JP2017015516A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor that corrects an influence of deterioration of a light source with high accuracy.SOLUTION: A gas sensor 100 of the present invention comprises: a first storage unit 71 that stores a first parameter for calculating gas density; a first density computation unit 61 that, when a first light emitting unit 41 emits light, calculates first gas density from sensor signals S1A, S2A to be output from each of first sensor unit 51 and second sensor unit 52, first temperature information to be output from a temperature measurement unit 12, and the first parameter; a second storage unit 72 that stores a second parameter for calculating the gas density; and a second gas density computation unit 62 that, when a second light emitting unit 42 emits light, calculates second gas density from sensor signals S1B, S2B to be output from each of first sensor unit and second sensor unit, second temperature information to be output from the temperature measurement unit, and the second parameter.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas sensor, and more particularly to a gas sensor capable of correcting the influence of deterioration of a light source in measurement of gas concentration with high accuracy.

Light-emitting elements are used in many applications. In addition to indoor / outdoor lighting applications, optical devices using light-emitting elements that emit light of a specific wavelength (sterilizers using ultraviolet light, reflected light) It is also used in the distance measuring device used. Further, in combination with a light emitting element and a light receiving element, a light receiving and emitting device that detects a spatial state between the light emitting element and the light receiving element (an object / substance detection device in a specific space, a gas sensor using infrared light (for example, see Patent Document 1) ).
In particular, in recent years, the presence / absence and concentration measurement of gas have attracted attention, and in particular, the presence / absence and concentration measurement of environmental gases (eg, CO ₂ , NO, etc.) have attracted attention. Sensors that measure these gases with high accuracy include chemical reaction type gas sensors and optical type gas sensors. From the viewpoint of high measurement accuracy and little change over time, an optical gas sensor has attracted particular attention. The optical gas sensor includes a light source that emits a wavelength that is absorbed by molecules of a gas to be measured, and a sensor that reads the signal.

The above environmental gas strongly absorbs light having a wavelength around several μm (for example, around 4.3 μm in the case of CO ₂ ), so that a light source that emits light in this wavelength band and light in this wavelength band A sensor that outputs a signal corresponding to the intensity is required. LEDs that emit light in the middle to far infrared region are mainly used for non-dispersive infrared (hereinafter referred to as NDIR) gas sensors and are under development.

Special table 2001-503865 gazette

  However, the light emitting characteristics of the light emitting element vary depending on the usage environment and changes over time. Specifically, a change in emission intensity and a change in emission wavelength can be mentioned. In the case of a light receiving / emitting device that detects the spatial state (transmission characteristics) from the light emitting element to the light receiving element based on the output of the light receiving element described above, if the light emission characteristic of the light emitting element changes, the output from the light receiving element The spatial state cannot be detected accurately. Therefore, in the case of an NDIR type gas sensor, if the intensity of the light source changes, the absolute value of the measured gas concentration shifts, so that there is a problem that accurate concentration measurement cannot be performed.

As a method for reducing such a change in light emission characteristics, light emitted from the light emitting element is detected by a light receiving element for monitoring, and a change in the light emission characteristic of the light emitting element is detected based on the output of the light receiving element for monitoring. Examples of the method include monitoring and controlling the operation of the light emitting element and compensating the output of the light receiving element for detecting the state. However, the light reaching the light receiving element for monitoring is also affected by attenuation or the like in the space, similarly to the light reaching the light receiving element for state detection, and therefore cannot be accurately monitored when the state of this space changes. .
The present invention has been made in view of such problems, and an object of the present invention is to provide a gas sensor capable of correcting the influence of deterioration of a light source in gas concentration measurement with high accuracy. is there.

As a result of intensive studies to solve the above problems, the present inventor has come up with the following gas sensor.
A first aspect of the present invention includes a gas cell into which a measurement target gas is introduced, a first main surface, and a second main surface opposite to the first main surface, and the first main surface has a first main surface. A first substrate having a light emitting unit and a first sensor unit; a first main surface; and a second main surface facing the first main surface, wherein the second light emitting unit is disposed on the first main surface. And a second substrate provided with a second sensor unit, a first driving unit that drives the first light emitting unit, a second driving unit that drives the second light emitting unit, the first driving unit, and the The second driving unit measures the temperature of the driving control unit that controls the timing of driving the first light emitting unit and the second light emitting unit, the temperature of the first light emitting unit and / or the second light emitting unit, and temperature information. When the first light emitting unit emits light, the temperature measuring unit that outputs as the temperature measuring unit, the first storage unit that stores the first parameter for calculating the gas concentration, A first gas concentration based on a first a sensor signal and a second a sensor signal output from the sensor unit and the second sensor unit, first temperature information output from the temperature measurement unit, and the first parameter, respectively. A first concentration calculation unit that calculates the second concentration, a second storage unit that stores a second parameter for calculating the gas concentration, and the first sensor unit and the second sensor when the second light emitting unit emits light. The second concentration calculation for calculating the second gas concentration from the first b sensor signal and the second b sensor signal output from the unit, the second temperature information output from the temperature measurement unit, and the second parameter, respectively. A third storage unit that records the temperature information, the first a sensor signal, the second a sensor signal, and the second gas concentration, a first trigger generation unit that outputs a first trigger signal, 1 trigger signal When entered, based on the third information stored in the storage unit, it calculates the first parameter, and the parameter calculation unit to be stored in the first storage unit, a gas sensor comprising a.

  ADVANTAGE OF THE INVENTION According to this invention, the gas sensor which made it possible to correct | amend the influence of deterioration of the light source in the measurement of gas concentration with high precision is realizable.

It is a block diagram for demonstrating Embodiment 1 of the gas sensor which concerns on this invention. It is a block diagram for demonstrating Embodiment 2 of the gas sensor which concerns on this invention. It is a figure which shows the example of the parameter memorize | stored in the 1st memory | storage part. (A), (b) is a figure which shows the calculation method of the correction parameter memorize | stored in a 3rd memory | storage part. It is a block diagram which shows the Example which is a specific structure of each embodiment.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as the present embodiment) will be described. The following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

<Overall configuration>
The gas sensor according to the present embodiment includes a gas cell into which a measurement target gas is introduced, a first main surface, and a second main surface facing the first main surface, and the first light emitting unit on the first main surface. And a first substrate on which the first sensor unit is provided, a first main surface, and a second main surface opposite to the first main surface, the second light emitting unit and the second main surface on the first main surface. A second substrate on which a sensor unit is provided; a first driving unit that drives the first light emitting unit; a second driving unit that drives the second light emitting unit; and the first driving unit and the second driving unit. A drive control unit that controls timing for driving the first light emitting unit and the second light emitting unit, a temperature measuring unit that measures the temperature of the first light emitting unit and / or the second light emitting unit, and outputs the temperature information; and a gas concentration A first storage unit that stores a first parameter for calculation and a first sensor unit and a second sensor unit when the first light emitting unit emits light, respectively. A first concentration calculation unit that calculates a first gas concentration from the signal S1A and the signal S2A that are output, first temperature information output from the temperature measurement unit, and a first parameter; and for calculating the gas concentration When the second storage unit for storing the second parameter and the second light emitting unit emit light, the signals S1B and S2B output from the first sensor unit and the second sensor unit, respectively, and the temperature measuring unit output A second concentration calculation unit that calculates a second gas concentration from the second temperature information and a second parameter; a third storage unit that records the temperature information, the signal S1A, the signal S2A, and the second gas concentration; A first trigger generating unit that outputs a first trigger signal, and when the first trigger signal is input, a first parameter is calculated based on information stored in the third storage unit and stored in the first storage unit A parameter calculation unit A gas sensor that.

<First substrate>
In the gas sensor according to the present embodiment, the first substrate has a first light emitting portion and a first sensor portion formed on the first main surface. The material for the first substrate is not particularly limited. For example, Si, GaAs, sapphire, InP, InAs, Ge, and the like can be given. However, the present invention is not limited to this, and it may be selected according to the wavelength band to be used. A GaAs substrate is particularly preferable from the viewpoint that a semi-insulating substrate can be used and the diameter can be increased. Further, from the viewpoint of improving measurement sensitivity, it is preferable that the material of the first substrate is a material having high transmittance for light output from the light emitting unit. In addition, from the viewpoint of highly accurately compensating for output fluctuations of the light emitting unit, the material of the first substrate is preferably a material that reflects part of the light output from the first light source on the second main surface.
<Second substrate>
The second substrate is made of the same material as the first substrate, and having the same structure may be preferable from the viewpoint of productivity and temperature correction.

<First drive unit>
The first drive unit has a function of driving the first light source. A specific example is a driver circuit using a MOS drive transistor. As a specific driving condition, a constant current driving circuit driven at a constant current may be used, or a constant voltage driving circuit driven at a constant voltage may be used. In addition, although a DC drive current may be used, there are cases where driving by pulse driving is more effective from the viewpoint of power consumption. In particular, when driving a light source made of a laminated film of narrow gap semiconductors, it may be more preferable to drive by a pulse drive in order to suppress radiation due to heat generated during the drive. The specific duty of the pulse drive is preferably 50% or less. In order to suppress heat generation and power consumption, the duty may be 25%, 10% or less, or 5% or less. In this case, as shown in FIG. 2 to be described later, the output signal of the first sensor unit may be amplified while using the synchronization signal of the drive circuit. A specific example of the amplification method using the synchronization signal is a Lockin-Amp method. By using the Lockin-Amp method, a high S / H ratio can be realized, and a highly accurate gas sensor can be realized.

<Second drive unit>
It is preferable that it is the same structure as a 1st drive part. When there is manufacturing variation (sensitivity variation between the first light source unit and the second light source unit, variation in light emission characteristics of the first sensor unit and the second sensor unit, variation in the light path installation position), the light emission intensity of the light sources on both sides should be equal. Alternatively, it may have a function of adjusting the drive current and the drive voltage so that the output signals of the sensor units are equal.

<Drive controller>
The drive control unit receives the measurement request command, the timing when the first drive unit and the second drive unit drive the first light emitting unit and the second light emitting unit, and the start timing of the first calculation unit and the second calculation unit To control.
When the measurement request command is received, the first calculation unit is activated, and an output signal is output to the first drive unit so that the first light source is driven. In addition, at another timing, the second calculation unit is activated, and an output signal is output to the second drive unit so that the second light source is driven. The timing at which the second drive unit operates may be designed when a desired measurement request command exceeds a predetermined desired number of times.

When the period (or number of times) when the first light source is driven is T1, and the period when the second light source is driven is T2, T2> T1, so that the second light source is not deteriorated and periodic calibration ( The conversion parameter can be updated), and the effect of the present invention can be exhibited. In general, T2> (5 × T1) is good, T2> (10 × T1) is better, and T2> (100 × T1) is preferable.
Here, it has been described that the second light source operates in a cycle N times the period (or the number of times) when the first light source is driven, but the present invention is not limited to this. For example, when the temperature changes greatly, the first light source drive may be switched to the second light source drive. In this case, information on a wide temperature range can be obtained, and in the case of a gas sensor having a wide temperature range specification, it may be preferable from the viewpoint of measurement accuracy.

<Temperature measurement unit>
The temperature measurement unit is means for measuring the temperatures of the first light source and the second light source. Specific examples include a thermistor or a thermocouple installed near the light source, and a thermometer using a semiconductor junction may be used. Since the temperature measurement unit must accurately measure the temperatures of the first light source and the second light source, it is desirable that the temperature measurement unit be installed symmetrically with respect to the first light source and the second light source. If it does so, it will become possible to measure the temperature of both light sources accurately with one element. Further, the temperature of the light source may be calculated based on the internal resistance of the light source or the forward voltage applied to the junction. This may be preferable because it requires less parts and can calculate the temperature of the core of the light source. Further, the temperature of the light source may be calculated based on the internal resistance of the first sensor unit or the second sensor unit. In this case, the number of parts can be reduced, and the internal resistance of the sensor unit is higher than that of the light source.

<First storage unit>
The first storage unit has a role of storing the latest conversion parameter (B _nm parameter described later). As a specific form, an EEPROM (Electrically Erasable Programmable Read-only-memory), which is a semiconductor memory, may be used.
<First concentration calculation unit>
The first calculation unit calculates the gas concentration based on the parameters stored in the first storage unit, the instantaneous output of the first sensor unit, the output of the second sensor unit, and the temperature information from the temperature measurement unit. Has function.
FIG. 3 is a diagram illustrating an example of parameters stored in the first storage unit.

<Specific example of calculation method>
The gas concentration can be calculated from equation (1).
C = A _n R ⁿ +... + A ₁ R + A ₀ (1)
An = B _{n, m} T ^m +... + B _{n, 1} T + B _{n, 0}
...
A ₁ = B _{1, m} T ^m +... + B _1,1 T + B _1,0
A ₀ = B _{0, m} T ^m +... + B _0,1 T + B _0,0 (2)

However, T is a temperature, An is a coefficient of temperature shown in Formula (2), B _nm is a conversion parameter stored in the first storage unit, and Rn is an output signal of each of the first sensor unit and the second sensor unit. It is a numerical value obtained from the ratio.
The sensor unit on the same substrate as the driven light source may be a reference sensor, and the sensor unit on the opposite substrate may be a main sensor. By taking this ratio, the temperature characteristics are relaxed and a highly accurate gas sensor can be realized. In this case, when the first light source is emitting light, R = (output of the second sensor unit / output of the first sensor unit) may be set. When the second light source is emitting light, R = (first 1 sensor unit output / second sensor unit output).

<Second storage unit>
The second storage unit has a role of storing initial correction parameters when the second drive unit is driven at the time of manufacture (in some cases, at the time of manufacture and shipment). Similar to the first memory, the second memory may be formed of an EEPROM.
<Second concentration calculation unit>
The second concentration calculation unit includes parameters stored in the second storage unit, outputs of the first sensor unit and the second sensor unit obtained when the second light source is driven, and temperature information obtained from the temperature measurement unit. Based on the above, it has a role to calculate the gas concentration. The calculation method is the same as that of the first concentration calculation unit and is omitted.

<Third storage unit>
The third storage unit outputs the output of the first sensor unit, the output of the second sensor unit (or the ratio in some cases), the true concentration value calculated by the second concentration calculation unit, and the temperature measurement unit. It has a role of recording temperature information (see FIGS. 4A and 4B).
4A and 4B are diagrams illustrating a method for calculating the correction parameter stored in the third storage unit.
These pieces of information are calculated and recorded at the same time, but since this process is performed periodically and automatically, it becomes three-dimensional data as shown in FIG. Here, when the temperature information is organized into parameters, the relationship shown in FIG. 4B is obtained.

<First trigger generator>
The first trigger generator has a role of outputting a trigger signal so that the parameter calculator operates. The timing may be an arbitrary timing or a timing of generating a trigger signal when the measurement request command exceeds a desired number of times. In this case, the first trigger generation unit may perform an operation such that a trigger is generated when the difference between the output of the first calculation unit and the second calculation unit exceeds a desired value. In this case, the deterioration of the second sensor unit is desirable because it is the most suppressed.

<Parameter calculation unit>
The parameter calculation unit has a role of calculating a parameter of b _nm using the information stored in the third storage unit (FIG. 4B) and writing to the first storage unit. By this operation, the density calculation parameter is updated, and correct density conversion can always be performed regardless of the deterioration of the first light source.

<Second trigger generator>
The second trigger generator has a role of generating a trigger signal for activating the parameter calculator. Similar to the first trigger generation unit, the second trigger generation unit may have either timing of generating a trigger signal when the measurement request command exceeds a desired number of times. However, the second trigger generation unit may be set to generate a trigger signal less frequently than the first trigger generation unit.

<First amplification unit>
The first amplifying unit amplifies the output signal of the first signal unit using the synchronization signal from the first light source unit and the output signal of the first sensor unit. The first amplification unit may operate in the same way as Lockin-Amp. In this case, only the component having the same frequency as that of the synchronization signal can be extracted by mixing the synchronization signal from the first drive unit and the output signal of the first sensor unit and passing through the low-pass filter (LPF) circuit. . For example, when the drive timing of the first drive unit is 1 kHz, only signal components at a frequency of 1 kHz can be extracted.
Further, only when the first light source is driven, the outputs of the first sensor unit may be integrated, and the integration result may be output when a desired integration period or number of times is reached.
<Second amplification unit>
Since the second amplifying unit has the same structure and operation as the first amplifying unit, description thereof is omitted.
Next, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
FIG. 1 is a configuration diagram for explaining Embodiment 1 of a gas sensor according to the present invention. The first embodiment can be applied to the measurement of CO ₂ gas concentration.
The gas sensor 100 according to the first embodiment includes a gas cell 11 into which a measurement target gas is introduced (an inlet is not shown and omitted), a first main surface 21a, and a second main surface facing the first main surface 21a. 21b, the first substrate 21 provided with the first light emitting unit 41 and the first sensor unit 51 on the first main surface 21a, the first main surface 22a and the first main surface 22a. A second substrate 22 having a second main surface 22b and having a second light emitting unit 42 and a second sensor unit 52 provided on the first main surface 22a.

In addition, a first driving unit 31 that drives the first light emitting unit (first light source) 41 and a second driving unit 32 that drives the second light emitting unit (second light source) 42 are provided.
In addition, the first drive unit 31 and the second drive unit 32 control the timing of driving the first light emitting unit 41 and the second light emitting unit 42, and the first light emitting unit 41 and / or the second light emission. A temperature measuring unit 12 that measures the temperature of the unit 42 and outputs the temperature information.
Further, the first storage unit 71 that stores the first parameter for calculating the gas concentration and the first sensor unit 51 and the second sensor unit 52 output when the first light emitting unit 41 emits light, respectively. A first concentration calculation unit 61 that calculates a first gas concentration from the 1a sensor signal S1A, the second a sensor signal S2A, the first temperature information output from the temperature measurement unit 12, and the first parameter is provided. .

The second storage unit 72 that stores the second parameter for calculating the gas concentration and the first sensor unit 51 and the second sensor unit 52 output when the second light emitting unit 42 emits light, respectively. A second concentration calculation unit 62 that calculates a second gas concentration from the 1b sensor signal S1B, the second b sensor signal S2B, the second temperature information output from the temperature measurement unit 12, and the second parameter is provided. .
Also, a third storage unit 73 that records temperature information, the first a sensor signal S1A, the second a sensor signal S2A, and the second gas concentration, a first trigger generation unit 81 that outputs a first trigger signal, and a first trigger A parameter calculation unit 14 is provided that calculates a first parameter based on information stored in the third storage unit 73 and stores the first parameter in the first storage unit 71 when a signal is input.

Further, the second light emitting unit 42 is driven at a certain time interval, and the first parameter is periodically calibrated. The first trigger generator 81 outputs a first trigger signal when the difference between the first gas concentration and the second gas concentration is larger than a predetermined value.
The first trigger generation unit 81 outputs a first trigger signal when the number of gas concentration calculations by the first concentration calculation unit 61 exceeds a predetermined number.
Further, the apparatus further includes a second trigger generation unit 82 that outputs a second trigger at a predetermined time interval, and the parameter calculation unit 14 stores the second trigger signal in the third storage unit 73 when the second trigger signal is input. Based on the obtained information, the first parameter is calculated and stored in the first storage unit 71.

The third storage unit 73 further stores a sensor signal ratio S2A / S1A that is a ratio of the 2a sensor signal S2A and the 1a sensor signal S1A. In some cases, the division result of S2A / S1A may be stored in the third storage unit 73 instead of S1A and S2A. In this case, a storage device having a small capacity may be used, which may be preferable from the viewpoint of simplification of the system.
Further, the first light emitting unit 41 and the second light emitting unit 42 have the same structure and the same light emission characteristics, and the first sensor unit 51 and the second sensor part 52 have the same structure and the same sensitivity characteristics.

[Embodiment 2]
FIG. 2 is a configuration diagram for explaining Embodiment 2 of the gas sensor according to the present invention. In addition, the same code | symbol is attached | subjected to the component which has the same function as FIG.
The difference in configuration from the first embodiment described above is that a first amplifying unit 91 for amplifying the sensor signals S1A and S1B from the first sensor unit 51 based on the synchronization signal from the first driving unit 31 is provided, and 2 is that a second amplifying unit 92 for amplifying the sensor signals S2A and S2B from the second sensor unit 52 based on the synchronization signal from the driving unit 32 is provided.
The first substrate 21 and the second substrate 22 are installed next to each other, the first light source 41 and the first sensor unit 51 are provided on the first substrate 21, and the second light source 42 and the second sensor are provided on the second substrate 22. A part 52 is provided.
The 1st sensor part 51 and the 2nd sensor part 52, the 1st light source 41, and the 2nd light source 42 may have the same structure.

An n-type AlInSb layer having a thickness of 1 μm on a GaAs substrate, an i-type AlInSb layer having a thickness of 2 μm thereon, an AlInSb burr layer having a thickness of 0.02 μm thereon, and a p-type having a thickness of 0.5 μm thereon. An AlInSb layer was provided. This structure was formed using the MBE (Molecular Beam Epitaxy) method. Sn was used for n-type doping and Zn was used for p-type doping.
Then, after forming a multi-stage light emitting element and a multi-stage light receiving part using a second etching process (first etching from the top layer to the middle of the n layer and second etching to the GaAs substrate), Passivation with an insulating film (Si ₃ N ₄ ) was performed, holes for contact portions between the n layer and the p layer were processed, and finally a wiring layer using Au was formed.

FIG. 5 is a configuration diagram illustrating an example which is a specific structure of each embodiment.
The signal processing unit 104 is a signal processing IC created by using Si LSI technology, and includes each block (other than the first substrate 21, the second substrate 22, and the gas cell 11) shown in FIGS. Yes.
Further, the connection between the first light source 41, the second light source 42, the first sensor unit 51, the second sensor unit 52 and the signal processing IC is performed using a wire bonding technique (not shown), and the signal processing IC Connection to an external circuit (not shown) is made through a lead frame terminal.

Further, in order to improve measurement accuracy and gas separation property, an optical filter 101 having a center wavelength of about 4.3 μm is provided on the first substrate 21 and the second substrate 22 by using an adhesive 102.
Further, sealing was performed using the sealing portion 103 so as to be integrated with the signal processing IC while exposing the back surface of the first substrate 21 and the back surface (second main surface) of the second substrate 22.
Further, the optical path 106 is realized by a gas cell having a concave mirror shape.
The driving conditions were a voltage of 2 V, 100 mA, and a duty of 5%, and an integration circuit using the first amplification unit 91 and the second amplification unit 92 using the synchronization signals from the first driving unit 31 and the second driving unit 32 was used. .

The first drive unit 31 always drives the first light source 41, and the second drive unit 32 is a drive in the signal processing unit 104 so as to drive the second light source 42 periodically (for example, once / day). The control unit 13 is controlled.
In addition, the conversion parameter was set to be recalculated when the instantaneous CO ₂ concentration exceeded 20 ppm compared to the true CO ₂ concentration.
As a result, the temperature, true CO ₂ concentration, output of the first sensor unit 51, and output information of the second sensor unit 52 are obtained at random, and the effects of deterioration are completely guaranteed while periodically updating the conversion parameters. We were able to.

  As mentioned above, although embodiment of this invention was described, the technical scope of this invention is not limited to the technical scope as described in embodiment mentioned above. It is possible to add various changes or improvements to the above-described embodiments, and it is possible to add such changes or improvements to the technical scope of the present invention. it is obvious.

DESCRIPTION OF SYMBOLS 11 Gas cell 12 Temperature measurement part 13 Drive control part 14 Parameter calculation part 21 1st board | substrate 22 2nd board | substrate 21a, 22a 1st main surface 21b, 22b 2nd main surface 31 1st drive part 32 2nd drive part 41 1st light emission Unit 42 second light emitting unit 51 first sensor unit 52 second sensor unit 61 first concentration calculation unit 62 second concentration calculation unit 71 first storage unit 72 second storage unit 73 third storage unit 81 first trigger generation unit 82 Second trigger generation unit 91 First amplification unit 92 Second amplification unit 100 Gas sensor

Claims (7)

A gas cell into which a gas to be measured is introduced;
A first substrate having a first main surface and a second main surface opposite to the first main surface, wherein the first light emitting unit and the first sensor unit are provided on the first main surface;
A second substrate having a first main surface and a second main surface opposite to the first main surface, wherein a second light emitting unit and a second sensor unit are provided on the first main surface;
A first driving unit for driving the first light emitting unit;
A second driving unit for driving the second light emitting unit;
A drive control unit for controlling the timing at which the first driving unit and the second driving unit drive the first light emitting unit and the second light emitting unit;
A temperature measuring unit that measures the temperature of the first light emitting unit and / or the second light emitting unit and outputs the temperature information;
A first storage for storing a first parameter for calculating a gas concentration;
When the first light emitting unit emits light, a first a sensor signal and a second a sensor signal output from the first sensor unit and the second sensor unit, respectively, and first temperature information output from the temperature measuring unit And a first concentration calculation unit for calculating a first gas concentration from the first parameter,
A second storage unit for storing a second parameter for calculating a gas concentration;
When the second light emitting unit emits light, the first b sensor signal and the second b sensor signal output from the first sensor unit and the second sensor unit, respectively, and the second temperature information output from the temperature measuring unit. And a second concentration calculation unit for calculating a second gas concentration from the second parameter,
A third storage unit that records the temperature information, the 1a sensor signal, the 2a sensor signal, and the second gas concentration;
A first trigger generator for outputting a first trigger signal;
A parameter calculation unit that calculates the first parameter based on information stored in the third storage unit when the first trigger signal is input, and stores the first parameter in the first storage unit;
A gas sensor comprising:   2. The gas sensor according to claim 1, wherein the second light emitting unit is driven at a certain time interval to periodically calibrate the first parameter.   The gas sensor according to claim 1, wherein the first trigger generation unit outputs the first trigger signal when a difference between the first gas concentration and the second gas concentration is larger than a predetermined value.   2. The gas sensor according to claim 1, wherein the first trigger generation unit outputs the first trigger signal when the number of times the gas concentration is calculated by the first concentration calculation unit exceeds a predetermined number. A second trigger generator for outputting the second trigger at a predetermined time interval;
The parameter calculation unit calculates the first parameter based on the information stored in the third storage unit when the second trigger signal is input, and stores the first parameter in the first storage unit. The gas sensor according to any one of claims 1 to 4.   The gas sensor according to any one of claims 1 to 5, wherein the third storage unit further stores a sensor signal ratio that is a ratio of the second a sensor signal and the first a sensor signal. The first light emitting unit and the second light emitting unit have the same structure and the same light emission characteristics,
The gas sensor according to any one of claims 1 to 6, wherein the first sensor unit and the second sensor unit have the same structure and the same sensitivity characteristics.

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