Control method for gas detectors and gas sensors

Abstract

To provide a gas detector suitable for use in harsh environments where gas sensors are prone to degradation, while suppressing an increase in the number of parts and the size of the equipment. [Solution] This gas detector 100 is a gas detector that detects a target gas, and comprises a sensor unit 1 including a plurality of gas sensors 10 of the same type provided on the same substrate 14, and a control unit 2 that detects the target gas based on the output values ​​30 of the plurality of gas sensors 10, and the control unit 2 is configured to perform control to correct the output value 30 of a gas sensor 10 that has deteriorated based on the output values ​​30 of the plurality of gas sensors 10.

Description

Technical Field

[0001] This invention relates to a gas detector and a method for controlling a gas sensor.

Background Art

[0002] Conventionally, gas detectors have been known (see, for example, Patent Document 1).

[0003] Patent Document 1 discloses a substance detection device (gas detector) including a matrix sensor having a plurality of sensor units. In this gas detector, it is determined whether or not the sensor unit is deteriorated, and when it is determined that the sensor unit is deteriorated, an unused sensor unit among the plurality of sensor units is configured to be used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the substance detection device (gas detector) described in Patent Document 1, when it is determined that the sensor unit (gas sensor) is deteriorated, the gas sensor is not used. Therefore, when the gas detector is installed in a harsh environment where the gas sensor is likely to deteriorate, the degree of progress of deterioration of each gas sensor is accelerated. Thus, the replacement timing of the matrix sensor (sensor unit) is earlier with the same number of sensors as in the prior art. In addition, in order to extend the replacement timing, it is necessary to increase the number of sensors, which causes inconveniences such as an increase in the number of parts (cost increase) and enlargement of the device. Therefore, there is an inconvenience that it is not suitable for use in a harsh environment. Thus, there is a demand for a gas detector and a method for controlling a gas sensor that are suitable for use in a harsh environment where the gas sensor is likely to deteriorate while suppressing an increase in the number of parts and enlargement of the device.

[0006] This invention was made to solve the above-mentioned problems, and one of its objectives is to provide a gas detector and a gas sensor control method suitable for use in harsh environments where gas sensor degradation is likely to occur, while suppressing an increase in the number of parts and an increase in the size of the equipment. [Means for solving the problem]

[0007] To achieve the above objective, the gas detector according to the first aspect of this invention is a gas detector for detecting a target gas, comprising a sensor unit including a plurality of gas sensors of the same type provided on the same chip, and a control unit for detecting a target gas based on the output values ​​of the plurality of gas sensors, wherein the control unit is configured to perform control to correct the output value of a degraded gas sensor based on the output values ​​of the plurality of gas sensors. A degraded gas sensor means a gas sensor whose output value is outside a predetermined range, or a gas sensor whose output value deviates from the output value of other gas sensors by a predetermined percentage.

[0008] In the gas detector according to the first aspect of this invention, the control unit is configured to perform control to correct the output value of a deteriorated gas sensor based on the output values ​​of multiple gas sensors. This allows a deteriorated gas sensor to be continuously used for detecting the target gas by correcting it. Therefore, the lifespan of the gas sensors can be extended without increasing the number of gas sensors. As a result, a gas detector suitable for use in harsh environments where gas sensors are prone to deterioration can be provided while suppressing an increase in the number of parts and an increase in the size of the equipment. Note that the lifespan of a gas sensor is the same as the so-called remaining lifespan, indicating how long the gas sensor can be used in the future.

[0009] In the gas detector according to the first aspect described above, preferably, the control unit is configured to acquire output value information corresponding to the gas concentration based on the output values ​​of a plurality of gas sensors, and to correct any gas sensor that outputs an output value outside a predetermined range from the output value information of the plurality of gas sensors as a deteriorated gas sensor. With this configuration, the output value of a deteriorated gas sensor can be corrected based on the output value information acquired based on the output values ​​of a plurality of gas sensors without using a calibration reference gas. As a result, even if the gas detector is installed in an environment where calibration is difficult, the deteriorated gas sensor can be corrected. Furthermore, even if gas sensors are manufactured using the same process, the susceptibility to deterioration and the rate of deterioration may differ from one another due to manufacturing errors. Therefore, even if the usage conditions of the plurality of gas sensors are the same, there may be variations in the degree of deterioration. In addition, if dust adheres to any of the plurality of gas sensors, or if the plurality of gas sensors are exposed to a degrading atmosphere unevenly, the rate of deterioration of the plurality of gas sensors may differ from one another, resulting in variations in the degree of deterioration. Therefore, as described above, by correcting the output value of a degraded gas sensor based on output value information obtained from multiple gas sensors, it is possible to easily correct a sensor unit having multiple gas sensors with varying degrees of degradation.

[0010] In this case, preferably, the control unit is configured to determine the degree of deterioration of the sensor unit based on either the output value before correction, the correction status, or the output value information of the multiple gas sensors. With this configuration, the lifespan of the sensor unit can be easily predicted based on the degree of deterioration of the sensor unit. As a result, the timing of replacement of the sensor unit can be easily predicted.

[0011] In the configuration described above, where the control unit determines the degree of deterioration of the sensor unit, it is preferable that the control unit is configured to notify that the sensor unit or gas detector needs to be replaced based on the degree of deterioration. Generally, gas sensors have a shorter service life than their usable period. Therefore, replacement is required at a shorter time than the actual lifespan of the gas sensor. By configuring the control unit to notify that the sensor unit or gas detector needs to be replaced based on the degree of deterioration of the gas sensor, as described above, the sensor unit or gas detector can be used until it reaches the actual usage limit where it becomes unusable due to the end of its lifespan. As a result, the sensor unit or gas detector can be used for a longer period than the general service life.

[0012] In the gas detector according to the first aspect described above, preferably, the control unit is configured to notify the user if any of the gas sensors have deteriorated. With this configuration, the user can easily recognize that a gas sensor has deteriorated.

[0013] In this case, preferably, the control unit is configured to provide different notification methods depending on whether a gas sensor has deteriorated, specifically when the corrected gas sensor can be used continuously or when the corrected gas sensor cannot be used continuously. With this configuration, the user can easily determine whether the corrected gas sensor can be used continuously based on the notification method. As a result, the user can easily determine when it is time to replace the gas detector.

[0014] In the gas detector according to the first aspect described above, preferably, the gas to be detected includes a predetermined type of first target gas and a second target gas of a different type from the first target gas, and the plurality of gas sensors include a plurality of first gas sensors that detect the first target gas and a plurality of second gas sensors that detect the second target gas, and the control unit is configured to correct the output value of a deteriorated first gas sensor based on the output values ​​of the plurality of first gas sensors, and to correct the output value of a deteriorated second gas sensor based on the output values ​​of the plurality of second gas sensors. With this configuration, even if deterioration occurs in the first gas sensor and the second gas sensor, the deteriorated first gas sensor and the deteriorated second gas sensor can be continuously used to detect their respective target gases by correcting them based on their respective output values. Therefore, it is possible to improve the reliability of the first gas sensor and the second gas sensor, and thus improve the reliability of a gas detector that detects multiple types of target gases. As a result, it is possible to provide a gas detector that can detect multiple types of target gases in harsh environments.

[0015] A gas sensor control method according to the second aspect of this invention comprises the steps of: detecting a target gas based on the output values ​​of a plurality of gas sensors of the same type provided on the same chip; determining which of the plurality of gas sensors has deteriorated based on the output values ​​of the plurality of gas sensors; correcting the output value of the deteriorated gas sensor based on the output values ​​of the plurality of gas sensors; and continuing to use the corrected deteriorated gas sensor for detecting the target gas.

[0016] In the gas sensor control method according to the second aspect of the present invention, there are steps of correcting the output value of a gas sensor that has deteriorated among a plurality of gas sensors based on the output values of the plurality of gas sensors, and continuously using the deteriorated gas sensor after correction for detecting a gas to be detected. As a result, similar to the gas detector according to the first aspect, it becomes possible to extend the life of the gas sensor, so that it is possible to provide a gas sensor control method suitable for use in a harsh environment where the gas sensor is likely to deteriorate.

Advantages of the Invention

[0017] According to the present invention, as described above, it is possible to provide a gas detector and a gas sensor control method suitable for use in a harsh environment where the gas sensor is likely to deteriorate.

Brief Description of the Drawings

[0018] [Figure 1] It is a block diagram showing a control configuration of a gas detector according to an embodiment. [Figure 2] It is a circuit diagram showing a configuration example of a gas sensor of a gas detector according to an embodiment. [Figure 3] It is a schematic plan view showing a configuration example of a gas sensor of a gas detector according to an embodiment. [Figure 4] It is a schematic cross-sectional view showing a configuration example of a gas sensor of a gas detector according to an embodiment. [Figure 5] It is a graph for explaining a configuration in which a control unit of a gas detector determines whether a gas sensor has deteriorated according to an embodiment. [Figure 6] It is a flowchart for explaining a gas sensor control method by a gas detector according to an embodiment. [Figure 7] It is a block diagram showing a control configuration of a gas detector according to a modification.

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0020] Referring to FIGS. 1 to 6, the configuration of the gas detector 100 according to an embodiment will be described.

[0021] (Configuration of Gas Detector) The gas detector 100 of the present embodiment is a gas detector that detects a gas to be detected. Further, when the gas detector 100 detects the gas to be detected, it outputs an alarm to notify the user of gas leakage or the like. The gas to be detected is the gas that the gas detector 100 should detect. For example, the gas to be detected is a fuel gas (city gas) mainly containing methane gas.

[0022] As shown in FIG. 1, the gas detector 100 includes a sensor unit 1, a control unit 2, a notification unit 3, a storage unit 4, a plurality of amplifiers 5, and a communication unit 6. The plurality of gas sensors 10, the control unit 2, the notification unit 3, and the communication unit 6 are housed in the housing of the gas detector 100. The gas detector 100 operates by power supplied from a commercial power source or power of a battery not shown.

[0023] The sensor unit 1 includes a plurality of gas sensors 10 of the same type. The sensor unit 1 detects a single type of gas to be detected. In the example shown in FIG. 1, the sensor unit 1 includes gas sensors 10a to 10c. The sensor unit 1 outputs the output values 30 of the plurality of gas sensors 10 to the amplifier 5. In FIG. 1, for the sake of convenience, it is described that the output value 30 is output from only one of the plurality of gas sensors 10, but the output value 30 is also output from other gas sensors 10 in the same manner.

[0024] Each gas sensor 10 includes a sensing element 11 and a heating element 12 that heats the sensing element 11 to a predetermined temperature. The output values ​​30 of each gas sensor 10 are input to the corresponding amplifier 5. The gas sensors 10 are MEMS-type gas sensors. In other words, each gas sensor 10 is formed using MEMS (Micro Electro Mechanical Systems) technology, which forms a mechanical structure in a semiconductor substrate using a semiconductor manufacturing process. For example, each gas sensor 10 has a size of approximately 0.1 mm on each side. Note that in Figure 1, for convenience, only gas sensor 10a is shown with the sensing element 11 and heating element 12, but gas sensors 10b and 10c also include the sensing element 11 and heating element 12 in the same way.

[0025] Multiple gas sensors 10 include a measurement circuit as shown in Figure 2. The measurement circuit comprises sensor elements 13a to 13c, opposite-side resistors R1, R2, R4, R5, R7, and R8, and load resistors R3, R6, and R9.

[0026] Voltage is applied from power supply E to the sensor element 13a, the opposite side resistors R1 and R2, and the load resistor R3. Additionally, an output value of 30 (see Figure 1) is output from terminal A1 connected between the sensor element 13a and the load resistor R3, and from terminal A2 connected between the opposite side resistors R1 and R2.

[0027] Furthermore, voltage is applied from power supply E to the sensor element 13b, the opposite side resistors R4 and R5, and the load resistor R6. Additionally, an output value 30 is output from terminal A3 connected between the sensor element 13b and the load resistor R6, and from terminal A4 connected between the opposite side resistors R4 and R5.

[0028] Furthermore, voltage is applied from power supply E to the sensor element 13c, the opposite side resistors R7 and R8, and the load resistor R9. Additionally, an output value 30 is output from terminal A5 connected between the sensor element 13c and the load resistor R9, and from terminal A2 connected between the opposite side resistors R7 and R8.

[0029] In this embodiment, a voltage is simultaneously applied to each of the multiple gas sensors 10 from the power supply E. That is, in this embodiment, the multiple gas sensors 10 are driven simultaneously.

[0030] The gas sensor 10 changes its resistance when the target gas is adsorbed. Therefore, the change in the electrical resistance of the gas sensor 10 is extracted as a deviation voltage, and this is set as the output value 30, making it possible to measure the concentration of the target gas.

[0031] Specifically, the sensing element 11 of the gas sensor 10 is heated to a predetermined temperature by the heating element 12, thereby adsorbing oxygen from the air. Furthermore, if the target gas (for example, methane gas) is present, the oxygen adsorbed on the sensing element 11 reacts, causing a change in the electrical resistance of the sensing element 11. Multiple gas sensors 10 detect methane gas by measuring this change in electrical resistance.

[0032] Each of the multiple gas sensors 10, as shown in Figures 3 and 4, includes a substrate 14, an electrode pattern 15 provided on the substrate 14 via an insulating film 14a, a pair of electrode parts 16 connected to a power supply E (see Figure 2), and a SnO2 sensitive layer 17 covering the electrode pattern 15. The substrate 14 is made of Si. A cavity C is formed in the substrate 14. The electrode pattern 15 is made of Pt. The electrode pattern 15 also serves as both a sensitive part 11 and a heating part 12. In other words, the electrode pattern 15 is heated to a predetermined temperature when current is passed through it. Furthermore, when the gas to be detected is present, the resistance value of the electrode pattern 15 changes, thereby changing the output value 30. Note that the structures of gas sensors 10a to 10c are the same, so in Figure 4, gas sensor 10a is shown as a representative of the multiple gas sensors 10. The substrate 14 is an example of a "chip" as defined in the claims.

[0033] Furthermore, as shown in Figure 3, multiple gas sensors 10 are provided on the same substrate 14. In the example shown in Figure 3, three gas sensors 10a to 10c are provided on the same substrate 14. Note that the number of gas sensors 10 is not limited to three. For example, there may be several tens to 100 gas sensors 10. Preferably, there are 10 to 20 gas sensors 10. Also, the multiple gas sensors 10 may be arranged in an array on the same substrate 14.

[0034] The control unit 2 controls each part of the gas detector 100 (multiple gas sensors 10, notification unit 3, multiple amplifiers 5, and communication unit 6). The control unit 2 also detects the target gas based on the output values ​​30 of the multiple gas sensors 10. For example, the control unit 2 obtains the concentration of the target gas based on all the output values ​​30 of the multiple gas sensors 10. The control unit 2 includes a processor such as a CPU (Central Processing Unit) and memory such as RAM (Random Access Memory). The control unit 2 also performs control processing by executing a predetermined program.

[0035] The control unit 2 heats the sensing unit 11 to a predetermined temperature by pulse driving of the heating unit 12 at predetermined time intervals, and performs detection at predetermined temperatures of the multiple gas sensors 10 at predetermined time intervals. In other words, the control unit 2 pulsely heats the sensing unit 11 to a temperature at which methane gas can be detected at predetermined time intervals, and performs detection of methane gas at predetermined time intervals. For example, the control unit 2 performs detection of the multiple gas sensors 10 at predetermined temperatures with a period of approximately 60 seconds. The control unit 2 may also perform detection for the entire duration of the pulse in which the sensing unit 11 is pulsed, or it may perform detection for a part of the duration of the pulse in which the sensing unit 11 is pulsed (for example, the duration of one point).

[0036] Furthermore, the control unit 2 is configured to determine whether or not deterioration has occurred in the multiple gas sensors 10. The control unit 2 is also configured to determine the degree of deterioration of the sensor unit 1. Details of how the control unit 2 determines whether or not deterioration has occurred in the gas sensors 10, and how it determines the degree of deterioration of the sensor unit 1, will be described later.

[0037] The notification unit 3 provides notification by sound, light, etc., when the target gas is detected. The notification unit 3 is also configured to notify if there is a deteriorated gas sensor 10. Furthermore, the notification unit 3 provides notification in different ways depending on the degree of deterioration of the gas sensor 10 and the sensor unit 1. For example, the notification unit 3 can provide notification by varying the type, volume, and length of the sound it emits. The notification unit 3 can also provide notification by varying the color, whether or not it flashes, and the location of the light emitted.

[0038] The memory unit 4 stores a determination threshold (not shown) for the gas concentration to be detected, various programs (not shown) executed by the control unit 2, output value information 20 (described later), correction count information 21 (described later) which is information on the number of corrections performed on the gas sensor 10, and a threshold Th used to determine the deterioration of the gas sensor 10, which will be described later. The memory unit 4 includes, for example, a semiconductor memory element.

[0039] Amplifier 5 is configured to amplify the output value 30 output by the gas sensor 10. Amplifier 5 also outputs the amplified output value 30 to the control unit 2. Amplifier 5 includes amplifiers 5a to 5c corresponding to the gas sensors 10a to 10c. Amplifier 5 is, for example, an operational amplifier.

[0040] The communication unit 6 can communicate with an external device 7. For example, the communication unit 6 communicates with the external device 7 via a network. Alternatively, the communication unit 6 may communicate by directly connecting to the external device 7 via wired or wireless connection.

[0041] The control unit 2, notification unit 3, storage unit 4, and communication unit 6 may be provided on the same substrate 14 as the sensor unit 1, or they may be provided on different substrates.

[0042] (Degradation detection of gas sensor 10) In this embodiment, the control unit 2 determines whether or not a gas sensor 10 has deteriorated based on the output values ​​30 of the multiple gas sensors 10. Specifically, the control unit 2 acquires output value information 20 corresponding to the gas concentration based on the output values ​​30 of the multiple gas sensors 10. The control unit 2 then determines that a gas sensor 10 that outputs an output value 30 outside a predetermined range from the output value information 20 among the multiple gas sensors 10 is a deteriorated gas sensor 10. The output value information 20 includes, for example, the average value 20a (see Figure 5) of the output values ​​30 of the multiple gas sensors 10, the median, and the average value of the remaining output values ​​30 after excluding the maximum and minimum values.

[0043] Referring to Figure 5, the configuration in which the control unit 2 determines whether or not deterioration has occurred in the gas sensor 10 using the average value 20a of the output values ​​30 of multiple gas sensors 10 as output value information 20 will be described. In the graph shown in Figure 5, the vertical axis is the output value 30 of the gas sensor 10, and the horizontal axis is the number (No.) of the gas sensor 10.

[0044] In the example shown in Figure 5, gas sensors 1 to 3 (10) correspond to gas sensors 10a to 10c.

[0045] The control unit 2 obtains an average value 20a based on the output values ​​30a to 30c of the gas sensors 10a to 10c. The control unit 2 then determines whether the output values ​​30a to 30c of each gas sensor 10 are within a predetermined range 40. The predetermined range 40 is a range with an upper limit of the average value 20a plus a threshold Th, and a lower limit of the average value 20a minus the threshold Th. In other words, the predetermined range 40 is a range of +ΔTh and -ΔTh centered on the average value 20a. If the output value 30 of a gas sensor 10 is outside the predetermined range 40, the control unit 2 determines that the gas sensor 10 has deteriorated. The output value 30 of a deteriorated gas sensor 10 is excluded from the calculation of the average value 20a.

[0046] The threshold Th is 1 / 10 (10%) of the 10% LEL (Lower Explosion Limit) value, which is used, for example, to determine whether a gas leak is detected. For example, if the gas being detected is a methane-based gas, the 10% LEL is 5000 ppm. Therefore, if the gas being detected is a methane-based gas, the threshold Th is 500 ppm.

[0047] Furthermore, in this embodiment, if there is a deteriorated gas sensor 10, the control unit 2 excludes the output value 30 of the deteriorated gas sensor 10 and obtains the concentration of the gas to be detected. In other words, if there is a deteriorated gas sensor 10, the control unit 2 obtains the concentration of the gas to be detected using only the output value 30 of the gas sensors 10 that have not deteriorated.

[0048] Furthermore, the control unit 2 can determine that the sensor unit 1 as a whole is nearing or has deteriorated if the average value 20a approaches or exceeds a predetermined value (for example, half the value or the full value relative to 10% LEL), or if the operating time of multiple gas sensors 10 has elapsed to a predetermined time.

[0049] In harsh environments, the gas sensor 10 is prone to degradation. If the degraded gas sensor 10 is not used, the reliability of the sensor unit 1 decreases, resulting in a gas detector unsuitable for use in harsh environments. For example, a harsh environment includes at least one of the following: an environment with extreme temperature fluctuations and an environment with high temperatures.

[0050] (Correction of gas sensor output value) Therefore, in this embodiment, the control unit 2 is configured to perform control to correct the output value 30 of a gas sensor 10 that has deteriorated, based on the output values ​​30 of a plurality of gas sensors 10. Specifically, the control unit 2 is configured to correct a gas sensor 10 that outputs an output value 30 that is outside a predetermined range from the output value information 20 of the plurality of gas sensors 10, treating it as a deteriorated gas sensor 10. More specifically, the control unit 2 corrects the output value 30 of a deteriorated gas sensor 10 based on the output value 30 of a gas sensor 10 that has not deteriorated.

[0051] In this embodiment, the control unit 2 corrects the deteriorated gas sensor 10 by correcting the gain of the amplifier 5 corresponding to the deteriorated gas sensor 10 based on the output value 30 of the gas sensor 10 that has not deteriorated. Specifically, the control unit 2 obtains an average value 20a (see Figure 5) from the output values ​​30 of a plurality of gas sensors 10 that have not deteriorated. Then, the control unit 2 obtains a predetermined range 40 (see Figure 5) based on the average value 20a and a threshold Th, and corrects the gain of the amplifier 5 so that the output value 30 of the deteriorated gas sensor 10 falls within the obtained predetermined range 40. Preferably, the control unit 2 corrects the gain of the amplifier 5 so that the output value 30 of the deteriorated gas sensor 10 becomes the output value information 20 (average value 20a).

[0052] Furthermore, the control unit 2 stores the number of times correction has been performed for each of the multiple gas sensors 10 as correction count information 21 in the storage unit 4.

[0053] Furthermore, if correction of the output values ​​30 of multiple gas sensors 10 is applied from the initial startup of the gas detector 100, the output values ​​30 of gas sensors 10 whose output values ​​30 before correction fall outside a predetermined range due to initial defects can be corrected. As a result, the corrected gas sensor 10 that experienced an initial defect can be continuously used to detect the target gas.

[0054] (Determination of the degree of deterioration of the sensor part) In this embodiment, the control unit 2 is configured to determine the degree of deterioration of the sensor unit 1 based on any of the following: the output values ​​30 before correction of the multiple gas sensors 10, the correction status, or the output value information 20.

[0055] When determining the degree of deterioration of the sensor unit 1 based on the uncorrected output values ​​30 of multiple gas sensors 10, the control unit 2 determines the degree of deterioration of the sensor unit 1 based, for example, on the degree of deviation between the uncorrected output values ​​30 of the multiple gas sensors 10 and the average value 20a of the output values ​​30 excluding the output values ​​30 of the gas sensors 10 that have deteriorated. Specifically, the control unit 2 determines that the degree of deterioration of the sensor unit 1 is progressing as the degree of deviation between the uncorrected output values ​​30 of the multiple gas sensors 10 and the average value 20a increases.

[0056] Furthermore, when determining the degree of deterioration based on the correction status, the control unit 2 determines the degree of deterioration of the sensor unit 1 based, for example, on the number of corrections performed on the deteriorated gas sensor 10. Specifically, the control unit 2 obtains the number of corrections for each gas sensor 10 based on the correction count information 21 stored in the memory unit 4, and determines that the more corrections performed, the more advanced the deterioration of the sensor unit 1.

[0057] Furthermore, when determining the degree of deterioration based on the output value information 20, the control unit 2 may be configured to determine the degree of deterioration of the sensor unit 1 based on the number of gas sensors 10 whose uncorrected output value 30 falls outside a predetermined range 40 determined based on the output value information 20 (for example, the average value 20a) and a threshold Th. In this case, the control unit 2 determines that the degree of deterioration of the sensor unit 1 is progressing as the number of gas sensors 10 whose uncorrected output value 30 falls outside the predetermined range 40 increases.

[0058] (Notification of replacement of the sensor unit or gas detector) In this embodiment, the control unit 2 is configured to notify that the sensor unit 1 or the gas detector 100 needs to be replaced based on the degree of deterioration.

[0059] Specifically, the control unit 2 notifies that the sensor unit 1 needs to be replaced when its deterioration reaches a predetermined stage. For example, the control unit 2 notifies that the sensor unit 1 needs to be replaced when the number of gas sensors 10 that cannot be used after correction exceeds a predetermined number. For example, in a sensor unit 1 having 10 gas sensors 10, if 3 gas sensors 10 become unusable after correction, the control unit 2 notifies that the sensor unit 1 needs to be replaced. If only the sensor unit 1 can be replaced, the control unit 2 only needs to notify that the sensor unit 1 needs to be replaced based on its deterioration. Furthermore, if the entire gas detector 100 needs to be replaced along with the sensor unit 1, the control unit 2 only needs to notify that the gas detector 100 needs to be replaced based on its deterioration.

[0060] (Notification of deteriorated gas sensor) The control unit 2 is configured to notify the system if any of the gas sensors 10 have deteriorated. Specifically, the control unit 2 notifies the system of the presence of a deteriorated gas sensor 10 by controlling the notification unit 3. In this embodiment, the control unit 2 may also cause the notification unit 3 to notify the system in a different manner depending on the degree of deterioration of the gas sensor 10. For example, if the notification unit 3 notifies by emitting light such as an LED, the control unit 2 will notify the system of the degree of deterioration of the gas sensor 10 by lighting the LED yellow if the degree of deterioration is small. If the degree of deterioration of the gas sensor 10 is large, the control unit 2 will notify the system of the degree of deterioration of the gas sensor 10 by lighting the LED red. Furthermore, for example, when the notification unit 3 provides notification by voice, the control unit 2 notifies the degree of deterioration of the gas sensor 10 by having the notification unit 3 emit a short "beep, beep, beep" sound if the degree of deterioration of the gas sensor 10 is small. Also, if the degree of deterioration of the gas sensor 10 is large, the control unit 2 notifies the degree of deterioration of the gas sensor 10 by having the notification unit 3 emit a long "beep, beep, beep" sound.

[0061] Furthermore, in this embodiment, when the control unit 2 notifies that a gas sensor 10 has deteriorated, it is configured to provide different notification methods depending on whether the corrected gas sensor 10 can be used continuously or whether the corrected gas sensor 10 cannot be used continuously. For example, if the corrected gas sensor 10 can be used continuously, the control unit 2 notifies that the corrected gas sensor 10 can be used continuously by lighting up a green LED and simultaneously lighting up a yellow LED. If the corrected gas sensor 10 cannot be used continuously, the control unit 2 notifies that the corrected gas sensor 10 cannot be used continuously by lighting up a yellow LED and simultaneously lighting up a red LED.

[0062] (Gas detection process) Next, the gas detection process by the control unit 2 will be explained with reference to Figure 6.

[0063] In step S1 of Figure 6, the control unit 2 detects the gas to be detected based on the output values ​​30 of multiple gas sensors 10 of the same type provided on the same substrate 14.

[0064] Next, in step S2, the control unit 2 determines which of the multiple gas sensors 10 has deteriorated based on the output values ​​30 of the multiple gas sensors 10. If there are no deteriorated gas sensors 10, the process ends. If there are deteriorated gas sensors 10, the process proceeds to step S3.

[0065] If the process proceeds from step S2 to step S3, in step S3, the control unit 2 corrects the output value 30 of the gas sensor 10 that has deteriorated, based on the output values ​​30 of the gas sensors 10.

[0066] Next, in step S4, the control unit 2 continues to use the corrected, degraded gas sensor 10 for detecting the target gas. After that, the process ends.

[0067] (Effects of this embodiment) In this embodiment, the following effects can be obtained.

[0068] In this embodiment, as described above, the control unit 2 is configured to perform control to correct the output value 30 of a gas sensor 10 that has deteriorated, based on the output values ​​30 of the multiple gas sensors 10. As a result, a deteriorated gas sensor 10 can be continuously used to detect the target gas by correcting it. Therefore, the lifespan of the gas sensors 10 can be extended without increasing the number of gas sensors 10. As a result, a gas detector 100 suitable for use in harsh environments where gas sensor 10 deterioration is likely to occur can be provided, while suppressing an increase in the number of parts and an increase in the size of the equipment.

[0069] Furthermore, in this embodiment, as described above, the control unit 2 acquires output value information 20 corresponding to the gas concentration based on the output values ​​30 of the multiple gas sensors 10, and is configured to correct any gas sensor 10 that outputs an output value 30 outside a predetermined range from the output value information 20 among the multiple gas sensors 10 as a deteriorated gas sensor 10. This makes it possible to correct the output value 30 of a deteriorated gas sensor 10 based on the output value information 20 acquired based on the output values ​​30 of the multiple gas sensors 10, without using a calibration reference gas. As a result, even if the gas detector 100 is installed in an environment where calibration is difficult, the deteriorated gas sensor 10 can be corrected. In addition, even if the gas sensors 10 are manufactured using the same process, the susceptibility to deterioration and the degree of deterioration may differ from one another due to manufacturing errors. Therefore, even if the usage conditions of the multiple gas sensors 10 are the same, there may be variations in the degree of deterioration. Furthermore, if dust adheres to any of the gas sensors 10, or if the gas sensors 10 are unevenly exposed to a degraded atmosphere, the rate of degradation of the gas sensors 10 may differ from one another, resulting in variations in the degree of degradation. Therefore, as described above, by correcting the output value 30 of the degraded gas sensor 10 based on the output value information 20 acquired based on the output values ​​30 of the gas sensors 10, the sensor unit 1 having multiple gas sensors 10 with varying degrees of degradation can be easily corrected.

[0070] Furthermore, in this embodiment, as described above, the control unit 2 is configured to determine the degree of deterioration of the sensor unit 1 based on any of the pre-correction output values ​​30 of the multiple gas sensors 10, the correction status, or the output value information 20. This makes it easy to predict the lifespan of the sensor unit 1 based on its degree of deterioration. As a result, it is easy to predict when the sensor unit 1 needs to be replaced.

[0071] Furthermore, in this embodiment, as described above, the control unit 2 is configured to notify that the sensor unit 1 or the gas detector 100 needs to be replaced based on the degree of deterioration. Generally, the gas sensor 10 has a shorter service life than its usable period. Therefore, it needs to be replaced at a shorter time than the actual lifespan of the gas sensor 10. By configuring the control unit 2 to notify that the sensor unit 1 or the gas detector 100 needs to be replaced based on the degree of deterioration of the gas sensor 10, as described above, the sensor unit 1 or the gas detector 100 can be used until it reaches the actual usage limit where it becomes unusable due to the end of its lifespan. As a result, the sensor unit 1 or the gas detector 100 can be used for a longer period than the general service life.

[0072] Furthermore, in this embodiment, as described above, the control unit 2 is configured to notify the user if any of the gas sensors 10 have deteriorated. This allows the user to easily understand that a gas sensor 10 has deteriorated.

[0073] Furthermore, in this embodiment, as described above, when the control unit 2 notifies that there is a deteriorated gas sensor 10, it is configured to make the notification mode different depending on whether the corrected gas sensor 10 can be used continuously or not. This allows the user to easily understand whether the corrected gas sensor 10 can be used continuously based on the notification mode. As a result, the user can easily understand when it is time to replace the gas detector 100.

[0074] Furthermore, in this embodiment, as described above, the gas sensor control method includes the steps of: correcting the output value 30 of a gas sensor 10 that has deteriorated among the multiple gas sensors 10 based on the output values ​​30 of the multiple gas sensors 10; and continuing to use the corrected deteriorated gas sensor 10 for detecting the target gas. This makes it possible to extend the lifespan of the gas sensor 10, similar to the gas detector 100, and thus provides a gas sensor control method suitable for use in harsh environments where deterioration of the gas sensor 10 is likely to occur.

[0075] (modified version) It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than by the description of the embodiments above, and further includes all modifications (exceptions) within the meaning and scope equivalent to the claims.

[0076] For example, the above embodiment shows an example in which the gas detector 100 detects a single type of target gas, but the present invention is not limited thereto. In the present invention, the target gas may include a predetermined type of first target gas and a second target gas of a different type from the first target gas. The first target gas is, for example, methane gas. The second target gas is, for example, hydrogen sulfide gas generated from sewage or the like.

[0077] As shown in the modified example in Figure 7, the gas detector 200 may include a sensor unit 201, a control unit 202, a notification unit 3, a storage unit 4, an amplifier 5, and a communication unit 6.

[0078] The modified sensor unit 201 includes a plurality of gas sensors, which include a plurality of first gas sensors 203 for detecting a first target gas and a plurality of second gas sensors 204 for detecting a second target gas.

[0079] The first gas sensor 203 is, for example, a semiconductor gas sensor capable of detecting methane gas. The first gas sensor 203 includes three gas sensors, first gas sensors 203a to 203c. Since the first gas sensor 203 has the same configuration as the gas sensor 10 according to the above embodiment, a detailed explanation is omitted.

[0080] The second gas sensor 204 is a semiconductor gas sensor capable of detecting, for example, hydrogen sulfide gas. The second gas sensor 204 is formed by MEMS technology, which forms a mechanical structure in a semiconductor substrate using a semiconductor manufacturing process. For example, the second gas sensor 204 has a size of about 0.1 mm on each side. The second gas sensor 204 also includes a substrate, an electrode pattern provided on the substrate, and a ZnO-sensitive layer covering the electrode pattern. The ZnO-sensitive layer also contains gallium. The second gas sensor 204 detects gas by heating the ZnO-sensitive layer to a predetermined temperature by pulse driving. The second gas sensor 204 includes second gas sensors 204a to 204c.

[0081] In the modified gas detector 200, amplifier 5 includes amplifiers 5a to 5c corresponding to the first gas sensors 203a to 203c, and amplifiers 5d to 5f corresponding to the second gas sensors 204a to 204c.

[0082] The control unit 202 is configured to correct the output values ​​30 of a first gas sensor that has deteriorated based on the output values ​​30 of a plurality of first gas sensors 203, and to correct the output values ​​30 of a second gas sensor that has deteriorated based on the output values ​​30 of a plurality of second gas sensors 204. The configuration in which the control unit 202 corrects the deteriorated first gas sensor 203 is the same as the configuration in which the control unit 2 corrects the deteriorated gas sensor 10 according to the above embodiment, except that a first threshold Th1 is used instead of a threshold Th, so a detailed explanation is omitted. Similarly, the configuration in which the control unit 202 corrects the deteriorated second gas sensor 204 is the same as the configuration in which the control unit 2 corrects the deteriorated gas sensor 10 according to the above embodiment, except that a second threshold Th2 is used instead of a threshold Th, so a detailed explanation is omitted.

[0083] The first threshold Th1 and the second threshold Th2 should be 10% of the 10% LEL of the first target gas and 10% of the 10% LEL of the second target gas, respectively.

[0084] In the modified gas detector 200, as described above, the control unit 202 is configured to correct the output value 30 of a first gas sensor 203 that has deteriorated based on the output value 30 of a plurality of first gas sensors 203, and to correct the output value 30 of a second gas sensor 204 that has deteriorated based on the output value 30 of a plurality of second gas sensors 204. As a result, even if deterioration occurs in the first gas sensor 203 and the second gas sensor 204, the deteriorated first gas sensor 203 and the deteriorated second gas sensor 204 can be continuously used to detect their respective target gases by correcting them based on their respective output values ​​30. Therefore, the reliability of the first gas sensor 203 and the second gas sensor 204 can be improved, and thus the reliability of the gas detector 200 that detects multiple types of target gases can be improved. As a result, a gas detector 200 capable of detecting multiple types of target gases in harsh environments can be provided.

[0085] Furthermore, in the above embodiment, an example was shown in which the control unit 2 corrects a gas sensor 10 that outputs an output value 30 outside a predetermined range from the output value information 20 among the plurality of gas sensors 10 as a deteriorated gas sensor 10, but the present invention is not limited to this. The control unit may be configured to determine whether or not deterioration has occurred in a gas sensor based on the output value of the gas sensor without using the output value information. For example, the control unit may be configured to determine that deterioration has occurred in a gas sensor when the difference between the output value of one gas sensor and that gas sensor is greater than or equal to a predetermined difference.

[0086] Furthermore, although the above embodiment shows an example in which the control unit 2 determines the degree of deterioration of the sensor unit 1, the present invention is not limited to this. For example, the control unit does not need to determine the degree of deterioration of the sensor unit.

[0087] Furthermore, while the above embodiment shows an example in which the control unit 2 notifies that the sensor unit 1 or the gas detector 100 needs to be replaced based on the degree of deterioration, the present invention is not limited to this. For example, the control unit does not need to notify that the sensor unit or the gas detector needs to be replaced.

[0088] Furthermore, in the above embodiment, an example was shown in which the control unit 2 notifies the system if any of the gas sensors 10 have deteriorated, but the present invention is not limited to this. For example, the control unit does not need to notify the system even if there are deteriorated gas sensors.

[0089] Furthermore, in the above embodiment, an example was shown in which the control unit 2 provides different notification methods for when the corrected gas sensor 10 can be used continuously and for when the corrected gas sensor 10 cannot be used continuously. However, the present invention is not limited to this. For example, the control unit does not need to provide different notification methods for when the corrected gas sensor can be used continuously and for when the corrected gas sensor cannot be used continuously.

[0090] Furthermore, although the above embodiment shows an example where the threshold value Th is set to 10% of the 10% LEL of the gas to be detected, the present invention is not limited to this. For example, the threshold may be set by obtaining the variance of the output values ​​of multiple gas sensors and setting it as 1σ of the variance, or by setting the threshold value to 20% of the mean value.

[0091] Furthermore, although the above embodiment shows an example of a configuration in which all of the gas sensors 10 are used to detect the target gas, the present invention is not limited to this. It is not necessary to use all of the gas sensors when detecting the target gas. However, even if not all of the gas sensors are used when detecting the target gas, it is still necessary to drive all of the gas sensors.

[0092] Furthermore, although the above embodiment shows an example in which the control unit 2 acquires the concentration of the gas to be detected based on the output values ​​30 of a plurality of gas sensors 10, the present invention is not limited to this. For example, the control unit may be configured to determine the presence or absence of the gas to be detected based on the output values ​​of a plurality of gas sensors.

[0093] Furthermore, although the above embodiment shows an example of a configuration in which gas is detected at a predetermined temperature at predetermined time intervals of approximately 60 seconds, the present invention is not limited to this. In the present invention, gas may be detected at predetermined time intervals other than 60 seconds.

[0094] Furthermore, although the above embodiment shows an example in which the multiple gas sensors 10 are semiconductor type gas sensors, the present invention is not limited to this. For example, the multiple gas sensors may be electrochemical sensors (potential-constant electrolytic type, diaphragm galvanic cell type), catalytic combustion type gas sensors, or gas thermal conduction type gas sensors. When the multiple gas sensors are configured as gas sensors other than semiconductor type, it is necessary to arrange each gas sensor within a predetermined range (for example, a few centimeters) in order for the multiple gas sensors to detect the same target gas.

[0095] Furthermore, although the above embodiment showed methane as the gas to be detected, the present invention is not limited to this. For example, the gas to be detected may be hydrogen gas, ethane gas, propane gas, or carbon monoxide gas.

[0096] Furthermore, although the above embodiment shows an example in which the gas detector 100 is equipped with a notification unit 3 and a communication unit 6, the present invention is not limited thereto. In the present invention, the gas detector may be equipped with only one of the notification unit and the communication unit. For example, the gas detector may not be equipped with a communication unit. Also, the gas detector may not be equipped with a notification unit. In this case, the notification unit may be provided separately from the gas detector. Furthermore, even if the gas detector is equipped with a notification unit, notification may be performed by an external device to the gas detector.

[0097] Furthermore, in the above embodiment, for the sake of explanation, an example was shown in which the control process was explained using a flow-driven flowchart that processes sequentially according to the processing flow, but the present invention is not limited to this. In the present invention, the control process may be performed by event-driven processing, which executes processing on an event-by-event basis. In this case, it may be performed as a completely event-driven system, or a combination of event-driven and flow-driven systems may be used. [Explanation of Symbols]

[0098] 1. 201 Sensor section 2,202 Control Unit 10, 10a~10c Gas Sensor 20 Output Value Information 30 Output Value 100, 200 gas detectors 203, 203a~203c First gas sensor 204, 204a~204c Second gas sensor

Claims

1. A gas detector that detects the target gas, A sensor unit including multiple gas sensors of the same type, mounted on the same chip, The system includes a control unit that detects the target gas based on the output values ​​of the plurality of gas sensors, The control unit is configured to perform control to correct the output value of a gas sensor that has deteriorated, based on the output values ​​of the plurality of gas sensors, in the gas detector.

2. The control unit is configured to acquire output value information corresponding to the gas concentration based on the output values ​​of the plurality of gas sensors, and to perform the correction on a gas sensor that outputs an output value outside a predetermined range from the output value information among the plurality of gas sensors, treating it as the deteriorated gas sensor.

3. The gas detector according to claim 2, wherein the control unit is configured to determine the degree of deterioration of the sensor unit based on any of the output values ​​of the plurality of gas sensors before correction, the correction status, and the output value information.

4. The gas detector according to claim 3, wherein the control unit is configured to notify that the sensor unit or the gas detector needs to be replaced based on the degree of deterioration.

5. The gas detector according to claim 1, wherein the control unit is configured to notify the gas sensor that has deteriorated if any of the plurality of gas sensors has deteriorated.

6. The gas detector according to claim 5, wherein the control unit is configured to provide different notification methods for when the corrected gas sensor can be used continuously and when the corrected gas sensor cannot be used continuously, when it provides notification that the gas sensor has deteriorated.

7. The gas to be detected includes a first gas to be detected of a predetermined type and a second gas to be detected of a different type from the first gas to be detected. The plurality of gas sensors include a plurality of first gas sensors that detect the first target gas and a plurality of second gas sensors that detect the second target gas, The gas detector according to claim 1, wherein the control unit is configured to correct the output values ​​of the first gas sensors that have deteriorated based on the output values ​​of the plurality of first gas sensors, and to correct the output values ​​of the second gas sensors that have deteriorated based on the output values ​​of the plurality of second gas sensors.

8. The steps include detecting a target gas based on the output values ​​of multiple gas sensors of the same type installed on the same chip, The steps include determining which of the plurality of gas sensors has deteriorated based on the output values ​​of the plurality of gas sensors, The steps include correcting the output value of the gas sensor among the plurality of gas sensors that has deteriorated based on the output values ​​of the plurality of gas sensors, A gas sensor control method comprising the step of continuing to use the corrected gas sensor that has deteriorated in order to detect the gas to be detected.

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