Maintenance method and maintenance system of zirconia oxygen concentration meter

Abstract

The present invention provides a zirconia oxygen concentration meter and a maintenance method and system thereof. The maintenance of the zirconia oxygen concentration meter can be appropriately implemented. The maintenance method of the zirconia oxygen concentration meter is a method for measuring a measured gas using a zirconia sensor, the zirconia oxygen concentration meter stores at least one of an internal resistance value and a correction coefficient existing in the zirconia sensor in a storage unit, the correction coefficient is a coefficient used to correct a conversion formula for converting the measured value of the physical quantity of the zirconia sensor into the oxygen concentration of the measured gas based on the measured value of the physical quantity of the zirconia sensor measured for a standard gas with a known oxygen concentration, an information processing device determines a time when the zirconia sensor should be maintained based on a change over time of at least one of the internal resistance value and the correction coefficient stored in the storage unit, and the information processing device prompts a time when the zirconia sensor should be maintained.

Description

[0001] This application claims the benefit of priority based on Japanese Patent Application No. 2021-061832 filed in Japan on March 31, 2021, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0002] The present disclosure relates to a maintenance method and a maintenance system for a zirconia oxygen concentration meter. Background Art

[0003] Zirconia oxygen concentration meter is an oxygen concentration meter that uses the conductivity of zirconia element to oxygen ions at high temperature. Platinum electrodes are added to both sides of the zirconia element and heated. If gases with different oxygen partial pressures are brought into contact with each side of the zirconia element, the oxygen concentration cell function is generated. The zirconia oxygen concentration meter measures the electromotive force generated between the two electrodes through this function to measure the oxygen partial pressure on the measurement gas side.

[0004] The zirconia oxygen concentration meter deteriorates with long-term use, and the zirconia sensor produces an offset (drift) in the oxygen concentration. In order to maintain the correct display of the oxygen concentration, it is necessary to regularly flow a gas of known concentration to the measurement gas side to calibrate the electrical correction output. For example, Patent Document 1 describes a technique related to the calibration of a zirconia oxygen concentration meter.

[0005] By regularly performing such calibration, the zirconia oxygen meter is usually maintained in a normal state. However, when the zirconia sensor deteriorates, the drift effect cannot be fully corrected even with calibration, resulting in measurement failure and errors. If this happens, the zirconia sensor itself needs to be replaced.

[0006] Thus, it is necessary to perform maintenance such as calibration and replacement of the zirconium oxide sensor at appropriate timing. On the other hand, since maintenance work requires time and cost, it is desirable to suppress it to the necessary minimum.

[0007] However, it is known that the timing and content of necessary maintenance vary greatly depending on the environment in which the zirconia oxygen concentration meter is used. For example, the calibration cycle and sensor replacement timing of the zirconia oxygen concentration meter for process gas used in boilers or power plants largely depend on the usage environment such as the components, temperature and moisture contained in the measured gas. At present, the timing and content of maintenance are generally appropriately determined by the user according to the situation.

[0008]

Prior technical literature

[0009] [Patent Literature]

[0010] Patent Document 1: Japanese Patent Application Publication No. 2007-263933

[0011] However, since users have little knowledge and experience about the behavior of zirconia sensors, they are often unable to properly set the timing and content of appropriate maintenance. As a result, there are cases where users perform excessive calibration or sensor replacement, or continue to use the zirconia sensor until an error occurs, resulting in the shutdown of the equipment of the complete set of equipment.

[0012] Therefore, it is also considered that the manufacturer of the zirconia oxygen meter can recommend necessary maintenance to the user at an appropriate time. However, in order for the manufacturer to recommend appropriate maintenance, it is necessary to share detailed information such as the use environment, calibration status, and degree of sensor degradation of the zirconia oxygen meter, but in reality, it is difficult to share information from the start of equipment operation to replacement. Summary of the invention

[0013] An object of the present disclosure is to provide a maintenance method and a maintenance system for a zirconia type oxygen concentration meter, and a zirconia type oxygen concentration meter capable of appropriately performing maintenance of the zirconia type oxygen concentration meter.

[0014] According to several embodiments, a maintenance method of a zirconia type oxygen concentration meter is a maintenance method of a zirconia type oxygen concentration meter that uses a zirconia sensor to measure the oxygen concentration of a measured gas, wherein the zirconia type oxygen concentration meter stores at least one of an internal resistance value and a correction coefficient existing in the zirconia sensor in a storage unit, the correction coefficient being a coefficient for correcting a conversion formula for converting the physical quantity measured by the zirconia sensor into the oxygen concentration of the measured gas based on a physical quantity measured by the zirconia sensor for a standard gas having a known oxygen concentration, an information processing device determines a time when maintenance of the zirconia sensor should be performed based on a temporal change of at least one of the internal resistance value and the correction coefficient stored in the storage unit, and the information processing device prompts the time when maintenance of the zirconia sensor should be performed. In this way, since the time when maintenance should be performed determined based on at least one of the internal resistance value and the correction coefficient is prompted, the user performs maintenance at the prompted time, and the maintenance of the zirconia type oxygen concentration meter can be appropriately performed.

[0015] In the maintenance method of the zirconia oxygen concentration meter according to one embodiment, the information processing device approximates the change of the internal resistance value over time by a quadratic curve, and determines the time when the value of the internal resistance value estimated by the quadratic curve regarding the change of the internal resistance value over time reaches the upper limit value of the internal resistance value determined in advance as the time when the maintenance of the zirconia sensor should be performed. In this way, the change of the internal resistance value over time is approximated by a quadratic curve, and the time when the internal resistance value reaches the upper limit value is estimated by using the quadratic curve to determine the time when maintenance should be performed, so that the time when maintenance is required can be appropriately determined and prompted.

[0016] In the maintenance method of the zirconia oxygen concentration meter according to one embodiment, the information processing device approximates the change of the correction coefficient over time by a quadratic curve, and determines the time when the rate of change of the correction coefficient estimated by the quadratic curve reaches a predetermined upper limit of the rate of change as the time when the zirconia sensor should be calibrated. In this way, by approximating the change of the correction coefficient over time by a quadratic curve, estimating the time when the rate of change of the correction coefficient reaches the upper limit using the quadratic curve, and determining the time when the zirconia sensor should be calibrated, the time when maintenance is required can be appropriately determined and prompted.

[0017] In a maintenance method for a zirconia oxygen concentration meter according to one embodiment, the information processing device approximates the change of the correction coefficient over time by a quadratic curve, and determines the time when the variation range of the correction coefficient estimated by the quadratic curve reaches the upper limit of the variation range determined in advance as the time when the zirconia sensor should be replaced. In this way, the change of the correction coefficient over time is approximated by a quadratic curve, and the time when the variation range of the correction coefficient reaches the upper limit is estimated by using the quadratic curve to determine the time when the zirconia sensor should be replaced. Therefore, the time when maintenance is required can be appropriately determined and prompted.

[0018] In a maintenance method of a zirconia oxygen concentration meter according to one embodiment, the zirconia oxygen concentration meter determines a coefficient for correcting the conversion formula as the correction coefficient based on a first measurement value of the physical quantity measured by the zirconia sensor for a first standard gas having a known first oxygen concentration, i.e., a first measurement value, and a second measurement value of the physical quantity measured by the zirconia sensor for a second standard gas having a known second oxygen concentration, i.e., a second measurement value, and stores the determined correction coefficient in the storage unit. In this way, the correction coefficient is determined based on the measurement values ​​of the physical quantity measured by the zirconia sensor for two standard gases of different concentrations, and the period when maintenance should be performed is determined based on such a correction coefficient. Therefore, the period when maintenance is required can be appropriately determined and prompted.

[0019] According to some embodiments, a maintenance system for a zirconia oxygen meter includes: a zirconia oxygen meter that measures the oxygen concentration of a measured gas using a zirconia sensor; and an information processing device, wherein the zirconia oxygen meter stores at least one of an internal resistance value and a correction coefficient existing in the zirconia sensor in a storage unit, the correction coefficient being a coefficient for correcting a conversion formula for converting the physical quantity measured by the zirconia sensor into the oxygen concentration of the measured gas based on a physical quantity measured by the zirconia sensor for a standard gas having a known oxygen concentration, and the information processing device determines a time when maintenance of the zirconia sensor should be performed based on a temporal change of at least one of the internal resistance value and the correction coefficient stored in the storage unit, and prompts the time when maintenance of the zirconia sensor should be performed. In this way, since the time when maintenance should be performed determined based on at least one of the internal resistance value and the correction coefficient is prompted, the user performs maintenance at the prompted time, and maintenance of the zirconia oxygen meter can be appropriately performed.

[0020] According to some embodiments, the zirconia oxygen concentration meter is a zirconia oxygen concentration meter that uses a zirconia sensor to measure the oxygen concentration of a measured gas, and includes a control unit that measures an internal resistance value present in the zirconia sensor at a predetermined timing and stores the measured internal resistance value in a storage unit. Therefore, the change in the internal resistance value stored in the storage unit can be analyzed to appropriately determine the time and content of maintenance to be performed.

[0021] According to some embodiments, the zirconia type oxygen concentration meter is a zirconia type oxygen concentration meter that uses a zirconia sensor to measure the oxygen concentration of the measured gas, and includes a control unit, the control unit measures a physical quantity related to a standard gas having a known oxygen concentration through the zirconia sensor, calculates a correction coefficient based on the measured physical quantity and the known oxygen concentration, the correction coefficient being a coefficient for correcting a conversion formula for converting a measurement value of the physical quantity by the zirconia sensor into the oxygen concentration of the measured gas, and stores the calculated correction coefficient in a storage unit. Therefore, it is possible to analyze changes in the correction coefficient stored in the storage unit to appropriately determine the time and content of maintenance to be performed.

[0022] According to one embodiment of the present disclosure, it is possible to appropriately perform maintenance of the zirconia oxygen concentration meter. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a diagram showing a maintenance flow of the zirconia type oxygen concentration meter according to the comparative example.

[0024] Figure 2 It is a diagram showing a configuration example of a maintenance system according to an embodiment of the present disclosure.

[0025] Figure 3 Yes means Figure 2 A diagram showing an example of a configuration of a zirconia sensor.

[0026] Figure 4 Yes means Figure 2 A block diagram of an example of a converter configuration.

[0027] Figure 5 Yes means Figure 2 A block diagram of an example of the configuration of a management device.

[0028] Figure 6 It is a diagram showing a maintenance flow of the zirconia oxygen concentration meter in one embodiment.

[0029] Figure 7 This is a diagram for explaining calculation of a correction coefficient of a zirconia-type oxygen concentration meter.

[0030] Figure 8 It is a schematic diagram showing the electrical connection relationship between the zirconia sensor and the converter.

[0031] Fig. 9 This is a diagram for explaining the estimation of the replacement timing of the zirconia sensor.

[0032] Fig.10 It is a diagram showing a maintenance flow of the zirconia oxygen concentration meter in one embodiment.

[0033] Fig.11 It is a diagram showing a maintenance flow of the zirconia oxygen concentration meter in one embodiment.

[0034] Description of Reference Numerals

[0035] 1 zirconia oxygen concentration meter; 10 zirconia sensor; 11 zirconia tube; 12, 13 electrodes; 15 voltage source; 16 internal resistor; 17, 18 terminals; 20 converter; 21 control unit; 22 storage unit; 23 sensor unit; 231 shunt resistor; 232 switch; 233 measurement circuit; 24 HMI; 25 input / output unit; 26 communication unit; 30 gas bottle; 41 power cable; 42 gas cable; 43, 44 pressure reducing valve; 50 management device; 51 control unit; 52 storage unit; 53 communication unit; 54 input unit; 55 output unit; 100 maintenance system; G1 measured gas; G2 comparison gas; V out Electromotive force. DETAILED DESCRIPTION

[0036] <<Comparative Example>>

[0037] Figure 1 This is a diagram showing the maintenance process of the zirconia oxygen concentration meter involved in the comparative example. In the comparative example, when the manufacturer delivers the zirconia oxygen concentration meter equipment, the user starts the operation of the equipment. The user regularly calibrates according to his own judgment, but with continued use, the zirconia sensor gradually deteriorates. As the deterioration progresses, even if the calibration is performed, the influence of drift cannot be fully corrected, and eventually the measurement of the zirconia oxygen concentration meter will be erroneous. The user confirms the occurrence of the error and orders a new zirconia sensor from the manufacturer. The manufacturer accepts the order and delivers the new zirconia sensor. The user sets the new zirconia sensor and starts the operation of the equipment again. In the comparative example, such a cycle is repeated.

[0038] In the structure involved in the comparative example, the user calibrates the zirconia sensor according to his own judgment. However, the user's knowledge and experience regarding the maintenance of the zirconia sensor may not be sufficient, and the user may perform maintenance too frequently or not at a sufficient frequency. Figure 1 As in the maintenance process of the embodiment, the result of continuing to use the zirconia oxygen concentration meter until an error occurs may cause the equipment of the plant to stop. Thus, in the structure involved in the comparative example, there is also a case where appropriate maintenance cannot be performed.

[0039] <<Implementation Method>>

[0040] Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying drawings. In each of the drawings, the same reference numerals are attached to the same or corresponding parts. In the description of this embodiment, the description of the same or corresponding parts is appropriately omitted or simplified.

[0041] [First embodiment]

[0042] (Maintenance System)

[0043] Figure 2 1 is a diagram showing a configuration example of a maintenance system 100 according to an embodiment of the present disclosure. The maintenance system 100 includes a zirconia oxygen concentration meter 1 and a management device 50 as an information processing device in the present embodiment. The zirconia oxygen concentration meter 1 includes: a zirconia sensor 10, a converter 20, and a gas sealing bottle 30. The zirconia sensor 10 and the converter 20 are connected by a power cable 41. The zirconia sensor 10 and the gas sealing bottle 30 are connected by a gas cable 42 provided with pressure reducing valves 43 and 44. If each surface of the zirconia element of the zirconia sensor 10 contacts a gas with a different oxygen partial pressure, the action of an oxygen concentration cell is generated. The zirconia sensor 10 sends an electromotive force corresponding to the action to the converter 20 (hereinafter also referred to as a "unit electromotive force"). The converter 20 measures (calculates) the oxygen partial pressure of the measured gas based on the electromotive force and the oxygen partial pressure of the comparison gas. In addition, the converter 20 generates a log data file based on the calibration of the zirconia sensor 10 or the normal degradation diagnosis described later, and stores it in the storage unit 22 (see Figure 4 ).

[0044] The gas sealing bottle 30 is a supply source of a gas whose oxygen partial pressure value is known as a reference when measuring the oxygen partial pressure of the measured gas. The gas sealing bottle 30 stores, for example, a span gas and a zero gas, selects one of the gases as a comparison gas, and supplies it to the zirconia sensor 10. The span gas is a gas containing 20.95% oxygen and nitrogen, etc., and air is mainly used. The zero gas is a gas containing 0.51% oxygen and nitrogen, etc. The span gas and the zero gas can be used as standard gases with known oxygen concentrations.

[0045] The management device 50 is, for example, an information processing device for managing the maintenance of the zirconia oxygen concentration meter 1 maintained by the manufacturer of the zirconia oxygen concentration meter 1. The management device 50 determines the period when the maintenance of the zirconia sensor 10 should be performed based on the log data file generated by the converter 20, and prompts it. Here, the period when the maintenance should be performed may include the period when the zirconia sensor 10 should be calibrated and the period when the zirconia sensor 10 should be replaced. The management device 50 determines the calibration period and replacement period of the zirconia sensor 10, and determines the maintenance period based on the period. Therefore, according to the structure involved in this embodiment, since the user performs maintenance at the prompted period, the maintenance of the zirconia oxygen concentration meter can be appropriately performed.

[0046] Figure 3 Yes means Figure 2 FIG. 1 is a diagram showing an example of a configuration of a zirconia sensor 10 . Figure 3 The measurement principle of the zirconium oxide sensor 10 is shown in a cross-sectional view. Figure 3 In the embodiment, the zirconia sensor 10 has a zirconia tube 11 and electrodes 12 and 13 arranged on the inner and outer circumferences thereof. Generally, porous platinum electrodes are used for the electrodes 12 and 13. In the zirconia sensor 10 having such a structure, after the zirconia tube 11 is heated to a high temperature of about 750°C, the comparison gas G2 is made to flow to the outside of the tube (the comparison gas flow path), and the measured gas G1 is made to flow to the inside of the tube (the measured gas flow path). As a result, an electromotive force V corresponding to the oxygen concentration difference between the comparison gas G2 and the measured gas G1 is generated between the two electrodes 12 and 13. out The electromotive force V out The ratio of the oxygen concentration is proportional to the logarithm of the ratio. By using a gas with a known oxygen concentration such as air (for example, a span gas) as the comparison gas G2, it is possible to calculate the oxygen concentration of the reference gas G2 according to the electromotive force V out Specifically, when the temperature of the zirconia sensor 10 is 750°C, if the oxygen partial pressure of the measured gas G1 is P X , the oxygen partial pressure of the comparison gas G2 is set to P A , then based on the Nernst equation, P is given by the following [Formula 1] X .

[0047] [Formula 1]

[0048] P X =P A 10 －Vout / 50.74

[0049] Figure 4 Yes means Figure 2 The converter 20 includes a control unit 21, a storage unit 22, a sensor unit 23, an HMI (Human Machine Interface) 24, an input / output unit 25, and a communication unit 26.

[0050] The control unit 21 includes one or more processors. In one embodiment, the "processor" is a general-purpose processor such as a CPU (Central Processing Unit) or a dedicated processor specialized for a specific process, but is not limited to these. The control unit 21 is connected to each component of the converter 20 in a communicable manner to control the operation of the entire converter 20. The control unit 21 controls the operation of each component based on the application and data used to realize the function of the zirconia oxygen concentration meter 1. For example, the control unit 21 can control the operation of each component based on the electromotive force V of the zirconia sensor 10. outThe oxygen concentration is measured based on the size of the sensor, or a correction coefficient is calculated, or the internal resistance value of the zirconia sensor 10 is calculated, or the processing result is displayed on the display unit of the HMI 24.

[0051] The storage unit 22 includes any storage module including RAM (Random Access Memory), ROM (Read-Only Memory), HDD (Hard Disk Drive) and SSD (Solid State Drive). The storage unit 22 can function as a main storage device, an auxiliary storage device or a cache, for example. The storage unit 22 stores any information used for the operation of the converter 20 or obtained as a result of the operation of the converter 20. For example, the storage unit 22 can also store system programs, application programs, log data files, various data received from manufacturers, measurement data measured in the sensor unit 23, and various information received by the communication unit 26. The storage unit 22 is not limited to being built in the converter 20, and can also be an external database or external storage module such as an SD (Secure Digital) card or a USB (Universal Serial Bus) memory.

[0052] The sensor unit 23 measures the electromotive force V of the zirconia sensor 10. out The sensor unit 23 is connected to the zirconia sensor 10 . The structure of the sensor unit 23 for measuring the internal resistance of the zirconia sensor 10 will be described later. The data measured by the sensor unit 23 is stored in the storage unit 22 .

[0053] The HMI 24 is an interface with the user and includes an operation unit for accepting user operations, a display unit for displaying information related to maintenance such as the oxygen concentration measured by the zirconia sensor 10 and a calibration cycle, and the like.

[0054] The input / output unit 25 is an interface for inputting and outputting data to and from other devices or storage media. The input / output unit 25 includes, for example, an SD card slot, a USB interface, and the like.

[0055] The communication unit 26 includes any communication module that can communicate with other devices through any communication technology. The communication unit 26 may also include a communication control module for controlling communication with other devices and a storage module for storing communication data such as identification information required for communication with other devices. Hereinafter, an example in which the communication unit 26 is implemented by a communication device of a wireless LAN (Local Area Network) that can be connected to the Internet is described. However, the communication unit 26 may be a communication device that performs communication based on other communication methods including wired LAN or Bluetooth communication, for example.

[0056] Figure 5 Yes means Figure 2 The block diagram of the configuration example of the management device 50 is shown in FIG. The management device 50 is one or a plurality of server devices that can communicate with each other. Instead of such a configuration, the management device 50 may be any general electronic device such as a PC (Personal Computer) or other dedicated electronic device. Figure 5 As shown, the management device 50 includes a control unit 51 , a storage unit 52 , a communication unit 53 , an input unit 54 , and an output unit 55 .

[0057] The control unit 51 includes one or more processors. In one embodiment, the "processor" is a general-purpose processor or a dedicated processor specialized for a specific process, but is not limited thereto. The control unit 51 is connected to each component of the management device 50 in a communicable manner to control the operation of the entire management device 50.

[0058] The storage unit 52 includes any storage module including HDD, SSD, ROM, EEPROM (Electrically Erasable Programmable Read-Only Memory) and RAM. The storage unit 52 can function as a main storage device, an auxiliary storage device or a cache, for example. The storage unit 52 stores any information used in the operation of the management device 50 or obtained as a result of the operation of the management device 50. For example, the storage unit 52 can also store system programs, application programs, and various information received by the communication unit 53. The storage unit 52 is not limited to being built into the management device 50, and can also be an external database or an external storage module connected via a digital input and output interface such as USB.

[0059] The communication unit 53 includes any communication module that can communicate with the converter 20 of the zirconia oxygen concentration meter 1 or other devices such as the cloud through any communication technology. The communication unit 53 may also include a communication control module for controlling communication with other devices, and a storage module for storing communication data such as identification information required for communication with other devices.

[0060] The input unit 54 includes one or more input interfaces for receiving input operations from the user and obtaining input information based on the user's operations. For example, the input unit 54 is a physical key, an electrostatic capacitance key, a pointing device, a touch screen integrated with the display of the output unit 55, or a microphone for receiving voice input, but is not limited thereto.

[0061] The output unit 55 includes one or more output interfaces for outputting information to the user to notify the user. For example, the output unit 55 is a display that outputs information using images, or a speaker that outputs information using voice, but is not limited thereto. In addition, at least one of the input unit 54 and the output unit 55 may be integrally formed with the management device 50, or may be separately provided.

[0062] The functions of the management device 50 can be realized by executing a computer program (program) that can be used to make the maintenance system 100 involved in this embodiment function by the processor included in the control unit 51. That is, the functions of the management device 50 can be realized by software. The computer program causes the computer to realize the functions corresponding to the processing of each step by causing the computer to execute the processing of the steps included in the operation of the management device 50. That is, the computer program is a program for causing the computer to function as the management device 50 involved in this embodiment.

[0063] A computer program can be recorded on a computer-readable recording medium. Examples of computer-readable recording media include magnetic recording devices, optical disks, optical magnetic recording media, or semiconductor memories. The program can be circulated, for example, by selling, transferring, or lending portable recording media such as DVDs (digital versatile discs) or CD-ROMs (compact disc read only memory) on which the program is recorded. The program can be circulated by pre-storing the program in a server's memory and then forwarding the program from the server to other computers via a network. The program can be provided as a program product.

[0064] The computer temporarily stores, for example, a program recorded in a portable recording medium or a program forwarded from a server in a main storage device. In addition, the computer uses a processor to read the program stored in the main storage device and uses the processor to execute processing based on the read program. The computer can directly read the program from the portable recording medium and execute processing based on the program. The computer can successively execute processing based on the received program each time the program is forwarded from the server to the computer. It is also possible not to forward the program from the server to the computer, but only to implement functions based on execution instructions and results, so-called processing based on ASP (application service provider) type services. The program contains information for electronic computer processing and is based on the program. For example, data that is not a direct instruction to the computer but has the nature of specifying the computer's processing is equivalent to the "program-based portion."

[0065] A part or all of the functions of the management device 50 may be realized by a dedicated circuit included in the control unit 51. That is, a part or all of the functions of the management device 50 may be realized by hardware. In addition, the management device 50 may be realized by a single information processing device or by the cooperation of multiple information processing devices.

[0066] (Maintenance method of zirconia oxygen concentration meter)

[0067] Figure 6 1 is a diagram showing a maintenance flow of the zirconia oxygen concentration meter 1 according to one embodiment of the present disclosure. Figure 6 The operations of the zirconia oxygen meter 1 and the management device 50 described above correspond to the maintenance method according to the present embodiment. In the present embodiment, when the manufacturer delivers the zirconia oxygen meter 1 (S1), the user starts operating the device (S2).

[0068] After the operation starts, the zirconia oxygen concentration meter 1 involved in this embodiment performs normal degradation diagnosis on the zirconia sensor 10 and the like (S3). Normal degradation diagnosis refers to a process in which the control unit 21 of the converter 20 automatically measures the internal resistance value existing in the zirconia sensor 10 at a predetermined timing and stores the measured internal resistance value in the storage unit 22. As described later, it is known that the internal resistance value of the zirconia sensor 10 gradually increases with the use of the zirconia sensor 10. The zirconia oxygen concentration meter 1 can analyze the change in the internal resistance value and appropriately determine the time and content of maintenance by storing such internal resistance value in the storage unit 22 as a log data file.

[0069] In addition, after the operation starts, the user regularly calibrates the zirconia sensor 10 (S4). When calibrating the zirconia sensor 10, the control unit 21 of the converter 20 measures the physical quantity (for example, electromotive force, etc.) related to the standard gas with a known oxygen concentration through the zirconia sensor 10. The control unit 21 calculates the correction coefficient based on the measured physical quantity and the known oxygen concentration, and stores the calculated correction coefficient in the storage unit 22. The correction coefficient is a coefficient used to correct the conversion formula for converting the measured value of the physical quantity by the zirconia sensor 10 into the oxygen concentration of the measured gas. As described later, it is known that these correction coefficients gradually change with the use of the zirconia sensor 10. The zirconia oxygen concentration meter 1 stores the correction coefficients used in each such calibration as a log data file in the storage unit 22. As a result, it is possible to analyze the changes in the correction coefficients, and appropriately determine the period and content of maintenance based on the change range and change rate of the correction coefficients.

[0070] In order to appropriately determine the time and content of maintenance to be performed, the control unit 21 of the converter 20 can store information such as the calibration cycle and process measurement value in the storage unit 22 as a log data file in addition to the calibration coefficient and normal degradation diagnosis information. The calibration cycle is the time interval of the calibration of the zirconia sensor 10 performed by the user. The process measurement value is the electromotive force V measured by the zirconia sensor 10 during the operation of the zirconia oxygen concentration meter 1. out The measured value of the electromotive force V out The calculated oxygen concentration change data. Such log data files are taken out to the outside using a recording medium such as an SD card or a USB memory. The user obtains the log data files in an information processing device such as a PC, a tablet or a smart phone that can be connected to the Internet, and sends the log data files to the manufacturer via a WEB website provided by the manufacturer (S5).

[0071] The manufacturer analyzes the log data file received from the user (S6), and recommends a calibration cycle and a sensor replacement cycle to the user (S7). The details of the analysis of the log data file will be described later. The user calibrates the zirconia sensor 10 according to the recommended calibration cycle recommended by the manufacturer, and orders the zirconia sensor 10 according to the sensor replacement cycle (S8). When the zirconia sensor 10 is delivered (S9), the user sets the zirconia sensor 10 and starts the operation of the zirconia oxygen concentration meter (S10).

[0072] Thus, in the maintenance system 100 according to the present embodiment, the zirconia oxygen meter 1 performs normal degradation diagnosis on the zirconia sensor 10, etc., and records information such as the correction coefficient, normal degradation diagnosis information, correction cycle, and process measurement value as a log data file. Moreover, the management device 50 of the manufacturer recommends the user a recommended correction cycle and sensor replacement cycle based on this information. Therefore, according to the structure according to the present embodiment, the timing and content of the maintenance of the zirconia oxygen meter 1 can be appropriately determined and implemented.

[0073] (Maintenance management based on correction factor)

[0074] The electromotive force V is measured by using the measured gas G1 as the span gas or the zero gas and the reference gas G2 as the span gas. out The zirconia oxygen concentration meter 1 is calibrated. These span gas and zero gas are used as standard gases with known oxygen concentrations. That is, if the measured gas G1 is set as the span gas, the converter 20 is calibrated for the sensor output corresponding to the oxygen concentration of the span gas (span calibration). If the measured gas G1 is set as the zero gas, the converter 20 is calibrated for the sensor output corresponding to the oxygen concentration of the zero gas (zero point calibration).

[0075] Figure 7 This is a diagram for explaining the calculation of the correction factor of the zirconium oxide oxygen concentration meter. Figure 7 In the figure, the vertical axis represents the electromotive force (unit electromotive force) V of the zirconia sensor 10. out [mV]. The horizontal axis represents the oxygen concentration [vol %] of the gas G1 to be measured. The horizontal axis is displayed using a logarithmic scale.

[0076] exist Figure 7 In the formula, the corrected standard curve represents the theoretical standard curve corresponding to the straight line obtained by the following formula [Formula 2] obtained by deforming [Formula 1].

[0077] [Formula 2]

[0078] V out =-50.74·log(P X / P A )

[0079] Here, the oxygen partial pressure P of the measured gas G1 is X , Compare the oxygen partial pressure P of gas G2 A The calculation formula corresponding to the theoretical calibration curve can be used to calculate the response of the zirconia sensor 10 to a physical quantity (for example, the unit electromotive force V out The conversion formula for converting the measured value of (etc.) into the oxygen concentration of the measured gas.

[0080] like Figure 7 As shown, when the oxygen concentration value is expressed in a logarithmic scale, the correction standard curve is a straight line of (oxygen concentration [vol%], unit electromotive force [mV]) passing through the points of (20.95 [vol%], 0 [mV]) and (0.51 [vol%], 81.92 [mV]). The theoretical value (81.92 [mV]) of the unit electromotive force when the oxygen concentration of the measured gas is the zero gas concentration (0.51 [vol%]) is called the zero base point, and the theoretical value (0 [mV]) of the unit electromotive force when it is the span gas concentration (20.95 [vol%]) is called the span base point.

[0081] The standard curve before correction represents the characteristics of the unit electromotive force of the degraded zirconia sensor 10. Figure 7 In the example, when the oxygen concentration of the measured gas G1 is the span gas concentration (20.95 [vol %]), the degraded zirconia sensor 10 shows a unit electromotive force es [mV], and when it is the zero gas concentration (0.51 [vol %]), it shows a unit electromotive force ez [mV]. Figure 7 In the example, when the oxygen concentration of the measured gas is p1 [vol %], a unit electromotive force e1 [mV] larger than the theoretical value is observed. Therefore, if the oxygen concentration is calculated using the theoretical calibration curve based on the measured unit electromotive force, the calculated oxygen concentration deviates from the actual oxygen concentration.

[0082] The zirconia oxygen concentration meter 1 according to the present embodiment corrects and calibrates the oxygen concentration of the gas to be measured based on the deviation from the zero base point and the span base point of the calibration curve before correction. That is, the zirconia oxygen concentration meter 1 corrects the calibration curve before correction to the corrected calibration curve based on the measured value of the physical quantity (e.g., unit electromotive force) of the zirconia sensor 10 measured for the zero gas and the span gas as the standard gas. The ratio of the difference (B) between the unit electromotive force (ez) for the zero gas concentration and the unit electromotive force (es) for the span gas concentration of the calibration curve before correction expressed as a percentage to the difference (A) between the zero base point and the span base point in the theoretical calibration curve is called the zero point correction rate. The ratio of the unit electromotive force (C) for the span gas concentration of the calibration curve before correction expressed as a percentage to the difference (A) between the zero base point and the span base point in the theoretical calibration curve is called the span point correction rate. Here, A=81.92[mV], B=ez-es[mV], and C=es[mV]. That is, the zero point correction rate and the span point correction rate are expressed by the following [Formula 3].

[0083] [Formula 3]

[0084] Zero point correction rate = (B / A) × 100 (%)

[0085] Span point correction rate = (C / A) × 100 (%)

[0086] The zirconia oxygen meter 1 of the present embodiment calculates the above-mentioned zero point correction rate and span point correction rate as correction coefficients. The zirconia oxygen meter 1 uses the above-mentioned zero point correction rate and span point correction rate to calculate the oxygen concentration y [vol %] of the measured gas from the measured unit electromotive force E [mV] by the following [Formula 4].

[0087] [Formula 4]

[0088] y = 20.95 × 10 (E－Ks) / (-50.74×Kz)

[0089] Where, Kz = zero point correction rate / 100, Ks = span point correction rate × 81.92 / 100. z is called the zero correction factor, K s It is called the span point correction factor. Zero point correction factor and span point correction factor can also be used as correction factors.

[0090] In the zirconia sensor 10 that operates as in theory, the zero point correction rate is 100% and the span point correction rate is 0%. As the zero point correction rate and the span point correction rate move away from these theoretical values, the deterioration of the zirconia sensor 10 increases, and correction becomes difficult. In the present embodiment, a threshold value is set in advance for the difference from the theoretical value of the correctable zero point correction rate and span point correction rate. When the zero point correction rate or the span point correction rate exceeds the theoretical value and the threshold value and is different, it can be determined that the zirconia sensor 10 needs to be replaced. For example, the threshold value of the zero point correction rate can be set to 30%. In this case, the correctable range of the zero point correction rate is 70% to 130%. In addition, for example, the threshold value of the span point correction rate can also be set to 18%. In this case, the correctable range of the span point correction rate is 0% to 18%.

[0091] In addition, as the zirconia sensor 10 is used and the deterioration of the zirconia sensor 10 increases, the difference between the correction coefficients such as the zero correction rate and the span correction rate and their theoretical values ​​increases. Moreover, it is known that the difference between the correction coefficient and its theoretical value increases in the shape of a quadratic curve as time passes. Therefore, the management device 50 that receives the log data file containing the correction coefficient can approximate the change of the correction coefficient over time through a quadratic curve. Moreover, the management device 50 can determine the period when the change range of the correction coefficient estimated by the quadratic curve with respect to the change of the correction coefficient over time reaches the upper limit of the predetermined change range as the period when the zirconia sensor 10 should be replaced. For example, the upper limit of the change range of the zero correction rate can be set to 30%. The upper limit of the change range of the span correction rate can be set to 18%. In addition, the management device 50 can also determine the period when the change rate of the correction coefficient estimated by the quadratic curve with respect to the change of the correction coefficient over time reaches the upper limit of the predetermined change rate as the period when the zirconia sensor 10 should be calibrated. For example, the upper limit of the variation rate of the zero correction rate and the span correction rate can be set to a value between 0.2% and 0.5% (for example, 0.3%). In this way, the management device 50 approximates the change of the correction coefficient over time through a quadratic curve, and estimates the time when the zirconia sensor 10 should be replaced or calibrated, so that the time and content of the maintenance required can be appropriately determined and the user can be prompted. In addition, the determination of the time and content of the maintenance based on the change of the correction coefficient over time can use the log data file after more than three calibrations, so that the change of the correction coefficient over time can be more accurately estimated.

[0092] In addition, the zirconia oxygen concentration meter 1 determines the coefficient used to correct the conversion formula as a correction coefficient based on the measured values ​​of the physical quantity measured by the zirconia sensor 10 for the first and second standard gases with known oxygen concentrations, that is, the first and second measured values, and stores it in the storage unit 22. Such first and second standard gases can be set to the aforementioned zero gas and span gas, for example. In this way, the zirconia oxygen concentration meter 1 determines the correction coefficient based on the measured values ​​of the physical quantity measured by the zirconia sensor 10 for two standard gases with different concentrations, and determines the period when maintenance should be performed based on such correction coefficients. Therefore, according to the structure of this embodiment, the period when maintenance is required can be appropriately determined and prompted.

[0093] (Maintenance management based on internal resistance value)

[0094] Figure 8 Yes means Figure 2Schematic diagram of the electrical connection relationship between the zirconia sensor 10 and the converter 20. There are several items for evaluating the soundness of the zirconia sensor 10, but one of them is the internal resistance of the zirconia sensor 10. The internal resistance of a qualified zirconia sensor 10 is low, usually below 100Ω. However, if it is used continuously in actual gas, the internal resistance value of the zirconia sensor 10 tends to increase when the sensor characteristics deteriorate due to various factors such as contamination of the sensor electrode, cracks, or changes in the physical properties of the sensor. The internal resistance value of a degraded zirconia sensor 10 is generally more than several kΩ. Therefore, the zirconia oxygen concentration meter 1 involved in this embodiment can perform self-diagnosis of the internal resistance regularly (for example, once a week or a month) to confirm the soundness of the zirconia sensor 10.

[0095] Here, refer to Figure 8 As an example of a method for measuring internal resistance, a resistance shunt method will be described. Figure 8 Only excerpts and Figure 2 The parts related to the sensor signals of the zirconia sensor 10 and the converter 20 are shown. Figure 8 In FIG. 1 , the equivalent circuit of the zirconia sensor 10 is represented by an internal resistor 16 and a voltage source 15 connected in series. The voltage source 15 is a device that outputs an electromotive force V of the zirconia sensor 10. out The internal resistor 16 and the two terminals 17 and 18 of the voltage source 15 connected in series are connected to the measuring circuit 233 of the sensor unit 23 of the converter 20 via the power cable 41. Figure 8 In this way, the internal resistor 16 and the voltage source 15 connected in series with each other are connected in parallel with the shunt resistor 231 and the switch 232 connected in series with each other in the converter 20. The shunt resistor 231 and the switch 232 are also included in the sensor unit 23. The measuring circuit 233 measures the electromotive force V of the voltage source 15 observed when the shunt resistor 231 is electrically connected to the internal resistor 16 and the voltage source 15 and when the shunt resistor 231 is not electrically connected, based on the ON / OFF switching of the switch 232. out The resistance value of the internal resistor 16 is calculated based on the change in

[0096] In order to perform such a measurement, an electromotive force V of the voltage source 15 is required. out However, since the comparison gas G2 uses a span gas with the same composition as air, for example, when the measured gas G1 is an actual gas, the electromotive force V of the voltage source 15 is out Sometimes it becomes 0 mV or a low level close to 0 mV. In such a case, it is difficult to calculate the resistance value of the internal resistor 16 by the resistance shunt method. If zero gas is used as the measured gas G1, the electromotive force V of the zirconia sensor 10 is outWhen the resistance shunt method is used, the gas G1 to be measured is generally set to zero gas. If the internal resistance value of the zirconia sensor 10 is set to R cell , the electromotive force of the zirconia sensor 10 when zero gas is used as the measured gas G1 is V zero , the resistance value of the shunt resistor 231 is set to R s , and the voltage between the two terminals 17 and 18 when the switch 232 is turned on and the shunt resistor 231 is connected in parallel with the internal resistor 16 and the voltage source 15 is set to V cell , then the following [Formula 5] holds.

[0097] [Number 5]

[0098] R cell =(V zero -V cell )×Rs / V cell

[0099] The zirconia oxygen concentration meter 1 according to the present embodiment can measure the internal resistance value R of the zirconia sensor 10 at a predetermined timing by the above-mentioned principle. cell The measured value is stored in the storage unit 22. In addition, the method of measuring the internal resistance value of the zirconia sensor 10 is not limited to the resistance shunt method, and other methods may also be used. As described above, the internal resistance value R of the zirconia sensor 10 cell The value of can be sent to the management device 50 as a log data file and used by the management device 50 to estimate the sensor replacement cycle, etc.

[0100] As the deterioration of the zirconia sensor 10 increases due to the use of the zirconia sensor 10, the internal resistance value of the zirconia sensor 10 increases. Moreover, it is known that the internal resistance value increases in the shape of a quadratic curve over time. Therefore, the management device 50 that has received the log data file containing the internal resistance value can approximate the change of the internal resistance value over time by a quadratic curve. Moreover, the management device 50 can determine the period when the value of the internal resistance value estimated by the quadratic curve regarding the change of the internal resistance value over time reaches the upper limit of the internal resistance value determined in advance as the period when the maintenance of the zirconia sensor 10 should be performed. In this way, the management device 50 approximates the change of the internal resistance value over time by a quadratic curve, estimates the period when the maintenance of the zirconia sensor 10 should be performed, and can appropriately determine the period when maintenance is required and prompt the user.

[0101] Fig. 9 This is a diagram for explaining the estimation of the replacement period of the zirconia sensor 10. Fig. 9 In FIG. 1 , the horizontal axis represents time. The vertical axis represents the internal resistance value (sensor resistance) [Ω) of the zirconium oxide sensor 10. Fig. 9 The black dot curve represents the internal resistance value R of the zirconia sensor 10. cell The dotted curve is the internal resistance value R cell The approximate curve of the measured value. Fig. 9 In , the approximate curve is shown by a quadratic curve. Fig. 9 In the example, 3000Ω is set as the upper limit of the internal resistance value, and the zirconia sensor 10 is recommended for maintenance such as replacement at the recommended replacement time when the internal resistance value is predicted to reach 3000Ω. In addition, the period from the start of use of the zirconia sensor 10 to the recommended replacement time corresponds to the period of time for which the sensor is recommended to be replaced. In this way, the management device 50 can calculate the recommended replacement time and recommended replacement cycle of the zirconia sensor 10 based on the change in the internal resistance value over time, and prompt the user.

[0102] As described above, the maintenance system 100 according to the present embodiment includes: the zirconia oxygen meter 1 for measuring the oxygen concentration of the gas to be measured using the zirconia sensor 10, and the management device 50. The zirconia oxygen meter 1 stores at least one of the internal resistance value of the zirconia sensor 10 and the correction coefficient in the storage unit 22, the correction coefficient being a coefficient for correcting the conversion formula for converting the physical quantity measured by the zirconia sensor 10 into the oxygen concentration of the gas to be measured based on the measured value of the physical quantity measured for the standard gas. The management device 50 determines and prompts the time when the maintenance of the zirconia sensor 10 should be performed based on the change over time of at least one of the internal resistance value and the correction coefficient stored in the storage unit 22. In this way, since the time when the maintenance should be performed determined based on at least one of the internal resistance value and the correction coefficient is prompted, the user performs the maintenance at the prompted time, and the maintenance of the zirconia oxygen meter can be appropriately performed.

[0103] In the previous structure, in order to understand the user's calibration status and the degree of deterioration of the zirconia sensor 10, the user and the manufacturer need to share information in detail. In contrast, according to the structure involved in this embodiment, the user's use status of the zirconia oxygen concentration meter 1 can be easily grasped by simply handing over the log data file. In addition, according to the structure involved in this embodiment, the manufacturer can accept and analyze the log data file to suggest appropriate calibration cycles and sensor replacement timings to the user. Therefore, the user side can optimize the maintenance of the zirconia oxygen concentration meter 1. In addition, according to the structure involved in this embodiment, since the history related to the calibration of the zirconia oxygen concentration meter 1 and the change of the internal resistance value can be obtained as a log data file, data analysis can be performed with high precision, and maintenance can be appropriately implemented. In addition, according to the structure involved in this embodiment, regardless of the user's knowledge or experience related to the behavior of the zirconia sensor 10, appropriate calibration cycles and sensor replacement timings can be set. Therefore, it is possible to avoid reduction in work hours and costs due to excessive calibration and replacement of the zirconia sensor 10 , poor measurement values ​​due to delay in calibration timing, and equipment downtime due to delay in replacement of the zirconia sensor 10 , and the like.

[0104] [Second embodiment]

[0105] In the first embodiment, a log data file is taken out to the outside using a recording medium such as an SD card, and the user obtains the log data file in an information processing device such as a PC and sends it to the manufacturer via a WEB website. However, by automating the extraction and sending of such log data files, even if the user does not perform such operations, the time for calibration and replacement of the zirconia sensor 10 can be automatically prompted.

[0106] Fig.10 The details of the maintenance process of the zirconia oxygen concentration meter without such automated extraction and transmission of log data files are shown. When the user is configuring the zirconia oxygen concentration meter 1 (S11), the user operates HMI24 to output the log data file (S12). The user takes out the log data file (S13) and stores the log data in a storage medium such as an SD card (S14). The user obtains the log data file in an information processing device such as a PC that can be connected to the Internet, and sends the log data file to the manufacturer via a WEB website provided by the manufacturer (S15).

[0107] When the manufacturer receives the log data file (S16), the log data file is analyzed (S17), the analysis result is checked (S18), and the analysis result is sent to the user (S19). The analysis result is sent electronically via the Internet through e-mail or by mail. When the user receives the analysis result (S20), the content is reflected in the maintenance plan of the zirconia oxygen concentration meter 1 (S21).

[0108] Thus, if the maintenance of the zirconia oxygen meter 1 is not automated, manual work is required. In contrast, by automating the maintenance of the zirconia oxygen meter 1 , the work man-hours can be reduced.

[0109] Fig.11 The following is a flow chart of automated maintenance of the zirconia oxygen concentration meter 1. Fig.11 The operations of the zirconia oxygen concentration meter 1 and the management device 50 described above correspond to the maintenance method according to the present embodiment.

[0110] exist Fig.11 In the embodiment of the present invention, if the user performs a calibration operation (S31), the control unit 21 of the converter 20 automatically outputs a log data file (S32) and sends the log data file to the management device 50 managed by the manufacturer (S33). Based on the control of the control unit 21, the communication unit 26 such as a wireless LAN connected to the Internet sends the log data file.

[0111] If the control unit 51 of the management device 50 receives the log data file (S34), it analyzes the log data file (S35). The control unit 51 can control the management device 50 according to the pre-set program for analyzing the log data file described in the first embodiment, so as to analyze the log data file. The analysis result can include a recommended maintenance plan (maintenance period and content, etc.). After the analysis, the control unit 51 sends the analysis result to the converter 20 managed by the user (S36). Based on the control of the control unit 51, the communication unit 53 sends the analysis result.

[0112] When receiving the analysis result of the log data file (S37), the control unit 21 of the converter 20 displays the contents of the recommended maintenance schedule on the HMI 24 of the converter 20 (S38). The user reflects the displayed maintenance schedule in the maintenance of the zirconia oxygen meter 1 (S39).

[0113] Thus, by automating the operations of extracting log data and sending it to the manufacturer, and automatically notifying the user of the time for calibration and replacement of the zirconia sensor 10, manual operations can be reduced. Therefore, the operation man-hours can be reduced and human errors can be prevented.

[0114] [Other embodiments]

[0115] In the above-mentioned embodiment, the structure of determining the period and content of maintenance of the zirconia sensor 10 based on the change of the internal resistance value and the correction coefficient of the zirconia sensor 10 over time is described. However, the period and content of maintenance of the zirconia sensor 10 can also be analyzed and used by using machine learning techniques to analyze all data that are considered to be related to maintenance. Such data can include information such as the above-mentioned calibration cycle and process measurement values. In this way, information related to maintenance with higher accuracy can be provided.

[0116] The present disclosure is not limited to the above-mentioned embodiments. Multiple blocks recorded in the block diagram may be integrated into one, or one block may be divided. Instead of executing multiple steps recorded in the flowchart in a time series as described, the steps may be executed in parallel or in a different order according to the processing capability of the device executing each step or as needed. In addition, changes can be implemented within the scope of the main purpose of the present disclosure.

Claims

1. A maintenance method for a zirconia type oxygen concentration meter, the maintenance method being a maintenance method for a zirconia type oxygen concentration meter that uses a zirconia sensor to measure the oxygen concentration of a gas to be measured, The zirconia oxygen concentration meter stores the ratio of the difference between the unit electromotive force for the zero gas concentration and the unit electromotive force for the span gas concentration of the standard curve before correction to the difference between the zero base point and the span base point in the theoretical standard curve, and the ratio of the unit electromotive force for the span gas concentration of the standard curve before correction to the difference between the zero base point and the span base point in the theoretical standard curve as correction coefficients in a storage unit, wherein the correction coefficients are coefficients for correcting a conversion formula for converting the measurement value of the physical quantity of the zirconia sensor measured for the standard gas having a known oxygen concentration into the oxygen concentration of the measured gas based on the measurement value of the physical quantity of the zirconia sensor measured for the standard gas having a known oxygen concentration. The information processing device approximates the change over time of the correction coefficient stored in the storage unit by a quadratic curve, The time when the rate of change of the correction coefficient estimated by the quadratic curve with respect to the change over time of the correction coefficient reaches a predetermined upper limit value of the rate of change is determined as the time when the zirconia sensor should be calibrated. The time when the zirconia sensor should be calibrated is indicated.

2. The maintenance method of the zirconia oxygen concentration meter according to claim 1, wherein: The information processing device approximates the change over time of the internal resistance value existing in the zirconia sensor stored in the storage unit by a quadratic curve, A time when the internal resistance value estimated by the quadratic curve regarding the temporal change of the internal resistance value reaches a predetermined upper limit value of the internal resistance value is determined as a time when maintenance of the zirconia sensor should be performed.

3. The maintenance method of the zirconia oxygen concentration meter according to claim 1 or 2, wherein: The zirconia oxygen concentration meter determines a coefficient for correcting the conversion formula as the correction coefficient based on a first measurement value of the physical quantity measured by the zirconia sensor for a first standard gas having a known first oxygen concentration, i.e., a first measurement value, and a second measurement value of the physical quantity measured by the zirconia sensor for a second standard gas having a known second oxygen concentration, i.e., a second measurement value. The determined correction coefficient is stored in the storage unit.

4. The maintenance method of the zirconia oxygen concentration meter according to claim 1, wherein: The zero base point is the theoretical value of the unit electromotive force when the oxygen concentration of the measured gas is the zero gas concentration, i.e., 0.51 [vol %], and the span base point is the theoretical value of the unit electromotive force when the oxygen concentration of the measured gas is the span gas concentration, i.e., 20.95 [vol %].

5. The maintenance method of the zirconia oxygen concentration meter according to claim 1, wherein: The information processing device determines a time when the variation range of the correction coefficient estimated by the quadratic curve regarding the temporal variation of the correction coefficient reaches a predetermined upper limit value of the variation range as a time when the zirconia sensor should be replaced. The time when the zirconium oxide sensor should be replaced is indicated.

6. A maintenance system comprising: a zirconia oxygen concentration meter for measuring the oxygen concentration of a gas to be measured using a zirconia sensor, and an information processing device, The zirconia oxygen concentration meter stores the ratio of the difference between the unit electromotive force for the zero gas concentration and the unit electromotive force for the span gas concentration of the standard curve before correction to the difference between the zero base point and the span base point in the theoretical standard curve, and the ratio of the unit electromotive force for the span gas concentration of the standard curve before correction to the difference between the zero base point and the span base point in the theoretical standard curve as correction coefficients in a storage unit, wherein the correction coefficients are coefficients for correcting a conversion formula for converting the measurement value of the physical quantity of the zirconia sensor measured for a standard gas having a known oxygen concentration into the oxygen concentration of the measured gas, The information processing device approximates the change over time of the correction coefficient stored in the storage unit by a quadratic curve, The time when the rate of change of the correction coefficient estimated by the quadratic curve with respect to the change over time of the correction coefficient reaches a predetermined upper limit value of the rate of change is determined as the time when the zirconia sensor should be calibrated. The time when the zirconia sensor should be calibrated is indicated.

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