Ion concentration measurement apparatus, ion concentration measurement program, ion concentration measurement method, measurement apparatus, and measurement method

Abstract

Provided is an ion concentration measurement apparatus 100 for measuring an ion concentration in a solution of interest, the apparatus 100 being provided with: an ion concentration sensor 10 which outputs an ion concentration signal that is a signal corresponding to the ion concentration in the solution; and an ion concentration estimation unit 33 which calculates a time-dependent change d1 between the ion concentrations C1 and C2 from ion concentration signals at time points of t1 and t2 that are different from each other, and estimates a stable value Cs at which the ion concentration indicates a stable value by using the time-dependent change d1 of the ion concentration.

Description

Ion concentration measuring device, ion concentration measuring program, ion concentration measuring method, measuring device, and measuring method

[0001] The present invention relates to an ion concentration measuring device, an ion concentration measuring program, an ion concentration measuring method, a measuring device, and a measuring method.

[0002] An ion concentration measuring device is immersed in a test liquid to measure the ion concentration of the test liquid. As shown in Patent Document 1, for example, an ion concentration measuring device of this type generates an electromotive force between the internal liquid of the electrode unit and the test liquid by immersing or contacting the electrode unit in the test liquid, and calculates the ion concentration of the test liquid based on the electromotive force. Since this electromotive force varies depending on the temperature of the test liquid, this ion concentration measuring device performs temperature compensation based on the temperature of the test liquid when calculating the ion concentration.

[0003] However, this ion concentration measuring device is known to have unstable ion concentrations for a certain time from the start of measurement when the device is immersed in or in contact with the test liquid, resulting in a waiting time until the ion concentration stabilizes. Furthermore, this ion concentration measuring device requires a waiting time until the temperature of the test liquid stabilizes, due to a temperature difference between the electrode unit and the test liquid when the electrode unit and the test liquid are immersed in or in contact with each other. Therefore, since the ion concentration stabilizes only after this waiting time has elapsed, it takes time for a stable ion concentration to be measured.

[0004] Furthermore, since the user determines whether the temperature and ion concentration of the test liquid have stabilized, the measurement accuracy varies depending on the user's skill. As a result, if a waiting time is required until the temperature and ion concentration of the test liquid have stabilized as described above, depending on the user's skill, it may be impossible to determine whether the temperature and ion concentration of the test liquid have stabilized.

[0005] JP 2012-211871 A

[0006] The present invention has been made to solve the above problems, and its main object is to complete the measurement of concentration within the time from the start of measurement until the concentration becomes stable.

[0007] That is, the ion concentration measuring device of the present invention is an ion concentration measuring device for measuring the ion concentration of a test liquid, comprising an ion concentration sensor that outputs an ion concentration signal corresponding to the ion concentration of the test liquid, and an ion concentration estimation unit that calculates a time change in the ion concentration from the ion concentration signals at different times and estimates a stable value at which the ion concentration stabilizes using the time change in the ion concentration. The ion concentration measurement program of the present invention is an ion concentration measuring program used in an ion concentration measuring device equipped with an ion concentration sensor that outputs an ion concentration signal corresponding to the ion concentration of the test liquid, comprising: an ion concentration estimation unit that calculates a time change in the ion concentration from the ion concentration signals at different times and estimates a stable value at which the ion concentration stabilizes using the time change in the ion concentration. The ion concentration measurement method of the present invention is an ion concentration measuring method used in an ion concentration measuring device equipped with an ion concentration sensor that outputs an ion concentration signal corresponding to the ion concentration of the test liquid, comprising: an ion concentration measurement unit that calculates a time change in the ion concentration from the ion concentration signals at different times and estimates a stable value at which the ion concentration stabilizes using the time change in the ion concentration.

[0008] With this configuration, the time change of the ion concentration is calculated from ion concentration signals at different times, and the stable value of the ion concentration is estimated using the time change of the ion concentration. Therefore, the stable value of the ion concentration is estimated regardless of whether the ion concentration is actually stable. By using the estimated stable value as the measured value of the ion concentration, the ion concentration measurement can be completed within the time from the start of measurement until the actual ion concentration stabilizes, thereby shortening the measurement time. Furthermore, because the ion concentration estimation unit estimates the stable value of the ion concentration, the user does not need to determine whether the ion concentration has actually stabilized. Therefore, the ion concentration measurement can be performed without relying on the user's skill.

[0009] It is preferable that the ion concentration measuring device further includes a temperature sensor that outputs a temperature signal that is a signal corresponding to the temperature of the test liquid, and the ion concentration estimation unit calculates the change in temperature over time from the temperature signals at different times, and estimates the stable value using the change in ion concentration over time and the change in temperature over time.

[0010] With this configuration, the stable value of the ion concentration is estimated using the time change in the ion concentration and the time change in the temperature of the test liquid, so the ion concentration can be measured from the start of measurement until the temperature of the test liquid stabilizes. Furthermore, since the stable value of the ion concentration is estimated using the time change in the temperature, by compensating for the temperature of the test liquid, the stable value of the ion concentration can be estimated more accurately than if only the time change in the ion concentration were used, thereby improving measurement accuracy.

[0011] It is desirable that the ion concentration measuring device further includes a degradation data storage unit that stores degradation data indicating a degradation state of the ion concentration sensor using the ion concentration signal output from the ion concentration sensor, and that the ion concentration estimation unit estimates the stable value using at least the change in the ion concentration over time and the degradation data.

[0012] Generally, when an ion concentration sensor deteriorates, the error in the ion concentration signal output by the ion concentration sensor increases, and it takes time for the ion concentration to stabilize. In the present invention, the ion concentration estimation unit estimates the stable value of the ion concentration using the time change in the ion concentration and the deterioration data, so that the stable value of the ion concentration can be obtained even when an error in the ion concentration signal occurs due to deterioration.

[0013] The ion concentration measuring device preferably further includes a reference data storage unit that stores reference data indicating the known ion concentration of the test liquid or the ion concentration of the test liquid measured by the ion concentration sensor, and a degradation data update unit that compares the reference data with the estimated stable value and updates the degradation data, wherein the degradation data storage unit acquires the degradation data updated by the degradation data update unit, and the ion concentration estimation unit estimates the stable value using the updated degradation data.

[0014] With this configuration, the degradation data update unit compares the reference data with the estimated stable value to update the degradation data, so that the degradation data stored in the degradation data storage unit indicates the updated degradation of the ion concentration sensor. Therefore, the ion concentration estimation unit estimates the stable value with high accuracy, because the degradation of the ion concentration sensor is updated.

[0015] The ion concentration measuring device further includes a degradation model creation unit that creates a degradation model representing the change in degradation of the ion concentration sensor over time based on the reference data and the estimated stable value, the degradation data update unit predicts and updates the degradation data based on the degradation model, the degradation data storage unit stores the degradation data predicted by the degradation data update unit, and the ion concentration estimation unit estimates the stable value using the predicted degradation data.

[0016] With this configuration, the deterioration data is predicted and updated based on the deterioration model created by the deterioration model creation unit, so the ion concentration estimation unit can estimate the ion concentration after a predetermined time has elapsed, such as the time of the next calibration, and the user can predict the calibration cycle of the ion concentration sensor based on the deterioration model. Furthermore, since the time when the ion concentration becomes stable is determined based on the deterioration state of the ion concentration sensor, by creating the deterioration model by the deterioration model creation unit, the deterioration data update unit can predict the time when the ion concentration becomes stable and update the deterioration data.

[0017] The ion concentration measuring device may be one that performs measurements by batch measurement in which the device is immersed in or brought into contact with the test liquid for each measurement.

[0018] When measuring ion concentrations by batch measurement, there is a problem that the ion concentration changes between immediately after immersion or contact with the test liquid and after a predetermined time has passed, requiring a waiting time until stable measurement can be performed. However, in the ion concentration measuring device of the present invention, the ion concentration estimation unit estimates the stable value of the ion concentration using the time change in ion concentration, so even in the case of batch measurement, ion concentration measurement can be performed between the start of measurement and when the ion concentration stabilizes.

[0019] The ion concentration estimation unit may estimate the stable value using a least squares method based on changes over time in the ion concentration at different times.

[0020] With this configuration, the stable value is estimated using the least squares method based on the time changes in the ion concentration at different times. Therefore, even if an error occurs in the ion concentration signal output by the ion concentration sensor, the error can be corrected to estimate the stable value.

[0021] The measuring device is a measuring device that measures a first element that indicates the concentration of a substance to be measured or a value related thereto, and includes a first sensor that outputs a first element signal that is a signal corresponding to the first element, a second sensor that outputs a second element signal that is a signal corresponding to a second element that indicates a parameter different from the first element, and a stable value estimation unit that estimates a first stable value at which the first element indicates a stable value, wherein the stable value estimation unit calculates a time change of the first element from the first element signals at different times, calculates a time change of the second element from the second element signals at different times, and estimates the first stable value using the time change of the first element and the time change of the second element. Further, a measurement method is applicable to a measurement device that measures a first element indicating the concentration of a substance to be measured or a value related thereto, the measurement device including a first sensor that outputs a first element signal corresponding to the first element, and a second sensor that outputs a second element signal corresponding to a second element indicating a parameter different from the first element, the measurement device calculating a time change of the first element from the first element signals at different times, calculating a time change of the second element from the second element signals at different times, and estimating a first stable value at which the first element is stable using the time change of the first element and the time change of the second element. With such a configuration, it is possible to obtain the same effects as the ion concentration measuring device according to the present invention.

[0022] According to the present invention as described above, it is possible to complete the concentration measurement from the start of the measurement until the concentration becomes stable.

[0023] FIG. 1 is a schematic diagram of an ion concentration measuring device according to one embodiment of the present invention; FIG. 2 is a flowchart of an ion concentration estimation method according to the same embodiment; FIG. 3 is a graph showing a method of estimating ion concentration and temperature according to the same embodiment; FIG. 4 is a graph showing a method of estimating ion concentration according to another embodiment; FIG. 5 is a schematic diagram of an ion concentration measuring device according to another embodiment; FIG. 6 is a flowchart of a method of estimating ion concentration according to another embodiment; FIG. 7 is a schematic diagram of an ion concentration measuring device according to another embodiment; and FIG. 8 is a graph showing a method of estimating ion concentration according to another embodiment.

[0024] An ion concentration measuring device according to one embodiment of the present invention will be described below with reference to the drawings. Note that in all of the drawings shown below, some parts may be omitted or exaggerated for clarity. Identical components are designated by the same reference numerals, and their description will be omitted where appropriate.

[0025] 1. Device Configuration The ion concentration measuring device 100 according to this embodiment measures the ion concentration of a sample liquid, and performs the measurement by batch measurement in which the device is immersed in or comes into contact with the sample liquid for each measurement.

[0026] 1, the ion concentration measuring device 100 includes a measuring device A having an elongated shape as a whole, and an information processing device B including a CPU and the like configured to be able to communicate with the measuring device A via wired or wireless communication. The measuring device A is provided with an ion concentration sensor 10 that detects the ion concentration of the test liquid, and a temperature sensor 20 that detects the temperature of the test liquid.

[0027] The ion concentration sensor 10 is provided at the tip of the measuring device A, and is immersed in or in contact with the test liquid to output an ion concentration signal that corresponds to the ion concentration of the test liquid. This ion concentration sensor 10 is a composite type that integrates a measurement electrode, which is an ion-selective electrode, with a reference electrode. In addition, a test liquid holder 11 is formed on the surface of the ion concentration sensor 10 to hold the test liquid so that the test liquid comes into contact with the surface.

[0028] The temperature sensor 20 is provided inside the measuring device A and outputs a temperature signal that corresponds to the temperature of the test liquid. The temperature sensor 20 is, for example, a thermistor, and detects the test liquid held in the test liquid holder 11 to determine the temperature of the test liquid.

[0029] The information processing device B receives the ion concentration signal and the temperature signal and processes these signals. Specifically, as shown in Fig. 1, the information processing device B has a data receiving unit 31 that receives signals from each sensor, a deterioration data storage unit 32 that stores deterioration data indicating the deterioration state of each sensor, and an ion concentration estimation unit 33 that estimates a stable value indicating a stable value of the ion concentration. The data received by the data receiving unit 31 is output to the deterioration data storage unit 32 and the ion concentration estimation unit 33.

[0030] The degradation data storage unit 32 stores degradation data for each sensor based on the data received by the data receiving unit 31. The degradation data is created when each sensor is calibrated by comparing a test solution of known ion concentration with the ion concentration based on the signal from each sensor. Here, examples of degradation data include the state of response sensitivity and asymmetry potential difference of each sensor. The created degradation data is stored in the degradation data storage unit 32 based on input from a user or a computing device such as a CPU. It is sufficient that degradation data for at least the ion concentration sensor 10 has been created.

[0031] The ion concentration estimation unit 33 estimates a stable value of the ion concentration based on signals from each sensor. The ion concentration estimation unit 33 acquires data from the data reception unit 31 and the degradation data storage unit 32, estimates the stable value of the ion concentration, and outputs the estimated value. Hereinafter, an ion concentration estimation method performed by the ion concentration estimation unit 33 will be described, as shown in FIG. 2 .

[0032] The ion concentration estimation unit 33 calculates a time change d1 in the ion concentration and a time change d'1 in the temperature from the ion concentration signal and the temperature signal at different times. Specifically, the ion concentration estimation unit 33 acquires the ion concentration signal and the temperature signal at time t1 from the data receiving unit 31 and calculates an ion concentration C1 and a temperature F1 from these signals. The ion concentration estimation unit 33 also calculates an ion concentration C2 and a temperature F2 at time t2 in the same manner. The ion concentration estimation unit 33 then calculates a time change d1 in the ion concentration and a time change d'1 in the temperature from time t1 to t2 by subtracting and dividing the ion concentration C1 and the temperature F1 at time t1 from the ion concentration C2 and the temperature F2 at time t2, respectively.

[0033] The ion concentration estimation unit 33 acquires the deterioration data of the ion concentration sensor 10 and the deterioration data of the temperature sensor 20 from the deterioration data storage unit 32. The ion concentration estimation unit 33 may acquire each deterioration data before calculating each time change, or may not acquire the deterioration data of each sensor.

[0034] The ion concentration estimation unit 33 estimates a stable ion concentration value Cs, which indicates a stable ion concentration value, based on the time change d1 of the ion concentration and the deterioration data of the ion concentration sensor 10. The ion concentration estimation unit 33 also estimates a stable temperature value Fs, which indicates a stable temperature value of the test liquid, based on the time change d'1 of the temperature and the deterioration data of the temperature sensor 20. Note that the stable ion concentration value Cs and stable temperature value Fs in this embodiment refer to the ion concentration and temperature when the difference between the ion concentration and temperature measured by each sensor is less than a predetermined value.

[0035] In this embodiment, as shown in FIG. 3 , the ion concentration estimation unit 33 uses a least squares method, such as the Levenberg-Marquardt method or the recursive least squares method, to create a prediction model that predicts changes in ion concentration and temperature over time from a time change d1 in ion concentration and a time change d'1 in temperature. Specifically, when creating the prediction model, the ion concentration estimation unit 33 calculates the rate of change of ion concentration and the rate of change of temperature from the time change d1 in ion concentration and the time change d'1 in temperature. Next, the ion concentration estimation unit 33 calculates the time ts at which the rates of change are estimated to stabilize based on the deterioration data of each sensor, and creates a prediction model of the ion concentration and temperature up to the time ts. Based on this prediction model and the deterioration data of each sensor, the ion concentration estimation unit 33 estimates a stable ion concentration value Cs indicating the ion concentration at the time ts and a stable temperature value Fs indicating the temperature at the time ts.

[0036] Furthermore, the ion concentration estimation unit 33 performs temperature compensation on the stable ion concentration value Cs based on the estimated stable temperature value Fs, and calculates a compensated stable value Cf, which is the temperature-compensated stable value of the ion concentration. Thereafter, the ion concentration estimation unit 33 transmits the compensated stable value Cf to the display unit 40, such as a display.

[0037] 2. Effects of the Present Embodiment According to the ion concentration measuring device 100 of the present embodiment, the ion concentrations C1 and C2 are calculated based on the ion concentration signals at different times t1 and t2, and the stable ion concentration value Cs is estimated using the time change d1 of the ion concentration calculated from the ion concentrations C1 and C2. Therefore, the stable ion concentration value Cs is estimated regardless of whether the ion concentration is stable or not, so that the ion concentration measurement can be completed in the transient state from the start of measurement until the ion concentration stabilizes. Furthermore, because the ion concentration estimation unit 33 estimates the stable ion concentration value Cs, the user does not need to determine whether the ion concentration has stabilized. Therefore, the ion concentration measurement can be performed without relying on the user's skill.

[0038] 3. Other Modified Embodiments The present invention is not limited to the above-described embodiments.

[0039] In this embodiment, the ion concentration estimation unit 33 estimates the stable value Cs of the ion concentration using the ion concentrations C1 and C2 and the deterioration data, but it is sufficient that the stable value Cs of the ion concentration is estimated using at least the ion concentrations C1 and C2.

[0040] In the present embodiment, the ion concentration estimation unit 33 performs temperature compensation on the stable ion concentration value Cs based on the estimated stable temperature value Fs. However, temperature compensation may not be performed on the stable ion concentration value Cs. In this case, the ion concentration estimation unit 33 estimates the stable ion concentration value Cs from the ion concentrations C1 and C2 and outputs the stable ion concentration value Cs to the display unit 40.

[0041] In this embodiment, the ion concentration and temperature are calculated from the ion concentration signal and temperature signal corresponding to times t1 and t2, but the ion concentration and temperature may be calculated from the respective signals at different times. For example, the ion concentration may be calculated from the ion concentration signals at times t1 and t2, and the temperature of the test liquid may be calculated from the temperature signals at times t'1 and t'2, which are different from times t1 and t2.

[0042] In the present embodiment, the estimated stable temperature value Fs is used to perform temperature compensation for the estimated stable ion concentration value Cs, but the timing for performing temperature compensation is not limited to this. For example, the ion concentration estimation unit 33 may first estimate the stable temperature value Fs, perform temperature compensation for the ion concentrations C1 and C2 corresponding to each ion concentration signal, and then calculate the stable ion concentration value Cs.

[0043] In this embodiment, the ion concentration estimation unit 33 estimates the ion concentration based on the time change d1 of the ion concentration, the time change d'1 of the temperature of the test liquid, and the degradation data, but the ion concentration estimation unit 33 may also estimate the ion concentration based on other parameters that indicate the electrochemical properties of the test liquid. For example, the ion concentration estimation unit 33 may also estimate the ion concentration based on the time change of the salt concentration of the test liquid.

[0044] In this embodiment, when using the least squares method, the ion concentration estimation unit 33 estimates the stable ion concentration value Cs from the ion concentrations C1 and C2 at two different times, t1 and t2. However, the stable ion concentration value Cs may also be estimated from the ion concentrations at three or more times. For example, as shown in FIG. 4 , the ion concentration estimation unit 33 may calculate the time change d2 of the ion concentration at times t2 and t3 in addition to the time change d1 of the ion concentration at times t1 and t2, and create a prediction model from the time changes d1 and d2 of the ion concentration to estimate the stable ion concentration value. Alternatively, the ion concentration estimation unit 33 may create prediction models from each of the time changes d1 and d2 of the ion concentration and calculate the stable ion concentration value corresponding to each prediction model. In this way, even if an error occurs in the ion concentration signal output by the ion concentration sensor, the time change of the ion concentration is calculated using other times, so the error can be corrected to estimate the stable value.

[0045] 5, the ion concentration measuring device 100 may further include a reference data storage unit 34 that stores reference data indicating a known ion concentration of a test liquid or an ion concentration of a test liquid measured by the ion concentration sensor 10, and a degradation data update unit 35 that compares the reference data with each estimated stable value and updates degradation data. Here, the reference data may be, for example, the ion concentration Ci when the ion concentration sensor 10 is calibrated or the ion concentration Ci measured by the ion concentration sensor 10, and the reference data storage unit 34 stores the ion concentration Ci.

[0046] The degradation data updating method is as shown in FIG. 6 . Specifically, when the ion concentration estimation unit 33 outputs the stable ion concentration value Cs, the degradation data updating unit 35 compares the response sensitivity of the ion concentration sensor 10 based on the ion concentration Ci in the reference data storage unit 34 and the stable ion concentration value Cs. If the difference in response sensitivity is within the reference range, the degradation data updating unit 35 updates the degradation data, outputs it to the degradation data storage unit 32, and ends the measurement. If the difference in response sensitivity is outside the reference range, the ion concentration sensor 10 is replaced and the measurement ends. As a result, the ion concentration estimation unit 33 uses the updated degradation data in the next measurement, allowing for accurate estimation of the stable value.

[0047] 7 , the ion concentration measuring device 100 may further include a deterioration model creating unit 36 ​​that creates a deterioration model representing changes in deterioration over time of the ion concentration sensor 10 based on the reference data and the estimated stable value Cs of the ion concentration. In this case, the deterioration data updating unit 35 updates the deterioration data based on the created deterioration model. Then, the ion concentration estimating unit 33 estimates the ion concentration based on the predicted deterioration data.

[0048] Specifically, as shown in FIG. 8 , the degradation model creation unit 36 ​​creates a degradation model D1 that indicates a change over time in the sensitivity of the ion concentration sensor 10 in the reference data. Then, when an estimated stable value Cs is output at time t1, the degradation model creation unit 36 ​​compares the sensitivity Y1 of the ion concentration sensor 10 in the reference data with the sensitivity Y1a of the ion concentration sensor 10 at the estimated stable value Cs, and creates a new degradation model D2. Specifically, the degradation model D2 may be created by, for example, calculating a ratio α of the sensitivity Y1a to the sensitivity Y1 and multiplying the degradation model D1 by this ratio. Note that the degradation model is not limited to a change over time in the sensitivity of the ion concentration sensor 10, but may also be a change over time in an abnormal potential of the ion concentration sensor 10.

[0049] The degradation data update unit 35 then predicts and updates the degradation data, for example, at time ts when the ion concentration stabilizes, based on the new degradation model D2. The updated degradation data is stored in the degradation data storage unit 32, and the ion concentration estimation unit 33 uses the updated degradation data to estimate the stable value Cs of the ion concentration.

[0050] This allows the ion concentration estimation unit 33 to estimate the ion concentration after a predetermined time has elapsed, and also allows the user to predict, based on the deterioration model, the calibration cycle of the ion concentration sensor 10. Furthermore, since the time at which the ion concentration will stabilize is estimated based on the deterioration data of the ion concentration sensor 10, the deterioration model creation unit 36 ​​creates a deterioration model, which allows the deterioration data update unit 35 to predict the time at which the ion concentration will stabilize and update the deterioration data.

[0051] In this embodiment, the ion concentration of the test liquid is measured, but the parameter to be measured is not limited to ion concentration and may be a first element indicating the concentration of the substance to be measured or a value related thereto. In this case, the measurement device for measuring the first element includes a first sensor that outputs a first element signal that is a signal corresponding to the first element, a second sensor that outputs a second element signal that is a signal corresponding to a second element that indicates a parameter different from the first element, and a stable value estimation unit that estimates a first stable value indicating a stable value of the first element, wherein the stable value estimation unit calculates a time change of the first element from the first element signal at different times, calculates a time change of the second element from the second element signal at different times, and estimates the first stable value using the time change of the first element and the time change of the second element.

[0052] Here, the measurement object constituting the first element may be any of gas, liquid, or solid. When the measurement object is gas, the parameters include the concentration of exhaust gas, the concentration of process gas, the concentration of air, the concentration of gas components in dust, or the concentration of element components. Specifically, NO Ｘ , S.O. Ｘ , CO ２ , THC, NH ３ , N.H. ４ , CO, CH ４, PM2.5, O ３ , H ２ Examples of parameters when the object to be measured is a liquid include total nitrogen, total phosphorus, organic oxygen concentration (TOC), biochemical oxygen demand (BOD), chemical oxygen demand (COD), liquid electrical conductivity, liquid electrical resistivity, liquid turbidity, liquid color, residual chlorine concentration, peracetic acid concentration, silica concentration, and dissolved gases such as dissolved oxygen and dissolved carbon dioxide. Examples of parameters when the object to be measured is a solid include element concentration or component concentration in the solid. Note that the form of the object to be measured may be different from the form at the time of sampling.

[0053] Furthermore, parameters indicating the second element include temperature, air temperature, pressure, humidity, light intensity, illuminance, voltage value, current value, pulse number, carbon dioxide concentration, impedance, or flow rate.

[0054] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention.

[0055] According to the present invention, the concentration measurement can be completed within the time from the start of the measurement until the concentration becomes stable.

[0056] REFERENCE SIGNS LIST 100: Ion concentration measuring device 10: Ion concentration sensor 20: Temperature sensor 32: Deterioration data storage unit 33: Ion concentration estimation unit 34: Reference data storage unit 35: Deterioration data update unit Cs: Stable value of ion concentration d1: Time change in ion concentration d'1: Time change in temperature

Claims

1. An ion concentration measuring device for measuring the ion concentration of a test liquid, an ion concentration sensor that outputs an ion concentration signal that is a signal corresponding to the ion concentration of the test liquid; an ion concentration estimation unit that calculates a change in the ion concentration over time from the ion concentration signals at different times, and estimates a stable value at which the ion concentration stabilizes, using the change in the ion concentration over time.

2. a temperature sensor that outputs a temperature signal corresponding to the temperature of the test liquid; 2. The ion concentration measuring device according to claim 1, wherein the ion concentration estimating unit calculates a time change of the temperature from the temperature signals at different times, and estimates the stable value using the time change of the ion concentration and the time change of the temperature.

3. a degradation data storage unit that stores degradation data indicating a degradation state of the ion concentration sensor using a signal output from the ion concentration sensor; The ion concentration measuring device according to claim 1 , wherein the ion concentration estimating unit estimates the stable value using at least the time change of the ion concentration and the deterioration data.

4. a reference data storage unit that stores reference data indicating a known ion concentration of the test liquid or an ion concentration of the test liquid measured by the ion concentration sensor; a degradation data update unit that compares the reference data with the estimated stable value and updates the degradation data; the degradation data storage unit stores the degradation data updated by the degradation data update unit; The ion concentration measuring device according to claim 3 , wherein the ion concentration estimating unit estimates the stable value using the updated deterioration data.

5. a deterioration model creating unit that creates a deterioration model representing a time-dependent change in deterioration of the ion concentration sensor based on the reference data and the estimated stable value; the degradation data update unit predicts and updates the degradation data based on the degradation model; the degradation data storage unit stores the degradation data predicted by the degradation data update unit; The ion concentration measuring device according to claim 4 , wherein the ion concentration estimating unit estimates the stable value using predicted deterioration data.

6. 3. The ion concentration measuring device according to claim 1, wherein the measurement is performed by batch measurement in which the device is immersed in or contacted with the test liquid for each measurement.

7. The ion concentration measuring device according to claim 1 , wherein the ion concentration estimating unit estimates the stable value using a least squares method based on time variations of the ion concentration at different times.

8. An ion concentration measurement program used in an ion concentration measurement device having an ion concentration sensor that outputs an ion concentration signal corresponding to the ion concentration of a test liquid, an ion concentration measurement program that causes a computer to function as an ion concentration estimation unit that calculates a change over time in the ion concentration from the ion concentration signals at different times, and estimates a stable value at which the ion concentration stabilizes, using the change over time in the ion concentration.

9. An ion concentration measurement method used in an ion concentration measurement device equipped with an ion concentration sensor that outputs an ion concentration signal corresponding to the ion concentration of a test liquid, comprising: An ion concentration measurement method comprising: calculating a time change in the ion concentration from the ion concentration signals at different times; and estimating a stable value at which the ion concentration stabilizes using the time change in the ion concentration.

10. A measuring device for measuring a first element that indicates the concentration of a substance to be measured or a value related thereto, a first sensor that outputs a first element signal that is a signal according to the first element; a second sensor that outputs a second element signal that is a signal corresponding to a second element that indicates a parameter different from the first element; a stable value estimation unit that estimates a first stable value indicating a stable value of the first element, The stable value estimation unit a measurement device that calculates a time change of the first element from the first element signals at mutually different times, calculates a time change of the second element from the second element signals at mutually different times, and estimates the first stable value using the time change of the first element and the time change of the second element.

11. A measurement method used in a measurement device that measures a first element that indicates the concentration of a measurement object or a value related thereto, comprising: The measuring device is a first sensor that outputs a first element signal that is a signal according to the first element; a second sensor that outputs a second element signal that is a signal according to a second element that indicates a parameter different from the first element; A measurement method comprising: calculating a time change of the first element from the first element signals at mutually different times; calculating a time change of the second element from the second element signals at mutually different times; and estimating a first stable value, at which the first element is stable, using the time change of the first element and the time change of the second element.