JP6062704B2 - Gas concentration detector - Google Patents

Description

  The present invention relates to a gas concentration detection device that detects the concentration of a measurement target gas contained in a sample gas.

  Conventionally, as a gas concentration detection device that detects the concentration of a measurement target gas contained in a sample gas, based on a signal (measurement data) output from a light receiving element (light reception sensor) according to the concentration of the measurement target gas, Some detect the concentration of the gas to be measured.

  That is, since the output signal of the light receiving element changes according to the concentration of the measurement target gas, the concentration of the measurement target gas can be detected by using this output signal (measurement data).

JP 2004-138499 A

However, in the above conventional gas concentration detection apparatus, the output signal of the light receiving element may fluctuate due to the influence of noise or the like, and there is a possibility that the detection accuracy of the gas concentration is lowered.
For example, when the output signal of the light receiving element fluctuates due to noise or the like, the gas concentration detection result also fluctuates, and the gas concentration detection accuracy decreases.

  Therefore, the present invention has been made in view of such problems, and even when the output signal of the light receiving element fluctuates due to the influence of noise or the like, the gas concentration detection capable of suppressing a decrease in gas concentration detection accuracy. An object is to provide an apparatus.

  The invention according to claim 1, which has been made to achieve such an object, includes a measurement cell into which a sample gas is introduced and a measurement cell in a gas concentration detection device that detects the concentration of a measurement target gas contained in the sample gas. A light source for irradiating the sample gas introduced to the sample with infrared light, a first light receiving unit for detecting infrared light having different wavelength regions and passing through the sample gas, and a second light receiving unit. And a detection means for detecting the concentration of the measurement target gas contained in the sample gas based on the measurement data obtained by the first light receiving means and the measurement data obtained by the second light receiving means. The detecting means includes a moving average calculating means for calculating respective moving average values of the measurement data by the first light receiving means and the measurement data by the second light receiving means, and the measurement data by the first light receiving means. The first data maximum value which is the maximum value during the irradiation period of infrared light from the light source among the moving average value, and the maximum value during the irradiation period of infrared light from the light source among the moving average value of the measurement data by the second light receiving means. A maximum value calculating means for calculating a certain second data maximum value, and a first data minimum value which is a minimum value in a non-irradiation period of infrared light by the light source among moving average values of measurement data by the first light receiving means. And a minimum value calculating means for calculating a second data minimum value, which is a minimum value in a non-irradiation period of infrared light from the light source, among moving average values of measurement data by the second light receiving means, and a first data maximum A difference value for calculating a first data difference value that is a difference value between the value and the first data minimum value, and a second data difference value that is a difference value between the second data maximum value and the second data minimum value, respectively. Calculation means Difference average calculation means for calculating a first data difference average value that is a moving average value of the first data difference value and a second data difference average value that is a moving average value of the second data difference value; and first data A gas concentration detection device comprising: a concentration calculation means for calculating the concentration of the measurement target gas contained in the sample gas based on the difference average value and the second data difference average value.

  In this gas concentration detection apparatus, in calculating the gas concentration, the measurement data by the first light receiving means and the measurement data by the second light receiving means are not used as they are, but the measurement data by the first light receiving means and the second light receiving means are used. It is characterized in that the gas concentration is calculated using the moving average value of the measurement data.

  In other words, even if the measurement data by the first light receiving means and the measurement data by the second light receiving means fluctuate greatly instantaneously due to the influence of noise (disturbance factor), the fluctuation range of the moving average value is measured. Since it is smaller than the instantaneous fluctuation range of data, the influence of noise (disturbance factor) and the like can be suppressed when calculating the gas concentration.

  Regarding the calculation of the moving average value, not only the measurement data by the first light receiving unit and the measurement data by the second light receiving unit, but also the first data difference value and the second data difference value (moving average value (first data)). The difference average value and the second data difference average value) are respectively calculated.

  In this way, by calculating the moving average value over a plurality of stages with respect to the measurement data by the first light receiving means and the measurement data by the second light receiving means, the influence of noise (disturbance factor) and the like can be further suppressed, and the gas concentration A decrease in detection accuracy can be suppressed.

Therefore, according to the present invention, even when the output signal of the light receiving element fluctuates due to the influence of noise or the like, it is possible to suppress a decrease in gas concentration detection accuracy.
Note that the irradiation state and non-irradiation state of infrared light by the light source may be switched and controlled irregularly, or may be switched at regular intervals. The infrared light irradiation period and the non-irradiation period may have different lengths.

  And when performing irradiation control which makes the irradiation state and non-irradiation state of infrared light one cycle repeatedly, the first data maximum value, the second data maximum value, the first data minimum value, for each cycle, The second data minimum value may be calculated, and the moving average values (first data difference average value and second data difference average value) may be calculated using the calculated values over a plurality of cycles. That is, the moving average value (first data difference average value and second data difference average value) is calculated using the first data difference value and the second data difference value calculated for each cycle, and the concentration of the measurement target gas Is calculated.

  Thus, by calculating the moving average value using each calculated value over a plurality of cycles, even if instantaneous noise (disturbance factor) or the like occurs, a large change in the moving average value can be suppressed. The influence of disturbance factors) can be further suppressed, and a decrease in gas concentration detection accuracy can be suppressed.

  Next, the gas concentration detection device described above includes an integrated flow rate determination unit that determines whether or not the integrated flow rate value of the sample gas introduced into the measurement cell exceeds a predetermined flow rate determination value. The calculation means is included in the sample gas based on the latest first data difference average value and second data difference average value at the time when the integrated flow value determination unit determines that the integrated flow value exceeds the flow determination value. It is possible to adopt a configuration in which the concentration of the measurement target gas is calculated.

  Thus, by determining whether or not the integrated flow value of the sample gas introduced into the measurement cell exceeds the flow rate determination value, it can be determined whether or not the sample gas has been sufficiently introduced into the measurement cell, It is possible to avoid calculating the gas concentration in a situation where the introduction of the sample gas into the measurement cell is insufficient.

  That is, the concentration of the measurement target gas is calculated based on the latest first data difference average value and second data difference average value when the integrated flow value of the sample gas introduced into the measurement cell exceeds the flow rate determination value. Thus, the concentration of the measurement target gas can be calculated in a state where the sample gas is sufficiently introduced into the measurement cell.

Therefore, according to the present invention, it is difficult to generate a detection error due to insufficient introduction of the sample gas into the measurement cell, and it is possible to suppress a decrease in gas concentration detection accuracy.
Next, in the gas concentration detection device described above, whether or not the temperatures of the heaters for heating the first light receiving means and the second light receiving means and the first light receiving means and the second light receiving means are within a predetermined normal range. Temperature detecting means for determining whether the temperature of the first light receiving means and the second light receiving means is within a normal range by the temperature determining means. It is possible to adopt a configuration in which density calculation is executed.

  As described above, by providing the heater and the temperature determining unit, it is possible to execute the concentration calculation of the measurement target gas by the detecting unit after confirming that the first light receiving unit and the second light receiving unit are in the normal state. .

  For example, the temperature range in which the first light receiving means and the second light receiving means do not condense is determined in advance as a normal range, and the concentration of the measurement target gas when the temperatures of the first light receiving means and the second light receiving means are within this normal range. By calculating the above, it is possible to detect the concentration of the gas to be measured while suppressing adverse effects due to condensation of the first light receiving means and the second light receiving means. That is, it is possible to suppress fluctuations in the amount of light received by the first light receiving unit and the second light receiving unit due to the influence of condensation, and it is possible to suppress a decrease in the detection accuracy of the concentration of the measurement target gas.

  Therefore, according to the present invention, since it is possible to perform the concentration calculation of the measurement target gas after confirming that the temperatures of the first light receiving means and the second light receiving means are in the normal range, it is possible to suppress a decrease in gas concentration detection accuracy. be able to.

  When the temperature determination unit determines that the temperatures of the first light receiving unit and the second light receiving unit are not in the normal range, the detection unit does not calculate the concentration of the measurement target gas and does not calculate the first light receiving unit. It is possible to adopt a configuration of waiting until each temperature of the means and the second light receiving means is in a normal range.

It is a schematic block diagram of the gas concentration detection apparatus which detects the density | concentration of the alcohol contained in a person's expiration. It is BB sectional drawing in the gas concentration detection apparatus of FIG. It is a flowchart showing the processing content of the gas concentration detection processing. It is a timing chart showing an example of each state of the ON / OFF state of a light source, the sensor output (output data) of a 1st infrared rays detection element, and a moving average value. It is a measurement result of the difference average value (Example) of the output data of an infrared detection element, and the difference value (comparative example) calculated from the output data of an infrared detection element without using a moving average.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
In the following embodiments, a gas concentration detection apparatus to which the present invention is applied will be described as an example.

[1. First Embodiment]
[1-1. overall structure]
The overall configuration of the gas concentration detection device 1 of the present embodiment will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a gas concentration detection device 1 that detects the concentration of alcohol contained in a person's breath.
The gas concentration detection device 1 of this embodiment is a non-dispersive infrared absorption (NDIR) gas concentration detection device.

The gas concentration detection apparatus 1 mainly includes an infrared gas sensor 111 into which human breath is blown, and a control unit 151 that executes a gas concentration detection process.
FIG. 2 is a cross-sectional view of the infrared gas sensor 111 taken along the line BB.

  The infrared gas sensor 111 includes a cylindrical container 113 whose front end side (left side in FIG. 1) is closed, a heater 114 disposed so as to surround the container 113, and a white light source 115 disposed on the front end side of the container 113. , And a base 117 disposed on the rear end side of the container 113.

  The container 113 is a container made of a non-translucent material (for example, an aluminum alloy) filled with a sample gas containing a specific component to be measured, and a plurality of passages for introducing and discharging the sample gas are provided on the side wall thereof. The pores 141 and 143 are formed.

  A gas introduction pipe 144 is connected to the vent hole 141, and a gas exhaust pipe 145 is connected to the vent hole 143. A flow rate sensor 146 is provided in the gas introduction pipe 144. The flow sensor 146 outputs a signal corresponding to the flow rate of gas flowing through the gas introduction pipe 144 to the control unit 151.

  The heater 114 is a silicon rubber heater and is disposed so as to surround the container 113. The heater 114 heats the container 113 at a specific control target temperature set to 40 [° C.] or higher (in this embodiment, set to 50 [° C.]), so that the inner surface of the container 113 is condensed. Suppress.

  At this time, the amount of heat from the heater 114 is also conducted to the base 117 via the container 113. This suppresses dew condensation on the surfaces of the constituent elements of the base 117 (the first wavelength selection filter 131, the second wavelength selection filter 133, the first infrared detection element 135, and the second infrared detection element 137), which will be described later.

  The base 117 includes a non-transparent cap 119 made of, for example, stainless steel and a TO package 121. The cap 119 includes a disk part 123 and a cylindrical part 125.

  The disk portion 123 is provided with openings 127 and 129 at two locations, and a first wavelength selection filter 131 and a second wavelength selection filter 133 are disposed in each of the openings 127 and 129. The first wavelength selection filter 131 and the second wavelength selection filter 133 are disposed so as to cover the openings 127 and 129, respectively, and each transmits only infrared rays in a specific band.

  The first wavelength selection filter 131 and the second wavelength selection filter 133 are not particularly limited in material, and are formed on the surface of a substrate made of an infrared transmitting material such as sapphire, quartz glass, silicon, germanium, zinc selenide, A laminate of a plurality of transparent films can be employed.

  Further, on the inner surface of the TO package 121, a first infrared detection element 135 and a second infrared detection element 137 are arranged on the rear end side corresponding to the first wavelength selection filter 131 and the second wavelength selection filter 133, respectively. Has been.

The first infrared detection element 135 and the second infrared detection element 137 each output a voltage corresponding to the intensity of the incident infrared rays.
The types of the first infrared detection element 135 and the second infrared detection element 137 are not particularly limited, and generally used infrared sensors such as a pyroelectric sensor, a thermopile sensor, and a photodiode can be used.

  In addition, when the surface of any one of the first wavelength selection filter 131, the second wavelength selection filter 133, the first infrared detection element 135, and the second infrared detection element 137 is condensed, the infrared rays are weakened by the condensation. The intensity of infrared rays incident on the infrared detection element 135 or the second infrared detection element 137 is reduced. In order to suppress the influence of such condensation, heating by the heater 114 is effective.

The white light source 115 outputs light including at least infrared rays, and there is no particular limitation on the type thereof, and a light bulb or a heating resistor can be used.
In the infrared gas sensor 111 of the present embodiment, the white light source 115, the first wavelength selection filter 131, and the first infrared detection element 135 are arranged on the same straight line L1, and similarly, the white light source 115 and the second light source 115 are connected to each other. The wavelength selection filter 133 and the second infrared detection element 137 are arranged on another same straight line L2.

  That is, the infrared rays irradiated from the white light source 115 are transmitted through the sample gas introduced into the container 113, and the first infrared detection elements are respectively passed through the first wavelength selection filter 131 and the second wavelength selection filter 133. 135 and the second infrared detecting element 137 are arranged to enter.

  The first wavelength selection filter 131 has a band (pass band) of light (that is, infrared light) that can pass therethrough that matches an absorption band of a specific component (for example, ethyl alcohol (EtOH)) whose concentration is to be measured. It consists of As for the light incident on the first wavelength selection filter 131, only light having a wavelength matching this pass band is transmitted, and light having other wavelengths cannot be transmitted.

  That is, the infrared light having a wavelength matching the pass band is absorbed by the specific component, but the material of the first wavelength selection filter 131 is selected so that only the absorbed infrared light can be transmitted.

  Therefore, the intensity of the light transmitted through the first wavelength selection filter 131, that is, the output of the first infrared detection element 135 depends on the concentration of the gas species (specific component) present in the measurement space 147 of the container 113. That is, the concentration of the specific component existing in the measurement space 147 can be measured based on the output of the first infrared detection element 135 (specifically, the sensor output obtained by amplifying the element output).

  The second wavelength selection filter 133 has a band (pass band) of light (that is, infrared rays) that can pass therethrough that is different from that of the first wavelength selection filter 131, and any of the second wavelength selection filter 133 that is assumed to exist in the sample gas. It is configured with a band that does not correspond to a gas absorption band.

For this reason, it becomes possible to compensate for noise (disturbance factor) with respect to the output of the first infrared detection element 135 by using the second infrared detection element 137 as a reference element.
The control unit 151 calculates the gas concentration of a specific component (for example, ethyl alcohol (EtOH)) that is a concentration measurement target based on the output of the first infrared detection element 135, the output of the second infrared detection element 137, and the like.

  The control unit 151 is configured by a so-called microcomputer, and although not shown in detail, has a known configuration, a microprocessor that performs calculation, a RAM that temporarily stores programs and data, a ROM that stores programs and data, An A / D conversion circuit that converts an analog signal into a digital signal is included. The A / D conversion circuit converts an analog signal input from the AD input terminal ADC into a digital signal that can be used by a microprocessor or the like.

[1-2. Gas concentration detection]
Next, the gas concentration detection process executed by the control unit 151 will be described. FIG. 3 is a flowchart showing the processing content of the gas concentration detection processing.

The gas concentration detection process starts when the gas concentration detection device 1 is activated.
When the gas concentration detection process is started, first, in S110 (S represents a step, the same applies hereinafter), an initial setting process including initialization of the RAM operation and the like is performed.

  In the initial setting process in S110, a process for setting various parameter values and various flag states used in the gas concentration detection process to initial values is performed. For example, the cycle counter variable n is set to an initial value (n = 1), and the light source determination flag F is set to a reset state (F = 0). Also, an initial value is set as the maximum ON value used for the process in S180, and an initial value is set as the minimum OFF value used in the process in S210. At this time, the initial value of the ON maximum value is set to the minimum value in the numerical range that the ON maximum value can take, and the initial value of the OFF minimum value is set to the maximum value in the numerical range that the OFF minimum value can take. Set.

  Next, in S120, the heater 114 is started and the process which controls the heater 114 so that it may become predetermined control target temperature is performed. In the present embodiment, the control target temperature is set to 50 [° C.].

  In the next S130, it is determined whether or not the temperature of the first infrared detecting element 135 and the temperature of the second infrared detecting element 137 are both in the normal range. If an affirmative determination is made, the process proceeds to S140. Wait by repeatedly executing steps.

  In the present embodiment, the normal range in S130 is a temperature range in which the surfaces of the first wavelength selection filter 131, the second wavelength selection filter 133, the first infrared detection element 135, and the second infrared detection element 137 are not condensed. Is set. Specifically, “a temperature range of 45 ° C. or more” is set as the normal range in S130, and the temperature of the first infrared detection element 135 and the temperature of the second infrared detection element 137 are increased by the heating of the heater 114. If both are 45 [° C.] or higher, an affirmative determination is made in S130.

  Although not shown in FIG. 1, a temperature sensor is provided in the vicinity of the first infrared detecting element 135 and the second infrared detecting element 137, and the first sensor is based on the temperature detection signal from the temperature sensor. The temperature of the first infrared detecting element 135 and the temperature of the second infrared detecting element 137 are detected.

  When an affirmative determination is made in S130 and the process proceeds to S140, ON / OFF control of the white light source 115 is started in S140. In this ON / OFF control, the white light source 115 is controlled to be in an ON state (lighted state) for 0.25 [sec], and then is controlled to be in an OFF state (light-off state) for 0.25 [sec]. Again, control is performed to the ON state (lighting state). That is, in this ON / OFF control, the control in which the ON state (lighting state) and the OFF state (light-off state) are one cycle is repeatedly executed every 0.5 [sec].

In the next S150, the process of acquiring and storing the output data of the first infrared detecting element 135 and the output data of the second infrared detecting element 137 is started.
The sampling period at this time is 1 [msec], and each output data is acquired every 1 [msec]. The sensor output data acquisition process started in S150 is subsequently executed as a background process, and is continuously executed until the gas concentration detection process is completed.

  In the next S160, the moving average values of the output data of the first infrared detection element 135 and the output data of the second infrared detection element 137 are calculated using the data saved in the sensor output data acquisition process (S150). Start processing.

  In S160, for the output data of the first infrared detection element 135 and the output data of the second infrared detection element 137, the latest 150 pieces of data stored in the sensor output data acquisition process (S150) are obtained. A moving average value of data is calculated by calculating an average value as a target. Further, the moving average value calculation process started in S160 is subsequently executed as a background process, and is continuously executed until the gas concentration detection process is completed.

In S170, it is determined whether or not the white light source 115 is in an ON state. If an affirmative determination is made, the process proceeds to S180, and if a negative determination is made, the process proceeds to S190.
When an affirmative determination is made in S170 and the process proceeds to S180, in S180, the maximum value of the moving average value calculated in the moving average value calculation process (S160) is determined by comparison, and the power is turned on based on the determination result. Is stored (hereinafter also referred to as the ON maximum value).

  Specifically, the latest moving average value is compared with the ON maximum value stored when the previous process is executed, and the larger value is stored as the current ON maximum value. In other words, when the latest moving average value is large, the latest moving average value is stored as the current ON maximum value, and when the ON maximum value stored during the previous processing execution is large, it is stored during the previous processing execution. This ON maximum value is stored as the current ON maximum value. When S180 is executed for the first time, the initial value of the ON maximum value set in S110 is compared with the latest moving average value. As the initial value, the minimum value in the numerical range that the ON maximum value can take is set. Therefore, the latest moving average value is stored as the ON maximum value.

  At this time, in S180, the ON maximum value V1max related to the output data of the first infrared detecting element 135 and the ON maximum value V2max related to the output data of the second infrared detecting element 137 are stored.

  If a negative determination is made in S170 and the process proceeds to S190, it is determined in S190 whether or not the light source determination flag F is in a reset state (F = 0). If an affirmative determination is made, the process proceeds to S200, and if a negative determination is made, the process proceeds to S210. To do.

When an affirmative determination is made in S190 and the process proceeds to S200, the light source determination flag F is set to the set state (F = 1) in S200.
When the process of S200 is completed or a negative determination is made in S190 and the process proceeds to S210, in S210, the minimum value of the moving average value calculated in the moving average value calculation process (S160) is determined by a comparison operation. Based on the determination result, a process of saving a minimum value when the power is turned off (hereinafter also referred to as an OFF minimum value) is performed.

  Specifically, the latest moving average value is compared with the OFF minimum value stored when the previous process is executed, and the smaller value is stored as the current OFF minimum value. In other words, when the latest moving average value is small, the latest moving average value is stored as the current OFF minimum value, and when the OFF minimum value stored at the previous processing execution time is small, it is stored at the previous processing execution time. The OFF minimum value is stored as the current OFF minimum value. When S210 is executed for the first time, the initial value of the OFF minimum value set in S110 is compared with the latest moving average value, and the maximum value of the numerical range that the OFF minimum value can take is set as the initial value. Therefore, the latest moving average value is stored as the OFF minimum value.

  At this time, in S210, the OFF minimum value V1min related to the output data of the first infrared detection element 135 and the OFF minimum value V2min related to the output data of the second infrared detection element 137 are stored.

  When the process of S180 or S210 is completed and the process proceeds to S220, it is determined in S220 whether the white light source 115 is in the ON state and the light source determination flag F is in the set state (F = 1). If it determines, it will transfer to S230, and if it determines negative, it will transfer to S170. Note that S220 is a step for determining whether or not one cycle of ON / OFF control of the white light source 115 is completed, and a negative determination is made at a stage before one cycle is completed, and the processing from S170 to S220 is performed. When one cycle is completed, an affirmative determination is made and the process proceeds to S230.

When an affirmative determination is made in S220 and the process proceeds to S230, in S230, the light source determination flag F is set to a reset state (F = 0).
In subsequent S240, a difference value between the latest ON maximum value stored in S180 and the latest OFF minimum value stored in S210 is calculated. At this time, in S240, the difference value ΔV1 (n) (= ON maximum value V1max−OFF minimum value V1min) related to the output data of the first infrared detection element 135 and the difference value ΔV2 (related to the output data of the second infrared detection element 137). n) Calculation is performed for each of (= ON maximum value V2max−OFF minimum value V2min). Each time S240 is executed, the difference value ΔV1 (n) and the difference value ΔV2 (n) corresponding to the cycle counter variable n are stored.

In subsequent S250, a process of adding 1 to the cycle counter variable n (n = n + 1) is executed.
In the next S260, a process of resetting the ON maximum value and the OFF minimum value is performed. Specifically, the same initial value as that in S110 is set for each of the ON maximum value and the OFF minimum value. Thus, each time the one cycle of the ON / OFF control of the white light source 115 is completed, the ON maximum value and the OFF minimum value are reset.

In subsequent S270, it is determined whether or not the cycle counter variable n is 6 or more (n ≧ 6). If an affirmative determination is made, the process proceeds to S280, and if a negative determination is made, the process proceeds to S170.
Note that S270 is a step of determining whether at least five or more difference values ΔV1 (n) and ΔV2 (n) calculated in S240 are stored. The determination is repeated, and the processes from S170 to S270 are repeated. If five or more are stored, an affirmative determination is made and the process proceeds to S280.

  When an affirmative determination is made in S270 and the process proceeds to S280, in S280, the moving average value of the difference values calculated in S240 (hereinafter, also referred to as difference average value) is calculated and stored. In S280, the average value of the latest five difference values calculated in S240 is calculated and stored as the difference average value.

  At this time, in S280, the difference average value ΔV1ave (n−5) (= (ΔV1 (n−5) + ΔV1 (n−4) + ΔV1 (n−3) + ΔV1 (n−)) regarding the output data of the first infrared detection element 135 is obtained. 2) + ΔV1 (n-1)) / 5) and the difference average value ΔV2ave (n-5) (= (ΔV2 (n-5) + ΔV2 (n-4) + ΔV2 ( n-3) + ΔV2 (n-2) + ΔV2 (n-1)) / 5) are calculated and stored. Every time S280 is executed, the difference average value ΔV1ave (n-5) and the difference average value ΔV2ave (n-5) are calculated and stored based on the cycle counter variable n.

  In subsequent S290, it is determined whether or not introduction of exhaled air (sample gas) into the measurement space 147 of the container 113 has been started. If an affirmative determination is made, the process proceeds to S300, and if a negative determination is made, the process proceeds to S170 again. In this embodiment, based on the signal output from the flow sensor 146, it is determined whether or not introduction of exhaled air (sample gas) has started.

  That is, S290 is a step of determining whether or not the introduction of exhalation (sample gas) into the measurement space 147 of the container 113 has been started. A negative determination is made before the introduction of exhalation is started and S170 to S290 are performed. The process is repeated, and when introduction of exhalation is started, an affirmative determination is made and the process proceeds to S300.

  When an affirmative determination is made in S290 and the process proceeds to S300, in S300, whether or not the integrated flow rate value of the exhaled air (sample gas) introduced into the container 113 through the gas introduction pipe 144 is greater than a predetermined flow rate determination value TH1. If the determination is affirmative, the process proceeds to S300. If the determination is negative, the process proceeds to S170.

  S300 is a step of determining whether or not an amount of exhaled air (sample gas) necessary for gas detection has been introduced into the container 113, and when it is less than the required amount (when the integrated flow value is equal to or less than the flow determination value TH1). Is negatively determined, and the processing from S170 to S300 is repeated. When the required amount is reached (when the flow rate integrated value is larger than the flow rate determination value TH1), the determination is affirmative and the process proceeds to S310.

In the present embodiment, a value corresponding to exhalation 1.0 [L] is set as the flow rate determination value TH1.
When an affirmative determination is made in S300 and the process proceeds to S310, in S310, expiration is performed using the latest difference average values (difference average value ΔV1ave (n-5) and difference average value ΔV2ave (n-5)) calculated in S280. The alcohol concentration (gas concentration) contained in (sample gas) is calculated.

  Specifically, first, the difference average value ΔV1ave (n− of the output data of the first infrared detection element 135 is calculated using a map or a calculation formula indicating the correlation between the output data of the first infrared detection element 135 and the gas concentration. The gas concentration C (n-5) corresponding to 5) is calculated. The map or calculation formula is prepared based on actual measurement data.

  In subsequent S320, it is determined whether or not the gas concentration obtained in S310 is greater than a predetermined gas concentration determination value TH2. If the determination is affirmative, the flow proceeds to S330, and if the determination is negative, the flow proceeds to S340.

  When an affirmative determination is made in S320 and the process proceeds to S330, “high concentration determination” is set as a determination result of the detected gas concentration in S330. That is, in S330, based on the determination result in S320, a process of determining that “the concentration of alcohol contained in exhaled breath (sample gas) is high” is performed.

  If a negative determination is made in S320 and the process proceeds to S340, “low concentration determination” is set as a determination result of the detected gas concentration in S340. That is, in S340, based on the determination result in S320, a process of determining that “the concentration of alcohol contained in exhaled breath (sample gas) is low” is performed.

When the processing in S330 or S340 is completed, in subsequent S350, the determination result set in S330 or S340 is output to an external device not shown in FIG.
When the process in S350 is completed, the present process (gas concentration detection process) is terminated.

  As described above, when the gas concentration detection process is executed, first, the heater 114 is activated (S120), and the temperature of the first infrared detection element 135 and the temperature of the second infrared detection element 137 are both in the normal range. Then (YES in S130), ON / OFF control of the white light source 115 is performed (S140).

  Thereafter, the acquisition of the output data of the first infrared detection element 135 and the output data of the second infrared detection element 137 is started (S150), the calculation of the moving average value of each output data is started (S160), the ON maximum value and A difference value from the OFF minimum value is calculated (S240), an average difference value is calculated (S280), and a gas concentration is calculated (S310).

  Here, FIG. 4 shows a timing chart showing an example of each state of the ON / OFF state of the white light source 115, the sensor output (output data) of the first infrared detection element 135, and the moving average value. In FIG. 4, the states in the six cycles where the period counter variable n is n = 1 to 6 (in other words, the states in the six cycles from the first cycle T1 to the sixth cycle T6) are shown. Show.

  As shown in FIG. 4, for example, in the light source ON period T1a in the first cycle T1 (n = 1), both the sensor output and the moving average value increase with time, and the first cycle T1 Among these, in the light source OFF period T1b, the sensor output and the moving average value both decrease with time.

  During the light source ON period T1a, a negative determination is made in S220 and the processes in S170 to S220 are repeatedly executed. When the determination in S170 is affirmative and S180 is executed, the latest moving average value is obtained. A comparison operation with the ON maximum value stored at the time of the previous processing execution is performed, and a large value is stored as the ON maximum value (ON maximum value V1max and ON maximum value V2max). Further, during the light source OFF period T1b, a negative determination is made in S220 and the processes of S170 to S220 are repeatedly executed. When the negative determination is made in S170 and S210 is executed, the latest moving average value is obtained. A comparison operation with the OFF minimum value stored at the time of the previous process execution is performed, and the small values are stored as OFF minimum values (OFF minimum value V1min and OFF minimum value V2min).

  Of the waveform of the moving average value, the maximum value in the light source ON period is an example of the ON maximum value V1max acquired in S180, and the minimum value in the light source OFF period is the OFF minimum value V1min acquired in S210. It is an example. Further, as shown in FIG. 4, in each cycle, a difference value ΔV1 (n) (= ON maximum value V1max−OFF minimum value V1min) that is a difference value between the ON maximum value V1max and the OFF minimum value V1min is calculated. .

  At this time, the difference value ΔV2 (n) (= ON maximum value V2max−OFF minimum value) which is a difference value between the ON maximum value V2max and the OFF minimum value V2min also with respect to the sensor output (output data) of the second infrared detection element 137. V2min) is calculated.

  Then, the difference value ΔV1 (n) is calculated for the sensor output (output data) of the first infrared detecting element 135 in the period from the first cycle T1 to the fifth cycle T5 (period counter variable n = 1 to 5). (Affirmative determination in S270), the difference average value ΔV1ave (1), which is the average value of the five difference values ΔV1 (n), is calculated (S280). At this time, the difference average value ΔV2ave (1), which is the average value of the five difference values ΔV2 (n), is also calculated for the sensor output (output data) of the second infrared detection element 137.

  Thereafter, during the period for determining whether or not the introduction of the exhaled air (sample gas) into the container 113 is started (S290), and the exhaled air (sample gas) introduced into the container 113 becomes an amount necessary for gas detection. During this period (during the period when the flow rate integrated value is equal to or less than the flow rate determination value TH1, negative determination is made at S300), the difference average value ΔV1ave (n-5) and the difference average value ΔV2ave (n-5) are repeatedly calculated. The

  Such calculation of the difference average value is repeatedly executed while moving the calculation target period for each cycle (S170 to S300). That is, when the calculation of the difference average value and the gas concentration in the period from the first cycle T1 to the fifth cycle T5 is completed, the period from the second cycle T2 to the sixth cycle T6 (period counter variable n = 2 to 6). ) Is executed, and thereafter, the calculation is executed in the period from the third cycle T3 to the seventh cycle T7 (period counter variable n = 3 to 7).

  When the exhaled air (sample gas) introduced into the container 113 reaches an amount necessary for gas detection (the flow rate integrated value is larger than the flow rate determination value TH1, affirmative determination is made in S300), the difference average calculated last is calculated. Based on the value ΔV1ave (n-5) and the difference average value ΔV2ave (n-5), the gas concentration is calculated (S310).

[1-3. Measurement result]
Here, the difference average value ΔV1ave (n−5) of the output data of the first infrared detection element 135 obtained by using the gas concentration detection device 1 of the present embodiment, and the output data of the infrared detection element without using the moving average The measurement result carried out to compare the difference value ΔV calculated from the above will be described.

  FIG. 5 shows measurement results of the difference average value ΔV1ave (n−5) of the output data of the first infrared detection element 135 and the difference value ΔV calculated from the output data of the infrared detection element without using the moving average. .

  In FIG. 5, the difference average value ΔV1ave (n−5) of the output data of the first infrared detection element 135 is shown as an example, and the difference value ΔV calculated from the output data of the infrared detection element without using the moving average is shown. It shows as a comparative example.

  As can be seen from FIG. 5, the waveform of the comparative example greatly fluctuates, whereas the waveform of the embodiment has a small fluctuation range. Specifically, in the waveform shown in FIG. 5, the difference between the maximum value and the minimum value in the waveform of the comparative example is 12.64 [mV], whereas the maximum value and the minimum value in the waveform of the example are. And 1.59 [mV].

From this, it can be seen that the gas concentration detection apparatus 1 of the present embodiment can suppress the influence of noise and the like as compared with a conventional detection apparatus that does not use a moving average.
[1-4. effect]
As described above, the gas concentration detection apparatus 1 of the present embodiment uses the output data of the first infrared detection element 135 and the output data of the second infrared detection element 137 as they are when calculating the gas concentration (alcohol concentration). Instead, the gas concentration is calculated using the moving average value of these output data.

  In other words, even when the output data of the first infrared detection element 135 and the output data of the second infrared detection element 137 are greatly fluctuated instantaneously due to the influence of noise (disturbance factor), the moving average value is Since the fluctuation range is smaller than the instantaneous fluctuation range of the measurement data, the influence of noise (disturbance factor) and the like can be suppressed when calculating the gas concentration.

  Regarding the calculation of the moving average value, not only the output data of the first infrared detecting element 135 and the output data of the second infrared detecting element 137 but also the moving average of the difference value ΔV1 (n) and the difference value ΔV2 (n). The values (difference average value ΔV1ave (n-5), difference average value ΔV2ave (n-5)) are calculated and stored.

  As described above, by calculating the moving average value over a plurality of stages with respect to the output data of the first infrared detection element 135 and the output data of the second infrared detection element 137, the influence of noise (disturbance factor) can be further suppressed. , A decrease in gas concentration detection accuracy can be suppressed.

  Therefore, according to the gas concentration detection device 1 of the present embodiment, even if the output data of the first infrared detection element 135 and the output data of the second infrared detection element 137 fluctuate due to the influence of noise or the like, the gas concentration The reduction in detection accuracy can be suppressed.

  Further, since the gas concentration detection device 1 of the present embodiment determines whether or not the integrated flow value of the exhaled air (sample gas) introduced into the container 113 has exceeded the flow determination value TH1, the exhaled gas is supplied to the container 113. It is possible to determine whether or not the gas concentration has been sufficiently introduced, and to avoid calculating the gas concentration in a situation where the introduction of exhalation into the container 113 is insufficient.

  That is, the latest difference average value (difference average value ΔV1ave (n-5) and difference average value ΔV2ave (n-5)) when the integrated flow value of exhaled breath introduced into the container 113 exceeds the flow rate determination value TH1. Based on the above, by calculating the alcohol gas concentration, the alcohol gas concentration can be calculated in a state where the exhaled gas is sufficiently introduced into the container 113.

  Further, since the gas concentration is calculated using the moving average value, no matter what timing the accumulated flow value of exhaled breath introduced into the container 113 exceeds the flow rate determination value TH1, the actual sample gas ( An appropriate detection result corresponding to the concentration of (expired air) can be obtained, and a decrease in gas concentration detection accuracy can be suppressed.

Therefore, according to the present embodiment, it becomes difficult to generate a detection error due to insufficient introduction of exhalation into the container 113, and a decrease in gas concentration detection accuracy can be suppressed.
Moreover, the gas concentration detection apparatus 1 of this embodiment is provided with the heater 114, and when the temperature of the 1st infrared rays detection element 135 and the temperature of the 2nd infrared rays detection element 137 are determined to be a normal range (affirmation determination by S130) ), Gas concentration detection using the output data of the first infrared detection element 135 and the output data of the second infrared detection element 137 is executed.

  The normal range in S130 is “a temperature range in which the surfaces of the first wavelength selection filter 131, the second wavelength selection filter 133, the first infrared detection element 135, and the second infrared detection element 137 are not condensed”.

  From this, after confirming that the surfaces of the first wavelength selection filter 131, the second wavelength selection filter 133, the first infrared detection element 135, and the second infrared detection element 137 are in a normal state where no condensation occurs, the gas concentration Arithmetic can be performed. That is, fluctuations in the amount of light received by the first infrared detection element 135 and the second infrared detection element 137 due to the influence of condensation can be suppressed, and a decrease in detection accuracy of the concentration of the measurement target gas can be suppressed.

  Therefore, according to the present embodiment, it was confirmed that the surfaces of the first wavelength selection filter 131, the second wavelength selection filter 133, the first infrared detection element 135, and the second infrared detection element 137 are in a normal state where no condensation occurs. Since the gas concentration calculation can be executed as described above, it is possible to suppress a decrease in detection accuracy of the gas concentration.

[1-5. Correspondence with Claims]
Here, the correspondence of the words in the claims and the present embodiment will be described.
Human exhalation corresponds to an example of a sample gas, alcohol corresponds to an example of a measurement target gas, the container 113 corresponds to an example of a measurement cell, and the white light source 115 corresponds to an example of a light source.

  The first wavelength selection filter 131 and the first infrared detection element 135 correspond to an example of a first light receiving unit, and the second wavelength selection filter 133 and the second infrared detection element 137 correspond to an example of a second light reception unit.

  The control unit 151 corresponds to an example of a detection unit, the control unit 151 that executes S170 corresponds to an example of a moving average calculation unit, the control unit 151 that executes S190 corresponds to an example of a maximum value calculation unit, and S220 The controller 151 to be executed corresponds to an example of a minimum value calculation unit.

  The control unit 151 that executes S250 corresponds to an example of a difference value calculation unit, the control unit 151 that executes S280 corresponds to an example of a difference average calculation unit, and the control unit 151 that executes S290 is an example of an integrated flow rate determination unit. The control unit 151 that executes S300 corresponds to an example of a density calculation unit.

The heater 114 corresponds to an example of a heater, and the control unit 151 that executes S130 corresponds to an example of a temperature determination unit.
[2. Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

  For example, the above embodiment includes the heater 114, and in the gas concentration detection process, the gas concentration is calculated when an affirmative determination is made in S130. However, the first wavelength selection filter 131 and the second wavelength selection are configured. When used in an environment where the surfaces of the filter 133, the first infrared detection element 135, and the second infrared detection element 137 are not condensed, a heater is not provided and S120 and S130 in the gas concentration detection process are omitted. Also good.

  In addition, the determination values (temperature conditions, time conditions, etc.) of various parameters used in the gas concentration detection process are not limited to the above-mentioned numerical values, and arbitrary values according to the application within a range where appropriate determination processes are possible. Can be taken.

Furthermore, regarding the calculation of the moving average value in S170, the number of data used for the calculation of the average value is not limited to 150, and any value can be taken according to the application.
Further, the flow rate determination value TH1 in S290 is not limited to “a value corresponding to exhalation 1.0 [L]”, and an arbitrary value can be set according to the use and purpose.

  DESCRIPTION OF SYMBOLS 1 ... Gas concentration detection apparatus, 111 ... Infrared type gas sensor, 113 ... Container, 114 ... Heater, 115 ... White light source, 117 ... Base, 131 ... 1st wavelength selection filter, 133 ... 2nd wavelength selection filter, 135 ... 1st Infrared detecting element, 137... Second infrared detecting element, 151.

Claims (3)

In the gas concentration detection device that detects the concentration of the measurement target gas contained in the sample gas,
A measurement cell into which the sample gas is introduced;
A light source for irradiating the sample gas introduced into the measurement cell with infrared light;
A first light receiving means having a different wavelength region, and detecting infrared light irradiated from the light source and passed through the sample gas; and a second light receiving means;
Detection means for detecting a concentration of a measurement target gas contained in the sample gas based on measurement data obtained by the first light receiving means and measurement data obtained by the second light receiving means;
A gas concentration detecting device comprising:
The detection means includes
A moving average calculating means for calculating respective moving average values of the measurement data by the first light receiving means and the measurement data by the second light receiving means;
Of the moving average value of the measurement data by the first light receiving means, the first data maximum value which is the maximum value during the irradiation period of infrared light by the light source, and the moving average value of the measurement data by the second light receiving means A maximum value calculating means for calculating a second data maximum value, which is a maximum value in the irradiation period of infrared light from the light source;
Of the moving average value of the measurement data by the first light receiving means, the first data minimum value that is the minimum value in the non-irradiation period of the infrared light by the light source and the moving average value of the measurement data by the second light receiving means A minimum value calculating means for calculating a second data minimum value which is a minimum value in a non-irradiation period of infrared light by the light source;
A first data difference value that is a difference value between the first data maximum value and the first data minimum value, and a second data difference value that is a difference value between the second data maximum value and the second data minimum value. Difference value calculating means for calculating
Difference average calculation means for calculating a first data difference average value that is a moving average value of the first data difference value and a second data difference average value that is a moving average value of the second data difference value;
Concentration calculating means for calculating the concentration of the measurement target gas contained in the sample gas based on the first data difference average value and the second data difference average value;
Providing
A gas concentration detection device characterized by the above. An integrated flow rate determining means for determining whether or not an integrated flow rate value of the sample gas introduced into the measurement cell exceeds a predetermined flow rate determination value;
The concentration calculation means is based on the latest first data difference average value and second data difference average value when the integrated flow determination means determines that the integrated flow value exceeds the flow determination value. Calculating the concentration of the measurement target gas contained in the sample gas;
The gas concentration detection apparatus according to claim 1. A heater for heating the first light receiving means and the second light receiving means;
Temperature determining means for determining whether or not each temperature of the first light receiving means and the second light receiving means is within a predetermined normal range;
With
When the temperature determination unit determines that the temperatures of the first light receiving unit and the second light receiving unit are within the normal range, the detection unit calculates the concentration of the measurement target gas;
The gas concentration detection device according to claim 1 or 2, wherein