JP2002174626A - Sampling type gas detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device capable of reducing a noise without requiring high performance from a pump. SOLUTION: This device comprises a photoacoustic gas sensor, a sampling pipe for carrying air of an area under surveillance to the photoacoustic gas sensor, the suction pump for introducing the air to the photoacoustic gas sensor via the sampling pipe, and a silencing chamber positioned between the photoacoustic gas sensor and the suction pump. By this, even without requiring an extremely low noise and vibration from the suction pump, the silencing chamber can reduce noise and gas can be detected efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sampling type gas detector.

[0002]

2. Description of the Related Art Conventionally, a gas detection device using a sampling tube uses a suction pump to convey air to a gas sensor. As such a pump, a pump that operates quietly with a stable suction amount is used, but if such performance is required, an expensive pump is naturally used.

[0003]

If a photoacoustic gas sensor is used as such a gas sensor, the detection mechanism is the same as that of a so-called microphone, so that it is easy to pick up noise. Very few are required.
As a result, the whole system becomes expensive.

Accordingly, an object of the present invention is to provide a device capable of reducing noise without requiring high performance of a pump.

[0005]

SUMMARY OF THE INVENTION The present invention provides a photoacoustic gas sensor, a sampling pipe for conveying air in a monitored area to the photoacoustic gas sensor, and a photoacoustic gas sensor via the sampling pipe. It is characterized by comprising a suction pump for introducing the air, and a muffling chamber arranged between the photoacoustic gas sensor and the suction pump.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. FIG. 1 is a schematic diagram showing an embodiment utilizing the present invention.

In the figure, reference numeral 1 denotes a photoacoustic gas sensor;
Is a diaphragm type pump as an example of a suction pump;
Is a silencing chamber, which is connected from the pump 2 to the silencing chamber 3 by a suction pipe 7 and from the silencing chamber 3 to the photoacoustic gas sensor 1 by an inlet pipe 8. And
The sampling tube sucked by the pump 2 and not shown in detail will be connected from the direction of the arrow shown on the pump 2.

In such a configuration, the gas sensor 1 is
As a detection principle, when a target gas is irradiated with infrared rays, absorption occurs at a specific wavelength (for example, about 4.3 micrometers for CO2), the internal energy of gas molecules increases, and the pressure is measured as a pressure rise in the container. Although not shown in detail, a specific configuration is provided in which a detection chamber is provided, an infrared light source is turned on and off at a predetermined cycle, and a minute pressure change is measured by a microphone (microphone). The output of this microphone is proportional to the gas concentration. The detection principle of such a photoacoustic gas sensor is superior in selectivity as compared with other fixed electrolyte systems and light wave interference systems.

Further, the diaphragm type pump 2 has a feature that the exhaust pressure is large, and a large exhaust pressure can be obtained though it is compact and inexpensive. However, on the other hand, the exhaust gas pulsates, and when this is combined with the photoacoustic gas sensor 1, a large noise output is given to the gas sensor 1 including the vibration by the pump 2.

On the other hand, in this embodiment, a silencing chamber 3 is arranged between the gas sensor 1 and the pump 2. The silencing chamber 3 has a housing made of an elastic material such as rubber and has a sponge S inside. Thus, in addition to the soundproofing properties of the sponge S itself, the elasticity of the rubber silencer 3 housing is received as volume expansion of energy due to pressure loss generated when air passes through the sponge S. As a result, the pulsating air that has flowed in can be smoothed, and vibration and noise can be absorbed to reduce the noise output.

The silencer 3 has three rooms 4,
The structure is divided into 5 and 6, and the air passes through the sponge S in the sound deadening chamber 3 so as to increase the distance to avoid pressure vibration resonance. That is, the air from the suction pipe 7 flows into the inflow ports 9, 1,
From 0, they are introduced into the rooms 4, 6 on both sides and then mixed again in the central room 5. At this time, since the air introduced from the openings 11 and 12 has different paths, the air is canceled by the phase difference of the pressure vibration. As a result, the effect of the muffling room 3 can be sufficiently obtained without dividing the room into large rooms, and the housing can be made small, so that there is no problem in responsiveness in terms of capacity.

Next, the results of the detection output according to this embodiment are shown in the graph of FIG.

In FIG. 2, the vertical axis represents the carbon dioxide concentration (p
pm), and the horizontal axis is time (seconds). Then, regarding the detected values in the graph, A is the output change according to this embodiment, B is the output change when the sound deadening room 3 of this embodiment is configured as one room, and C is the sound deadening room 3. This is the output when the pump 2 is directly connected to the gas sensor 1 without using it. Then, in the flow on the horizontal axis, the output starts to be taken from the time of power-on, and after 100 seconds, the pump 2 is turned on to start suction, and after 200 seconds, the injection of 1500 ppm of carbon dioxide is started.

From this result, in the case of the direct connection at C, since the pump 2 is turned on, it is largely shaken off by the noise at the same time as the pump 2 is turned on, and the measurement becomes impossible. In contrast, A, B
In the case of using the muffling room 3 in the above, slight noise is recognized, but the measurement is sufficiently possible. In the case of the three muffling rooms 3 in A, the noise is almost halved compared to B. ing. As for the rise of the output at the time of carbon dioxide injection, it is shown that the response is better in the case of the three silence rooms 3 in A than in the case of the single silence room B.

As described above, when the pump 2 is connected to the photoacoustic gas sensor 1 and used, the muffler chamber 3 is arranged between the pumps 2 to enable stable gas detection.
Can be used in one room instead of three.

Further, in this embodiment, air is flowed from the sampling pipe (not shown in detail) in a direction in which the air is exhausted through the pump 2, the silencer 3, and the gas sensor 1. 1. The present invention is also applicable to a case where the gas flows into the pump 2 via the sound deadening chamber 3. The direction of such an airflow differs depending on the gas to be detected, and when targeting carbon dioxide, the direction of the airflow may be in any direction without considering the adsorption action by the sound deadening chamber 3. However, in the case of the type of gas adsorbed when using the sponge S, it is necessary to arrange the devices in consideration of this point.

Based on the above embodiments, the present invention provides a photoacoustic gas sensor, a sampling pipe for conveying air in a monitored area to the photoacoustic gas sensor, and A suction pump for introducing the air into the photoacoustic gas sensor, and a muffling chamber disposed between the photoacoustic gas sensor and the suction pump, wherein the suction pump has very little noise and vibration. , The noise reduction chamber can reduce noise and efficiently detect gas.

The sound deadening chamber has a sponge inside, and the sound deadening chamber is made of a material having a resilient housing, so that the air passes through the sponge in addition to the soundproofing properties of the sponge itself. The energy due to the pressure loss generated at this time can be received as volume expansion by the elasticity of the rubber silencing chamber housing. As a result, the pulsating air that has flowed in can be smoothed, and vibration and noise can be absorbed to reduce the noise output.

Further, the sound deadening room is divided into a plurality of rooms, and the distance that air passes through a sponge in the sound deadening room is increased.
The resonance of the pressure vibration can be avoided, the operation of the silencing chamber can be sufficiently obtained without using a large room, and the pump can be reduced in size, so that the response is not affected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a gas detection device according to one embodiment of the present invention.

FIG. 2 is a graph showing a change in detection output by two other examples of the gas detection device of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas sensor 2 Pump 3 Silence room

Claims (4)

[Claims] 1. A photoacoustic gas sensor, a sampling pipe for conveying air in a monitored area to the photoacoustic gas sensor, and a suction for introducing the air to the photoacoustic gas sensor via the sampling pipe. A sampling type gas detection device, comprising: a pump; and a muffling chamber arranged between the photoacoustic gas sensor and the suction pump. 2. The sampling type gas detector according to claim 1, wherein the muffling chamber has a sponge inside. 3. The sampling type gas detecting device according to claim 1, wherein the silencing chamber has a housing formed of a material having elasticity. 4. The sampling type gas detector according to claim 1, wherein the muffling room is divided into a plurality of rooms.