Gas detection and control devices

Abstract

To provide a gas detection device in which the useful life of a detection element can be easily predicted, and a control device.SOLUTION: The gas detection device pertaining to one embodiment of the present invention comprises a sensor chamber, an acquisition unit, a measurement unit and a calculation unit. The sensor chamber houses a detection element having output which changes by absorption, by the detection element, of an odorous content included in detection object gas. The acquisition unit acquires a zero point which is the output of the detection element when gas for calibration is introduced into the sensor chamber and a measured value that is a change amount of the detection element from the zero point when the detection object gas is introduced into the sensor chamber. The measurement unit measures the odorous content on the basis of the measured value of the detection element. The calculation unit acquires an approximate curve that indicates the characteristic of change with time of the zero point, on the basis of history data that is the history of the zero point, and calculate a time till a critical value is reached in which the zero point is preliminarily set, on the basis of the approximate curve.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a gas detection device and a control device. [Background technology]

[0002] In order to distinguish between odors, which are collections of multiple gas components, there has been active development in recent years of odor sensors that pattern odors by arranging gas sensors with adsorption films with multiple different chemical properties into an array to form a multi-array sensor.The use of such odor sensors makes it possible to distinguish between pleasant and unpleasant odors, and applications of odor sensors have begun to be considered in fields where human sensory evaluation has traditionally been relied upon. These applications include indoor and automotive environmental management, factory process management, and environmental monitoring to detect early-stage fires and malodors that affect the human body.

[0003] For example, odor sensors use a detection element with an adsorption film on a quartz crystal oscillator. The resonant frequency of the quartz crystal oscillator decreases in proportion to the weight of gas adsorbed by the adsorption film, so gas can be detected based on the change in resonant frequency. Therefore, a decrease in sensitivity level due to deterioration over time of the adsorption film that adsorbs odorants affects the reliability of the odor sensor. The main cause of deterioration of the adsorption film over time is that the adsorbed odor components cannot be released from the adsorption film during sensor use, and remain on the adsorption film, causing the odor components to accumulate.

[0004] For example, as gas sensors continue to be used, their elements deteriorate, causing a decrease in gas sensitivity and malfunction. When a gas sensor reaches the end of its life, it will no longer function as an odor sensor, and its reliability as a sensor will decrease, or it will become completely unusable. Therefore, knowing the element's lifespan is very useful for users, as it lets them know when the sensor will no longer be usable and increases convenience by allowing them to arrange for a replacement sensor or sensor element.

[0005] As a method for predicting the lifespan of such gas sensors, for example, Patent Document 1 discloses a method in which a history of changes in sensitivity to a standard gas used for calibration is sequentially stored, a time-dependent sensitivity decay characteristic curve specific to the gas sensor is obtained based on this calibration history data, and a specific decay point at which the sensitivity value is a specific ratio to the initial sensitivity value set for the gas sensor is found using this curve, thereby obtaining the end of service life. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6182052 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the method described in Patent Document 1 requires sequential calibration processes using multiple types of standard gases to obtain calibration history data, and also requires setting sensitivity adjustment amounts based on the sensor output values ​​of these various standard gases so that the sensor sensitivity value matches the initial sensitivity value, resulting in the problem that the sensor calibration process requires a great deal of effort.

[0008] In view of the above circumstances, an object of the present invention is to provide a gas detection device and a control device that can easily predict the life of a detection element. [Means for solving the problem]

[0009] A gas detection device according to one aspect of the present invention includes a sensor chamber, an acquisition unit, a measurement unit, and a calculation unit. The sensor chamber accommodates a detection element that produces an output change upon adsorption of odor components contained in the detection target gas. The acquisition unit acquires a zero point, which is the output of the detection element when a calibration gas is introduced into the sensor chamber, and a measurement value, which is the amount of change from the zero point of the detection element when the target gas is introduced into the sensor chamber. The measurement unit measures the odor components based on the measurement value of the detection element. The calculation unit obtains an approximation curve showing the time-dependent change characteristics of the zero point based on historical data that is a history of the zero point, and calculates the time until the zero point reaches a predetermined limit value based on the approximation curve.

[0010] The calculation unit may be configured to calculate an average rate of change of the zero points using a predetermined number of the most recent pieces of the history data, and extrapolate the average rate of change to the most recent zero point, thereby obtaining the approximation curve.

[0011] The limit value may be a limit value indicating a limit of sensitivity of the detection element.

[0012] The detection element may be a vibration device having an adsorption film that adsorbs the odor component, and in which a change in resonant frequency occurs due to the adsorption of the odor component.

[0013] The limit value may be a limit value indicating a limit of the oscillation frequency of the vibration device.

[0014] The gas detection device may further include a first gas introduction line, a second gas introduction line, and a storage unit. The first gas introduction line introduces the target gas into the sensor chamber. The second gas introduction line has a filter capable of adsorbing odor components contained in the target gas, and introduces the target gas as the calibration gas into the sensor chamber through the filter. The storage unit stores the history data and the limit value.

[0015] The detecting element may include a plurality of detecting elements, in which case the calculation unit obtains the approximation curve for each of the plurality of detecting elements.

[0016] A control device according to one aspect of the present invention is a control device for a gas detection device, an acquisition unit that acquires a zero point, which is the output of a detection element that changes in output due to adsorption of odor components contained in a detection target gas, when a calibration gas is introduced into a sensor chamber that houses the detection element, and a measurement value, which is the amount of change from the zero point of the detection element when the detection target gas is introduced into the sensor chamber; a measurement unit that measures the odor components based on the measurement values ​​of the detection element; a calculation unit that obtains an approximation curve that indicates a time-dependent change characteristic of the zero point based on history data that is a history of the zero point, and calculates a time until the zero point reaches a preset limit value based on the approximation curve; It is equipped with: [Effects of the Invention]

[0017] According to the present invention, the life of a detection element can be easily predicted. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram of a gas detection device according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing an example of the configuration of a detection element. [Figure 3] FIG. 4 is a schematic diagram showing frequency changes of a detection element. [Figure 4] FIG. 10 is a diagram showing an example of the relationship between the gas sensitivity of a QCM and the amount of fluctuation in the zero-point frequency. [Figure 5] FIG. 10 is a diagram showing an example of the relationship between the amount of frequency drop that causes oscillation defects in a QCM and the crystal impedance value (CI value). [Figure 6] 10 is a graph showing an example of the relationship between the zero-point frequency and the odorant concentration at that time relative to the operating time of the odor sensor. [Figure 7] 5 is a diagram illustrating a method for calculating a predicted life span of a detection element in the gas detection device. FIG. [Figure 8] 6 is a flowchart showing an example of a procedure for a refresh process in the gas detection device. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] [Gas detection equipment] FIG. 1 is a schematic diagram of a gas detection device 100 according to one embodiment of the present invention. The gas detection device 1 is configured as an alarm device that is installed, for example, inside a distribution board and detects specific odor components in gas that is generated when an abnormality such as overheating of a distribution cable or a cable fire occurs, and then issues an alarm, etc.

[0021] As shown in FIG. 1, gas detection device 100 includes gas sensor 2, control device 4, and display device 5.

[0022] The gas sensor 2 has a housing 20 , a first intake port 21 , a second intake port 22 , and a sensor chamber 60 .

[0023] The first intake port 21 communicates with the sensor chamber 60 via a first flow path 31. The second intake port 22 communicates with the sensor chamber 60 via a second flow path 32. First intake port 21 and second intake port 22 are inlets for taking outside air G into sensor chamber 60. Outside air G is a gas to be detected by gas detection device 100, and in this embodiment, is the air inside the switchboard.

[0024] A first pump 31P is disposed in first flow path 31 to take in outside air G from first intake port 21 into sensor chamber 60. This forms a first gas introduction line L1 that introduces outside air G into sensor chamber 60.

[0025] A second pump 32P is disposed in second flow path 32, which takes in outside air G from second intake port 22 into sensor chamber 60. A filter 32F is disposed in second flow path 32, which adsorbs odor components and moisture contained in the outside air G taken in from second intake port 22 to generate clean air, which is a calibration gas. This forms a second gas introduction line L2 that introduces clean air into sensor chamber 60.

[0026] In the embodiments of the present invention, clean air refers to gas from which odorous components and moisture contained in the outside air G have been removed using a filter, but it is also possible to provide a separate device that generates clean gas that does not contain odorous components or moisture, and to send the clean gas from that device to the sensor chamber 60 as clean air.

[0027] The first pump 31P and the second pump 32P are typically configured as diaphragm pumps, but other gas senders capable of sending or sucking gas at a constant flow rate, such as fans or blowers, can also be used. The first pump 31P and the second pump 32P are driven individually by the control device 4, and by driving either one of them, either the first flow path 31 or the second flow path 32 is selected as the intake flow path for outside air.

[0028] The filter 32F can be made of materials with high humidity removal properties such as silica gel or molecular sieves to remove humidity and hydrophilic odor components, materials with high odor adsorption properties such as activated carbon or zeolite to remove odor components, or a combination of these.

[0029] The sensor chamber 60 accommodates a plurality of QCM (Quartz Crystal Microbalance) sensors 10 as detection elements, and a temperature sensor 71 .

[0030] Sensor chamber 60 forms a chamber into which measurement is performed by taking in outside air G. Sensor chamber 60 is connected to first flow path 31 and second flow path 32, and outside air G is introduced into sensor chamber 60 via first air intake port 21 or second air intake port 22. Although not shown, sensor chamber 60 is connected to an exhaust passage that exhausts the introduced gas.

[0031] The QCM sensor 10 is a detection element whose resonant frequency changes when it adsorbs odor components contained in the outside air G. Each QCM sensor 10 constitutes a detection channel (ch). The number of QCM sensors 10 corresponds to the number of channels, and is not particularly limited. In this embodiment, an example is given in which a 16-channel QCM sensor 10 is provided, but at least one channel is sufficient.

[0032] An oscillation circuit 50 is connected to each QCM sensor 10. Each oscillation circuit 50 is driven by the control device 4. Each oscillation circuit 50 vibrates each QCM sensor 10 at a predetermined resonance frequency. The oscillation circuit 50 is connected to a counter circuit (not shown) that counts the oscillation frequency of the QCM sensor 10. The counter circuit counts changes in the resonance frequency of each QCM sensor 10 and outputs the count value to the control device 4. In this embodiment, the measurement value of each QCM sensor 10 is the count value output by the counter circuit.

[0033] The temperature sensor 71 measures the temperature of the outside air G. The measurement value output from the temperature sensor 71 is output to the control device 4. The control device 4 corrects the measurement value of each QCM sensor 10 based on the temperature measured by the temperature sensor 71. Typically, a temperature measuring element such as a thermistor is used for the temperature sensor 71.

[0034] The humidity sensor 72 measures the relative humidity of the outside air G. The measurement value output from the humidity sensor 72 is output to the control device 4. The control device 4 corrects the measurement value of each QCM sensor 10 based on the humidity measured by the humidity sensor 72. The humidity sensor 72 can be a conventional type such as a capacitance type that detects humidity based on the output value of capacitance or a semiconductor type that detects humidity based on the output value of resistance, but is not limited to these. A hydrophilic adsorption film may be formed on the QCM sensor, and the humidity of each QCM sensor 10 may be corrected based on the change in resonant frequency when odor components are adsorbed.

[0035] The temperature sensor 71 and the humidity sensor 72 are not limited to being configured separately, and a temperature and humidity sensor having both a temperature measurement function and a humidity measurement function may be employed.

[0036] Each QCM sensor 10, each oscillation circuit 50, temperature sensor 71, and humidity sensor 72 may be mounted on a common wiring board, or may be mounted on separate wiring boards.

[0037] Each QCM sensor 10 has a configuration comprising a quartz crystal oscillator as an oscillator and an adsorption film disposed on the quartz crystal oscillator that adsorbs specific odor components contained in the outside air G. The basic structure is the same except for the type of adsorption film.

[0038] 2, the QCM sensor 10 includes a quartz crystal oscillator 13, an electrode 11, an adsorption film 12, lead lands 16A and 16B, leads 14A and 14B, pin terminals 19A and 19B, and a holder 18. The quartz crystal oscillator 13 is, for example, an AT-cut quartz crystal plate. The resonant frequency of the quartz crystal oscillator 13 is not particularly limited and is, for example, 32 MHz.

[0039] Since the resonant frequency of the quartz crystal oscillator 13 of the QCM sensor 10 decreases in proportion to the weight of the gas adsorbed by the adsorption film 12, the amount of change in the resonant frequency is calculated for each QCM sensor 10, and based on this calculation result, it is possible to detect whether the outside air G contains the odor component that is the detection target of the adsorption film 12.

[0040] In this embodiment, a quartz crystal resonator with a resonant frequency is used as the detection element, but this is not limiting. For example, other vibration devices such as a ceramic resonator, a surface acoustic wave element, a piezoelectric thin film resonator, a cantilever, and a diaphragm can also be used instead of a quartz crystal resonator.

[0041] Electrodes 11 are formed on both sides of the quartz crystal unit 13, and an adsorption film 12 is formed on the electrodes 11 formed on one side of the quartz crystal unit 13. Lead lands 16A are formed integrally with the electrodes 11 formed on one side, and lead lands 16B are formed integrally with the electrodes 11 formed on the other side.

[0042] The adsorption films 12, which are the sensitive films of each QCM sensor 10, are made of different materials. The materials constituting the adsorption films 12 are selected arbitrarily depending on the type of odor component to be detected. The adsorption films 12 are configured to be able to adsorb one or more types of odor components.

[0043] Leads 14A and 14B are made of a metal spring material. One end of lead 14A is electrically connected to electrode 11 formed on one surface via lead land 16A, and the other end is connected to pin terminal 19A. One end of lead 14B is electrically connected to electrode 11 formed on the other surface via lead land 16B, and the other end is connected to pin terminal 19B. Pin terminals 19A and 19B are supported by a holder 18 provided on the wiring board, and holder 18 supports crystal unit 13 so that it can vibrate freely.

[0044] The control device 4 is configured to alternately repeat a refresh process and a gas measurement process. The refresh process cleans the adsorption film 12 of each QCM sensor 10 and the inside of the sensor chamber 60 with clean air introduced through the second gas introduction line L2, and acquires the zero point (hereinafter also referred to as the zero point frequency), which is the resonant frequency of each QCM sensor 10 in a state sufficiently cleaned by the clean air. The gas measurement process measures the amount of change from the zero point frequency of each QCM sensor 10 when outside air G is introduced into the sensor chamber 60 through the first gas introduction line L1. Based on the measurement values ​​of each QCM sensor 10, the control device 4 detects the presence or absence of a specific odor component in the gas G, which is the detection target gas, or measures the amount or concentration of the odor component.

[0045] FIG. 3 is a schematic diagram showing an example of the change in output of the QCM sensor 10 during the refresh process and the gas measurement process.

[0046] During the refresh process period before the gas measurement process, the adsorption film 12 and sensor chamber 60 of each QCM sensor 10 are thoroughly cleaned with clean air to set environmental factors such as the vibration frequency of each QCM sensor 10 and the humidity of the sensor chamber 60 to zero. Cleaning the adsorption film 12 means desorbing odor components from the adsorption film 12 with clean air. The gas measurement process is performed after the refresh process. In the illustrated example, the changes in the resonant frequencies of three QCM sensors 10, ch1, ch2, and ch3, out of the 16-channel QCM sensor 10, are shown. The minimum frequency value that indicates the maximum change from the zero-point frequency of each channel is included in the measurement value of each QCM sensor 10. The gas measurement process is performed at a predetermined cycle (e.g., every hour) for a predetermined time (e.g., 10 minutes).

[0047] After the gas measurement process is completed, the refresh process is performed again. This causes the gas components adsorbed in the adsorption film 12 of each QCM sensor 10 to desorb, and each QCM sensor 10 returns to its zero-point frequency. The refresh process period is not particularly limited, and may be performed continuously after the gas measurement process is completed until just before the next gas measurement process.

[0048] In a QCM sensor 10 that has not deteriorated over time, the zero-point frequency of each QCM sensor 10 is 32 MHz, which is the natural frequency of the quartz oscillator 13. On the other hand, if desorption of gas components and moisture is insufficient due to deterioration of the adsorption film 12 over time, the zero-point frequency of the QCM sensor 10 will be a frequency lower than the natural frequency of the quartz oscillator 13.

[0049] The decrease in the zero-point frequency of the QCM sensor 10 has a strong correlation with the gas sensitivity of the QCM sensor 10. Figure 4 shows an example of the relationship between the gas sensitivity of the QCM sensor 10 and the amount of fluctuation in the zero-point frequency. This figure shows the relationship between the change in the zero-point frequency of the QCM sensor 10 for any number of channels and their gas sensitivity when the QCM sensor 10 is operated for a long period of time in a high-temperature, high-humidity environment. The horizontal axis represents the frequency difference from the zero point, and the vertical axis on the left represents the gas sensitivity ratio. The gas sensitivity ratio is a relative ratio, with the sensitivity when the frequency difference is 0 being set to 100.

[0050] As shown in Figure 4, gas sensitivity also tends to decrease as the zero frequency decreases. Once gas sensitivity reaches a certain level, it becomes impossible to distinguish between noise and gas detection response, so there is a lower limit to gas sensitivity, below which the sensor will no longer be reliable. The relationship between gas sensitivity and zero frequency can be explained as follows:

[0051] QCM sensors used for gas detection have sites for gas adsorption. This is particularly evident in sensitive membranes with high sensor properties, and materials containing numerous micropores are often used. As the sensor is used, such sensitive membranes lose their adsorption sites due to factors such as irreversible contamination, causing a decrease in sensitivity. This contamination of the adsorption sites causes the mass of the sensitive membrane to increase, which gradually reduces the vibration frequency of the QCM sensor.

[0052] Furthermore, Figure 5 shows an example of the relationship between the amount of frequency drop that causes a QCM sensor to malfunction and the crystal impedance value (CI value). The frequency of the QCM sensor decreases as the weight of the sensitive film increases. On the other hand, as shown in the figure, the CI value increases as the frequency decreases. If the CI value exceeds a limit value, the QCM sensor will malfunction. Therefore, if the sensor is used further in a state where sensitivity has decreased, and an extremely large increase in film weight is caused by contamination, the QCM sensor will stop functioning.

[0053] From the above, we can see that the zero-point frequency changes depending on the state of contamination of the sensitive film, and the more irreversible contamination of the sensitive film becomes, the greater the weight of the sensitive film becomes, and the corresponding decrease in the zero-point frequency of the QCM sensor. On the other hand, the frequency of the QCM sensor represents the degree of contamination of the sensitive film, and is an indicator of the state of the gas adsorption sites of the sensitive film, as well as an indicator of the occurrence of oscillation failure caused by an increase in film weight.

[0054] Figure 6 is a graph showing an example of the relationship between the zero-point frequency and the concentration of odorous substances at that time against the operating time of an odor sensor in a distribution board. Here, a QCM sensor is used as the odor sensor, and an optical gas concentration meter is used to measure the gas concentration.

[0055] As shown in Figure 6, two trends can be seen in the changes in the odor sensor. The first is a large drop in frequency occurring at regular intervals. The other is a tendency for the zero-point frequency to gradually decrease without any particular time limit. As with the previous discussion, the main cause of these is thought to be irreversible contamination of the sensitive membrane. Most of the points where a large drop in the zero-point frequency is observed are those where the gas concentration meter indicates a high value. In other words, this is thought to be due to the inhalation of a very strong odor, which caused the strong odor components to irreversibly adhere to the minute pores in the sensitive film of the QCM sensor, preventing desorption and increasing the weight of the sensitive film. Regarding the gradual decrease in the zero-point frequency, it is presumed that a trace amount of gas that would not normally affect the change in the sensor frequency slowly bound to the sensitive membrane, causing contamination, resulting in a gradual decrease in the zero-point frequency.

[0056] From the above, it can be seen that a decrease in the zero-point frequency is observed even in an actual environment, and that contamination of the sensitive film under normal use affects the lifespan of the sensor. Therefore, the control device 4 of this embodiment is configured to be able to predict the life of each QCM sensor 10 from the change over time in the zero-point frequency as follows.

[0057] [Control device] The control device 4 will be described in detail below. The control device 4 is an information processing device having a CPU and memory. The control device 4 controls the driving of the first pump 31P, the second pump 32P, the oscillation circuit 50, the temperature sensor 71, the humidity sensor 72, etc., and acquires information about the resonance frequency and its change amount of each QCM sensor 10, as well as the temperature and humidity of the outside air G, from the oscillation circuit 50, the temperature sensor 71, and the humidity sensor 72.

[0058] 1, the control device 4 has, as functional blocks of a CPU, an acquisition unit 41, a measurement unit 42, a calculation unit 43, and a determination unit 44. The control device 4 further includes a storage unit 45 configured with a semiconductor memory or the like.

[0059] (Storage part) The memory unit 45 stores a program for operating the acquisition unit 41, the measurement unit 42, the calculation unit 43, and the determination unit 44 as functional blocks of a CPU. The memory unit 45 stores correction coefficients for temperature correction and humidity correction of the measurement values ​​of each QCM sensor 10.

[0060] The memory unit 45 stores the zero-point frequency, which is the resonant frequency of each QCM sensor 10 in a state in which the adsorption film 12 and the sensor chamber 60 are cleaned by clean air during the refresh process, acquired by the acquisition unit 41. The memory unit 45 stores history data, which is the history of the zero-point frequency during each refresh process for each QCM sensor 10.

[0061] The memory unit 45 stores the measurement values ​​of each QCM sensor 10 in the gas measurement process acquired by the acquisition unit 41. The measurement values ​​of each QCM sensor 10 are acquired for each QCM sensor 10 in each gas measurement process, and are stored in the memory unit 45 as historical data of the measurement values.

[0062] The storage unit 45 stores the measurement values ​​of the temperature sensor 71 and the humidity sensor 72 acquired by the acquisition unit 41. The storage unit 45 stores the measurement values ​​of each QCM sensor 10 and the measurement values ​​of the temperature sensor 71 and the humidity sensor 72 in a time-related association.

[0063] (Acquisition Department) In each refresh process, the acquisition unit 41 acquires the zero-point frequency of each QCM sensor 10 and the measurement values ​​of the temperature sensor 71 and the humidity sensor 72. In each gas measurement process, the acquisition unit 41 acquires the measurement values ​​of each QCM sensor 10 and the measurement values ​​of the temperature sensor 71 and the humidity sensor 72, and stores these in the memory unit 45.

[0064] In this embodiment, for example, the following three conditions are set as criteria for adopting the zero-point frequency of each QCM sensor 10 to be stored in the storage unit 45. The first condition is that the fluctuation amount of the zero-point frequency acquired before and after does not exceed a predetermined threshold, the second condition is that the acquired zero-point frequency is a zero-point frequency measured in an odor-free environment, and the third condition is that the initial temperature and humidity conditions are matched.

[0065] The first condition is intended to prevent the inclusion of abnormal values ​​in the zero-point frequency history data. Since abnormal jumps in the magnitude of change are occasionally observed in the time-series change in the zero-point frequency, the threshold value is set for the amount of fluctuation in the zero-point frequency used as history data so that the abnormal values ​​are removed, preventing the abnormal values ​​from adversely affecting the calculation of the prediction formula for determining the lifespan (corresponding to the approximation curve described below). Specifically, the threshold value is set to a value that is considered to be a statistical outlier based on the data on fluctuations in the zero-point frequency that has already been acquired. If the natural frequency of the QCM sensor 10 used is 32 MHz, the threshold value is, for example, 10,000 Hz, but can be set arbitrarily depending on the type of adsorption film 12.

[0066] The second condition is intended to exclude zero-point frequencies that have been subjected to frequency fluctuations due to the adsorption of odor components from the zero-point frequencies used as history. The zero-point frequencies are obtained during the refresh process as described above, but odor components that cannot be removed by the filter 32F may be mixed into the clean air. In this case, large fluctuations are observed in the zero-point frequencies, and if a fluctuation in the zero-point frequency exceeds a predetermined level, it can be assumed that odor components are present. Note that this second condition is essentially synonymous with the first condition and may therefore be included in the first condition.

[0067] The third condition is intended to eliminate the adverse effects on life expectancy prediction caused by the mixing of zero-point frequencies under different temperature and humidity conditions, since QCM sensors generally have temperature and humidity dependent characteristics. The initial temperature and humidity settings are, for example, the temperature and humidity when the zero-point frequency is acquired at the beginning of operation of gas detection device 100. This makes it possible to prevent variations in the zero-point frequency due to differences in temperature and humidity conditions. Additionally, the initial temperature and humidity conditions must match, but this does not necessarily mean that they must match perfectly. For example, a certain tolerance band may be adopted around the initial temperature and humidity. For example, if the temperature and humidity during measurement of the zero-point frequency are within the initial temperature setting ±30°C and the initial humidity setting ±8% RH, they are considered to match the initial temperature and humidity settings.

[0068] (Measurement part) During the gas measurement process, the measurement unit 42 corrects the measurement values ​​of each QCM sensor 10 using correction coefficients for temperature and humidity, and measures the type and amount or concentration of a specific odor component in the gas G, which is the detection target gas. The specific odor component is an odor component that is adsorbed by at least one adsorption film 12 of each QCM sensor 10 and can be identified by a reference detection pattern stored in the memory unit 46. It should be noted that known methods can be used to correct the temperature and humidity of the measurements of each QCM sensor 10, and the details thereof will be omitted here.

[0069] (Calculation section) Based on the history data that is the history of the zero-point frequency, the calculation unit 43 acquires an approximation curve that indicates the time-dependent change characteristics of the zero-point frequency for each QCM sensor 10. Based on the acquired approximation curve, the calculation unit 43 calculates the time until the zero-point frequency for each QCM sensor 10 reaches a preset limit value.

[0070] For example, Figure 7 shows an example of the change over time in the zero-point frequency of the QCM sensor 10 for each channel in the sensor chamber 60 of the gas detection device 100 installed inside a distribution board. In the figure, the horizontal axis represents the number of days elapsed, and the vertical axis represents the amount of change in the zero-point frequency. The figure shows the sensitivity per unit concentration of the QCM sensor 10 for any channel (here, ch7 and ch16) to the generated gas at any measurement time points A, B, and C.

[0071] Here, point A indicates the time before the burnt odor measurement, point B indicates the time after the burnt odor measurement, and point C indicates the time any number of days after point B. The burnt odor contains the odor component to be detected that is generated from the insulating coating that covers the distribution cable when the cable heats up.

[0072] As shown in Figure 7, the zero-point frequency gradually decreases for most channels from the start of measurement, and it can be seen that the gas sensitivity per unit concentration also decreases as the zero-point frequency decreases. Furthermore, before and after measuring the burnt odor, the zero-point frequency of the QCM sensor for a specific channel (ch16 in this case) decreases significantly compared to the other QCM sensors (see points A and B), and then decreases linearly (see points B and C).

[0073] 7, the calculation unit 43 obtains an approximate curve (an approximate straight line in this example) that indicates the time-varying characteristics of the zero-point frequency up to the present for each QCM sensor 10 based on the history data, which is the history of the zero-point frequency. This is done by calculating, for example, the average rate of change of the most recent past zero-point frequencies. This makes it relatively easy to predict the time-varying characteristics of the QCM sensor 10. Note that the method for calculating the approximate curve is not limited to the linear approximation method described above, and other approximation methods can also be used.

[0074] The calculation unit 43 extrapolates the acquired approximation curve to the current zero-point frequency for each channel. Taking the approximation curve for the QCM sensor 10 associated with channel 16 shown in FIG. 7 as an example, the calculation unit 43 calculates the intersection point D between the approximation curve and the limit frequency, which is the limit value of the zero-point frequency preset for the QCM sensor 10 associated with channel 16, as the lifespan of the QCM sensor 10. The intersection point D corresponds to the replacement time for the QCM sensor 10. The "lifespan" here refers to the number of days from the start of measurement to the intersection point D.

[0075] The limit value is set individually for each QCM sensor 10 and stored in the memory unit 45. The limit value may be a limit value for the sensitivity limit, a limit value for the oscillation limit, or both. The limit value is set based on the type of adsorption film 12, the natural frequency of the quartz crystal oscillator 13, etc.

[0076] (Judgment Department) The determination unit 44 is configured to determine whether replacement is necessary for the lifespan of each QCM sensor calculated by the calculation unit 43. The determination unit 44 may determine whether replacement is necessary based on the number of days remaining in the lifespan calculated from the present. For example, the remaining lifespan may be determined using multiple criteria, such as "replacement required" if the remaining lifespan is less than 50 days, "prepare for replacement" if the remaining lifespan is 50 to 100 days, and "no replacement required" if the remaining lifespan is 100 days or more.

[0077] 7, it can be determined that the QCM sensor 10 for channel 16 "needs replacement," and that the QCM sensors 10 for the other channels "do not need replacement." The determination unit 44 is configured to determine whether the QCM sensor 10 for each channel needs replacement as described above, and to output the determination result to the display device 5.

[0078] (display device) The display device 5 has a display unit capable of displaying information about the lifespan of each QCM sensor 10 output from the control device 4. The display unit may display the judgment results of the judgment unit 44 regarding the remaining lifespan of each QCM sensor 10. The display may also be displayed in different formats depending on the judgment results. For example, only information about QCM sensors judged as "requiring replacement" or "preparing for replacement" may be displayed.

[0079] The display device 5 may also display on the display unit the history of the measurement values ​​of each QCM sensor 10, the results of identifying the detected gas, the gas concentration, etc. This allows the type and concentration of the detected gas to be known.

[0080] The display device 5 may further include alarm devices such as a buzzer and a lamp. In this case, based on an abnormality signal generated by the control device 4 when a specific odor component is detected, the buzzer can sound or the lamp can be turned on or blinked, thereby alerting the outside world of an abnormality in the switchboard.

[0081] [Gas detection device operation] Details of control device 4 will be described below along with a typical operation of gas detection device 100. Fig. 8 is a flowchart showing an example of the procedure for refresh processing, which is one of the processing procedures of control device 4.

[0082] The control device 4 alternately executes the refresh process and the gas measurement process. In this embodiment, the refresh process is executed every hour as follows, and then the gas measurement process is carried out.

[0083] When the refresh process starts, the control device 4 introduces clean air into the sensor chamber 60 through the second gas introduction line L2 (step 101). This cleans the adsorption film 12 of each QCM sensor 10 and the sensor chamber 60.

[0084] Next, the control device 4 acquires the zero-point frequency of each refreshed QCM sensor 10 and the measured values ​​of the temperature sensor 71 and the humidity sensor 72 at that time (step 102).The control device 4 then determines whether the acquired zero-point frequency of each QCM sensor 10 satisfies the above-mentioned adoption criteria (first to third criteria) (step 103), and if the adoption criteria are met, stores the acquired zero-point frequency of each QCM sensor 10 in the memory unit 45 (step 104).If the adoption criteria are not met, the acquired zero-point frequency is not stored in the memory unit 45, and the process ends.

[0085] The control device 4 determines whether a predetermined period of time has elapsed since the start of operation of the gas detection device 100 (step 105). The predetermined period of time may be a period of time until historical data on the zero-point vibration frequency of each QCM sensor 10 required for predicting the life of the QCM sensors 10 is accumulated. If the control device 4 determines that the predetermined period of time has elapsed since the start of operation of the gas detection device 100 ("Y" in step 105), it executes a life calculation process for each QCM sensor 10 (step 106).

[0086] In this life calculation step, the control device 4 calculates the rate of change of the zero-point frequency for each QCM sensor 10 from the zero-point frequency history data stored in the memory unit 45, based on the results of the most recent few measurements used for life prediction. Then, the control device 4 extrapolates the obtained rate of change to obtain an approximation curve, which is a prediction line of the zero-point frequency, for each QCM sensor 10 (see FIG. 7). As shown in FIG. 7, the operating time corresponding to the intersection D between the obtained approximation curve and the limit frequency as a preset limit value is predicted to be the life of the QCM sensor 10 (the time until the limit frequency is reached). The operating time until this limit frequency is reached is calculated as the predicted life of the QCM sensor 10.

[0087] There are two types of predicted lifespans. The first is a predicted lifespan at a sensitivity failure level, where the limit frequency is reached, determined by a decrease in gas sensitivity. This indicates that the QCM sensor 10 continues to function, but the initial sensitivity level cannot be guaranteed. The second is the predicted lifespan at the oscillation failure level, where oscillation stops. This indicates that the sensor's CI value exceeds the oscillation margin and the sensor is completely non-functional. As described above, the critical frequency is set individually for each QCM sensor 10. Furthermore, the critical frequency may be a limit value for a sensitivity failure level, a limit value for an oscillation failure level, or both.

[0088] Next, the control device 4 determines whether each QCM sensor 10 needs to be replaced based on the life calculation result (step 107). Here, for example, as described above, the determination may be made by classifying the QCM sensors into multiple categories such as "replacement required," "preparation for replacement," and "no replacement required" depending on the number of days remaining in the life calculated from the predicted life.

[0089] Next, the control device 4 outputs the judgment result to the display unit of the display device 5 based on the above judgment result (step 108). The judgment results to be displayed may be the judgment results for all QCMs, or may be the judgment results for QCMs that have been judged as "replacement required" and "preparing for replacement", for example.

[0090] The control device 4 executes the above process each time a refresh process is performed, thereby calculating the predicted lifespan of each QCM sensor 10. This allows the user to be notified when the sensor will no longer be usable, which improves the convenience of arranging for a replacement sensor or a replacement sensor element.

[0091] In addition, according to this embodiment, the zero-point frequency of each QCM sensor 10 is obtained using clean gas, in which odor components have been removed from the gas to be detected, as the calibration gas, so the lifespan of each QCM sensor 10 can be predicted more easily without having to prepare a dedicated standard gas as the calibration gas.

[0092] Furthermore, according to this embodiment, the zero-point frequency obtained each time a refresh process is executed is used to predict the lifespan of each QCM sensor 10, so the remaining lifespan of each QCM sensor 10 can be automatically determined in almost real time, thereby reducing the burden on maintenance workers.

[0093] Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above-described embodiments and that various modifications can be made.

[0094] For example, in the above embodiment, a QCM was used as an example of an odor component detection element, but this is not limiting and other detection elements, such as semiconductor sensors whose resistance changes upon adsorption of odor components, may also be used. Furthermore, the detection elements may be capable of detecting physical changes, such as an increase in weight or expansion stress due to gas adsorption of the adsorption film, and converting these changes into electrical signals.

[0095] In the above embodiment, the calculation of the predicted life of QCM sensor 10 and the process of determining the same (steps 108 and 109) are performed every time the refresh process is performed, but this is not limited thereto and the calculation and determination may be performed every predetermined number of refresh processes. In this case, the longer the number of operating days of gas detection device 100, the more frequently the predicted life of QCM sensor 10 is calculated and determined.

[0096] Furthermore, in the above embodiment, control device 4 is provided with storage unit 45, but a function replacing storage unit 45 may be installed in a cloud server connected to a network line. In this case, gas detection device 100 is provided with a communication device capable of communicating with the cloud server, and is configured to be able to send and receive history data of the zero-point frequency to and from the cloud server wirelessly or via a wired connection via the communication device.

[0097] The gas detection device according to the present invention is not limited to applications for detecting abnormalities such as fires. For example, it may be used as a sensor for detecting unpleasant odor components in a room and performing ventilation operations. The present invention is also applicable to analyzing odor components contained in unknown gases. [Explanation of symbols]

[0098] 4...Control device 10...QCM (detection element) 12...Adsorption film 41…Acquisition part 42…Measuring part 43...Calculation section 44…Judgment section 45...Storage section 71...Temperature sensor 72...Humidity sensor 100...Gas detection device

Claims

1. a sensor chamber that houses a detection element that produces an output change upon adsorption of odor components contained in the detection target gas; an acquisition unit that acquires a zero point, which is the output of the detection element when the calibration gas is introduced into the sensor chamber, and a measurement value, which is the amount of change from the zero point of the detection element when the detection target gas is introduced into the sensor chamber; a measurement unit that measures the odor components based on the measurement values ​​of the detection element; a calculation unit that obtains an approximation curve that indicates a time-dependent change characteristic of the zero point based on history data that is a history of the zero point, and calculates a time until the zero point reaches a preset limit value based on the approximation curve; Equipped with A gas detection device in which the history data is a history of zero points that meets one of the following conditions: the amount of fluctuation in the zero points obtained before and after does not exceed a predetermined threshold, and the temperature and humidity conditions at the initial setting are met.

2. 2. The gas detection device according to claim 1, The calculation unit calculates an average rate of change of the zero point using a predetermined number of most recent pieces of the history data, and extrapolates the rate to the most recent zero point to obtain the approximate curve. Gas detection equipment.

3. 3. The gas detection device according to claim 1 or 2, The limit value indicates the limit of the sensitivity of the detection element. Gas detection equipment.

4. 3. The gas detection device according to claim 1 or 2, The detection element is a vibration device having an adsorption film that adsorbs the odor components, and the adsorption of the odor components causes a change in resonance frequency. Gas detection equipment.

5. 5. The gas detection device according to claim 4, The limit value indicates a limit of oscillation of the vibration device. Gas detection equipment.

6. The gas detection device according to any one of claims 1 to 5, a first gas introduction line for introducing the target gas into the sensor chamber; a second gas introduction line having a filter capable of adsorbing odor components contained in the detection target gas, and introducing the detection target gas as the calibration gas into the sensor chamber through the filter; and a storage unit for storing the history data and the limit value. Gas detection equipment.

7. The gas detection device according to any one of claims 1 to 6, the detection element includes a plurality of detection elements; The calculation unit obtains the approximate curve for each of the plurality of detection elements. Gas detection equipment.

8. 1. A control device for a gas detection device, comprising: an acquisition unit that acquires a zero point, which is the output of a detection element that changes in output due to adsorption of odor components contained in a detection target gas, when a calibration gas is introduced into a sensor chamber that houses the detection element, and a measurement value, which is the amount of change from the zero point of the detection element when the detection target gas is introduced into the sensor chamber; a measurement unit that measures the odor components based on the measurement values ​​of the detection element; a calculation unit that obtains an approximation curve that indicates a time-dependent change characteristic of the zero point based on history data that is a history of the zero point, and calculates a time until the zero point reaches a preset limit value based on the approximation curve; Equipped with The historical data is a control device that is a history of zero points that meets one of the following conditions: the amount of fluctuation in the zero points obtained before and after does not exceed a predetermined threshold, and the temperature and humidity conditions at the initial setting are met.

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