JPH1090128A - Gas concentration measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas concentration measuring instrument which can highly accurately measure the concentration of a gas. SOLUTION: A gas concentration measuring instrument is provided with a gas sensor 1 having a gas detecting property, a gas leading passage 2 for leading a gas to be detected to the sensor 1, and a ventilator 3 which leads the gas to be detected to the passage 2. In addition, the instrument is provided with a setting switching section A which sets the aerating speed of the ventilator 3 to the passage 2 at a high value when the concentration of the gas to be detected is high and to a small value when the concentration of the gas is low.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas concentration measuring device.

[0002]

2. Description of the Related Art Conventionally, as a gas concentration measuring device of this type, a gas detecting device is simply provided with a gas ventilation passage for flowing a gas to be detected, and a ventilation device is provided to constitute the gas concentration measuring device. Things are known. That is, when the outside air containing the gas to be detected is guided to the gas detection element by the ventilation device, the gas to be detected comes into contact with the gas detection element and is detected. An output based on the concentration of
The configuration is such that the concentration of the detected gas can be known.

[0003]

There are two types of cases where it is necessary to know the concentration of the gas to be detected by a gas concentration measuring device. In other words, in the case of <1> detection of the presence or absence of gas leakage, it is necessary to know the approximate gas concentration quickly rather than obtaining the accurate gas concentration. This is the case where it is necessary to accurately determine the concentration of even a small gas in the case where it must be found accurately.

However, in the case described above, in order to cope with the purpose of the above <1>, it is necessary to perform a large amount of ventilation to a highly responsive gas detection element to enable quick judgment. On the other hand, in order to respond to the purpose of <2>, for a gas detection element having high output stability,
There is a current situation in which it is required to stably supply outside air containing the gas to be detected from the atmosphere in which the concentration of the gas to be detected is to be obtained. Although the performance of the gas detection element has been improved in recent years, if the gas concentration measuring device is used for both of the above purposes, and if it is attempted to respond to the purpose of <1> with high performance, the <2 If stable configuration was not obtained for the purpose of <2> and a configuration suitable for the purpose of <2> was adopted, the situation had to be such that it could not be used for the purpose of <1>.

Accordingly, it is an object of the present invention to provide a gas concentration measuring device capable of measuring gas concentration with high performance irrespective of the purpose of measuring gas concentration in view of the above-mentioned circumstances.

[0006]

According to the present invention, an accurate concentration output is obtained when a conventional gas concentration measuring apparatus suitable for the purpose <1> is used for the purpose <2>. What is not possible is that a large amount of atmospheric gas containing the gas to be detected is supplied to the gas sensing element, so the gas concentration must be measured with a large amount of air mixed in from around the atmosphere of the gas to be detected. Therefore, instead of measuring the concentration of locally existing gas, the focus is on the fact that the gas concentration in a wide range of atmospheres is averaged and found, The characteristic configuration of the gas concentration measuring apparatus of the present invention for achieving the above object will be described with reference to FIG. 1. In this case, a gas detection element 1 having gas detection characteristics is provided, and the gas detection element 1 is provided on the gas detection element 1. Guide the gas channel And a ventilation device 3 for guiding the gas to be detected to the gas passage 2 is provided. When the concentration of the gas to be detected is high, the ventilation speed of the gas passage 2 by the ventilation device 3 is set to be high. In addition, a setting switching unit A for setting the ventilation speed of the ventilation device 3 to a low value when the concentration of the gas to be detected is low is provided. More specifically, the gas passage 2 is provided with a bypass 21, and the gas detecting element 1 is provided in the bypass 21.
And a flow control mechanism A for maintaining a constant flow rate to the bypass passage 21 regardless of the flow rate to the gas passage 2. A flow path switching valve 4 is provided in the gas conducting pipe on the downstream side of the gas inflow side end 2a of the bypass passage 21 so as to be capable of introducing and switching the gas to be detected and the outside air not containing the gas to be detected. The control mechanism A is configured.

FIG. 1 is used merely for reference, and the present invention is not limited to FIG.

[Effects] That is, a ventilation device for guiding the gas to be detected is provided in the gas passage, and when the concentration of the gas to be detected is high, the ventilation speed of the gas through the gas passage by the ventilation device is set to be large. At the same time, when the concentration of the gas to be detected is low, the ventilation speed by the ventilation device is set to be small. By ventilating the outside air, quick gas detection can be performed, and even if the concentration of the gas to be detected is low, the concentration of the gas to be detected can be obtained by ventilation in accordance with the low concentration. At this time,
When detecting a low concentration, there is a possibility that the responsiveness may be lower than when detecting a high concentration, but in such a case, generally a high responsiveness is rarely required,
For example, considering gas leak detection, etc., gas detection does not become a dangerous situation such as poisoning due to gas leak, but rather, it becomes necessary to detect gas presence and simultaneously measure concentration. Many. Therefore, when the concentration of the gas to be detected is low, the object of <1> can be achieved and the object of <2> can be achieved at the same time. Conversely, when measuring a high-concentration gas to be detected for the purpose of <2>, accurate concentration measurement is not likely to be required if rapid concentration measurement is possible. Even if the concentration is diluted, a large error hardly occurs in the measured concentration, so that an adverse effect can be obtained as an accurate concentration measurement result.

Therefore, it has become possible to provide a gas concentration measuring device which can exhibit high performance for any of the two purposes, even if it is used for the two purposes.

Further, the gas passage is constituted by providing a bypass in the gas passage, and a gas detecting element is provided in the bypass, so that the gas passage to the bypass is independent of the amount of air flowing into the gas passage. If a flow control mechanism for maintaining a constant air flow rate is provided, the gas concentration in contact with the gas detection element is constant, so that the temperature control of the gas detection element can be easily performed. Can measure. Further, a flow path switching valve is provided in the gas conducting pipe on the downstream side of the gas inflow side end of the bypass path,
If a gas to be detected and external air not containing the gas to be detected are provided so as to be switchable and a flow rate control mechanism is configured, the gas conducting pipe may be maintained at a constant flow rate by a ventilation device (for example, a gas suction pump may be used). In the case where the gas suction pump is provided and the gas suction pump is operated in a steady state, the flow rate to the bypass pipe can be kept constant while the gas suction pump is constantly operated, and the flow rate of the gas flowing through the gas passage can be adjusted. For example, when the gas passage 2 is divided into four parts to form first to fourth passages 21 to 24, the gas detection path is provided as a bypass pipe and a gas detection element is provided. If the three-way valve 4 is provided as a flow path switching valve in the second to fourth passages 22 to 24, all the three-way valves 4
By switching to the side, 25% of the gas sucked by the ventilation device 3 is detected through the first passage 21 and is detected by the gas detecting element 1, and the other 75%
Can be outside air containing no gas to be detected, the amount of gas sucked from the gas inlet 2a can be limited to 25% of the gas suction capacity of the ventilation device 3, and the gas concentration can be adjusted with high sensitivity. It can be measured (see FIG. 2). However, of the three-way valve 4, the one in the second passage 22 is switched to the gas introduction part side of the detected gas, and
3. If the fourth passage 24 is switched to the air passage 6 side, 25% of the gas sucked by the ventilation device 3
Is a gas to be detected which is sucked through the first passage 21 and is detected by the gas detecting element 1, 25% is a gas to be detected which is sucked through the second passage but not detected by the gas detecting element 1, 50% Can be the outside air that does not contain the gas to be detected, and the amount of gas sucked from the gas inlet 2a can be limited to 50% of the gas suction capacity of the ventilation device 3 (see FIG. 3). Similarly, 25% of the gas sucked by the ventilation device 3 is the gas to be detected which is sucked through the first passage 21 and detected by the gas detecting element 1, and 50%
Is a gas to be detected which is sucked through the second and third passages 22 and 23 but not detected by the gas detecting element 1, 25%
Can be the outside air that does not contain the gas to be detected, and the amount of gas sucked from the gas introduction portion 2a is
Can be limited to 75% of the gas suction capacity (see FIG. 4). Finally, by switching all the three-way valves 4 to the gas introduction unit 6 side, 25% of the gas sucked by the ventilation device 3 can be obtained. % Of the gas to be detected which is sucked through the first passage 21 and detected by the gas detection element 1, and the other 75% is sucked through the second to fourth passages by the gas detection element 1. A gas that is not detected can be used as a gas to be detected, and the amount of gas suctioned from the gas introduction unit 2a can be used for suctioning the gas to be detected by setting the gas suction capacity of the ventilation device 3 to 100%. (See FIG. 5). That is, since the gas to be detected having a ventilation amount of 25% of the gas suction capacity of the ventilation device 3 always flows into the first passage 21 constituting the bypass pipe, the gas can be detected in a state where the gas detection conditions are stable. The gas introduction section 2a
Can be changed in four stages.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the gas concentration measuring device of the present invention comprises a gas detecting element 1 having gas detecting characteristics.
And a gas conducting path 2 for guiding the gas to be detected to the gas detecting element 1, and a gas suction pump 3 for guiding the gas to be detected to the gas conducting path 2. The gas passage 2 is divided into four passages, the first passage 21 of which is bypassed, and the gas passage 2 is formed as a bypass passage in which the gas detection element 1 is provided. Further, a three-way valve 4 is provided in the other second to fourth passages 22 to 24, a switching control device 5 for switching the flow path of the three-way valve 4 is provided, and an air introduction path 6 is connected to introduce air. It is configured to be able to switch between introduction of outside air containing the gas to be detected. As a result, the gas sucked by the gas suction pump 3 is obtained by mixing the gas containing the gas to be detected from the gas inlet of the gas passage with the external air at an arbitrary ratio of 25%. Become. Here, the gas flowing into the bypass 21 is always the outside air containing the gas to be detected, and is set to 25% of the gas suction amount of the gas suction pump 3. Here, the gas introduced from the gas introduction unit 2a is only the gas containing the gas to be detected out of the gas sucked by the gas suction pump 3; By switching, the amount of gas introduced from the gas introduction unit 2a is changed to configure the setting switching unit A that switches the setting of the ventilation speed. By switching the three-way valve 4 as shown in FIGS.
%, 75%, and 100%. The gas detection element 1 has a gas detection characteristic for methane gas, is provided with a gas detection circuit 7 that generates a signal based on gas detection, a power supply circuit 8 that supplies power to the gas detection circuit 7, and a generated signal. Output circuit 9 for outputting as a gas concentration information
Is provided so that the obtained gas concentration information can be output to the switching control device 5. The gas conducting path 2 is provided with a filter 2b for preventing a situation where dust components come into contact with the gas detecting element 1 and the sensitivity is lowered.

When the above-mentioned gas concentration measuring device is used, when the concentration of the gas to be detected is high from the gas concentration information, the ventilation speed to the gas conducting path 2 is set to be large, and the concentration of the gas to be detected is increased. The switching control device 5 is set and controlled so as to set the ventilation speed to a low value when the speed is low.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a gas concentration measuring device according to an embodiment.

FIG. 2 is a diagram showing a usage form of a gas concentration measuring device.

FIG. 3 is a diagram showing a usage form of a gas concentration measuring device.

FIG. 4 is a diagram showing a use form of the gas concentration measuring device.

FIG. 5 is a diagram showing a use form of the gas concentration measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas detection element 2 Gas conduction path 3 Ventilation device

Claims (3)

[Claims] A gas detection element having gas detection characteristics, a gas conduction path for guiding a gas to be detected provided in the gas detection element, and a ventilation device for guiding the gas to be detected provided in the gas conduction path; A setting switching unit that sets a high ventilation speed of the ventilation device to the gas passage when the gas concentration is high, and sets a low ventilation speed by the ventilation device when the concentration of the gas to be detected is low. Gas concentration measuring device provided with. 2. The gas conducting path is configured by providing a bypass in a gas conducting pipe, and a gas detecting element is provided in the bypass, so that the gas conducting path to the bypass is independent of the amount of ventilation to the gas conducting pipe. 2. The gas concentration measuring device according to claim 1, further comprising a flow control mechanism for maintaining a constant amount of ventilation. 3. A flow path switching valve is provided in the gas conduit at a downstream side of a gas inflow side end of the bypass path, and a gas to be detected and outside air containing no gas to be detected are provided so as to be switchable. And a flow control mechanism.
The gas concentration measuring device according to item 1.