KR830000032B1 - Photoacoustic gas analyzer - Google Patents

Abstract

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Description

Photoacoustic gas analyzer

FIG. 1 is an explanatory view showing a first embodiment of the present invention. FIG.

FIG. 2 is an explanatory diagram of a second embodiment; FIG.

FIG. 3 is an explanatory diagram of a third embodiment; FIG.

4 is a cross-sectional view taken along the line IV-IV in Fig. 3;

FIG. 5 is an explanatory view of the operation of the apparatus shown in FIG. 3; FIG.

FIG. 6 is an explanatory diagram showing an example of a multi-component system. FIG.

The present invention relates to a photoacoustic analyzer using a blackbody radiation light source and an optoacoustic detector. More particularly, the present invention relates to a photoacoustic analyzer using a black body radiation source and an inexpensive gas analyzer capable of stably and precisely quantifying a specific trace gas, .

In the conventional photoacoustic analyzer, although a laser light source having a selectivity for an energy source is used, it has a problem that it is very expensive and the device itself becomes large.

An object of the present invention is to obtain an inexpensive and stable analyzing apparatus by using a black body radiation light source instead of a conventional laser light source and optically using a filter.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 shows a first embodiment of a photoacoustic gas analyzer according to the present invention, wherein (1) is a black body radiation light source, (2) is a photo interrupter (chopper), The multilayer film interference filter detector, and (5) a high impedance amplifier.

The infrared energy radiated from the black body radiation source 1 is caused to be intermittent light by the optical interrupter 2 and then sent to the filter 3 for positive and the infrared energy of the measured component details reaches the detector 4 .

The sample gas is now continuously or intermittently supplied through the capillary 7 in the gas inlet 6 of the detector 4 and circulated in the detector 4 to be introduced into the gas outlet 9 via the capillary 8. [ .

Assuming that a gas coinciding with the infrared spectrum of the measurement component band is contained in the measurement gas, this gas absorbs the infrared energy and raises the pressure in the detector 4. [

Now, if the light is interrupted at a proper cycle, the capacitor film 10 can be displaced at that period and taken out as a signal.

Also, it is not necessarily a condenser microphone type. For example, it may be a mass flow type.

Since the absorption of energy in the detector 4 is proportional to the concentration of the measurement gas, the concentration of the unknown gas in the sample gas can be quantified.

The change in the microphone capacity of the condenser membrane 10 is taken out as an electrical output by the amplifier 5 and rectified by the rectifier 30 before shaking the indicator 31. [

FIG. 2 shows a second embodiment of the inventive device and further enhances the device of the second embodiment.

In the apparatus of the first embodiment, when the infrared absorption band as the disturbance component exists in the vicinity of the absorption band of the measurement component or when the concentration of the measurement component is extremely low with respect to the concentration of the disturbance component, Can not be sufficiently removed.

Therefore, as in the second embodiment shown in Fig. 2, the light receiving chamber of the detector 4 is made to be a refractory type, and a gas filter 11 (which may be an absorbing solid filter) is sandwiched between these chambers It is installed.

In the second embodiment, the case where CO ₂ is present as an obstructing gas when measuring the trace CO concentration in the atmosphere will be described. The infrared energy emitted from the black body radiation source 1 is transmitted to the optical interrupter 2 to reach the detector 4 after passing through the solid multilayer interference filter 3 which transmits the infrared absorption band of CO after intermittent light of, for example, 10 Hz.

Now, assuming that both the compartments (a) and (b) in the detector 4 are filled with gas that does not absorb infrared rays, absorption of infrared energy does not occur in any of the compartments (a) and (b) , the pressure of the condenser microphone does not rise, and the film 10 of the condenser microphone does not displace.

Next, an atmosphere containing a trace amount of CO to which CO ₂ is introduced is introduced into both compartments (a) and (b).

In both compartments (a) and (b), absorption occurs as described below, and a film displacement proportional to the CO concentration is generated, so that the CO concentration can be accurately quantified without interfering with CO ₂ .

That is, the infrared energy incident on the compartment (a) is infrared energy of a certain band determined by the multilayer interference filter 3 having the center wavelength of about 4.6μ.

However, the infrared absorption band of the CO ₂ gas partially overlaps with the infrared absorption band of the CO gas and overlaps with a part of the transmission energy band of the filter 3.

Therefore, the infrared energy reached in the first compartment (a) is absorbed by the trace CO molecules and CO ₂ interfering molecules in the compartment, and the temperature of the room is raised.

Now, assuming that the energy due to the absorption is? Ia,

ΔIa = ΔICO + ΔCO ₂

In the gas filter 11, infrared energy of IO -? Ia, in which the infrared energy is I, is reached.

In the gas filter 11, the same CO gas as the measurement object is sealed at an appropriate concentration, where the important absorption band of CO is attenuated.

Let this be I ₁ .

The infrared energy of I ₁ reaches the compartment (b), absorbing the CO molecules in this compartment and their respective concentrations, and raising the temperature of this compartment.

Now the energy < RTI ID = 0.0 >

ΔIb = ΔI'CO + ΔI'CO ₂

Here, ΔICO ₂ and ΔI'CO ₂ can be set to ΔICO ₂ = ΔI'CO ₂ by empirically selecting the half width of the solid filter 3 and the CO concentration of the gas filter 11.

Since the difference in absorption energy between the two compartments (a) and (b), i.e., the pressure difference, displaces the condenser membrane 10,

ΔE = ΔIa-ΔIb

_{= ΔICO + ΔCO 2 - (ΔI'CO} + I'CO2)

=? ICO-? I'CO

Since? I'CO is absorption in the region where there is no CO main absorption band by the gas filter 1

ΔICO "ΔI'CO

And is proportional to the CO concentration, so that ΔE can correctly detect the signal of CO without interfering with CO ₂ .

Or less.

As in the second embodiment, the light-receiving chambers of the detectors are arranged in series to form a refractory type, and a gas filter or an absorption type solid filter having absorption equal to the measurement gas is inserted between these chambers, It is also possible to provide a highly accurate ultra-minute gas analyzer.

FIG. 3 shows a third embodiment of the present invention, which is intended to obtain an effect equivalent to that of the second embodiment by using the gas-correlated rotary filter 12. According to this method, many components can be measured I can do it.

In the third embodiment, a case where CO ₂ is present as an obstruction component when the trace CO concentration in the atmosphere is measured will be described.

3, the infrared energy reflected by the blackbody radiation source 1 reaches the detector 4 after passing through the gas-correlated rotation filter 12, past the solid multi-layer interference filter 3.

The filter cell 13 is filled with a gas which does not absorb infrared rays at all, and the filter cell 14 is filled with the measurement gas at an appropriate concentration.

The last infrared energy of the filter cell 13 is absorbed by CO molecules and CO ₂ molecules in the detector 4 and the temperature of this chamber is raised to displace the capacitor film 10.

Let A be the signal at this time.

Next, the infrared energy passing through the filter cell 14 is mainly absorbed by the CO ₂ molecule when it reaches the detector 4 because the CO ₂ absorption band is removed.

Let this signal be B.

As shown in FIG. 5, the signals B and A shown in the figure are alternately outputted at the cycles determined by the number of revolutions of the correlated rotary cell 12 at the amplifiers 5 and 16, The signals A and B are input to the respective hold amplifiers 18 and 19 by the synchronizing signal generated by the synchronizing signal generator 17 and the final signal output BA is obtained by the subtracter 20 .

Thus, it is possible to support the CO gas concentration without interference.

It is also possible to constitute a multi-component system by providing a plurality of gas cells corresponding to various gases in the rotating cell with the multilayer film interference filter as the window of the rotating cell.

The sixth turning those shown for an example, selsil 21 in the CO gas, N ₂ gas, selsil 23, CO ₂ gas, selsil 24 is provided with N ₂ gas is filled respectively in selsil 22 and A CO multilayer interference filter is provided in the windows of the cell chambers 21 and 22 and a CO ₂ multilayer interference filter is provided in the windows of the cell chambers 23 and 24.

INDUSTRIAL APPLICABILITY As described above, the apparatus of the present invention uses a black body radiation light source and further uses a solid multilayer interference filter of +, so that a gas analyzer which is inexpensive and stable can be obtained.

In particular, it is possible to provide a gas analyzer which does not cause zero drift.

Claims (1)

1. A photoacoustic gas analyzer having a light source, an optical interrupter interrupting light from the light source, and a photoacoustic detector irradiated with intermittent light interrupted by the interrupter, wherein the solid-state multilayer interference filter Wherein the black body radiation source is a black body radiation source.

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