JPH05203573A - Infrared ray gas analyzer - Google Patents

Abstract

PURPOSE:To measure the measurement gas concentration of a number of components at high speed by allowing infrared rays at a specified wavelength region to pass through a sample intermittently by a rotary body including a band-pass filter, etc. CONSTITUTION:Infrared rays with for example a wavelength of 2-10mum from a light source 11 are cast to band-pass filters 15 and 16 which are provided at a plurality of windows of a rotary circular plate as a light flux 14 and then the filters 15 and 16 and a glare-protection mask 19 allow infrared rays at a specific wavelength band with a change in wavelength which is specific in terms of time. Infrared rays which are transmitted through the filter 15 and the mask 19 are absorbed by a sample gas 30 which flows from a passage 37 to a passage 38 through a sample chamber 32, are attenuated, and then are received by an infrared rays detector 43. The filters 15 and 16 are laid out alternately for measurement component and for reference light. respectively, a detector 43 performs measurement as current or voltage between electrode terminals 46 and 47 according to the energy and wavelength region of incidence infrared rays and then measures gas component and concentration in reference to the difference between light at the measurement band and the reference light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared gas analyzer which can be used in the fields of medical engineering and biotechnology such as environmental technology for measuring the concentration of gas components in the atmosphere or combustion exhaust gas and the measurement of respiratory air.

[0002]

2. Description of the Related Art An infrared gas analyzer of this kind is generally called a non-dispersive infrared gas analyzer NDIR, and an optical measurement system is formed by a combination of a light source, a sample cell, an infrared detector, a bandpass filter and a chopper. It is configured.

In conventional infrared gas analyzers, various shapes are used for the chopper, for example, one cycle of light is interrupted per revolution, one of which a plurality of cycles of light is interrupted, and the temporal change of the luminous flux of the optical path. Although there are things that can be properly selected depending on the shape, the rotating chopper has been used only for intermittent light. Further, when a bandpass filter is used, it is configured to detect an infrared ray in a specific wavelength region just before the infrared detector, that is, among the infrared rays that have passed through the sample cell.

FIG. 4 illustrates a typical configuration of a conventional infrared gas analyzer. The infrared analyzer 100 shown in FIG. 4 includes an infrared source 101, a reflecting mirror 102, an infrared lens 103, a sample cell 104, a chopper wheel 105, an infrared sensor 106 and a CD motor 107.
The sample gas in the sample cell 104 is irradiated with infrared rays from the above, and the transmitted light is chopped by the chopper wheel 105 and detected by the infrared sensor 106.

[0005]

In the conventional NDIR configuration, each component of the sample gas absorbs infrared light over a wide range of the infrared wavelength range of the light source. For this reason, the sample gas is thermally excited, and particularly when it contains a gas component having a high absorptivity, absorption and emission occur at the same time. There is a problem that the influence of the components and the concentration influence of the measured components themselves appear non-linearly. Further, there is a problem that a plurality of infrared detectors are required for measuring a plurality of components, and an amplifier and a data processing device are complicated.

In order to solve the problems of the conventional infrared gas analyzer, the present invention reduces the influence of components other than the target component in the measurement of a single component or a plurality of components, or the number of infrared detectors and related amplifiers. The objective is to construct a method that enables measurement of high-speed response with as little as possible.

[0007]

In order to achieve the above object, an infrared gas analyzer according to the present invention has a sample cell placed between an infrared light source and an infrared detector so that the sample absorbs light in the infrared region. In an infrared gas analyzer that measures gas components and concentrations by means of a multilayer bandpass filter located between the light source and the sample cell, multiple filters including the reference light filter are placed on the rotating body. The infrared light from the light source is intermittently passed through the sample cell by the rotating body including the filter, and the infrared light partially absorbed by the sample is received by the detector. The feature is that the gas component and the concentration are measured on the basis of the difference between the reference light and the light of the measurement band.

[0008]

In the infrared gas analyzer according to the present invention, the bandpass filter is operated in the optical path from the light source to the sample cell so that only the infrared ray in the specific relatively narrow wavelength region passes through the sample cell, and the bandpass filter is used. Are placed on the rotating body to simultaneously perform the chopper action of the light flux. Furthermore, an infrared detector with high sensitivity and quick response characteristics was used, and it was possible to increase the speed of the chopper at the same time. This enables a fast response. The same detector can be used to measure multiple components.

[0009]

Embodiments of the present invention will be described below with reference to FIGS. 1, 2 and 3. FIG. 1 is a structural diagram of an infrared gas analyzer according to an embodiment of the present invention. Infrared light emitted from the light source 11 and having a continuous spectrum with a wavelength of 2 to 10 μm is applied to the bandpass filters 15 and 16 as a light beam 14 at a substantially right angle by the reflecting mirror surface 12 and the condenser lens 13.
The bandpass filters 15 and 16 are attached to a plurality of windows provided on a circular plate 25 that rotates around a rotary shaft 22 supported by a bearing 23, and selectively pass only infrared rays in a specific wavelength band. Let The rotary shaft 22 is attached to the shaft attachment portion 26. A light-shielding mask 19 which is precisely manufactured is attached to the disc 25, and the light beam 14 can pass infrared rays of a specific wavelength band with a specific waveform change with time by the bandpass filters 15 and 16 and the light-shielding mask 19. It is like this. Almost coaxial with the light flux 14, the sample cell 31
Are arranged to form the sample chamber 32 inside, and the sample chamber 32
Infrared rays passing through the bandpass filter 15 and the light shielding mask 19 with infrared transmitting windows 35 and 36 placed in front of and behind are absorbed by the sample gas 30 in the sample chamber 32, attenuated, and reach the infrared detector 43. It is configured. The infrared detector 43 is provided with a case 42 and a detector window 45, and depending on the energy of the incident infrared ray and its wavelength range,
The output can be obtained as a current or voltage between the electrode terminals 46, 47.

The sample cell 31 is provided with passages 37 and 38 for gas inflow and outflow, and the sample gas 30 to be measured is
Can flow out of the passage 37 from the passage 37 via the sample chamber 32. When the bandpass filters 15 and 16 provided on the window of the rotating disk 25 for specific components and for the reference light are alternately arranged as shown in FIG. The output signal as in (a) is obtained from the detector. Further, in the example of FIG. 2B, a bandpass filter 15 for reference light and several types of component bandpass filters 16, 17 and 18 are sequentially mounted. Furthermore, FIG.
In the example of (c), two sets of optical systems are used for one rotating disk 25, and two sets of sample chambers 32 and 32 'and infrared detectors 43 and 43' are provided. 3B and 3C are signal outputs of the detector corresponding to FIGS. 2B and 2C.

A plurality of timing signal light transmission holes 51 and a plurality of timing light transmission holes 5 provided in the rotating disk 25 of FIG.
Reference numeral 2 is used for data processing of the signal output of the detector, and is for obtaining a timing signal by arranging an unillustrated photocoupler or photointerrupter, or an LED and a photo IC at appropriate positions. 3 (a), 3 (b)
This timing signal is also shown in FIG.

The signal outputs of the infrared detectors 32 and 32 'are
Normally, a signal which is appropriately amplified and is easily processed by a high-speed A / D converter can be processed by a calculator. In case of FIG. 3 (b) shown as, for example, signals S ₁ corresponding to the reference signal R and the components S _1, when there is a signal S _2, which corresponds to component S _2, 1 to 1 rotation time signal pulse Z The value of 10 to 50 .mu.s of the x signal at that time is based on the y signal pulse which is reset first, and the next x signal every 100 .mu.s is A / D.
About 10 to 20 signals are converted and integrated.

The integrated value is set as R, and the x signal is processed from the next y signal by using this as a timing signal, and the integrated value is set as S ₁ . Further, the x signal from the next y signal is similarly processed to obtain S ₂ . A calculation process for obtaining S / R is performed to obtain the measured value of each component. Then, for example, the relationship between x _{0 in} the case of a sample gas that does not include a measurement component generally called 0 (zero) gas and x _{c in} the case of a sample gas called a calibration gas that includes a measurement component with a known concentration. From this, the measured concentration can be obtained. That is, x ₀
Based on S ₁₀ / R in the case of and S _1c / R in the case of x _c ,
The value of S ₁ / R for the measured concentration is determined. Absorption of infrared rays by the concentration α and its gas component (S ₁₀ / RS)
_Since the relationship of ₁ / R) is not necessarily linear, a calibration relationship is usually established with known gases of several kinds of concentrations. Using this relationship, the concentration α can be calculated from (S ₁ / R).

The signal output method of the infrared detector as described above is not limited to the digital method, and analog calculation processing is possible.

[0015]

According to the present invention, with respect to a sample containing various components having absorption ability in the infrared region, one set or a small number of sets of optical systems can be used to measure the concentration of multi-component gas at a very high response speed. Can be measured accurately. Moreover, it is a structure that irradiates only a specific narrow wavelength band infrared ray that has passed through the bandpass filter to the measurement gas and absorbs a part of it, and suppresses the interference of other gas such as a component having a large absorptivity. be able to.

According to this type of infrared gas analyzer, it is possible to measure, for example, a single component such as CO ₂ concentration in exhaled breath by 10
It is possible to respond within ms. In addition, even if 3 components are measured simultaneously in automobile exhaust gas, 1 detector will
With a response speed of 0 ms, it is possible to measure without interference of other components.

As described above, not only can a large number of components and samples be measured with a small number of optical systems and detectors at a high response speed, but also infrared irradiation of the sample gas can reduce the band width and the total energy. It is possible to measure without causing mutual interference of absorption / emission.

On the other hand, in the embodiment, the case where the sample gas is introduced into the cell for measurement is shown, but it is also possible to directly measure the sample cell by providing an infrared window or the like in the gas passage.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a configuration of an infrared gas analyzer.

FIG. 2 is a front explanatory view of a rotating disc.

FIG. 3 is a graph showing an output waveform of an infrared detector.

FIG. 4 is a structural explanatory view showing a conventional infrared analyzer.

[Explanation of symbols]

 11 Light Source 12 Reflecting Mirror Surface 13 Condensing Lens 14 Luminous Flux 15 Bandpass Filter 16 Bandpass Filter 17 Bandpass Filter 18 Bandpass Filter 19 Shading Mask 22 Rotating Shaft 23 Bearing 25 Disc 26 Shaft Mounting Part 30 Sample Gas 31 Sample Cell 32, 32 'Sample chamber 35, 36 Infrared transmission window 37 Passage 38 Passage 42 Case 43, 43' Infrared detector 45 Detector window 46 Electrode terminal 47 Electrode terminal 51 Timing signal light transmission hole 52 Timing signal light transmission hole 100 Infrared analyzer 101 Infrared source 102 Reflector 103 Infrared lens 104 Sample cell 105 Chopper wheel 106 Infrared sensor 107 CD motor

Claims (3)

[Claims] 1. In an infrared gas analyzer in which a sample cell is placed between an infrared light source and an infrared detector to measure gas components and concentrations by the absorbance of the sample in the infrared region, between the light source and the sample cell. A multilayer bandpass filter is located in the multi-layer bandpass filter, and a plurality of this filter, including the reference light filter, are arranged on the rotating body, and infrared light from the light source is rotated by the rotating body including the filter in a specific wavelength range. Infrared light is intermittently passed through the sample cell, and the infrared light partially absorbed by the sample is received by the detector, and the gas component and concentration are measured based on the difference between the reference light and the light in the measurement band. Infrared gas analyzer. 2. The gas analyzer according to claim 1, wherein the multi-layer bandpass filter to be arranged on the rotating body comprises two types for reference light and a single component, or three or more types for a plurality of components. Infrared gas analyzer that measures the component and concentration of each component or multiple components with the same device. 3. The gas analyzer according to claim 1 or 2, wherein a plurality of infrared light paths are provided for a combination of the same rotor and a multilayer film bandpass filter, and a plurality of sample cells and a plurality of sample cells are provided. An infrared gas analyzer that measures a single component or multiple components simultaneously with the same device for multiple types of samples or multiple types of measurement ranges using an infrared detector.