Measuring device and measurement method

Abstract

To measure impedance of an electrode more easily and precisely by a pH measuring device using a glass electrode.SOLUTION: A measuring device (10) comprises a measurement section (161) for measuring impedance of a measured electrode having a first terminal and a second terminal, and a control section (11). The measurement section (161) has an operational amplifier having a first input terminal and a second input terminal, and an output terminal, and a feedback resistor that is a variable resistor having a third terminal connected to the output terminal and a fourth terminal connected to the first input terminal, and the control section (11) acquires a measurement value of impedance of the measured electrode on the basis of voltage applied to the second terminal, the potential of the output terminal, and the resistance value of the feedback resistor in a state in which the first input terminal is connected to the first terminal.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a measurement device and a measurement method. [Background technology]

[0002] pH (hydrogen ion exponent) is a physical quantity that indicates the degree of acidity or alkalinity of a solution. pH is defined as the negative common logarithm of the hydrogen ion concentration in a solution.

[0003] The glass electrode pH measurement method is a well-known method for measuring the pH of a solution. When two different solutions are present on either side of a special glass membrane, an electromotive force proportional to the difference in pH between the two solutions is generated in the glass membrane. The glass electrode pH measurement method measures the potential difference between the glass electrode and a reference electrode due to this electromotive force, thereby measuring the pH of the solution.

[0004] In a pH measurement device using a glass electrode, the impedance value of the electrode changes due to deterioration of the electrode, resulting in a decrease in the accuracy of pH measurement. Patent Document 1 describes a technique for calibrating pH measurement values ​​based on the measured value of the electrode impedance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2013-019804 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the conventional configuration leaves room for improvement in terms of measuring the impedance of the electrodes easily and with high accuracy.

[0007] Therefore, an object of the present disclosure is to enable easier and more accurate measurement of electrode impedance in a pH measurement device using a glass electrode. [Means for solving the problem]

[0008] In some embodiments, the measurement device comprises: (1) a measurement unit for measuring the impedance of a measurement target electrode having a first terminal and a second terminal; A control unit; Equipped with The measurement unit an operational amplifier having a first input terminal, a second input terminal, and an output terminal; a feedback resistor that is a variable resistor having a third terminal connected to the output terminal and a fourth terminal connected to the first input terminal; and When the first input terminal is connected to the first terminal, the control unit obtains a measured value of the impedance of the measured electrode based on the voltage applied to the second terminal, the potential of the output terminal, and the resistance value of the feedback resistor.

[0009] In this way, the measurement device includes a feedback resistor of the operational amplifier, which is a variable resistor, and obtains a 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 easy and highly accurate measurement of the impedance of the electrode being measured. For example, even if the impedance of the electrode being measured is extremely high, the measurement device can accurately measure the impedance of the electrode being measured by increasing the resistance value of the feedback resistor according to the impedance.

[0010] In one embodiment, (2) In the measuring device of (1), a first switch that switches a terminal connected to the first input terminal and the fourth terminal between a state in which the terminal is connected to the first terminal and a state in which the terminal is not connected to the first terminal; a second switch that switches the terminal connected to the second input terminal between a state in which the terminal is connected to an electromotive force terminal that outputs the potential of the electrode to be measured immersed in the measurement liquid, which is a sample, and a state in which the terminal is not connected to the electromotive force terminal; Further provided with The control unit A measured value of the impedance of the electrode to be measured may be obtained 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.

[0011] In this way, the measurement device is provided with a first switch and a second switch, and by switching these switches, it is possible to switch between a pH measurement mode in which the pH of the measurement solution is measured and an impedance measurement mode in which the impedance of the electrode to be measured is measured. Therefore, in a measurement device that measures the pH of a measurement solution, it is possible to measure the impedance of the electrode to be measured with high accuracy simply by switching the switches.

[0012] In one embodiment, (3) In the measuring device of (2), The control unit acquiring a potential of the electrode to be measured in a state in which 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 solution may be obtained based on the obtained potential of the electrode to be measured.

[0013] Therefore, the measuring device is capable of measuring the pH of the measurement solution and the impedance of the electrode to be measured with high accuracy, with a compact configuration.

[0014] In one embodiment, (4) In any of the measuring devices described in (1) to (3), The control unit The temperature of the electrode to be measured is acquired. The measured value of the impedance of the electrode to be measured may be corrected based on the acquired temperature.

[0015] 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 therefore, it is possible to measure the impedance of the electrode to be measured with even higher accuracy.

[0016] In one embodiment, (5) In the measuring device of (4), The control unit obtaining a temperature correction function that indicates the relationship between temperature and impedance according to the type of the electrode to be measured; The temperature correction function may be used to correct the measured value of the impedance of the electrode under measurement.

[0017] In this way, the measuring device corrects the measured impedance value using a temperature correction function according to the type of electrode being measured, and therefore, it is possible to measure the impedance of the electrode being measured with even higher accuracy.

[0018] In one embodiment, (6) In any of the measuring devices described in (1) to (5), a liquid earth circuit for applying a voltage to the glass electrode and the reference electrode via the measurement liquid; The measuring unit may include a first measuring unit that measures the impedance of a glass electrode as the measured electrode when a voltage is applied by the liquid earth circuit, and a second measuring unit that measures the impedance of a reference electrode as the measured electrode.

[0019] As described above, the measuring device includes a first measuring unit that measures the impedance of the glass electrode and a second measuring unit that measures the impedance of the reference electrode when a voltage is applied by the liquid earth circuit, and is therefore capable of measuring the impedance of the glass electrode and the reference electrode with high accuracy.

[0020] In one embodiment, (7) In the measuring device of (6), The control unit may acquire the pH of the measurement solution based on the potential difference between the glass electrode immersed in the measurement solution and the reference electrode when no voltage is applied by the liquid earth circuit.

[0021] In this way, the measuring device measures the pH of the measurement solution based on the potential difference between the glass electrode immersed in the measurement solution and the reference electrode when no voltage is applied by the liquid earth circuit, making it possible to measure the pH of the measurement solution with high accuracy.

[0022] In one embodiment, (8) In the measuring device of (7), The control unit may correct the pH of the measurement solution obtained based on the potential difference between the glass electrode immersed in the measurement solution and the reference electrode, based on the correlation between fluctuations in the measured impedance of the glass electrode and fluctuations in the measured pH of the measurement solution.

[0023] In this way, the measuring device corrects the measured pH value based on the correlation between the fluctuation in the measured impedance of the glass electrode and the fluctuation in the measured pH of the test solution, so that the measuring device can measure the pH of the test solution with as high accuracy as possible even if the glass electrode is deteriorated.

[0024] In one embodiment, (9) In any one of the measuring devices (1) to (8), The measurement section may include, as the feedback resistor, a resistor capable of switching between a plurality of ranges of resistance values.

[0025] Therefore, the measuring device can switch the resistance value range of the feedback resistor according to the impedance of the electrode to be measured, making it possible to measure the impedance of the electrode to be measured easily and with high accuracy.

[0026] In one embodiment, (10) In any one of the measuring devices according to (1) to (9), The control unit obtaining a degree of deterioration of the electrode to be measured based on the measured value of the impedance of the electrode to be measured; The acquired degree of deterioration may be output.

[0027] In this way, the measuring device automatically outputs the degree of deterioration of the measured electrode, so the user can recognize the degree of deterioration of the measured electrode without having to measure the impedance for each measuring device individually. Because the measuring device measures the impedance of the measured electrode with high accuracy, the degree of deterioration can be accurately obtained.

[0028] In one embodiment, (11) In the measuring device of (10), The control unit predicting the replacement time of the measured electrode based on the degree of deterioration acquired at a plurality of points in time; The predicted replacement time of the measured electrode may be output.

[0029] In this way, the measuring device predicts and outputs the replacement time of the measured electrode based on the degree of deterioration of the measured electrode, so the user can take measures such as replacing the measured electrode in advance at an appropriate timing before the measured electrode breaks down, as necessary.The measuring device measures the impedance of the measured electrode with high accuracy, so it is possible to predict and output the replacement time of the measured electrode.

[0030] In some embodiments, the measurement method includes: (12) A measurement method for a measurement device, comprising: a measurement unit for measuring the impedance of a measurement target electrode having a first terminal and a second terminal; A control unit; A measurement method for a measurement device comprising: The measurement unit an operational amplifier having a first input terminal, a second input terminal, and an output terminal; a feedback resistor that is a variable resistor having a third terminal connected to the output terminal and a fourth terminal connected to the first input terminal; and The control unit acquires a measured value of the impedance of the measured electrode 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.

[0031] The measurement method uses a measurement device equipped with a feedback resistor of an operational amplifier, which is a variable resistor, to obtain a 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 method allows the resistance value of the feedback resistor to be adjusted according to the impedance of the electrode being measured, making it possible to measure the impedance of the electrode being measured easily and with high accuracy. For example, even if the impedance of the electrode being measured is extremely high, the measurement method allows the impedance of the electrode being measured to be measured with high accuracy by increasing the resistance value of the feedback resistor according to the impedance. [Effects of the Invention]

[0032] According to an embodiment of the present disclosure, in a pH measurement device using a glass electrode, the impedance of the electrode can be measured more easily and with higher accuracy. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 10 is a diagram illustrating a configuration of an impedance measuring circuit according to a comparative example. [Figure 2] 1 is a block diagram showing an example of the configuration of a measurement device according to an embodiment; [Figure 3] FIG. 3 is a schematic diagram showing an example of the configuration of the measurement unit in FIG. 2. [Figure 4] FIG. 2 is a diagram illustrating an example of the configuration of a pH measurement circuit according to an embodiment. [Figure 5] FIG. 2 is a diagram illustrating an example of the configuration of a pH measurement circuit according to an embodiment. [Figure 6] FIG. 1 is a diagram illustrating an example of the configuration of an impedance measurement circuit according to an embodiment. [Figure 7] FIG. 1 is a diagram illustrating an example of the configuration of an impedance measurement circuit according to an embodiment. [Figure 8] FIG. 8 is a diagram showing an example of the configuration of a circuit equivalent to the impedance measurement circuit of FIG. 7. [Figure 9] 10A and 10B are diagrams illustrating examples of resistance values ​​of variable resistors according to switching contents of switches. [Figure 10] FIG. 1 is a diagram illustrating a configuration example of a hybrid circuit according to an embodiment. [Figure 11] FIG. 4 is a diagram illustrating an example of the configuration of the measurement circuit unit in FIG. 3. [Figure 12] 1 is a graph showing an outline of the relationship between electrode temperature and impedance. [Figure 13] FIG. 1 is a diagram illustrating an example of the configuration of a measurement system according to an embodiment. [Figure 14] FIG. 14 is a block diagram showing an example of the configuration of the server device in FIG. 13. [Figure 15] FIG. 14 is a block diagram showing an example of the configuration of the terminal device of FIG. 13. [Figure 16] 14 is a flowchart showing an example of the operation of the measurement device of FIG. 13. [Figure 17] 14 is a flowchart showing an example of the operation of the measurement device of FIG. 13. [Figure 18] 14 is a flowchart showing an example of the operation of the measurement device of FIG. 13. DETAILED DESCRIPTION OF THE INVENTION

[0034] <Comparative Example> 1 is a diagram showing the configuration of an impedance measurement circuit 90 according to a comparative example. The impedance measurement circuit 90 is a circuit for measuring a pH value of a glass electrode in a pH measurement device. xThe impedance measurement circuit 90 includes a resistor R9, an operational amplifier (op-amp) 92, and an A / D (Analog-to-Digital) converter 93. As shown in FIG. 1, the resistor R9, one end of which is connected to ground G, is connected to the input terminal of the operational amplifier 92 by a jumper (short bar) 91. The input terminal of the operational amplifier 92 is connected to a voltage V i is applied to the resistor R x The output terminal of the operational amplifier 92 is connected to an A / D converter 93, which outputs a current signal I converted into a digital signal. The impedance measurement circuit 90 measures the voltage V i and the current signal I, the resistance R of the electrode to be measured is calculated. x Obtain the impedance of

[0035] In the operational amplifier 92, an imaginary short is realized so that the potential difference between the non-inverting input terminal and the inverting input terminal is 0 V, and in a balanced 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 the formula (1). I1=V i / (R x +R9) (1)

[0036] The potential V2 of the non-inverting input terminal of the operational amplifier 92 is calculated by the formula (2). V2=R9×I1(2)

[0037] Substituting equation (1) into equation (2), R x Solving for gives equation (3). R x =(V i / V2-1)×R9 (3)

[0038] In this configuration, the resistance value of the resistor R9 is xIf the resistance R is extremely small compared to the impedance of the resistor R, the value of V2 input to the A / D converter 93 will be extremely small, and due to rounding caused by digitization, it will be difficult to obtain the value of V2 with high accuracy. x To accurately measure the impedance of the resistor R x However, it is necessary to connect a resistor R9 of about the same size as the resistor R x Since the impedance of is unknown, the resistance of the connected resistor R9 is x The resistance of resistor R9 may be significantly different from the impedance of resistor R x If the impedance is significantly different from that of the resistor R x It is not possible to measure with high accuracy.

[0039] In particular, the impedance of a glass electrode is generally several tens of MΩ to several GΩ, and resistors with such high resistance are generally expensive. Therefore, it is practically difficult to employ an impedance measurement circuit 90 including a resistor R9 with a resistance value of approximately several tens of MΩ to several GΩ as a module or the like provided in a pH measurement device. As a result, when measuring the impedance of a glass electrode, a high insulation resistance meter is generally used individually for each pH measurement device, which requires a lot of effort for maintenance of the pH measurement device.

[0040] Furthermore, the impedance measuring circuit 90 according to the comparative example requires the resistor R9 to be connected via a jumper 91. Therefore, managing the jumper 91 is cumbersome.

[0041] In this way, the impedance measuring circuit 90 according to the comparative example is x There is room for improvement in terms of measuring the impedance of the electrode R easily and with high accuracy. As a result, it is difficult to perform maintenance properly in a system with multiple pH measurement devices. For example, x Based on the change in impedance of electrode R x This makes it difficult to accurately detect and respond to deterioration.

[0042] <Embodiment> The present disclosure describes an example of a configuration that allows for simple and highly accurate measurement of the impedance of a measurement electrode. Hereinafter, one embodiment of the present disclosure will be described with reference to the drawings. In each drawing, parts having the same configuration or function are designated by the same reference numerals. In the description of this embodiment, duplicated descriptions of the same parts may be omitted or simplified as appropriate.

[0043] 2 is a block diagram showing an example of the configuration of a measurement device 10 according to one embodiment. The measurement device 10 measures the pH of a measurement solution, which is a sample. As shown in FIG. 2, the measurement device 10 includes a control unit 11, a memory unit 12, a communication unit 13, an input unit 14, an output unit 15, a measurement unit 16, and a temperature detection unit 17.

[0044] The control unit 11 includes one or more processors. In one embodiment, the "processor" may be, but is not limited to, a general-purpose processor or a dedicated processor specialized for a particular process. 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.

[0045] The storage unit 12 includes any storage module, such as a hard disk drive (HDD), a solid state drive (SSD), a read-only memory (ROM), and a random access memory (RAM). The storage unit 12 may function as, for example, a main storage device, an auxiliary storage device, or a cache memory. The storage unit 12 stores any information used in the operation of the measuring device 10. For example, the storage unit 12 may store a system program, measurement data, a temperature correction function for each type of electrode, and various information received by the communication unit 13. The storage unit 12 is not limited to being built into the measuring device 10, but may also be an external database or an external storage module.

[0046] The communication unit 13 includes any communication module that can communicate with other devices such as the server device 120 and the terminal device 130 (see FIG. 13) using any communication technology. 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.

[0047] The input unit 14 includes one or more input interfaces that receive input operations from an operator and acquire input information based on the operations of the operator. For example, the input unit 14 may be, but is not limited to, a physical key, a capacitance key, a pointing device, or a touch screen that is integrated with the display of the output unit 15.

[0048] The output unit 15 includes one or more output interfaces that output information to the operator and notify the operator. For example, the output unit 15 is, but is not limited to, a display that outputs information as an image or a speaker that outputs information as sound. Such a display may be, for example, a liquid crystal panel display or an organic EL (Electro Luminescence) display. At least one of the input unit 14 and the output unit 15 may be configured integrally with the measuring device 10 or may be provided separately.

[0049] The measuring unit 16 measures the pH of the measurement liquid, which is a sample, using a glass electrode 162. Details of the measuring unit 16 will be described later with reference to FIGS.

[0050] The temperature detection unit 17 detects the temperatures of a glass electrode 162 and a reference electrode 163 (see FIG. 3), which will be described later. The temperature detection unit 17 is configured by a thermistor or a thermocouple, but the principle of the temperature detection unit 17 is arbitrary.

[0051] The functions of the measuring device 10 can be realized by executing a computer program (program) according to this embodiment on a processor included in the control unit 11. That is, the functions of the measuring device 10 can be realized by software. The computer program causes a computer to execute processing of steps included in the operation of the measuring device 10, thereby causing the computer to realize functions corresponding to the processing of each step. That is, the computer program is a program that causes a computer to function as the measuring device 10 according to this embodiment.

[0052] Some or all of the functions of the measuring device 10 may be realized by a dedicated circuit included in the control unit 11. That is, some or all of the functions of the measuring device 10 may be realized by hardware. Furthermore, the measuring device 10 may be realized by a single computer or by multiple computers working together.

[0053] Fig. 3 is a schematic diagram showing an example of the configuration of the measurement unit 16 in Fig. 2. As shown in Fig. 3, the measurement unit 16 includes a measurement circuit unit 161, a glass electrode 162, a reference electrode 163, and a liquid earth 164. The glass electrode 162, the reference electrode 163, and the liquid earth 164 are immersed in the measurement solution S, which is the sample.

[0054] The measurement circuit unit 161 is connected to the glass electrode 162, the reference electrode 163, and the liquid earth 164. The measurement circuit unit 161 measures the pH of the measurement solution 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 earth 164.

[0055] The glass electrode 162 includes a glass membrane 165, a buffer solution 166 placed inside the glass membrane 165, and an electrode 167. The buffer solution 166 is a liquid whose pH is known in advance. The pH of the buffer solution 166 is, for example, 7. When the glass membrane 165 containing the buffer solution 166 is immersed in a test solution S, an electromotive force proportional to the difference in pH between the buffer solution 166 and the test solution S is generated on the surface of the glass membrane 165. The electrode 167 is used to detect this electromotive force. The electrode 167 is immersed in the buffer solution 166.

[0056] 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 provided with a liquid junction 170, a KCl solution (e.g., 3.3M KCl) 169 contained within the container 168, and an electrode 171. The liquid junction 170 may be made of, for example, porous ceramic. The KCl solution 169 flows out through the liquid junction 170 and comes into contact with the measurement solution S. This allows the reference electrode 163 to obtain a constant reference potential with the measurement solution S regardless of changes in the properties of the measurement solution S, such as temperature, pressure, and flow rate. The electrode 171 is immersed in the KCl solution 169.

[0057] In general, the electromotive force generated on the surface of the glass film 165 is measured from the potentials of the electrodes 167 and 171, and the pH of the test solution S is measured according to this electromotive force. Meanwhile, the measurement unit 16 further includes a liquid earth 164 having an electrode 172 immersed in the test solution S. The measurement unit 16 acquires the potential of the glass electrode 162 relative to the liquid earth 164 and the potential of the reference electrode 163 relative to the liquid earth 164, and measures the electromotive force generated on the surface of the glass film 165 from the difference between these potentials. Therefore, the measurement device 10 according to this embodiment can measure the pH of the test solution S with high accuracy.

[0058] Meanwhile, the measurement circuit unit 161 measures the impedance of the glass electrode 162 while the glass electrode 162 and the liquid earth 164 are immersed in the test solution S. Specifically, the measurement circuit unit 161 measures the potential difference between the electrode 167 and the electrode 172 via the test solution 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 comparison electrode 163 while the comparison electrode 163 and the liquid earth 164 are immersed in the test solution S. Specifically, the measurement circuit unit 161 measures the potential difference between the electrode 171 and the electrode 172 via the test solution S, and measures the impedance of the comparison electrode 163 based on the measured value of the potential difference.

[0059] The impedance of the glass electrode 162 is several tens of MΩ to several GΩ. In contrast, the impedance of the test solution S is negligibly small. Therefore, the measurement unit 16 can measure the impedance of the glass electrode 162 via the test solution S. The impedance of the reference electrode 163 is several kΩ to several hundreds of kΩ. Therefore, the measurement device 10 may measure the impedance of the test solution S separately, i.e., the conductivity of the test solution S, and measure the impedance of the reference electrode 163 by subtracting the impedance of the test solution S from the impedance measured via the test solution S and the reference electrode 163.

[0060] Next, a pH measurement circuit 30 for measuring the pH of the measurement solution S will be described with reference to FIGS. 4 and 5. FIG. 4 is a diagram showing an example of the configuration of a pH measurement circuit 30 according to one embodiment. As shown in FIG. 4, the pH measurement circuit 30 includes an operational amplifier 31, an A / D converter 32, and resistors R11 and R12. While FIG. 4 shows the pH measurement circuit 30 configured as a non-inverting amplifier circuit, the pH measurement circuit 30 is not limited to a non-inverting amplifier circuit as long as it can convert a signal from a voltage source with extremely high impedance into a voltage without attenuation. For example, the pH measurement circuit 30 may be configured as an inverting amplifier circuit or a voltage follower circuit (see FIG. 5).

[0061] 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 electromotive force is applied to the non-inverting input terminal (+ input terminal) serving as the second input terminal. The terminal that outputs the potential of the electrode to be measured immersed in the measurement solution (sample) is also called the "electromotive force terminal." A resistor R12, which is a feedback resistor, is connected between the inverting input terminal (- input terminal) serving as the first input terminal and the output terminal. The inverting input terminal is connected to ground G via resistor R11. The output terminal is connected to an A / D converter 32, and the output of the operational amplifier 31 is output as a digital signal.

[0062] In 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, which is 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. Since it is known that there is a certain relationship between the voltage E based on the electromotive force and pH, 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 earth 164 and the potential E2 of the reference electrode 163 relative to the liquid earth 164 are obtained, and the pH is obtained according to the difference between the two (E1-E2).

[0063] Fig. 5 shows an example of the configuration of a pH measurement circuit 30a configured as a voltage follower circuit. In the example of the configuration of the pH measurement circuit 30a configured as a voltage follower circuit as shown in Fig. 5, the output terminal and the inverting input terminal (- input terminal) of the operational amplifier 31 are directly connected.

[0064] Next, an impedance measurement circuit 40 for measuring the impedance of the electrode to be measured will be described with reference to Fig. 6. Fig. 6 is a diagram showing an example of the configuration of the impedance measurement circuit 40 according to one embodiment. As shown in Fig. 6, the impedance measurement circuit 40 includes an operational amplifier 41, an A / D converter 42, a feedback resistor (variable resistor) R p , and voltage source V iThe impedance measurement circuit 40 is provided with a measurement electrode R having a first terminal and a second terminal. x Measure the impedance of the

[0065] 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 serves as a second input terminal, is connected to the ground G. A feedback resistor R is provided between the inverting input terminal, which serves as a first input terminal, and the output terminal. p is connected to the feedback resistor R p has a third terminal and a fourth terminal, and 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.

[0066] The impedance measurement circuit 40 measures a known voltage V with respect to liquid ground 164. i Apply this voltage V i The output voltage V of the operational amplifier 41 o By measuring the measured electrode R x Measure the unknown impedance at the current i x to voltage V o is obtained by the amplifier 41, and this voltage V o and feedback resistor R p and voltage V i From the measured electrode R x The inverting input terminal of the operational amplifier 41 is supplied with a voltage V i The electrode to which the current is applied (resistance R x ) is connected to the first terminal of the

[0067] Here, in the operational amplifier 41, an imaginary short is realized so that the potential difference between the non-inverting input terminal and the inverting input terminal becomes 0V, so the potential V - is the potential V of the non-inverting input terminal + = 0. Therefore, the resistance R x The current i flows toward the inverting input terminal of the operational amplifier 41. x is calculated using equation (4). i x =(V i -V - ) / R x =V i / R x (4)

[0068] On the other hand, the feedback resistor R p The current i flows from the output terminal to the inverting input terminal. p is the potential of the output terminal V o and the potential V of the inverting input terminal - Therefore, it is calculated by equation (5). i p =(V o -V - ) / R p =V o / R p (5)

[0069] Here, there is no current input or output at the inverting input terminal of the operational amplifier 41. Therefore, the sum of the currents is 0, and i x +i p = 0. Therefore, equation (6) holds true. i x =-i p (6)

[0070] Substituting equations (4) and (5) into equation (6), equation (7) is established. V i / R x =-V o / R p (7)

[0071] By transforming equation (7), equation (8) is established. R x =-(V i / V o )R p (8) Here, the negative sign in equation (8) means that the current i p , i x This is due to the definition of the orientation of the

[0072] Therefore, the impedance of the electrode to be measured is expressed as the voltage V i , V i , and feedback resistor R p In FIG. 6, the applied voltage V i is shown with an AC symbol, but may also be a DC voltage.

[0073] By transforming equation (8), equation (9) is established. V o =-(R p / R x )V i (9) Therefore, R p and R x If the difference in magnitude between the o falls outside the range of signal values ​​that the A / D converter 42 or other components can process, and the impedance R x Therefore, the measurement unit 16 is configured to measure the feedback resistance R p The resistance value of R x By setting the value close to x Measure with high precision.

[0074] Feedback resistor R p By connecting the switches and resistors in a binary tree structure, a high resistance value can be achieved using resistors with low resistance values. Fig. 7 is a diagram showing an example of the configuration of an impedance measurement circuit 40a according to one embodiment.

[0075] In Figure 7, the feedback resistor R p 8 includes resistors R1, R2, R4 to R7, and switches S1 to S4. Resistors R1 and R2 are connected in parallel. One end of each of resistors R1 and R2 is connected to the inverting input terminal of operational amplifier 41, and the other end is connected to switch S1. One end of switch S1 is connected to switch S2. Switch S1 can switch the circuit element connected to switch S2 between resistor R1 and resistor R2. By switching switch S1, resistor R1 or R2 corresponds to resistor Rc in FIG. 8.

[0076] Resistors R4 to R7 are connected in series in this order. The end of resistor R4 that is not connected to resistor R5 is connected to the output terminal of operational amplifier 41. The end of resistor R7 that is not connected to resistor R6 is connected to ground G.

[0077] One end of switch S2 is connected to switch S1. Switch S2 can switch the circuit element connected to switch S1 between switches S4 and S3. Switch S4 can switch the circuit element connected to switch S2 between both terminals of resistor R4. Switch S3 can switch the circuit element connected to switch S2 between both terminals of resistor R6. In this way, by switching switches S2, S3, and S4, switch S1 is electrically connected directly to any of the connection terminal 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. In other words, depending on the switching operation of switches S2 to S4, the series of resistors R4 to R7 is divided into two by the junction between the resistors directly connected to switch S1, and operates as voltage-dividing resistors Ra and Rb, except when switch S1 is directly connected to the output terminal of operational amplifier 41. The switches S1 to S4 are semiconductor or relay type switches, but may be realized by other methods.

[0078] The feedback resistor R of the impedance measurement circuit 40a p The resistance value of the resistors Ra, Rb, and Rc is determined by switching the switches S1 to S4. Referring to FIG. 8, the resistance values ​​of the voltage dividing resistors Ra, Rb, and resistor Rc and the resistance value of the feedback resistor R p 8 is a diagram showing an example of the configuration of a circuit 40b equivalent to the impedance measuring circuit 40a of FIG.

[0079] 8, the output terminal of the operational amplifier 41 is connected to one end of a resistor Rb. The other end of the resistor Rb is connected to one end of a resistor Ra and to one end of a resistor Rc. The other end of the resistor Rc is connected to the inverting input terminal of the operational amplifier 41, forming a negative feedback circuit for the operational amplifier 41. The other end of the resistor Ra is connected to ground G.

[0080] As shown in FIG. 8, the potential at 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 - In a negative feedback circuit such as that shown in FIG. 8, the feedback signal follows the input signal, and as mentioned above, in a steady state, the input signal and the feedback signal are in a so-called imaginary short state, as if they were shorted. In the imaginary short state, the potential V of the inverting input terminal of the operational amplifier 41 - The potential difference between the potential of the non-inverting input terminal and the potential of the non-inverting input terminal (which is 0 due to grounding) is 0, so V - =0.

[0081] In the imaginary short state, the input and output of the current at 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 of the operational amplifier 41 is x The current I in is equal to (I in =I3). Therefore, the potential V1 at the connection terminal between resistor Rb and resistor Ra is Rc×I3=Rc×I in is.

[0082] The potential V of the output terminal of the operational amplifier 41 o is the current I2 flowing from the output terminal to the resistor Rb, the resistor Rb, and the aforementioned V1, o =V1+Rb×I2. As mentioned above, V1=Rc×I in The relationship is I2=I1+I3=I1+I in Since the following relationship holds, V o = Rc × I in +Rb×(I1+I in) holds. Furthermore, the relationship I1 = V1 / Ra holds. As mentioned above, the relationship V1 = Rc × Iin holds, so the following equation (10) holds. V o = Rc × I in +Rb×(V1 / Ra+I in ) = Rc × I in +Rb×(Rc / Ra×I in +I in ) =I in ×(Rc×(1+Rb / Ra)+Rb) (10)

[0083] Here, by transforming equation (7), equation (11) is established. R p =-(V o / V i )R x (11)

[0084] When equation (10) is substituted into equation (11), the following equation (12) is established. R p =-(I in R y / V i )R x (12) However, R y is given by equation (13). R y =Rc×(1+Rb / Ra)+Rb (13)

[0085] Here, I in =-I x Furthermore, from equation (4), equation (14) holds. I in =-V i / R x (14)

[0086] Substituting equation (14) into equation (12) gives equation (15). R p =R y =Rc×(1+Rb / Ra)+Rb (15)

[0087] Here, resistor R1 is 10 MΩ, resistor R2 is 1 kΩ, resistor R4 is 900 Ω, resistor R5 is 90 Ω, resistor R6 is 9 Ω, and resistor R7 is 1 Ω. In this case, the connection relationship of switches S1 to S4 and the resistances of Ra, Rb, Rc, and R p The relationship between the resistance value of the feedback resistor R and the switching state of the switch is shown in Figure 9. p 10A and 10B are diagrams illustrating examples of resistance values ​​of the resistors.

[0088] For example, when the range is "1", switch S1 is set to "B", so switch S2 and resistor R2 (=1kΩ) are connected via switch S1, and Rc = 1,000Ω. Switch S2 is set to "A". Switch S4 is set to "A". Therefore, regardless of the setting of switch S3, Ra of the voltage dividing resistors is 1,000Ω (=R4+R5+R6+R7), and Rb is 0Ω. Therefore, the feedback resistor R p is 1,000 Ω.

[0089] Also, for example, when the range is "7", switch S1 is set to "A", so switch S2 and resistor R1 (=10MΩ) are connected via switch S1, and 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 dividing resistors is 10Ω (=R6+R7) and Rb is 990Ω (=R4+R5). Therefore, the feedback resistor R p is 1,000,000,990 Ω.

[0090] As shown in Figure 9, the feedback resistor R p The resistance value of the feedback resistor R can be switched in eight steps over a wide dynamic range of 1k, 10k, 100k, 1M, 10M, 100M, 1G, and 10G by switching the switches S1, S2, S3, and S4. p There is only one resistor of 10 MΩ, resistor R1. There are only four switches, S1, S2, S3, and S4. Therefore, the feedback resistor Rp is 10 from minimum resistance to maximum resistance. 7 A dynamic range as wide as 1000 times can be achieved with a small number of high-value resistors and switches. p In this case, there are no switches connected in parallel that can be energized at the same time, so the leakage current generated in the switches does not accumulate to become a large error current. For example, switches S3 and S4 are switched by switch S2. Therefore, switches S3 and S4 do not energize at the same time, and leakage currents do not accumulate. Therefore, the feedback resistor R p According to this, a variable resistor with a large dynamic range, low cost, and simple structure can be realized. The impedance measurement circuit 40 uses such a feedback resistor R p By providing this, it is possible to measure the impedance of the glass electrode 162 and the reference electrode 163 with high accuracy over a wide dynamic range.

[0091] In addition, the feedback resistor R p The configuration of the feedback resistor R p In the case of the feedback resistor Rc, either one of the two resistors R1 and R2 can be selected as the resistor Rc. However, a specific resistor may be predetermined as the resistor Rc, or it may be selectable from three or more resistors. p In the feedback resistor R in FIG. 7, four resistors R4 to R7 connected in series are divided into voltage dividing resistors Ra and Rb by switches S2 to S4. The number of resistors may be three or less, or five or more. p In order to realize the voltage dividing resistors Ra and Rb, three switches S2 to S4 connected in a binary tree structure are provided, but the number of switches may be two or less, or may be four or more. p may have a configuration provided in the amplifier circuit described in Japanese Patent Laid-Open No. 2022-002384 (for example, the feedback resistor included in the amplifier circuit shown in FIGS. 1, 3, 5, and 8 of the same publication), for example.

[0092] The measurement circuit section 161 may include the pH measurement circuits 30, 30a described with reference to Figures 4 and 5 and the impedance measurement circuit 40 described with reference to Figures 6 to 9, separately for each of the glass electrode 162 and the reference electrode 163. Alternatively, the measurement circuit section 161 may include a hybrid circuit 50 that can switch between the pH measurement circuit 30 and the impedance measurement circuit 40 using a switch, for each of the glass electrode 162 and the reference electrode 163.

[0093] 10 is a diagram showing an example of the configuration of a hybrid circuit 50 according to an embodiment. As shown in FIG. 10, the hybrid circuit 50 includes switches 51 and 52, an operational amplifier 53, an A / D converter 54, a resistor R11, and a feedback resistor (variable resistor) R p , and voltage source V i Equipped with.

[0094] As shown in Fig. 10, a switch 51 is connected to the non-inverting input terminal serving as the second input terminal of the operational amplifier 53. The switch 51 serving as the second switch can switch the circuit element connected to the non-inverting input terminal between the ground G (set to "B") and an electrode (set to "A") to which a voltage E based on an electromotive force is applied. A feedback resistor R p The output terminal is connected to an A / D converter 54, and the output of the operational amplifier 53 is output as a digital signal. A switch 52 is also connected to the inverting input terminal of the operational amplifier 53. The switch 52, which serves as a first switch, connects the circuit element connected to the inverting input terminal to a known voltage V with respect to the liquid ground 164. i is applied, impedance R x and a resistor R11 (set to "A") having one end connected to ground G. The switches 51 and 52 are semiconductor or relay type switches, but may be realized by other methods.

[0095] When switches 51 and 52 are both set to "A," hybrid circuit 50 becomes equivalent to pH measurement circuit 30 shown in Fig. 4. When switches 51 and 52 are both set to "B," hybrid circuit 50 becomes equivalent to impedance measurement circuit 40 shown in Fig. 6. By providing such a hybrid circuit 50 for each of glass electrode 162 and reference electrode 163, measurement circuit unit 161 can measure the potential and impedance based on the pH of each electrode.

[0096] 10, the impedance measurement circuit 40 of FIG. 6 can be switched with the pH measurement circuit 30 of FIG. 4, but the hybrid circuit 50 may be switched with the pH measurement circuit 30a of FIG. 5 instead of the pH measurement circuit 30 of FIG. 4. In this case, the switch 52 may be capable of switching the inverting input terminal of the operational amplifier 53 between a state in which it is connected to the electrode to be measured (set to "B") and a state in which it is not connected to other circuit elements (set to "A"). The feedback resistor R p may short-circuit the output terminal and the inverting input terminal of the operational amplifier 53. Furthermore, the hybrid circuit 50 may be configured to switch the impedance measurement circuit 40 with a pH measurement circuit configured as an inverting amplifier circuit.

[0097] FIG. 11 is a diagram showing an example of the configuration of the measurement circuit section 161 of FIG. 3. As shown in FIG. 11, the measurement circuit section 161 includes hybrid circuits 50a and 50b, and a liquid ground circuit 60. The hybrid circuit 50a is connected to a glass electrode 162. The hybrid circuit 50b is connected to a reference electrode 163. Each of the hybrid circuits 50a and 50b has the configuration described with reference to FIG. 10. The liquid ground circuit 60 is connected to a liquid ground 164. The liquid ground circuit 60 includes a switch 61. The switch 61 connects the circuit elements connected to the electrode 172 of the liquid ground 164 to the ground G (set to "A") and the voltage source V i (set to "B") and . The switch 61 is a semiconductor or relay type switch, but may be realized by other methods. In FIG. 11, the applied voltage V iis shown with an AC symbol, but may also be a DC voltage.

[0098] When measuring the pH of the measurement solution S, the measurement circuit section 161 sets all of the 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 section 161 sets all of the switches 51, 52, and 61 to "B." Because the measurement device 10 is equipped with such a measurement circuit section 161, it is possible to measure the pH of the measurement solution S and the impedance of the electrode to be measured simply and accurately with a compact configuration.

[0099] It is known that the impedance of a measured electrode changes depending on the electrode's temperature. FIG. 12 is a graph 71 showing an outline of the relationship between the temperature and impedance of the measured electrode. In FIG. 12, the horizontal axis represents the electrode temperature. The vertical axis represents the electrode impedance on a logarithmic scale. Graph 71 shows the relationship between the electrode temperature and impedance. Graph 71 shows that the electrode impedance decreases rapidly with increasing temperature. 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 electrode temperature measured by the temperature detection unit 17. Specifically, the measuring device 10 may acquire a temperature correction function that indicates the correspondence between temperature and impedance according to the type of electrode and correct the measured impedance value using the temperature correction function. By performing such temperature correction, the measuring device 10 can measure the impedance of the measured electrode with high accuracy.

[0100] In the measurement system 1, the measurement device 10 may transmit the measurement results to the server device 120 via the network N. The server device 120 stores the measurement electrode R x The impedance of the electrode, deterioration of the electrode, etc. may be managed. Such a measurement system 1 will be described with reference to Fig. 13. Fig. 13 is a diagram showing an example of the configuration of the measurement system 1 according to one embodiment.

[0101] 13, the measurement system 1 includes a measurement device 10, a server device 120, and a terminal device 130. The measurement device 10, the server device 120, and the terminal device 130 are communicably connected to each other via an arbitrary network N including the Internet, an intranet, or a combination thereof. The number of measurement devices 10, the server device 20, and the terminal device 130 is arbitrary and may be two or more.

[0102] The server device 120 manages the measurement results of the measurement device 10, such as the pH of the measurement solution S and the impedance of the electrode to be measured, as well as the deterioration status of the electrode. The server device 120 is configured by any computer, such as a WS (Workstation) or a PC (Personal Computer), for example.

[0103] Terminal device 130 accesses server device 120 to obtain the measurement results and the deterioration status of the electrodes managed by measuring device 10. Terminal device 130 may be operated by a user, including a maintenance worker for measuring device 10. Terminal device 130 is configured by any computer, such as a PC, a tablet terminal, or a smartphone.

[0104] Fig. 14 is a block diagram showing an example configuration of server device 120 in Fig. 13. Server device 120 includes a control unit 121, a storage unit 122, and a communication unit 123. The configurations of control unit 121, storage unit 122, and communication unit 123 are similar to those of control unit 11, storage unit 12, and communication unit 13 of measurement device 10, and therefore detailed description thereof will be omitted.

[0105] Fig. 15 is a block diagram showing an example configuration of terminal device 130 in Fig. 13. 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 control unit 131, storage unit 132, communication unit 133, input unit 134, and output unit 135 are similar to those of control unit 11, storage unit 12, communication unit 13, input unit 14, and output unit 15 of measuring device 10, and therefore detailed description thereof will be omitted.

[0106] Fig. 16 is a flowchart showing an example of the operation of the measuring device 10 in Fig. 13. Fig. 16 shows a processing procedure in which the measuring device 10 measures the impedance of the electrode to be measured. The operation of the measuring device 10 described with reference to Fig. 16 may correspond to one of the measurement methods of the measuring device 10. The operation of each step in Fig. 16 is performed under the control of the control unit 11 of the measuring device 10, but all or part of the steps in Fig. 16 may be performed by the server device 120 or the terminal device 130.

[0107] Hereinafter, the measurement device 10 has the configuration shown in FIG. 11, and the feedback resistors R p 7 and 9 will be described below. An example of the operation when measuring the impedance of the glass electrode 162 will be described below, but the operation when measuring the impedance of the reference electrode 163 is similar.

[0108] 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 each of the switches 51a, 51b, and 61 in FIG. 11 to "B."

[0109] In step S12, the control unit 11 sets the feedback resistor R p Set the resistance value of the feedback resistor R to the minimum range. p When the resistance range of the feedback resistor R p For the above, switches S1 to S4 are set to the setting value corresponding to range "1". Specifically, switch S1 is set to "B", switch S2 is set to "A", and switch S4 is set to "A". The setting of switch S3 is arbitrary.

[0110] In step S13, the control unit 11 adjusts the potential V o The control unit 11 determines whether the potential V is within a predetermined range (for example, the measurement range of the A / D converter 54). oIf it is within the predetermined range (YES in step S13), the process proceeds to step S15, and if it is not (NO in step S13), the process proceeds to step S14. p The resistance value of the feedback resistor R is first set to the minimum range and then gradually increased, but it may also be set to the maximum range and then gradually decreased. p While changing the resistance value of o is within a predetermined range, the feedback resistor R p The order in which the resistance values ​​are changed is not particularly limited.

[0111] In step S14, the control unit 11 sets the feedback resistor R p Increase the resistance range by one step. For example, p 9, the control unit 11 sets the range to "2." Then, the control unit 11 proceeds to step S13 again. o The processes of steps S13 and S14 are repeated until the potential V falls within the predetermined range. o This prevents the value of (I) from being rounded off in the A / D converter 54, and allows the impedance of the electrode to be measured to be obtained with high precision.

[0112] In step S15, the control unit 11 controls the potential V o Based on the impedance of the electrode to be measured, R x Specifically, the potential V o and known V i , R p Based on this, the impedance R x In this embodiment, the impedance is corrected based on the temperature of the electrode to be measured in the process described later with reference to Fig. 17, but the control unit 11 may also correct the impedance based on the temperature in step S15.

[0113] In step S16, control unit 11 determines whether or not to store the impedance measurement value acquired in step S15. For example, when a user instructs control unit 11 to store the measurement value, control unit 11 may determine to store the measurement value in storage unit 12. If control unit 11 determines to store the measurement value (YES in step S16), control unit 11 proceeds to step S17, and if not (NO in step S16), control unit 11 proceeds to step S18.

[0114] In step S17, the control unit 11 stores the impedance measurement value acquired 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 cause the server device 120 or the terminal device 130 to store the measurement value.

[0115] In step S18, control unit 11 determines whether to continue measurement. For example, control unit 11 may determine not to continue measurement when the user instructs control unit 11 to end impedance measurement. If control unit 11 determines to continue measurement (YES in step S18), control unit 11 returns to step S15, and if not (NO in step S18), control unit 11 proceeds to step S19.

[0116] In step S19, the control unit 11 sets the pH measurement mode to measure the pH of the measurement solution S. Specifically, the control unit 11 sets each of the switches 51a, 51b, and 61 in Fig. 11 to "A." After completing the process of step S19, the control unit 11 ends the process of the flowchart in Fig. 16.

[0117] FIG. 17 is a flowchart showing an example of the operation of the measuring device 10 in FIG. 13. FIG. 17 shows a processing procedure for correcting the measured impedance value obtained based on the flowchart in FIG. 16 based on the temperature of the electrode to be measured. The operation of the measuring device 10 described with reference to FIG. 17 may correspond to one of the measurement methods of the measuring device 10. The operation of each step in FIG. 17 is executed based on the control of the control unit 11 of the measuring device 10, but all or part of the steps in FIG. 17 may be executed by the server device 120 or the terminal device 130. Below, an example of the operation when correcting the measured impedance value of the glass electrode 162 will be described, but the operation for the reference electrode 163 is similar.

[0118] In step S21, the control unit 11 acquires the measured value of the impedance of the electrode to be measured before temperature correction is performed.

[0119] 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.

[0120] In step S23, control unit 11 corrects the measured impedance value using the temperature correction function acquired in step S22. Specifically, control unit 11 corrects the measured impedance value using the temperature correction function acquired in step S22 based on the temperature of glass electrode 162 detected by temperature detection unit 17. Control unit 11 may correct the measured impedance value to a value corresponding to a reference temperature (e.g., 25 degrees), for example.

[0121] In step S24, control unit 11 records the impedance measurement value corrected in step S23. Specifically, control unit 11 stores the corrected measurement value in storage unit 12. In addition, control unit 11 may transmit the corrected measurement value to server device 120 or terminal device 130 via communication unit 13, and store the corrected measurement value in server device 120 or terminal device 130. Upon completing the processing of step S24, control unit 11 ends the processing of the flowchart in FIG. 17.

[0122] FIG. 18 is a flowchart showing an example of the operation of the measuring device 10 of FIG. 13. FIG. 18 shows a processing procedure for acquiring the degree of deterioration of an electrode based on the impedance measurement value acquired based on the flowchart of FIG. 16 or the impedance measurement value corrected based on the flowchart of FIG. 17. The operation of the measuring device 10 described with reference to FIG. 18 may correspond to one of the measurement methods of the measuring device 10. The operation of each step of FIG. 18 is executed under the control of the control unit 11 of the measuring device 10, but all or part of the steps of FIG. 18 may be executed by the server device 120 or the terminal device 130. Below, an example of the operation when acquiring the degree of deterioration of the glass electrode 162 will be described, but the operation for the reference electrode 163 is similar.

[0123] In step S31, the control unit 11 acquires a measured value of the impedance of the glass electrode 162 acquired based on the flowchart of FIG. 16 or corrected based on the flowchart of FIG.

[0124] In step S32, the control unit 11 acquires the degree of deterioration of the glass electrode 162 based on the measurement value acquired in step S31. It is generally known that the impedance of the electrode being measured increases as the deterioration progresses. Therefore, the control unit 11 may acquire a relational expression between the impedance value and an index indicating the degree of deterioration and use the relational expression to acquire the degree of deterioration of the glass electrode 162. The impedance value in the relational expression may 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 acquire a measured impedance value corrected to a value corresponding to the reference temperature based on the flowchart of FIG. 17. The control unit 11 may acquire the relational expression pre-stored in the memory unit 12 or may receive it from the server device 120 via the communication unit 13. The degree of deterioration of the electrode may be expressed numerically or in several stages.

[0125] In step S33, the control unit 11 notifies the user of the degree of deterioration acquired in step S32. For example, the degree of deterioration may be displayed on the display of the output unit 15. Specifically, the control unit 11 may cause the output unit 15 to display a graph showing the change over time in the impedance or the degree of deterioration measured at multiple points in time, thereby visually indicating the degree of deterioration. The control unit 11 may perform regression analysis on the graph showing the change over time in the degree of deterioration, predict when the degree of deterioration will reach a predetermined threshold, and notify the user of the predicted time as the time to replace the electrodes. The control unit 11 may transmit the degree of deterioration and the time to replace the electrodes to the terminal device 130, and display them on the display of the output unit 135. After completing the process of step S33, the control unit 11 ends the process of the flowchart of FIG. 18.

[0126] As described above, the measurement device 10 includes a measurement unit 16 that measures the impedance of the electrode to be measured, and a control unit 11. The measurement 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 that is a variable resistor connected to the output terminal and the inverting input terminal of the operational amplifier. p The control unit 11 has an inverting input terminal and a feedback resistor Rp is the measured electrode R x When the electrode is connected to one end of the test piece, the voltage applied to the other end of the test piece, the potential at the output terminal of the operational amplifier, and the feedback resistor R p Based on the resistance value of the measured electrode R x Obtain a measurement of the impedance of the

[0127] Therefore, according to the measurement device 10, the feedback resistor R p The resistance value of the measured electrode R x Therefore, the measurement device 10 can easily and accurately measure the impedance of the measurement target electrode R. x Furthermore, the measurement device 10 can omit the use of external components such as the jumper 91. For example, the impedance of the measurement electrode R x Even if the impedance of the feedback resistor R is extremely large, the measurement device 10 adjusts the feedback resistor R p By increasing the resistance of the measured electrode R x It is possible to measure the impedance with high accuracy.

[0128] The measurement device 10 also includes a feedback resistor R p 8, and the voltage dividing resistors Ra and Rb are configured by arranging a plurality of switches in a binary tree structure as shown in FIG. 7. Therefore, the measuring device 10 can be configured by using a feedback resistor R, which is a variable resistor with a wide dynamic range at low cost, without using an expensive high resistance. p It is possible to achieve the following.

[0129] Furthermore, the measurement device 10 can measure the measured electrode R with high accuracy in this way. x Using the measured impedance of the measured electrode R x In order to accurately detect the degree of deterioration of the measured electrode R x It is possible to notify the user of the degree of deterioration and the replacement time.

[0130] Furthermore, the measurement device 10 outputs the measured electrode R x The user is notified of the degree of deterioration and replacement time of each measuring device 10. Therefore, even if a plurality of measuring devices 10 is installed, the user can properly manage each measuring device 10 without having to check on each measuring device 10.

[0131] Furthermore, the measuring device 10 can switch between a pH measurement mode in which the pH of the measurement solution S is measured and an impedance measurement mode in which the impedance of the electrode to be measured is measured simply by switching switches 51 (51a, 51b), 52 (52a, 52b), and 61.

[0132] The measurement device 10 also includes a measurement electrode R x Based on the temperature of the measured electrode R x In order to correct the measured impedance of the electrode R x It is possible to measure the impedance with higher accuracy.

[0133] The measuring device 10 passes 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 band-pass filter, and detects the applied voltage V i The signal corresponding to the frequency of the output terminal (potential V o With this configuration, even if the output of the operational amplifier 53 contains noise components due to low purity of the measurement solution S, it is possible to measure the impedance of the electrode to be measured with high accuracy.

[0134] The measuring device 10 may also be provided with a separate component for measuring the conductivity (impedance) of the test solution S. For example, the measuring device 10 may be provided with another liquid ground in addition to the liquid ground 164, and the conductivity of the test solution S may be determined 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 test solution S. Furthermore, in the impedance measurement mode, the measuring device 10 can measure the impedance of the electrode to be measured with even higher accuracy by eliminating the influence of the conductivity of the test solution S.

[0135] Furthermore, if a correlation is found between fluctuations in the impedance value of glass electrode 162 and fluctuations in the pH value of the test solution S, measurement device 10 may correct the pH value by taking into account the fluctuations in the impedance value of glass electrode 162. That is, measurement device 10 may calibrate the pH value obtained based on the potential difference between glass electrode 162 and reference electrode 163, depending on the correlation between fluctuations in the impedance value of glass electrode 162 and fluctuations in the measured pH value of test solution S. With this configuration, even if glass electrode 162 has deteriorated to some extent, measurement device 10 can measure the pH value of test solution S with as high an accuracy as possible, regardless of such deterioration of glass electrode 162.

[0136] The present disclosure is not limited to the above-described embodiments. For example, multiple blocks shown in the block diagrams may be integrated, or one block may be divided. Multiple steps shown in the flowcharts may be executed in parallel or in a different order depending on the processing capabilities of the device executing each step, or as needed, instead of being executed in chronological order as described. Other modifications are possible without departing from the spirit of the present disclosure. [Explanation of symbols]

[0137] 1. Measurement System 10. Measuring equipment 11 Control section 12 Storage section 13 Communications Department 14 Input section 15 Output section 16 Measuring part 17 Temperature detection unit 30 pH measurement circuit 31 Operational Amplifier 32 A / D converter 40 Impedance measurement circuit 41 Operational Amplifier 42 A / D converter 50 Hybrid Circuit 51,52 Switch 53 Operational Amplifier 54 A / D converter 60 Liquid Earth Circuit 61 Switch 71 graphs 90 Impedance measurement circuit 91 Jumper 92 Operational Amplifier 93 A / D converter 120 Server device 121 Control Unit 122 Storage section 123 Communications Department 130 Terminal Equipment 131 Control Unit 132 Storage section 133 Communications Department 134 Input section 135 Output section 161 Measurement circuit section 162 Glass Electrode 163 Reference electrode 164 Liquid Earth 165 Glass membrane 166 Buffer 167 Electrode 168 Container 169 KCl solution 170 Liquid junction 171 Electrode 172 Electrode G ground N Network R1,R2,R4-R7 resistance R9, R11, R12 resistors Ra,Rb,Rc resistance R p Feedback resistor R x Electrode to be measured S Measurement liquid S1-S4 switches V i Applied voltage

Claims

1. a measuring unit for measuring the impedance of a measurement target electrode having a first terminal and a second terminal; A control unit; Equipped with The measurement unit an operational amplifier having a first input terminal, a second input terminal, and an output terminal; a feedback resistor that is a variable resistor having a third terminal connected to the output terminal and a fourth terminal connected to the first input terminal; and the control unit, in a state in which the first input terminal is connected to the first terminal, acquires a measured value of the impedance of the electrode to be measured based on a voltage applied to the second terminal, a potential of the output terminal, and a resistance value of the feedback resistor. Measuring device.

2. a first switch that switches a terminal connected to the first input terminal and the fourth terminal between a state in which the terminal is connected to the first terminal and a state in which the terminal is not connected to the first terminal; a second switch that switches the terminal connected to the second input terminal between a state in which the terminal is connected to an electromotive force terminal that outputs the potential of the electrode to be measured immersed in the measurement liquid, which is a sample, and a state in which the terminal is not connected to the electromotive force terminal; Further provided with The control unit a measurement value of the impedance of the electrode to be measured is obtained 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; The measuring device according to claim 1 .

3. The control unit acquiring a potential of the electrode to be measured in a state in which 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; obtaining a pH value of the measurement solution based on the obtained potential of the electrode to be measured; The measuring device according to claim 2 .

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

5. The control unit obtaining a temperature correction function that indicates the relationship between temperature and impedance according to the type of the electrode to be measured; correcting the measured value of the impedance of the electrode to be measured using the temperature correction function; 5. The measuring device according to claim 4.

6. a liquid earth circuit for applying a voltage to the glass electrode and the reference electrode via the measurement liquid; The measuring unit includes a first measuring unit that measures the impedance of a glass electrode as the electrode to be measured when a voltage is applied by the liquid earth circuit, and a second measuring unit that measures the impedance of a reference electrode as the electrode to be measured. The measuring device according to any one of claims 1 to 3.

7. the control unit acquires the pH of the measurement solution based on the potential difference between the glass electrode immersed in the measurement solution and the reference electrode when no voltage is applied by the liquid earth circuit. The measuring device according to claim 6.

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

9. The measurement device according to claim 1 , wherein the measurement section includes, as the feedback resistor, a resistor capable of switching between a plurality of ranges of resistance values.

10. The control unit obtaining a degree of deterioration of the electrode to be measured based on the measured value of the impedance of the electrode to be measured; outputting the acquired degree of deterioration; The measuring device according to any one of claims 1 to 3.

11. The control unit predicting the replacement time of the measured electrode based on the degree of deterioration acquired at a plurality of points in time; outputting the predicted replacement time of the measured electrode; The measuring device according to claim 10.

12. a measuring unit for measuring the impedance of a measurement target electrode having a first terminal and a second terminal; A control unit; A measurement method for a measurement device comprising: The measurement unit an operational amplifier having a first input terminal, a second input terminal, and an output terminal; a feedback resistor that is a variable resistor having a third terminal connected to the output terminal and a fourth terminal connected to the first input terminal; and the control unit acquires a measured value of the impedance of the electrode to be measured based on a voltage applied to the second terminal, a potential of the output terminal, and a resistance value of the feedback resistor, in a state where the first input terminal is connected to the first terminal. Measurement method.

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