System and method for measuring at least one characteristic of water from a wastewater network.

Abstract

A method for measuring at least one parameter of water from a wastewater network, in which a sensor (1) comprising staggered electrode pairs is implemented, and, in a measurement phase, a local electric current Ii and a local voltage Vi are measured for each pair of electrodes of the sensor, and the local electric currents are corrected by removing a current measurement offset value Z to produce corrected local electric currents, and corrected local conductances Coi are calculated using the corrected local electric currents, and local conductivities EC25i are calculated using the products of the local conductances Coi by cell constants Ki and using a temperature measurement T of said water to correct for an effect of temperature on the local conductances,and in which process a relative height Hr (measurement) of water is determined and an overall conductivity EC 25 of said water is calculated by a function having at least one parameter which is the determined relative height Hr (measurement) of said water. The process is implemented in a system. Figure for the abstract: Fig. 7,

Description

Title of the invention: System and method for measuring at least one characteristic of water from a sanitation network. Scope of the invention

[0001] The invention relates to a system and method for measuring at least one characteristic of water in a wastewater network by calculating the conductivity of said water and a level (or height) of said water in order to allow, in particular, the detection of the presence of extraneous water and possibly its quantification, the detection of the presence of sediments and possibly their quantification, and the calculation of the flow rate of said water. It has applications in the field of wastewater network monitoring and extraneous water detection. State of the art

[0002] The present invention relates to the field of wastewater management in sewer systems. These systems are subject to a significant problem: the presence of extraneous water in addition to (or instead of) wastewater. Indeed, sewer systems are normally designed for wastewater management and to allow for its specific treatment. In general, extraneous water is water that is not polluted and therefore does not require treatment; it is also called extraneous clear water. This extraneous water can be of natural origin (spring catchment, groundwater drainage, ditches, network or pumping station flooding, etc.) or artificial origin (fountains, building drainage, cooling water, heat pump discharge, air conditioning discharge, etc.).They have the disadvantage of diluting wastewater effluents, reducing the available transport capacity in sanitation networks, and saturating wastewater treatment plants.

[0003] This extraneous water, most often of rainwater origin, can also infiltrate and enter sewer systems through leaks or infrastructure defects. This infiltration of extraneous water increases the volume of wastewater to be treated at treatment plants, sometimes significantly. However, sewer systems are designed for a specific number of inhabitants in a defined geographical area, and extraneous water can lead to an overload of the treatment and collection capacities of the sewer systems. Furthermore, the water flowing through the systems can also carry solid matter that can form deposits, further reducing the capacity of the networks.

[0004] A rational, ecological, and economical solution would be to significantly limit or even completely eliminate extraneous water from sewage systems. Similarly, It would be preferable to prevent solid materials from entering the networks, for example by implementing upstream settling tanks.

[0005] However, field studies to detect these extraneous waters remain to this day lengthy, costly, and difficult to implement. Methods to prevent solid matter from entering the sewer system represent an additional cost and require monitoring.

[0006] It is therefore particularly interesting to develop easy-to-use tools that allow for the simple and efficient detection and quantification of extraneous water in the different parts of the sanitation network in order to identify the sources and then to be able to effectively eliminate them.

[0007] The same applies to deposits of solid matter or sediment that accumulate on the bare bottom of the sewer network. The bare bottom corresponds to the ground or bottom of the sewer network that is free of deposits or sediment.

[0008] Within the framework of the present invention, means are proposed for detecting, identifying / categorizing and quantifying the different waters that may circulate in a sanitation network and in particular extraneous waters and sediments by means of water conductivity measurements.

[0009] Indeed, since extraneous water often originates from rainwater, its ion content and therefore its conductivity are very low, typically less than 30 pS / cm. Wastewater, on the other hand, has high or even very high conductivities, generally 1 mS / cm and up to 10 mS / cm for some industrial wastewater.

[0010] Monitoring the evolution of water conductivity can therefore make it possible to detect the presence and determine the proportion of extraneous water at a given time.

[0011] However, this does not allow us to know the quantity of extraneous water in absolute value. It is therefore also useful to be able to measure the overall water flow rate at the point of analysis.

[0012] The proposed solution for this, measuring water height / level, differs from known methods using ultrasonic radar sensors, Doppler probes, or pressure sensors for determining water level and flow rate. Furthermore, these known methods do not allow for differentiation between various types of water, including extraneous water.

[0013] In the following, the term "water" or "waters" alone, without specifying the type of water, refers to any type of water that may be encountered within a wastewater network. The water in a wastewater network may, for example, contain wastewater and / or extraneous water.

[0014] A method for measuring at least one characteristic of a liquid solution is known from document FR2 701 566. Summary of the invention

[0015] The solution proposed by the invention relates to a method for measuring at least one parameter of water from a wastewater network, in which a sensor is used, intended to be placed in contact with said water and having electrodes on its surface, including a reference electrode and a determined number N greater than one of excitation electrodes, the reference electrode being elongated vertically and the excitation electrodes being spaced equidistant from each other and aligned vertically parallel to the reference electrode, each excitation electrode defining with the reference electrode a pair of electrodes, and, in a measurement phase, a local electric current 11 flowing and a local applied voltage V t are measured for each pair of electrodes of the sensor, and the local electric currents are corrected by removing a current measurement offset value Z to produce corrected local electric currents,and we calculate corrected local conductances Co i using corrected local electric currents, and we calculate local conductivities EC 25i using the products of the local conductances Co i by cell constants K, and using a temperature measurement T of said water to correct for an effect of temperature on the local conductances, and wherein we determine a relative height Hr (measurement j) of water using the local conductivities EC 25t, and wherein we calculate a global conductivity EC 25 of said water by a function having at least one parameter which is the determined relative height Hr (measurement) of said water.

[0016] In the context of the invention, the term "current" is understood to mean an electric current corresponding to an electric intensity, the unit of which is the Ampere. Similarly, the term "voltage" is understood to mean an electric voltage corresponding to a voltage, the unit of which is the Volt.

[0017] Still within the scope of the invention, the qualifier "local" refers to an element concerning a given excitation electrode or a given pair of electrodes among the pairs of electrodes of the sensor.

[0018] Other advantageous features of the process according to the invention, taken individually or in all technically possible combinations, are as follows:

[0019] - said at least one measured parameter is the overall conductivity;

[0020] - each pair of electrodes (and the corresponding excitation electrode) is referenced by a determined index i, the index i being a positive integer between 0 and AM, the pair of electrodes with index i = 0 being the lowest pair of electrodes of the sensor and the pair of electrodes with index N - 1 being the highest pair of electrodes of the sensor and the index increments by 1 from one pair of electrodes to the next, moving upwards along the height of the sensor,

[0021] - during the measurement phase, the local conductivity EC 25i of a pair is calculated electrodes before moving to the next pair of electrodes, going back up along the sensor;

[0022] - the corrected local conductance Co i is calculated by correcting the electric current local / 1 measured by subtracting a current measurement offset value Z, i.e. Co , = ( /

[0023] - the local conductivities are calculated by EC 25i = * Ki with Co , = ( / — Z) / 1 + ((TT - 25) * v) Vi

[0024]

[0025] where v is a coefficient of variation of the electrical conductance of water as a function of temperature, preferably v = 0.02; - we calculate the local conductivities by EC 25i = Coi * Ki with Co , = (1,- i+((T=-25)*0.02)

[0026]

[0027]

[0028]

[0029] z) / v / ; - the local conductivity EC 25i is calculated directly from the local electric current 11 and the local voltage V, measured without going through an intermediate calculation of a conductance, - A raw local conductivity ECi is calculated by multiplying a corrected local conductance Ci by a cell constant Ki of the corresponding electrode pair i, i.e., ECi = Ci * Ki, where the corrected local conductance Ci is calculated by correcting the local electric current I1 by a current measurement offset value Z, i.e., Ct = (It - Z) / V - we calculate the local conductivity EC 25i by correcting the raw local conductivity EC i for the effects of the water temperature T by a calculation bringing the local conductivity back to a determined reference temperature, the determined reference temperature preferably being 25 °C; - In the case of a determined reference temperature of 25°C, the local conductivity EC 25i is calculated by EC 25i = cos φ or by EC 25i = (ri - z) * v * K 1 + ((T° - 25) * v) 1 + ((T° - 25) * v)

[0030]

[0031] or by EC 25i = where v is a coefficient of variation of the conductance 1 + ((T° - 25) * p) electrical conductivity of water as a function of temperature, preferably v = 0.02; - the water in the sanitation network contains extraneous water; - a sensor is implemented which includes means for measuring the current electrical current flowing through the electrode pairs;

[0032] - a sensor is implemented which includes means for measuring the voltage applied between the electrodes of the electrode pairs;

[0033] - the measurement of the corrected local conductance is carried out at constant current or, of preferably, at constant voltage;

[0034] - the current measurement offset value Z is determined during a phase calibration;

[0035] - the current measurement offset value Z is a common Z value for all the pairs of electrodes;

[0036] - the current measurement offset value Z is the measured electric current while no excitation electrode is connected to the current measurement means measuring the electric current;

[0037] - the current measurement offset value Z is the measured electric current then that the sensor is out of water and dry;

[0038] - the current measurement offset value Z is the average of the currents local electrical 11 measured on all electrode pairs while the sensor is out of water and dry;

[0039] - the water temperature T° is measured and the local conductivity is calculated corrected for the effects of water temperature by adjusting the calculated local conductivity to a determined reference temperature, the determined reference temperature being 25 °C, the calculation formula correcting the temperature being:

[0040] EC 25i = 1 + ((1^-25) *0.02)

[0041] with: EC 25i the local conductivity at 25°C in S / cm for the pair of electrodes of index i, Co i the corrected local conductance for the pair of electrodes of index i, K t the cell constant of the pair of electrodes of index i, T° the temperature measured in °C of the water;

[0042] - during the measurement of the local electric current 11 and the local voltage V t, one applies to the pair of electrodes a periodic alternating voltage of determined excitation frequency, said alternating voltage being in the form of squares comprising plateaus of successive voltages of opposite signs;

[0043] - the periodic alternating voltage is generated by an H-bridge;

[0044] - the periodic alternating voltage comprises successive voltage plateaus of opposite signs and of the same absolute value;

[0045] - the local electric current 11 and the local voltage V t are measured during the plateau;

[0046] - the periodic alternating voltage comprises successive voltage plateaus of opposite signs, of the same absolute value and of the same duration of each plateau so that the periodic alternating voltage has a crest factor equal to 1;

[0047] - during the measurement phase, the determined excitation frequency is chosen from a set of measurement frequencies as a function of an expected or assumed or previously calculated water conductivity (local or global as the case may be);

[0048] - the measurement frequency set comprises three frequencies which are 500 Hz, 1000 Hz and 5000 Hz;

[0049] - a specific excitation frequency of 500 Hz is implemented for a local conductivity to be measured less than or equal to 1999 pS / cm, 1,000 Hz for a local conductivity to be measured between 2000 pS / cm and 9999 pS / cm, 5,000 Hz for a local conductivity to be measured greater than or equal to 10,000 pS / cm;

[0050] - a specific excitation frequency of 500 Hz is implemented for a overall conductivity to be measured less than or equal to 1999 pS / cm, of 1,000 Hz for an overall conductivity to be measured between 2000 pS / cm and 9999 pS / cm, of 5,000 Hz for an overall conductivity to be measured greater than or equal to 10,000 pS / cm;

[0051] - if, following a first measurement, a first calculation of local conductivity EC 25i gives a value which does not correspond to the conductivities predicted for the excitation frequency used in said first measurement, then the measurement is repeated with an excitation frequency adapted to the conductivity obtained in said first measurement;

[0052] - if, following a first measurement, a first calculation of overall conductivity EC 25 gives a value which does not correspond to the conductivities predicted for the excitation frequency used in said first measurement, then the measurement is repeated with an excitation frequency adapted to the conductivity obtained in said first measurement;

[0053] - in a calibration phase, the following are determined for a given frequency: cell constants K, ;

[0054] - in a calibration phase, for each frequency of the set measurement frequencies, cell constants K t;

[0055] - in the measurement phase, the cell constants Kt corresponding to the determined excitation frequency used;

[0056] - in a calibration phase, a measurement offset value Z is determined current for each frequency in the set of measurement frequencies;

[0057] - a detection of pairs of electrodes that are emerged, i.e., out of water, is implemented. a pair of electrodes being emerged if the local conductivity EC 25i for said pair of electrodes is zero, i.e. 0 pS / cm and the pair or pairs of electrodes located above said pair of electrodes has or have local conductivities of zero;

[0058] - in the measurement phase, the measurements and calculations of the conductivities are carried out local pair of electrodes after pair of electrodes starting with the lowest pair of electrodes of the sensor and moving up from one pair of electrodes to the next along the height of the sensor;

[0059] - during the measurement phase, measurements and calculations of conductivities are stopped local when a determined number of successive electrode pairs have zero local conductivities, said determined number being two or more than two;

[0060] - a detection of faulty electrode pairs is implemented, a pair electrodes being faulty if the local conductivity EC 25i for said pair of electrodes is zero while it is overcome by at least one pair of electrodes with non-zero local conductivity, and the number m of faulty electrode pairs is determined;

[0061] - a detection of faulty electrode pairs is implemented and the fault is corrected the calculation of the relative height Hr (measurementj to take into account the presence of one or more pairs of faulty electrodes;

[0062] - during the measurement phase, measurements are stopped when a predetermined number of pairs of faulty electrodes was detected, said determined number preferably being an integer multiple of two or more, preferably two;

[0063] - the relative height Hr (measurementj = Hj of water is calculated by:

[0064] H j = (EC mean * H max / EC mca)

[0065] with:

[0066] EC max the highest local conductivity EC 25i among the local conductivities EC 25i of all the electrode pairs of the sensor and

[0067] EC means the average conductivity measured over all electrode pairs of the sensor, i.e. the sum of the local conductivities EC 25i divided by the total number of electrode pairs of the sensor, and

[0068] H max the maximum relative height of water measurable by the sensor;

[0069] - the maximum relative water height measurable by the sensor, H max, is the product of the number N of excitation electrodes by e which is the spacing step between two successive excitation electrodes along the height of the sensor, i.e. H max = N * e;

[0070] - for calculating the relative height Hr (measurement) = H; the conductivities are used EC 25i local;

[0071] - the relative height Hr (measurement j = Ho 2 of water is calculated by:

[0072] Ho 1 = (EC mean * H max / EC max) + H corr

[0073] with:

[0074] EC max the highest local conductivity EC 25i among the local conductivities EC 25i of all the electrode pairs of the sensor and

[0075] EC means the average conductivity measured over all electrode pairs of the sensor during the measurement phase, i.e., the sum of the local conductivities EC 25i divided by the total number of electrode pairs of the sensor, and

[0076] H max the maximum relative height of water measurable by the sensor, and

[0077] H corr a height correction value calculated by H corr = e * m where m is the number of faulty electrode pairs and where e is the spacing step between two successive excitation electrodes along the height of the sensor, i.e. of indices i and i+1, the pair of electrodes of index i+1 being above that of index i;

[0078] - for calculating the relative height Hr (measurement j = Ho i, we use the conductivities EC 25i local;

[0079] - the relative height Hr (measurement) = H2 of water is calculated by:

[0080] H 2 = (1 tast * e) + ax3 + bx2 + ex + d

[0081] with:

[0083] with

[0084] a, b, c, d predetermined constants,

[0085] e the spacing between two successive excitation electrodes along the height of the sensor, i.e. of indices i and i+1, the pair of electrodes of index i+1 being above that of index i,

[0086] EC last the local conductivity EC 25i of the last pair of electrodes upwards still in contact with the water, i.e. the pair of electrodes with the highest non-zero local conductivity,

[0087] 1 tast is the index of the last pair of electrodes upwards still in contact with water, the lowest pair of electrodes of the sensor having an index equal to zero;

[0088] - in the case of calculating the relative height Hr (measurementj = H 2, the constants are advantageously the following: 114 < a < 115, -217 < b < -216, 151 < c < 152 and -31 < d < -30;

[0089] - for the calculation of the relative height Hr (measurement) = H 2, the conductivities are used EC 25i local;

[0090] - the spacing step e between two successive excitation electrodes along the height of the sensor is measured between the centers of two successive excitation electrodes, i.e. of indices i and i+1;

[0091] - the spacing step e between two successive excitation electrodes along the The height of the sensor is constant over the entire height of the sensor;

[0092] - the relative water height is calculated by Hr (measurementj = Hm by Hr (measurementj = Ho i or by Hr (measurement) = H2 as a function of a result of logical tests where

[0093] if ( (1 last < 2) or ( (1 last <SEU1E capteud et ( (si la paire d’électrodes d’indice 1 last est non défaillante et si la paire d’électrodes d’indice 1 last -1 est défaillante) ou (si la paire d’électrodes d’indice 1 tast - 1 est non défaillante et si la paire d’électrodes d’indice 1 tast - 2 is failing) ) ) ) then the relative water height is calculated with Hr (measurement) = H} or, preferably, with Hr (measurementj = Ho i,

[0094] otherwise the relative water height is calculated with Hr (measurementj = H 2,

[0095] 1 lastly the index of the last pair of electrodes upwards still in contact with the water, the lowest pair of electrodes of the sensor having an index equal to zero, and

[0096] The sensor THRESHOLD is a parameter that is a function of the number N of excitation electrodes of the sensor;

[0097] - the sensor THRESHOLD parameter is equal to 3 / 4 * N;

[0098] - water is present on a bare bottom of the sewer network and a absolute height Ha (measurement) of water in the sanitation network per Ha (measurement) = Hr (measurement) + H offset aVCC.

[0099] H ojfset the height between the bare bottom of the sewer network and the bottom of the excitation electrode of the lowest electrode pair of the sensor, i.e. the electrode pair with index i = 0;

[0100] - we calculate the overall conductivity EC j^par EC 25 = ECmean (Hmax) with

[0101] ECmean (Hmax) EC mean H max / Hr (measurement)

[0102] where:

[0103] EC mean is the average conductivity measured over all electrode pairs of the sensor during the measurement phase, i.e., the sum of the local conductivities EC 25i divided by the total number of electrode pairs of the sensor, and

[0104] Hr (measurement) is the relative water height, and

[0105] H max is the maximum relative height of water measurable by the sensor;

[0106] - in a calibration phase, a curve of evolution is determined with the sensor of the average conductivity measured on all pairs of electrodes as a function of a relative actual water height measured by a measuring device, said device being separate from the sensor and being in particular a radar, and a straight line fitted to said curve is determined and from said straight line a value Dk of average conductivity offset is determined, said value Dk being the average conductivity at zero relative actual water height on the straight line fitted to the curve, and

[0107] wherein, in the measurement phase, the calculation of the overall conductivity EC 25 is corrected with the value Dk of the average conductivity shift by:

[0108] EC 22 ECmean (Hmax) Dk + (EC mean - DE) H max / Hr (measurement),

[0109] - the radar is a device independent of the system and is used for calibration;

[0110] - the sensor does not include radar;

[0111] - the system does not include radar;

[0112] - the actual relative water height is measured by a height measuring device which is a radar;

[0113] - the radar is an ultrasonic radar;

[0114] - for the calculation of the overall conductivity EC 25 = ECmean (Hmax) we use the local conductivities EC 25i;

[0115] - the overall conductivity EC is calculated using EC 25 = EC water with EC water = EC / oc Or

[0116] EC max is the highest local conductivity among the local conductivities of all the electrode pairs of the sensor and

[0117] oc, which is a correlation coefficient that is a function of the relative height Hr (measurement) of water and has a value between 0 and 1, oc being calculated by: [01 18] OC — Cl 7 1 ni / ? i Hr (measurement)) + C ] Hr (measurement) + 1 EH (measurement) + £ 1 EH (measurement) + f 1

[0119] with

[0120] ai,bi, ci, di,ei and f i which are predetermined constants;

[0121] - in the case of calculating the overall conductivity EC 25 = EC water, the constants are advantageously the following: 5.4E-01 < al < 5.5E-01, l.8E+06 < bl < l.9E+06, -3.9E-08 < cl < -3.8E-08, 2.9E-05 < dl < 3.0E-05, 9.5E-03 < el < 9.6E-03 and 8.7E+00 <fl < 8,8E+OO;

[0122] - for the calculation of the overall conductivity EC 25 = EC water, the conductivities are used EC 25i local;

[0123] - for calculating the overall conductivity EC 25 as a function of the relative height Hr (measurement) We use either Hr (measurement) = H1, or Hr (measurement) = Ho], or Hr (measurement) = H2

[0124] - a salinity S of the water is calculated as a function of the water temperature T and the overall conductivity EC 25;

[0125] - the salinity S of the water is calculated by:

[0126] S = aO + (al * Rt °'5) + (a2 * Rt) + (a3 * Rt]'5) + (a4 * Rt2) + (a5 * Rt2'5) + ((T - 15) / (1+ / :(7- 15))) * (bO + (bl * Rt °'5) + (b2 * Rt) + (b3 * Rt+ (b4 * Rt2) + (b5 * Rt2'5 ))

[0127] with:

[0128] Rt = (EC 25 / 42.914) / (cO + (cl * T) + (c2 + T2) + (c3 * T3) + (c4 * T4))

[0129] and

[0130] aO = 0.0080 bO = 0.0005 cO = 0.6766097

[0131] al = -0.1692 bl = -0.0056 cl = 0.0200564

[0132] a2 = 25.3851 b2 = -0.0066 c2 = 0.000110426

[0133] a3 = 14.0941 b3 = -0.0375 c3 = -6.9698E-07

[0134] a4 = -7.0261 b4 = 0.0636 c4 = 1.0031E-09

[0135] a5 = 2.7081 b5 = -0.0144 k = 0.0162

[0136] where the overall EC 25 conductivity of the water is in mS / cm and T is the temperature in °C;

[0137] - sediment detection is implemented, a pair of index i electrodes being subjected to sediments if its local conductivity value EC 25i is non-zero and is either less than EC 25i+i * (1 - Pk) , or greater than EC i+1 *(1 + Pk), where Pk is a detection factor chosen between 0.1 and 0.9, and in which a relative sediment height Hr sediments is calculated by the product of the index value i plus 1 by e which is the spacing step between two successive excitation electrodes along the height of the sensor, i.e. Hr sediments = e * (i +1);

[0138] - a detection of defective electrode pairs is implemented;

[0139] - a detection of defective electrode pairs is implemented, a pair electrodes of index i being defective if its local conductivity value EC 25i is non-zero and outside a range of values ​​defined by the two terminals EC 25i+i * (1 - Ps ) and EC i+i *(1+ Ps) and if EC 25i+i is non-zero where Ps is a sensitivity factor chosen between 0.1 and 0.9;

[0140] - an electrode fouling type detection system is implemented;

[0141] - a detection of the type of electrode fouling is implemented among the defective electrode pairs;

[0142] - the detection of insulating-type fouled electrode pairs implements calculations and comparisons similar to those implemented for sediment detection but with a different detection factor Pk;

[0143] - when measuring the local electric current Ii and the local voltage V, one applies to the pair of electrodes a periodic alternating voltage of determined excitation frequency, said alternating voltage being in the form of squares comprising plateaus of successive voltages of opposite signs;

[0144] - during the measurement phase, the determined excitation frequency is chosen in a set of measurement frequencies based on a presupposed or previously calculated conductivity of the water;

[0145] - the periodic alternating voltage is generated by an H-bridge;

[0146] - the periodic alternating voltage comprises successive voltage plateaus of opposite signs and of the same absolute value;

[0147] - the periodic alternating voltage comprises successive voltage plateaus of opposite signs, of the same absolute value and of the same duration of each plateau so that the periodic alternating voltage has a crest factor equal to 1;

[0148] - in a calibration phase, for each frequency of the set measurement frequencies, the cell constants K i;

[0149] - in the measurement phase, the cell constants Kt corresponding to the determined excitation frequency used;

[0150] - in a calibration phase, a measurement offset value Z is determined fluent.

[0151] The solution proposed by the invention also relates to a measurement system specially configured to ensure the implementation of the method of the invention.

[0152] More specifically, the invention relates to a system for measuring at least one parameter of water from a sanitation network, the system being specially configured to ensure the implementation of the described process and comprising an H-bridge.

[0153] Other advantageous features of the system according to the invention, taken individually or in all technically possible combinations, are as follows:

[0154] - the system includes hardware means, including computing power, enabling execution one or more actions, e.g. determinations and calculations, of the process of the invention;

[0155] - the system intended for measuring at least one parameter of water in a network The sanitation system includes a sensor having electrodes on its surface, including a reference electrode and a determined number N of excitation electrodes, the reference electrode being vertically elongated and the excitation electrodes being spaced equidistant from each other and vertically aligned parallel to the reference electrode, each excitation electrode defining with the reference electrode a pair of indexed measuring electrodes i, the index i being an integer between 0 and AM, the pair of electrodes indexed 0 being the bottom pair of electrodes of the sensor, the system further comprising an electronic assembly including a constant voltage generator circuit, an H-bridge, a bridge supply current measurement circuit, a bridge supply voltage measurement circuit, an analog demultiplexer, a microcontroller with a control program,

[0156] the system further comprising a water temperature measurement circuit and the microcontroller with control program is configured to further acquire the temperature measurement digitally,

[0157] the H-bridge comprising a power input having two power connections receiving a bridge supply voltage, a bridge output having two output connections producing between them a bridge output voltage and a bridge control input, the H-bridge enabling, depending on the bridge control, at least to obtain between the two output connections a positive or negative bridge output voltage and of an absolute value substantially equal to said bridge supply voltage,

[0158] the demultiplexer comprising an analog output port, a set of analog input ports and an input selection control input allowing, depending on the input selection control, to connect or not, only one at a time, the selected input port to output port, each of the excitation electrodes being connected to a corresponding input port of the demultiplexer,

[0159] the reference electrode being connected to one of the two output connections of the H-bridge and each of the excitation electrodes being able to be connected via the output port of the demultiplexer to the second of the two output connections of the H-bridge,

[0160] the constant voltage generator circuit supplying the bridge supply voltage via the bridge supply current measurement circuit,

[0161] the bridge supply current measurement circuit measuring the current intended for the H-bridge supply input in order to obtain a measurement of the local electric current 11 flowing in the electrode pair selected i by the demultiplexer,

[0162] the bridge supply voltage measurement circuit measuring the supply voltage of the H-bridge in order to obtain a measurement of the voltage V i applied between the two electrodes of the electrode pair selected by the demultiplexer;

[0163] - the microcontroller with control program is configured during the measurement of said at least one characteristic of the water in the wastewater network, for:

[0164] — in a first step: control the input selection control input of the demultiplexer to connect the output of the H-bridge to an excitation electrode selected for measurement from among the electrode pairs,

[0165] — in a second step: regularly order the command entry bridge by a switching control so that the bridge output voltage can switch between positive and negative at a defined excitation frequency, and once the bridge output voltage has switched, digitally acquire at least one measurement of the bridge supply current from the bridge supply current measurement circuit, and digitally acquire at least one measurement of the bridge supply voltage from the bridge supply voltage measurement circuit, then

[0166] — in a third step: calculate, as a function of said at least one measure of acquired bridge supply current, of said at least one acquired bridge supply voltage measurement and one acquired temperature measurement, a corrected local conductance Co i and a local conductivity EC 25i or directly a local conductivity EC 25i for the index i electrode pair selected by the demultiplexer;

[0167] - the microcontroller with control program is configured to iterate the first, second and third steps in order to obtain a local conductivity EC 25i of each of the electrode pairs;

[0168] - constant voltage is a direct voltage;

[0169] - the microcontroller with control program is configured so that the voltage of output of the constant voltage generator circuit is zero outside the measurement of said at least one parameter of the water in the sanitation network;

[0170] - the microcontroller with control program is configured so that the voltage the output of the constant voltage generator circuit is zero until regular control of the bridge control input has begun and as soon as the acquisition(s) of the bridge supply current measurement(s) and the bridge supply voltage measurement(s) are completed,

[0171] - the constant voltage generator circuit is controlled by the microcontroller, the output voltage of said generator circuit can be made zero or have a constant value determined according to a command of the control program, and the control program brings the output voltage of said generator circuit to the constant value determined just after the switching command and before the acquisitions of the current and voltage measurements, then brings the output voltage of said generator circuit to the value zero just after the acquisitions of the current and voltage measurements;

[0172] - the microcontroller with control program is configured to correct the measurement bridge supply current acquired by subtracting from the measurement a leakage current Z due to the H-bridge, said leakage current being a current measurement offset value Z obtained during a calibration phase in which the demultiplexer does not connect the H-bridge to one of the electrode pairs;

[0173] - the microcontroller with control program is configured to correct the measurement bridge supply current acquired by subtracting from the measurement a leakage current Z due to the H-bridge, the demultiplexer and possibly a selected electrode pair (i.e. connected to the H-bridge), the leakage current being a current measurement offset value Z obtained during a calibration phase in which the sensor is dry, the electrode pairs not being immersed in contact with water;

[0174] - in the second step, the acquisitions are synchronized with the commands of switching of the bridge output voltage and acquisitions are carried out after a determined delay following a command to switch the bridge output voltage so that said bridge output voltage is stabilized during the acquisitions;

[0175] - the analog demultiplexer is bidirectional;

[0176] - the H-bridge has two push-pull circuits between the two connections power supply and the two output connections are at the two midpoints of the two push-pull circuits;

[0177] - the bridge output voltage which switches between positive and negative at a frequency The defined excitation is a square signal with a zero average value over one period;

[0178] - the bridge output voltage which switches between positive and negative at a frequency defined excitation is a square signal whose positive voltage duration is equal to the negative voltage duration over one period;

[0179] - the H-bridge also allows, depending on the bridge command, the application or no, the supply voltage on the output;

[0180] - the H-bridge also allows, depending on the bridge control, to make the floating output (i.e. high impedance);

[0181] - the demultiplexer inputs can all be made floating (i.e. high impedance);

[0182] - one of the two H-bridge power supply connections is connected to a common ground potential of the electronic assembly, the second power connection of the H-bridge being connected to the constant voltage generator circuit via the current measurement circuit, and the bridge supply voltage measurement circuit measures the voltage between the second power connection of the H-bridge and the common ground potential of the electronic assembly;

[0183] - the microcontroller with control program includes at least one converter analog to digital (i.e., analog to digital);

[0184] - the bridge supply current measurement from the current measurement circuit bridge power is acquired by an analog-to-digital converter of the microcontroller;

[0185] - the bridge supply voltage measurement from the voltage measurement circuit bridge power is acquired by an analog-to-digital converter of the microcontroller;

[0186] - the microcontroller with control program includes at least one converter digital to analog (i.e., digital to analog);

[0187] - the output voltage of the constant voltage generator circuit is under the control of the microcontroller, said output voltage being able to be made zero or to have a constant value determined selectable by the control program;

[0188] - the excitation and reference electrodes are arranged on a material hydrophobic and non-conductive of electricity;

[0189] - the excitation and reference electrodes are arranged on a rigid material, the electrodes being rigid and the sensor is rigid;

[0190] - the excitation and reference electrodes are arranged on a flexible material, the electrodes being flexible;

[0191] - the electrodes are electrically insulated from each other on the sensor;

[0192] - each excitation electrode is a localized, point electrode with a surface reduced compared to the surface area of ​​the reference electrode;

[0193] - the set of analog input ports of the demultiplexer comprises a number of ports equal to or greater than the determined number of excitation electrodes;

[0194] - the set of analog input ports of the demultiplexer comprises a number of ports equal to the determined number of excitation electrodes;

[0195] - the excitation electrodes are aligned and staggered in height at a constant pitch, the adjacent excitation electrodes being separated by an identical distance;

[0196] - the excitation electrodes are aligned and staggered in height according to a variable pitch, the adjacent excitation electrodes being separated by a distance varying according to the height along the height of the sensor;

[0197] - the electronic assembly further comprises at least one memory circuit digital connected to the microcontroller;

[0198] - the memory of the memory circuit is persistent memory;

[0199] - the memory circuit includes digital data of which at least the cell constants K t and the current measurement offset value Z;

[0200] - the microcontroller with control program is further configured to calculate a relative height Hr (measurement of the water and, possibly, an absolute height Ha (measurement) of the water, depending on the local conductivities EC 25i Calculated for each of the pairs of electrodes of the sensor;

[0201] - the microcontroller with control program is further configured to calculate an overall conductivity EC 2s by a function using the relative height Hr (measurement) of the water;

[0202] - the microcontroller with control program is configured to use a defined excitation frequency of switching of the output voltage of the bridge which is 500 Hz when the conductivity range to be measured is less than or equal to 1999 pS / cm, 1,000 Hz when the conductivity range to be measured is between 2000 pS / cm and 9999 pS / cm, 5,000 Hz when the conductivity range to be measured is greater than or equal to 10,000 pS / cm. Brief description of the figures

[0203] On the attached figures:

[0204] [Fig. 1] represents a sensor front face intended to receive a reference electrode and excitation electrodes in an example of a sensor usable in the invention,

[0205] [Fig.2] represents a reference electrode for the front face of the example sensor of [Fig.1],

[0206] [Fig.3] represents an axial cross-sectional view of an excitation electrode for the front face of the example sensor of [Fig.1],

[0207] [Fig.4] represents a perspective view of the rear of an excitation electrode for the front face of the example sensor in [Fig.1],

[0208] [Fig.5] shows, in lateral view, a sensor device including the example of sensor usable in the invention and an adaptation support allowing the device to be fixed and adjusted on a gutter edge,

[0209] [Fig.6] shows, in lateral view, the sensor device of the [Fig.5] installed on a ditch edge

[0210] [Fig.7] schematically represents the system of the invention in an example of a design where the electronic assembly is separated into two interconnected parts and where the sensor comprises 16 excitation electrodes,

[0211] [Fig.8] represents the evolution of the local conductivities calculated for a set of 16 excitation electrodes depending on the evolution of a water level to which the system is subjected, the calculated absolute height of the water level also being represented,

[0212] [Fig.9] represents the evolution of the local conductivities calculated for a part of the Excitation electrodes depending on the evolution of a water level to which the system is subjected, some of the excitation electrodes being fouled,

[0213] [Fig. 10] schematically represents the electronic assembly of the system of the invention,

[0214] [Fig. 11] schematically represents an H-bridge as implemented in the electronic assembly of the system of the invention and comprising two output connections A and B and two power supply connections 22a and 22b,

[0215] [Fig. 12] schematically represents the H-bridge as implemented in the electronic assembly of the system of the invention, for the two opposite polarities, positive and negative, produced between the two output connections A and B, and

[0216] [Fig. 13] represents in the form of a flow diagram the steps enabling a measurement within the system of the invention. Detailed description

[0217] The following description with regard to the attached drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be carried out.

[0218] First of all, it should be noted that when a measurement on or for or of an excitation electrode is mentioned (for reasons of simplification), this corresponds to a measurement based on the measurement of the current flowing between the excitation electrode in question and the reference electrode, the two electrodes defining a pair of measuring electrodes.

[0219] Furthermore, due to the use of a sensor comprising multiple excitation electrodes, each forming, with the reference electrode, an electrode pair, each electrode pair and corresponding excitation electrode is identified by a number or index value i for ease of understanding, the index i taking a value between 0 and AM (ze [0, ..., AM] where N is the number of excitation electrodes) depending on the excitation electrode considered. By convention for the explanations of the operation of the invention, the index i = 0 corresponds to the lowest electrode pair of the sensor, i.e., excitation electrode or electrode pair number 0.

[0220] Each pair of electrodes is associated with measurements of a local electric current and a local voltage, as well as with calculation results (e.g., local conductance and local conductivity). These are also identified by an index i, which is the same as that of the pair of electrodes from which the measurements and calculations originated. This also allows a specific pair of electrodes to be assigned a result of a determination (e.g., is it a faulty or defective pair of electrodes? Is it the highest immersed pair of electrodes? ...).

[0221] Generally speaking, "local" refers to anything pertaining individually to each pair of electrodes, and "global" refers to anything pertaining to the sensor as a whole, i.e., anything resulting from the overall implementation of the electrode pairs, particularly those resulting from calculations with all or more than one pair of electrodes. Thus, a parameter (e.g., current, voltage, conductance, conductivity, correction value) indexed i corresponds to a local parameter associated with a specific pair of electrodes indexed i (or, alternatively, with number z).

[0222] Furthermore, the qualifier "relative" is used to indicate that the sensor serves as a reference. Thus, in the case of the relative height Hr (measurement), the zero of the measurement corresponds to the lower edge of the lowest excitation electrode of said sensor, i.e., with an index equal to 0, knowing that the lower edge of the reference electrode is level with the lower edge of the lowest excitation electrode.

[0223] It should also be noted that the upper edge of the reference electrode is level with the upper edge of the lowest excitation electrode.

[0224] The system and method of the invention implement measurements and calculations of conductance in order to be able to calculate the conductivity of water, typically wastewater from a sanitation network which may include or be replaced by extraneous water, i.e. not intended to be there.

[0225] For the measurement of conductance, a sensor with two electrodes called anode and cathode can be used, and the value of the resistivity of water, Rsol, can then be determined by two methods, either at constant current or at constant voltage.

[0226] For the constant current method, a constant and known current I is sent through the anode and the voltage V between the anode and the cathode is measured. For the constant voltage method, a constant and known voltage V is applied between the anode and the cathode and the resulting current I is measured.

[0227] It is this latter method which is implemented within the framework of the invention.

[0228] We can then calculate the resistivity of water, Rsol, using Ohm's law. Since conductance is the inverse of the resistivity of water, Rsol, we can calculate the conductance by considering the inverse of the calculation of the resistivity, i.e. conductance = I / V.

[0229] The conductivity of water can be obtained directly from a measurement of the conductance or directly from the current I and the voltage V (therefore without going through an intermediate calculation of the conductance). These two possibilities can be implemented within the framework of the calculations of the invention.

[0230] The resistivity and conductance values ​​obtained depend, however, on the measurement conditions and the quality of the measurement chain.

[0231] In particular, the electrodes of the different sensors have possibly different sizes, shapes, spacings and may be made of different materials, which will lead to different values ​​of conductance and especially conductivity for the same water between different sensors.

[0232] In addition, the conductance varies according to the temperature of the water.

[0233] It is therefore advantageously implemented to implement calculation methods to correct conductance measurements and to standardize and unify the conductivity values ​​obtained.

[0234] To this end, the invention implements a parameter for correcting variations in measurements due to differences between the electrodes and sensors; this parameter, called the cell constant, is specific to each pair of electrodes within the scope of the present invention. Thus, a cell constant of the indexed electrode pair i is denoted Kt hereafter.

[0235] The cell constants K, are therefore parameters for correcting the heterogeneity of the electrode pairs of the sensors.

[0236] The cell constants K, are used to correct the local conductances measured by the sensor to obtain the local conductivities.

[0237] We therefore implement a correction parameter for variations in measurements due to differences between electrodes and sensors, this parameter being called cell constant and denoted K t in the following, the index i resulting from each pair of electrodes (indexed z) having a cell constant which is specific to it.

[0238] Thus, within the framework of the invention implementing a sensor with multiple excitation electrodes (i.e., as many pairs of electrodes), an operation is provided The sensor calibration process allows for obtaining the cell constants Kt for each of the excitation electrodes (i.e., each electrode pair). These constants can differ from one excitation electrode to another and from one sensor to another. The cell constants Kt, obtained during the calibration operation, are preferably stored in persistent, i.e., non-volatile, system memory so that they can be used in subsequent measurements without having to repeat calibration operations. Ideally, this storage should be in persistent memory within the sensor itself, since these cell constants are specific to the calibrated sensor.

[0239] The cell constants Ki are therefore determined for each sensor and for each pair of electrodes (i.e., selected excitation electrode and reference electrode) during a calibration phase in which a standard solution of known conductance value is used, allowing Kt = Conductance measured for the selected i-index electrode pair.

[0240] It will be seen that it is advantageous to obtain these cell constants K h for each of the excitation frequencies that can be used in the system.

[0241] In addition, a correction can be implemented for the measurements of the local voltage V, and the local electric current 11.

[0242] In the described embodiment, only the local electric current 11 is corrected. Regarding the local voltage V, which is not measured directly across the selected electrode pair, it is assumed that, given the low current flowing in the water between the electrodes, the voltage drops in the circuit supplying the current to the electrode pair are negligible. In another embodiment, a correction of these voltage drops is also provided.

[0243] Regarding the correction of local electric current measurements Ih, a calibration is performed to determine a current measurement offset value, Z, which allows for the calculation and zeroing of leakage currents that may exist within the system's measurement chain. These leakage currents are, for example, the leakage currents of semiconductors and capacitors used in the system's measurement chain and / or leakage currents between electrodes. A single current measurement offset value, Z, is used for each measurement frequency.

[0244] Thus, in the described implementation, each local electric current 1 is corrected by a single value Z of current measurement offset for the measurement frequency, said value Z having been determined during a calibration phase.

[0245] As before, the current measurement offset Z values ​​are preferably stored in persistent system memory so that they can be used in subsequent measurements.

[0246] Moreover, while it is preferable to carry out measurements at a water temperature that corresponds to that used for calibration, in particular calibration with the standard solution, typically 25 °C, it is more advantageous to implement a correction of the effects of temperature by calculation.

[0247] Thus, for the calculation of both local and global conductivities, temperature is taken into account during measurements because of the strong influence of temperature on conductivity and conductance.

[0248] In general, the effect of temperature is non-linear. However, in the context of the implementation of the invention with water from a sewage network, the temperature range encountered is relatively limited and it is generally assumed that the effect of temperature is linear in said range and that the variation in conductivity is 2% per degree Celsius.

[0249] Thus, in order to standardize the measurement results with regard to the effects of temperature, a reference temperature was chosen to provide the results of the measurements and calculations of local and global conductivities. The most commonly accepted reference temperature is 25 °C, and we then speak of conductivity at 25 °C (here: local conductivity EC 2si and global conductivity EC 25).

[0250] It is this reference temperature of 25°C which has been chosen in the context of the invention but it is understood that the means of the invention can simply be applied to other reference temperature values ​​and / or other rates of variation of conductivity.

[0251] For water in a wastewater network, a calculation of local conductivity is implemented within the framework of the invention at the reference temperature of 25°C and with correction by cell constant K, according to the formula:

[0252] EC 25i = CO^K^ l + (Cr-25)*0.02)

[0253] with EC 2si the local conductivity at 25°C in S / cm for the pair of index i electrodes; Co i the corrected local conductance for the pair of index i electrodes, K t the cell constant of the pair of index i electrodes, T° the temperature measured in °C of said water and Co i = (I — Z) / V i where Z, is the local electric current flowing in the pair of index i electrodes and V, the voltage applied between the electrodes of said pair of index i electrodes, the current and voltage being measured and acquired in the system.

[0254] It is this calculation of the local conductivity EC 25i taking into account the temperature which is implemented for the calculation of the relative height Hr (measurement j of the water and the global conductivity EC 25 of the water.

[0255] The invention also implements an excitation of the electrodes by an alternating voltage during the measurements, which causes reversals of the current flowing between the two electrodes of the electrode pair.

[0256] Indeed, when a direct voltage is applied between an anode and a cathode in a conductive liquid medium, the circulating current produces an electrolysis which will create a polarization which will quickly render the electrodes inoperative.

[0257] To avoid this polarization effect, an H-bridge is used in the electronic assembly of the system, and its output sends an alternating voltage to the electrodes during measurements. This voltage is a square wave signal, consisting of positive and negative pulses of the same duration and the same absolute value of amplitude / voltage, so that the average voltage applied between the excitation electrode and the reference electrode is zero (only one pair of these electrodes is excited during a measurement).

[0258] Outside of measurements / acquisitions, the H-bridge is in an open configuration (i.e., floating output) or its power supply is disconnected. As a result, no voltage is present at its output. Alternatively or as a complement, the demultiplexer is deselected, i.e., its input / output ports are made non-conductive, and its input ports are left floating, so that no current can flow through the electrodes and the water.

[0259] The H-bridge is controlled by a microcontroller with a control program for the entire electronic system. This microcontroller with a control program is configured so that the excitation frequency for the AC voltage produced at the output of the H-bridge is variable according to the conductivity range to be measured. Preferably, the microcontroller with a control program adapts the excitation frequency for the AC voltage based on initial conductivity measurements. If the excitation frequency used is correct for the measurement(s), the frequency remains unchanged; otherwise, it is modified. This modification is carried out in such a way that the excitation frequency increases with conductivity.

[0260] As an example of frequencies defined according to measurement ranges, we propose:

[0261] - for a conductivity (pS / cm) between 0 and 1999, an excitation frequency of 500 Hz

[0262] - for a conductivity (pS / cm) between 2000 and 9999, an excitation frequency of 1000 Hz

[0263] - for a conductivity (pS / cm) of 10000 and above, an excitation frequency of 5000 Hz

[0264] Materially, the system of the invention comprises several elements: a sensor and an electronic assembly.

[0265] In Figures 1 to 4 and 7, the sensor 1 consists of a vertically elongated housing 12 on the surface of which the excitation electrodes 10 and reference electrodes 11 are arranged. The sensor 1 comprises a reference electrode 11 and a number of excitation electrodes 10, generally a multiple of 8, for example, 16, 32, or even 64 excitation electrodes 10. The excitation electrodes 10 are circular with a diameter of 5 mm and are spaced 5 mm apart, with the centers of two successive excitation electrodes separated by 10 mm. The reference electrode 11 is vertically elongated along the height of the sensor 1. The lower and upper ends of the reference electrode are preferably rounded. The width of the reference electrode is substantially constant along its height. The excitation electrodes 10 appear substantially point-like relative to the reference electrode 11.The excitation electrodes 10 are aligned vertically parallel to the reference electrode 11 and at a constant distance from the latter.

[0266] [Fig.l], the housing 12 is shown alone and it has on its surface orifices 13, 14 passing through the thickness of the wall for fixing the electrodes on the housing.

[0267] [Fig.2], the reference electrode 11 is shown alone and it includes pins of attachment to the housing 12 and intended to be placed in the orifices 13 for fixing the reference electrode to the housing and also electrical connection of the latter inside the housing.

[0268] Figures 3 and 4, one of the excitation electrodes 10 is shown alone and is in the approximate shape of a mushroom and is intended to be placed in one of the orifices 14 for fixing the excitation electrode to the housing 12 and also for electrical connection of the latter inside the housing.

[0269] It is understood that the electrodes 10, 11 are flush with the surface of the housing 12. The fixings and electrical connections are made by screwing screws into the bored and tapped pins of the reference electrode 11 (or by bolting if the pins are threaded) and into the tapped bores of the excitation electrodes 10. Once the electrodes 10, 11 are installed, fixed, and electrically connected to the other elements arranged in the housing 12, the latter is finally closed in a hermetic manner. Advantageously, the contents of the housing can be filled with a polymerizable filling material, for example, an elastomer.

[0270] The sensor 1 which is disposed in contact with the water of the sanitation network therefore has on its surface electrodes 10, 11 which are or are not immersed in contact with said water depending on the level / height of said water along the height of the sensor.

[0271] In an application involving wastewater flowing through a channel 4, as shown in Figures 5 and 6, the sensor 1 is advantageously mounted on an adapter bracket 2 comprising a swiveling base 3 fixed to the edge of the channel 4. The swiveling base 3 allows adjustment of the sensor 1's position so that it is vertical and the reference electrode 11 is also vertical (and thus the alignment of the excitation electrodes 10 is also vertical). The adapter bracket 2 may also include a means for adjusting the height of the sensor 1 relative to the base 3, e.g., by sliding, so that the sensor can be lowered or lowered more or less deeply into the channel 4. Advantageously, the sensor housing is of reduced thickness so as not to disrupt the water flow in flow measurement applications.

[0272] The electronic assembly [Fig. 10] comprises several electronic circuits which are preferably arranged in different locations.

[0273] These electronic circuits include at least one constant voltage generator circuit 15, an H-bridge 23, a bridge supply current measurement circuit 16, 17, 18, 20, a bridge supply voltage measurement circuit 21, an analog demultiplexer 26, a microcontroller with a control program 28, at least one digital memory circuit connected to or internal to the microcontroller, including persistent memory, and a water temperature measurement circuit 29 for the wastewater network. Other electronic circuits may be provided, for example, a communication interface circuit, wired (e.g., Modbus RS485 communication) or wireless, for exchanging data (e.g., measurements) and / or programs with the outside of the system. For example, a display interface circuit (e.g., measurement display), and an input interface circuit (e.g., a waterproof keypad).

[0274] Preferably, as in the embodiment shown [Fig. 7], the analog demultiplexer 26 and the sewage network water temperature measurement circuit 29 are housed in the sensor 1 housing 12, with the remaining electronic circuits housed in a separate housing, referred to as the control box 6, located away from the sensor housing. The two are connected by a wired link 5 (e.g., I2C protocol). The control box 6 includes a wired link 7 for communication, advantageously Modbus RS485 communication, with the outside of the system. It is understood that other means of communication can be implemented in other embodiments.

[0275] Modbus implements registers and advantageously some of these registers allow, if called, to trigger an action, for example, a measurement, a system reset, a system calibration.

[0276] Indeed, the demultiplexer 26 is responsible for demultiplexing the excitation signal 25A, 25B coming from the H-bridge 23 to select / connect one at a time of the excitation electrodes 10. However, the sensor 1 can have 16 excitation electrodes, or even more: 32 or 64, and it is preferable to reduce the length of the connections between the demultiplexer 26 and the excitation electrodes 10 and also to avoid a wire connection 5 with so many wires.

[0277] Such an arrangement in a sensor 12 housing and a control 6 housing the microcontrollers leaves all attitude to choose the location of the control 6 housing which can thus be placed in a safer and more accessible location if necessary.

[0278] The microcontrollers 28 advantageously used in the system have the advantage of comprising, in addition to a microprocessor, interface circuits, in particular one or more analog-to-digital converters (ADCs) 30, and memory, e.g. persistent EEPROM / “Flash” memory and RAM, and are possibly reprogrammable. However, it is planned to implement a separate persistent memory connected to the microcontroller for storing data. In particular, data concerning the sensor can be stored in persistent memory in the sensor housing, including sensor configuration data (e.g., number of excitation electrodes), electrode-specific calibration data, e.g., the cell constants K, of the different excitation electrodes. It is also advantageous to store in the system, in particular in the microcontroller, system-specific and / or sensor-specific data, e.g.The Z offset value of the current measurement allows for the calculation of zeroing of leakage currents, more precisely allowing for the suppression / correction of the effects of leakage currents in the measurements.

[0279] These usable microcontrollers may also include one or more analog-to-digital converters (i.e. ADC “Analog to Digital Converter”), one or more digital-to-analog converters (i.e. DAC “Digital to Analog Converter”), means of communication including in particular SPI (i.e. “Serial Peripheral Interface”) and / or CAN (i.e. “Controller Area Network”), a real-time clock (i.e. RTC “Real-Time Clock”).

[0280] Thus, in a particularly advantageous embodiment, the housing 12 of the sensor 1 includes persistent memory storing sensor-specific configuration data, for example, the number of excitation electrodes, preferably the cell constants Kt of the different excitation electrodes, and / or any other data specific to the sensor in question. This persistent memory in the sensor may also possibly include the sensor's serial number, its date of manufacture, and, optionally, the version number(s) of the microcontroller programs that can use the sensor in question.

[0281] In one embodiment, the persistent memory of the system (including that of the sensor) can be used to store information on events (e.g., breakdowns, repairs) or actions that have occurred.

[0282] Thus, it is possible to change a sensor in a system without having to recalibrate / recalibrate the whole system, the microcontrollers 28 with control program of the control box 6 being configured to adapt to different sensors using the proper configuration data of each sensor contained in the persistent memory of sensor 1.

[0283] As an example of a microcontroller, the STM32L431RCT6 can be used, which has a persistent "Flash" memory of 256K-bit and a RAM of 64K-bit.

[0284] Preferably, the power supplies and / or activations of the electronic circuits of the electronic assembly are under the control of the microcontroller in order to be able to reduce the consumption of the system as much as possible outside of measurement times, the microcontroller itself being able to switch to a low power consumption mode.

[0285] For generating the alternating voltage applied to the electrodes during measurement, an H-bridge 23 is used (Figures 11, 12). This H-bridge 23 has a power input with two supply connections 22a and 22b receiving a bridge supply voltage. It also has a bridge output with two output connections (ref. A) 25A and (ref. B) 25B producing a bridge output voltage between them. It also has a bridge control input 24 allowing each of the semiconductors in the two push-pull (i.e., symmetrical configuration) it comprises to be configured as either conducting or non-conducting. The bridge control input 24 allows, depending on the bridge commands 24, a cutoff of the voltage on the bridge output (bridge output A / 25A and B / 25B); and voltage inversions on the bridge output.

[0286] The H-bridge 23 includes a first push-pull with two controlled switches 31BH and 31BL and common / midpoint output B, typically MOS transistors, arranged between the two supply connections 22a and 22b. The H-bridge 23 also includes a second push-pull with two controlled switches 31AH and 31AL and common / midpoint output A, typically MOS transistors, arranged between the two supply connections 22a and 22b.

[0287] Depending on the transistors made to conduct, the bridge supply voltage (22a-22b) is sent to the output of bridge A, B inverted or not ([Fig. 12]) and as a result the current flowing (through 25A, 25B) in the electrodes is alternately reversed.

[0288] The reference electrode 11 is connected to the output connection A (via 25A) of the H-bridge 23.

[0289] The analog demultiplexer 26 allows one excitation electrode 10 to be selected at a time to either emit or receive the current flowing through the electrodes (i.e., one excitation electrode and the reference electrode) due to the application of the bridge output voltage (via 25A, 25B). The demultiplexer 26 has an analog output port connected to the output connection B (via 25B) of the H-bridge 23. The demultiplexer 26 includes a set of analog input ports, each connected to a corresponding excitation electrode 10. The demultiplexer 26 also includes an input selection control input which, depending on the input selection command (by 27), allows the selected input port to be connected or disconnected, only one at a time, to the output port. For this purpose, the unselected input ports are made floating (i.e., high impedance). In one embodiment, the input selection control input can be used to disable the demultiplexer, i.e., to break all electrical connections between the output port and the input ports, for example, by setting all output ports to high impedance.

[0290] For the H-bridge 23, it is possible to use an electronic component normally used for the control of direct current (DC) motors. This type of component allows control of the direction of rotation of a DC motor by reversing the current direction and also control of its rotational speed using pulse-width modulated (PWM) signals. This latter capability allows control of the excitation frequency of the square wave signal produced at the output of the H-bridge.

[0291] The constant voltage generator circuit 15 is a simple voltage regulator controlled (by 19) by the microcontroller 28. This control is either on / off or, in a more advanced mode, can act on the value of the generated constant voltage, for example, by varying it between 2 V and 5 V. In the example described, the constant voltage generator circuit 15 is controlled by the microcontroller in an on / off manner (by switching its power supply on or off) and is configured to generate a fixed voltage of 3 V. Its output impedance is sufficiently low to consider that the system operates at a constant voltage for the currents to be generated in the electrode circuit.

[0292] The constant voltage generator circuit 15 provides the bridge supply voltage (at 22a) via the bridge supply current measurement circuit 16, 17, 18, 20.

[0293] The bridge supply current measurement circuit allows the current to be measured at the supply input of the H-bridge. This supply current entering (via 22a) the H-bridge 23 is approximately equal to the current passing through the bridge output (via A / 25A and B / 25B) and therefore to the current passing through electrodes 10, 11. However, the H-bridge 23 may itself consume some of the current supplying it, and even if this self-consumption is small and could be considered negligible, it is preferable to take it into account and subtract it from the bridge supply current measurement used to calculate the local conductance and / or local conductivity. To this end, a correction is implemented in the current measurement by using a current measurement offset value Z. to perform by calculation a zeroing of the leakage currents that may exist within the system (more precisely allowing to eliminate / correct the effects of leakage currents in the measurements).

[0294] The determination of the zeroing data Z is based on the fact that the current measurement must return zero when no current flows through the electrodes, for example because the sensor is dry or the demultiplexer is deactivated and / or the bridge output is floating (none of the H-bridge transistors are conducting) or, less preferably, both outputs A and B are grounded or at the supply potential (voltage at 22A). In practice, and more simply, the determination of the zeroing data Z during the calibration phase is carried out by dry-circuiting the sensor.

[0295] The bridge supply current measurement circuit uses a shunt resistor 16, and the voltage drop across the shunt 16 is measured by a differential amplifier 18 whose output voltage VI (at connection 20) is proportional to the current flowing through the shunt 16. Preferably, the shunt value is as low as possible; for example, a 0.5Q ±1%, 1W shunt can be used. Advantageously, a differential filter 17 is implemented at the input of the differential amplifier. Given the excitation frequency of the signal produced by the H-bridge, between 500 Hz and 5000 Hz, the differential low-pass filter across the shunt resistor has a cutoff frequency of 800 Hz to eliminate any disturbances related to the generation of the square wave AC signal by the H-bridge.Connection 20 transmits the voltage VI to an analog-to-digital converter (ADC) 30 of the microcontroller 28 so that the latter can digitally acquire the value of the measured current.

[0296] The bridge supply voltage measurement circuit 21, which measures the bridge supply voltage, consists of a connection 21 to line 22a (i.e., downstream of the shunt 16, with the constant voltage generator circuit 15 considered upstream of the shunt) used to supply the H-bridge 23. Connection 21 transmits the voltage V2, corresponding to the H-bridge supply voltage 23, to an analog-to-digital converter (ADC) 30 of the microcontroller 28 so that the latter can digitally acquire the voltage value. Filtering may be implemented on connection 21.

[0297] Electronic components for overvoltage protection can be provided on the power lines coming out of the H-bridge and leading to the electrodes.

[0298] The system of the invention can be applied to the implementation of a "data logger", that is to say, a recorder / device for collecting data from the sensor. The system then includes a sufficient amount of persistent memory to collect at least the measurements resulting from the calculations performed and the time references. corresponding (i.e., the time of measurement). For this purpose, a dedicated persistent memory circuit can be implemented, for example, in the form of a removable memory card. It is also possible to offload the collected data via the Modbus wired communication link 7. Alternatively, wireless communication can be implemented.

[0299] In a particular embodiment the electronic assembly further includes a real-time clock electronic circuit (i.e. date + time) if the microcontroller does not include one or cannot handle simulating one.

[0300] The program executed by the microcontroller can advantageously optimize system power consumption and implement numerous radio and / or wired communication protocols. The program is preferably configured to perform measurements and possibly collect them with many types of sensors, since sensors advantageously have persistent memory containing their characteristics, and the microcontroller program allows the measurements, including calculations, to be adapted to the sensor used.

[0301] The program is advantageously configured with specific low-level libraries provided by the microcontroller manufacturer, which constitute a first layer of hardware abstraction, and high-level libraries for the component and application layers. It is also advantageously implemented for the program with a so-called "Board Support Package" layer that describes the internal and external peripherals specific to the electronic assembly in order to allow the system to be used with various peripherals; the peripherals used are described therein so that the program can adapt to them.

[0302] The procedure for a measurement with the system is now described.

[0303] The measures can be triggered in two different ways:

[0304] -Automatically when the sensor is powered on, then upon user request,

[0305] - Only upon user request.

[0306] The user can trigger a measurement by writing any value to a specific Modbus register. When a measurement is triggered, the following steps are executed:

[0307] 1. The excitation frequency is determined based on the last value of Local or global conductivity is measured. If no measurement has been taken prior to the current one, a default excitation frequency is used. A "Num, Electrode" counter variable for electrode pair selection is reset to zero.

[0308] 2. The selected excitation frequency is applied to the H-bridge component in the form of a PWM signal allowing to produce at the output of the bridge a periodic square wave.

[0309] 3. The demultiplexer output corresponding to the excitation electrode of number / The index "Num, Electrode" is selected so that the outputs of the H-bridge are electrically connected to the electrode pair "Num, Electrode" via the demultiplexer. For "Num, Electrode" = 0, the lowest electrode pair of the sensor is selected.

[0310] 4. The voltage regulator is switched on and generates a 3VDC voltage at the input of the H-bridge.

[0311] 5. A 5ms delay is applied to allow the regulator to rise in voltage.

[0312] 6. The voltages VI and V2 are measured by the analog-to-digital converter of the microcontroller. These measurements are iterated a user-defined number of times (from 5 to 25, in increments of 5) according to their required accuracy. The voltage values ​​VI and V2 used for subsequent calculations are then averages of these iterated measurements.

[0313] 7. The voltage regulator is off.

[0314] 8. The local electric current 11 is calculated from the average value of VI. The local voltage V, being equal to the average value of V2. The index i being equal to the value of the variable "Num, Electrode".

[0315] 9. The local conductance of the sewage network water is calculated with a The leakage currents are corrected by Z, with the correction applied at 11. The local conductivity EC 25i (where i is equal to the value of the variable "Num, Electrode") is also calculated, with the water temperature having been initially measured before the start of the steps. Each local conductivity EC 25i is stored. Alternatively, the local conductivity EC 25i is calculated directly from 1, and V

[0316] 10. Steps 3 to 9 are repeated, each time performing the measurement on the electrode next by incrementing the value of the variable "Num, Electrode" by 1: "Num, Electrode" = "Num, Electrode" +1;

[0317] and until all electrodes have been measured OR a user-predetermined number of electrode pairs (Modbus parameter STOP_AFTER) produce a local conductivity value EC 25i of zero, indicating that they are likely out of the water or faulty. This Modbus parameter STOP_AFTER is set to 2 by default. It can be modified, in particular if faulty electrodes are known to exist. For example, this parameter can be increased in multiples of 2.

[0318] It is therefore understood that only the pair of electrodes undergoing the measurements is supplied by the H-bridge and that the measurements are carried out on only one pair of electrodes at a time.

[0319] More specifically, it is presented in relation to [Fig.13], a flow diagram in the case where the measurement to be obtained is the overall conductivity EC 2s corrected for temperature for a sensor of 16 pairs of electrodes.

[0320] The measurement process begins with a temperature measurement, which is then stored. Next, calibration data (e.g., cell constants K) are retrieved from persistent memory (preferably persistent memory in the sensor). Then, an electrode number / index counter with the variable "Num, Electrode" is reset to zero (i.e., the selection number of the bottom excitation electrode of the sensor). The demultiplexer then selects the excitation electrode by the electrode number in the counter. The H-bridge is then activated to begin generating the square wave AC signal. During this generation, measurements of the excitation voltage (i.e., H-bridge supply voltage) and excitation current (i.e., H-bridge supply current) are acquired to record the values ​​from the analog-to-digital converter.After these acquisitions, the generation of the square wave AC signal is stopped, and the local conductivity is calculated by applying the calibration data (Z and K, for the electrode selected by the counter). The local conductivity is then stored in one of the Modbus registers. These operations are repeated after incrementing the electrode number counter to perform measurements on all excitation electrodes, working from the bottom of the sensor upwards. An electrode number test allows the process to stop once all electrodes have been measured, i.e., the stop occurs if "Num, Electrode" >= N, with A equal to 16 in this example. It is understood that additional tests can be added, for example, to stop the sweep if two successive local conductivity measurements are zero while the previous ones were not.

[0321] Generally speaking, the measures can be triggered in two different ways:

[0322] - Automatically when the system is powered on and then on request from a user, or

[0323] - Only at the request of a user. Indeed, the system is configured as A programmable logic controller (PLC) implements a Modbus communication protocol in RTU mode, here RS485, and the user connected to the system can trigger an activity, in this case a measurement, by writing to a specific Modbus register. It is understood that other means and communication protocols can be implemented in other embodiments.

[0324] In the case of an application where the system is used as a data logger / data collection device, the measurements are carried out automatically according to a predefined program, for example periodic or conditional (e.g. temperature variation, specific detection...).

[0325] It is assumed that, given the rapid nature of the measurement process, the temperature of the wastewater network does not change significantly during the measurement and, consequently, the temperature is measured only once (although iterations may be implemented during this single measurement to perform averaging and increase the accuracy of the temperature measurement) at the very beginning of the process. The temperature value obtained is stored in memory, typically RAM, for the purposes of calculating local conductivities corrected for temperature effects. The temperature value obtained is also stored in a Modbus register so that it is accessible to users. In the case where the system is used as a data logger, the temperature value can also be associated with the recorded / collected measurements.

[0326] In order to perform the measurement, it is also necessary to retrieve the calibration data, i.e., the cell constants Kt and the current measurement correction offset value Z, which are stored in the sensor's persistent memory if accurate measurements are desired, and the sensor configuration data, in particular the number of excitation electrodes and / or demultiplexer input ports. Note that this latter information can potentially be obtained indirectly from the number of cell constants Ki, each of which is specific to a given excitation electrode.

[0327] For the remainder of the explanation of the example described, it is conventionally assumed that the excitation electrodes (and therefore the corresponding electrode pairs) are referenced / numbered from 0 to 15 from the bottom of the sensor to the top of the sensor, which has 16 electrode pairs. Due to the configuration of the electronic assembly, measurements can only be taken with one excitation electrode energized at a time, and it is therefore necessary to scan all the excitation electrodes to obtain measurements for each of them.

[0328] Preferably, as shown, the first pair of electrodes to be measured is number 0, i.e., the lowest excitation electrode. Thus, when, during the sweep upwards through the different electrodes successively, a local conductivity measurement is zero, the upper level / plane of the sewage network water can be considered to be just below that of zero local conductivity if the previous excitation electrodes had a non-zero local conductivity, and the sweep can then be stopped. However, as a safety measure, it is preferable to continue the sweep in case the zero local conductivity is due to an anomaly (e.g., a faulty electrode, a defect in the electronic circuit, and / or (of the wiring) because in this case there will be at least one pair of electrodes above with non-zero local conductivity. As an interim measure, a single additional measurement can be taken on the next excitation electrode, i.e., just above the one with zero measurement, which will give a measurement of zero local conductivity (making it more likely that the upper level / plane of the sewage network water is indeed lower) or will give a measurement of non-zero local conductivity (which will make it likely that there is an anomaly with the excitation electrode with zero local conductivity measurement).

[0329] An electrode counter for selecting the input port of the demultiplexer 26 is initialized to 0; this counter is used to count the scans of the different excitation electrodes. The value of the electrode counter is passed to the program function responsible for the demultiplexing.

[0330] Once the selected excitation electrode is connected by the demultiplexer to the output of the H-bridge 23, the generation of the square wave AC signal is started by control (by 24) of the H-bridge 23, which is powered by a DC voltage of typically 3V supplied by the constant voltage generator circuit 15. The constant voltage generator circuit 15 advantageously receives its power supply via a switch, e.g., a MOSFET, to limit system power consumption outside of measurement periods. It is understood that this switch is made conductive to provide this typical 3V. Preferably, the control (by 24) of the H-bridge 23 for generating the square wave AC signal is started slightly before the constant voltage generator circuit 15 supplies the typical 3V. Note that if the output of the H-bridge 23 can be made floating (i.e.(no current flowing through the electrodes) independently of the control (by 24) of the H-bridge 23 for generation of the square AC signal, then the order of application of the power supplies will be less important and the output will be left floating until the activations of the power supplies and the control of the bridge for generation of the square AC signal have been made.

[0331] After a short stabilization time, for example of 5ms for an excitation frequency of 500Hz, the current and voltage from the bridge supply current measurement circuit 16, 17, 18, 20, and the bridge supply voltage measurement circuit 21, respectively, are acquired by the analog-to-digital converter of the microcontroller.

[0332] These measurements and acquisitions are iterated for each pair of electrodes to perform averaging that improves accuracy. Thus, averages are taken over five acquisitions for the excitation current and voltage. These iterations correspond to a number n of measurements, e.g., from 5 to 25 in increments of 5, determined by the user according to their accuracy requirements.

[0333] The measured current is obtained from the acquired (averaged) value of VI ([Fig. 10]) via connection 20.

[0334] The measured voltage is obtained from the acquired (averaged) value of V2 via connection 21.

[0335] The local conductivity (i.e., conductivity for the selected excitation electrode) is calculated by implementing a leakage current correction using the current measurement offset value Z, a correction with the cell constant Kt, and taking into account the effects of temperature. The calculation is as follows:

[0336] EC 25i = coi*Ki ! + (fr - 25) * 0.02)

[0337] with Co i = (I — Z) / V i the local conductance corrected for leakage currents for the pair of electrodes of index i, EC 25i the local conductivity reduced to 25°C in S / cm for the pair of electrodes of index i; K t the cell constant of the pair of electrodes of index i, T° the temperature measured in °C of the sewage network water.

[0338] This / these local conductivity calculations EC 25i can be carried out before proceeding to the measurement of the next excitation electrode or, then, after the end of the local current and voltage measurements (i.e. after the last pair of electrodes measured).

[0339] Once the current and voltage acquisitions have been carried out, the power supply to the constant voltage generator circuit 15 is cut off and the bridge control for generating the square AC signal is stopped.

[0340] These same operations are repeated to scan each of the pairs of electrodes until, preferably, an electrode with zero local conductivity is encountered (or another criterion as explained above in consideration of the possibility of an anomaly).

[0341] For each selected excitation electrode and acquisition of current and voltage then averaging, the calculations of local conductivities are carried out according to the formulas presented within the framework of the present invention.

[0342] The local conductivity values ​​thus obtained are stored in persistent system memory and preferably in Modbus registers.

[0343] Preferably, the excitation frequency for switching the output voltage of the H-bridge used to reverse the direction of the electrode excitation current is determined based on the last measured local conductivity value. If no measurement has been taken before the one initiated, a default excitation frequency is used.

[0344] The selected excitation frequency is applied to the H-bridge circuit as a bridge control signal, generating the previously described square AC voltage at the H-bridge output. Depending on the electronic component which is Used for the H-bridge, this bridge control can be a PWM signal or a square wave signal.

[0345] The local conductivity values ​​EC 25i stored for each excitation electrode of the sensor can then be used to calculate the overall conductivity EC 25, to calculate salinity, to calculate water level, to calculate sediment height, to detect defective or failing electrodes and the type of fouling...

[0346] The local conductivity values ​​EC 25i can also be stored for different times, e.g. four times a day, to allow the determination of changes in the water and, for example, its composition.

[0347] Regarding the calculation of the water level, it is possible to use the system to determine the relative water level with respect to the sensor.

[0348] In the case of the sensor whose excitation electrodes are spaced center to center of 10mm (i.e. the spacing step e between two successive excitation electrodes along the height of the sensor is equal to 10 mm), it is possible to determine the water level with an accuracy substantially equal to 10 mm if considering the on-or-none, i.e. transition from a measurement of a non-zero local conductivity to a zero local conductivity for the next pair of electrodes upwards.

[0349] However, thanks to the invention, it is possible to precisely measure the local conductivity EC 25i and therefore to follow the evolution of these values ​​and thus millimeter variations in the water level.

[0350] To this end, it is proposed to calculate the relative height Hr (measurement) = H; or Hr (measurement) = Ho i or Hr (measurement) = H 2. The system can be configured to be able to perform the three calculations or, preferably those of Hr (measurementj = Ho 2 and Hr (measurementj = H 2 at the choice of the user or according to logical tests.

[0351] From the relative height Hr (measurement) of the water, an overall water conductivity can then be calculated, i.e., EC 25 = average EC (based on EC 25 = water EC). The system can be configured to perform both calculations at the user's choice or according to logical tests.

[0352] Regarding the calculation of salinity S, it is possible to calculate the salinity of water from its overall conductivity. The IFREMER institute published in 2004 (Ref.: Aminot A., Kérouel R., 2004. Hydrology of marine ecosystems: parameters and analyses. Ed Ifremer, 336p. ISBN 2-84433-133-5) a formula comprising numerous parameters and allowing the precise determination of salinity S as a function of conductivity and temperature.

[0353] This calculation formula is:

[0354] S = aO + (al * Rt °'5) + (a2 * Rt) + (a3 * Rt ]'5) + (a4 * Rt2) + (a5 * Rt2'5) + ((T - 15) / (l+k(T- 15))) * (bO + (bl * Rt °'5) + (b2 * Rt) + (b3 * Rt]'5) + (b4 * Rt2) + (b5 * Rt2'5 ))

[0355] with:

[0356] Rt = (EC 25 / 42.914) / (cO + (cl * T) + (c2 + T2) + (c3 * T3) + (c4 * T4))

[0357] and

[0358] aO = 0.0080 bO = 0.0005 cO = 0.6766097

[0359] al = -0.1692 bl = -0.0056 cl = 0.0200564

[0360] a2 = 25.3851 b2 = -0.0066 c2 = 0.000110426

[0361] a3 = 14.0941 b3 = -0.0375 c3 = -6.9698E-07

[0362] a4 = -7.0261 b4 = 0.0636 c4 = 1.0031E-09

[0363] a5 = 2.7081 b5 = -0.0144 k = 0.0162

[0364] where EC 25 is the overall conductivity in mS / cm and T is the temperature in °C.

[0365] This calculation, which can be executed by the microcontroller, is useful in certain applications in coastal environments where it is common for parasitic waters to be partly composed of seawater infiltration.

[0366] It should be noted that, rather than performing the complete calculation, it is advantageous to implement in the system a table of pre-calculated salinity values ​​which includes all salinity values ​​for overall conductivities between 0 and 100 mS / cm and temperatures between 0 and 35°C. Thanks to this, the calculation time for salinity is reduced to the time required to scan the table.

[0367] The calibration process of the system is now described, which allows obtaining the values ​​of the cell constants Kt and, preferably, also the offset value Z, which eliminates the effect of leakage currents that may exist within the system. The offset value Z of the current is therefore global and is used for all electrode pairs.

[0368] The system calibration is carried out by two operations:

[0369] - Calculation of cell constants K t ,

[0370] - Calculation of offset values, i.e., offset caused by leakage currents. Preferably, only one offset value Z is implemented per measurement frequency for the entire system.

[0371] These two steps are carried out by the same function of the program but independently. Indeed, the cell constants Kt are obtained by using a standard solution of known conductance at a determined temperature, preferably at 25°C, or, advantageously, by compensating for the effects of the temperature brought back to 25°C (see below), and the offset values ​​Z are obtained by putting the sensor out of water, i.e. in the open air and drying it.

[0372] The implementation of Modbus communication means is advantageously used in that the same command / action register is used for both calibration operations, the value sent in the relevant register allowing the selection of the operation to be performed.

[0373] Thus, if this sent value is zero, then the calculation of the zeroing data, Z, of the leakage current will be performed. If this sent value is greater than zero, then the calculation of the cell constants Kt will be performed, the non-zero value sent being the conductivity value of the standard solution.

[0374] During calibration operations using conductivity, local conductivity measurements are carried out with the standard solution in the same way as for a measurement of sewage water, but for the determination of the cell constants K, no correction is made during the measurement, i.e., K = 1 for i = 0, ..., N-1, and therefore raw local conductance measurements are used to determine K

[0375] - For the calculation of each cell constant, denoted K h for each pair For an indexed electrode i, we use each value of raw conductance (ie without correction, ie K, = I during measurement) measured, denoted Cei, on the standard solution and we use the following formula for calculating the cell constant Kt:

[0376] K = Standard conductivity Cei

[0377] where StandardConductivity is the conductivity of the standard solution. Note that Cei is advantageously temperature compensated at 25 °C and calibration can therefore be performed at any temperature.

[0378] Preferably, this calibration is carried out at the reference temperature of 25°C or else the local conductivities are calculated with correction for the effects of temperature.

[0379] Note that since cell constant values ​​can be influenced by the electrode excitation frequency, it is preferable to use an excitation frequency suitable for the range of conductivity values ​​that one wishes to measure. The same applies to the measurement of the conductivity of the standard solution. The following list gives an example of the relationships between the measurable conductivity ranges (pS / cm), the preferred defined excitation frequencies (Hz), and the recommended conductivities (pS / cm) of the standard solutions to be used for the corresponding intended measurement range.

[0380] Range (pS / cm) | Frequency (Hz) | Standard conductivity (pS / cm)

[0381] Oà 1 99915001 1 413

[0382] 2,000 to 9,999 I 1,000 I 5,000

[0383] 10,000 and more I 5,000 I 12,880

[0384] Depending on the application, the user can choose to calibrate 1, 2, or 3 measurement ranges. The recommended conductivity values ​​for the standard solutions are readily available from specialized retailers. The sensor must be fully immersed in the standard solution during the calibration of the cell constants Kh. Several sets of cell constants are therefore determined, one set for each of the possible excitation frequencies.

[0385] - For the correction of leakage currents, it is preferable to implement a The only offset value Z is used to correct the measured current. The offset value Z, intended to correct current measurements during the measurement phase, corresponds to the current measured when the sensor is dry and exposed to air, and no excitation electrode is selected.

[0386] The system can be implemented in the following manner to obtain the zeroing data Z:

[0387] The first excitation frequency, i.e. 500Hz, is applied to the H-bridge 23 by means of a bridge control.

[0388] The constant voltage generator circuit 15 is powered / activated to generate a 3 V DC voltage.

[0389] While the demultiplexer 26 does not select any excitation electrode (e.g., floating input port), current measurements are acquired from the bridge supply current measurement circuit 16, 17, 18, 20, and these acquired current measurements are stored.

[0390] The power supply to / disable of the constant voltage generator circuit 15 is cut off / disabled.

[0391] We average the current measurements and store the result which is Z.

[0392] These operations are preferably repeated for the three defined possible excitation frequencies, i.e. 500Hz, 1000Hz and 5000Hz).

[0393] Thus, only the current is measured and acquired and this current is stored which will be used to correct subsequent current measurements (outside calibration) during the measurement phase.

[0394] It can be noted that this implementation gives an indication of the leakage currents relating essentially to the H-bridge and provides a unique zeroing data Z (i.e. independent of the electrodes) for the current.

[0395] Examples of measurement results are now presented in relation to Figures 8 and 9.

[0396] For [Fig. 8], the system with a fault-free and fouling-free sensor with 16 excitation electrodes was used and placed in a tank containing water, the level of which was first raised and then lowered. The conductivity measurements 9 for each of the 16 excitation electrodes are shown over time (conductivity and water level versus time plot). In [Fig. 8], the The conductivity for the lowest excitation electrode of the sensor is referenced 9a and the conductivity for the highest excitation electrode is referenced 9p. The calculated absolute water level is represented by the curve referenced 8.

[0397] There are also cases where the sensor may have one or more faulty electrode pairs (i.e., producing zero local conductivity measurements when immersed in water). There are also cases where the sensor may have one or more defective electrode pairs (i.e., producing non-zero local conductivity measurements that are very different from the other electrode pairs) because they are subjected to an environment containing interfering elements that lead to measurement anomalies (e.g., fouling).

[0398] More generally, a pair of electrodes is considered defective if its operation is impaired. Thus, when one or all of the electrodes of a defective pair of electrodes are located below the water surface, its local conductivity value may be higher or lower than that of the other submerged electrode pairs. When one or all of the electrodes of a defective pair of electrodes are located above the water surface, its local conductivity value may be non-zero. Therefore, tests are advantageously implemented to compare local conductivities, based on the relative water height Hr (measured) determined to ascertain whether the electrode pairs are submerged or not, in order to identify defective electrode pairs.However, when the difference in conductivity reaches a predefined threshold for a non-zero number of successive electrode pairs starting from the lowest electrode pair, the electrode pairs concerned are considered to be under / in contact with a sediment layer and not as defective.

[0399] The reasons for the appearance of a defective pair of electrodes may be the presence of a disruptive element on the surface of the electrodes, the presence of a bacterial deposit (biofilm) on the surface of the electrodes, the presence of a greasy deposit on the surface of the electrodes, etc. These reasons are therefore mainly of external origin to the sensor.

[0400] Figure 9 allows visualization of certain anomalies, e.g., one or more defective electrodes, in the conductivity measurements. The local conductivity measurements 9 for some of the sensor's excitation electrodes are shown over the time during which the water level rises (conductivity versus water level representation).

[0401] There are two distinct types of fouling for defective electrodes:

[0402] - insulating fouling, i.e. hindering the passage of current, and

[0403] - conductive fouling, i.e. facilitating the passage of current.

[0404] On [Fig.9], one of the excitation electrodes (curve 9x) has been fouled with an insulating material and another (curve 9y) has been fouled with a conductive material (wet wipe).

[0405] The two types of fouling result in very different responses:

[0406] - in the case of the insulating material, the response for the excitation electrode (9x curve) is simply attenuated in the same way that a sedimentary deposit would be.

[0407] - in the case of the conductive material, the response for the excitation electrodes (curve 9y) shows a slight conductivity when out of water.

[0408] In the latter case, if the fouling is less conductive than water, then the conductivity measured when the excitation electrode is fully immersed will be lower than normal (this is the case for 9y in [Fig. 9]). Conversely, if the fouling is more conductive than water, then the conductivity measured when the excitation electrode is fully immersed will be higher than normal.

[0409] The system is configured to detect different forms of fouling. Fouling detection for insulating fouling is performed similarly to the detection of sedimentary deposits described above, except that the detection threshold is lower. For example, if the conductivity measurement for the excitation electrode with index i gives a conductivity value x percent lower than the excitation electrode with index z+1 (i.e., the excitation electrode z+1 directly above the previous one z), then the excitation electrode with index i (i.e., the pair of electrodes with index z) is considered fouled. The value of the detection threshold x can be selected by the user, and its default value is 10%.

[0410] Fouling detection for conductive type fouling is carried out as follows (recall that excitation electrode number = 0 is the lowest electrode of the sensor). For example, if the conductivity measurement for excitation electrode number i gives a non-zero conductivity value while the measurement for excitation electrode number i-1 gives a zero conductivity value, electrode number i is considered to be fouled.

[0411] The detection and correction of anomalies in measurements is now described.

[0412] In the case where one or a few pairs of electrodes are faulty (i.e. conductivity (zero when immersed in water), it is possible to compensate for the loss of information by calculation. To this end, it is necessary to detect pairs of electrodes whose measured local conductivity values ​​are zero, i.e., exhibiting a conductivity of OpS / cm when immersed.

[0413] To this end, a detection of faulty electrode pairs is implemented, an electrode pair being faulty if the local conductivity for said electrode pair is zero, i.e. 0 pS / cm, while immersed in contact with water, i.e., if there is at least one electrode pair that gives a local conductivity non-zero and which is located at a height greater than that of the faulty electrode pair.

[0414] Advantageously, the system is configured to stop measurements as soon as a specified number greater than or equal to 2 of successive electrode pairs give a local conductivity measurement of OpS / cm and / or as soon as two electrode pairs have been detected as faulty. The presence of a zero conductivity measurement for a specific excitation electrode amidst others giving non-zero measurements signals a failure of the corresponding electrode pair. In this case, if the water level calculation uses the averages of the local conductivity measurements, a shift occurs in the water level evolution curve, which can be compensated for by knowing the spacing step e between two successive excitation electrodes along the height of the sensor (however, some uncertainty will remain regarding the level information around the detected faulty excitation electrode).

[0415] It is understood that the activation and deactivation times and the command / control times of the elements of the electronic assembly can be modified in relation to the times described, but that it is preferable that these times be chosen so that the pairs of electrodes are subjected to polarizations for the shortest possible time or at least that they cancel each other out on average (same duration of application of the current in one direction and in the other).

[0416] In certain embodiments where the electrode pairs are not vertically aligned and / or are on a flexible sensor conforming to a non-planar shape, the system can be configured to calculate a water level that takes into account the arrangement of the electrode pairs. For example, a flexible sensor conforming to the circular shape of a pipe is used, and calculations are performed to obtain a water level result measured along a vertical axis.

Claims

Demands

1. A method for measuring at least one parameter of water from a wastewater network, wherein a sensor (1) is used, intended to be disposed in contact with said water and having electrodes on its surface, including a reference electrode (11) and a determined number N, greater than one, of excitation electrodes (10), the reference electrode (11) being vertically elongated and the excitation electrodes (10) being spaced equidistant from each other and vertically aligned parallel to the reference electrode, each excitation electrode (10) defining with the reference electrode (11) a pair of electrodes, and in a measurement phase, a local electric current 11 flowing and a local applied voltage Vt are measured for each pair of electrodes of the sensor, and the local electric currents are corrected by removing a current measurement offset value Z to produce corrected local electric currents,and we calculate corrected local conductances Co i using corrected local electric currents, and we calculate local conductivities EC 25i using the products of the local conductances Co i by cell constants K, and using a temperature measurement T of said water to correct for an effect of temperature on the local conductances, and wherein we determine a relative height Hr (measurement j) of water using the local conductivities EC 25i, and wherein we calculate a global conductivity EC 25 of said water by a function having at least one parameter which is the determined relative height Hr (measurement j) of said water.

2. A method according to claim 1, wherein the relative height Hr (measurement j = H 2 of water is calculated by: H = H iast * e ) + ax 3 + bx2 + ex + d With: Y zz PP^t PC fat-1 2 with a, b, c, d predetermined constants, e the spacing step between two successive excitation electrodes along the height of the sensor, EC last the local conductivity EC 25i of the last pair of electrodes upwards still in contact with the water, i.e. the highest non-zero local conductivity electrode pair, 1 tast is the index number of the last pair of electrodes upwards still in contact with the water, the lowest pair of electrodes of the sensor having an index equal to zero.

3. Method according to claim 1, wherein the relative height Hr (measurementj = El j of water is calculated by: El i (EC mean El max / EC max) with: EC max the highest local conductivity EC 25i among the local conductivities EC 25i of all the electrode pairs of the sensor and EC mean the average conductivity measured over all the electrode pairs of the sensor, i.e. the sum of the local conductivities EC 25i divided by the total number of electrode pairs of the sensor, and H max the maximum relative height of water measurable by the sensor.

4. A method according to any one of claims 1 to 3, wherein a detection of faulty electrode pairs is implemented, an electrode pair being faulty if the local conductivity EC 25i for said electrode pair is zero while it is overcome by at least one electrode pair with non-zero local conductivity, and the number m of faulty electrode pairs is determined.

5. A method according to claim 4, wherein the relative height Hr (measurementj = Ho 2 of water is calculated by: Ho j — (EC mean H max / EC max) -FH corr with: EC max the highest local conductivity EC 25i among the local conductivities EC 25i of all the electrode pairs of the sensor and EC mean the average conductivity measured on all the electrode pairs of the sensor during the measurement phase, i.e. the sum of the local conductivities EC 25i divided by the total number of electrode pairs of the sensor, and H max the maximum relative height of water measurable by the sensor, and H corr is a height correction value calculated by H corr = e * m where m is the number of faulty electrode pairs and where e is the spacing step between two successive excitation electrodes along the height of the sensor.

6. A method according to any one of claims 2 to 5, wherein the relative water height is calculated by Hr (measurement) = Hj or by Hr (measurement) = H0i or by Hr (measurement) = H2 as a function of a result of logical tests where if ( (Zlasr < 2) or ( (Jast <SEUIL capteur) et ( (si la paire d’électrodes d’indice 1 last est non défaillante et si la paire d’électrodes d’indice 1 iast -1 est défaillante) ou (si la paire d’électrodes d’indice 1 last - 1 est non défaillante et si la paire d’électrodes d’indice 1 last - 2 est défaillante) ) ) ) alors la hauteur relative d’eau est calculée avec Hr (mesure) = H ] ou, de préférence, avec Hr (mesure) = Ho ,, sinon la hauteur relative d’eau est calculée avec Hr (mesUre) = H 2, 1 étant La valeur d’indice de la dernière paire d’électrodes vers le haut encore en contact avec le l’eau, la paire d’électrodes la plus basse du capteur ayant une valeur d’indice égale à zéro,and the sensor threshold (SENSOR THRESHOLD) being a constant function of the number N of excitation electrodes of the sensor.

7. A method according to any one of claims 1 to 6, wherein water is present on a bare bottom of the sewer network and an absolute height Ha (measure) of water in the sewer network is calculated by Ha (measure) = ZZr (measure) + ZZ OffSet with: H Offset the height between the bare bottom of the sewer network and the bottom of the excitation electrode of the lowest electrode pair of the sensor.

8. A method according to any one of claims 1 to 7, wherein the overall conductivity EC 25 is calculated by EC 25 = EC water with EC water — EC max / WHERE EC max is the highest local conductivity among the local conductivities of all the electrode pairs of the sensor and oc which is a correlation coefficient function of the relative height Hr (measurement) of water and having a value between 0 and 1, oc being calculated by: OC — 1 ln(bl Hr (measurement)) + CJ Hr (measurement) + 1 HK (measurement) + £ 1 Hr (measurement) + f 1 with at,bi,c hd t and / 7 which are predetermined constants.

9. A method according to any one of claims 1 to 8, wherein a salinity S of the water is calculated as a function of the water temperature T and the overall conductivity EC 25 ■

10. A method according to any one of claims 1 to 9, wherein a detection of defective electrode pairs is implemented, an electrode pair of index i being defective if its local conductivity value EC 251 is non-zero and outside a range of values ​​defined by the two terminals EC 251+1 * (1 - Ps ) and EC i+1 *(1+ Ps) and if EC 25i+i is non-zero where Ps is a sensitivity factor chosen between 0.1 and 0.

9.

11. A method according to any one of claims 1 to 10, wherein sediment detection is implemented, a pair of electrodes of index i being subjected to sediment if its local conductivity value EC 25t is non-zero and is either less than EC 251+1 * (1 - Pk), or greater than EC i+1 * (1 + Pk) where Pk is a detection factor chosen between 0.1 and 0.9, and wherein a relative sediment height Hr sediments is calculated by the product of the index value i plus 1 by e, which is the spacing between two successive excitation electrodes along the height of the sensor, i.e., Hr sediments = e * (i + V-

12. A method according to any one of claims 1 to 11, wherein, during the measurement of the local electric current 11 and the local voltage V i, a periodic alternating voltage of determined excitation frequency is applied to the electrode pair, said alternating voltage being in the form of squares comprising plateaus of successive voltages of opposite signs.

13. A system for measuring at least one parameter of water from a sewage system specially configured to ensure the implementation of the method of any one of claims 1 to 12 and comprising an H-bridge.

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