Optical gas sensor device, gas detection method and program

Abstract

To suppress fluctuations in a gas concentration value based on a change in the substrate temperature.SOLUTION: An optical gas sensor device 100 comprises: a light source 2 which emits infrared rays to gas G being a detection object; an optical filter 3 which transmits the infrared rays of a wavelength corresponding to an absorption wavelength of the gas G being the detection object; a light receiving unit 4 which detects the infrared rays incident through the optical filter 3 and generates a detection signal; a substrate 6 on which the light source 2 and the light receiving unit 4 are mounted; and a signal processing unit 5. The signal processing unit 5 intermittently drive-controls on / off of the light source 2, and calculates a gas concentration value of the gas G being the detection object from a differential value obtained by subtracting the detection value of the detection signal during the off-state of the light source 2 from the detection value of the detection signal during the on-state of the light source 2.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an optical gas sensor device, a gas detection method, and a program. [Background technology]

[0002] Conventionally, gas sensors using the non-dispersive infrared absorption method (NDIR) are known. NDIR gas sensors utilize the property that many gases absorb their own infrared wavelengths, and measure the concentration of the gas by detecting how much of each wavelength is absorbed when infrared light is emitted to the gas to be detected. For example, there is a gas sensor that has an infrared light emitter and receiver and detects the concentration of the gas to be detected that is located in the optical path of the emitter and receiver.

[0003] For example, a non-dispersive infrared gas sensor is known that includes a light source arranged in a lens barrel into which a gas to be measured is introduced, and an infrared wavelength selection filter and an infrared detection unit arranged on a block separate from the lens barrel so as to face the light source (see Patent Document 1). The non-dispersive infrared gas sensor periodically switches the light source between a first set light amount and a second set light amount that is smaller than the first set light amount. The non-dispersive infrared gas sensor calculates the difference between the average value of two consecutive detection signals of the first set light amount and the detection signal of the second set light amount between them, and converts it into a gas concentration, thereby suppressing a decrease in the measurement accuracy of the gas concentration due to a change in the measurement environment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-135258 A Summary of the Invention [Problem to be solved by the invention]

[0005] In gas sensors, there is a demand for mounting the light source and the light receiving part on the same substrate in terms of miniaturization and simplification of the device configuration. In this configuration, heat from the light source is transferred to the light receiving part through the substrate, and has a large effect on the gas detection signal in the light receiving part. There is a demand for suppressing the fluctuation of the gas concentration value calculated from the gas detection signal based on the change in substrate temperature.

[0006] An object of the present invention is to suppress fluctuations in gas concentration values ​​due to changes in substrate temperature. [Means for solving the problem]

[0007] In order to solve the above problems, the optical gas sensor device of the present invention comprises: A light source that emits infrared rays to a gas to be detected; an optical filter that transmits infrared light having a wavelength corresponding to an absorption wavelength of the gas to be detected; a light receiving unit that detects infrared rays incident through the optical filter and generates a detection signal; a substrate on which the light source and the light receiving unit are mounted; and a signal processing unit that controls the on / off intermittent drive of the light source and calculates the gas concentration value of the gas to be detected from a difference value obtained by subtracting the detection value of the detection signal when the light source is off from the detection value of the detection signal when the light source is on.

[0008] The present invention also provides a method for producing a semiconductor device comprising the steps of: A light source that emits infrared rays to a gas to be detected; an optical filter that transmits infrared light having a wavelength corresponding to an absorption wavelength of the gas to be detected; a light receiving unit that detects infrared rays incident through the optical filter and generates a detection signal; a substrate on which the light source and the light receiving unit are mounted, The method includes a signal processing step of controlling the on / off of the light source intermittently and calculating the gas concentration value of the gas to be detected from a difference value obtained by subtracting the detection value of the detection signal when the light source is off from the detection value of the detection signal when the light source is on.

[0009] In addition, the program of the present invention is A light source that emits infrared rays to a gas to be detected; an optical filter that transmits infrared light having a wavelength corresponding to an absorption wavelength of the gas to be detected; a light receiving unit that detects infrared rays incident through the optical filter and generates a detection signal; a substrate on which the light source and the light receiving unit are mounted, a signal processing unit that performs intermittent drive control by turning on / off the light source, and calculates a gas concentration value of the gas to be detected from a difference value obtained by subtracting a detection value of a detection signal when the light source is off from a detection value of a detection signal when the light source is on; Function as. Effect of the Invention

[0010] According to the present invention, it is possible to suppress fluctuations in gas concentration values ​​due to changes in substrate temperature. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of an optical gas sensor device according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a perspective view of an optical gas sensor device. [Diagram 3] FIG. [Figure 4] FIG. 2 is a diagram showing a circuit configuration of an optical gas sensor device and an instrument. [Diagram 5] 13 is a flowchart showing a status signal generating process. [Figure 6] 13 is a flowchart showing a light source intermittent drive control process. [Figure 7] 6 is a flowchart showing a measurement loop process of the status signal generation process of FIG. 5. [Figure 8] FIG. 4 is a diagram showing the waveform of a status signal. [Figure 9] FIG. 4 illustrates various timings of the on-off waveforms of the light source. [Figure 10]1A is a diagram showing the time characteristics of the detection value when the light source is on, and FIG. 1B is a diagram showing the time characteristics of the detection value when the light source is off. [Figure 11] FIG. 13 is a diagram showing the time characteristics of a difference value of a detection value. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the scope of the present invention is not limited to the illustrated examples.

[0013] First, a schematic configuration of an optical gas sensor device 100 according to the present embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram of the optical gas sensor device 100 according to the present embodiment.

[0014] As shown in FIG. 1, the optical gas sensor device 100 of this embodiment is an NDIR type gas sensor, and includes an optical cover 1, a light source 2, an optical filter 3, a light receiving unit 4, a signal processing unit 5, and a switch 81. The optical gas sensor device 100 radiates (emits, emits) infrared rays from the light source 2, and emits the infrared rays to the gas G to be detected (measured) in the optical cover 1 through an optical path (path) in the optical cover 1. The amount of light reaching the light receiving unit 4 is reduced by the molecules of the gas G to be detected that exist in the optical path absorbing the infrared rays. The optical gas sensor device 100 detects the infrared rays partially absorbed by the gas G to be detected by the light receiving unit 4 through the optical filter 3, processes the detection signal by the signal processing unit 5, and detects (measures) and outputs the concentration of the gas G to be detected. The switch 81 is a switch that turns on / off the light emission of the light source 2, and is included in the circuit element unit 8 described later. When gas detection is performed, the signal processing unit 5 turns the light source 2 on / off via the switch 81 to operate it intermittently. The optical cover 1 has a gas introduction port 11 as a gas introduction section which is an inlet for introducing the gas G to be detected. A contamination filter 12 is attached to the gas introduction port 11 to prevent foreign matter from entering from the outside. The contamination filter 12 is, for example, a metal mesh filter or a resin porous film.

[0015] In particular, the optical gas sensor device 100 filters the infrared rays emitted from the light source 2 to the gas G to be detected by the optical filter 3 and receives them by the light receiving unit 4. The optical filter 3 is disposed in a position near the light receiving unit 4 on the optical path upstream of the light receiving unit 4. This configuration can reduce the area of ​​the optical filter 3 and reduce costs, since it is sufficient to filter the infrared rays emitted from the light source 2 on the light receiving surface of the light receiving unit 4, compared to a configuration in which the infrared rays emitted from the light source 2 are filtered by an optical filter before being emitted to the gas G to be detected. Furthermore, the signal-to-noise ratio (SN ratio) of the sensor is improved because the infrared rays emitted from sources other than the light source 2 before filtering are not received. However, the optical gas sensor device 100 may be configured to filter the infrared rays emitted from the light source 2 by the optical filter 3 and emit them to the gas G to be detected. In this embodiment, the infrared rays received by the light receiving unit 4 through the optical filter 3 are designed so that they reach the gas G by reflecting off the inner surface of the optical cover 1, as well as the optical path that reaches the gas G directly from the light source 2. It is desirable for the inner surface of the optical cover 1 to have a high reflectance, since this increases the efficiency of using light (infrared rays).

[0016] The optical gas sensor device 100 detects an alternative fluorocarbon refrigerant, which is a refrigerant for air conditioners, as the gas G to be detected. The alternative fluorocarbon is a synthetic compound (gas) refrigerant used industrially as an alternative to specific fluorocarbons (chlorofluorocarbons, abbreviated as CFCs). CFC refrigerants have a high ozone depletion potential and are a cause of destruction of the Earth's ozone layer, so replacement with hydrochlorofluorocarbon (HCFC) refrigerants, which have a low ozone depletion potential, has begun. In developed countries, there is also a shift from HCFC refrigerants to HFC refrigerants (R410A), which has an ozone depletion potential of zero.

[0017] CFC refrigerants, HCFC refrigerants, and HFC refrigerants have a high global warming potential and are known to be greenhouse gases that cause global warming. For this reason, the replacement of HFC refrigerants (R410A) with HFC refrigerants (R32) that have a lower global warming potential is being considered. In this embodiment, for example, R32, a fluorocarbon refrigerant, is detected as the gas G to be detected.

[0018] The optical gas sensor device 100 outputs various status signals based on the gas concentration value of the detected gas G to an information processing unit of the device that performs processing based on the status of the optical gas sensor device 100. The information processing unit is, for example, an MCU (Micro Controller Unit) 200 in FIG. 4 described later. The status signals are, for example, a fault signal, an alarm signal, and a monitoring signal (normal signal). The fault signal indicates a fault state of the optical gas sensor device 100. The alarm signal indicates that the concentration of the detected gas G is in an abnormal state (alarm state) that requires an alarm. The monitoring signal indicates that the concentration of the detected gas G is in a normal state. When the device is an alarm device, it issues various alarms (for example, an alarm of a fault of the optical gas sensor device 100 based on a fault signal, an alarm of an abnormality in the concentration of the detected gas G based on an alarm signal) in response to various signals received from the optical gas sensor device 100. The device may be a device 230 (FIG. 4) including the optical gas sensor device 100 and the MCU 200, or may be a device separate from the optical gas sensor device 100 (an external device including the MCU 200 (e.g., the device 230 in FIG. 4)). Examples of the device include a room air conditioner, a store / office air conditioner, and a multi-air conditioner for a building.

[0019] However, the gas G to be detected is not limited to R32, and may be other fluorocarbon refrigerants. Furthermore, the gas G to be detected is not limited to fluorocarbon refrigerants, and may be carbon dioxide, carbon monoxide, propane, methane, butane, ammonia, oxygen disulfide, nitrogen dioxide, nitric oxide, ozone, sulfur hexafluoride, ethylene, etc.

[0020] Next, a specific device configuration of the optical gas sensor device 100 will be described with reference to Figures 2 and 3. Figure 2 is a perspective view of the optical gas sensor device 100. Figure 3 is a perspective view of the light source 2.

[0021] As shown in Fig. 2, the optical gas sensor device 100 specifically includes an optical cover 1, a light source 2, an optical filter 3, a light receiving unit 4, a signal processing unit 5, a substrate 6, a connector 7, and a circuit element unit 8. Fig. 2 also illustrates an x-axis, a y-axis, and a z-axis. These three axes are the same in Fig. 3.

[0022] The optical cover 1 is mounted on the surface of the substrate 6 on the +z side, covers (encompasses) the light source 2, the optical filter 3, and the light receiving unit 4, forms a space capable of storing the gas G to be detected inside, and is a cover through which the gas G to be detected is introduced into and out of the space via a gas introduction port 11. The base of the optical cover 1 is made of, for example, resin, and has a plurality of planar or curved inner surfaces. The inner surface of the base of the optical cover 1 is covered with an infrared reflective film. In this embodiment, gold is used as the infrared reflective film, but this is not limited thereto. Silver, aluminum, or a dielectric multilayer film may be used as the infrared reflective film. Furthermore, a protective film such as silicon oxide or silicon nitride may be formed on the infrared reflective film as necessary to prevent corrosion of the metal film of the infrared reflective film. The infrared reflective film and the protective film may be formed by plating, sputtering, vacuum deposition, or the like.

[0023] The optical cover 1 serves to efficiently guide the infrared rays emitted from the light source 2 to the light receiving unit 4 as an optical path, by reflecting the infrared rays emitted from the light source 2 with an infrared reflective film, so that at least a part of the reflected light reaches the light receiving unit 4 via the optical filter 3. In addition, the shape, size, and position of the gas introduction port 11 for the gas G of the optical cover 1 in Fig. 2 are merely examples, and are not limited thereto.

[0024] 3, the light source 2 is a MEMS (Micro Electro Mechanical Systems) type light source mounted on the upper surface (+z side surface) of the substrate 6, and has, for example, a membrane M having a membrane structure. The light source 2 has an electrode 231 and a pad P1 provided on the +x direction side, and an electrode 232 and a pad P2 provided on the -x direction side.

[0025] The light source 2 has a configuration in which, for example, a light source layer support layer, a light source layer 21, an electrode support layer, and a protective layer (all not shown) are laminated from the -z direction side to the +z direction side as a membrane M provided on a Si substrate. The light source layer support layer has, for example, a silicon oxide film, a silicon nitride film, and an HLD (High temperature Low pressure Dielectric layer) layer from the -z direction side to the +z direction side. The light source layer 21 is a thin film heater serving as a light source (metal) layer (light emitting layer) that radiates infrared rays, and is made of, for example, MoSi 2 The light source layer emits infrared rays having an intensity and wavelength dependency that depend on the surface temperature and surface emissivity when the membrane M is heated by energization. The electrode support layer has, for example, two insulator layers from the -z direction side to the +z direction side, and supports the electrodes. The protective layer is a top protective layer made of an insulator.

[0026] The light source layer 21 is electrically connected to the electrodes 231 and 232. The pad P1 is a pad for wire bonding and is electrically connected to the electrode 231. The pad P2 is a pad for wire bonding and is electrically connected to the electrode 232. The pads P1 and P2 are wire bonded to terminals of a wiring pattern on the substrate 6, and when a voltage is applied, electricity is applied to the light source layer 21, causing infrared rays to be emitted.

[0027] The light source 2 as a MEMS type light source is small and low-profile, and can realize miniaturization as a sensor module. In addition, the light source 2 as a MEMS type light source has characteristics such as a long life, low power consumption, and short response time, and can achieve low power consumption as a whole sensor module. The short response time of the MEMS type light source makes it possible to shorten the standby time after power is turned on when performing intermittent driving, and can reduce the average power consumption.

[0028] Furthermore, as a MEMS-type light source, light source 2 can directly utilize the light emitted from the surface of the high-temperature part, making it possible to apply it to the detection of gases that have absorption bands at long wavelengths. In addition, the area that emits infrared light from light source 2 is patterned with high precision on the flat surface of the Si substrate of membrane M, and individual variations in the direction of emission are extremely small. This reduces variations in the amount of light received when a sensor module is constructed using light source 2, contributing to improved product yields. Furthermore, light source 2 is easily mass-produced because it is produced in bulk using MEMS technology based on silicon wafers.

[0029] The light source 2 is a surface-mounted component that is directly mounted (COB: Chip On Board) on the substrate 6. However, the light source 2 is not limited to this, and may be a DIP (Dual Inline Package) component (such as a CAN package).

[0030] As shown in FIG. 1, the optical filter 3 is a filter that is provided to cover the light receiving surface of the light receiving unit 4 and transmits light (infrared rays) in a wavelength range (band) corresponding to the absorption wavelength specific to the gas G to be detected. In this way, the transmission wavelength of the optical filter 3 is designed to match the absorption wavelength specific to the gas G to be detected, thereby suppressing the change in the amount of light caused by gases other than the gas G to be detected, and improving the signal-to-noise ratio of the detection signal of the light receiving unit 4. More specifically, the optical filter 3 filters infrared rays in a wide wavelength range that are incident from the light source 2 and pass through the gas G, and transmits infrared rays in a wavelength range corresponding to the absorption wavelength of the gas G. The optical filter 3 may be a bandpass filter that transmits only wavelengths in a specific frequency band, or a longpass filter that transmits an infrared band in a wavelength range corresponding to the absorption wavelength of the gas G as a transmission wavelength equal to or greater than the cut-on wavelength. The longpass filter is a filter that cuts off light on the shorter wavelength side than the specific cut-on wavelength and transmits light on the longer wavelength side.

[0031] The optical filter 3 has, for example, a silicon substrate as a substrate, and a dielectric multilayer film or a multilayer film made of an infrared-transmitting material such as Si, Ge, sulfide, and fluoride. The silicon substrate is a planar silicon substrate. The material of the substrate is not limited to silicon, and Ge (germanium), quartz, alumina, BaF2 (barium fluoride), CaF2 (calcium fluoride), etc. can be used. The multilayer film is a film with a plurality of layers provided on both sides of the silicon substrate. The planar shape of the optical filter 3 is circular, but is not limited thereto, and may be other shapes such as rectangular.

[0032] The light receiving unit 4 is mounted on the +z side of the substrate 6 and is a thermopile type optical sensor (infrared sensor) having multiple thermocouples, which detects the amount of incident infrared light and outputs a detection signal as an analog electrical signal. However, the light receiving unit 4 is not limited to a thermopile type infrared sensor, and may be an infrared sensor of various types shown in the following Table I.

[0033] [Table 1]

[0034] Furthermore, the light receiving unit 4 is, for example, an infrared sensor in a CAN package, but is not limited to this configuration.

[0035] The signal processing unit 5 is mounted on a planar area other than the optical cover 1 on the +z side surface of the substrate 6, and is an AFE (Analog Front End)-IC (Integrated Circuit) serving as an electronic component (processor) that performs signal processing on the detection signal of the light receiving unit 4. The signal processing unit 5 amplifies and AD converts the analog detection signal of the light receiving unit 4, and generates a difference value between the detection value when the light source 2 is on and the detection value when the light source 2 is off. The signal processing unit 5 performs corrections for temperature and individual variations of the optical gas sensor device 100 on the difference value of the detection values, and generates various status signals from the difference value of the digital detection values. The signal processing unit 5 outputs the difference value of the digital detection values ​​and the status signal.

[0036] The substrate 6 is a PCB (Printed Circuit Board) in which conductive wiring is printed on a plate such as glass epoxy resin. On the +z side of the substrate 6, an optical cover 1, a light source 2, a light receiving unit 4, a signal processing unit 5, a connector 7, and a circuit element unit 8 are mounted. The +z side of the substrate 6 is approximately parallel to the optical filter 3 and the light receiving surface of the light receiving unit 4.

[0037] The connector 7 is mounted on a flat area on the +z side of the substrate 6 other than the optical cover 1 and the signal processing unit 5, and is a connector for outputting various digital signals output from the signal processing unit 5 to an information processing unit (MCU 200) of a downstream device 230 (assumed to be an alarm device). The connector 7 is connected to the MCU 200 of the device 230 via a cable having a plug.

[0038] The circuit element section 8 is a circuit element such as a switch such as a switch 81, a chip resistor, or a chip capacitor.

[0039] Next, the optical path of infrared rays in the optical gas sensor device 100 will be described. In the optical gas sensor device 100, infrared rays emitted from the light source 2 in the +z direction are absorbed by the gas G to be detected inside the optical cover 1. The infrared rays are reflected by the inner surface of the optical cover 1 in the ±x, ±y, and ±z directions while being absorbed, filtered by the optical filter 3, and reach and enter the light receiving unit 4. This optical path is a linear optical path on a plane, or an optical path that is reflected by the inner surface of the optical cover 1 and bent. The inner surface of the optical cover may be flat, curved, or a combination of these, or may be a pipe shape with a polygonal, circular, or elliptical cross section that is drawn around three-dimensionally.

[0040] Next, the circuit configuration of the optical gas sensor device 100 will be described with reference to Fig. 4. Fig. 4 is a diagram showing the circuit configuration of the optical gas sensor device 100 and the device 230.

[0041] As shown in Fig. 4, the optical gas sensor device 100 has a circuit configuration including a light source 2, a light receiving unit 4, a signal processing unit 5, and a circuit element unit 8. The signal processing unit 5 has an amplifier 50, a temperature sensor 511, a clock generating unit 512, a multiplexer 52, an AD (Analog to Digital) converter 53, an NVM (Non-Volatile Memory) 54, a data processor 55, a communication unit 56, and a status output terminal 57. The circuit element unit 8 has a switch 81, and resistors 82 and 83. The optical gas sensor device 100 is connected to an MCU 200 of a device 230. The device 230 includes the MCU 200, resistors 211 and 212, a capacitor 213, and an alarm unit 214.

[0042] The MCU 200 is a control unit that controls each unit of the device 230, and includes a communication unit 201. The communication units 56, 201 are serial communication units that use an I2C communication method. The communication unit 56 of the optical gas sensor device 100 and the communication unit 201 are connected to each other through a clock line SCL and a data line SDA by the connector 7. The communication unit 201 generates a clock signal and outputs it to the communication unit 56, and transmits and receives a data signal to and from the communication unit 56. The communication method of the communication units 56, 201 is not limited to IC2, and other serial communication methods such as UART (Universal Asynchronous Receiver / Transmitter) and CSI (Clocked Serial Interface) can also be used. The MCU 200 is also connected to a status output terminal 57 via a signal line 220, and receives a status signal of the optical gas sensor device 100 from the optical gas sensor device 100, which will be described later. The MCU 200 controls the notification unit 214 based on the status signal of the optical gas sensor device 100. The notification unit 214 notifies the status of the optical gas sensor device 100 based on the status signal by displaying, outputting sound, or the like under the control of the MCU 200, as will be described later.

[0043] Further, the power supply unit of the power supply voltage VDD is connected to a clock line SCL (serial clock) via a resistor 211, to a data line SDA (serial data) via a resistor 212, and to ground via a capacitor 213. The resistors 211 and 212 are pull-up resistors. Noise is removed from the power supply voltage VDD by the capacitor 213.

[0044] The light source 2 and the switch 81 are connected in series between the power supply of the power supply voltage VDD and the ground. The switch 81 is a switch for switching the light source 2 on / off. The switch 81 is composed of an NMOSFET (N-channel Metal-Oxide-Semiconductor Field Effect Transistor) or a CMOS (Complementary Metal-Oxide-Semiconductor), and a gate as a control terminal is connected to the signal processing unit 5. The resistors 82 and 83 are connected in series between the power supply of the power supply voltage VDD and the ground. The node between the resistors 82 and 83 is connected to the input terminal of the light receiving unit 4. The power supply voltage divided by the resistors 82 and 83 is input to the input terminal of the light receiving unit 4. The light receiving unit 4 detects infrared rays IR emitted from the light source 2 and input through the gas G and the optical filter 3, and outputs an analog detection signal from the output terminal.

[0045] The power supply voltage divided by the resistors 82 and 83 is input to a first input terminal of the amplifier 50. The output terminal of the light receiving unit 4 is connected to a second input terminal of the amplifier 50. The amplifier 50 amplifies the analog detection signal output from the light receiving unit 4 using the input divided power supply voltage and the detection signal input from the light receiving unit 4.

[0046] The output terminal of the amplifier 50 is connected to one of the multiple input terminals of the multiplexer 52. The temperature sensor 511 is connected to one of the multiple input terminals of the multiplexer 52, detects the temperature inside the optical cover 1, generates an analog temperature signal, and outputs the generated analog temperature signal to the corresponding input terminal of the multiplexer 52.

[0047] The clock generating unit 512 is a clock generating circuit, which generates a digital clock signal and outputs it to the data processor 55. The data processor 55 acquires the current time based on the clock signal input from the clock generating unit 512. The clock generating unit 512 may be configured to be connected to the AD converter 53, generate an analog clock signal, and output it to the AD converter 53.

[0048] For example, in response to signal selection control from the data processor 55, the multiplexer 52 multiplexes the amplified analog detection signal input from the light receiving unit 4, the analog temperature signal input from the temperature sensor 511, and the divided power supply voltage into one analog multiplexed signal and outputs it to the input terminal of the AD converter 53. The AD converter 53 converts the input multiplexed signal into a multiplexed signal of the digital detection signal of the light receiving unit 4, the digital temperature signal, and the digital divided power supply voltage, and outputs it to the data processor 55.

[0049] The NVM 54 is a memory that stores information in a non-volatile manner, and stores, for example, a threshold M1 of the difference in the detection value between when the light source is on and when the light source is off, a threshold A of the gas concentration value of the gas G, a threshold N of the light source voltage value, an initial failure determination period, a non-determination period, and a correction coefficient, which will be described later. The threshold M1 is a threshold for distinguishing between a fault state and a normal state (a state without a fault state) of the optical gas sensor device 100, and is a lower limit threshold of the detection difference value between when the light source is on and when the light source is off when gas G is introduced in a normal state. The threshold A is a threshold for distinguishing between an alarm state and a normal state (a state without an alarm state) of the optical gas sensor device 100, and is an upper limit threshold of the gas concentration value of the gas G in the normal state.

[0050] The threshold N is a threshold for distinguishing between an abnormal state and a normal state (a state without an abnormal state) of the voltage value (light source voltage value) applied to the light source 2, and is the upper limit threshold of the light source voltage value in the normal state. The threshold N is, for example, 3.3 [V].

[0051] The initial failure judgment period is a waiting time until the judgment of the initial state failure after the power supply of the optical gas sensor device 100 is turned on, and is, for example, 2 [sec] that is empirically and experimentally set in advance. The non-judgment period is a waiting time for stabilizing a difference value of the detection signal of the light receiving unit 4 (described later) after the initial failure judgment of the optical gas sensor device 100, and is, for example, 38 [sec] that is empirically and experimentally set in advance. The correction coefficient is a correction coefficient for performing correction processes such as temperature correction and correction of individual variations of the optical gas sensor device 100 on the detection value of the light receiving unit 4.

[0052] The data processor 55 is a control unit (processor) that performs signal processing on the detection signal of the light receiving unit 4, and includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), and a storage unit. The CPU controls the optical gas sensor device 100. The RAM is a volatile memory that temporarily stores information. The storage unit is composed of a non-volatile memory (NVM: Non-Volatile Memory) such as a ROM (Read Only Memory), and various data and programs are stored in the storage unit. The storage unit may be configured to be shared with the data processor 55 by the NVM 54, which is a non-volatile memory provided separately from the data processor 55. Note that, as the NVM 54, a mask ROM, an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory), a flash memory, or the like can be used. In the data processor 55, the CPU reads out a program stored in the storage unit, loads it in the RAM, and performs various processes in cooperation with the loaded program. It is assumed that the storage unit stores a state signal generating program for executing a gas concentration measurement process described later.

[0053] The data processor 55 calculates the gas concentration value of the gas G using the digital detection signal and digital temperature signal of the light receiving unit 4 input from the multiplexer 52 and the correction coefficient stored in the NVM 54. The data processor 55 generates various status signals (fault signal, alarm signal, and monitoring signal, which will be described later) of the optical gas sensor device 100 according to comparison and correction of the calculated gas concentration value and light source voltage value with the threshold value stored in the NVM 54. The data processor 55 transmits the gas concentration value to the MCU 200 of the device 230 via the communication unit 56. The data processor 55 also transmits a status signal of the optical gas sensor device 100 to the MCU 200 via the status output terminal 57 based on a predetermined format. The data processor 55 may be configured by a circuit such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0054] The communication unit 56 transmits and receives data signals (such as gas concentration values) to and from the communication unit 201 via the data line SDA.

[0055] Next, the operation of the data processor 55 of the signal processing unit 5 will be described as an operation of the optical gas sensor device 100 with reference to Figs. 5 to 9. Fig. 5 is a flowchart showing a status signal generation process. Fig. 6 is a flowchart showing a light source intermittent drive control process. Fig. 7 is a flowchart showing a measurement loop process of the status signal generation process of Fig. 5. Fig. 8 is a diagram showing a waveform of a status signal. Fig. 9 is a diagram showing various timings of the on / off waveform of the light source 2.

[0056] It is assumed that the optical gas sensor device 100 is connected to the MCU 200 of the device 230 in advance, and the gas G to be detected is introduced into the optical cover 1 from the gas introduction port 11. The optical gas sensor device 100 is powered off. As shown in the waveform of the "power off" status signal in Fig. 8, the output (status signal) from the status output terminal 57 of the signal processing unit 5 is always high. However, the "power off" status signal is always high when the pull-up resistor (not shown) of the signal line 220 of the device 230 to which the optical gas sensor device 100 is connected is on.

[0057] Then, the data processor 55 of the signal processing unit 5 executes a status signal generation process in accordance with a status signal generation program stored in an internal storage unit, triggered by the user turning on the power supply to the optical gas sensor device 100 (step S10).

[0058] First, the data processor 55 initializes the signal processor 5 and prepares it for driving (step S11). Then, the data processor 55 fixes the PWM (Pulse Width Modulation) of the status signal to be output low, and controls the switch 81 to fix the light source 2 to off (step S12). In step S12, as shown by the waveform of the status signal for "initial operation" in FIG. 8, it is always set to low.

[0059] Then, the data processor 55 reads out the initial failure determination period stored in the NVM 81, and controls the switch 81 based on the clock signal generated by the clock generating unit 512 to start initial intermittent light source drive control of turning on / off the light source 2 (step S13). After step S13, the intermittent light source drive control process shown in Fig. 6 is executed in parallel with the status signal generation process. The initial intermittent light source drive control is an intermittent drive control with a repeating pattern of the light source off time being, for example, 200 [ms] and the light source on time being, for example, 200 [ms] in the waveform of the light source off (light-out) time and the light source on (light-emitting) time of the intermittent drive control of the light source 2 shown in Fig. 9.

[0060] Here, the light source intermittent drive control process will be described with reference to FIG. 6. First, the data processor 55 controls the switch 81 to turn off the light source 2, and waits for the measurement of the detection value of the light receiving unit 4, the substrate temperature, and the voltage value of the light source 2 when the light source is off based on the clock signal generated by the clock generating unit 512 (step S31). As shown in FIG. 9, in the intermittent drive control of the light source 2, at time t11 (, t21 ...) as the final timing (before rising) of the light source on time, the detection value of the detection signal of the light receiving unit 4 when the light source is off, the substrate temperature of the substrate 6 by the temperature sensor 511, and the light source voltage value of the light source 2 are measured. That is, in step S31, the data processor 55 waits from the start of the light source off time until the time of the measurement timing of the final measurement value. The waiting time of step S31 corresponding to the initial intermittent drive control of step S13 is, for example, 200 [ms].

[0061] Then, the data processor 55 acquires the detection value from the detection signal of the light receiving unit 4, acquires the substrate temperature from the temperature sensor 511, and acquires the divided power supply voltage between the resistors 82 and 83. Furthermore, the data processor 55 calculates the voltage value to be applied to the light source 2 from the divided power supply voltage as the light source voltage value, and measures the detection value, the substrate temperature, and the light source voltage value when the light source is off (step S32).

[0062] Then, the data processor 55 controls the switch 81 to turn on the light source 2, and waits for the measurement of the detection value of the light receiving unit 4, the substrate temperature, and the voltage value of the light source 2 when the light source is on, based on the clock signal generated by the clock generating unit 512 (step S33). As shown in FIG. 9, in the intermittent drive control of the light source 2, at time t12 (, t22 ...) which is the final timing (before the falling edge) of the light source off time, the detection value of the light receiving unit 4 when the light source is off and the substrate temperature of the substrate 6 by the temperature sensor 511 are measured. That is, in step S33, the data processor 55 waits from the start of the light source on time until the time when the final measured value is measured. The waiting time of step S33 corresponding to the initial failure determination period of step S13 is, for example, 200 [ms].

[0063] Then, the data processor 55 acquires the detection value from the detection signal of the light receiving unit 4 and acquires the substrate temperature from the temperature sensor 511, and measures the detection value and the substrate temperature when the light source is on (step S34). Note that in step S34, the data processor 55 may be configured to measure the voltage value (light source voltage value) applied to the light source 2, similarly to step S32.

[0064] Then, the data processor 55 reads out the correction coefficient from the NVM 54, and calculates the difference value of the detection values, the average substrate temperature, and the gas concentration value using the detection values ​​and the substrate temperature measured in steps S32 and S34 when the light source is off and when the light source is on, and the read out correction coefficient (step S35). The process proceeds to step S31. Step S35 is executed at time t13 (, t23...) immediately after time t12 (, t22...) of step S34, as shown in FIG.

[0065] Here, the process of step S35 will be described in more detail. First, the data processor 55 subtracts the detection value when the light source is off, acquired in step S32, from the detection value when the light source is on, acquired in step S34, to calculate a difference value of the detection values ​​of the light receiving unit 4. Then, the data processor 55 calculates an average substrate temperature, which is an average value of the substrate temperature when the light source is off, measured in step S32, and the substrate temperature when the light source is on, measured in step S34. Then, the data processor 55 calculates a gas concentration value using the calculated difference value of the detection values, the average substrate temperature, and a correction coefficient. Also, the data processor 55 transmits the calculated gas concentration value to the MCU 200 of the device 230 via the communication unit 56.

[0066] 5, the data processor 55 determines whether or not the initial failure determination period read out in step S13 has elapsed since the light source was turned off (step S14) based on the clock signal generated by the clock generating unit 512. If the initial failure determination period has not elapsed (step S14; NO), the process proceeds to step S14.

[0067] When the initial failure determination period has elapsed (step S14; YES), the data processor 55 reads a predetermined failure condition from the NVM 54. Further, the data processor 55 determines whether to detect an initial failure of the optical gas sensor device 100 based on whether the light source voltage value obtained in step S32 of the initial intermittent drive control and the difference value between the detection values when the light source is on and when the light source is off calculated in step S35 satisfy the read predetermined failure condition (step S15). The predetermined failure condition has, for example, as a threshold for failure occurrence, a threshold value M1 for the difference value between the detection values when the light source is on and when the light source is off, and a threshold value N for the light source voltage value.

[0068] In step S15, based on whether the difference value between the detection values when the light source is on and when the light source is off calculated in step S35 is < M1 and the light source voltage value obtained in step S32 ≥ N, it is determined whether an initial failure has occurred in the optical gas sensor device 100.

[0069] When an initial failure is detected (step S15; YES), the data processor 55 sets the output status signal to the PWM in the failure mode to make it a failure signal (step S16). By step S16, the "at failure" PWM status signal shown in FIG. 8 is generated as a failure signal and output to the device 230. The failure signal becomes, for example, an intermittent signal with a low period of 75 [msec], a high period of 300 [msec], and a duty ratio of 80%. When the MCU 200 of the device 230 receives the failure signal via the signal line 220, it causes the notification unit 214 to output a notice of the failure of the optical gas sensor device 100.

[0070] Then, the data processor 55 reads out the non-determination period stored in the NVM 81, and controls the switch 81 based on the clock signal generated by the clock generating unit 512 to start normal intermittent drive control of turning on / off the light source 2 (step S17). After step S17, in the intermittent light source drive control being executed in parallel with the status signal generation process, the on / off interval of the normal intermittent drive control process is applied to steps S31 and S33. The intermittent light source drive control is an intermittent drive control with a repeating pattern in which the light source off time is, for example, 750 [msec] and the light source on time is, for example, 250 [msec] in the waveform of the light source off time and the light source on time of the intermittent drive control of the light source 2 shown in FIG.

[0071] Then, the data processor 55 starts counting the non-determination period based on the clock signal generated by the clock generating unit 512, and stops outputting the status signal (step S18). The non-determination period is a waiting period until the gas concentration value stabilizes, and since the gas concentration value is not stable, the output of the gas concentration value and the status signal is stopped. Then, the data processor 55 determines whether the non-determination period has elapsed since the start of counting in step S18 based on the clock signal generated by the clock generating unit 512 (step S19). If the non-determination period has not elapsed (step S19; NO), the process proceeds to step S19.

[0072] If the non-determination period has elapsed (step S19; YES), the data processor 55 sets the status signal to be output to PWM in monitoring mode and sets it as a monitoring signal (step S20). In step S20, the PWM status signal "during monitoring" shown in Fig. 8 is generated as a monitoring signal and output to the device 230. The monitoring signal is an intermittent signal with, for example, a low period of 300 [msec], a high period of 75 [msec], and a duty ratio of 20%.

[0073] Then, the data processor 55 executes a measurement loop process (step S21). Here, the measurement loop process of step S21 will be described with reference to Fig. 7. As shown in Fig. 7, first, the data processor 55 acquires a difference value of the detection values ​​of the light receiving unit 4, an average substrate temperature, and a gas concentration value (step S41). Step S41 is a step for acquiring a difference value of the detection values ​​of the light receiving unit 4, an average substrate temperature, and a gas concentration value calculated in the immediately preceding step S35 in the light source intermittent drive control process.

[0074] Then, the data processor 55 reads out a predetermined alarm determination threshold value A from the NVM 54, and judges whether or not an alarm concentration value that is a gas concentration value requiring an alarm is detected based on whether or not the gas concentration value acquired in step S41 is greater than A (step S42). When an alarm concentration value is detected (step S42; YES), the data processor 55 sets the output status signal to PWM in alarm mode to become an alarm signal (step S43). In step S43, a PWM status signal for "alarm" shown in FIG. 8 is generated as an alarm signal and output to the device 230. The alarm signal is, for example, an intermittent signal with a low period of 150 [msec], a high period of 225 [msec], and a duty ratio of 60%. When the MCU 200 of the device 230 receives the alarm signal from the signal processing unit 5 via the signal line 220, it causes the annunciation unit 214 to output an alarm indicating that the gas concentration value is high. The process proceeds to step S41.

[0075] If the warning concentration value is not detected (step S42; NO), the data processor 55 reads out a predetermined fault condition from the NVM 54. Furthermore, the data processor 55 determines whether or not to detect a fault during normal operation (normal fault) of the optical gas sensor device 100, depending on whether or not the light source voltage value acquired in step S41 during normal intermittent drive control and the difference between the detection values ​​when the light source is on and when the light source is off acquired in step S41 satisfy the read-out predetermined fault condition (step S44). The predetermined fault condition may, for example, include a threshold value M1 of the difference between the detection values ​​when the light source is on and when the light source is off, and a threshold value N of the light source voltage value, as a threshold value for fault occurrence.

[0076] In step S44, similar to step S15 of the initial failure determination, based on whether the difference value <M1 of the detection values when the light source is on and when the light source is off obtained in step S41 and whether the light source voltage value obtained in step S41 is ≧N, the occurrence of a normal failure in the optical gas sensor device 100 is determined. However, it is not limited thereto, and a configuration may be adopted in which the failure determination method (such as failure conditions) for the initial failure determination is different from the failure determination method (such as failure conditions) for the normal failure determination.

[0077] When a normal failure is not detected (step S44; NO), the data processor 55 sets the output status signal to the PWM in the monitoring mode to obtain a monitoring signal (step S45). Step S45 is the same as step S20. The process proceeds to step S41.

[0078] When a normal failure is detected (step S44; YES), the data processor 55 sets the output status signal to the PWM in the failure mode to obtain a failure signal (step S46). Step S46 is the same as step S16. The process proceeds to step S41.

[0079] Next, with reference to FIGS. 10(a) to 11, a specific example of gas concentration value detection will be described. FIG. 10(a) is a diagram showing the time characteristics of the detection value when the light source is on. FIG. 10(b) is a diagram showing the time characteristics of the detection value when the light source is off. FIG. 11 is a diagram showing the time characteristics of the difference value of the detection values.

[0080] As shown in FIG. 10(a), from 0 (start of light source control) to 8 [min], R32 gas was not introduced into the space in which the optical gas sensor device 100 was installed, and the gas concentration value of R32 in the optical cover 1 was set to 0 [ppm]. Similarly, from 8 to 11 [min], R32 gas was introduced into the space, and the gas concentration value of R32 in the optical cover 1 was set to 5000 [ppm]. Similarly, from 11 to 14 [min], R32 gas was further introduced into the space, and the gas concentration value of R32 in the optical cover 1 was set to 10000 [ppm]. Similarly, from 14 to 17 [min], R32 gas was further introduced into the space, and the gas concentration value of R32 in the optical cover 1 was set to 15000 [ppm].

[0081] In Fig. 10(a), the detection value of the light receiving unit 4 when the light source is on (emitting light) is shown by a solid line versus time in the above-mentioned R32 gas state, and the substrate temperature [°C] is similarly shown by a dotted line versus time. The characteristic curve of the substrate temperature [°C] versus time is common to Figs. 10(a) to 11.

[0082] In Fig. 10(b), the detection value of the light receiving unit 4 when the light source is off (extinct) is shown by a solid line against time. In Fig. 11, the difference value of the detection value of the light receiving unit 4 against time (detection value when the light source is on - detection value when the light source is off) is shown by a solid line in the above-mentioned R32 gas state.

[0083] The light receiving unit 4 as an infrared sensor may fluctuate in detection value due to a sudden change in the substrate temperature, and may not be able to read infrared rays sufficiently. Specifically, as shown in Fig. 10(a), in order to calculate the gas concentration value from the detection value when the light source is on, it is necessary to wait for a standby time of 8 minutes or more from the start of the optical gas sensor device 100 until the increase in the substrate temperature settles down. In particular, in the optical gas sensor device 100, since the light source 2 and the light receiving unit 4 are mounted on the same substrate 6, the heat generated by the light source 2 is easily conducted to the light receiving unit 4 via the substrate 6, and the detection value of the light receiving unit 4 is likely to become unstable.

[0084] In contrast, by using a configuration that takes the difference between the detection values ​​when the light source is on and when the light source is off as shown in FIG. 11, the difference between the detection values ​​stabilizes in a short time, and the standby time can be shortened to approximately 30 seconds.

[0085] As described above, according to this embodiment, the optical gas sensor device 100 includes the light source 2 that emits infrared rays to the gas G to be detected, the optical filter 3 that transmits infrared rays having a wavelength corresponding to the absorption wavelength of the gas G to be detected, the light receiving unit 4 that detects the infrared rays incident through the optical filter 3 and generates a detection signal, a substrate 6 on which the light source 2 and the light receiving unit 4 are mounted, and a signal processing unit 5. The signal processing unit 5 controls the intermittent on / off drive of the light source 2, and calculates the gas concentration value of the gas G to be detected from a difference value obtained by subtracting the detection value of the detection signal when the light source 2 is off from the detection value of the detection signal when the light source 2 is on.

[0086] Therefore, in a configuration in which the light source 2 and the light receiving unit 4 are mounted on the same substrate 6 and the light receiving unit 4 is easily affected by the heat of the light source 2, it is possible to suppress fluctuations in the detection signal of gas G due to changes in substrate temperature, and to stabilize the gas concentration value. In addition, the time from start-up to normal measurement of the gas concentration value can be shortened.

[0087] The optical gas sensor device 100 also includes a temperature sensor 511 that detects the substrate temperature of the substrate 6. The signal processor 5 calculates a gas concentration value from the substrate temperature and the difference between the detection values ​​of the light receiver 4. More specifically, the temperature sensor 511 detects the substrate temperature when the light source is on and the substrate temperature when the light source is off. The signal processor 5 calculates an average substrate temperature, which is the average of the substrate temperature when the light source 2 is on and the substrate temperature when the light source 2 is off, and calculates a gas concentration value from the average substrate temperature and the difference between the detection values ​​of the light receiver 4. This makes it possible to calculate a stable gas concentration value by suppressing the influence of the difference between the substrate temperatures when the light source 2 is on and when the light source 2 is off.

[0088] Furthermore, the light source 2 is a MEMS type light source, which can shorten the response time and reduce the power consumption of the optical gas sensor device 100.

[0089] The optical gas sensor device 100 also includes an optical cover 1 provided on a substrate 6 so as to cover the light source 2 and the light receiving section 4, and arranged so that infrared light passing through an optical filter 3 is reflected on its inner surface and at least a part of the reflected light reaches the light receiving section 4, and a gas inlet port 11 for introducing a gas G to be detected into the optical cover 1. Therefore, the gas concentration value of the gas G in the optical cover 1 can be accurately detected.

[0090] Furthermore, the signal processor 5 determines that the optical gas sensor device 100 has a fault when the difference between the detection values ​​when the light source is on and when the light source is off is lower than a threshold value M1 as a predetermined first threshold value and the light source voltage value applied to the light source 2 is equal to or higher than a threshold value N as a predetermined second threshold value. This makes it possible to accurately determine that the optical gas sensor device 100 has a fault.

[0091] Moreover, the signal processing unit 5 determines the state of the optical gas sensor device 100 from the gas concentration value, and outputs a state signal of the determined state to the external device 230. Therefore, a state signal of the optical gas sensor device 100 based on a stable and accurate gas concentration value can be output to the device 230.

[0092] The above description of the embodiment is merely an example of the optical gas sensor device, the gas detection method, and the program according to the present invention, and the present invention is not limited to this.

[0093] For example, in the above embodiment, the data processor 55 is configured to calculate the difference value of the detection value when the light source 2 is on and when the light source is off in step S35 of the light source intermittent drive process. However, the present invention is not limited to this configuration. For example, the data processor 55 may be configured to calculate a "second difference value obtained by subtracting the amount of change in the detection value for two consecutive times when the light source 2 is off from the first difference value of the detection value when the light source 2 is on and when the light source is off" instead of the "difference value of the detection value when the light source 2 is on and when the light source is off". According to this configuration, the stabilization of the second difference value can be made faster than the first difference value, and the waiting time in FIG. 11 can be further shortened. In addition, the data processor 55 may be configured to calculate the gas concentration value using the calculated second difference value, the substrate average temperature, and a correction coefficient.

[0094] In the above embodiment, the data processor 55 is configured to calculate the gas concentration value and generate the status signal by comparing it with various thresholds, but this is not limited to the above. The data processor 55 may be configured to calculate a value corresponding to the gas concentration value and generate the status signal by comparing the value corresponding to the gas concentration value with various corresponding thresholds.

[0095] In the above embodiment, the optical gas sensor device 100 includes one set of the light source 2, the optical filter 3, and the light receiving unit 4, but the present invention is not limited to this. The optical gas sensor device may include multiple sets of the light source 2, the optical filter 3, and the light receiving unit 4.

[0096] Furthermore, the detailed configuration and operation of the optical gas sensor device 100 in the above embodiment may be modified as appropriate without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0097] 100 Optical gas sensor device G Gas 1 Optical cover 11 Gas inlet port 12 Contamination Filter 2 light source 21 Light source layer 231,232 electrodes P1, P2 pad M Membrane 3 Optical Filters 4 Light receiving section 5. Signal Processing Section 50 Amps 511 Temperature Sensor 512 Clock Generation Unit 52 Multiplexer 53 A / D converter 54 NVM 55 Data Processor 56 Communications Department SCL Clock line SDA Data line 6 Substrate 7 Connectors 8 Circuit Element Section 81 Switch 82,83 Resistance 230 Equipment 200 MCU 201 Communications Department 211,212 Resistance 213 Capacitor 214 Information Department 220 Signal Line

Claims

1. A light source that emits infrared rays to a gas to be detected; an optical filter that transmits infrared light having a wavelength corresponding to an absorption wavelength of the gas to be detected; a light receiving unit that detects infrared rays incident through the optical filter and generates a detection signal; a substrate on which the light source and the light receiving unit are mounted; and a signal processing unit that controls intermittent driving of the light source by turning it on and off, and calculates a gas concentration value of the gas to be detected from a difference value obtained by subtracting a detection value of a detection signal when the light source is off from a detection value of a detection signal when the light source is on.

2. a temperature sensor for detecting a temperature of the substrate; 2. The optical gas sensor device according to claim 1, wherein the signal processing unit calculates the gas concentration value from the substrate temperature and the difference value.

3. the temperature sensor detects a substrate temperature when the light source is on and a substrate temperature when the light source is off; 3. The optical gas sensor device according to claim 2, wherein the signal processing unit calculates an average substrate temperature which is an average of the substrate temperature when the light source is on and the substrate temperature when the light source is off, and calculates the gas concentration value from the average substrate temperature and the difference value.

4. 2. The optical gas sensor device according to claim 1, wherein the light source is a MEMS type light source.

5. an optical cover provided on the substrate so as to cover the light source and the light receiving unit, the infrared light having passed through the optical filter being reflected on an inner surface of the optical cover, and at least a portion of the reflected light reaching the light receiving unit; 2. The optical gas sensor device according to claim 1, further comprising a gas inlet portion for introducing the gas to be detected into the optical cover.

6. 2. The optical gas sensor device according to claim 1, wherein the signal processing unit determines that the optical gas sensor device is faulty when a difference value obtained by subtracting a detection value of the detection signal when the light source is off from a detection value of the detection signal when the light source is on is lower than a predetermined first threshold value and a voltage value applied to the light source is equal to or higher than a predetermined second threshold value.

7. 7. The optical gas sensor device according to claim 1, wherein the signal processing unit determines a state of the optical gas sensor device from the gas concentration value, and outputs a state signal of the determined state to an external device.

8. A light source that emits infrared rays to a gas to be detected; an optical filter that transmits infrared light having a wavelength corresponding to an absorption wavelength of the gas to be detected; a light receiving unit that detects infrared rays incident through the optical filter and generates a detection signal; a substrate on which the light source and the light receiving unit are mounted, A gas detection method including a signal processing step of intermittently controlling the on / off of the light source and calculating a gas concentration value of the gas to be detected from a difference value obtained by subtracting a detection value of a detection signal when the light source is off from a detection value of a detection signal when the light source is on.

9. A light source that emits infrared rays to a gas to be detected; an optical filter that transmits infrared light having a wavelength corresponding to an absorption wavelength of the gas to be detected; a light receiving unit that detects infrared rays incident through the optical filter and generates a detection signal; a substrate on which the light source and the light receiving unit are mounted, a signal processing unit that performs intermittent drive control by turning on / off the light source, and calculates a gas concentration value of the gas to be detected from a difference value obtained by subtracting a detection value of a detection signal when the light source is off from a detection value of a detection signal when the light source is on; A program to function as a

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