JP4084344B2 - Portable flammable gas concentration measuring device - Google Patents

Description

  The present invention relates to a portable combustible gas concentration measuring device, and more particularly to a portable combustible gas concentration measuring device suitable for measuring the concentration of combustible gas in a predetermined region.

  In the periodic inspection of equipment that burns gas or oil as fuel, the concentration of carbon monoxide gas (hereinafter referred to as CO gas) in the exhaust gas of the gas equipment is checked to detect the incomplete combustion state at an early stage. . For example, if CO gas of a predetermined concentration or more is detected even in a part of the exhaust port, it may be considered that an incomplete combustion state has occurred in the combustion apparatus of the gas equipment, and a detailed inspection may be requested. Done. In general, in combustion equipment, before the entire combustion becomes defective, a defective combustion part occurs only on a part of the combustion surface. Therefore, an intake pipe for measuring the gas concentration is inserted into the exhaust port to measure the gas concentration. The presence of exhaust with a high gas concentration is checked. If a high CO gas concentration is detected even in a part of the exhaust port, it is considered as a sign that the entire combustor is in a bad state.

  The fossil fuel combustion exhaust gas includes hydrogen gas, carbon dioxide gas, and the like in addition to the CO gas. The CO gas and the hydrogen gas are combustible gases that burn when oxygen is supplied. Therefore, in order to selectively measure CO gas, a catalytic combustion type gas sensor has been proposed. For example, as shown in Patent Document 1. The catalytic combustion type gas sensor described in Patent Document 1 is formed by forming a carrier made of alumina on a metal coil by electrodeposition, and forming a catalyst such as platinum on the surface thereof, and allowing a constant current to flow through the coil. By heating the alumina carrier, only the CO gas in the exhaust gas is combusted through the catalyst, and the coil resistance value is detected by the combustion. The CO gas concentration is detected by utilizing the fact that the CO gas concentration and the increase in the resistance value of the coil due to combustion have a predetermined proportional relationship.

Further, the inventors of the present invention increased the catalytic combustion region and detected in a high concentration region by thinly forming an alumina support having a large number of holes and mixed with a catalyst on a metal coil by a certain method. The heat capacity was reduced to expand the detectable range in the low-concentration region, the carrier surface temperature variation was reduced, the selectivity for the type of flammable gas was improved, and the response speed was increased by reducing the heat capacity. A catalytic combustion type gas sensor was proposed. For example, it is described in Patent Document 2.
JP 2003-121402 A (published April 23, 2003) Japanese Patent Application No. 2004-137293 (filed on May 6, 2004)

  The above-mentioned contact combustion type gas sensor can widen the detectable concentration range in comparison with the semiconductor type gas sensor, for example, in the detection of CO gas concentration, and can be miniaturized. It can be applied to a concentration detection device. In order to make it portable, it is necessary to reduce the size by limiting the necessary hardware as much as possible. However, even if the hardware is limited, it is desirable to devise so that a state in which the CO concentration of the exhaust gas of the combustion equipment is partially increased can be reliably detected.

  Therefore, an object of the present invention is to provide a portable combustible gas concentration measuring device that can reliably detect the maximum gas concentration.

  In order to achieve the above object, an aspect of the present invention provides a gas suction means for sucking combustible gas, a gas sensor for detecting a gas concentration of the sucked combustible gas, and displaying the detected gas concentration. In the normal mode, the maximum gas concentration value of the gas concentration detected by the gas sensor detected by the gas sensor is displayed on the display means, and instantaneously responds to the instantaneous value display command. Control means for storing the maximum gas concentration value while displaying the gas concentration value on the display means, and returning to the normal mode in response to the end of the instantaneous value display command. It is a property gas concentration measuring device.

  In the above aspect, in a preferred embodiment, the gas sensor is a contact combustion type gas sensor that detects a gas concentration via a temperature at which inhaled combustible gas comes into contact and burns.

  In the above aspect, in a preferred embodiment, in response to a zero adjustment command, the control means resets the maximum gas concentration value when the instantaneous value is less than a predetermined reference concentration and performs zero point calibration of the gas sensor. And an error state is set when the instantaneous value is equal to or higher than a predetermined reference density.

  According to the above aspect of the present invention, when a combustible gas concentration distribution in a predetermined area such as an exhaust port is checked using a gas sensor having a quick response, an operator carrying the measuring device performs a partial operation in the predetermined area. Therefore, it is possible to easily and reliably detect a gas concentration that is high. The operator can detect the gas concentration at each position in the predetermined region as an instantaneous value by issuing an instantaneous value display command. When the gas sensor is a contact combustion type gas sensor, its responsiveness is fast, so it is possible to instantaneously detect a partially high gas concentration, and the instantaneous value is high-speed according to the intake position of the gas to be measured. Even if it changes, the maximum gas concentration in the predetermined region can be reliably detected. If a zero adjustment command is erroneously issued, the zero point calibration of the gas sensor in the wrong state can be avoided by setting the error state without performing the zero point calibration.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the matters described in the claims and equivalents thereof.

  FIG. 1 is a configuration diagram of a portable combustible gas concentration measuring apparatus according to the present embodiment. The main body 30 of the measuring device has a size and weight that can be carried. In the drawing, the appearance of the apparatus main body 30 is shown on the lower side 32A from the broken line of the main body 30, and the internal configuration of the apparatus main body 30 is shown on the upper side 32B from the broken line.

  First, a configuration for measuring gas concentration will be described. A gas intake pipe 22 for introducing a gas to be measured is provided at the upper left of the main body 30. The gas intake pipe 22 is connected to an intake pipe or tube of a certain length (not shown), and the other end of the intake pipe or tube is moved by an exhaust port of a combustion device and the gas to be measured is sucked therefrom. . In addition, an air intake pipe 24 is provided at the upper left of the main body 30. The air intake pipe 24 joins the gas intake pipe 22 by a Venturi pipe structure to form a mixing unit 22A. That is, the gas flow of the gas to be measured is formed by sucking the gas by the intake pump 29 provided on the downstream side of the gas flow, and air is mixed with the gas to be measured based on the gas flow. By allowing air to be mixed, the gas to be measured can be completely burned on the sensor surface even if oxygen shortage occurs in the gas to be measured, and measurement up to a high gas concentration can be made possible.

  The gas to be measured mixed in the mixing unit 22 </ b> A flows through the pipe 26 and the pipe 26 </ b> A having a larger cross-sectional area, and is supplied to the gas sensor 21. The gas flow to be measured that has flowed into the pipe 26 </ b> A having a large cross-sectional area has a low flow rate and is supplied to the gas sensor 21 at a low flow rate. An intake pump 29 is provided on the downstream side of the gas sensor 21, and exhaust of the pump is performed from the exhaust pipe 27.

  On the other hand, a single display means 34, an instantaneous value command button 36, a zero adjustment command button 38, and a power switch 40 are provided on the surface of the measurement apparatus main body 30. As will be described later, when the power switch 40 is turned on, the gas sensor detects the measured gas concentration at predetermined sampling time intervals, and the maximum gas concentration value among the continuously detected gas concentrations is displayed on the display means 34. The This is the normal display mode. When the instantaneous value button 36 is kept pressed, the instantaneous value of the gas concentration is displayed on the display means 34. When the pressing of the instantaneous value button 36 is stopped, the display means 34 returns to the normal display mode of the maximum gas concentration value. . Further, by pressing the zero adjustment command button 38, a series of gas concentration measurement is reset, and the zero point calibration of the gas sensor is performed. However, if the zero adjustment command button 38 is accidentally pressed during gas concentration measurement, an error display is displayed on the display means 34 or an error lamp (not shown) if the instantaneous value of the gas concentration being measured is equal to or greater than a predetermined reference concentration. Etc. If the instantaneous value is less than the reference concentration, the series of measured gas concentration values are cleared and the zero point calibration of the gas sensor is performed.

  2 and 3 are diagrams showing the configuration of the catalytic combustion type gas sensor in the present embodiment. In FIG. 2, the detection element of a gas sensor and its circuit structure are shown. As shown in FIG. 2 (a), the sensing element of the gas sensor in the present embodiment thinly attaches an alumina carrier 14 mixed with a catalyst to a coil wire 12 made of platinum wire or nickel wire by an electrodeposition method, and fires. As a result, a plurality of through holes 19 are formed in the carrier 14. By attaching the alumina carrier 14 thinly, a cylindrical alumina carrier 14 is formed with respect to the coil wire 12. The carrier is mixed with a catalyst 16 such as platinum or palladium for catalytic combustion of CO gas, and a large number of through holes 19 are formed. In addition to the surface of the carrier 14, the catalyst in the through holes 19 also contacts the gas to be measured. This contributes to complete combustion of the gas to be measured. The above catalytic combustion type gas sensor is described in detail in the above-mentioned Patent Document 2.

  In this way, the sensing element of the gas sensor has a large number of through holes 19 in a state where the carrier is mixed with the catalyst, and is formed in a thin film shape, so that the catalytic combustion region by the catalyst increases and the high concentration region is detected. By expanding the range and making it porous, the heat capacity is lowered and the detection range in the low concentration region is also widened, and the variation in the carrier surface temperature is reduced by the reduction in the heat capacity, thereby improving the gas selectivity.

  FIG. 2B shows the configuration of the detection circuit, and a bridge circuit is configured by the detection element E1 in which the gas to be measured contacts and burns, the reference element E2 for temperature compensation, and the resistors R1 and R2. The reference element E2 for temperature compensation has the same configuration as that shown in FIG. 2A, but does not contain a catalyst and does not burn even when the gas to be measured comes into contact. In the bridge circuit, power is applied to the series circuit of the sensing element E1 and the reference element E2 and the series circuit of the resistors R1 and R2, and the coils of the sensing element E1 and the reference element E2 are heated, and combustion of the detected gas is induced. The Then, it is detected as a voltage value from the sensor output to which the nodes A and B are connected that the CO gas as the gas to be measured is combusted in the sensing element E1 and the coil wire has a high resistance value due to the temperature rise. The reference element E2 is for compensating when the resistance of the coil wire is increased due to an increase in the environmental temperature.

  When the gas concentration to be measured is increased by the bridge circuit, combustion in the sensing element E1 becomes active, and the resistance of the coil wire increases due to the temperature rise. As a result, the voltage value of the node A increases. On the other hand, when the gas concentration to be measured decreases, the resistance of the coil wire decreases, and the voltage value at node A decreases. Since the measured gas concentration and the voltage value are in a proportional relationship, the measured gas concentration can be detected from the voltage value.

  FIG. 3 shows an internal configuration of the gas sensor 21 shown in FIG. The pipe 26A is connected to the inlet P1, and the outlet P2 is connected to the intake pump 29. And the conduit | pipe 211 has the conduit | pipe part 211A through which the to-be-measured gas which flows in from the inflow port P1 and is discharged | emitted from the discharge port P2 passes, and the conduit | pipe part 211B in which the detection element 213 and the reference element 212 are accommodated, A metal mesh plate 214 is provided between them. The reference element 212 is disposed upstream of the detection element 213 in the gas flow, and a partition wall 216 for blocking radiant heat is formed between the reference element 212 and the reference element 212 and the detection element 213 each have a mesh-like through hole. Covered with a cover 218.

  The gas to be measured is introduced from the inflow port P1, and is decelerated by the conduit portion 211A having a large cross-sectional area. Further, the gas to be measured that has flowed into the conduit portion 211A is diffused through the metal mesh plate 214 to the conduit portion 211B in which the element is accommodated. An adsorbent 215 such as activated carbon that adsorbs ethyl alcohol, methyl alcohol, or the like is disposed on the metal mesh plate 214, and gas that affects measurement other than the CO gas to be measured is adsorbed from the gas to be measured.

  Further, since the reference element 212 is arranged on the upstream side of the detection element 213, heat generated by combustion in the detection element 213 can be prevented from affecting the reference element 212. Further, the temperature sensor 217 detects the temperature in the conduit portion 211A and is used for temperature correction.

  FIG. 4 is a configuration diagram of the gas concentration measuring apparatus according to the present embodiment. In FIG. 4, the bridge circuit shown in FIG. 2 is shown. Nodes A and B of the bridge circuit are input to a differential amplifier 50 having an AD conversion function, and the voltage between the nodes A and B is amplified and digitalized. The output is supplied to the control unit 52. The control unit 52 is composed of, for example, a microcomputer, takes in the output of the differential amplifier 50 at a predetermined sampling time (for example, 1 second) interval, and records it in the internal memory. Then, in response to commands from the instantaneous value command button 36, the zero adjustment command button 38, and the power switch 40, the gas concentration value is displayed and reset on the display means 34 by display control to be described later.

  FIG. 5 is a flowchart showing display control and the like by the control unit 52 of the gas concentration measuring apparatus in the present embodiment. When the power switch 40 is turned on (S10), power is turned on in the measuring apparatus and the apparatus waits for a predetermined time (for example, 5 seconds) until the instrument warms up (S12). After waiting, assuming that the gas to be measured has not been inhaled, the current gas concentration to be measured is set to zero, and zero point calibration is performed on the sensor output (S14). Thereafter, the control unit 52 starts display control on the display means 34 in the normal display mode for displaying the maximum gas concentration value. The control unit 52 takes in the output from the differential amplifier 50 every predetermined sampling time (for example, 1 second), and displays the maximum gas concentration value of the measured values up to that time on the display means 34 (S16). Step S16 in the normal display mode is repeated until the instantaneous value button 36 or the zero adjustment button 38 is pressed, and when the newly measured gas concentration exceeds the maximum gas concentration, the measured value becomes the new maximum gas. The concentration is stored in the internal memory and displayed on the display means 34. That is, the maximum gas concentration is constantly updated and displayed in the same measurement session.

  When the instantaneous value button 36 is depressed during the normal display mode (S18), the instantaneous value of the gas concentration sampled every second is displayed on the display means 34 and the measured gas concentration is measured while the button is depressed. Data of the maximum gas concentration value, which is a peak value, is stored and updated in the internal memory (S20). When the pressing of the instantaneous value button 36 is finished, the normal display mode is again resumed, and the measured gas concentration peak value is displayed on the display means 34 (S16).

  When the zero adjustment button 38 is depressed, a series of measured gas concentration data is reset (S28), and zero point adjustment is performed (S14). However, when the zero adjustment button 38 is pressed, if the instantaneous value of the measured gas concentration is a predetermined reference value, for example, the CO gas concentration is 500 ppm or more (S24), the state is inappropriate for zero point adjustment. An error is displayed (S26). Only when the instantaneous value is less than the reference value, the measured gas concentration information is reset, the maximum gas concentration value is cleared (S28), and zero point adjustment is performed (S14). Thereafter, a new measurement session is started, and the peak value of the measured gas concentration is displayed on the display means 34 in the normal display mode (S16). When the above error state occurs, the error can be canceled by the power switch 40. When the power is turned off in the normal display mode (S30), the measurement is finished.

  As described above, since the portable gas concentration measuring apparatus has a simplified configuration with only one display means 34 for displaying the measured gas concentration value, there is no operator in the normal display mode after power-on. The maximum gas concentration value that is the peak value of the measured gas concentration is displayed without pressing down the command button. Thereby, when the operator moves the other end of the intake pipe to an exhaust port or the like to be measured, it is ensured that a partially high gas concentration is not missed. Also, when you want to know the position of incomplete combustion where the CO gas concentration is high, you can display the instantaneous value gas concentration by pressing down the instantaneous value button 36 and move the other end of the intake pipe slowly. The instantaneous value can be observed while In addition, since the maximum gas concentration value is displayed, when a series of measurement sessions is completed, the maximum gas concentration value is cleared and the zero point adjustment of the gas sensor is performed in response to pressing the zero adjustment button. .

  According to the present embodiment, when using a catalytic combustion type gas sensor with a fast detection response speed, if an attempt is made to measure the gas concentration in a predetermined region such as an exhaust port, an instantaneous value is obtained each time the position of the intake pipe moves. Since it changes at high speed, the maximum gas concentration value is displayed in the normal display mode. By using such a display mode, it is possible to reliably detect a failure state in which the CO gas concentration partially increases during the exhaust of the combustion equipment.

It is a block diagram of the portable combustible gas concentration measuring apparatus in this Embodiment. It is a figure which shows the structure of the contact combustion type gas sensor in this Embodiment. It is a figure which shows the structure of the contact combustion type gas sensor in this Embodiment. It is a block diagram of the gas concentration measuring apparatus in this Embodiment. It is a flowchart figure which shows the display control etc. by the control unit 52 of the gas concentration measuring apparatus in this Embodiment.

Explanation of symbols

21: Gas sensor, 30: Measuring device main body, 34: Display means, 36: Instantaneous value command button 38: Zero point adjustment command button, 40: Power switch

Claims (1)

A gas intake pipe for inhaling flammable gas;
An air intake pipe for taking in air;
A mixing section for mixing the inhaled combustible gas and air;
A gas sensor that is supplied with the mixed combustible gas and detects a gas concentration of the combustible gas; and
A single display means for displaying the detected gas concentration;
The gas concentration detected by the gas sensor is acquired at predetermined sampling time intervals, and in the normal mode, the maximum gas concentration value among the detected gas concentrations is displayed on the display means, and in response to an instantaneous value display command, an instantaneous value is displayed. while displaying the gas concentration value on the display means stores the maximum gas concentration value, the response with return to response the normal mode, the zero adjustment command generated in the gas concentration measurement to the end of the instantaneous value display command Then, when the instantaneous value is lower than the reference concentration inappropriate for zero point calibration, the zero point calibration of the gas sensor is performed, and when the instantaneous value is equal to or higher than the reference concentration, an error state is set and the zero point calibration is not performed. It has a control means for so,
The gas sensor is a contact combustion type gas sensor that detects a gas concentration via a temperature at which the combustible gas contacts and burns, and the contact combustion type gas sensor is a carrier in which a catalyst is mixed with a coil wire and has a plurality of penetrations. A portable flammable gas concentration measuring device comprising a carrier having pores attached thereto .

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