JPH08128956A - Gas concentration measuring equipment - Google Patents

Abstract

PURPOSE: To provide gas concentration measuring equipment capable of accurate ly measuring the concentration of gas of specific kind in an atmosphere in spite of simple constitution. CONSTITUTION: Light containing a component of wave length (=λ1 , ...) which is absorbed by gas of the kind of the object of concentration measurement and light containing a component of wave length (=λ0 ) which is not actually absorbed by gas of the kind contained in gas of the object of the concentration measurement are outputted from a light source 100, and radiated to a container 200 in which gas of the object of measurement is filled. The intensity of light of wave length (=λ0 ) through the container 200 is detected with a light detecting part 300, and based on the detected result, the light intensity outputted from the light source 100 is controlled so as to be constant through from a feedback part 400 to a driving part 300. After the light intensity outputted from the light source 100 is controlled so as to be constant, the intensity of light of wave length (=λ1 , ...) is detected with a detecting part 300, and based on the detected result, the concentration of gas of specific kind is measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas concentration measuring device for measuring the concentration of a specific gas component in an atmosphere.

[0002]

2. Description of the Related Art A gas concentration measuring device that employs light as a probe to measure the concentration of a specific gas species of a gas in an atmosphere is widely used in the fields of environmental measurement and pollution gas measurement. In such a gas concentration measuring device that has been conventionally used to measure the concentration of a specific gas species, there are two types depending on whether the number of light receiving elements used is one or two.

FIG. 8 is a typical configuration diagram of a conventional first type gas concentration measuring device (hereinafter referred to as a device of Conventional Example 1) using one light receiving element. As shown in FIG. 8, the apparatus of Conventional Example 1 (a) is a periodic (period = T ₁ ) component of a wavelength range including a wavelength (λ ₁ ) having absorption by a specific gas species whose concentration is to be measured. A light source 910 provided with a halogen lamp that generates various pulsed lights, and (b) a gas to be measured is stored under a constant pressure, and the light output from the light source 910 is input from the end surface 921 and passed through the internal atmosphere. After that, the gas chamber 920 that outputs from the end surface 922
And (c) a bandpass filter (BPF) 930 for inputting the light output from the end face 922 and selecting and transmitting light having a wavelength substantially equal to wavelength = λ _1, and (d) light passing through the BPF 930. Pyroelectric element 940 that receives light, detects the intensity of the received light, and outputs an electric signal according to the detected light intensity.
And (e) an amplifier 950 that inputs the electric signal output from the pyroelectric element 940, amplifies and outputs the signal, and (f) a signal that outputs the signal output from the amplifier 950 and synchronizes with cycle = T _1. -In amplifier 960 for extracting and outputting
And (g) a smoothing circuit 970 that inputs the signal output from the lock-in amplifier 960, smoothes it, and outputs it.
(H) An amplifier 955 that inputs the signal output from the smoothing circuit 970, amplifies and outputs the signal, and (i) inputs the signal output from the amplifier 955 and inputs the specific gas in the gas stored in the gas chamber 920. And a processing unit 980 for obtaining the concentration of the seed.

In the device of Conventional Example 1, the pulsed light output from the light source 910 enters the gas chamber 920 containing the gas to be measured from the end surface 921 and is output from the end surface 922 after traveling through the gas to be measured. It For the light output from the end face 922, the BPF 930 selects a wavelength component substantially the same as the wavelength = λ _1, and the intensity of this wavelength component is detected by the pyroelectric element 940. The electric signal which is the detection result of the pyroelectric element 940 is amplified by the amplifier 950, and then the lock-in amplifier 960 extracts the component synchronized with the cycle = T ₁ of the pulsed light and is smoothed by the smoothing circuit 970. The smoothed signal is amplified by the amplifier 955 and input to the processing unit 980. The processing unit 980 obtains the concentration of the specific gas species (for example, CO ₂ ) from the amplitude value of the input signal.

FIG. 9 is a typical block diagram of a second conventional type gas concentration measuring device (hereinafter referred to as a conventional example 2 device) using two light receiving elements. As shown in FIG. 9, the device of Conventional Example 2 (a) is substantially absorbed depending on the wavelength (λ ₁ ) at which there is absorption by a specific gas species to be measured for concentration and the gas species in the gas to be measured. Wavelength (λ
Light source 910 including a halogen lamp that generates periodic (period = T ₁ ) pulsed light of a component in a wavelength range including ₂ ).
And (b) a gas chamber 925 that stores a gas to be measured under a constant pressure, inputs the light output from the light source 910 from the end surface 926, and outputs the light from the end surface 927 after passing through the internal atmosphere, (C) Area 92 of end surface 927
The bandpass filter (BP) which inputs the light output from 7 ₁ and selects and transmits the light of the wavelength substantially the same as the wavelength = λ ₁
F) 931 and a bandpass filter (BPF) 932 which inputs the light output from the region 927 ₂ of the end face 927 and selects and transmits the light of the wavelength substantially equal to the wavelength = λ _2.
And (d) receiving light through the BPF 931, detecting the intensity of the received light, and outputting light through the pyroelectric element 941 that outputs an electrical signal corresponding to the detected light intensity, and receiving light through the BPF 932. A pyroelectric element 942 that detects the intensity of the received light and outputs an electric signal according to the detected light intensity;
(E) An amplifier 951 for inputting, amplifying, and outputting an electric signal output from the pyroelectric element 941, and a pyroelectric element 9
A lock-in for inputting the electric signal output from 42, amplifying and outputting the amplified signal, and (f) inputting the signal output from the amplifier 951, extracting and outputting the signal synchronized with the cycle = T _1. A lock-in amplifier 962 which inputs the signals output from the amplifier 961 and the amplifier 951 and extracts and outputs a signal in synchronization with the cycle = T ₁ , and (g)
Input the signal output from the lock-in amplifier 961,
A smoothing circuit 971 for smoothing and outputting, and a smoothing circuit 972 for inputting and smoothing and outputting a signal output from the lock-in amplifier 962, and (h) a signal output from the smoothing circuit 971 and an output from the smoothing circuit 972. The calculated signal is input, the ratio of the amplitude value of the signal output from the smoothing circuit 971 to the amplitude value of the signal output from the smoothing circuit 972 is calculated, and a signal having an amplitude corresponding to the value of the calculation result is output. A divider 990, and (i) an amplifier 955 which inputs, amplifies and outputs the signal output from the divider 990,
(J) A processing unit 985 that receives the signal output from the amplifier 955 and obtains the concentration of the specific gas species in the gas stored in the gas chamber 920.

In the apparatus of the second conventional example, the light of the wavelength = λ ₁ and λ ₂ components of the pulsed light output from the light source 910 individually travels in the gas to be measured in the same manner as in the first conventional example. The intensity is detected and smoothed. The two smoothed signals are input to the divider 990. The divider 990 has a wavelength = λ
The ratio of the amplitude value of the signal for wavelength = λ ₁ to the amplitude value of the signal for ₂ is calculated, and the signal having the amplitude corresponding to the value of the calculation result is output. The value of this calculation result is, in principle, a value that does not depend on the fluctuation of the amount of light generated by the light source, and the signal corresponding to the calculation result is amplified by the amplifier 956 and then processed by the processing unit 9.
Enter in 85. The processing unit 985 obtains the concentration of the specific gas species (for example, CO ₂ ) from the amplitude value of the input signal.

[0007]

Since the conventional gas concentration measuring device is constructed as described above, it has the following problems.

In the device of Conventional Example 1, if the amount of light generated by the light source changes due to deterioration of the light source or the like, the measured concentration changes regardless of the value of the concentration of the gas species for concentration measurement in the gas under measurement. There was a problem that it would end up.

Further, the device of Conventional Example 2 is a device which can cancel the change in the amount of light generated by the light source due to deterioration of the light source in principle, but the divider currently available is expensive. In addition, since the temperature stability is poor, there is a problem in that accurate measurement cannot be performed when the environment temperature in which the device is installed changes.

The present invention has been made in view of the above, and an object of the present invention is to provide a gas concentration measuring device having a simple structure and capable of accurately measuring the concentration of a specific gas species in an atmosphere. To do.

[0011]

The gas concentration measuring device according to the present invention comprises: (a) a light source for generating light having a component in a predetermined wavelength range having an intensity according to an instruction from the outside, and (b) a constant light source. A container for storing the gas under pressure, inputting the light output from the light source into the inside from the first end face, and outputting the light from the first number area of the second end face after passing through the internal atmosphere, respectively. (C) First light for inputting the light output from the first region of the second end face of the container and detecting the intensity of light having a wavelength substantially the same as the set first wavelength value A first photodetector having a detection system; and (d) a feedback unit for instructing the light source of the intensity of the output light according to the value of the difference between the detected light intensity and the reference value notified from the first photodetector. And (e) the light emitted from each of the regions arranged in each region of the second end face of the container except the first region. A light having a wavelength substantially the same as the wavelength value set for each region, and a second number including a number of photodetection systems less than the first number for detecting the intensity of the light of the selected wavelength. And (f) a processing unit that collects the light intensity for each wavelength notified from the second light detection unit and obtains the concentration of the gas species to be measured of the gas stored in the container. It is characterized by including.

Here, the light having the first wavelength value is not substantially absorbed by the gas species in the gas contained in the container, and each region of the second end face of the container except the first region is not absorbed. The light having the wavelength value set for each may be absorbed by the gas species to be measured.

The first number is 2, and the gas species to be measured is CO ₂ or H ₂ O, or the first number is 3, and the gas species to be measured are CO ₂ and H ₂ O. H
_It may be characterized by being ₂ O.

The light output from the light source may be pulsed light.

Further, the photodetection system inputs the light output from the corresponding region of the second end face of the container, selects the light having a wavelength substantially the same as the set wavelength value, and transmits the selected wavelength. Receives the light transmitted through the filter and the wavelength filter,
A photodetector for detecting the intensity of the received light may be provided.

[0016]

After storing the gas to be measured under a predetermined pressure in the container, the concentration measurement of the gas species (N kinds of gas species) of the concentration in the gas to be measured by the gas concentration measuring device of the present invention is started. To do.

First, there is substantially no absorption depending on the wavelength of light (= λ ₁ , ..., λ _N ; wavelength values different from each other) that is absorbed by the gas species to be measured for concentration and the gas species contained in the gas to be measured. The light source generates light having a first wavelength (= λ ₀ ) of light at an initial intensity. In the present invention, the light emitted from the light source may be continuous light or pulsed light.
However, if pulsed light is adopted, the cause of instability due to continuous light can be reduced. The light output from the light source enters the container from the first end surface, travels in the atmosphere filled with the measurement target gas, and then exits from the second end surface. The second end face is virtually divided into (N + 1) regions, and light is emitted from all the regions.

The light emitted from the first region is input to the first photo-detecting section, and the first photo-detecting system causes the wavelength = λ.
The intensity of light having substantially the same wavelength as ₀ is detected, and the detection result corresponding to the detected intensity of light is notified to the feedback unit. The first photodetection system is a wavelength filter that receives the light output from the first region of the second end face of the housing and selects and transmits the light having a wavelength substantially equal to wavelength = λ _0. And a photodetector for receiving the light transmitted through the wavelength filter and detecting the intensity of the received light.

The feedback unit detects the difference between the detected light intensity notified from the first light detection unit and the reference value, and when the detected light intensity is larger than the reference value, the reduction amount of the intensity of the output light, When the detected light intensity is smaller than the reference value, the light source is instructed to increase the intensity of the output light. As a result, a feedback loop of light source-first photodetector-feedback-light source is formed, and the intensity of light output from the light source is controlled to a constant value.

The light emitted from the second to (N + 1) th regions of the second end surface of the container is input to the second photodetector. In the second photodetector, the i-th (i = 2 to (N + 1))
The light emitted from the th region is input and the wavelength = λ _i-1
The intensity of light having substantially the same wavelength as is detected by the i-th photodetection system, and the detection results corresponding to the N photodetection intensities are notified to the processing unit. In the above feedback operation, the detection result of the second photodetector after the output light intensity of the light source becomes a constant value is a value normalized by the output light intensity of the light source.

The processing unit collects the detection result output from the second detection unit after the output light intensity of the light source reaches a constant value, and based on the collection result, the measurement target gas of the gas species whose concentration is to be measured. Find the concentration in the medium.

When there is only one kind of gas whose concentration is to be measured, a feedback loop for controlling the output light intensity of the light source to a constant value by a detection system according to the intensity of light having a wavelength absorbed by this gas species. Is adopted as an element of, and the wavelength = λ ₀ in the processing unit.
It is also possible to collect the detection results regarding the concentration of the gas species whose concentration is to be measured in the measurement target gas.

[0023]

Embodiments of the gas concentration measuring apparatus of the present invention will be described below with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

(First Embodiment) FIG. 1 is a block diagram of the first embodiment of the gas concentration measuring apparatus of the present invention. The apparatus of this embodiment measures the concentration of CO _{2 in} the atmosphere. As shown in FIG. 1, this device (a) has an intensity according to an instruction from the outside, a light component of wavelength = 4.3 μm and a wavelength = 3.9 μm.
Light source 10 for generating pulsed light having a light component of
0 and (b) A storage that stores the atmosphere under atmospheric pressure, inputs the light output from the light source 100 into the inside from the end face 210, and outputs the light from the regions 221 and 222 of the end face 220 after passing through the internal atmosphere. Vessel 200, (c)
The photodetection unit 30 including the photodetection system 310 that receives the light output from the region 221 of the end face 220 of the container 200 and detects the intensity of the light of the wavelength substantially equal to the wavelength = 3.9 μm.
0, (d) a feedback unit 400 for instructing the light source 100 to output light intensity according to the value of the difference between the light detection result notified from the light detection unit 300 and the reference value, and (e) the container 200. The light output from the region 222 of the end face 220 is input, and the wavelength =
The photodetector 500 including a photodetection system 510 for detecting the intensity of light having a wavelength substantially equal to 4.3 μm, and (f) the photodetection results notified from the photodetector 500 are collected and stored in the container 2
Processing unit 710 for obtaining the concentration of CO _{2 in} the atmosphere stored in the storage unit 00. It should be noted that the light of wavelength = 3.9 μm is not substantially absorbed by the gas species in the atmosphere, and the wavelength = 4.3 μm.
Light is absorbed only by CO ₂ in the atmospheric gas species.

The photodetection section 300 includes a photodetection system 310 and
A signal processing unit 320 that receives the light intensity detection signal output from the light detection system 310, synchronizes with the pulse period, and then smoothes and outputs the signal. Then, the photodetection system 310 inputs the light output from the region 221, and the wavelength = 3.9 μm.
A wavelength filter 3 that selects and outputs light of the same wavelength as
11, a pyroelectric element 312 that receives the light transmitted through the wavelength filter 311 and detects the intensity of the received light, and an amplifier 3 that amplifies the light intensity signal output from the pyroelectric element 312.
13 and 13. In addition, the signal processing unit 320 receives the signal output from the photodetection system 310, and a lock-in amplifier 321 that extracts a component synchronized with the cycle of the pulsed light.
A smoothing circuit 322 that inputs the signal output from the lock-in amplifier 321, smoothes and outputs the signal, and an amplifier 323 that amplifies the signal output from the smoothing circuit 322 are provided.

The feedback unit 400 compares the signal output from the light detecting unit 300 with a reference value and outputs a signal having a value corresponding to the difference, and the light source 100 outputs the signal output from the comparing circuit 410. And a drive circuit 420 for converting the pulsed light into the pulsed light drive mode. Then, the drive circuit 420
Includes a conversion circuit 421 that converts the form of the signal output from the comparison circuit 410, and a blinking control circuit 422 that makes the output signal of the conversion circuit 421 into a periodic pulse. Further, as shown in FIG. 2, the comparison circuit 410 includes an operational amplifier 411 in which the signal output from the photodetector 300 is input to the negative input terminal of the operational amplifier 411 and the reference voltage is input to the positive input terminal. , Reference voltage value is variable resistor 41
It is variable by 2.

The light detecting section 500 includes a light detecting system 510 and
The signal processing unit 320 receives the light intensity detection signal output from the light detection system 510, synchronizes with the pulse period, and then smoothes and outputs the signal. Then, the light detection system 510 inputs the light output from the region 222, and the wavelength = 4.3 μm.
A wavelength filter 5 for selecting and outputting light having substantially the same wavelength as
11, a pyroelectric element 312 that receives light transmitted through the wavelength filter 511 and detects the intensity of the received light, and an amplifier 3 that amplifies the light intensity signal output from the pyroelectric element 312.
13 and 13.

The apparatus of this embodiment measures the CO ₂ concentration in the atmosphere as follows.

After the atmosphere, which is the gas to be measured, is stored in the container 200 under a predetermined pressure, the concentration measurement of CO ₂ which is the gas species whose concentration is to be measured in the atmosphere is started by the gas concentration measuring device of this embodiment. To do.

First, the wavelength of CO ₂ light λ ₁ (= 4.3 μm)
m) and gas species contained in the atmosphere (including CO ₂ ,
N ₂ , O _2, etc.), a wavelength λ ₀ that is substantially free of absorption.
The light source generates pulsed light including (= 3.9 μm) at an initial intensity. The light output from the light source 100 enters the housing 200 from the end face 210, and is emitted from the end face 220 after traveling in an atmosphere filled with the atmosphere. The end face 220 is virtually divided into two regions 221, 222, and light is emitted from both regions.

The light emitted from the area 221 is detected by the photodetector 3
00, and the light detection system 310 detects the intensity of light having a wavelength substantially equal to wavelength = λ ₀ . Light detection system 310
Then, the wavelength filter 311 selects and transmits light having a wavelength substantially the same as wavelength = λ _0, and then the pyroelectric element 312 detects the received light intensity, and outputs an intensity detection signal corresponding to the received light intensity to the photodetection system 3
It is output as an output signal of 10. The signal output from the light detection system 310 is input to the signal processing unit 320. In the signal processing unit 320, the lock-in amplifier 321 extracts from the input signal a component that is synchronized with the cycle of the pulsed light emitted from the light source 100, and then is output as a substantially direct current signal whose waveform is smoothed by the smoothing circuit 322 as a photodetection unit. The output signal of 300 is output to the feedback unit 400.

In the feedback section 400, first, the comparison circuit 410
, And compares the set reference value with the DC value of the input substantially DC signal, which is the photodetection result of the photodetector 300, and outputs an output signal according to the difference. That is, when the light detection result is larger than the reference value, the output value of the comparison circuit 410 is reduced, and when the light detection result is smaller than the reference value, the output value of the comparison circuit 410 is increased to reduce the output value. Change. The signal output from the comparison circuit 410 is output to the light source 100 via the drive circuit 420 as a signal for designating the output intensity. In the device of the present embodiment, the drive circuit 420 generates a pulse, and the light source 100 generates light according to the form of the waveform of the notified output intensity instruction signal. As a result,
Light source 100-Light detection unit 300-Return unit 400-Light source 10
A feedback loop of 0 is formed, and the light source 100
The intensity of the light output from is controlled to a constant value.

FIG. 3 is a timing chart showing the operating condition of the apparatus of this embodiment after the output light intensity of the light source 100 is controlled to be constant. Hereinafter, the operation of the apparatus of this embodiment after the output light intensity of the light source 100 is controlled to be constant will be described.

The light emitted from the region 222 of the end face 220 of the container 200 is input to the photodetection section 500, and the photodetection system 510 detects the intensity of the light having a wavelength substantially equal to wavelength = λ _1. . In the light detection system 510, the wavelength filter 51
After selecting and transmitting light having a wavelength substantially the same as the wavelength = λ _{1 at 1} , the pyroelectric element 512 detects the received light intensity and outputs an intensity detection signal corresponding to the received light intensity as an output signal of the photodetection system 510. To do. The signal output from the light detection system 510 is input to the signal processing unit 520. In the signal processing unit 520, the lock-in amplifier 521 extracts a component that is synchronized with the cycle of the pulsed light emitted from the light source 100 from the input signal, and then, as a substantially direct current signal whose waveform is smoothed by the smoothing circuit 522, as a light detection unit. The output signal of 500 is output to the processing unit 710.

After the output light intensity of the light source reaches a constant value, the processing unit 710 collects the detection results output from the detection unit 500 and obtains the concentration of CO _{2 in} the atmosphere based on the collection results.

In the above measurement, the feedback operation
Light detection unit 500 after the output light intensity of the light source reaches a constant value
The detection result in 1 is a value standardized by the output light intensity of the light source 100. Therefore, since the light detection result for a predetermined irradiation light amount can be obtained regardless of the deterioration of the light emission characteristics of the light source 100 over time, the density measurement can be performed accurately and stably without division.

Further, since the device of this embodiment has a simple structure and is suitable for downsizing, CO ₂ incorporated in the air conditioner is
Suitable as a density sensor.

(Second Embodiment) FIG. 4 is a block diagram of the second embodiment of the gas concentration measuring apparatus of the present invention. The apparatus of this embodiment measures the concentration of CO ₂ in the atmosphere as in the first embodiment, except that the processing after the light intensity detection is performed by the processing unit 820 equipped with a microprocessor. That is, the apparatus of the present embodiment is (a) a halogen light source 100 which generates pulsed light having an intensity according to an instruction from the outside and having a light component of wavelength = 4.3 μm and a light component of wavelength = 3.9 μm. ,
(B) The light source 100 stores the atmosphere under atmospheric pressure and
The light output from the end face 210 is input into the inside, and after passing through the internal atmosphere, the regions 221 and 2 of the end face 220
22 and (c) storage device 2 which outputs from 22 respectively.
00, the light output from the region 222 of the end face 220 of 00, and the light detection system 310 for detecting the intensity of the light having the wavelength substantially equal to the wavelength = 3.9 μm, and (d) the end face 220 of the container 200. Input the light output from the region 222 of
A photodetection system 510 for detecting the intensity of light having a wavelength substantially equal to 4.3 μm, and (e) a light intensity detection result notified from the photodetection system 310 is input and compared with an internally set reference value. The light source 1 according to the difference between the light intensity detection result and the reference value.
00 to instruct to change the intensity of the output light, and
After the intensity of the output light becomes constant at 00, the light detection system 510
And a processing unit 800 for obtaining the CO ₂ concentration based on the light intensity detection result notified by the processing unit 800.

The processing section 800 compares the light intensity detection result output from the photodetection system 310 with a preset reference value, and the light intensity detection result output from the photodetection system 310 is the same as the reference value. A light amount control unit 810 for instructing the light source 100 to change the output light intensity so that the light intensity detection result output from the light detection system 510 is collected, and a concentration measuring unit for obtaining a CO ₂ concentration based on the collection result. 820
And The light quantity control unit 810 receives the light intensity detection signal output from the light detection system 310 and converts the light intensity detection signal into digital data.
C) 811 compares the converted digital data with the internally set reference value to calculate the output light intensity for instructing the light source 100, and the output light intensity notified from the comparison unit 812. A pulse generator 813 that generates a 1 Hz pulse having an amplitude value, and a pulse generator 81
The driving circuit 814 that converts the signal notified from the No. 3 into the driving mode of the light source 100. Further, the concentration measuring unit 82
0 is an analog-to-digital converter (ADC) 821 that inputs the light intensity detection signal output from the light detection system 510 and converts it into digital data, and a concentration process that determines the CO ₂ concentration based on the converted digital data. And a section 822.

The apparatus of this embodiment measures the CO ₂ concentration in the atmosphere as follows.

After setting the reference value of the comparison unit 812 of the processing unit 800 and storing the atmosphere as the gas to be measured under a predetermined pressure in the container 200, the concentration in the atmosphere by the gas concentration measuring apparatus of this embodiment is set. The measurement of the concentration of CO ₂ which is the gas species to be measured is started.

First, the wavelength of CO ₂ light λ ₁ (= 4.3 μm)
m) and gas species contained in the atmosphere (including CO ₂ ,
N ₂ , O _2, etc.), a wavelength λ ₀ that is substantially free of absorption.
The light source generates pulsed light including (= 3.9 μm) at an initial intensity. The light output from the light source 100 enters the housing 200 from the end face 210, and is emitted from the end face 220 after traveling in an atmosphere filled with the atmosphere. The end face 220 is virtually divided into two regions 221, 222, and light is emitted from both regions.

With respect to the light emitted from the region 221, the light detection system 310 detects the intensity of light having a wavelength substantially equal to wavelength = λ ₀ . In the light detection system 310, the wavelength filter 31
After selecting and transmitting light having a wavelength substantially the same as the wavelength = λ _{0 in} 1, the pyroelectric element 312 detects the received light intensity and outputs an intensity detection signal corresponding to the received light intensity as an output signal of the photodetection system 310. To do. The signal output from the light detection system 310 is input to the light amount control unit 810 of the processing unit 800. Light amount control unit 81
At 0, the ADC 811 first inputs the output signal from the photodetection system 310 and converts it into digital data. After the digital data is smoothed by the comparison unit 812, it is compared with a set reference value, and the light intensity to be output by the light source 100 is calculated from the comparison result. The calculation result is the pulse generation unit 813.
Is notified, and a pulse of 1 Hz having an amplitude that reflects the calculation result is generated. The pulse signal output from the pulse generation unit 813 is notified to the light source 100 via the drive circuit 814. As a result, a feedback loop of light source 100-light detection system 310-light quantity control 810-light source 100 is formed, and the intensity of light output from light source 100 is controlled to a constant value.

The light emitted from the region 222 of the end face 220 of the container 200 is wavelength = λ by the photodetection system 510.
The intensity of light having the same wavelength as ₁ is detected. Light detection system 5
In 10, the wavelength filter 511 selects light having a wavelength substantially equal to λ ₁ and transmits the selected light, and then the pyroelectric element 512 detects the received light intensity, and outputs an intensity detection signal corresponding to the received light intensity to the light detection system 510. Output as the output signal of. The signal output from the light detection system 510 is the concentration measurement unit 820 of the processing unit 800.
To enter. After the output light intensity of the light source 100 becomes constant, the density measuring unit 820 converts the signal output from the photodetection system 510 into digital data by the ADC 821, smoothes the digital data by the density processing unit 822, and smoothes it. The CO ₂ concentration is calculated from the value of.

In the above measurement, the feedback operation
Light detection system 510 after the output light intensity of the light source reaches a constant value
The light intensity detection result in 1 is a value normalized by the output light intensity of the light source 100. Therefore, similar to the first embodiment, the light detection result for a predetermined irradiation light amount can be obtained regardless of the deterioration of the light emission characteristics of the light source 100 over time, so that accurate and stable density measurement can be performed.

Further, the device of this embodiment has a simpler construction than that of the first embodiment and is suitable for further miniaturization, and is therefore suitable as a CO ₂ concentration sensor incorporated in an air conditioner.

(Third Embodiment) FIG. 5 is a block diagram of the third embodiment of the gas concentration measuring apparatus of the present invention. The apparatus of this embodiment measures the concentration of H ₂ O in the atmosphere in addition to the concentration of CO _{2 in} the atmosphere of the first embodiment. As shown in FIG. 5, the apparatus of the present embodiment virtually divides the end face 220 of the container 200 into three areas (221 to 223) in the apparatus of the first embodiment, and outputs from the area 223. Wavelength λ ₂ (= 5.5 μm) where light is absorbed only by H ₂ O in atmospheric gas components
A light detection unit 600 that detects the light intensity of the substantially same wavelength is further provided. Further, as the light source, wavelength = λ ₀ , λ ₁ , λ ₂
The light source 100 that emits light including the three types of components is used, and the processing unit 730 that determines the H ₂ O concentration in addition to the CO ₂ concentration is employed.

The light detecting section 600 includes a light detecting system 610,
The signal processing unit 320 receives the light intensity detection signal output from the light detection system 610, synchronizes with the pulse period, and then smoothes and outputs the signal. Then, the light detection system 610 inputs the light output from the region 223, and the wavelength = 5.5 μm.
A wavelength filter 6 for selecting and outputting light having substantially the same wavelength as
11, a pyroelectric element 312 that receives the light that has passed through the wavelength filter 611 and detects the intensity of the received light, and an amplifier 3 that amplifies the light intensity signal output from the pyroelectric element 312.
13 and 13.

The apparatus of this embodiment measures the CO ₂ concentration and H ₂ O concentration in the atmosphere as follows. Figure 6
[Fig. 4] is a timing chart showing an operating condition of the device of the present embodiment after the output light intensity of the light source 100 is controlled to be constant.

In the apparatus of this embodiment, the intensity of the light source 100 generated is controlled to be constant as in the first embodiment. Then, the CO ₂ concentration is measured in the same manner as in the first embodiment. In parallel with the measurement of the CO ₂ concentration, the H ₂ O concentration in the atmosphere stored in the container 200 is measured as follows.

The light emitted from the region 223 of the end face 220 of the container 200 is input to the photodetection section 600, and the photodetection system 610 detects the intensity of the light having a wavelength substantially equal to wavelength = λ _2. . In the light detection system 610, the wavelength filter 61
After selecting and transmitting light having a wavelength substantially the same as wavelength = λ _{2 in} 1, the pyroelectric element 312 detects the received light intensity and outputs an intensity detection signal corresponding to the received light intensity as an output signal of the photodetection system 610. To do. The signal output from the light detection system 610 is input to the signal processing unit 320. In the signal processing unit 320, the lock-in amplifier 321 extracts from the input signal a component that is synchronized with the cycle of the pulsed light emitted from the light source 100, and then is output as a substantially direct current signal whose waveform is smoothed by the smoothing circuit 322 as a photodetection unit. The output signal of 600 is output to the processing unit 730.

The processing unit 730 collects the detection results output from the detection unit 600 after the output light intensity of the light source reaches a constant value, and obtains the concentration of H ₂ O in the atmosphere based on the collection results.

Also in the measurement by the apparatus of this embodiment, as in the first embodiment, the light detecting section 500 and the light detecting section 600 after the output light intensity of the light source becomes a constant value by the feedback operation.
The detection result in 1 is a value standardized by the output light intensity of the light source 100. Therefore, since the light detection result for a predetermined irradiation light amount can be obtained regardless of the deterioration of the light emission characteristics of the light source 100 over time, the density measurement can be performed accurately and stably without division.

(Fourth Embodiment) FIG. 7 is a block diagram of the third embodiment of the gas concentration measuring apparatus of the present invention. The apparatus of this embodiment measures the concentration of H ₂ O in the atmosphere in addition to the concentration of CO _{2 in} the atmosphere of the second embodiment. As shown in FIG. 7, the apparatus of this embodiment virtually divides the end face 220 of the container 200 into three areas (221 to 223) in the apparatus of the third embodiment, and outputs from the area 223. Wavelength λ ₂ (= 5.5 μm) where light is absorbed only by H ₂ O in atmospheric gas components
A light detection system 610 for detecting the light intensity of the substantially same wavelength as is further provided. Further, as the light source, wavelength = λ ₀ , λ ₁ , λ ₂
The light source 100 that generates light including the three types of components is used, and the processing unit 850 that includes the concentration processing unit 830 that determines the H ₂ O concentration in addition to the CO ₂ concentration is used.

The density processing unit 830 receives the light intensity detection signal output from the light detection system 610 and converts it into digital data, and an analog-digital converter (ADC) 831.
And a concentration processing unit 832 for obtaining the H ₂ O concentration based on the converted digital data.

The apparatus of this embodiment measures the CO ₂ concentration and H ₂ O concentration in the atmosphere as follows.

In the apparatus of this embodiment, the intensity of the light source 100 generated is controlled to be constant as in the first embodiment. Then, the CO ₂ concentration is measured in the same manner as in the first embodiment. In parallel with the measurement of the CO ₂ concentration, the H ₂ O concentration in the atmosphere stored in the container 200 is measured as follows.

The light emitted from the region 223 of the end face 220 of the container 200 is wavelength = λ by the photodetection system 610.
The intensity of light having the same wavelength as ₂ is detected. Light detection system 6
10, the wavelength filter 611 selects light having a wavelength substantially equal to λ ₂ and transmits the selected light, and then the pyroelectric element 312 detects the received light intensity, and outputs an intensity detection signal corresponding to the received light intensity to the light detection system 610. Output as the output signal of. The signal output from the light detection system 610 is input to the concentration measuring unit 830. After the output light intensity of the light source 100 becomes constant, the density measuring unit 8
At 30, the signal output from the photodetection system 610 is converted into an ADC signal.
After conversion to digital data in 831, the density data is smoothed in the density processing unit 832, and the H ₂ O density is calculated from the smoothed value.

In the above measurement, the feedback operation
Light detection system 510 after the output light intensity of the light source reaches a constant value
The light intensity detection result of the light detection system 610 is the light source 10
The output light intensity is 0, which is a standardized value. Therefore, similar to the first embodiment, the light detection result for a predetermined irradiation light amount can be obtained regardless of the deterioration of the light emission characteristics of the light source 100 over time, so that accurate and stable density measurement can be performed.

Further, the device of this embodiment has a simpler construction than the third embodiment which performs the same function and is suitable for further size reduction. Therefore, the CO ₂ concentration and H ₂ O incorporated in the air conditioner are reduced. It is suitable as a density sensor.

The present invention is not limited to the above embodiment, but can be modified. For example, although the above-mentioned embodiment shows an example of measuring the concentration of a specific gas species (CO ₂ , H ₂ O) in the atmosphere, the present invention can be applied even if the measurement target gas is other than the atmosphere, and the concentration measurement target The gas may be CO or the like.

[0062]

As described above in detail, according to the gas concentration measuring apparatus of the present invention, the light intensity of the light having a wavelength that is not substantially absorbed by the gas species contained in the gas to be measured after passing through the measuring gas. Is detected and is fed back to the light source to control the light intensity generated by the light source to be constant. Then, after the output light intensity of the light source becomes constant, the intensity of the light having a wavelength absorbed by the concentration measurement target gas species after passing through the measurement target gas is measured to measure the concentration of the concentration measurement target gas species. Therefore, regardless of changes in the output light intensity of the light source, it is possible to perform accurate concentration measurement with a simple configuration suitable for downsizing.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a gas measuring device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a main part of a comparison circuit of the gas measuring device according to the first embodiment.

FIG. 3 is a timing chart of the operation of the gas measuring device according to the first embodiment.

FIG. 4 is a configuration diagram of a gas measuring device according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram of a gas measuring device according to a third embodiment of the present invention.

FIG. 6 is a timing chart of the operation of the gas measuring device according to the third embodiment.

FIG. 7 is a configuration diagram of a gas measuring device according to a fourth embodiment of the present invention.

FIG. 8 is a configuration diagram of a conventional gas measuring device.

FIG. 9 is a configuration diagram of a conventional gas measuring device.

[Explanation of symbols]

100 ... Light source, 200 ... Storage device, 300, 500, 60
0 ... Photodetector, 310, 510, 610 ... Photodetector system, 3
11, 511, 611 ... Wavelength filter, 312 ... Pyroelectric element, 320 ... Signal processing unit, 321 ... Lock-in amplifier,
322 ... Smoothing circuit, 400 ... Feedback section, 410 ... Comparison circuit, 420 ... Driving circuit, 710, 730 ... Processing section, 80
0,850 ... Processing unit, 810 ... Light amount control unit, 820, 8
30 ... Concentration measuring unit.

Claims (6)

[Claims] 1. A light source for generating light having a component in a predetermined wavelength range having an intensity according to an instruction from the outside, a gas stored under a constant pressure, and a first light for outputting the light. And an output from the first area of the second end surface of the storage container, which is input to the inside from the end surface of the storage container and outputs from the plurality of first number areas of the second end surface after passing through the internal atmosphere. A first photodetection system for inputting the converted light and detecting the intensity of light having a wavelength substantially the same as the set first wavelength value.
And the detected light intensity value and the reference value notified from the first light detection unit are compared, and the detected light intensity value and the reference value notified from the first detection unit are the same. And a feedback unit for instructing the intensity of output light to the light source, and output from respective regions of the second end face of the container, which are arranged in each region except the first region. A light detection system is provided that selects from the light a light having a wavelength substantially the same as the wavelength value set for each of the regions and detects the intensity of the light of the selected wavelength by one less than the first number. Second
A light detection unit, and a processing unit that collects the light intensity value for each wavelength notified from the second light detection unit and obtains the concentration of the gas species to be measured of the gas stored in the container. A gas concentration measuring device comprising: 2. The light having the first wavelength value is not substantially absorbed by the gas species in the gas contained in the container, and the first region of the second end face of the container is contained. 2. The gas concentration measuring device according to claim 1, wherein light having a wavelength value set for each region except is absorbed by the gas species to be measured. 3. The gas concentration measuring device according to claim 1, wherein the first number is 2, and the gas species to be measured is CO ₂ or H ₂ O. 4. The gas concentration measuring device according to claim 1, wherein the first number is 3, and the gas species to be measured are CO ₂ and H ₂ O. 5. The gas concentration measuring device according to claim 1, wherein the light output from the light source is pulsed light. 6. The light detection system inputs light output from a corresponding region of the second end face of the container, selects light having a wavelength substantially the same as a set wavelength value, and transmits the selected light. The gas concentration measuring device according to claim 1, further comprising: a wavelength filter for controlling the gas concentration, and a photodetector for receiving the light transmitted through the wavelength filter and detecting the intensity of the received light.