JP7260376B2 - Constant potential electrolytic gas sensor - Google Patents

Description

The present invention relates to a constant potential electrolysis gas sensor, and to correction of a calibration curve using a standard gas.

A constant potential electrolysis gas sensor consists of electrodes (working electrode and counter electrode) formed by applying a gas-permeable membrane to the side of an electrolyte tank containing an electrolyte, and platinum, which has a catalytic action, on the surface of the gas-permeable membrane. and a reference electrode placed in the electrolyte bath, and the potential difference between the working electrode and the reference electrode is kept constant by a potentiostat circuit. After passing through the gas-permeable membrane, the target gas is ion-exchanged at the working electrode, and accompanying this, a counter reaction occurs at the counter electrode, causing an electrolytic current to flow. Gas concentration is measured by utilizing the fact that this current is proportional to the target gas concentration.

In the constant potential electrolysis gas sensor having such a configuration, the volume of the electrolytic solution filled in the electrolytic solution tank may fluctuate due to changes in atmospheric pressure and ambient temperature. Sulfuric acid, which is often used as an electrolyte, is hygroscopic. When the gas sensor is placed in a high-humidity environment, the hygroscopicity of sulfuric acid takes in water vapor from the outside, increasing the amount of electrolyte and increasing the amount of electrolyte. increases in volume. Such volume fluctuations of the electrolytic solution cause fluctuations in the internal pressure in the electrolytic solution tank, which may cause fluctuations in the output of the electrolysis current.

In addition, the internal pressure fluctuation in the container due to the above-mentioned volume fluctuation of the electrolyte may cause leakage of the electrolyte near the electrode, and the electrolyte leaked to the lead terminal connected to the electrode may cause corrosion of the lead terminal. may result.

Events that can occur in a constant potential electrolysis gas sensor such as those described above cause a decrease in detection accuracy or impossibility of detection.

For example, Patent Literature 1 discloses a constant potential electrolysis type gas sensor in which a gas containing portion is provided in an electrolyte bath. With such a configuration, the gas contained in the gas containing portion absorbs the volume fluctuation of the electrolytic solution, and by reducing the fluctuation range of the internal pressure in the electrolytic solution tank, it is possible to prevent a decrease in detection accuracy and an impossibility of detection. .

JP-A-2002-71621

The constant potential electrolytic gas sensor has a detection range of several hundred ppb to several tens of ppm, and is extremely sensitive. In addition, it is possible to detect toxic gases such as carbon monoxide, hydrogen sulfide, silane, and arsine at low concentrations due to the feature that the selectivity of the gas to be detected is given by the set potential difference between the electrodes. It is often used as a portable gas sensor for On the other hand, the service life is relatively short, about one year.

Structural solutions to the problems caused by volume fluctuations of the electrolyte solution, such as providing an air containing portion in the electrolyte solution tank as in the invention of Patent Document 1, result in an increase in the size of the gas sensor, which impairs its portability. Moreover, providing a complex structure to a constant potential electrolysis gas sensor, which has a short service life of only one year, unnecessarily increases the cost relative to the number of years of use. Rather, it is more cost-effective to accurately grasp failures and abnormalities due to aged deterioration and use the gas sensor while replacing it with a new one.

Therefore, the present invention prevents deterioration in measurement accuracy by appropriately correcting the calibration curve for fluctuations in the output peculiar to constant potential electrolysis gas sensors, and prevents failures and abnormalities in the sensor due to fluctuations in the volume of the electrolyte. It is intended to accurately detect when it occurs.

In order to solve the above problems, in the present invention, a gas to be measured is reacted with molecules in a liquid solvent through a gas permeable membrane, and the current value and the gas concentration to be presented are determined according to the current value generated by the generated ions. is a constant potential electrolysis gas sensor that presents gas concentrations based on a calibration curve showing the relationship of, when correcting the calibration curve with a standard gas that does not substantially contain the gas to be measured, the current value according to the standard gas is A variation detection unit that detects the variation in the output by obtaining the output multiple times, a variation determination unit that determines whether the detected variation is within a predetermined width C so that it is not determined to be abnormal, and a standard gas. The first concentration to be compared with the specified value A used to determine whether the gas concentration to be presented based on the calibration curve is abnormal or whether the calibration curve should be corrected according to the value of the current a second concentration value comparison/judgment unit for comparing and judging the gas concentration to be presented with a prescribed value B which is greater than the prescribed value A and used for judging an abnormality of the gas sensor; A constant potential electrolysis gas sensor is provided having a control section for controlling the determination section for detection and a correction section for correcting the calibration curve according to the value of the current generated by the standard gas.

Further, in the constant potential electrolysis type gas sensor having the above configuration, the control unit has a constant potential electrolysis type having a first operation means for operating the variation determination unit and the first concentration value comparison determination unit in order unless an abnormality is determined. A gas sensor is provided.

Further, in the constant potential electrolysis gas sensor having the above configuration, the controller determines that the determination result of the first concentration value comparison/determination unit is abnormal or that the calibration curve must be corrected. provides a constant potential electrolytic gas sensor having a second operation means for subsequently operating the second concentration value comparison/determination unit.

Further, in the constant potential electrolysis gas sensor having the above configuration, the control unit operates the correction unit when the determination result of the second concentration value comparison determination unit is a determination result that the gas sensor is not abnormal. A potentiostatic electrolytic gas sensor having a third actuation means is provided.

Further, in the constant potential electrolysis gas sensor having the above configuration, the correction unit includes first correction means for correcting the calibration curve so that the gas concentration to be presented becomes 0 according to the value of the current generated by the standard gas. A constant potential electrolytic gas sensor is provided.

Further, in the constant potential electrolysis gas sensor having the above configuration, the correction unit corrects the calibration curve so that the value obtained by multiplying the gas concentration in the standard gas based on the current pre-correction calibration curve by a predetermined coefficient becomes the correction amount. A potentiostatic electrolytic gas sensor having a second compensation means is provided.

Further, in the constant potential electrolysis gas sensor having the above configuration, the correction unit has selection receiving means for receiving a selection of whether to perform the current correction by the first correcting means or the current correction by the second correcting means. A potential electrolytic gas sensor is provided.

According to the present invention, it is possible to provide a constant-potential electrolysis gas sensor that can prevent deterioration in detection accuracy due to volume fluctuations of the electrolytic solution, etc., and can accurately determine an abnormality of the gas sensor.

FIG. 2 is a conceptual diagram showing an example of the functional configuration of the constant potential electrolytic gas sensor of Embodiment 1; Conceptual diagram showing the basic configuration of a constant potential electrolytic gas sensor Conceptual diagram for explaining the predetermined width C Conceptual diagram showing the number of times the standard gas was measured and the gas concentration value at each measurement Conceptual diagram showing the number of times the standard gas was measured and the gas concentration value at each measurement FIG. 2 is a conceptual diagram showing an example of the hardware configuration of the constant potential electrolytic gas sensor of Embodiment 1; Flow chart showing an example of the flow of processing when correcting the calibration curve using a standard gas Flow chart showing another example of the flow of processing when correcting the calibration curve using a standard gas Flow chart showing another example of the flow of processing when correcting the calibration curve using a standard gas FIG. 2 is a conceptual diagram showing an example of the functional configuration of the constant potential electrolytic gas sensor of Embodiment 2; FIG. 11 is a conceptual diagram showing an example of the functional configuration of the constant potential electrolytic gas sensor of Embodiment 3; FIG. 10 is a conceptual diagram showing an example of the functional configuration of the constant potential electrolytic gas sensor of Embodiment 4; FIG. 10 is a conceptual diagram showing an example of the functional configuration of the constant potential electrolytic gas sensor of Embodiment 5; FIG. 11 is a conceptual diagram showing an example of the functional configuration of the constant potential electrolytic gas sensor of Embodiment 6; Conceptual diagram showing changes in gas concentration values to be presented when the calibration curve is corrected by the second correction means.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the present invention should not be limited to these embodiments in any way, and can be implemented in various forms without departing from the gist of the present invention.

In the first embodiment, claim 1 will be mainly described. In the second embodiment, claim 2 will be mainly described. In the third embodiment, claim 3 will be mainly described. In the fourth embodiment, claim 4 will be mainly described. Embodiment 5 mainly describes claim 5 . Embodiment 6 mainly describes claims 6 and 7 .
<Embodiment 1>
<Overview of Embodiment 1>

In the invention of the first embodiment, the variation in the gas sensor output before concentration conversion and the converted concentration value are compared with the respective specified values, and based on the result, correction of the calibration curve using the standard gas and determination of abnormality of the gas sensor are performed.
<Embodiment 1 Configuration>

FIG. 1 is a conceptual diagram showing an example of the functional configuration of the constant potential electrolytic gas sensor of this embodiment. As shown, the "constant potential electrolysis gas sensor" 0100 of this embodiment includes a "control section" 0101, a "variation detection section" 0102, a "variation determination section" 0103, and a "first concentration value comparison determination section." ' 0104 , a 'second density value comparison/judgment unit' 0105 , and a 'correction unit' 0106 .

Note that each functional configuration described below can be implemented as a combination of hardware and software. Specifically, if a computer is used, the CPU, main memory, bus, or secondary storage device (nonvolatile memory such as flash memory and SSD, storage media such as CD and DVD, and read drives for those media) etc.), input devices used for information input, printers, display devices, hardware components such as other external peripherals, interfaces for external peripherals, interfaces for communication, and to control those hardware driver programs, other application programs, user interface applications, and the like. Then, by arithmetic processing of the CPU according to the program developed on the main memory, input from the input device and other interfaces, etc., data held on the memory and hard disk are processed and accumulated, and each hardware and Instructions are generated to control the software. Alternatively, the functional blocks of the device may be realized by dedicated hardware. It may also include a gas introduction mechanism, a sensor installation structure, a chamber for measurement, or a gas flow path for measurement.

Moreover, each embodiment described in this specification can be realized not only as an apparatus, but also as a method, partly or wholly. Also, part of such a device can be configured as software. Furthermore, a software product used for causing a computer to execute such software and a recording medium on which the product is fixed are naturally included in the technical scope of each embodiment described in this specification (this specification the same throughout).

Before describing the configuration of each part described above, the basic configuration of the constant potential electrolysis type gas sensor will be described with reference to FIG.

The constant potential electrolytic gas sensor consists of a "gas permeable membrane" 0203 in which a "working electrode" 0202 is superimposed on the upper surface of a "plastic container" 0201 with an upper and lower opening, and a "gas permeable membrane" in which a "counter electrode" 0204 is superimposed on the lower surface of the container. 0205, and a "reference electrode" 0206 is placed in the container and filled with the liquid solvent of the electrolyte.

The gas-permeable membrane is a membrane that is permeable only to gas but not to liquid. For example, a porous membrane made of a fluorine resin such as a PTFE membrane (polytetrafluoroethylene membrane) is used. Electrodes such as the working electrode are formed by coating the surface of the gas-permeable membrane with metal particles having a catalytic action such as platinum or gold, or by kneading and firing such metal particles with a binder to form a thin film. It is configured by stacking the above on a gas permeable membrane.

A specific potential difference is maintained between the working electrode and the reference electrode using a potentiostat circuit. In such a state, as shown in the figure, when CO (carbon monoxide), which is the gas to be measured, comes into contact with the working electrode, the following chemical reactions occur at the working electrode and the counter electrode.
Working electrode: CO+H ₂ O→CO ₂ +2H ⁺ +2e ⁻
Counter electrode: 1/2O ₂ +2H ⁺ +2e ⁻ →H ₂ O
Total reaction: CO+1/ _2O2 → _CO2
This chemical reaction causes an electrolysis current to flow between the working electrode and the counter electrode, and this electrolysis current value can be obtained as an output, converted into a CO gas concentration value based on a predetermined calibration curve, and presented. By appropriately selecting the potential difference between the working electrode and the reference electrode and the electrolytic solution, it is possible to measure the concentration of not only CO gas but also various gases.

The present embodiment is characterized in the process of correcting the calibration curve using a standard gas that does not contain a measurement target gas such as CO gas in the constant potential electrolysis gas sensor as described above. Correction of the calibration curve using the standard gas is to correct the calibration curve so that the gas concentration of the measurement target gas presented by the gas sensor is 0 or close to 0 when the standard gas is measured. Each configuration shown in FIG. 1 will be described below. The timing for correcting the calibration curve using the standard gas is not particularly limited. For example, the correction may be performed based on an instruction input by the user, or may be performed automatically based on a predetermined schedule.

First, the 'controller' 0101 controls a variation determination section, a first density value comparison determination section, and a second density value comparison determination section, which will be described later, in order to detect an abnormality. For example, it controls the operation conditions and the operation order of each determination unit. Further, each determination unit may be configured to control the setting or change of a specified value used as a criterion for determination.

The 'variation detection unit' 0102 has a function of detecting variations in the output by obtaining an output corresponding to the current value of the standard gas a plurality of times at the calibration curve correction timing. The standard gas is a gas that does not contain the gas to be measured. uses air. A standard gas containing oxygen is used when measuring a gas that requires oxygen for a chemical reaction that produces an electrolytic current. Further, the current value by the standard gas refers to the electrolysis current value generated by exposing the working electrode to the standard gas. Also, the output according to the current value may be the current value itself, or may be a value obtained by converting the current value into a voltage value.

Variations in the output according to the current value due to the standard gas can be caused by errors in the gas sensor element itself, errors in AD conversion, errors in the amplifier circuit, and the like. It is normal for a gas sensor to have a certain amount of variation, but if the degree of variation exceeds the normal level, there is a possibility that the gas sensor is in an abnormal state such as failure or damage. is high. Therefore, the variation detection unit detects variations in the output so that the variation determination unit, which will be described later, determines an abnormality of the gas sensor. There are various specific aspects of variations in the output to be detected, and the variations correspond to the width C defined by the variation determination unit.

A 'variation determination unit' 0103 uses a predetermined width C for determining whether the variation in the output detected by the variation detection unit is abnormal or not, and determines whether the variation falls within the predetermined width C. have The predetermined width C is, for example, the width from the minimum value to the maximum value, the width from the first quartile to the third quartile, and the median value −σ It is specified by (standard deviation) to the central value + σ, etc.

FIG. 3 is a line graph showing the output values obtained a plurality of times in succession and the predetermined width C. As shown in FIG. The horizontal axis is the number of acquisitions of the output value, and the vertical axis is the output value. Note that the output value may be a current value or a voltage value. Also, since the output value varies depending on the sensor, the output values shown on the vertical axis are relative values for explanation.

As shown in the figure, there are many output values outside the range C among the 50 output values. Therefore, when such a variation in output value is detected, the variation determining section determines that the gas sensor is abnormal. More specifically, a predetermined percentage of the variation of the measurement points, such as 100% or 90%, is within the variation width C, which is the percentage of the variation range of the width C of the measurement points. A preferable ratio is about 90% to 100%. In addition, it can be judged that the standard deviation prescribed amount of the variation of the measurement points is within the width C of the variation. The standard deviation specified amount is represented, for example, by plus or minus 2 sigma or plus or minus 2.3 sigma. When the standard deviation is defined, the value is preferably within the range of plus or minus 2 sigma to plus or minus 3 sigma. Alternatively, it may be defined by the size of the standard deviation. It is how large the standard deviation is relative to the mean. If there is a large variation with respect to the average value, there is a high possibility that the gas sensor is abnormal. The standard deviation is preferably about 20% to 30% of the average value.

The ``first concentration value comparison/determination unit'' 0103 determines that the gas concentration to be presented is abnormal based on the calibration curve according to the value of the current generated by the standard gas, or determines whether the calibration curve should be corrected. It has a function of making a comparison with a specified value A that is used to make a judgment.

The gas concentration to be presented when the standard gas is introduced should be 0 ppm if it is assumed that the gas to be measured is not contained in the standard gas. Also, if the gas concentration contained in the standard gas is assumed in advance, the assumed gas concentration should be presented. Moreover, even if the measured gas concentration value deviates from the assumed gas concentration value, if the drift is within the allowable range of the gas sensor, the calibration curve can be corrected so that no problem can be measured. On the other hand, if the difference between the measured gas concentration value and the assumed gas concentration value exceeds the allowable drift range, it is determined that the measured gas concentration value is abnormal and the gas sensor is abnormal. .

The first concentration value comparison/judgment unit determines whether there is an abnormality in the gas sensor or whether correction of the calibration curve is necessary based on the difference between the displayed gas concentration value converted by the calibration curve by measuring the standard gas and the assumed gas concentration value described above. to judge. Then, a determination is made depending on whether the width of deviation from the assumed gas concentration value exceeds the specified value A. If the specified value plus or minus A (absolute value A) is exceeded, at least measures such as correction of the calibration curve are required. Give the user information that there is no choice but to do it.

FIG. 4 is a conceptual diagram showing the number of times the display gas concentration value of the standard gas is compared with the specified value A, and the display gas concentration value (ppm) at each comparison time. In this figure, it is assumed that the gas to be measured is not included in the standard gas, and the prescribed value A is set to "5 ppm". Here, since the prescribed value is a value that regulates the deviation width, it is judged to be abnormal or the calibration curve must be corrected when it exceeds the range of -5 ppm to +5 ppm. (Whether it is an abnormality judgment or a correction necessary judgment is determined according to a separate judgment standard.)

In the figure, the specified range is indicated by the shaded area, and the gas concentration values from 0 to 6 times fall within the specified range, but exceed that range at the time of the seventh comparison. The first concentration value comparison/judgment section judges that abnormality judgment or correction of the calibration curve should be performed based on the result of the seventh measurement. Such judgment may be made immediately when the range specified by the specified value is exceeded, or may be judged or judged when the result of exceeding the range occurs a predetermined number of times in succession. may

The 'second concentration value comparison/judgment unit' 0104 has a function of comparing and judging the gas concentration to be presented with a prescribed value B which is greater than the prescribed value A and is used to judge an abnormality of the gas sensor. FIG. 5 is a conceptual diagram showing the number of times the display gas concentration value converted by the calibration curve by measuring the standard gas is compared with the specified value B, and the display gas concentration value at each comparison time. Here, the specified value A is "5 ppm", and the specified value B is "20 ppm", which is larger than the specified value A. The specified value B is also a value that specifies the range of gas concentration values like the specified value A, and the range specified by the specified value B is from −20 ppm to +20 ppm. In the figure, the scale lines of −20 ppm and +20 ppm are indicated by thick dotted lines. In the figure, the displayed gas concentration value is a negative value, but this is a calculated value inside the gas sensor and is not actually presented to the gas sensor user. At least, a display such as "0 ppm" is displayed on the display that displays the gas concentration value, while the calibration curve correction necessity and the gas sensor abnormality determination are being performed. The same applies to the first density value comparison/determination section described above.

In the figure, the displayed gas concentration value at the 18th time is below -20 ppm, and the second concentration value comparison/determination unit determines that the gas sensor is abnormal when such a result is obtained. Based on this determination, it may be configured to display that the gas sensor is abnormal, or display a message to replace the gas sensor. Further, when the displayed gas concentration value exceeds the specified value A but does not exceed the specified value B, it can be understood that the calibration curve needs to be corrected although the gas sensor is not abnormal.

In this way, the second concentration value comparison/determination unit has the function of distinguishing between the situation that the gas sensor is abnormal and the situation that the calibration curve needs to be corrected. Also, the first concentration value comparison/determination unit can determine a situation where the gas sensor is not abnormal and correction of the calibration curve is unnecessary. Therefore, by the functions of the first concentration value comparison determination section and the second concentration value comparison determination section, it is possible to determine the above three situations that may occur in the gas sensor, in addition to the abnormality determination by the variation determination section.

The 'correction unit' 0106 has a function of correcting the calibration curve based on the value of the current generated by the standard gas. The execution of the correction is based on the determination result of the first density value comparison determination section and the determination result of the second density value comparison determination section. For example, the judgment result of the first concentration value comparison judgment unit is abnormal or the calibration curve must be corrected, and the judgment result of the second concentration value comparison judgment unit is that the gas sensor is abnormal. If not, correct the calibration curve. This is because the displayed gas concentration converted based on the value of the current generated by the standard gas and the calibration curve does not fall within the range of gas concentrations defined by the specified value A, and does not fall within the range of gas concentrations specified by the specified value B. This indicates that the calibration curve is to be corrected when the
<Embodiment 1 Hardware>

FIG. 6 is a conceptual diagram showing an example of the hardware configuration of the constant potential electrolytic gas sensor of this embodiment. As shown, the constant potential electrolysis gas sensor includes a CPU 0601, a nonvolatile memory (eg, ROM, SSD, etc.) 0602, a main memory 0603, an interface I/F 0604, and a constant potential electrolysis gas sensor via the I/F. gas sensor element 0605, a display 0606, and a system bus 0607 for exchanging signals therebetween.

The non-volatile memory stores a variation detection program for detecting variations in the output by obtaining an output corresponding to the current value of the standard gas a plurality of times, and a predetermined width C for preventing the detected variation from being determined to be abnormal. It determines whether the gas concentration to be presented is abnormal or whether the calibration curve needs to be corrected based on the variation determination program that determines whether it falls within the standard gas and the calibration curve according to the value of the current generated by the standard gas. a first concentration value comparison/judgment program for comparing and judging against a specified value A used to determine the gas concentration to be presented; A second concentration value comparison and judgment program for comparison and judgment, a control program for controlling the execution of the judgment program for detecting the abnormality, a correction program for correcting the calibration curve according to the value of the current generated by the standard gas, etc. Information such as various programs, calibration curves, specified values A, specified values B, and width C is held. In addition, the non-volatile memory holds current values generated by the standard gas obtained by executing each program described above, judgment results, and the like. The main memory expands and executes the programs stored in the non-volatile memory, makes judgments, corrects the calibration curve according to the judgment results, or notifies an abnormality of the gas sensor.
<Embodiment 1: Flow of processing>

FIG. 7 is a flow chart showing an example of the flow of processing in the case of correcting the calibration curve with the standard gas in the constant potential electrolysis gas sensor or determining the abnormality of the gas sensor. The following flow is based on the premise that the standard gas hardly contains the gas to be measured. As shown in the figure, first, by obtaining an output corresponding to the current value of the standard gas in the gas flowed through the gas flow path a plurality of times, variations in the output are detected (S0701). Then, it is determined whether or not the detected variation is within a predetermined width C for not determining that it is abnormal (S0702). If it does not fall within the width C, it is judged to be abnormal and reported (S0703). On the other hand, if it is within the width C, the display gas concentration of the measurement target converted from the output corresponding to the current value of the standard gas and the calibration curve is obtained (S0704). Then, it is determined whether the acquired absolute value of the display gas concentration is smaller than the specified value A (|gas concentration|<specified value A). (S0705). If the determination result is smaller than the specified value A, the process ends. On the other hand, if the determination result is that it is not less than the specified value A, it is determined whether the acquired absolute value of the display gas concentration is smaller than the specified value B (|gas concentration|<specified value B) (S0706). In the case of the determination result that it is smaller than the specified value B, the calibration curve is corrected (S0707), and the process ends. On the other hand, if the determination result is that the value is not smaller than the specified value B, it is determined that there is an abnormality and is reported (S0703), and the process ends.

In addition, the process of judging and reporting an abnormality differs depending on whether it is based on the result of determination using the width C or based on the result of determination using the specified value B. and so on.

FIG. 8 is a flow diagram showing another example of the flow of processing in the case of correcting the calibration curve with the standard gas in the constant potential electrolysis gas sensor or determining the abnormality of the gas sensor. As shown, first, the display gas concentration of the measurement target converted from the output corresponding to the current value of the standard gas and the calibration curve is obtained (S0801). Then, it is determined whether the acquired absolute value of the display gas concentration is smaller than the specified value A (|gas concentration|<specified value A). (S0802). In the case of the judgment result that the current value is smaller than the specified value A, the variation in the output is detected by obtaining the output corresponding to the current value of the standard gas for the gas flowed through the gas flow path a plurality of times (S0803). Then, it is determined whether or not the detected variation is within a predetermined width C for not determining that it is abnormal (S0804). If it fits within the width C, it ends. On the other hand, if it does not fit within the width C, it is judged to be abnormal and reported (S0805).

If the result of the comparison determination in S0802 is that it is not smaller than the specified value A, it is determined whether the acquired absolute value of the displayed gas concentration is smaller than the specified value B (|gas concentration|<specified value B) ( S0806). In the case of the determination result that it is not smaller than the specified value B, it is determined that there is an abnormality and notified (S0805), and the process ends. On the other hand, if the determination result is smaller than the specified value B, the above-described output variation is detected (S0807). Then, it is determined whether the detected variation is within the width C described above (S0808). If it does not fall within the width C, it is judged to be abnormal and reported (S0805). On the other hand, if it is within the width C, the calibration curve is corrected (S0809) and the process ends.

FIG. 9 is a flowchart showing yet another example. As shown, first, the display gas concentration of the measurement target converted from the output corresponding to the current value of the standard gas and the calibration curve is obtained (S0901). Then, it is determined whether the acquired absolute value of the display gas concentration is smaller than the specified value B (|gas concentration|<specified value B) (S0902). If the determination result is that it is not smaller than the specified value B, it is determined to be abnormal and reported (S0903), and the process ends. On the other hand, if the determination result is that it is smaller than the specified value B, it is determined whether the acquired absolute value of the display gas concentration is smaller than the specified value A (|gas concentration|<specified value A). (S0904). In the case of the determination result that the current value is smaller than the specified value A, an output corresponding to the current value of the standard gas is obtained a plurality of times in the gas flowed through the gas flow path to detect variations in the output (S0905). Then, it is determined whether or not the detected variation is within a predetermined width C for not determining that it is abnormal (S0906). If it does not fall within the width C, it is judged to be abnormal and reported (S0903). On the other hand, if it is within the width C, the process ends.

If the result of the comparison determination in S0904 is that it is not smaller than the specified value A, the above-described variation in output is detected (S0907). Then, it is determined whether the detected variation is within the width C described above (S0908). If it does not fall within the width C, it is judged to be abnormal and reported (S0903). On the other hand, if it is within the width C, the calibration curve is corrected (S0909), and the process ends.

Further, in the above flow, each determination process is performed by the control unit or the control program so that the determination using the width C, the determination using the specified value A, and the determination using the specified value B are performed in a series of flows. Although controlled, each determination process may be controlled to be performed as an individual process flow.
<Embodiment 1 effect>

According to the present embodiment, it is possible to correct the calibration curve as necessary for fluctuations in the output peculiar to the constant potential electrolysis type gas sensor, and to accurately detect the failure or abnormality of the gas sensor.
<Embodiment 2>
<Overview of Embodiment 2>

The constant potential electrolysis gas sensor of this embodiment is based on the first embodiment, and is configured so that the control unit operates the variation determination unit and the first concentration value comparison determination unit in that order unless an abnormality is determined.
<Embodiment 2 Configuration>

FIG. 10 is a conceptual diagram showing an example of the functional configuration of the constant potential electrolytic gas sensor of this embodiment. As shown, the "constant potential electrolysis type gas sensor" 1000 of this embodiment includes a "control section" 1001 having a "first operating means" 1007, a "variation detection section" 1002, and a "variation judgment section" 1003. , a 'first density value comparison/judgment unit' 1004 , a 'second density value comparison/judgment unit' 1005 , and a 'correction unit' 1006 . The configuration other than the control unit is the same as the configuration of the same name in the constant potential electrolysis type gas sensor of the first embodiment. Therefore, the control unit will be described here, and descriptions of other configurations will be omitted.

The 'first operation unit' 1007 has a function of operating the variation determination unit and the first density value comparison/determination unit in this order unless an abnormality is determined.

As described in the first embodiment, the variation determination unit performs determination using the width C, and when the variation is within the width C, it is not determined to be abnormal. Then, if it is determined that there is no abnormality, then the first density value comparison/determination unit that uses the specified value A for comparison and determination is operated. Therefore, when the result obtained by operating the variation determination section is a determination result indicating that there is an abnormality, the first density value comparison determination section is not operated.

The hardware configuration of the present embodiment can be implemented according to the hardware configuration of the first embodiment, and further, the first operation that operates unless an abnormality is determined in the order of the variation determination section and the first density value comparison determination section. It can be realized by holding a program and executing it as appropriate.

Also, the flow of processing in this embodiment is included in the flow of processing in the first embodiment described with reference to FIG. 7, so description thereof will be omitted.
<Embodiment 2 effect>

According to the present embodiment, when an abnormality is determined as a result of the determination based on the variation and the width C, the comparison determination between the gas concentration value and the specified value A is not performed. Therefore, the unnecessary operation of the first density value comparison/determination section can be omitted.
<Embodiment 3>
<Overview of Embodiment 3>

The constant potential electrolysis type gas sensor of this embodiment is based on the first or second embodiment, and the control unit operates the second concentration value comparison/judgment unit according to the judgment result of the first concentration value comparison/judgment unit. It is configured.
<Embodiment 3 Configuration>

FIG. 11 is a conceptual diagram showing an example of the functional configuration of the constant potential electrolytic gas sensor of this embodiment. As shown in the figure, the ``constant potential electrolysis gas sensor'' 1100 of this embodiment includes a ``control unit'' 1101 having a ``first operation means'' 1107 and a ``second operation means'' 1108, and a ``variation detection part'' 1102. , a 'variation determination unit' 1103 , a 'first density value comparison determination unit' 1104 , a 'second density value comparison determination unit' 1105 , and a 'correction unit' 1106 . The configuration other than the control unit is the same as the configuration of the same name in the constant potential electrolysis type gas sensor of the first or second embodiment. Therefore, the control unit will be described here, and descriptions of other configurations will be omitted.

The 'second operating means' 1108 operates the second concentration value comparison/judgment unit when the judgment result of the first concentration value comparison/judgment unit is abnormal or the judgment result indicates that the calibration curve must be corrected. It has a function to operate next.

As described in the first or second embodiment, the first concentration value comparison/judgment unit acquires the gas concentration to be presented based on the value of the current generated by the standard gas and the calibration curve. Then, by comparing the obtained gas concentration with the specified value A, it is determined whether the gas concentration is abnormal or correction of the calibration curve is necessary. When it is determined that the gas concentration is abnormal or that the calibration curve needs to be corrected, the second operation means further operates the second concentration value comparison/determination unit that uses the specified value B for comparison and determination.

The hardware configuration of this embodiment can be realized according to the hardware configuration of Embodiment 1 or 2, and the determination result of the first concentration value comparison determination unit is abnormal, or the calibration curve must be corrected. If the determination result is that the second density value comparison/determination unit is to be operated next, the second operation program is stored and executed as appropriate.

Also, the flow of processing in this embodiment is included in the flow of processing in the first embodiment described with reference to FIG. 7, so description thereof will be omitted.
<Embodiment 3 Effect>

If the result of comparison with the specified value A is that the gas concentration is not abnormal and the correction of the calibration curve is not necessary, the operation of the second concentration value comparison/judgment section is unnecessary. According to this embodiment, when the gas concentration is not abnormal and correction of the calibration curve is not required, the second operation means does not perform the operation in the second concentration value comparison/determination section.
<Embodiment 4>
<Overview of Embodiment 4>

The constant potential electrolysis gas sensor of this embodiment is based on any one of Embodiments 1 to 3, and is configured such that the control unit operates the correction unit according to the determination result of the second concentration value comparison/determination unit. .
<Embodiment 4 Configuration>

FIG. 12 is a conceptual diagram showing an example of the functional configuration of the constant potential electrolytic gas sensor of this embodiment. As shown, the "constant potential electrolysis gas sensor" 1200 of this embodiment has a "control section" 1201 having a "first operating means" 1207, a "second operating means" 1208, and a "third operating means" 1209. , a 'variation detection unit' 1202, a 'variation determination unit' 1203, a 'first density value comparison determination unit' 1204, a 'second density value comparison determination unit' 1205, and a 'correction unit' 1206. Become. The configuration other than the control section is the same as the configuration of the same name in the constant potential electrolysis type gas sensor according to any one of the first to third embodiments. Therefore, the control unit will be described here, and descriptions of other configurations will be omitted.

The 'third operation means' 1209 has a function of causing the control section to operate the correction section when the judgment result of the second concentration value comparison judgment section indicates that the gas sensor is not abnormal.

As described in the first to third embodiments, the second concentration value comparison/judgment unit compares the gas concentration to be presented with the specified value B based on the value of the current generated by the standard gas and the calibration curve. The third operating means operates the correcting section to correct the calibration curve when the result of the comparison indicates that the gas sensor is not abnormal.

The hardware configuration of this embodiment can be realized according to the hardware configuration of any one of Embodiments 1 to 3, and the control unit determines that the determination result of the second concentration value comparison determination unit is not an abnormality of the gas sensor. In the case of the judgment result, the third operation program for operating the correction unit is stored and executed as appropriate.

Also, the flow of processing in this embodiment is included in the flow of processing in the first embodiment described with reference to FIG. 7, so description thereof will be omitted.
<Embodiment 4 Effect>

When it is determined that the gas sensor is abnormal by comparison with the specified value B, the above notification should be performed and there is no need to correct the calibration curve. The third operating means of the present embodiment eliminates unnecessary calibration curve correction.
<Embodiment 5>
<Overview of Embodiment 5>

The constant potential electrolysis gas sensor of this embodiment is based on any one of Embodiments 1 to 4, and is configured so that the correction of the calibration curve by the correction unit is performed so that the gas concentration of the standard gas becomes 0. there is
<Embodiment 5 Configuration>

FIG. 13 is a conceptual diagram showing an example of the functional configuration of the constant potential electrolytic gas sensor of this embodiment. As shown, the ``constant potential electrolysis gas sensor'' 1300 of this embodiment includes a ``controller'' 1301, a ``variation detection part'' 1302, a ``variation determination part'' 1303, and a ``first concentration value comparison determination part. 1304 , a “second density value comparison/determination unit” 1305 , and a “correction unit” 1306 having a “first correction means” 1307 . Note that the control unit may have any one of the first to third operation means. The configuration other than the correction unit is the same as the configuration of the same name in the constant potential electrolysis type gas sensor of the first embodiment. Therefore, the correction unit will be described here, and descriptions of other configurations will be omitted.

The 'first correction means' 1307 has a function of correcting the calibration curve so that the gas concentration to be presented becomes 0 according to the value of the current generated by the standard gas.

When it is determined that the calibration curve needs to be corrected by the first concentration value comparison determination unit and the second concentration value comparison determination unit, the calibration curve is corrected by the first correction means, so that the gas to be presented Density errors are corrected.

The hardware configuration of this embodiment can be realized according to the hardware configuration of any one of Embodiments 1 to 4, and the gas concentration to be presented by the correction unit according to the value of the current generated by the standard gas is It can be realized by storing a first correction program for correcting the calibration curve so that it becomes 0 and executing it as appropriate. Also, the flow of processing in this embodiment is the same as the flow of processing in the first embodiment described with reference to FIG. 7, so description thereof will be omitted.
<Embodiment 5 Effects>

According to the constant potential electrolysis gas sensor of the present embodiment, when it is determined that the calibration curve needs to be corrected, the calibration curve is corrected, thereby correcting the error in the gas concentration to be presented.
<Embodiment 6>
<Overview of Embodiment 6>

The constant potential electrolysis type gas sensor of this embodiment is based on any one of Embodiments 1 to 5, and is configured so that the calibration curve is corrected by a correction amount corresponding to a predetermined coefficient.
<Embodiment 6 Configuration>

FIG. 14 is a conceptual diagram showing an example of the functional configuration of the constant potential electrolytic gas sensor of this embodiment. As shown, the ``constant potential electrolysis gas sensor'' 1400 of this embodiment includes a ``controller'' 1401, a ``variation detection part'' 1402, a ``variation judgment part'' 1403, and a ``first concentration value comparison judgment part. 1404 , a “second density value comparison/determination unit” 1405 , and a “correction unit” 1406 having a “first correction means” 1407 and a “second correction means” 1408 . Note that the control unit may have any one of the first to third operation means. The configuration other than the correction unit is the same as the configuration of the same name in the constant potential electrolysis type gas sensor of the first embodiment. Therefore, the correction unit will be described here, and descriptions of other configurations will be omitted.

The 'second correction means' 1408 has a function of correcting the calibration curve so that the value obtained by multiplying the gas concentration in the standard gas based on the calibration curve before correction this time by a predetermined coefficient becomes the correction amount.

For example, if the gas concentration X in the standard gas does not fall within the range specified by the specified value A and falls within the range specified by the specified value B, the first concentration value comparison determination unit and the second concentration value comparison The judgment unit judges that the calibration curve needs to be corrected. Here, when the calibration curve is corrected by the first correcting means in the fifth embodiment, the calibration curve is corrected so that the gas concentration of 0 is presented when the current value on which the gas concentration X is based is output. Corrections are made. This correction then presents a gas concentration of 0 based on the corrected calibration curve if the current value produced by the standard gas remains unchanged.

On the other hand, in the correction of the calibration curve by the second correcting means, correction is performed using a correction amount of 0.2X, which is the value obtained by multiplying the gas concentration X by a coefficient such as 20%. As a result, the electric power value converted to the concentration of 0.8X based on the calibration curve before correction is corrected to the calibration curve corresponding to the gas concentration of 0. With this correction amount, a deviation still remains between the output of the standard gas in the previous measurement and the calibration curve. Therefore, it is preferable to subsequently correct the calibration curve. In this case, a value obtained by multiplying 0.8X, which is the remaining deviation amount, by 20%, which is a coefficient, is corrected as a correction amount.

While performing stepwise correction in this manner, it is preferable to continue measuring the standard gas. For example, each time correction is performed, is it necessary to convert the current value of the standard gas into concentration based on the calibration curve at the start of correction, and correct the concentration value by the first concentration value comparison determination unit and the second comparison determination unit? to decide. Then, when it is determined that correction is necessary, correction is performed by the correction amount multiplied by the above-described coefficient. On the other hand, when it is determined that the correction is not necessary, the calibration curve is corrected so that the gas concentration corresponding to the current value on which the determination is based becomes 0, and the correction by the second correction means is terminated. . FIG. 15 is a conceptual diagram showing changes in gas concentration values to be presented when the calibration curve is corrected by the second correction means.

FIG. 15(a) shows the case where the coefficient is 20%, and FIG. 15(b) shows the case where the coefficient is 50%. The horizontal axis indicates the number of measurements of the standard gas, and the vertical axis indicates the gas concentration value converted according to the current value of the standard gas. is the gas concentration value corresponding to the power value at each measurement based on the calibration curve at the start of correction. That is, there is no change in the concentration of the gas to be measured in the actual standard gas. Plotted with square points in the figure are gas concentration values based on the calibration curve corrected for each measurement. In this case, the specified value A is set to 0.5 ppm.

As shown in FIG. 15(a), the gas concentration value to be presented in the fifth measurement is 5 ppm, which exceeds the specified value of 0.5 ppm, so it is determined that correction of the calibration curve is necessary. Then, 1 ppm, which is the value obtained by multiplying 5 ppm, which is the gas concentration value at this time, by a coefficient of 20%, becomes the correction amount. The gas concentration value to be presented by correcting this calibration curve is 4 ppm. Subsequently, even in the sixth measurement, the gas concentration values indicated by the circled points remain the values at which it is determined that the calibration curve needs to be corrected. Therefore, the calibration curve is corrected using the correction amount of 0.8 ppm, which is the value obtained by multiplying the remaining deviation amount of 4 ppm by the coefficient of 20%. The gas concentration value to be presented by this corrected calibration curve is 3.2 ppm. A series of corrections is terminated when the gas concentration value based on the calibration curve corrected by repeating the corrections in this way falls below the specified value A (15th time). On the other hand, as shown in FIG. 15(b), if the coefficient that defines the correction amount is increased, the number of measurements required until the gas concentration value falls within the specified value A decreases, and the series of corrections ends relatively quickly.

When a constant potential electrolytic gas sensor is exposed to a high-concentration measurement target gas that exceeds the measurement range, the measurement target gas may be adsorbed on the electrode and remain there temporarily. In this case, the gas concentration value based on the current value generated by the standard gas can become so high as to require correction of the calibration curve. is done. However, the influence of the remaining gas is temporary, and after the influence disappears, the gas concentration measurement value based on the corrected calibration curve contains an error, which is inconvenient. By reducing the coefficient and gently correcting the calibration curve, it is easy to use because large measurement errors are less likely to occur even for temporary effects such as exposure to high-concentration gases. On the other hand, when fluctuations in humidity, air pressure, etc. are expected during measurement, it is preferable to promptly correct the calibration curve according to the fluctuations, because this contributes to maintaining measurement accuracy.

By appropriately setting the coefficient that defines the correction amount, it is possible to correct the calibration curve suitable for the measurement environment and measurement mode. Further, the constant potential electrolysis gas sensor of the present embodiment may have a configuration for receiving the setting of the coefficient in the second correcting means.

Further, the correction unit may have selection reception means for receiving a selection of whether to perform the current correction by the first correction means described in the fifth embodiment or the second correction means to perform the current correction.

The hardware configuration of this embodiment can be realized according to the hardware configuration of any one of Embodiments 1 to 5, and the value obtained by multiplying the gas concentration in the standard gas according to the pre-correction calibration curve by a predetermined coefficient is It can be realized by storing a second correction program for correcting the calibration curve so as to obtain the correction amount and executing it as appropriate. Also, the flow of processing in this embodiment is the same as the flow of processing in the first embodiment described with reference to FIG. 7, so description thereof will be omitted.
<Embodiment 6 effect>

According to the constant potential electrolysis type gas sensor of this embodiment, the calibration curve can be corrected by the correction amount according to the coefficient.

0100 constant potential electrolytic gas sensor 0101 control unit 0102 variation detection unit 0103 variation determination unit 0104 first concentration value comparison determination unit 0105 second concentration value comparison determination unit 0106 correction unit

Claims (7)

The gas to be measured is allowed to react with the molecules in the liquid solvent through the gas permeable membrane, and the gas concentration is determined based on the calibration curve showing the relationship between the current value and the gas concentration to be presented according to the current value generated by the generated ions. A potentiostatic electrolytic gas sensor that presents
When correcting the calibration curve with a standard gas that contains almost no target gas,
a variation detection unit for detecting variations in the output by obtaining an output corresponding to the current value of the standard gas a plurality of times;
a variation determination unit that determines whether the detected variation is within a predetermined width C for not determining that the variation is abnormal;
a specified value A used to determine whether the gas concentration to be presented based on the calibration curve is abnormal or to correct the calibration curve according to the value of the current generated by the standard gas ; a first concentration value comparison/judgment unit that compares and judges the gas concentration to be presented ;
a second concentration value comparing/determining unit that compares and determines the gas concentration to be presented with a specified value B that is greater than the specified value A and is used to determine an abnormality of the gas sensor;
a control unit that controls the determination unit to detect the abnormality;
a correction unit that corrects the calibration curve according to the value of the current generated by the standard gas;
constant potential electrolytic gas sensor.

2. The constant potential electrolysis gas sensor according to claim 1, wherein the control unit has a first operation means for operating the variation determination unit and the first concentration value comparison/determination unit in order unless an abnormality is determined. The control unit causes the second concentration value comparison/judgment unit to operate next when the judgment result of the first concentration value comparison/judgment unit is abnormal or the judgment result indicates that the calibration curve must be corrected. 3. A constant potential electrolysis gas sensor according to claim 2, having two operating means. 4. The constant potential electrolysis according to claim 3, wherein the control unit has third operation means for operating the correction unit when the determination result of the second concentration value comparison/determination unit indicates that the gas sensor is not abnormal. formula gas sensor. 5. The correction unit according to any one of claims 1 to 4, wherein the correction unit has a first correction means for correcting the calibration curve so that the gas concentration to be presented according to the value of the current generated by the standard gas is 0. Constant potential electrolytic gas sensor. 6. Any one of claims 1 to 5, wherein the correction unit has second correction means for correcting the calibration curve so that the correction amount is a value obtained by multiplying the gas concentration in the standard gas based on the calibration curve before correction this time by a predetermined coefficient. 1. The constant potential electrolytic gas sensor according to 1. 7. The constant potential electrolysis system according to claim 6, wherein the correction unit has selection receiving means for receiving a selection of whether the current correction is to be performed by the first correcting means or the second correcting means is to perform the current correction. gas sensor.

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