JPH1090207A - Methane concentration measuring method and gas concentration measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable accurate measurement of methane concentration even if sundry gas exists. SOLUTION: This gas concentration measuring device is provided with a gas dilution device 2, which composes gas concentration in a detectable manner on the basis of variation of the resistance value of a gas detecting element 1 when gas subject to detection is made to come in contact with it and makes gas subject to detection come into contact with the gas detecting element 1 by air diluting so that resistance value variation of methane concentration equivalent to less than 1000ppm can be obtained when a discrimination mechanism 7a, which is for discriminating whether or not the resistance value variation of the gas detecting element 1 caused by contact with gas subject to detection is equivalent to 1000ppm or more by methane concentrate conversion, discriminates that the resistance value variation is equivalent to 1000ppm or more by methane concentration conversion and also provided with an arithmetic unit 7b which detects methane in the diluted gas subject to detection from the resistance value variation of the gas detecting element 1 on the basis of contact with the diluted gas subject to detection and converts it to methane concentration before dilution.

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 in which a gas to be detected is brought into contact with a gas detecting element and the gas concentration can be detected based on a change in the resistance value of the gas detecting element. The present invention relates to a methane gas concentration measuring method for detecting methane gas using the gas concentration measuring device.

[0002]

2. Description of the Related Art Conventionally, as this type of gas concentration measuring device, there has been known a device in which a gas to be detected in the atmosphere is simply suctioned, sampled, and detected by a gas detecting element. The methane gas concentration was measured using such a gas detection device. For example, first, when it is detected that a gas leak has occurred, the methane gas concentration is used to determine whether or not there is a safety problem. The need for accurate measurements arises.

[0003]

However, although a normal methane gas detecting element selectively detects methane gas, it has an output with respect to other flammable gas (hereinafter referred to as miscellaneous gas), In an atmosphere where is present in large quantities, despite the fact that methane gas is almost nonexistent,
In some cases, it was determined that methane gas was leaking. For this reason, for example, it may be determined that methane gas is leaking based on a large amount of ethanol gas, which is a typical example of miscellaneous gas, and erroneous detection of gas leak may hinder stable use of methane gas. It is thought that there is a case.

Accordingly, an object of the present invention is to provide a technique capable of accurately measuring the methane gas concentration even in the presence of miscellaneous gas in view of the above-mentioned drawbacks.

[0005]

Means for Solving the Problems The present inventors have proposed that a conventionally used gas detecting element has a methane gas concentration of 10%.
When trying to detect a gas to be detected having a concentration exceeding 00 ppm, miscellaneous gas contained in the gas to be detected is also detected at the same time, so that accurate gas concentration cannot be measured. It has been newly found that when detecting a gas having a concentration of, the miscellaneous gas contained in the detected gas is hardly detected, so that the gas concentration can be measured accurately.
The present invention has been made based on this new finding. [Structure 1] The characteristic means of the methane gas concentration measuring method of the present invention for achieving this object will be described with reference to FIG. 1. The gas detection element 1 is brought into contact with a gas to be detected. Using a gas concentration measuring device configured to be able to detect the gas concentration based on the change in the resistance value of the gas detection element, the change in the resistance value of the gas detection element due to the contact of the gas to be detected is equivalent to 1000 ppm or more in terms of methane gas concentration. To
The detected gas is diluted with air so as to obtain a resistance value change corresponding to a methane gas concentration corresponding to 1000 ppm or less and brought into contact with the gas detection element, and the gas detection element based on the contact of the diluted detected gas. It is to detect the methane gas in the diluted gas to be detected from the change in the resistance value of 1 and convert it to the methane gas concentration before dilution.

The drawings are merely used for reference, and the present invention is not limited to the drawings.

[Effects] That is, according to the above findings,
Since the miscellaneous gas is contained in a large amount in the detected gas atmosphere when the concentration exceeds 1000 ppm in terms of the methane gas concentration, the concentration of the miscellaneous gas is reduced to 1000 ppm or less. Is measured, the methane gas concentration can be measured almost without being affected by the miscellaneous gas. Here, the methane gas concentration conversion value is 100
If it is set to 0 ppm, 1000 ppm unless miscellaneous gas is present in a large amount relative to methane gas.
The methane gas concentration up to can be measured almost accurately. As a result, even if miscellaneous gas is mixed with low-concentration methane gas, the methane gas concentration can be measured accurately without being affected by the miscellaneous gas, and the methane gas concentration is erroneously detected. This has made it possible to prevent such inconveniences as to hinder the stable supply and use of gas.

[Structure 2] The characteristic structure of the methane gas concentration measuring apparatus of the present invention for achieving the above object will be described with reference to the drawings. The gas concentration is configured to be freely detectable based on the change in the resistance value of the gas detection element 1, and whether or not the change in the resistance value of the gas detection element 1 due to the contact of the gas to be detected corresponds to 1000 ppm or more in terms of methane gas concentration. When the discrimination mechanism 7a determines that the change in the resistance value corresponds to 1000 ppm or more in terms of methane gas concentration, the discrimination mechanism 7a discriminates the detected gas by 1000 p.
a gas diluting device 2 for contacting the gas detection element with an air dilution so as to obtain a resistance value change corresponding to a methane gas concentration equal to or less than pm, and the gas detection based on the contact of the diluted gas to be detected. The point is that an arithmetic unit 7b for detecting the methane gas in the diluted gas to be detected from the change in the resistance value of the element 1 and converting it into the methane gas concentration before dilution is provided.

The drawings are merely used for reference, and the present invention is not limited to the drawings.

[Effects] In other words, since the gas detection device is provided so as to be capable of detecting the gas to be detected by providing the gas detection element, first, the output by the gas to be detected can be obtained, and the discrimination mechanism is provided. Therefore, it is possible to determine whether or not the information on the gas concentration indicates that the change in the resistance value of the gas detection element exceeds an amount corresponding to 1000 ppm of the methane gas concentration. At this time, in order to perform the above gas detection method, if the result of the determination by the determination means recognizes that the concentration of the gas to be detected is 1000 ppm or more in terms of methane gas concentration, the gas to be detected is air-diluted by the dilution device. After dilution, the output from the detected gas is converted to methane gas concentration by 1
000 ppm or less. Note that the dilution ratio at this time can be appropriately selected according to the information input to the determination means. The previously obtained gas concentration output in terms of the methane gas concentration does not substantially include the output of the miscellaneous gas, so that it may be considered that the output is entirely methane gas. Therefore, if the gas concentration output diluted by the arithmetic unit is converted into a methane gas concentration, an accurate methane gas concentration can be obtained. Therefore, it is possible to provide a gas detection device that is unlikely to erroneously detect a methane gas leak or the like, and it is possible to easily and accurately perform stable gas supply and safety management.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the gas detection device of the present invention is provided with a gas detection element 1, and a flow control device including a dilution control mechanism 2 a for bringing a diluted gas to be detected into contact with the gas detection element 1. 2 and a suction pump 3 for sucking, through the gas detection element 1, the gas to be detected, the dilution of which is controlled by the flow control device 2. As shown in FIG. 2, the gas detection element 1
A power supply circuit 4 that is incorporated in the bridge circuit 1a and supplies power, an amplification circuit 5 that amplifies an output signal from the gas detection element 1, converts the signal into a methane gas concentration, and outputs the methane gas concentration to a display device 6. An arithmetic circuit 7 for determining whether the output information is equivalent to 1000 ppm or more in terms of methane gas concentration is provided, and an alarm circuit 9 for issuing an alarm such as a buzzer 8 when the concentration exceeds the allowable concentration of methane gas is provided. The dilution control mechanism 2a is controlled based on the determination result of the arithmetic circuit 7, and based on the determination result, the methane gas concentration can be displayed or output as an alarm. In the dilution control mechanism 2a, the arithmetic circuit 7 determines that the output information is 1 in terms of methane gas concentration.
When it is determined that the detected gas is equal to or more than 000 ppm, the detected gas is doubled and tripled so as to obtain a resistance value change corresponding to a methane gas concentration equivalent to 1000 ppm or less.
In order to sequentially dilute the air in the order of,.
A gas detection section 2b for introducing a gas to be detected and an air introduction section 2c for mixing dilution air are configured to be openable and closable.
When it is determined that the output information is equivalent to 1000 ppm or more in terms of methane gas concentration, the air is further diluted. When it is determined that the output information is equivalent to 1000 ppm or less in terms of methane gas concentration, the output information is output information that gives an accurate methane gas concentration. It is converted to a methane gas concentration as it is, and the converted output is output to the display device 6, and if the converted output exceeds the allowable concentration, an alarm output is issued to the alarm circuit 9; It is configured to issue an alarm such as a buzzer 8.

It should be noted that the arithmetic circuit shown in the above-described embodiment is defined as the discriminating mechanism 7a and the arithmetic unit 7b in the claims.
Both of these functions are combined, and a circuit or device having each function may be separately provided instead of such a form. In addition, a configuration that allows the gas to be detected to be diluted, like the flow rate adjusting device described in the above embodiment, is called a gas diluting device. In addition, regarding the dilution ratio, it is also possible to change the dilution ratio in a geometric series instead of adjusting the dilution ratio in an arithmetic series, and to set a target output after dilution in advance, The dilution ratio for obtaining the output can be used as the concentration output information output from the gas detection element. In this case, it is sufficient that a feedback circuit is provided between the flow rate adjusting device and the gas detection element so that the dilution rate can be output.

[0013]

The gas detection output characteristics of a general gas detection element will be described below. As shown in FIG. 3, the output characteristics of the methane gas detection element change logarithmically with respect to the concentration, but the output relating to the miscellaneous gas starts to increase gradually at a value exceeding 1000 ppm. The output for miscellaneous gas is 1000p
Even if it exceeds pm, it is extremely lower than the output of methane gas, and if the output from the gas detection element is subjected to dilution control so as to be 1000 ppm or less in terms of methane gas concentration, the output from the miscellaneous gas is hardly detected. That can be expected.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a gas concentration measuring device.

FIG. 2 is a diagram showing an assembled state of a gas detection element.

FIG. 3 is a characteristic diagram of a gas detection element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas detection element 2 Gas dilution device 7a Discrimination mechanism 7b Arithmetic unit

Claims (2)

[Claims] 1. A methane gas for detecting a methane gas by using a gas concentration measuring device in which a gas to be detected is brought into contact with a gas detection element and the gas concentration is freely detectable based on a change in the resistance value of the gas detection element. A concentration measuring method,
When the change in the resistance value of the gas detection element due to the contact of the gas to be detected is equivalent to 1000 ppm or more in terms of methane gas concentration, a change in the resistance value corresponding to the methane gas concentration of the gas to be detected is 1000 ppm or less is obtained. As described above, the air is diluted and brought into contact with the gas detection element, and from the change in the resistance value of the gas detection element based on the contact of the diluted detection gas, the methane gas in the diluted detection gas is detected, and the dilution is performed. A methane gas concentration measurement method that converts to the previous methane gas concentration. 2. A gas concentration measuring device comprising: a gas to be detected in contact with a gas detecting element; and a gas concentration detecting device configured to detect a gas concentration based on a change in resistance value of the gas detecting element. The discriminating mechanism for discriminating whether or not the resistance value change of the gas detecting element is equivalent to 1000 ppm or more in terms of methane gas concentration is provided.
The resistance value change is 1000 ppm in terms of methane gas concentration.
When it is determined that the above is the case, the detected gas is set to 1
Providing a gas diluting device that is air-diluted so as to obtain a resistance value change corresponding to a methane gas concentration equivalent to 000 ppm or less and brought into contact with the gas detection element, and the gas detection element based on the contact of the diluted gas to be detected. A methane gas concentration measuring device provided with an arithmetic unit for detecting a methane gas in a diluted gas to be detected from the change in the resistance value of the sample and converting the detected methane gas into a methane gas concentration before the dilution.