the surface of the first, working, electrode 12. Oxygen evolution may cause limescale on the surface of the first, working, electrode 12 to dissolve into the local solution. Accordingly, due to the cleaning step, the liquid flow rate measurement apparatus 10 itself may be configured to clean itself in use, i.e., the liquid flow rate measurement apparatus 10 may be self-cleaning, e.g., when placed in the liquid flow system (e.g., as part of online monitoring). The liquid flow rate measurement apparatus 10 itself may be configured to continually clean itself in use (e.g., between measurement cycles). Accordingly, the first, working,

[0230] I42354WOelectrode 12, and / or the second electrode 14, and / or the third, counter, electrode 16 may be cleaned by the cleaning steps and the flow rate measurement steps as described herein during use (i.e., when the liquid flow rate measurement apparatus 10 is placed into the liquid flow system 2).

[0231] The liquid flow rate measurement apparatus 10 may be configured, after determining the flow rate determined by processing the current response value, to hold the first, working, electrode 12 at the third potential value for a cleaning time period (e.g., the liquid flow rate measurement apparatus 10 may be configured to execute a cleaning step). The cleaning step may be executed prior to determining the flow rate determined by processing the current response value.

[0232] The cleaning time period may be 0.5 seconds. The cleaning time period may be 1 to 5 seconds; or 1 to 10 seconds; or 1 to 20 seconds, e.g., 5 seconds, 10 seconds, 15 seconds, or 20 seconds. The cleaning time period may be indefinite, e.g., up to or over 24 hours.

[0233] The liquid flow rate measurement apparatus 10 may further include a modem configured to transmit the first current response value and / or flow rate to a remote database and / or server.

[0234] The liquid flow rate measurement apparatus 10 may be configured to output the first current response value and / or flow rate to a readable medium.

[0235] Accordingly, the liquid flow rate measurement apparatus 10 may output a flow rate locally, e.g., if the liquid flow rate measurement apparatus 10 is connected in proximity to a control location, e.g., as part of the same electrical system. Additionally or alternatively, the liquid flow rate measurement apparatus 10 may output a flow rate remotely, e.g., to a control location not connected to the same electrical system. The liquid flow rate measurement apparatus 10 may additionally or alternatively include a display means (e.g., a screen), such that an operator may view the flow rate of a liquid directly from the liquid flow rate measurement apparatus 10.

[0236] As described herein, the liquid flow rate measurement apparatus 10 may be configured to correlate the first current response value to a liquid flow rate using an empirically derived calibration curve (e.g., the calibration date) representative of liquid flow rate versus current response value. In particular, the step of obtaining, using the calibration data, a flow rate value determined from the first current response value may comprise correlating the first current response value with the liquid flow rate using an empirically derived calibration curve representative of liquid flow rate versus current response value. The calibration curve (e.g., calibration data) may be tailored to a specific liquid to be measured. Accordingly, as described herein, the liquid flow rate measurement apparatus 10 may include one or more (e.g., multiple) calibration curves (e.g., calibration data) corresponding to various liquids to be measured.

[0237] I42354WOThe first, working, electrode 12 may be cylindrical in shape. The first, working, electrode may have a diameter of 0.5 to 2.0 mm. The first, working, electrode 12 may have a diameter of 0.8 to 1.2 mm. The first, working, electrode may have a diameter of 1 mm. The first, working, electrode may have a length of 4 mm. The first, working, electrode may have a length of 1 to 10 mm. Such an electrode size may be particularly suited for macro-fluidic liquid flow systems.

[0238] The first, working, electrode 12 and / or the second electrode 14 may be hemispherical, cuboid, conical, or tubular, in shape. The first, working, electrode 12 and / or the second electrode 14 may be a film sensor having a cross or disc shape. The first, working, electrode 12 and / or the second electrode 14 may be a microdisk electrode.

[0239] The first, working, electrode 12 and the second electrode 14 may be parallel electrodes. The first, working, electrode 12 and / or the second electrode 14 may be concentric rings (e.g., annular concentric cylinders). The first, working, electrode 12 and / or the second electrode 14 may be an interdigitated array.

[0240] As described herein, the first, working, electrode 12 may be larger than prior electrodes in in prior electrochemical systems. Such a size may be particularly suited for macro-fluidic liquid flow systems and / or environments. Additionally, having a larger electrode as described herein may provide advantages. In particular, in electrode systems having smaller electrodes, a cleaning step may strip away the surface of the electrode, such that, when smaller electrodes are used, the electrode may be destroyed in a small number of working (e.g., measurement) and cleaning cycles. The liquid flow rate measurement apparatus 10 as described herein may undergo multiple measurement and cleaning cycles without destroying the first, working, electrode 12. Further, as described herein, since the liquid flow rate measurement apparatus 10 may undergo multiple measurement and cleaning cycles, the liquid flow rate measurement apparatus 10 may be considered self-cleaning.

[0241] The first, working, electrode 12 may be a platinum electrode. The first, working, electrode 12 may may comprise silver, titanium, aluminium, platinum, stainless steel, gold, graphite, and / or glassy carbon. The first, working, electrode 12 may be formed of (or may consist of) silver, titanium, aluminium, platinum, stainless steel, gold, graphite, and / or glassy carbon.

[0242] The second electrode 14 may be a silver / silver-chloride electrode. The second electrode 14 may be a reference electrode. The second electrode 14 may be a silver / silver-chloride reference electrode. The second electrode 14 may be cylindrical in shape. The second electrode 14 may have a diameter of 1 mm. The second electrode 14 may comprise silver, titanium, aluminium, platinum, stainless steel, gold, graphite, and / or glassy carbon. The second electrode 14 may be formed of (or consist of) silver, titanium, aluminium, platinum, stainless steel, gold, graphite, and / or glassy carbon. Additionally or alternatively, the second electrode 14 may comprise Hg / HgSC (mercury / mercuric

[0243] I42354WOsulfate); Hg / Hg2Cl2 (mercury / mercury chloride, e.g., calomel or saturated calomel); copper metal; silver metal; and / or stainless steel. The second electrode 14 may be formed of (or may consist of) Hg / HgSC (mercury / mercuric sulfate); Hg / Hg2Cl2 (mercury / mercury chloride, otherwise known as calomel or saturated calomel); copper metal; silver metal; and / or stainless steel.

[0244] The second electrode 14 may be a silver electrode. The second electrode 14 may be a pseudoreference electrode. The second electrode 14 may be a silver pseudo-reference electrode.

[0245] The first electrode potential value may be sufficient to induce hydrogen evolution on the surface of the first, working, electrode 12. The first electrode potential value may be between -0.5 volts to -1.5 volts. As described above, it will be appreciated that the potential values (e.g., the first electrode potential value, second potential value, third potential value, etc.) as described herein may be described in relation to a difference from the potential of a reference electrode (e.g., a silver / silver-chloride electrode) or a pseudo-reference electrode (e.g., a silver electrode), such as the second electrode 14, and may not be described in relation to an absolute value of voltage.

[0246] The third, counter, electrode 16, if present, may be a steel electrode. The third, counter, electrode 16, if present, may be a steel coated electrode. The third, counter, electrode 16 may be cylindrical. The third, counter, electrode 16 may be a polygonal, e.g., rectangular, prism. The third, counter, electrode 16 may be hemispherical, cuboid, conical, or tubular, in shape. The third, counter, electrode 16 may be a film sensor having a cross or disc shape. The third, counter, electrode 16 may be a microdisk electrode. The first, working, electrode 12 and / or the second electrode 14 and the third, working electrode 16 may be parallel electrodes. The first, working, electrode 12 and / or the second electrode 14 and the / or the third, working, electrode 16 may be concentric rings (e.g., annular concentric cylinders). The first, working, electrode 12 and / or the second electrode 14 and / or the third, working, electrode 16 may be an interdigitated array.

[0247] The liquid flow rate measurement apparatus 10 may have a housing, e.g., housing 18 as described in more detail herein. The third, counter, electrode 16 may form part of the housing, e.g., the third, counter, electrode 16 may extend from the housing 18, or may be the housing 18 itself. In other words, when the liquid flow rate measurement apparatus 10 is described as an electrochemical sensor, the third, counter, electrode 16 may form part (or all) of a body of the sensor. As shown in Figure 8, the third, counter, electrode 16 may be formed of an annular cylindrical shape, e.g., the third, counter, electrode 16 having an annular thickness, and hollow space within, where the first, working, electrode 12 and / or the second electrode 14 may be located (and / or electronics may be located).

[0248] The third, counter, electrode 16 may be any metallic or conductive material, such as copper, steel, magnesium, zinc, and / or graphene, for example.

[0249] I42354WOThe third, counter, electrode 16 may have a diameter of up to 12 mm. The third, counter, electrode 16 may have a diameter of up to 20 mm. The third, counter, electrode 16 may have a diameter of up to 30 mm. The third, counter, electrode 16 may have a diameter of up to and including 10; 20; 30; 40; 50; 60; 70; 80; 90; or 100 times diameter of the first, working, electrode 12. The counter electrode may prevent or substantially reduce the formation of undesired material coating(s) on the reference electrode, and such coating(s) may therefore form on the third, counter, electrode 16. It will be appreciated that more than three electrodes may be used in the liquid flow rate measurement apparatus 10 as described herein, the number of electrodes being determined by the purpose and system within which the apparatus is placed within.

[0250] As described herein, the third, counter, electrode 16 may provide a counter potential to the first, working, electrode 12, such that when the first, working, electrode 12 is held at a positive potential as described herein, the third, counter, electrode 16 may be held at a corresponding negative potential (and similarly when the first, working, electrode 12 is held at a negative potential, the third, counter, electrode may be held at a corresponding positive potential). The counter potential value may correspond to an inverse value of the potential value of the first, working electrode 12, e.g., the first electrode potential value (e.g., an inverse value of the potential at which the first, working, electrode 12 is held). For example, if the first, working, electrode is held at a first electrode potential value of -0.5 volts, the counter potential may therefore be +0.5 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). Accordingly, when the first, working, electrode 12 undergoes a measurement step (at, e.g., a negative potential), the third, counter, electrode 16 may undergo a cleaning step by virtue of being held at a counter (e.g., positive) potential. Accordingly, the third, counter, electrode 16 may undergo multiple cleaning cycles. When a large steel electrode is used as the third, counter, electrode 16, any surface stripping that may occur due to potential cycling (e.g., negative, to positive, to negative, etc.) may be negligible when considering the dimensions of the third, counter, electrode 16. Accordingly, the longevity of the third, counter, electrode 16 may be increased.

[0251] A proportionally large third, counter, electrode 16 (e.g., the third, counter, electrode 16 having a large diameter and / or large surface area in proportion to the first, working, electrode 12) may provide increased longevity of the third, counter, electrode 16. In particular, due to a larger surface area than a proportionally smaller electrode, the charge density over a large electrode may be lower than a smaller electrode. In particular, a larger electrode may have a larger surface area to conduct charge to a liquid than a smaller electrode for the same charge. Accordingly, the rate of surface reaction for a larger electrode may be lower than a proportionally smaller electrode.

[0252] As shown in Figures 2, 4, and 8, the liquid flow rate measurement apparatus 10 may include a housing 18 for housing electronics, e.g., a potentiostat, voltmeter 20, ammeter 22, controller 30, etc.

[0253] I42354WOAccordingly, the liquid flow rate measurement apparatus 10 may be configured as a single unit. The liquid flow rate measurement apparatus 10 may be modularly installable into the flow system 2. For example, the liquid flow rate measurement apparatus 10 may be readily removable from the liquid flow system 2 and re-installable elsewhere, where required.

[0254] As described herein with relation to the method of operating the liquid flow rate measurement apparatus 10, the method may include repeating the measurement step(s) and the flow rate determination step(s) as described herein. Accordingly, as described herein, the liquid flow rate measurement apparatus 10 may be configured to repeat the flow rate measurement step and the step of outputting the flow rate determined by processing the current response value. The liquid flow rate measurement apparatus 10 may be configured to repeat the flow rate measurement step a plurality of times and the step of outputting the flow rate determined by processing the current response value a plurality of times. Additionally or alternatively, the method may include a cleaning step or steps (e.g., the cleaning steps corresponding to the method of cleaning a liquid flow rate measurement apparatus 10 as described herein) after determining the flow rate of the liquid. Therefore, the liquid flow rate measurement apparatus 10 may be configured to perform the cleaning step or steps (e.g., the cleaning steps corresponding to the method of cleaning a liquid flow rate measurement apparatus 10 as described herein) after determining the flow rate of the liquid and outputting the flow rate determined by processing the current response value. As will also be appreciated, the cleaning step(s) as described herein may be executed prior to any measurement and / or flow rate determination step.

[0255] Dissolved oxygen measurement apparatus 100

[0256] As is shown in Figures 1 to 4 and 8, there is also provided a dissolved oxygen measurement apparatus 100. The dissolved oxygen measurement apparatus 100 may be considered to be a dissolved oxygen sensor. Accordingly, there is provided a dissolved oxygen measurement apparatus 100 for carrying out the method of cleaning a dissolved oxygen measurement apparatus 100, as described in more detail herein. The dissolved oxygen measurement apparatus 100 may comprise any of, any combination of, or all of the features and advantages of the liquid flow rate measurement apparatus 10 as described herein. Accordingly, as shown in 1 to 4, the dissolved oxygen measurement apparatus 100 and the liquid flow rate measurement apparatus 10 may share features and / or advantages. Therefore, for features shared between the liquid flow rate measurement apparatus 10 and the dissolved oxygen measurement apparatus 100 as described herein, e.g., the first, working, electrode and the second electrode, the reference numerals used herein are equivalent with the addition of 100.

[0257] The dissolved oxygen measurement apparatus 100 comprises a first, working, electrode 112 configured to be placed in a liquid flow system 2; a second electrode 114 configured to be placed in

[0258] I42354WOthe liquid flow system 2 and electrically connected to the first, working, electrode 112; the dissolved oxygen measurement apparatus 100 configured to hold the first, working, electrode 112 at a first electrode potential value, and the second electrode 114 is configured to provide a second potential value such that the dissolved oxygen measurement apparatus 100 has a system potential.

[0259] The second electrode 114 may therefore be used to calibrate the first, working, electrode 112 potential value (e.g., taking into account the system potential). In other words, the second electrode 114 may provide a baseline and / or reference point for determining the first, working, electrode 112 potential value. In particular, the second electrode 114 may provide the starting point for the measurement of the potential of the first, working, electrode 112, such that the potential of the first, working, electrode 112 may be determined relative to the starting point.

[0260] The dissolved oxygen measurement apparatus 100 may be used in flow systems including any of the liquids described in relation to the liquid flow rate measurement apparatus 10 as described herein. It will also be appreciated that the dissolved oxygen measurement apparatus 100 may be used in liquid systems including stationary water. Accordingly, reference to a “liquid flow system” as described herein may also apply to a system having stationary liquid, i.e., not including liquid flow.

[0261] In particular, as described herein, the liquid may be water. The liquid may be drinking (potable) water, raw water, wastewater, cooling water, etc. Alternatively, the liquid may include water, and may include other components, e.g., the liquid may be a water-based liquid, such as a carbonated beverage and / or liquid containing alcohol (e.g., ethanol) or other components. Alternatively, the liquid may be a solution absent of water. As described herein in relation to the liquid flow rate measurement apparatus 10, the liquid may be part of a large-scale, or macro-fluidic scale, system. Accordingly, the dissolved oxygen measurement apparatus 100 as described herein may be used in large-scale fluid processes such as macro-fluidic liquid flow systems, for example water distribution networks or soft drink processing. Therefore, the dissolved oxygen measurement apparatus 100 as described herein may be placed (and used) in a macro-fluidic fluid environment or system, e.g., flow environments or systems having greater flow rates than, e.g., microfluidic fluid environments (i.e., macro-fluidic flow processes, such as raw water systems, wastewater systems, cooling water systems, carbonated beverage production systems, etc.).

[0262] For example, liquid flow rates in macro-fluidic liquid flow systems and / or environments may be at least 0.1 litres per minute. Liquid flow rates in macro-fluidic liquid flow systems and / or environments may be at least 1 litre per minute. Liquid flow rates in macro-fluidic liquid flow systems and / or environments (for example large-scale fluid systems) may be up to 2,500 litres per minute. Liquid flow rates in particularly large-scale macro-fluidic liquid flow systems and / or environments may be up to 46,000 litres per minute. For example, an industrial water system may have particularly large flow rates of up to 46,000 litres per minute. As described above, smaller scale macro-fluidic liquid

[0263] I42354WOflow systems and / or environments may have a liquid flow rate of at least 1 litre per minute; or at least 0.1 litres per minute (for example in a domestic water system). Therefore, liquid flow rates in macrofluidic liquid flow systems may range from 0.1 litre per minute to 46,000 litres per minute. As will be appreciated, in macro-fluidic liquid flow systems, particularly large-scale macro-fluidic liquid flow systems, the dissolved oxygen measurement apparatus 100 may be configured to be placed in a portion, e.g., a pipe, of such a system (the pipe having a flow rate a proportion of the total flow rate of the macro-fluidic liquid flow system). In particular, as described herein, the first, working electrode 112, second electrode 114, and / or third, counter, electrode 116 (if present) may be configured to be placed in the macro-fluidic liquid flow system (or a portion, such as a pipe, of the macro-fluidic flow system). Accordingly, as will be appreciated, reference to the macro-fluidic liquid flow system herein may refer to a flow system (or flow pathway such as a pipe) capable of macro-fluidic liquid flow rates as described herein, for example a portion of a larger system, where the macro-fluidic liquid flow system (or portion) is capable of the macro-fluidic liquid flow rates as described herein. In such macro-fluidic liquid flow systems and / or environments, the velocity of the liquid (e.g., water) may be the principal transport mechanism of an electroactive substance (e.g., water molecules) rather than diffusion (as in microfluidic environments). For example, a liquid flow rate of 0.1 litres per minute in a pipe of a macro-fluidic liquid flow system having a 15 mm diameter may have a flow velocity of approximately 0.01 metres per second. Accordingly, the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 as described herein may be configured to be placed in a pipe of a flow system having a liquid flow rate of at least 0.1 litres per minute. The liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 as described herein may be configured to be placed in a pipe of a flow system having a liquid flow rate (or a flow rate capacity) of (or of at least) 0.1 litres per minute; 1 litre per minute; or 10 litres per minute; or 100 litres per minute; or 1000 litres per minute; or 2000 litres per minute; or 3000 litres per minute; or 5000 litres per minute.

[0264] As described herein, the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 as described herein may be particularly suitable for macro-scale liquid flow systems. The liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 as described herein may be particularly suitable for placement in pipe sizes corresponding to macro-scale liquid flow systems, for example, pipes greater than 0.5 cm in diameter; or greater than 1 cm in diameter; or greater than 1.5 cm in diameter; or greater than 2 cm in diameter. The liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 as described herein may be particularly suitable for use with (e.g., configured to be placed in) pipe diameter sizes up to 150 cm; or up to 100 cm; or up to 90 cm; or up to 80 cm; or up to 70 cm; or up to 60 cm; or up to 50 cm; or up to 40 cm; or up to 30 cm; or up to 20 cm; or up to 10 cm; or up to 5 cm; or up to 4 cm; or up to 3 cm, for example. The macro-fluidic liquid flow system may additionally or alternatively be or include (e.g., large scale) open and / or natural bodies of water, for example aqueducts, rivers, streams, etc. Further, since the liquid flow rate

[0265] I42354WOmeasurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 as described herein may be particularly suitable for macro-scale liquid flow systems, the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 as described herein may additionally or alternatively be particularly suitable for other macro-scale liquid systems where the sensor is moved through a large body of water, for example, when the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 is, e.g., formed of, placed on, or mounted on a vehicle (such as a boat) moving through a body of water (such as a lake, stream, river, ocean, etc.). Therefore, in such macro-fluidic liquid systems where the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 is moved through the system, the velocity of the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 through the liquid (e.g., water) may be the principal transport mechanism of an electroactive substance (e.g., water molecules) to the electrodes rather than diffusion (e.g., as in microfluidic environments). Accordingly, the liquid flow rate measurement apparatus 10 may measure velocity (or relative velocity) of the sensor (e.g., attached to a vehicle) moving through a body of water in a similar manner to that described herein with respect to measuring the flow rate of the liquid in flow systems. Similarly, the liquid flow rate measurement apparatus 10 may correlate the current response value as described herein (in liquid flow systems) to a liquid flow velocity in a similar manner to that described herein with respect to measuring the flow rate of the liquid in flow systems. Further, the dissolved oxygen measurement apparatus 100 may measure dissolved oxygen content of a body of water as the apparatus 100 is moved through the body of water.

[0266] As will be appreciated, the first, working, electrode 112 and the second electrode 114 may be placed in proximity to one-another, such that the first, working, electrode 112 and the second electrode 114 form a complete electrical circuit (across the liquid). As will also be appreciated, the first, working, electrode 112 and the second electrode 114 need not be directly adjacent one-another, but may instead be located a certain distance away from each other, e.g., a distance corresponding to up to a hundred times a diameter of the first, working, electrode 112 (e.g., a distance up to 10 cm), as long as the electrical circuit is complete.

[0267] In use, when a liquid flows overthe first, working, electrode 112, the apparatus is configured to obtain calibration data indicative of a correlation between a current value(s) of the apparatus and a dissolved oxygen content (e.g., concentration of dissolved oxygen) of the liquid, measure a first current response value of the apparatus, and output a dissolved oxygen content value determined from the first current response value.

[0268] In other words, in use, when a liquid flows overthe first, working, electrode 112, the apparatus may be configured to measure a first current response value of the apparatus, the current response value representative of a dissolved oxygen content in the liquid at the first electrode potential value of the

[0269] I42354WOfirst, working, electrode 112. Accordingly, the apparatus is configured to output the dissolved oxygen content of the liquid flow determined by processing the current response value. As will be appreciated, and as described in more detail herein, the current response value of the dissolved oxygen measurement apparatus 100 may be measured by an ammeter 122 electrically connected within the apparatus, e.g., connected between the first, working, electrode 112 and the second electrode 114. Therefore, the current response value of the dissolved oxygen measurement apparatus 10 may be measured between the first, working, electrode 112 and the second electrode 114. As described in more detail herein, the dissolved oxygen measurement apparatus 100 may be configured to repeat the aforementioned steps, i.e., the dissolved oxygen measurement step and / or the step of outputting the dissolved oxygen content.

[0270] As will be appreciated, in a stationary liquid system, the aforementioned determination of the dissolved oxygen content value may be obtained, in use, when liquid (e.g., stationary liquid) is in contact with the first, working, electrode 112.

[0271] Accordingly, the dissolved oxygen measurement apparatus 100 as described herein may provide advantages. In particular, as described herein, dissolved oxygen content of a liquid in a system may often be accounted for and / or mitigated in order to be able to measure a rate of reaction. On the contrary, the present dissolved oxygen measurement apparatus 100 as described herein may utilize the current response of a flow system directly in order to measure a dissolved oxygen content of a liquid.

[0272] The current response value of the dissolved oxygen measurement apparatus 100 may be measured by an ammeter 22 electrically connected within the apparatus, e.g., connected between the first, working, electrode 112 and the second electrode 114. Accordingly, the current response value of the dissolved oxygen measurement apparatus 100 may be measured between the first, working, electrode 112 and the second electrode 114. The current response value may be measured by a multimeter, for example (such as an ammeter 22 as part of a multimeter). The potential of the first, working, electrode 112, may be measured by a voltmeter 20. The potential of the first, working, electrode 112 may be measured by a multimeter, for example (such as a voltmeter 20 as part of a multimeter). The voltmeter 20 may be electrically connected to the first, working, electrode 112, and the second electrode 114. When three electrodes are present, as described in more detail herein, the ammeter 22 may be electrically connected to the first, working, electrode 112, the counter electrode 116, and / or the reference (or pseudo reference) electrode, and / or the voltmeter 20 may be electrically connected to the first, working, electrode 112, the reference (or pseudo reference) electrode, and / or the third, counter, electrode 116. The potential and / or current response value of the dissolved oxygen measurements apparatus 100 may be controlled and / or measured by a potentiostat electrically connected to the first, working, electrode 112, the second electrode 114, and the third, counter, electrode 116, if present. As will be appreciated, the ammeter 22 and / or voltmeter

[0273] I42354WO20 described herein may be embedded electronic equipment, logic controllers, controllers (e.g., controller 30), or processors that have been configured to perform this function. In particular, the ammeter 22 and / or voltmeter 20 may be embedded electronic(s) within the housing 18 of the dissolved oxygen measurements apparatus 100, for example, as part of a logic controller and / or processor.

[0274] The first, working, electrode 112 may be cylindrical in shape. The first, working, electrode may have a diameter of 0.5 to 2.0 mm. The first, working, electrode 112 may have a diameter of 0.8 to 1.2 mm. The first, working, electrode may have a diameter of 1 mm. The first, working, electrode 112 may have a length of 4 mm. The first, working, electrode 112 may have a length of 1 to 10 mm. Such an electrode size may be particularly suited for macro-fluidic flow liquid systems.

[0275] As described herein, the first, working, electrode 112 may therefore have increased longevity when compared to prior art working electrodes. In particular, as described herein, the first, working, electrode 112 may be larger than prior electrodes in prior electrochemical systems. Additionally, having a larger electrode as described herein may provide advantages. In particular, in electrode systems having smaller electrodes, a cleaning step may strip away the surface of the electrode, such that, when smaller electrodes are used, the electrode may be destroyed in a small number of working (e.g., measurement) and cleaning cycles. The dissolved oxygen measurement apparatus 100 as described herein may undergo multiple measurement and cleaning cycles without destroying the first, working, electrode 112.

[0276] The dissolved oxygen measurement apparatus 100 may be configured to set the first, working, electrode 112 to a first cleaning potential and hold the first, working, electrode 112 at the first cleaning potential for a first period of time, wherein the first cleaning potential is a positive potential. Accordingly, the dissolved oxygen measurement apparatus 100 may be configured to execute a first cleaning step. The first cleaning potential may otherwise be described herein as a preliminary cleaning potential. The first cleaning step may otherwise be described herein as a preliminary cleaning step. The first period of time may otherwise be described herein as a preliminary period of time. As will be appreciated, the preliminary cleaning step may not be executed by the dissolved oxygen measurement apparatus 100. The preliminary cleaning step may remove undesired elements, such as chlorine and / or metals on the surface of the first, working, electrode 112. The preliminary cleaning step may be executed prior to the oxygen evolution cleaning step.

[0277] The dissolved oxygen measurement apparatus 100 may be configured to set the first, working, electrode 112 to a second cleaning potential and hold the first, working, electrode 112 at the second cleaning potential for a second period of time. The second cleaning potential may be positive. The second cleaning potential may be more positive than the first cleaning potential. Accordingly, the dissolved oxygen measurement apparatus 100 may be configured to execute a second cleaning

[0278] I42354WOstep. The second cleaning potential may otherwise be described herein as an oxygen evolution cleaning potential. The second cleaning step may other be described herein as an oxygen evolution cleaning step. The second period of time may otherwise be described herein as an oxygen evolution period of time. Accordingly, as will be appreciated when the first cleaning step, i.e., the preliminary cleaning step, is not executed by the dissolved oxygen measurement apparatus 100, the second cleaning step may still be executed (for example, in the absence of the first cleaning step).

[0279] The dissolved oxygen measurement apparatus 100 may be configured to set the first, working, electrode 112 to a third cleaning potential and hold the first, working, electrode 112 at the third cleaning potential for a third period of time. The third cleaning potential may be a negative potential. Accordingly, the dissolved oxygen measurement apparatus 100 may be configured to execute a third cleaning step. The third cleaning potential may otherwise be described herein as a hydrogen evolution cleaning potential. The third cleaning step may other be described herein as an oxygen evolution cleaning step. The third period of time may otherwise be described herein as a hydrogen evolution period of time. Accordingly, as will be appreciated when the first cleaning step, i.e., the preliminary cleaning step, is not executed by the dissolved oxygen measurement apparatus 100, the third cleaning step may still be executed (for example, in the absence of the first cleaning step). Further, as described herein, since the dissolved oxygen measurement apparatus 100 may undergo multiple measurement and cleaning cycles, the dissolved oxygen measurement apparatus 100 may be considered self-cleaning.

[0280] Accordingly, the dissolved oxygen measurement apparatus 100 may be considered to be a selfcleaning dissolved oxygen measurement apparatus 100.

[0281] The dissolved oxygen measurement apparatus 100 may be configured to set the first, working, electrode 112 to a rest potential and hold the first, working, electrode 112 at the rest potential for a rest period of time. The rest step may be executed, e.g., in between, before, and / or after each cleaning step, and / or before or after the dissolved oxygen measurement step. The method may comprise multiple rest steps e.g., in between, before, and / or after each cleaning step, and / or before or after the dissolved oxygen measurement step.

[0282] The dissolved oxygen measurement apparatus 100 may comprise a controller 30. The controller 30 may be configured to execute the dissolved oxygen measurement step. The controller 30 may be configured to execute the first, second, and / or third cleaning step (which otherwise may each be described as the preliminary, oxygen evolution, and the hydrogen evolution cleaning step, respectively), and / or the rest step. The controller 30 may execute the step(s) automatically. For example, the controller 30 may execute the step(s) automatically based on a preset time configuration (e.g., a preset programme), or on the instruction of an operator, e.g., using a control programme.

[0283] I42354WOAs shown in Figures 1 and 3, the controller 30 may be electrically connected to the first, working, electrode 112 and the second electrode 114 (and, if present, as described in more detail herein, a third, counter, electrode 116). The controller 30 may be wirelessly connected to the dissolved oxygen measurement apparatus 100 for controlling the first, working, electrode 112 and the second electrode 114 (and, if present, as described in more detail herein, a third, counter, electrode 116). Accordingly, the controller 30 may hold the first, working, electrode 112 at the first electrode potential, the first cleaning potential, second cleaning potential, third cleaning potential, and / or the rest potential, and / or the controller 30 may hold the second electrode 114 at the second potential value. The controller 30 may hold the third, counter, electrode 116, if present, at a counter potential as described in more detail herein.

[0284] The dissolved oxygen measurement apparatus 100 may therefore include a dedicated controller 30 for processing the measured current response value, and for measuring the dissolved oxygen content of a liquid using the current response value of the apparatus 100. As described herein, the controller 30 may also control the setting of potential(s) of the first, working, electrode 112, the second electrode 114, and / or the third electrode 116, if present.

[0285] The dissolved oxygen measurement apparatus 100 may provide a processing device (e.g., the controller 30) to determine, from the calibration data and the measured first current response value of the apparatus 100, a dissolved oxygen content of the liquid. The dissolved oxygen measurement apparatus 100 may provide a measurement device (e.g., an ammeter 22 as described in more detail herein) to measure the current response value of the dissolved oxygen measurement apparatus 100. The dissolved oxygen measurement apparatus 100 may provide a data set including the calibration data indicative of a correlation between a current value(s) of the apparatus and a dissolved oxygen content of the liquid.

[0286] As described herein, the calibration data may be based on the first electrode potential value of the first, working, electrode 112. Additionally or alternatively, the data set may include a plurality of data sets, e.g., multiple sets of calibration data indicative of flow rate of a number of different liquids at a multiple potentials of the first, working, electrode 112. The controller 30 may select calibration data based on the liquid of the flow system. The controller 30 may select calibration data based on an input from an operator.

[0287] As described herein, the first, second, and third cleaning potentials may be applied to the liquid flow rate measurement apparatus 10. The first, second, and / or third cleaning potentials as described herein may each be described as the preliminary, oxygen evolution, and the hydrogen evolution cleaning potentials, respectively, as described herein. Therefore, as described herein in relation to the dissolved oxygen measurement apparatus 100, the liquid flow rate measurement apparatus 10

[0288] I42354WOmay be configured to set the first, working, electrode 12 to a first cleaning potential and hold the first, working, electrode 12 at the first cleaning potential for a first period of time. The first cleaning potential may be a positive potential. Accordingly, the liquid flow rate measurement apparatus 10 may be configured to execute a first cleaning step. The liquid flow rate measurement apparatus 10 may be configured to set the first, working, electrode 12 to a second cleaning potential and hold the first, working, electrode 12 at the second cleaning potential for a second period of time. The second cleaning potential may be a positive potential. The second cleaning potential may be more positive than the first cleaning potential. Accordingly, the liquid flow rate measurement apparatus 10 may be configured to execute a second cleaning step. It will be appreciated that in the absence of the first cleaning step, the second cleaning step, i.e., the oxygen evolution cleaning step, may still be executed. The liquid flow rate measurement apparatus 10 may be configured to set the first, working, electrode 12 to a third cleaning potential and hold the first, working, electrode 12 at the third cleaning potential for a third period of time, wherein the third cleaning potential is a negative potential. Accordingly, the liquid flow rate measurement apparatus 10 may be configured to execute a third cleaning step. The first, second, and / or third cleaning step as described herein may each be described as the preliminary, oxygen evolution, and the hydrogen evolution cleaning steps, respectively, as described herein. The liquid flow rate measurement apparatus 10 may additionally or alternatively be configured to set the first, working, electrode 12 to a rest potential and hold the first, working, electrode 12 at the rest potential for a rest period of time. Accordingly, when configured to implement the cleaning step(s), the liquid flow rate measurement apparatus 10 as described herein may be considered to be a self-cleaning liquid flow rate measurement apparatus 10.

[0289] The first cleaning potential may be equal to or between +0.7 volts to +1.2 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). The second cleaning potential may be equal to or greater than +1.4 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). The second cleaning potential may correspond to the third potential value as described above in relation to the liquid flow rate measurement apparatus 10. Accordingly, the second cleaning period of time (described below) may be a time as described herein in relation to the cleaning time period described above in relation to the liquid flow rate measurement apparatus 10. The third cleaning potential may be equal to or more negative than -0.9 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). The rest potential may be equal to or between +0.1 volts to +0.7 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode).

[0290] The first cleaning potential (i.e., the preliminary cleaning potential as described herein) may occupy the oxygen adsorption region for the electrode material, which may be equal to or between +0.7 volts to +1.2 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode) for a platinum electrode. The second cleaning potential (i.e., the oxygen evolution cleaning potential as described herein) may occupy the oxygen evolution (e.g., the

[0291] I42354WOhydrogen reduction) region for the electrode material, which may be equal to or greater than +1.4 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode) for a platinum electrode. The third cleaning potential (i.e., the hydrogen evolution cleaning potential as described herein) may occupy the hydrogen evolution region for the electrode material, which may be equal to or more negative than -0.9 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). The rest potential may be the region of minimal current on the electrode material, which for platinum may be equal to or between +0.1 volts to +0.7 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode).

[0292] As will be appreciated, and as described herein, the potentials may be considered to be in relation to a difference from the potential of a reference electrode (e.g., a silver / silver-chloride electrode). It will be appreciated that different electrode potentials may be provided suitable for each electrode material.

[0293] Accordingly, as described herein, the dissolved oxygen measurement apparatus 100 (and / or the liquid flow rate measurement apparatus 10) may undergo a series of potential (i.e., voltage) cycles to clean the first, working, electrode 12, 112. In particular, a positive potential step (e.g., the first cleaning step as described above) may clean the electrode by removing the adsorbed species, for example, when the first, working, electrode 12 is a platinum electrode, causing platinum oxide to form without oxygen evolution. As described above, a potential between +0.7 volts and +1.2 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode) may be used at the first, working, electrode 12, 112.

[0294] The second cleaning step as described above may employ a larger magnitude, positive potential to induce oxygen evolution, which may cause any limescale on the electrode to dissolve into the local solution. The applied potential of the first, working, electrode 12, 112 may be more positive than +1.4 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode).

[0295] The third cleaning step as described above may be a negative potential to induce hydrogen evolution. The applied potential of the first, working, electrode 12, 112 may be more negative than -0.9 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode).

[0296] The rest step may provide a potential for resting the first, working, electrode 12, 112. Accordingly, the first, working, electrode 12, 112, when a rest step is executed, may be prevented from ‘swinging’ between voltage extremes, continuously, which may increase the life of the first, working, electrode 12, 112.

[0297] I42354WOIt will be appreciated that the applied voltage(s) may be varied based on the electrode material of the first, working, electrode 12, 112. In particular, as will be appreciated, the potential values of the first, working, electrode 12, 112 may be altered based on the material of the first, working, electrode, and / or the material of the reference electrode, if present (e.g., the second electrode 14, 114). For example, the reference electrode material may provide a potential offset away from the reference potential provided by a standard hydrogen electrode. As an example, when a platinum first, working, electrode 12, 112 is used, and a silver / silver chloride reference electrode (e.g., the second electrode 14, 114) is used, the potential of the first, working, electrode at the second cleaning step (i.e., the oxygen evolution cleaning step) may be desired to be +1.4 volts from the reference electrode potential value, since the silver / silver chloride reference electrode potential may be offset +0.2 volts from the standard hydrogen electrode potential value. Therefore, in the hypothetical scenario where a platinum first, working, electrode 12, 112 is used and a standard hydrogen electrode is used as the second electrode 14, 114, the desired potential of the first, working, electrode 12, 112 may be greater than +1.6 volts during the second cleaning step as described above (e.g., the potential value not being offset from the +0.2 volt offset of the silver / silver-chloride electrode).

[0298] Accordingly, as described above, the potential of the first, working, electrode 12, 112 for the first cleaning step, for a platinum first, working, electrode 12, 112, may be between +0.9 and +1.4 volts from a reference value of a standard hydrogen electrode. The second cleaning potential may be equal to or greater than +1.6 volts from a reference value of a standard hydrogen electrode. The third cleaning potential may be equal to or more negative than -0.7 volts from a reference value of a standard hydrogen electrode. The rest potential may be equal to or between +0.3 volts to +0.9 volts from a reference value of a standard hydrogen electrode.

[0299] Such an offset required by the offset of the reference electrode material compared to a standard hydrogen electrode may be described as an offset “from standard”. Accordingly, the potential of the first, working, electrode 12, 112 may be offset accounting for the material of the reference electrode. For example, the offset of the potential of the first, working, electrode 12, 112 away from the values in relation to the standard hydrogen electrode may account for the offset of the potential of the reference electrode material from the standard hydrogen electrode, e.g., a saturated calomel electrode may be offset by +0.24 volts (e.g., +0.242 volts) from standard (which may result in a potential value for, e.g., the first cleaning step of +0.66 to +1.16 volts), a mercury / mercury sulphate reference electrode may be offset by +0.64 volts from standard (which, as an example, may result in a potential value for the first cleaning step of +0.26 to +0.96 volts), and a mercury / mercury oxide reference electrode may be offset by +0.099 volts from standard (which, as an example, may result in a potential value for the first cleaning step of +0.081 to +1.31 volts).

[0300] The first cleaning period of time (preliminary period of time) may be equal to or between 1 and 10 seconds (or 1 to 5 seconds; or 1 to 20 seconds, e.g., 5 seconds, 10 seconds, 15 seconds, or 20

[0301] I42354WOseconds). The second cleaning period of time (oxygen evolution period of time) may be equal to or between 1 and 10 seconds (or 1 to 5 seconds; or 1 to 20 seconds, e.g., 5 seconds, 10 seconds, 15 seconds, or 20 seconds). The third cleaning period of time (hydrogen evolution period of time) may be equal to or between 1 and 10 seconds (or 1 to 5 seconds; or 1 to 20 seconds, e.g., 5 seconds, 10 seconds, 15 seconds, or 20 seconds). The rest period of time may be equal to or up to 90 seconds. The rest period of time maybe up to, equal to, or greater than one day, e.g., the rest period of time may be indefinite.

[0302] The relationship between the current response value and the dissolved oxygen content of the liquid (e.g., a current-dissolved oxygen content relationship) may vary based on the (specific) liquid in the liquid flow system 2. Accordingly, the dissolved oxygen measurement apparatus 100 may include a database of current-dissolved oxygen content relationship(s) (e.g., calibration data) corresponding to various liquids.

[0303] The current-dissolved oxygen content relationship for the or each liquid may be empirically derived. In particular, the step of obtaining, using the calibration data, a dissolved oxygen content determined from the first current response value may comprise correlating the first current response value with dissolved oxygen content using an empirically derived calibration curve representative of dissolved oxygen content versus current response value. The current-dissolved oxygen content relationship may be represented by an equation, e.g., a quadratic equation. The current-dissolved oxygen content relationship may be represented by a second order polynomial, a third order polynomial, or fourth order polynomial, a fifth order polynomial. Accordingly, the order of polynomial may be 2, 3, 4, 5, 6, 7, 8, 9, or 10, for example. The relationship may also be exponential or logarithmic in form, or be approximated through the use of a neural network or other generalisable mathematical model, or a combination of the aforementioned methods. As described herein, the current-dissolved oxygen relationship may take into account concentrations of electroactive substances in the liquid, predictable responses of electroactive species against flow, and / or wherein other components of the solution are predictable and possible to control against, for example.

[0304] The dissolved oxygen measurement apparatus 100 may further include a third, counter, electrode 116 (e.g., configured to be placed into the liquid flow system 2) electrically connected to the first, working, electrode 112 and the second electrode 114, the third, counter, electrode 116 configured to be held at a counter potential value. The counter potential value may correspond to an inverse value of the potential value of the first, working electrode 12, e.g., the first electrode potential value (e.g., an inverse value of the potential at which the first, working, electrode 12 is held). For example, if the first, working, electrode is held at a first electrode potential value of -0.5 volts, the counter potential may therefore be +0.5 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode).

[0305] I42354WOAs described herein in relation to the liquid flow rate measurement apparatus 10, the third, counter, electrode 116, if present, may be a steel electrode. The third, counter, electrode 116, if present, may be a steel coated electrode. The third, counter, electrode 116 may be cylindrical. The third, counter, electrode 116 may be a polygonal, e.g., rectangular, prism. The dissolved oxygen measurement apparatus 100 may have a housing, e.g., housing 118 as described in more detail herein. The third, counter, electrode 116 may form part of the housing, e.g., the third, counter, electrode 116 may extend from the housing 118. In other words, when the dissolved oxygen measurement apparatus 100 is described as an electrochemical sensor, the third, counter, electrode 116 may form part of a body of the sensor. As shown in Figure 8, the third, counter, electrode 116 may be formed of an annular cylindrical shape, e.g., the third, counter, electrode 116 having an annular thickness, and hollow space within, where the first, working, electrode 112 and / or the second electrode 114 may be located (and / or electronics may be located).

[0306] The third, counter, electrode 116 may be any metallic or conductive material, such as copper, steel, magnesium, zinc, and / or graphene, for example.

[0307] The third, counter, electrode 116 may have a diameter of up to 12 mm. The third, counter, electrode 116 may have a diameter of up to 20 mm. The third, counter, electrode 116 may have a diameter of up to 30 mm. The third, counter, electrode may have a diameter of up to and including 100 times diameter of the first, working, electrode 112. The third, counter, electrode 116 may have a diameter of up to and including 10; 20; 30; 40; 50; 60; 70; 80; 90; or 100 times diameter of the first, working, electrode 112.

[0308] As will be appreciated, the first, working, electrode 112, and / or the second electrode 114, and / or the third, counter, electrode 116 may be placed in proximity to one-another, such that the first, working, electrode 112, the second electrode 114, and the third, counter, electrode 116 form a complete electrical circuit (across the liquid). As will be appreciated, the first, working, electrode 112, the second electrode 114, and the third, counter, electrode 116 may form a complete electrical circuit across the liquid. Additionally, the first, working, electrode 112, the second electrode 114, and / or the third electrode 116 may be placed in close proximity to one-another, e.g., adjacent or close-to-adjacent to one-another (e.g., up to 5cm). Such close proximity may improve the electrical connection between the first, working, electrode 112, the second electrode 114, and / or the third electrode 116. As will also be appreciated, the first, working, electrode 112, the second electrode 114, and / or the third electrode 116 need not be directly adjacent one-another, but may instead be located a certain distance away from each other, e.g., up to one-hundred times the distance corresponding to a diameter of the first, working, electrode 112 (e.g., up to 10 cm), as long as the electrical circuit is complete.

[0309] I42354WOWhen a third, counter, electrode 116 is provided, the second electrode 114 may solely act as a reference (or pseudo-reference) electrode. Accordingly, wear on the second electrode 114 may be reduced. In particular, when two electrodes are present, the second electrode 114 may act as both a counter electrode and a reference (or pseudo reference) electrode. Accordingly, fouling and / or unwanted coating (e.g., unwanted deposition of a material) on the surface of the electrode may occur at the second electrode 114 at a slower rate if three electrodes are present in the liquid flow rate measurement apparatus 100. Accordingly, providing a dissolved oxygen measurement apparatus 100 including three electrodes may increase the longevity of the dissolved oxygen measurement apparatus 100.

[0310] When a third, counter, electrode 116 is provided, the second electrode 114 of the dissolved oxygen measurement apparatus 100 may be a reference (or pseudo-reference) electrode.

[0311] The dissolved oxygen measurement apparatus 100 may be configured to automatically set the electrode potential of the first, working, electrode 112 to the first electrode potential.

[0312] The dissolved oxygen measurement apparatus 100 may be configured to automatically set the electrode potential of the first, working, electrode 112 to the first, second, and / or third cleaning potential(s), if present. As described herein, the first, second, and third cleaning potentials may each be described as the preliminary, oxygen evolution, and the hydrogen evolution cleaning potentials, respectively, as described herein.

[0313] The dissolved oxygen measurement apparatus 100 may be configured to automatically set the electrode potential of the first, working, electrode 112 to the rest potential. The dissolved oxygen measurement apparatus 100 may be configured to automatically measure the current response value. The dissolved oxygen measurement apparatus 100 may be configured to automatically output the dissolved oxygen content of the liquid. The automatic processing as described herein may be based on a predetermined programme. The automatic processing may be executed by the controller 30. As described herein, the dissolved oxygen measurement apparatus 100 may be configured to repeat the aforementioned steps. The dissolved oxygen measurement apparatus 100 may be configured to repeat the aforementioned steps a plurality of times. As described herein, the dissolved oxygen measurement apparatus 100 may be configured to execute (and / or repeat) the aforementioned steps automatically (e.g., using a processor and / or controller 30 configured to execute instructions).

[0314] As shown in Figures 2,4, and 8, the dissolved oxygen measurement apparatus 100 may include a housing 118 for housing electronics, e.g., a potentiostat, voltmeter 20, ammeter 30, controller 30 etc. The electronics may be embedded electronics. Accordingly, the dissolved oxygen measurement apparatus 100 may be configured as a single unit. The dissolved oxygen measurement apparatus

[0315] I42354WO100 may be modularly installable into the flow system 2. For example, the dissolved oxygen measurement apparatus 100 may be readily removable from the liquid flow system 2 and reinstallable elsewhere, where required.

[0316] As shown in Figures 5 and 6, there is also provided a method of operating a liquid flow rate measurement apparatus 10.

[0317] The liquid flow rate measurement apparatus 10 when described in reference to the method may comprise any of, any combination of, or all of the features and / or advantages of the liquid flow rate measurement apparatus 10 as described herein. The liquid flow rate measurement apparatus 10 used in the method may be configured to automatically execute one of, some of, or all of the steps (e.g., measurement steps, cleaning steps, resting steps) as described in more detail in relation to the method of operating a liquid flow rate measurement apparatus 10 as described in more detail herein. Accordingly, the method described herein may be executed and / or repeated automatically (e.g., by the controller 30, if present).

[0318] In particular, the liquid flow rate measurement apparatus 10 comprises: a first, working, electrode 12 configured to be placed in a liquid flow system 2; and a second electrode 14 configured to be placed in the liquid flow system 2 and electrically connected to the first, working, electrode 12; wherein: the first, working, electrode 12 is configured to be held at a measurement electrode potential value, and the second electrode 14 is configured to provide a counter potential value such that the liquid flow rate measurement apparatus 10 has a system potential. As described herein, the liquid flow system 2 may be a macro-fluidic liquid flow system (e.g., as described herein). Accordingly, the method may include placing the liquid flow rate measurement apparatus 10 into the macro-fluidic liquid flow system. The first, working, electrode 12 may be configured to be placed in the macro-fluidic liquid flow system. The second electrode 14 may be configured to be placed in the macro-fluidic liquid flow system.

[0319] As shown in Figure 5, the method comprises flowing a liquid over a first, working, electrode 12. The method comprises a measurement step (shown generally at 1100 in Figures 5 and 6), including, as shown at box 1002, holding the first, working, electrode 12 at the measurement potential value for a first time period (box 1004) and, after the first time period, measuring a first current response value of the apparatus (box 1006). Accordingly, at each step, e.g., the measurement step, the potential may therefore be held for a period of time to allow for non-faradaic current to decrease to almost zero, such that liquid flow rate measurement apparatus 10 measures the steady state current response. As described herein, the current response value of the liquid flow rate measurement apparatus 10 may be measured between the first, working, electrode 12 and the second electrode 14.

[0320] I42354WOThe first time period (e.g., the measurement time period) may be up to 10 seconds, e.g., 1 second, 3 seconds, 5 seconds, 7 seconds, 9 seconds, 10 seconds, or any value therebetween. The first time period may additionally or alternatively be described as including a holding, or settling time period. The first time period may be 1 to 5 seconds. The first time period may be up to 90 seconds. In particular, the first time period may be 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds, 80 seconds, or 90 seconds. The measurement potential value may be considered equivalent to the first electrode potential value as described herein in relation to the liquid flow rate measurement apparatus 10. As will be appreciated, as described herein, the measurement taken after the first time period may be taken within its own time period; the measurement taken after the first time period may betaken either immediately afterthe measurement time period, or during a subsequent time period, such as the flow rate measurement step as described in more detail below. The time period during which the measurement is taken may be considered to be a flow rate measurement step time period and may correspond to the second time period as described above in relation to the liquid flow rate measurement apparatus 10. The flow rate measurement step time period time period may be 1 to 5 seconds. The flow rate measurement step time period may be 0.5 seconds. The flow rate measurement step time period time period may be indefinite, e.g., for continuous measurement.

[0321] As shown in Figures 5 and 6, the method comprises a flow rate determination step (shown generally at 1102 in Figures 5 and 6), comprising, as shown in box 1008, obtaining calibration data indicative of a correlation between a current value(s) of the apparatus and a flow rate(s) of the liquid, obtaining a flow rate value determined from the first current response value (box 1010), and outputting the flow rate of the liquid (box 1012).

[0322] In other words, the method may include comparing the current value to a current-flow rate correlation data, the current-flow rate correlation data (e.g., calibration data) providing a liquid flow rate of liquid through the liquid flow system 2 corresponding to the current value at the measurement potential value of the first, working, electrode 12 in the liquid being flowed through the flow system 2. Accordingly, in this way, the method may determine the liquid flow rate of the liquid flow system 2.

[0323] As shown in Figure 6, the method may include repeating the measurement step(s) and the flow rate determination step(s). Additionally or alternatively, the method may include a cleaning step or steps (e.g., the cleaning steps corresponding to the method of cleaning a liquid flow rate measurement apparatus 10 as described herein) after determining the flow rate of the liquid. As will be appreciated, the cleaning step(s) as described herein may be executed prior to any measurement and / or flow rate determination step. Accordingly, the method may include repeating the cleaning step(s) as described herein.

[0324] I42354WOAdditionally or alternatively, the method may include, after the cleaning step, remeasuring the current response value of the system. As will be appreciated, the method may include repeating the measurement and flow rate determination steps without carrying out a cleaning step. When remeasuring the current response value of the system, the measurement potential may be changed or may be equivalent to the prior measurement step, such that subsequent repeats use the same and / or different measurement potentials of the first, working, electrode. Accordingly, the method may include utilizing multiple sets of calibration data to output a flow rate or flow rates.

[0325] The measurement potential of the first, working, electrode 12 may be a negative potential. The measurement potential of the first, working, electrode 12 may be between -0.9 volts and -1.8 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode).

[0326] As described herein, the measurement potential may be sufficient to induce hydrogen evolution on the surface of the first, working, electrode 12. The current response of the liquid flow rate measurement apparatus 10 may increase as a greater volume of fluid passes over the first, working, electrode 12; higher current may therefore indicate higher flow rate. It will be appreciated that there may be a non-zero current at zero flow. Additionally, it will be appreciated that a linear increase in flow rate of the liquid may not result in a linear increase in the current response value.

[0327] As shown in Figure 6, the method may further comprise a resting step (indicated generally at boxes 1014 and 1016). The resting step may comprise holding the first, working, electrode 12 at a resting potential value (box 1014) for a resting time period (box 1016). The resting step is shown generally in Figure 6 after the output of the liquid flow rate value; however, it will be appreciated that the resting step may be executed before or after any of the other step(s) of operating the liquid flow rate measurement apparatus 10 described herein. The resting potential value may be a positive potential. The resting step may provide a time-buffer between the ‘swinging’ of the potential of the first, working, electrode 12, such that the longevity (i.e., lifespan) of the first, working, electrode 12 may be increased.

[0328] The resting potential value may be between +0.1 volts and +0.7 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). The resting time period may be up to or including 20 seconds, e.g., 5 seconds, 10 seconds, 15 seconds, or 20 seconds. The resting time period may be indefinite. The resting time period may be up to 24 hours. The resting time period may be greater than 24 hours. The resting potential value may therefore be a positive potential below the threshold at which oxygen evolution is induced on the surface of the first, working, electrode 12. Accordingly, the resting potential may provide a rest period in which no reaction occurs at the surface of the first, working, electrode 12.

[0329] I42354WOAs shown in Figure 6, the method may further include a cleaning step. The cleaning step may comprise holding the first, working, electrode 12 at a cleaning electrode potential for a cleaning time period. The cleaning electrode potential may be a positive potential (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). The cleaning potential may be a potential greater than the resting potential value, if present. The cleaning potential value may be sufficient to induce oxygen evolution at the surface of the first, working, electrode 12. Accordingly, the cleaning electrode potential may be equal to or greater than +1.4 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). The cleaning electrode potential may be up to or equal to +2 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). As described herein, the cleaning step may include any, any combination, or all of the cleaning steps as described herein in relation to the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100, e.g., the cleaning step may include the first, second, and / or third cleaning steps (i.e., the preliminary, oxygen evolution, and / or hydrogen evolution cleaning steps). The cleaning step is generally shown in Figure 6 after the output of the liquid flow rate step (and after the rest step); however, it will be appreciated that that the cleaning step(s) may be executed before or after any of the other step(s) of operating the liquid flow rate measurement apparatus 10 described herein.

[0330] As shown in Figure 6, the method may include the rest step without the cleaning step, or the cleaning step without the rest step.

[0331] Accordingly, the method may include setting the first, working, electrode 12 to a rest potential (box 1014) and holding the first, working, electrode 12 at the rest potential for a rest time period (box 1016) after the liquid flow rate has been determined. Additionally or alternatively, the method may include setting the first, working, electrode 12 to a rest potential (box 1014) and holding the first, working, electrode 12 at the rest potential for a rest time period (box 1016) after the first, working, electrode 12 has undergone a cleaning step (boxes 1018 and 1020) (not shown). The method may include a rest step after the measurement and flow rate determination steps and / or the cleaning step(s) absent a further step of repeating the steps, e.g., the measurement step(s), required to obtain the current response value of the liquid flow rate measurement apparatus 10 (e.g., the current response value across the first, working, electrode 12 and the second electrode 14). Additionally or alternatively, after the cleaning step (boxes 1018 and 1020), if the current response value is to be remeasured, the method may include the rest step(s) after cleaning, and before the process of remeasuring (i.e., before setting the first, working, electrode 12 to the measurement potential value).

[0332] The method may comprise the following steps, in order:

[0333] a) the measurement step;

[0334] b) the flow rate determination step;

[0335] c) the resting step; and

[0336] I42354WOd) the cleaning step.

[0337] The potential value of the first, working, electrode 12 at the flow rate determination step may be the same potential value as the cleaning step. In other words, the flow rate determination step may also be performed as part of the cleaning step (due to the similarity of the potential value). Accordingly, as described above, the method may comprise the following steps, in order, (a); (b) & (d) together; and (c).

[0338] The method may comprise additional cleaning and / or rest step(s) as described herein before the measurement step. The rest step may be applied before and / or after any of the other steps. The resting step(s) may be performed more or less than once in a measurement cycle, e.g., in relation to every one measurement step.

[0339] The method may comprise the following steps, in order:

[0340] c) the resting step;

[0341] a) the measurement step; and

[0342] d) the cleaning step; and

[0343] b) the flow rate determination step.

[0344] Performing the method as mentioned above may prevent the voltage change from any cleaning step to the measurement step from interfering with the measured current value of the first, working, electrode 12. In particular, performing a rest step before the measurement step may provide a buffer of time for the voltage of the first, working, electrode 12 to stabilise.

[0345] The method may comprise the following steps, in order:

[0346] d) the cleaning step.

[0347] c) the resting step;

[0348] a) the measurement step; and

[0349] b) the flow rate determination step.

[0350] Steps (a) to (d) may be repeated at least once. As described above, the cleaning step (d) may comprise more than one cleaning step. In particular, the cleaning step (d) as described herein may comprise the cleaning steps as described in relation to the method of cleaning a liquid flow rate measurement apparatus 10 and / or a dissolved oxygen measurement apparatus 100 as described herein.

[0351] The steps as described herein may represent a full measurement, cleaning, and rest cycle of the liquid flow rate measurement apparatus 10. Accordingly, the liquid flow rate measurement apparatus 10 may periodically take current value measurements, whilst avoiding buildup of coating(s) on the

[0352] I42354WOsurface of the first, working, electrode 12, which may increase the lifespan of the liquid flow rate measurement apparatus 10.

[0353] As described herein, the method steps may be executed automatically by the liquid flow rate measurement apparatus 10. In particular, (a) the measurement step; and / or (b) the flow rate determination step; and / or (c) the resting step, if present; and / or (d) the cleaning step, if present, may be executed automatically by the liquid flow rate measurement apparatus 10. The automatic execution may be executed by the processor (and / or controller 30), if present, as described herein. The automatic execution may be initiated by a user, e.g., remotely.

[0354] As shown in Figure 7, there is also provided a method of cleaning a liquid flow rate measurement apparatus 10 and / or a dissolved oxygen measurement apparatus 100. The liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 used in the method may be configured to automatically execute one of, some of, or all of the steps (e.g., steps, resting steps) as described in more detail in relation to the method of cleaning a liquid flow rate measurement apparatus 10 and / or a dissolved oxygen measurement apparatus 100 as described in more detail herein. Accordingly, the method described herein may be executed automatically. In particular, as described herein, the processor (and / or controller 30), if present, may be configured to execute the method steps automatically.

[0355] The liquid flow rate measurement apparatus 10 of the method may have any of, any combination of, or all of the features and / or advantages of the liquid flow rate measurement apparatus 10 as described herein.

[0356] The dissolved oxygen measurement apparatus 100 of the method may have any of, any combination of, or all of the features and / or advantages of the dissolved oxygen measurement apparatus 100 as described herein.

[0357] The liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 may comprise a first, working, electrode 12, 112 configured to be placed in a liquid flow system 2; a second electrode 14, 114 configured to be placed in the liquid flow system 2 (e.g., in proximity to the first, working, electrode 12, 112) and electrically connected to the first, working, electrode 12, 112. The first, working, electrode 12, 112 may be configured to be held at a first electrode potential value, and the second electrode 14, 114 may be configured to provide a second potential value such that the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 has a system potential.

[0358] As shown in boxes 2002 and 2004 of Figure 7, the method may comprise (a) a first cleaning step, comprising holding the first, working, electrode 12, 112 at a first cleaning potential for a first cleaning

[0359] I42354WOperiod of time. The first cleaning potential may be positive potential (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). A positive potential step (e.g., the first cleaning step as described above) may clean the, e.g., platinum, electrode by removing the adsorbed species, e.g., causing platinum oxide to form without oxygen evolution. As will be appreciated, whilst box2000 of Figure 7 represents a step of placing the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 into a flow system 2, the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 may already be located within a flow system 2, e.g., installed into a pipe or flow pathway. The first cleaning potential may otherwise be described herein as a preliminary cleaning potential. The first cleaning step may other be described herein as a preliminary cleaning step and the first cleaning period of time may be considered to be a preliminary cleaning period of time. As will be appreciated, the preliminary cleaning step may not be executed by the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100.

[0360] As shown in boxes 2006 and 2008 of Figure 7, the method comprises (b) a second cleaning step, comprising holding the first, working, electrode 12, 112 at a second cleaning potential for a second cleaning period of time. The second cleaning potential may be a positive potential (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). The second cleaning potential may be more positive than the first cleaning potential. The second cleaning step as described above may employ a larger magnitude, positive potential to induce oxygen evolution, which may cause any limescale on the electrode to dissolve into the local solution. The second cleaning potential may otherwise be described herein as an oxygen evolution cleaning potential and the second cleaning period of time may be considered to be an oxygen evolution cleaning period of time. The second cleaning step may other be described herein as an oxygen evolution cleaning step. Accordingly, as will be appreciated when the first cleaning step, i.e., the preliminary cleaning step, is not executed by the dissolved oxygen measurement apparatus 100, the second cleaning step may still be executed (for example, in the absence of the first cleaning step). As will be appreciated, when the first cleaning step is not performed, the second cleaning step may be considered to comprise holding the first, working, electrode 12, 112 at a second cleaning potential for a first period of time (e.g., since the first period of time in respect of the preliminary cleaning potential will not be present).

[0361] As shown in boxes 2010 and 2012 of Figure 7, the method comprises (c) a third cleaning step, comprising holding the first, working, electrode 12, 112 a third cleaning potential for a third cleaning period of time. The third cleaning potential may be a negative potential (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). The third cleaning step as described above may be a negative potential to induce hydrogen evolution. The third cleaning potential may otherwise be described herein as a hydrogen evolution cleaning potential and the third cleaning period of time may be considered to be a hydrogen evolution cleaning period of

[0362] I42354WOtime. The third cleaning step may other be described herein as an hydrogen evolution cleaning step. Accordingly, as will be appreciated when the first cleaning step, i.e., the preliminary cleaning step, is not executed by the dissolved oxygen measurement apparatus 100, the third cleaning step may still be executed (for example, in the absence of the first cleaning step).

[0363] The first cleaning period of time (e.g., the preliminary cleaning period of time) may be 1 to 10 seconds (or 1 to 5 seconds; or 1 to 20 seconds, e.g., 5 seconds, 10 seconds, 15 seconds, or 20 seconds). The second cleaning period of time (e.g., the oxygen evolution cleaning period of time) may be 1 to 10 seconds (or 1 to 5 seconds; or 1 to 20 seconds, e.g., 5 seconds, 10 seconds, 15 seconds, or 20 seconds). The third cleaning period of time (e.g., the hydrogen evolution cleaning period of time) may be 1 to 10 seconds (or 1 to 5 seconds; or 1 to 20 seconds, e.g., 5 seconds, 10 seconds, 15 seconds, or 20 seconds).

[0364] The method may further include (d) a rest step. As described herein, the rest step may reduce wear of the first, working, electrode 12, 112 over its lifespan, such that the lifespan of the first, working, electrode 12, 112 may be increased. The rest step may be executed between any of the cleaning steps (and / or after, and / or before, the cleaning steps).

[0365] The rest step may comprise holding the first, working, electrode 12, 112 at a rest potential for a resting period of time.

[0366] The resting period of time may be up to or equal to 90 seconds. The resting period of time may be up to or equal to 86400 seconds, i.e., up to one day.

[0367] The rest potential may be a less positive potential (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode) than the first cleaning potential. Accordingly, the resting potential may be a potential insufficient to induce oxygen evolution at the first, working, electrode 12, 112. Accordingly, during the rest step, there may be no reaction at the surface of the first, working, electrode 12, 112.

[0368] The method of cleaning the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 may further comprise measurement step(s), such that the method of cleaning may be considered to be a method of cleaning and operating the liquid flow rate measurement apparatus and / or the dissolved oxygen measurement apparatus as described herein.

[0369] The method may further comprise (e) a dissolved oxygen measurement step. Accordingly, after the cleaning steps, the dissolved oxygen measurement apparatus 100 may measure the content of dissolved oxygen within the liquid.

[0370] I42354WOThe dissolved oxygen measurement step may comprise holding the first, working, electrode 12, 112 at a dissolved oxygen measurement potential for a dissolved oxygen measurement period of time.

[0371] The measurement potential may be less negative than the third cleaning potential. At the dissolved oxygen measurement step, a sufficiently negative potential, e.g., between -0.4 V and -0.8 V, may be applied and held (e.g., for a dissolved oxygen measurement period of time) to allow for the non-faradaic current to decrease to almost zero. The sensor may then measure the steady state current response, which can be used to measure the concentration of dissolved oxygen in the liquid.

[0372] The dissolved oxygen measuring step may comprise measuring the current response value of the apparatus, correlating the current response value of the apparatus and outputting the dissolved oxygen content determined by processing the current response value. The dissolved oxygen measuring step may comprise obtaining calibration data indicative of a correlation between a current value(s) of the apparatus and a dissolved oxygen content of the liquid; obtaining, using the calibration data, a dissolved oxygen content value determined from the current response value, and outputting the dissolved oxygen content of the liquid. As described herein, compensation steps may be implemented into the determination of the dissolved oxygen concentration of the liquid, e.g., compensation for flow, and / or known concentrations of liquid content may be included in the calibration data.

[0373] The method may further, additionally or alternatively, comprise (f) a flow rate measurement step.

[0374] The flow rate measurement step may comprise holding the first, working, electrode 12, 112 at a flow rate measurement potential value for a flow rate measurement period of time; and measuring a current response value of the apparatus. The flow rate measurement step may comprise obtaining calibration data indicative of a correlation between a current value(s) of the apparatus and a flow rate(s) of the liquid; obtaining, using the calibration data, a flow rate value determined from the current response value, and outputting the flow rate of the liquid. As described herein, compensation steps may be implemented into the determination of the flow rate of the liquid, e.g., known concentrations of liquid content may be included in the calibration data.

[0375] The flow rate measurement step may correspond to the step including the second time period as described above in relation to the liquid flow rate measurement apparatus 10. The flow rate measurement period of time may be 1 to 10 seconds. The flow rate measurement step time period time period may be 1 to 5 seconds. The flow rate measurement period of time may be 0.5 seconds. The flow rate measurement period of time may be any time as described herein in relation to the second time period in relation to the liquid flow rate measurement apparatus 10 as described herein. The flow rate measurement period of time may be indefinite, e.g., for continuous measurement. The

[0376] I42354WOflow rate measurement period of time may be adjusted or reconfigured during use of the liquid flow rate measurement apparatus 10.

[0377] The flow rate measurement potential may be a negative potential (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode).

[0378] The flow rate measurement potential and the third cleaning potential may be equivalent. Accordingly, the flow rate measurement step may be performed during the third cleaning step.

[0379] The first cleaning potential may be equal to or between +0.7 volts and +1.2 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). At such a voltage, adsorbed species on the surface of the first, working, electrode 12, 112 may be removed. Additionally or alternatively, when a platinum first, working, electrode 12, 112 is used, platinum oxide may form on the surface of the first, working, electrode 12, 112.

[0380] The second cleaning potential may be equal to or more positive than +1.4 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). Such a potential may induce oxygen evolution at the surface of the first, working, electrode 12, 112, which may cause limescale on the electrode to dissolve into the local solution.

[0381] The third cleaning potential may be equal to or more negative than -0.9 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). Such a potential may induce hydrogen evolution at the surface of the first, working, electrode 12, 112.

[0382] The rest potential, if present, may be equal to or between +0.1 volts and +0.7 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode). The rest (and / or resting) potential as described herein, if present, may alternatively be equal to or between +0.1 volts and +0.8 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode); accordingly, in some instances, an overlap between the rest potential and the first cleaning potential may be at least partially permitted.

[0383] The dissolved oxygen measurement potential, if present, may be equal to or between -0.4 volts and -0.8 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode).

[0384] The flow rate measurement potential, if present, may be equal to or between -0.9 volts and -1.8 volts (e.g., from a reference electrode potential value, such as a silver / silver-chloride reference electrode).

[0385] I42354WOAs described above, the potential(s) as described above may be potential(s) as a difference from a reference electrode value, and the potentials) may vary (e.g., be offset by a specific amount) based on the material of the first, working, electrode 12, 112, and / or the second electrode 14, 114 (e.g., the material of the reference electrode).

[0386] The method may be executed in the following order:

[0387] (a) the first cleaning step (the preliminary cleaning step);

[0388] (b) the second cleaning step (the oxygen evolution cleaning step);

[0389] (c) the third cleaning step (the hydrogen evolution cleaning step);

[0390] (d) the rest step, if present; and

[0391] (e) the dissolved oxygen measurement step, if present, and / or (f) the flow rate measurement step, if present.

[0392] Multiple rest steps may be used in the method as described herein, e.g., a rest step may be provided before, after, and / or between any of steps (a), (b), (c), (e), and / or (f) as described herein. It will be appreciated if the first cleaning step (a), e.g., the preliminary cleaning step is not executed, the method may be executed in the order (b), (c), (d), and (e) and / or (f) as described above.

[0393] The flow rate measurement potential may be equivalent to the third cleaning potential, i.e., the hydrogen evolution cleaning potential.

[0394] Accordingly, the method may include cleaning the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 and also include measuring the flow rate of the liquid and / or the dissolved oxygen concentration of the liquid.

[0395] It will be appreciated that the order of steps may be varied. In particular, the cleaning steps as described above may be executed in the following order:

[0396] (a) the first cleaning step; (c) the third cleaning step; (b) the second cleaning step; or (b) the second cleaning step; (c) the third cleaning step; (a) the first cleaning step; or (b) the second cleaning step; (a) the first cleaning step; (c) the third cleaning step; or (c) the third cleaning step; (b) the second cleaning step; (a) the first cleaning step; or (c) the third cleaning step; (a) the first cleaning step; (b) the second cleaning step.

[0397] Additionally, if present, steps (e) and (f) may be executed in another order, e.g., step (f) and then step (e).

[0398] The rest step (d) or additional rest steps as described herein may be executed between any of steps (a) to (f). Additional rest steps may increase the lifespan of the first, working, electrode 12, 112.

[0399] I42354WOAs will be appreciated, the method(s) as described herein may further include a compensation step(s). In particular, the method(s) may include post processing of raw data (e.g., current data) obtained by the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100, e.g., when correlating the current response value with the flow rate and / or dissolved oxygen content. The compensation step(s) may be executed, e.g., executed automatically, by the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100 (e.g., executed automatically by the controller 30). The postprocessing of raw data may occur prior to obtaining, using the calibration data, the flow rate value and / or the dissolved oxygen content value. Such concentrations, responses, or predictions as described herein used during compensation step(s) may be known or may be known or may be measured and combined with the measured current response from the apparatus, to remove their respective impact on the output of the liquid flow rate measurement step and / orthe dissolved oxygen measurement step. Accordingly, known or measured values relating to a known concentration of an electroactive substance, and / or where the response of the electroactive species may be predictable against flow and / or dissolved oxygen content of a liquid, and / or other components of the solution that are predictable and possible to control against, may be included in a calculation as part of the liquid flow rate measurement step and / orthe dissolved oxygen measurement step. The values, responses, and / or calculations may be included in the current-liquid flow rate relationship and / or the current-dissolved oxygen relationship as described in more detail herein.

[0400] The outputs of the compensation step(s) may be in the form of an equation, e.g., an Arrhenius (or similar) equation, and / or an exponential equation (e.g., in the form of ex).

[0401] Non-limiting examples of compensation steps are described as follows:

[0402] Temperature compensation (liquid flow rate measurement apparatus 10 and / or dissolved oxygen measurement apparatus 100):

[0403] a. A temperature reading may be taken by a separate sensor close enough in time and proximity to the liquid flow rate measurement apparatus 10 and / or dissolved oxygen measurement apparatus 100 that the reading can be assumed to be the temperature of the fluid at the point of the electrochemical reading.

[0404] b. The temperature may be used in an equation (e.g., by the controller 30, if present) to remove the temperature effects.

[0405] c. The equation may be empirically derived and may be similar in form to an Arrhenius Equation.

[0406] Flow compensation (dissolved oxygen measurement apparatus 100):

[0407] a. When the dissolved oxygen measurement is taken, it may be compensated against flow. A reading can be taken either using the electrochemical flow method described herein

[0408] I42354WOor using a separate sensor, provided the measurement is representative of the flow conditions experienced by the first, working, electrode 12, 112 at the time of the reading. Indeed, as described herein, the liquid flow rate measurement apparatus 10 and dissolved oxygen measurement apparatus 100 may share equivalent features. Accordingly, the dissolved oxygen measurement apparatus may be suitable for measuring flow as described herein in relation to the liquid flow rate measurement apparatus 10.

[0409] b. As with the other compensations, the controller 30 may use empirical equations to remove the dependency.

[0410] Conductivity and / or pH ((liquid flow rate measurement apparatus 10 and / or dissolved oxygen measurement apparatus 100):

[0411] a. Similar to temperature compensation, a reading may be taken and processed through an equation to remove the dependency.

[0412] b. The equation may be empirically derived.

[0413] The compensation steps related to temperature, flow, conductivity, and / or pH may be performed individually or may be combined, e.g., compensation steps relating to temperature and flow may be performed and the results combined to account for temperature and flow effects on the measurement output of the dissolved oxygen measurement apparatus 100. Certain compensation steps may not be required for certain liquids. For example, drinking (potable) water may not undergo significant changes in pH and / or conductivity, and therefore such parameters may not be accounted for.

[0414] The compensation step(s) as described herein may be implemented in the flow rate determination step and / or the dissolved oxygen concentration step as described herein. The compensation steps may include inputting the measured and / or known results into a database, e.g., into the calibration data.

[0415] As described herein, any of the method steps described herein may be performed (e.g., performed automatically) by the liquid flow rate measurement apparatus 10 and / or the dissolved oxygen measurement apparatus 100.

[0416] When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

[0417] The invention may also broadly consist in the parts, elements, steps, examples and / or features referred to or indicated in the specification individually or collectively in any and all combinations of two or more said parts, elements, steps, examples and / or features. In particular, one or more

[0418] I42354WOfeatures in any of the embodiments described herein may be combined with one or more features from any other embodiment(s) described herein.

[0419] Protection may be sought for any features disclosed in any one or more published documents referenced herein in combination with the present disclosure.

[0420] Although certain example embodiments of the invention have been described, the scope of the appended claims is not intended to be limited solely to these embodiments. The claims are to be construed literally, purposively, and / or to encompass equivalents.

[0421] I42354WO

Claims

56CLAIMS1. A liquid flow rate measurement apparatus, comprising:a first, working, electrode configured to be placed in a liquid flow system; and a second electrode configured to be placed in the liquid flow system and electrically connected to the first, working, electrode,the liquid flow rate measurement apparatus configured to hold the first, working, electrode at a first electrode potential value, andthe second electrode configured to provide a second potential value such that the liquid flow rate measurement apparatus has a system potential:wherein, in use, when a liquid flows over the first, working, electrode, the apparatus is configured to execute a flow rate measurement step, comprising:obtaining calibration data indicative of a correlation between a current value(s) of the apparatus and a flow rate(s) of the liquid, measuring a first current response value of the apparatus, and obtaining, using the calibration data, a flow rate value determined from the first current response value, andwherein the apparatus is configured to output the flow rate determined by processing the current response value.

2. The liquid flow rate measurement apparatus according to claim 1 for use in a macro-fluidic liquid flow system, wherein the first, working, electrode is configured to be placed in the macro-fluidic liquid flow system, and wherein the second electrode is configured to be placed in the macro-fluidic liquid flow system.

3. The liquid flow rate measurement apparatus of claim 1 or 2, further comprising a controller configured to execute the flow rate measurement step.

4. The liquid flow rate measurement apparatus according to any preceding claim, wherein the apparatus is further configured execute a cleaning step, comprising holding the first, working, electrode at a third potential value, wherein the third potential value is a positive potential and is optionally greater than +1 .4 volts.I42354WO575. The liquid flow rate measurement apparatus according to claim 4, wherein the apparatus is configured, after determining the flow rate determined by processing the current response value, to hold the first, working, electrode at the third potential value for a cleaning time period.

6. The liquid flow rate measurement apparatus according to claim 5, wherein the apparatus is further configured to hold the first, working, electrode at a fourth potential value for a second cleaning time period, wherein the fourth potential value is a negative potential value and is optionally equal to or more negative than -0.9 volts.

7. The liquid flow rate measurement apparatus according to any preceding claim, further comprising a third, counter, electrode electrically connected to the first, working, electrode and the second electrode and configured to be held at a counter potential value.

8. The liquid flow rate measurement apparatus according to any preceding claim, wherein the liquid flow rate measurement apparatus is configured to automatically set the electrode potential of the first, working, electrode, measure the current response value, and / or output the flow rate based on a predetermined programme.

9. The liquid flow rate measurement apparatus according to any preceding claim, wherein the apparatus is configured to execute the following steps in order:hold the first, working, electrode at the first electrode potential value for a first time period;after the first time period, during a second time period, measure a current response value of the apparatus;obtain calibration data indicative of a correlation between a current value(s) of the apparatus and a flow rate(s) of the liquid, compare the current response value to the calibration data, the calibration data providing a liquid flow rate of the liquid corresponding to the current response value at the first electrode potential value of the first, working, electrode, andoutput the flow rate determined by processing the current response value.

10. The liquid flow rate measurement apparatus according to any preceding claim, wherein the liquid flow rate measurement apparatus is configured to transmit the first current response value and / or flow rate to a remote server.

11. The liquid flow rate measurement apparatus according to any preceding claim, wherein the apparatus is configured to output the first current response value and / or flow rate to a readable medium.I42354WO5812. The liquid flow rate measurement apparatus according to any preceding claim, wherein the step of obtaining, using the calibration data, a flow rate value determined from the first current response value comprises correlating the first current response value with the liquid flow rate using an empirically derived calibration curve representative of liquid flow rate versus current response value.

13. The liquid flow rate measurement apparatus according to any preceding claim, wherein the working electrode is cylindrical in shape and has a diameter of 0.8 to 1.2 mm.

14. The liquid flow rate measurement apparatus according to any preceding claim, wherein the first, working, electrode is a platinum electrode.

15. The liquid flow rate measurement apparatus according to any preceding claim, wherein the second electrode is a silver / silver-chloride electrode.

16. The liquid flow rate measurement apparatus according to any preceding claim, wherein the second electrode is a silver electrode.

17. The liquid flow rate measurement apparatus according to any preceding claim, wherein the first electrode potential value is between -0.5 volts to -1.5 volts.

18. The liquid flow rate measurement apparatus according to any preceding claim, wherein, when the apparatus has output the flow rate determined by processing the current response value, the apparatus is configured to repeat the flow rate measurement step and wherein the apparatus is configured to output the flow rate determined by processing the current response value obtained by the repeated flow rate measurement step.

19. A dissolved oxygen measurement apparatus, comprising:a first, working, electrode configured to be placed in a liquid flow system; and a second electrode configured to be placed in the liquid flow system and electrically connected to the first, working, electrode,the dissolved oxygen measurement apparatus configured to hold the first, working, electrode at a first electrode potential value, andthe second electrode is configured to provide a second potential value such that the dissolved oxygen measurement apparatus has a system potential,wherein, in use, when a liquid flows over the first, working, electrode, the apparatus is configured to execute a dissolved oxygen measurement step, comprising:I42354WO59obtaining calibration data indicative of a correlation between a current value(s) of the apparatus and a dissolved oxygen content of the liquid, measuring a first current response value of the apparatus, and obtaining, using the calibration data, a dissolved oxygen content value determined from the first current response value, and wherein the apparatus is configured to output the dissolved oxygen content of the liquid flow determined by processing the current response value,and optionally wherein the dissolved oxygen measurement apparatus is configured for use in a macro-fluidic liquid flow system, wherein the first, working, electrode is configured to be placed in the macro-fluidic liquid flow system, and wherein the second electrode is configured to be placed in the macro-fluidic liquid flow system.

20. The dissolved oxygen measurement apparatus according to claim 19, wherein the apparatus is further configured to execute:an oxygen evolution cleaning step, comprising setting the first, working, electrode to an oxygen evolution cleaning potential, holding the first, working, electrode at the oxygen evolution cleaning potential for an oxygen evolution period of time, wherein the oxygen evolution cleaning potential is a positive potential; anda hydrogen evolution cleaning step, comprising setting the first, working, electrode to a hydrogen evolution cleaning potential, holding the first, working, electrode at the hydrogen evolution cleaning potential for an oxygen evolution period of time, wherein the hydrogen evolution cleaning potential is a negative potential.

21. The dissolved oxygen measurement apparatus according to claim 20, wherein the apparatus is further configured to execute:a preliminary cleaning step prior to the oxygen evolution potential cleaning step, comprising setting the first, working, electrode to a preliminary cleaning potential, holding the first, working, electrode at the preliminary cleaning potential for a preliminary period of time, wherein the preliminary cleaning potential is a positive potential, and wherein the oxygen evolution positive cleaning potential is more positive than the preliminary cleaning potential.

22. The dissolved oxygen measurement apparatus according to claim 19, 20, or 21 , wherein the apparatus is configured to execute:a rest step, comprising setting the first, working, electrode to a rest potential, holding the first, working, electrode at the rest potential for a rest period of time.

23. The dissolved oxygen measurement apparatus of any of claims 19 to 22, further comprising a controller configured to execute:the dissolved oxygen measurement step; and / orthe preliminary cleaning step, if present; and / orI42354WO60the oxygen evolution cleaning step, if present; and / orthe hydrogen evolution cleaning step, if present; and / orthe rest step, if present.

24. The dissolved oxygen measurement apparatus according to any of claims 19 to 23, wherein the first, working, electrode is cylindrical in shape and has a diameter of 0.8 to 1.2 mm.

25. The dissolved oxygen measurement apparatus according to any of claims 20 to 24, wherein:the preliminary cleaning potential is equal to or between +0.7 volts to +1.2 volts; and / orthe oxygen evolution cleaning potential is equal to or greater than +1 .4 volts; and / or the hydrogen evolution cleaning potential is equal to or more negative than -0.9 volts; and / orthe rest potential is equal to or between +0.1 volts to +0.7 volts.

26. The dissolved oxygen measurement apparatus according to any of claims 19 to 25, further comprising a third, counter, electrode electrically connected to the first, working, electrode and the second electrode, the third, counter, electrode configured to be held at a counter potential value.

27. The dissolved oxygen measurement apparatus according to any of claims 19 to 26, wherein the dissolved oxygen measurement apparatus is configured to automatically:set the electrode potential of the first, working, electrode to the first electrode potential; and / orset the electrode potential of the first, working, electrode to the preliminary, oxygen evolution , and / or hydrogen evolution cleaning potential(s), if present; and / orset the electrode potential of the first, working, electrode to the rest potential, if present;measure the current response value; and / oroutput the dissolved oxygen content of the liquid,based on a predetermined programme.

28. A method of operating a liquid flow rate measurement apparatus, the liquid flow rate measurement apparatus comprising:a first, working, electrode configured to be placed in a liquid flow system; and a second electrode configured to be placed in the liquid flow system and electrically connected to the first, working, electrode; wherein:the first, working, electrode is configured to be held at a measurement electrode potential value, andI42354WOthe second electrode is configured to provide a counter potential value such that the liquid flow rate measurement apparatus has a system potential,the method comprising:flowing a liquid over the first, working, electrode;a measurement step, comprising:holding the first, working, electrode at the measurement potential value for a first time period;after the first time period, measuring a first current response value of the apparatus;a flow rate determination step, comprising:obtaining calibration data indicative of a correlation between a current value(s) of the apparatus and a flow rate(s) of the liquid,obtaining, using the calibration data, a flow rate value determined from the first current response value, andoutputting the flow rate of the liquid.

29. The method according to claim 28, wherein the first, working, electrode is configured to be placed in a macro-fluidic liquid flow system, and wherein the second electrode is configured to be placed in the macro-fluidic liquid flow system.

30. The method according to claim 28 or 29, wherein the measurement potential of the first, working, electrode is a negative potential.

31. The method according to claim 30, wherein the measurement potential of the first, working, electrode is between -0.9 volts and -1.8 volts.

32. The method according to any of claims 29 to 31 , further comprising a resting step, the resting step comprising:holding the first, working, electrode at a resting potential value for a resting time period, wherein the resting potential value is a positive potential.

33. The method according to claim 32, wherein the resting potential value is between +0.1 volts and +0.7 volts.

34. The method according to any of claim 28 to 33, further comprising a cleaning step, wherein the cleaning step comprises:holding the first, working, electrode at a cleaning electrode potential for a cleaning time period, wherein the cleaning electrode potential is a positive potential and optionally is a potential greater than the resting potential value, if present.I42354WO35. The method according to claim 34, wherein the cleaning electrode potential is equal to or greater than +1.4 volts.

36. The method according to any of claims 34 or 35 when dependent on claim 32 or 33, wherein the method comprises the following steps, in order:a) the measurement step;b) the flow rate determination step;c) the resting step; andd) the cleaning step.

37. The method according to claim 36, wherein steps (a) to (d) are repeated at least once.

38. The method according to any of claims 34 to 37, wherein the method further comprises a second cleaning step, wherein the second cleaning step comprises:holding the first, working, electrode at a second cleaning electrode potential for a second cleaning time period, wherein the second cleaning electrode potential is a negative potential.

39. The method according to claim 38, wherein the second cleaning electrode potential is equal to or more negative than -0.9 volts.

40. The method according to any of claims 28 to 39, wherein:a) the measurement step; and / orb) the flow rate determination step; and / orc) the resting step, if present; and / ord) the cleaning step, if present,is executed automatically by the liquid flow rate measurement apparatus.

41. A method of cleaning a liquid flow rate measurement apparatus and / or a dissolved oxygen measurement apparatus, the liquid flow rate measurement apparatus and / or the dissolved oxygen measurement apparatus comprising:a first, working, electrode configured to be placed in a liquid flow system;a second electrode configured to be placed in the liquid flow system and electrically connected to the first, working, electrode;wherein the first, working, electrode is configured to be held at a first electrode potential value, andI42354WO63wherein the second electrode is configured to provide a second potential value such that the liquid flow rate measurement apparatus and / or the dissolved oxygen measurement apparatus has a system potential,the method comprising:(a) an oxygen evolution cleaning step, comprising:holding the first, working, electrode at an oxygen evolution potential for an oxygen evolution period of time, wherein the oxygen evolution cleaning potential is positive;(b) a hydrogen evolution cleaning step, comprisingholding the first, working, electrode at a hydrogen evolution cleaning potential for a hydrogen evolution period of time, wherein the hydrogen evolution cleaning potential is a negative potential.

42. The method according to claim 41 , further comprising:a preliminary cleaning step, comprising:holding the first, working, electrode at a preliminary cleaning potential for a preliminary period of time, wherein the preliminary cleaning potential is a positive potential, and wherein the oxygen evolution potential is more positive than the preliminary cleaning potential.

43. The method according to claim 41 or 42, further comprising:(d) a rest step, comprising:holding the first, working, electrode at a rest potential for a resting period of time, wherein the rest potential is less positive than the first cleaning potential.

44. The method according to claim 41 , 42, or 43, further comprising:(e) a dissolved oxygen measurement step, comprising:holding the first, working, electrode at a dissolved oxygen measurement potential for a dissolved oxygen measurement period of time, wherein the measurement potential is less negative than the third cleaning potential;obtaining calibration data indicative of a correlation between a current value(s) of the apparatus and a dissolved oxygen content of the liquid;obtaining, using the calibration data, a dissolved oxygen content value determined from the current response value, andoutputting the dissolved oxygen content of the liquid.

45. The method according to claim 41 , 42, 43, or 44, further comprising:(f) a flow rate measurement step, comprising:I42354WO64holding the first, working, electrode at a flow rate measurement potential value for a flow rate measurement period of time, wherein the flow rate measurement potential is a negative potential;measuring a current response value of the apparatus;obtaining calibration data indicative of a correlation between a current value(s) of the apparatus and a flow rate(s) of the liquid;obtaining, using the calibration data, a flow rate value determined from the current response value, andoutputting the flow rate of the liquid.

46. The method according to claim 45, wherein the flow rate measurement potential and the hydrogen evolution cleaning potential are equivalent, and wherein the flow rate measurement step is executed during the hydrogen evolution cleaning step.

47. The method according to any of claims 41 to 46, wherein:the preliminary cleaning potential, if present, is equal to or between +0.7 volts and +1 .2 volts; and / orthe oxygen evolution cleaning potential is equal to or more positive than +1.4 volts; and / orthe hydrogen cleaning potential is equal to or more negative than -0.9 volts; and / or the rest potential, if present, is equal to or between +0.1 volts and +0.7 volts; and / or the dissolved oxygen measurement potential, if present, is equal to or between -0.4 volts and -0.8 volts; and / orthe flow rate measurement potential, if present, is equal to or between -0.9 volts and -1.8 volts.

48. The method according to any of claims 41 to 47, wherein the method is executed in the following order:(a) the preliminary cleaning step, if present;(b) the oxygen evolution cleaning step;(c) the hydrogen evolution cleaning step;(d) the rest step, if present; and(e) the dissolved oxygen measurement step, if present, and / or(f) the flow rate measurement step, if present.I42354WO

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