Measurement device and measurement method

Abstract

The invention relates to a measuring device and a measuring method. A measurement device (10) is provided with: a measurement unit (161) that measures the impedance of an electrode to be measured having a first terminal and a second terminal; and a control unit (11), the measurement unit (161) having: an operational amplifier having a first input terminal, a second input terminal, and an output terminal; and a feedback resistor which is a variable resistor having a third terminal connected to the output terminal and a fourth terminal connected to the first input terminal, the control unit (11) being configured to control the first input terminal and the second input terminal in a state in which the first input terminal is connected to the first terminal, and the feedback resistor being a variable resistor having a third terminal connected to the output terminal and a fourth terminal connected to the first input terminal. The measurement value of the impedance of the electrode to be measured is acquired on the basis of the voltage applied to the second terminal, the potential of the output terminal, and the resistance value of the feedback resistor.

Description

[0001] Cross-references between related applications

[0002] This application claims the benefit of Japanese Patent Application No. 2024-043959 filed in Japan on March 19, 2024, the disclosure of which is hereby incorporated by reference in its entirety. Technical Field

[0003] The present invention relates to a measuring device and a measuring method. Background Art

[0004] pH (hydrogen ion index) is a physical quantity that indicates the degree of acidity or alkalinity of a solution.

[0005] pH is defined by the negative common logarithm of the hydrogen ion concentration in a solution.

[0006] The glass electrode pH measurement method is a well-known method for measuring the pH of a solution. When two different solutions are placed on either side of a special glass membrane, an electromotive force proportional to the pH difference between the two solutions is generated in the glass membrane. The glass electrode pH measurement method measures the pH of a solution by measuring the potential difference generated between the glass electrode and a reference electrode due to this electromotive force.

[0007] In pH measurement devices using glass electrodes, the impedance value of the electrode changes due to electrode degradation, which reduces the accuracy of pH measurement. Patent Document 1 describes a technique for correcting pH measurement values ​​based on the measured value of electrode impedance.

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-019804 Summary of the Invention

[0009] However, the current structure has room for improvement in terms of simply and accurately measuring the impedance of the electrode.

[0010] Therefore, an object of the present invention is to enable easier and more accurate measurement of the impedance of the electrode in a pH measuring device using a glass electrode.

[0011] Regarding the measuring devices according to some embodiments,

[0012] (1) having: a measuring unit that measures the impedance of a measured electrode having a first terminal and a second terminal; and

[0013] Control Department,

[0014] The measuring unit includes:

[0015] an operational amplifier having a first input terminal, a second input terminal, and an output terminal; and

[0016] a feedback resistor which is a variable resistor having a third terminal connected to the output terminal and a fourth terminal connected to the first input terminal,

[0017] The control unit acquires a measurement value of the impedance of the electrode to be measured based on the voltage applied to the second terminal, the potential of the output terminal, and the resistance value of the feedback resistor in a state where the first input terminal is connected to the first terminal.

[0018] In this manner, the measurement device includes the feedback resistor of the operational amplifier as a variable resistor, and obtains the measured value of the impedance of the electrode being measured based on the voltage applied to the second terminal of the electrode being measured, the potential of the output terminal of the operational amplifier, and the resistance value of the feedback resistor. Therefore, the measurement device can adjust the resistance value of the feedback resistor according to the impedance of the electrode being measured, thereby enabling simple and highly accurate measurement of the impedance of the electrode being measured. For example, even when the impedance of the electrode being measured is extremely high, the measurement device can increase the resistance value of the feedback resistor based on the impedance, thereby accurately measuring the impedance of the electrode being measured.

[0019] In one embodiment,

[0020] (2) Based on the measuring device of (1), it can be formed as follows:

[0021] Also features:

[0022] a first switch that switches the terminal connected to the first input terminal and the fourth terminal between a state of being connected to the first terminal and a state of being not connected to the first terminal; and

[0023] a second switch for switching the terminal connected to the second input terminal between a state of being connected to an electromotive force terminal and a state of not being connected to the electromotive force terminal, the electromotive force terminal outputting the potential of the electrode to be measured immersed in a measuring liquid as a sample;

[0024] The control unit acquires the measured value of the impedance of the electrode to be measured in a state in which the first switch connects the first input terminal and the fourth terminal to the first terminal and the second switch does not connect the second input terminal to the electromotive force terminal.

[0025] Thus, the measuring device includes a first switch and a second switch, and switching these switches switches between a pH measurement mode for measuring the pH of the measuring solution and an impedance measurement mode for measuring the impedance of the electrode being measured. Therefore, the measuring device for measuring the pH of the measuring solution can also accurately measure the impedance of the electrode being measured simply by switching the switches.

[0026] In one embodiment,

[0027] (3) Based on the measuring device of (2), it can be formed as follows:

[0028] The control unit acquires the potential of the electrode to be measured in a state where the first switch does not connect the first input terminal and the fourth terminal to the first terminal and the second switch connects the second input terminal to the electromotive force terminal.

[0029] The pH of the measurement liquid is acquired based on the acquired potential of the electrode to be measured.

[0030] Therefore, the measuring device can measure the pH of the measuring solution and the impedance of the electrode to be measured with high accuracy using a compact structure.

[0031] In one embodiment,

[0032] (4) Based on any one of the measuring devices (1) to (3), it can be configured as follows:

[0033] The control unit obtains the temperature of the electrode to be measured,

[0034] The measured value of the impedance of the electrode to be measured is corrected based on the acquired temperature.

[0035] In this way, the measuring device corrects the measured value of the impedance of the electrode to be measured based on the temperature of the electrode to be measured, and thus can measure the impedance of the electrode to be measured with higher accuracy.

[0036] In one embodiment,

[0037] (5) Based on the measuring device of (4), it can be formed as follows:

[0038] The control unit acquires a temperature correction function indicating a relationship between temperature and impedance according to the type of the electrode to be measured.

[0039] The measured value of the impedance of the electrode to be measured is corrected using the temperature correction function.

[0040] In this manner, the measurement device corrects the measured value of the impedance using the temperature correction function according to the type of the electrode to be measured, and thus can measure the impedance of the electrode to be measured with higher accuracy.

[0041] In one embodiment,

[0042] (6) Based on any one of the measuring devices (1) to (5), it can be configured as follows:

[0043] The device further comprises a liquid grounding circuit for applying a voltage to the glass electrode and the reference electrode via a measuring liquid.

[0044] The measuring unit includes: a first measuring unit for measuring the impedance of the glass electrode as the measured electrode when a voltage is applied using the liquid grounding circuit; and a second measuring unit for measuring the impedance of the reference electrode as the measured electrode when a voltage is applied using the liquid grounding circuit.

[0045] In this manner, the measuring device includes a first measuring unit for measuring the impedance of the glass electrode while a voltage is applied via the liquid grounding circuit, and a second measuring unit for measuring the impedance of the reference electrode while a voltage is applied via the liquid grounding circuit. Therefore, the measuring device can measure the impedance of the glass electrode and the reference electrode with high accuracy.

[0046] In one embodiment,

[0047] (7) Based on the measuring device of (6), it can be formed as follows:

[0048] The control unit acquires the pH of the measurement liquid based on a potential difference between the glass electrode immersed in the measurement liquid and the reference electrode in a state where no voltage is applied by the liquid ground circuit.

[0049] As described above, the measuring device measures the pH of the measuring liquid based on the potential difference between the glass electrode immersed in the measuring liquid and the reference electrode in a state where no voltage is applied by the liquid ground circuit. Therefore, the pH of the measuring liquid can be measured with high accuracy.

[0050] In one embodiment,

[0051] (8) Based on the measuring device of (7), it can be formed as follows:

[0052] The control unit corrects the pH of the measurement liquid obtained based on the potential difference between the glass electrode immersed in the measurement liquid and the reference electrode based on the correlation between the fluctuation of the measured value of the impedance of the glass electrode and the fluctuation of the measured value of the pH of the measurement liquid.

[0053] In this way, the measuring device corrects the measured pH value based on the correlation between the fluctuation in the measured value of the glass electrode's impedance and the fluctuation in the measured value of the pH of the measuring solution. Therefore, even if deterioration of the glass electrode progresses, the measuring device can still measure the pH of the measuring solution with the highest possible accuracy.

[0054] In one embodiment,

[0055] (9) Based on any one of the measuring devices (1) to (8), it can be configured as follows:

[0056] The measuring unit includes a resistor capable of switching a resistance value within a plurality of ranges as the feedback resistor.

[0057] Therefore, the measuring device can switch the resistance value range of the feedback resistor according to the impedance of the electrode to be measured and perform measurement, so the impedance of the electrode to be measured can be measured simply and accurately.

[0058] In one embodiment,

[0059] (10) Based on any one of the measuring devices (1) to (9), it can be configured as follows:

[0060] The control unit acquires the degree of degradation of the electrode to be measured based on the measured value of the impedance of the electrode to be measured,

[0061] The acquired degree of degradation is output.

[0062] In this way, the measurement device automatically outputs the degree of degradation of the measured electrode, allowing the user to determine the degree of degradation of the measured electrode without performing impedance measurements for each measurement device. The measurement device measures the impedance of the measured electrode with high precision, thus accurately determining the degree of degradation.

[0063] In one embodiment,

[0064] (11) Based on the measuring device of (10), it can be formed as follows:

[0065] The control unit predicts a replacement time of the electrode to be measured based on the degree of degradation acquired at a plurality of time points,

[0066] The predicted replacement time of the electrode to be measured is output.

[0067] In this way, the measurement device predicts and outputs the replacement time for the measured electrode based on the degree of degradation of the measured electrode. This allows the user to take appropriate measures, such as preemptively replacing the measured electrode, as needed, before the measured electrode fails. The measurement device measures the impedance of the measured electrode with high precision, making it possible to predict and output the replacement time for the measured electrode.

[0068] Regarding the measurement methods involved in several embodiments,

[0069] (12) A measuring method of a measuring device,

[0070] The measuring device comprises:

[0071] a measuring unit that measures the impedance of a measured electrode having a first terminal and a second terminal; and

[0072] Control Department,

[0073] In the measuring method,

[0074] The measuring unit includes:

[0075] an operational amplifier having a first input terminal, a second input terminal, and an output terminal;

[0076] as well as

[0077] a feedback resistor which is a variable resistor having a third terminal connected to the output terminal and a fourth terminal connected to the first input terminal,

[0078] The measurement method includes the following steps: the control unit obtains a measurement value of the impedance of the electrode to be measured based on the voltage applied to the second terminal, the potential of the output terminal, and the resistance value of the feedback resistor when the first input terminal is connected to the first terminal.

[0079] Regarding the measurement method, in a measurement device having a feedback resistor of an operational amplifier serving as a variable resistor, a measured value of the impedance of the electrode being measured is obtained based on the voltage applied to the second terminal of the electrode being measured, the potential of the output terminal of the operational amplifier, and the resistance value of the feedback resistor. Therefore, according to the measurement method, the resistance value of the feedback resistor can be adjusted and measured according to the impedance of the electrode being measured, thereby enabling simple and high-precision measurement of the impedance of the electrode being measured. For example, even when the impedance of the electrode being measured is extremely high, the measurement method can still accurately measure the impedance of the electrode being measured by increasing the resistance value of the feedback resistor according to the impedance.

[0080] Effects of the Invention

[0081] According to one embodiment of the present invention, with respect to a pH measurement device using a glass electrode, it is possible to measure the impedance of the electrode more simply and with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 It is a diagram showing the configuration of an impedance measurement circuit according to a comparative example.

[0083] Figure 2 This is a block diagram showing a configuration example of a measuring device according to one embodiment.

[0084] Figure 3 Yes Figure 2 A schematic diagram of an example of the structure of a measuring unit.

[0085] Figure 4 This is a diagram showing a configuration example of a pH measurement circuit according to one embodiment.

[0086] Figure 5This is a diagram showing a configuration example of a pH measurement circuit according to one embodiment.

[0087] Figure 6 This is a diagram showing a configuration example of an impedance measurement circuit according to one embodiment.

[0088] Figure 7 This is a diagram showing a configuration example of an impedance measurement circuit according to one embodiment.

[0089] Figure 8 Is to express Figure 7 A diagram showing a configuration example of a circuit equivalent to an impedance measurement circuit.

[0090] Figure 9 This is a diagram showing an example of the resistance value of the variable resistor according to the switching content of the switch.

[0091] Figure 10 This is a diagram showing a configuration example of a hybrid circuit according to one embodiment.

[0092] Figure 11 Yes Figure 3 FIG. 1 is a diagram showing a configuration example of a measurement circuit portion.

[0093] Figure 12 This is a graph schematically showing the relationship between electrode temperature and impedance.

[0094] Figure 13 This is a diagram showing a configuration example of a measurement system according to one embodiment.

[0095] Figure 14 Yes Figure 13 A block diagram of a structural example of a server device.

[0096] Figure 15 Yes Figure 13 A block diagram of a structural example of a terminal device.

[0097] Figure 16 Yes Figure 13 Flowchart of an example of the operation of a measuring device.

[0098] Figure 17 Yes Figure 13 Flowchart of an example of the operation of a measuring device.

[0099] Figure 18 Yes Figure 13 Flowchart of an example of the operation of a measuring device. DETAILED DESCRIPTION

[0100] Comparative Example

[0101] Figure 11 is a diagram showing the structure of an impedance measurement circuit 90 according to a comparative example. The impedance measurement circuit 90 measures the impedance of the electrode to be measured R in a pH measurement device using a glass electrode. x The impedance measuring circuit 90 includes a resistor R9, an operational amplifier (operational amplifier:

[0102] Operational Amplifier) ​​92, and A / D (Analog-to-Digital) converter 93. Figure 1 As shown, a resistor R9 having one end connected to the ground G is connected to the input terminal of an operational amplifier 92 using a jumper (short-circuit bar) 91. A voltage V is applied. i The resistance R x The impedance measuring circuit 90 is connected to the input terminal of the operational amplifier 92. The output terminal of the operational amplifier 92 is connected to the A / D converter 93, which outputs the current signal I converted into a digital signal. i The resistance R of the electrode to be measured is obtained by using the current signal I x impedance.

[0103] Regarding the operational amplifier 92, a virtual short circuit is implemented so that the potential difference between the non-inverting input terminal and the inverting input terminal becomes 0V. In the equilibrium state, the current input to the non-inverting input terminal is 0. Therefore, the measured electrode R x The current I1 flowing through the resistor R9 is calculated by equation (1).

[0104] I1=V i / (R x +R9) (1)

[0105] The potential V2 of the non-inverting input terminal of the operational amplifier 92 is calculated by equation (2).

[0106] V2=R9×I1 (2)

[0107] If we substitute equation (1) into equation (2) and solve for R x , then we get formula (3).

[0108] R x =(V i / V2-1) ×R9 (3)

[0109] Regarding this structure, if the resistance value of the resistor R9 is equal to the resistance value of the electrode R x The value of V2 input to the A / D converter 93 is extremely small compared to the impedance of the resistor R, and it is difficult to obtain the value of V2 with high accuracy due to rounding associated with digitization. x The impedance needs to be connected with the resistor R xThe resistor R9 is of the same size. x The impedance of the resistor R9 is unknown, so sometimes the resistance value of the connected resistor R x The impedance of resistor R9 is very different from that of resistor R x If the impedance is greatly different, the resistance R cannot be measured with high accuracy. x .

[0110] In particular, the impedance of a glass electrode typically ranges from tens of MΩ to several GΩ, and resistors with this high resistance are generally expensive. Therefore, it is practically difficult to employ an impedance measurement circuit 90 including resistor R9, which has a resistance of several tens of MΩ to several GΩ, as a module within a pH measurement device. Consequently, to measure the impedance of a glass electrode, a high insulation resistance meter is typically used for each pH measurement device, resulting in time-consuming maintenance.

[0111] Furthermore, the impedance measurement circuit 90 according to the comparative example needs to connect the resistor R9 via the jumper 91. Therefore, the management of the jumper 91 is complicated.

[0112] Thus, the impedance measuring circuit 90 according to the comparative example can measure the impedance of the electrode R to be measured simply and accurately. x There is room for improvement in terms of the impedance of the measured electrode. As a result, it is difficult to reliably perform maintenance on a system with multiple pH measuring devices. For example, it is difficult to x The change in impedance can reliably detect the degradation of the electrode Rx and take appropriate measures.

[0113] <Implementation Method>

[0114] The present invention describes a configuration example that enables simple and high-precision measurement of the impedance of an electrode being measured. An embodiment of the present invention is described below with reference to the accompanying drawings. In the drawings, components having identical structures or functions are denoted by the same reference numerals. In the description of this embodiment, overlapping descriptions of identical components may be omitted or simplified as appropriate.

[0115] Figure 2 1 is a block diagram showing a configuration example of a measuring device 10 according to one embodiment. The measuring device 10 measures the pH of a measuring solution as a sample. Figure 2 As shown, the measuring device 10 includes a control unit 11 , a storage unit 12 , a communication unit 13 , an input unit 14 , an output unit 15 , a measuring unit 16 , and a temperature detection unit 17 .

[0116] The control unit 11 includes one or more processors. In one embodiment, the "processor" is a general-purpose processor or a dedicated processor that performs specific processing, but is not limited to this. The control unit 11 is communicatively connected to each component of the measurement device 10 and controls the operation of the entire measurement device 10.

[0117] The storage unit 12 includes, for example, any storage module such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), a ROM (Read-Only Memory), and a RAM (Random Access Memory). The storage unit 12 can function as, for example, a main storage device, an auxiliary storage device, or a cache. The storage unit 12 stores any information used for the operation of the measurement device 10. For example, the storage unit 12 can store system programs, measurement data, temperature correction functions for each electrode type, and various information received by the communication unit 13. The storage unit 12 is not limited to being built into the measurement device 10 and can also be an external database or external storage module.

[0118] The communication unit 13 includes a server device 120 and a terminal device 130 (see Figure 13 The communication unit 13 may further include a communication control module for controlling communication with other devices and a storage module for storing communication data such as identification information required for communication with other devices.

[0119] The input unit 14 includes one or more input interfaces that receive input operations from the operator and obtain input information based on the operator's operations. Examples of the input unit 14 include physical keys, capacitance keys, a pointing device, and a touch screen integrated with the display of the output unit 15, but are not limited thereto.

[0120] The output unit 15 includes one or more output interfaces for outputting information to the operator and notifying the operator. For example, the output unit 15 may be a display that outputs information as an image or a speaker that outputs information as a voice, but is not limited to these. Such a display may be, for example, a liquid crystal panel display or an organic EL (electroluminescence) display. Furthermore, at least one of the input unit 14 and the output unit 15 may be integral with the measurement device 10 or provided separately.

[0121] The measuring unit 16 measures the pH of the measuring solution as a sample using the glass electrode 162. Figures 3 to 11 The measuring unit 16 will be described in detail.

[0122] The temperature detection unit 17 detects the temperature of the glass electrode 162 and the reference electrode 163 (see Figure 3 The temperature detecting unit 17 is composed of a thermistor or a thermocouple, but the principle of the temperature detecting unit 17 is arbitrary.

[0123] The functions of the measurement device 10 can be realized by executing the computer program (program) according to this embodiment by the processor included in the control unit 11. In other words, the functions of the measurement device 10 can be realized by software. The computer program causes the computer to execute the steps included in the operation of the measurement device 10, thereby causing the computer to realize the functions corresponding to the steps. In other words, the computer program is a program for causing the computer to function as the measurement device 10 according to this embodiment.

[0124] Part or all of the functions of the measurement device 10 may be implemented by a dedicated circuit included in the control unit 11. In other words, part or all of the functions of the measurement device 10 may be implemented by hardware. Furthermore, the measurement device 10 may be implemented by a single computer or by the coordinated operation of multiple computers.

[0125] Figure 3 Yes Figure 2 A schematic diagram of a structural example of the measuring unit 16. Figure 3 As shown, the measurement unit 16 includes a measurement circuit unit 161, a glass electrode 162, a reference electrode 163, and a liquid ground 164. The glass electrode 162, the reference electrode 163, and the liquid ground 164 are immersed in a measurement liquid S as a sample.

[0126] The measurement circuit unit 161 is connected to the glass electrode 162, the reference electrode 163, and the liquid ground 164. The measurement circuit unit 161 measures the pH of the measurement liquid S and the impedance of the glass electrode 162 and the reference electrode 163 based on the potentials of the glass electrode 162, the reference electrode 163, and the liquid ground 164.

[0127] The glass electrode 162 comprises a glass membrane 165, a buffer solution 166 contained within the glass membrane 165, and an electrode 167. The buffer solution 166 is a liquid with a predetermined pH. The pH of the buffer solution 166 is, for example, 7. When the glass membrane 165 containing the buffer solution 166 is immersed in the measurement liquid S, an electromotive force is generated on the surface of the glass membrane 165 that is proportional to the pH difference between the buffer solution 166 and the measurement liquid S. The electrode 167 is used to detect this electromotive force. The electrode 167 is immersed in the buffer solution 166.

[0128] The reference electrode 163 is an electrode that serves as a reference for detecting the electromotive force generated on the surface of the glass membrane 165. The reference electrode 163 includes a container 168 having a liquid confluence point 170, a KCl solution (e.g., 3.3 M KCl) 169 contained within the container 168, and an electrode 171. The liquid confluence point 170 can be made of, for example, porous ceramic. The KCl solution 169 flows out through the liquid confluence point 170 and comes into contact with the measuring liquid S. This allows the reference electrode 163 to maintain a constant reference potential with the measuring liquid S regardless of changes in the properties of the measuring liquid S, such as temperature, pressure, and flow rate. The electrode 171 is immersed in the KCl solution 169.

[0129] Typically, the electromotive force generated on the surface of the glass membrane 165 is measured based on the potentials of the electrodes 167 and 171, and the pH of the measurement liquid S corresponding to the electromotive force is measured. In contrast, the measurement unit 16 further includes a liquid ground 164 having an electrode 172 immersed in the measurement liquid S. The measurement unit 16 obtains the potential of the glass electrode 162 relative to the liquid ground 164 and the potential of the reference electrode 163 relative to the liquid ground 164, and measures the electromotive force generated on the surface of the glass membrane 165 based on the difference between the potentials. Therefore, the measurement device 10 according to this embodiment can measure the pH of the measurement liquid S with high accuracy.

[0130] Meanwhile, the measurement circuit unit 161 measures the impedance of the glass electrode 162 while the glass electrode 162 and the liquid ground 164 are immersed in the measurement liquid S. Specifically, the measurement circuit unit 161 measures the potential difference between the electrode 167 and the electrode 172 via the measurement liquid S, and measures the impedance of the glass electrode 162 based on the measured value of the potential difference. The measurement circuit unit 161 measures the impedance of the reference electrode 163 while the reference electrode 163 and the liquid ground 164 are immersed in the measurement liquid S. Specifically, the measurement circuit unit 161 measures the potential difference between the electrode 171 and the electrode 172 via the measurement liquid S, and measures the impedance of the reference electrode 163 based on the measured value of the potential difference.

[0131] The impedance of the glass electrode 162 ranges from tens of MΩ to several GΩ. In contrast, the impedance of the measuring liquid S is negligibly low. Therefore, the measuring unit 16 can measure the impedance of the glass electrode 162 via the measuring liquid S. Furthermore, the impedance of the reference electrode 163 ranges from several kΩ to several hundred kΩ. Therefore, the measuring device 10 can separately measure the impedance of the measuring liquid S, that is, the conductivity of the measuring liquid S, and subtract the impedance of the measuring liquid S from the impedance measured via the reference electrode 163 and the measuring liquid S to determine the impedance of the reference electrode 163.

[0132] Next, refer to Figure 4 and Figure 5, the pH measurement circuit 30 for measuring the pH of the measurement liquid S will be described. Figure 4 FIG. 1 is a diagram showing a configuration example of a pH measurement circuit 30 according to an embodiment. Figure 4 As shown, the pH measurement circuit 30 includes an operational amplifier 31 , an A / D converter 32 , a resistor R11 , and a resistor R12 . Figure 4 The pH measuring circuit 30 is shown as a non-inverting amplifier circuit. However, the pH measuring circuit 30 is not limited to a non-inverting amplifier circuit as long as it can convert a signal from a voltage source having an extremely high impedance into a voltage without attenuating the signal. For example, the pH measuring circuit 30 may be configured as an inverting amplifier circuit or a voltage follower circuit (see FIG. Figure 5 ).

[0133] The operational amplifier 31 has two input terminals (a non-inverting input terminal and an inverting input terminal) and an output terminal. A voltage E based on an electromotive force is applied to the non-inverting input terminal (+ input terminal) as the second input terminal. The terminal that outputs the potential of the electrode to be measured immersed in the measuring liquid as the sample is also called the "electromotive force terminal". The resistor R12 as a feedback resistor is connected between the inverting input terminal (- input terminal) as the first input terminal and the output terminal. The inverting input terminal is connected to the ground G via the resistor R11. The output terminal is connected to the A / D converter 32, which outputs the output of the operational amplifier 31 as a digital signal.

[0134] With this configuration, the output voltage Vout of the operational amplifier 31 is (1 + R12 / R11) E. That is, the amplification factor of the pH measurement circuit 30 is (1 + R12 / R11). Therefore, by dividing the output voltage Vout output as a digital signal from the A / D converter 32 by the amplification factor, the voltage E based on the electromotive force can be obtained. It is known that the voltage E based on the electromotive force and the pH have a constant relationship, so the pH can be obtained based on the voltage E. In this embodiment, the potential E1 of the glass electrode 162 relative to the liquid ground 164 and the potential E2 of the reference electrode 163 relative to the liquid ground 164 are obtained, and the pH is obtained based on the difference between the two (E1 - E2).

[0135] Figure 5 FIG. 4 shows a configuration example of a pH measurement circuit 30a configured as a voltage follower circuit. Figure 5 As described above, in the configuration example of the pH measurement circuit 30 a configured as a voltage follower circuit, the output terminal and the inverting input terminal (−input terminal) of the operational amplifier 31 are directly connected.

[0136] Next, refer to Figure 6 The impedance measurement circuit 40 for measuring the impedance of the electrode to be measured will be described. Figure 6FIG. 4 is a diagram showing a configuration example of an impedance measurement circuit 40 according to an embodiment. Figure 6 As shown, the impedance measurement circuit 40 includes an operational amplifier 41, an A / D converter 42, a feedback resistor (variable resistor) R p and the voltage source V i The impedance measurement circuit 40 measures the impedance of the electrode R to be measured having the first terminal and the second terminal. x impedance.

[0137] The operational amplifier 41 has two input terminals (a non-inverting input terminal and an inverting input terminal) and an output terminal. The non-inverting input terminal, which is the second input terminal, is connected to the ground G. The feedback resistor R p Connected between the inverting input terminal (the first input terminal) and the output terminal. Feedback resistor R p The operational amplifier 41 has a third terminal and a fourth terminal, the output terminal of the operational amplifier 41 is connected to the third terminal, and the inverting input terminal is connected to the fourth terminal. The output terminal is connected to the A / D converter 42, and the output of the operational amplifier 41 is output as a digital signal.

[0138] The impedance measurement circuit 40 applies a known voltage V to the liquid ground 164. i , measure the voltage V i The output voltage V of the operational amplifier 41 o , and thus the measured electrode R x More specifically, the amplifier 41 is used to calculate the unknown impedance of the current i x And get voltage V o , according to the voltage V o , feedback resistor R p and voltage V i For the electrode R x Therefore, a voltage V is applied. i The electrode (resistance R x ) is connected to the inverting input terminal of the operational amplifier 41.

[0139] Here, regarding the operational amplifier 41, a virtual short circuit is implemented so that the potential difference between the non-inverting input terminal and the inverting input terminal becomes 0 V, so the potential V - and the potential of the non-inverting input terminal V + =0. Therefore, the resistance R x The current i flowing toward the inverting input terminal of the operational amplifier 41 x Calculated by formula (4).

[0140] i x =(V i -V- ) / R x

[0141] =V i / R x (4)

[0142] On the other hand, according to the potential V o And the potential of the inverting input terminal V - , through formula (5) the feedback resistor R p The current i flowing from the output terminal to the inverting input terminal p Perform calculations.

[0143] i p =(V o -V - ) / R p

[0144] =V o / R p (5)

[0145] Here, no current is input or output to the inverting input terminal of the operational amplifier 41. Therefore, the sum of the currents is 0, which becomes i x +i p = 0. Therefore, formula (6) holds.

[0146] i x =-i p (6)

[0147] If equations (4) and (5) are substituted into equation (6), equation (7) holds.

[0148] V i / R x =-V o / R p (7)

[0149] If equation (7) is transformed, equation (8) becomes valid.

[0150] R x =- (V i / V o )R p (8)

[0151] Here, the negative sign of equation (8) is due to the current i p 、i x It is caused by the definition of the orientation and can be ignored.

[0152] Therefore, it is possible to use equation (8) based on the voltage V i 、V o And the feedback resistor Rp The impedance of the electrode being measured is calculated. Figure 6 The applied voltage V i It is represented by AC symbols, but can also be a DC voltage.

[0153] If equation (8) is transformed, equation (9) becomes valid.

[0154] V o =- (R p / R x )V i (9)

[0155] Therefore, if R p and R x The difference in size is significant, then the output voltage V o The impedance R cannot be measured accurately if the signal value is out of the range that the A / D converter 42 or other components can process. x Therefore, the measuring unit 16 sets the feedback resistor R p The resistance value is set close to R x The impedance R is measured with high accuracy. x .

[0156] About the feedback resistor R p By connecting switches and resistors in a binary tree structure, a higher resistance value can be achieved using a resistor with a lower resistance value. Figure 7 1 is a diagram showing a configuration example of an impedance measurement circuit 40 a according to an embodiment.

[0157] exist Figure 7 In the feedback resistor R p The circuit has resistors R1, R2, R4 to R7 and switches S1 to S4. Resistors R1 and R2 are connected in parallel. One end of each resistor R1 and R2 is connected to the inverting input terminal of the operational amplifier 41, and the other end is connected to the switch S1. One end of the switch S1 is connected to the switch S2. The switch S1 can switch the circuit element connected to the switch S2 between the resistor R1 and the resistor R2. By switching the switch S1, the resistor R1 or R2 is connected to the Figure 8 The resistor Rc corresponds to.

[0158] The resistors R4 to R7 are connected in series in this order. The end of the resistor R4 that is not connected to the resistor R5 is connected to the output terminal of the operational amplifier 41. The end of the resistor R7 that is not connected to the resistor R6 is connected to the ground G.

[0159] One end of switch S2 is connected to switch S1. Switch S2 can switch the circuit element connected to switch S1 between switch S4 and switch S3. Switch S4 can switch the circuit element connected to switch S2 between the two terminals of resistor R4. Switch S3 can switch the circuit element connected to switch S2 between the two terminals of resistor R6. In this way, by switching switches S2, S3, and S4, any one of the connection terminals between operational amplifier 41 and resistor R4, the connection terminal between resistors R4 and R5, the connection terminal between resistors R5 and R6, and the connection terminal between resistors R6 and R7 is directly electrically connected to switch S1. That is, according to the switching action of switches S2 to S4, except when switch S1 is directly connected to the output terminal of operational amplifier 41, the series of resistors R4 to R7 branches into two parts using the contacts between the resistors directly connected to switch S1 and acts as voltage divider resistors Ra and Rb. In addition, switches S1 to S4 are semiconductor or relay type switches, but can also be implemented by other means.

[0160] Feedback resistor R of impedance measurement circuit 40a p The resistance value of is determined by the resistance values ​​of the resistors Ra, Rb, and Rc, which are determined by the switching of the switches S1 to S4. Figure 8 The resistance values ​​of the voltage divider resistors Ra, Rb, and Rc and the feedback resistor R p The relationship between the resistance value and the Figure 8 Is to express Figure 7 FIG. 4 is a diagram showing a configuration example of a circuit 40b equivalent to the impedance measuring circuit 40a.

[0161] exist Figure 8 In FIG. 4 , the output terminal of operational amplifier 41 is connected to one end of resistor Rb. The other end of resistor Rb is connected to one end of resistor Ra and to one end of resistor Rc. The other end of resistor Rc is connected to the inverting input terminal of operational amplifier 41, forming a negative feedback circuit for operational amplifier 41. The other end of resistor Ra is connected to ground G.

[0162] like Figure 8 As shown, the potential of the output terminal of the operational amplifier 41 is V o The potential of the inverting input terminal of the operational amplifier 41 is V - .exist Figure 8 In such a negative feedback circuit, the feedback signal follows the input signal. As mentioned above, the input signal and the feedback signal are in a so-called virtual short-circuit state, which is like a short circuit. In the virtual short-circuit state, the potential V -The potential difference from the potential of the non-inverting input terminal (which becomes 0 due to grounding) is 0, so it becomes V - =0.

[0163] In the virtual short-circuit state, the current input and output of the inverting input terminal of the operational amplifier 41 is 0. Therefore, the current I3 flowing through the resistor Rc toward the inverting input terminal side of the operational amplifier 41 is proportional to the resistance Rc of the electrode. x The current I flowing in in Equal (I in = I3). Therefore, the potential V1 of the connection terminal between the resistor Rb and the resistor Ra is Rc×I3=Rc×I in .

[0164] The potential V at the output terminal of the operational amplifier 41 o The current I2 flowing from the output terminal to the resistor Rb, the resistor Rb, and the aforementioned V1 are expressed by the equation Vo=V1+Rb×I2. As mentioned above, V1=Rc×I in This relationship is consistent with I2=I1+I3=I1+I in This relationship holds, so V o =Rc×I in +Rb×(I1+I in ) holds. Also, the relationship I1=V1 / Ra holds. As mentioned above, V1=Rc×I in Since this relationship holds, the following formula (10) holds.

[0165] V o =Rc×I in +Rb×(V1 / Ra+I in )

[0166] =Rc×I in +Rb×(Rc / Ra×I in +I in )

[0167] =I in ×(Rc×(1+Rb / Ra)+Rb) (10)

[0168] Here, if equation (7) is transformed, equation (11) is established.

[0169] R p =- (V o / V i )R x (11)

[0170] If equation (10) is substituted into equation (11), the following equation (12) is established.

[0171] R p =- (I in R y / V i )R x (12)

[0172] Among them, R y It is given by formula (13).

[0173] R y =Rc×(1+Rb / Ra)+Rb (13)

[0174] Here, I in =-I x In addition, equation (14) holds true through equation (4).

[0175] I in =-V i / R x (14)

[0176] If equation (14) is substituted into equation (12), equation (15) can be obtained.

[0177] R p =R y

[0178] =Rc×(1+Rb / Ra)+Rb (15)

[0179] Here, the resistor R1 is set to 10MΩ, the resistor R2 is set to 1kΩ, the resistor R4 is set to 900Ω, the resistor R5 is set to 90Ω, the resistor R6 is set to 9Ω, and the resistor R7 is set to 1Ω. In this case, the connection relationship of the switches S1 to S4 and the relationship between the resistance values ​​of Ra, Rb, Rc, and Rp are given by Figure 9 express. Figure 9 The feedback resistance R corresponding to the switching content of the switch p Figure 1 shows examples of resistance values.

[0180] For example, when the range is "1," switch S1 is set to "B," connecting switch S2 and resistor R2 (=1 kΩ) via switch S1, resulting in Rc = 1,000 Ω. Switch S2 is set to "A." Switch S4 is set to "A." Therefore, regardless of the setting of switch S3, Ra of the voltage divider resistor is 1,000 Ω (= R4 + R5 + R6 + R7), and Rb is 0 Ω. Therefore, the feedback resistor R p is 1,000Ω.

[0181] For example, when the range is "7," switch S1 is set to "A," and thus switch S2 and resistor R1 (=10MΩ) are connected via switch S1, resulting in Rc = 10,000,000Ω. Switch S2 is set to "B." Switch S3 is set to "A." Therefore, regardless of the setting of switch S4, Ra of the voltage divider resistor is 10Ω (= R6 + R7), and Rb is 990Ω (= R4 + R5). Therefore, the feedback resistor R p 1,000,000,990Ω.

[0182] like Figure 9 As shown, the feedback resistor R p The resistance value can be switched to 1k, 10k, 100k, 1M, 10M, 100M, 1G and 10G in 8 levels by switching switches S1, S2, S3 and S4. p The only 10MΩ resistor included in is resistor R1. The only four switches are S1, S2, S3, and S4. Therefore, the feedback resistor R p A small number of high resistors and switches can achieve a minimum resistance to a maximum resistance of 10 7 times larger dynamic range. In addition, the feedback resistor R p , there are no parallel connected switches that can be energized at the same time, so the leakage current generated in the switches will not be superimposed and become a large error current. For example, switch S2 is used to switch switches S3 and S4. Therefore, switches S3 and S4 will not be energized at the same time and cause leakage current to superimpose. Therefore, according to the feedback resistor R p , a variable resistor with a large dynamic range, low cost and simple structure is realized. The impedance measurement circuit 40 has such a feedback resistor R p , thereby being able to measure the impedance of the glass electrode 162 and the reference electrode 163 with high precision within a larger dynamic range.

[0183] In addition, the feedback resistor R p The structure is not limited to reference Figure 7 The structure of the description. For example, Figure 7 The feedback resistor R p Either of the two resistors R1 and R2 can be selected as the resistor Rc, but a specific resistance can be predetermined as the resistor Rc, or the resistor Rc can be selected from three or more resistors. Figure 7 The feedback resistor R p The four resistors R4 to R7 connected in series are divided into voltage dividing resistors Ra and Rb by switches S2 to S4 , but the number of resistors may be less than or equal to three, or may be greater than or equal to five. Figure 7 The feedback resistor Rp In order to realize the voltage dividing resistors Ra and Rb, three switches S2 to S4 are connected in a binary tree structure, but the number of switches can be less than or equal to 2 or greater than or equal to 4. In addition, the feedback resistor R p For example, the amplifier circuit described in Japanese Patent Application Laid-Open No. 2022-002384 (e.g., Figure 1 、 3 , 5, and 8 have a structure including a feedback resistor.

[0184] The measurement circuit unit 161 may have a reference electrode for each of the glass electrode 162 and the reference electrode 163. Figure 4 and Figure 5 The pH measuring circuits 30 and 30a described above and the reference Figures 6 to 9 Alternatively, the measurement circuit unit 161 may include a mixing circuit 50 capable of switching between the pH measurement circuit 30 and the impedance measurement circuit 40 for each of the glass electrode 162 and the reference electrode 163 using a switch.

[0185] Figure 10 FIG. 1 is a diagram showing a configuration example of a hybrid circuit 50 according to an embodiment of the present invention. Figure 10 Thus, the mixing circuit 50 includes switches 51 and 52, an operational amplifier 53, an A / D converter 54, a resistor R11, a feedback resistor (variable resistor) R p and the voltage source V i .

[0186] like Figure 10 As shown, the switch 51 is connected to the non-inverting input terminal of the second input terminal of the operational amplifier 53. The switch 51 as the second switch can switch the circuit element connected to the non-inverting input terminal between the ground G (set to "B") and the electrode (set to "A") to which the voltage E based on the electromotive force is applied. The feedback resistor R p The switch 52 is connected between the inverting input terminal and the output terminal of the operational amplifier 53, which is the first input terminal. The output terminal is connected to the A / D converter 54, and the output of the operational amplifier 53 is output as a digital signal. The switch 52 is also connected to the inverting input terminal of the operational amplifier 53. The switch 52, which is the first switch, can be switched when a known voltage V is applied to the liquid ground 164. i With impedance R x The circuit element connected to the inverting input terminal is switched between the electrode to be measured (set to "B") and resistor R11 (set to "A"), the other end of which is connected to ground G. Switches 51 and 52 are semiconductor or relay-type switches, but may also be implemented in other ways.

[0187] When switches 51 and 52 are both set to "A", the mixing circuit 50 and Figure 4 The pH measurement circuit 30 shown is equivalent to the one shown in FIG. 3 . When switches 51 and 52 are both set to “B”, the mixing circuit 50 and Figure 6 The impedance measurement circuit 40 shown is equivalent. The measurement circuit unit 161 includes such a mixing circuit 50 for each of the glass electrode 162 and the reference electrode 163, and can measure the potential and impedance based on pH of each electrode.

[0188] also, Figure 10 The structural example shown can Figure 6 The impedance measuring circuit 40 is switched to Figure 4 The pH measuring circuit 30 and the mixing circuit 50 can be replaced Figure 4 The pH measuring circuit 30 is switched to Figure 5 In this case, the switch 52 can be formed to switch the inverting input terminal of the operational amplifier 53 between a state connected to the electrode to be measured (set to "B") and a state not connected to other circuit elements (set to "A"). Feedback resistor R p The output terminal and the inverting input terminal of the operational amplifier 53 may be short-circuited. Furthermore, the mixing circuit 50 may be configured so that the impedance measurement circuit 40 is switched to a pH measurement circuit configured as an inverting amplifier circuit.

[0189] Figure 11 Yes Figure 3 FIG. 161 is a diagram showing an example of a structure of a measuring circuit unit 161. Figure 11 As shown, the measurement circuit section 161 includes mixing circuits 50a, 50b and a liquid grounding circuit 60. The mixing circuit 50a is connected to the glass electrode 162. The mixing circuit 50b is connected to the reference electrode 163. The mixing circuits 50a and 50b each have a reference electrode 164. Figure 10 The liquid grounding circuit 60 is connected to the liquid grounding member 164. The liquid grounding circuit 60 has a switch 61. The switch 61 can be connected to the grounding member G (set to "A") and the voltage source V i (set to "B") switches the circuit element connected to the electrode 172 of the liquid ground 164. The switch 61 is a semiconductor type or relay type switch, but can also be implemented in other ways. Figure 11 The applied voltage V i It is represented by AC symbols, but can also be a DC voltage.

[0190] When measuring the pH of the measurement liquid S, the measurement circuit unit 161 sets switches 51 (51a, 51b), 52 (52a, 52b), and 61 to "A." When measuring the impedance of the glass electrode 162 and the reference electrode 163, the measurement circuit unit 161 sets switches 51, 52, and 61 to "B." The measurement device 10, equipped with this measurement circuit unit 161, can measure the pH of the measurement liquid S and the impedance of the electrodes being measured simply and accurately with a compact structure.

[0191] It is known that the impedance of an electrode to be measured changes depending on the temperature of the electrode. Figure 12 71 is a graph schematically showing the relationship between the temperature and impedance of the electrode being measured. Figure 12 In the graph 71, the horizontal axis represents the temperature of the electrode. The vertical axis represents the impedance of the electrode based on a logarithmic axis. Graph 71 shows the relationship between the temperature and impedance of the electrode. Graph 71 shows that the impedance of the electrode decreases sharply as the temperature increases. Therefore, when measuring the impedance of the glass electrode 162 and the reference electrode 163, the measuring device 10 corrects the measured impedance value based on the temperature of the electrode measured by the temperature detection unit 17. Specifically, the measuring device 10 can obtain a temperature correction function that represents the correspondence between temperature and impedance according to the type of electrode, and use the temperature correction function to correct the measured impedance value. By performing this temperature correction, the measuring device 10 can measure the impedance of the measured electrode with high accuracy.

[0192] The measurement device 10 can transmit the measurement result to the server device 120 via the network N in the measurement system 1. The server device 120 can manage the measured electrodes R for each measurement device 10. x impedance and electrode degradation, etc. Figure 13 This measurement system 1 will be described. Figure 13 It is a diagram showing a configuration example of a measurement system 1 according to one embodiment.

[0193] like Figure 13 As shown, measurement system 1 includes a measurement device 10, a server device 120, and a terminal device 130. Measurement device 10, server device 120, and terminal device 130 are connected to each other in a communicative manner via an arbitrary network N including the Internet, a local area network, or a combination thereof. The number of measurement devices 10, server device 20, and terminal device 130 is arbitrary and can be greater than or equal to two.

[0194] The server device 120 manages the measurement results of the pH of the measurement solution S and the impedance of the measured electrode obtained by the measurement device 10, as well as the electrode degradation status. The server device 120 is constituted by any computer such as a WS (WorkStation) or a PC (Personal Computer).

[0195] The terminal device 130 accesses the server device 120 to obtain the measurement results and electrode degradation status managed by the measurement device 10. The terminal device 130 can be operated by a user including a maintenance operator of the measurement device 10. The terminal device 130 is constituted by any computer such as a PC, tablet terminal, or smartphone.

[0196] Figure 14 Yes Figure 13 1 is a block diagram showing an example of the configuration of a server device 120. The server device 120 includes a control unit 121, a storage unit 122, and a communication unit 123. The configurations of the control unit 121, storage unit 122, and communication unit 123 are similar to those of the control unit 11, storage unit 12, and communication unit 13 of the measurement device 10, and therefore detailed descriptions thereof will be omitted.

[0197] Figure 15 Yes Figure 13 1 is a block diagram showing an example configuration of a terminal device 130. The terminal device 130 includes a control unit 131, a storage unit 132, a communication unit 133, an input unit 134, and an output unit 135. The configurations of the control unit 131, storage unit 132, communication unit 133, input unit 134, and output unit 135 are similar to those of the control unit 11, storage unit 12, communication unit 13, input unit 14, and output unit 15 of the measurement device 10, and therefore detailed descriptions thereof will be omitted.

[0198] Figure 16 Yes Figure 13 Flowchart of an example of the operation of the measuring device 10. Figure 16 The following is a flow chart showing the process of measuring the impedance of the electrode to be measured by the measuring device 10. Figure 16 The operation of the measuring device 10 described above may correspond to one of the measuring methods of the measuring device 10 . Figure 16 The actions of each step are performed based on the control of the control unit 11 of the measuring device 10, but Figure 16 All or part of the steps may also be executed by the server device 120 or the terminal device 130.

[0199] Next, the measuring device 10 has Figure 11 The structure shown in FIG. 5 and the feedback resistor R of the hybrid circuit 50a and 50b are p have Figure 7 and Figure 9In the following, an example of the operation when the impedance of the glass electrode 162 is measured will be described, but the operation when the impedance of the reference electrode 163 is measured is also the same.

[0200] In step S11, the control unit 11 sets the impedance measurement mode to measure the impedance of the electrode to be measured. Specifically, the control unit 11 sets Figure 11 The switches 51a, 51b, and 61 are respectively set to "B".

[0201] In step S12, the control unit 11 sets the feedback resistor R p The resistance value is set to the minimum range. For example, in the feedback resistor R p The range of resistance values ​​is determined by Figure 9 In the case shown, the feedback resistor R of the mixing circuit 50a p , set switches S1 to S4 to the setting values ​​corresponding to the range (Range) "1". Specifically, set switch S1 to "B", switch S2 to "A", and switch S4 to "A". The setting of switch S3 is arbitrary.

[0202] In step S13, the control unit 11 determines the potential V of the output terminal of the operational amplifier 53. o Is it within a predetermined range (for example, the measurement range of the A / D converter 54)? o If it is within the predetermined range (YES in step S13), the control unit 11 proceeds to step S15. If it is not (NO in step S13), the control unit 11 proceeds to step S14. p The resistance value is set to the minimum range and then gradually expanded, but it can also be set to the maximum range first and then gradually reduced. p The resistance value is changed and the potential V o When the feedback resistor R p The order of changing the resistance value is not particularly limited.

[0203] In step S14, the control unit 11 sets the feedback resistor R p For example, the feedback resistor R p The resistance value range is set to Figure 9 If the range is "1", the control unit 11 sets the range to "2". Then, the control unit 11 again advances the process to step S13. o The control unit 11 repeats the processing of steps S13 and S14 until the potential V falls within the predetermined range, thereby preventing the potential V from oThe value of is rounded off in the A / D converter 54, and the impedance of the electrode to be measured can be obtained with high accuracy.

[0204] In step S15, the control unit 11 controls the voltage V o The impedance R of the electrode to be measured is obtained x Specifically, based on the potential V o And the known V i 、R p , and obtain the impedance R through formula (8) x In this embodiment, refer to Figure 17 In the processing described later, the impedance correction based on the temperature of the electrode to be measured is executed. However, the control unit 11 may also perform the impedance correction based on the temperature in step S15.

[0205] In step S16, the control unit 11 determines whether the impedance measurement value obtained in step S15 has been stored. For example, if the user has instructed to save the measurement value, the control unit 11 may determine that the measurement value has been stored in the storage unit 12. If the measurement value has been stored (YES in step S16), the control unit 11 proceeds to step S17; if not (NO in step S16), the control unit 11 proceeds to step S18.

[0206] In step S17, the control unit 11 stores the impedance measurement value obtained in step S15 in the storage unit 12. In addition, the control unit 11 may transmit the measurement value to the server device 120 or the terminal device 130 via the communication unit 13 and store the measurement value in the server device 120 or the terminal device 130.

[0207] In step S18, the control unit 11 determines whether measurement is continuing. For example, if the user has instructed to end impedance measurement, the control unit 11 may determine that measurement is not continuing. If measurement is continuing (YES in step S18), the control unit 11 returns the process to step S15. If not (NO in step S18), the process proceeds to step S19.

[0208] In step S19, the control unit 11 sets the pH measurement mode to measure the pH of the measurement liquid S. Specifically, the control unit 11 sets Figure 11 The switches 51a, 51b, and 61 are set to "A" respectively. If the process of step S19 is completed, the control unit 11 ends. Figure 16 Flowchart processing.

[0209] Figure 17 Yes Figure 13 Flowchart of an example of the operation of the measuring device 10. Figure 17 Indicates the temperature of the electrode being measured. Figure 16 The flowchart of the process of correcting the impedance measurement value obtained. Figure 17 The operation of the measuring device 10 described above may correspond to one of the measuring methods of the measuring device 10 . Figure 17 The operations of each step are executed based on the control of the control unit 11 of the measuring device 10, but can also be executed by the server device 120 or the terminal device 130. Figure 17 Next, an example of the operation in the case of correcting the measured value of the impedance of the glass electrode 162 will be described, but the operation for the reference electrode 163 is also the same.

[0210] In step S21 , the control unit 11 acquires the measured value of the impedance of the electrode to be measured before temperature correction.

[0211] In step S22 , the control unit 11 acquires a temperature correction function according to the type of the electrode to be measured. Specifically, the control unit 11 acquires a temperature correction function according to the type of the glass electrode 162 used in the measurement device 10 from the storage unit 12 or the server device 120 .

[0212] In step S23, the control unit 11 corrects the measured impedance value using the temperature correction function acquired in step S22. Specifically, the control unit 11 corrects the measured value based on the temperature of the glass electrode 162 detected by the temperature detection unit 17 and the temperature correction function acquired in step S22. For example, the control unit 11 may correct the measured impedance value to a value corresponding to a reference temperature (e.g., 25 degrees Celsius).

[0213] In step S24, the control unit 11 records the impedance measurement value after correction in step S23. Specifically, the control unit 11 saves the corrected measurement value in the storage unit 12. On this basis, the control unit 11 can send the corrected measurement value to the server device 120 or the terminal device 130 via the communication unit 13, and store the corrected measurement value in the server device 120 or the terminal device 130. If the processing of step S24 is completed, the control unit 11 ends. Figure 17 Flowchart processing.

[0214] Figure 18 Yes Figure 13 Flowchart of an example of the operation of the measuring device 10. Figure 18 Indicates based on Figure 16 The impedance measurement value obtained by the flowchart or based on Figure 17 The process flow for obtaining the degree of electrode degradation by correcting the measured impedance value is shown in the flowchart. Figure 18 The operation of the measuring device 10 described above may correspond to one of the measuring methods of the measuring device 10 . Figure 18The operations of each step are executed based on the control of the control unit 11 of the measuring device 10, but can also be executed by the server device 120 or the terminal device 130. Figure 18 Next, an example of operation in the case of obtaining the degree of degradation of the glass electrode 162 will be described. The same applies to the operation of the reference electrode 163.

[0215] In step S31, the control unit 11 obtains Figure 16 obtained through or based on the flowchart of Figure 17 The flowchart corrects the measured value of the impedance of the glass electrode 162.

[0216] In step S32, the control unit 11 obtains the degree of degradation of the glass electrode 162 based on the measured value obtained in step S31. Generally, it is known that the impedance of the electrode being measured increases as degradation progresses. Therefore, the control unit 11 can obtain a relationship between the impedance value and an index representing the degree of degradation, and use this relationship to obtain the degree of degradation of the glass electrode 162. The impedance value in the relationship can be the impedance at a reference temperature corresponding to the type of electrode being measured. In this case, in step S31, it is preferable to obtain the impedance value based on the reference temperature. Figure 17 The measured impedance value is obtained by correcting it to a value corresponding to the reference temperature according to the flowchart. The control unit 11 can obtain the relationship equation pre-stored in the storage unit 12 or receive it from the server device 120 via the communication unit 13. The degree of electrode degradation can be represented by a numerical value or by several levels of degree.

[0217] In step S33, the control unit 11 notifies the user of the degree of degradation obtained in step S32. For example, the degree of degradation can be displayed on the display of the output unit 15. Specifically, the control unit 11 can cause the output unit 15 to display a graph showing the change in impedance or degree of degradation over time measured at multiple time points, visually showing the degree of degradation development. The control unit 11 can perform regression analysis on the graph showing the change in degree of degradation over time, predict the period when the degree of degradation reaches a predetermined threshold, and notify the predicted period as the replacement period of the electrode. The control unit 11 can send the degree of degradation and the replacement period of the electrode to the terminal device 130, and display it on the display of the output unit 135. If the processing of step S33 is ended, the control unit 11 ends. Figure 18 Flowchart processing.

[0218] As described above, the measuring device 10 includes the measuring unit 16 for measuring the impedance of the electrode to be measured and the control unit 11. The measuring unit 16 includes an operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal; and a feedback resistor R as a variable resistor. p, which is connected to the output terminal and the inverting input terminal of the operational amplifier. The control unit 11 is connected to the inverting input terminal and the feedback resistor R p With the electrode R being measured x When one end of the electrode is connected to the other end of the electrode, the potential of the output terminal of the operational amplifier and the feedback resistor R p The resistance value of the electrode to be measured is obtained by x The measured value of the impedance.

[0219] Therefore, according to the measuring device 10, it is possible to x The impedance is adjusted by measuring the feedback resistor R p Therefore, the measuring device 10 can easily and accurately measure the resistance value of the electrode R to be measured. x In addition, according to the measuring device 10, the use of external components such as the jumper 91 can be omitted. For example, even if the measured electrode R x When the impedance of the measuring device 10 is extremely large, the feedback resistor R is increased according to the impedance. p The resistance value of the electrode to be measured can be measured with high accuracy. x impedance.

[0220] In addition, the measuring device 10 is used as a feedback resistor R p And has Figure 8 Such voltage dividing resistors Ra, Rb and feedback resistor Rc have the following characteristics: Figure 7 Thus, the measurement device 10 can realize the feedback resistor R as a variable resistor with low cost and wide dynamic range without using expensive high resistors. p .

[0221] In addition, the measuring device 10 uses the electrode R to be measured with high precision. x The measured impedance value of the electrode R is accurately detected. x The degree of degradation of the electrode R can be notified to the user. x The degree of deterioration and replacement period, etc.

[0222] In addition, the measuring device 10 uses the output unit 15, the server device 120, the terminal device 130, etc. to transmit the measured electrode R x Therefore, even when a plurality of measuring devices 10 are installed, the user can appropriately manage each measuring device 10 without looking around at the measuring devices 10 .

[0223] The measuring device 10 can switch between a pH measurement mode for measuring the pH of the measuring solution S and an impedance measurement mode for measuring the impedance of the electrode to be measured by simply switching the switches 51 ( 51 a , 51 b ), 52 ( 52 a , 52 b ), and 61 .

[0224] In addition, the measuring device 10 is based on the measured electrode R x The temperature of the electrode R x The impedance of the electrode R can be measured with higher accuracy. x impedance.

[0225] In addition, the measuring device 10 can pass the output of the operational amplifier 53 or the output of the A / D converter 54 through a lock-in amplifier (synchronous detection) or a bandpass filter, etc., to extract the signal corresponding to the applied voltage V i The frequency corresponding signal (with the output terminal potential V o According to this configuration, even if the output of the operational amplifier 53 contains noise components due to, for example, low purity of the measurement liquid S, the impedance of the electrode to be measured can be measured with high accuracy.

[0226] Furthermore, the measuring device 10 may also include a structure for measuring the conductivity (impedance) of the measuring liquid S. For example, the measuring device 10 may include another liquid ground in addition to the liquid ground 164, and determine the conductivity of the measuring liquid S by applying a voltage between the two liquid grounds. This allows the measuring device 10 to measure not only the pH but also the conductivity of the measuring liquid S. Furthermore, in impedance measurement mode, the measuring device 10 eliminates the influence of the conductivity of the measuring liquid S and can more accurately measure the impedance of the electrode being measured.

[0227] Furthermore, if a correlation is detected between the fluctuation in the impedance value of the glass electrode 162 and the fluctuation in the pH value of the measurement liquid S, the measurement device 10 can correct the pH value by referring to the fluctuation in the impedance value of the glass electrode 162. Specifically, the measurement device 10 can correct the pH value obtained based on the potential difference between the glass electrode 162 and the reference electrode 163 based on the correlation between the fluctuation in the impedance value of the glass electrode 162 and the fluctuation in the measured pH value of the measurement liquid S. With this configuration, even if the glass electrode 162 deteriorates to some extent, the measurement device 10 can still measure the pH value of the measurement liquid S with the highest possible accuracy, regardless of the degree of degradation.

[0228] The present invention is not limited to the above-described embodiments. For example, multiple modules described in the block diagrams may be integrated, or a single module may be segmented. Instead of being executed in chronological order as described, the multiple steps described in the flowcharts may be executed in parallel or in a different order, depending on the processing capabilities of the devices executing each step or as needed. Other modifications are possible without departing from the scope of the present invention.

[0229] Description of the label

[0230] 1 Measurement system

[0231] 10. Measurement device

[0232] 11 Control Unit

[0233] 12 Storage

[0234] 13 Ministry of Communications

[0235] 14 Input section

[0236] 15 Output

[0237] 16 Measurement Department

[0238] 17 Temperature detection unit

[0239] 30 pH measurement circuit

[0240] 31 Operational Amplifier

[0241] 32 A / D converters

[0242] 40 Impedance Measurement Circuit

[0243] 41 Operational Amplifier

[0244] 42 A / D converter

[0245] 50 Hybrid Circuit

[0246] 51, 52 switches

[0247] 53 Operational Amplifier

[0248] 54 A / D converter

[0249] 60 Liquid Grounding Circuit

[0250] 61 Switch

[0251] 71 Graph

[0252] 90 Impedance Measurement Circuit

[0253] 91 jumper wires

[0254] 92 Operational Amplifier

[0255] 93 A / D converter

[0256] 120 Server Device

[0257] 121 Control Department

[0258] 122 Storage Department

[0259] 123 Ministry of Communications

[0260] 130 Terminal Device

[0261] 131 Control Department

[0262] 132 Storage Department

[0263] 133 Ministry of Communications

[0264] 134 Input

[0265] 135 Output

[0266] 161 Measurement circuit unit

[0267] 162 glass electrode

[0268] 163 contrast electrode

[0269] 164 Liquid Grounding Parts

[0270] 165 glass film

[0271] 166 buffer

[0272] 167 electrodes

[0273] 168 containers

[0274] 169 KCl solution

[0275] 170 Liquid Confluence Point

[0276] 171 Electrode

[0277] 172 electrodes

[0278] G Grounding piece

[0279] N Network

[0280] Resistors R1, R2, R4-R7

[0281] R9, R11, R12 resistors

[0282] Ra, Rb, Rc resistance

[0283] R p Feedback resistor

[0284] R x Electrode being measured

[0285] S assay solution

[0286] S1-S4 switches

[0287] V i Applied voltage

Claims

1. A measuring device, wherein: The measuring device comprises: a measuring unit that measures the impedance of a measured electrode having a first terminal and a second terminal; as well as Control Department, The measuring unit includes: an operational amplifier having a first input terminal, a second input terminal, and an output terminal; as well as a feedback resistor which is a variable resistor having a third terminal connected to the output terminal and a fourth terminal connected to the first input terminal, The control unit acquires a measurement value of the impedance of the electrode to be measured based on the voltage applied to the second terminal, the potential of the output terminal, and the resistance value of the feedback resistor in a state where the first input terminal is connected to the first terminal.

2. The measuring device according to claim 1, wherein The measuring device further comprises: a first switch configured to switch the terminals connected to the first input terminal and the fourth terminal between a state connected to the first terminal and a state not connected to the first terminal; as well as a second switch for switching the terminal connected to the second input terminal between a state of being connected to an electromotive force terminal and a state of not being connected to the electromotive force terminal, the electromotive force terminal outputting the potential of the electrode to be measured immersed in a measuring liquid as a sample; The control unit acquires the measured value of the impedance of the electrode to be measured in a state in which the first switch connects the first input terminal and the fourth terminal to the first terminal and the second switch does not connect the second input terminal to the electromotive force terminal.

3. The measuring device according to claim 2, wherein The control unit acquires the potential of the electrode to be measured in a state where the first switch does not connect the first input terminal and the fourth terminal to the first terminal and the second switch connects the second input terminal to the electromotive force terminal. The pH of the measurement liquid is acquired based on the acquired potential of the electrode to be measured.

4. The measuring device according to any one of claims 1 to 3, wherein The control unit obtains the temperature of the electrode to be measured, The measured value of the impedance of the electrode to be measured is corrected based on the acquired temperature.

5. The measuring device according to claim 4, wherein The control unit acquires a temperature correction function indicating a relationship between temperature and impedance according to the type of the electrode to be measured. The measured value of the impedance of the electrode to be measured is corrected using the temperature correction function.

6. The measuring device according to any one of claims 1 to 5, wherein The measuring device further includes a liquid grounding circuit for applying a voltage to the glass electrode and the reference electrode via the measuring liquid. The measuring unit includes: a first measuring unit for measuring the impedance of a glass electrode as the electrode to be measured in a state where a voltage is applied by the liquid grounding circuit; and a second measuring unit for measuring the impedance of a reference electrode serving as the electrode to be measured while a voltage is applied by the liquid grounding circuit.

7. The measuring device according to claim 6, wherein The control unit acquires the pH of the measurement liquid based on a potential difference between the glass electrode immersed in the measurement liquid and the reference electrode in a state where no voltage is applied by the liquid ground circuit.

8. The measuring device according to claim 7, wherein The control unit corrects the pH of the measurement liquid obtained based on the potential difference between the glass electrode immersed in the measurement liquid and the reference electrode based on the correlation between the fluctuation of the measured value of the impedance of the glass electrode and the fluctuation of the measured value of the pH of the measurement liquid.

9. The measuring device according to any one of claims 1 to 8, wherein The measuring unit includes a resistor capable of switching a resistance value within a plurality of ranges as the feedback resistor.

10. The measuring device according to any one of claims 1 to 9, wherein The control unit acquires the degree of degradation of the electrode to be measured based on the measured value of the impedance of the electrode to be measured, The acquired degree of degradation is output.

11. The measuring device according to claim 10, wherein The control unit predicts a replacement time of the electrode to be measured based on the degree of degradation acquired at a plurality of time points, The predicted replacement time of the electrode to be measured is output.

12. A measuring method, which is a measuring method using a measuring device. The measuring device comprises: a measuring unit that measures the impedance of a measured electrode having a first terminal and a second terminal; as well as Control Department, In the measuring method, The measuring unit includes: an operational amplifier having a first input terminal, a second input terminal, and an output terminal; as well as a feedback resistor which is a variable resistor having a third terminal connected to the output terminal and a fourth terminal connected to the first input terminal, The measurement method includes the following steps: the control unit obtains a measurement value of the impedance of the electrode to be measured based on the voltage applied to the second terminal, the potential of the output terminal, and the resistance value of the feedback resistor when the first input terminal is connected to the first terminal.

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