JP7199875B2 - hydrogen sensor - Google Patents

Description

The present invention relates to a hydrogen sensor for measuring the concentration of hydrogen gas in atmosphere.

For example, as described in Non-Patent Document 1 below, various detection methods are known for hydrogen sensors that measure the concentration of hydrogen gas in an atmosphere. It has been sold by various gas manufacturers.

Kagaku Kogaku 2017, Vol. 81, No. 8, pp. 410-413 "Special Issue: Progress and New Applications of Gas Sensors"

By the way, as shown in FIG. 5, this type of hydrogen sensor has different measurement ranges depending on the detection method, and also has advantages and disadvantages. In general, semiconductor, catalytic combustion, and electrochemical hydrogen sensors have the advantage of being able to measure with high sensitivity at concentrations lower than the lower limit (1%) of the measurement range of thermal conductivity hydrogen sensors. It has the disadvantage that it cannot measure concentrations of 10% or more. On the other hand, the thermal conductivity type hydrogen sensor has the advantage of being able to measure in a wide range from 1% to 100%, but has the disadvantage of not being able to measure with high sensitivity at the low concentration side of 1% or less. .

For this reason, there has been no conventional hydrogen sensor capable of measuring hydrogen gas in a wide measurement range from low concentrations of 1% or less to high concentrations of 10% or more. In addition, semiconductor type and electrochemical type hydrogen sensors for low concentrations can measure with high resolution (ppm order), but on the other hand, drift (measured value There is a problem that deviation, error) and failure occur. Therefore, it was necessary to select a hydrogen gas detection method in consideration of the usage environment.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a hydrogen sensor capable of measuring hydrogen gas over a wide measurement range by compensating for the disadvantages of the different detection methods.

In order to achieve the above object, a hydrogen sensor according to claim 1 of the present invention is a hydrogen sensor that measures the concentration of hydrogen gas in an atmosphere using a plurality of types of sensors with different detection methods,
a gas flow path through which the hydrogen gas in the atmosphere is introduced/outflowed;
a branch flow path that branches upstream of the gas flow path and merges on the downstream side of the gas flow path;
a thermal conductivity sensor arranged in a space on the upstream side of the branch flow path ;
a first suction means provided at the gas introduction port of the gas flow path for suctioning hydrogen gas in the atmosphere to speed up the response speed;
a low-concentration-side sensor disposed in a space on the downstream side of the branch flow path and having a lower limit of the measurement range on the lower-concentration side than the lower limit of the measurement range of the thermal conductivity sensor;
a second suction means provided at a confluence portion of the branched flow path with the downstream side of the gas flow path for suctioning the hydrogen gas branched on the upstream side of the gas flow path;
When the measurement power source of the thermal conductivity sensor is turned on and the concentration of hydrogen gas measured by the thermal conductivity sensor is determined to be equal to or lower than the lower limit of the measurement range, the measurement power source of the low concentration side sensor is turned on. and a control means for controlling to measure the concentration of the hydrogen gas.

The hydrogen sensor according to claim 2 is a hydrogen sensor that measures the concentration of hydrogen gas in an atmosphere using a plurality of types of sensors with different detection methods,
a gas flow path through which the hydrogen gas in the atmosphere is introduced/outflowed;
a branch flow path that branches upstream of the gas flow path and merges on the downstream side of the gas flow path;
a thermal conductivity sensor arranged in a space on the upstream side of the branch flow path ;
a first suction means provided at the gas introduction port of the gas flow path for suctioning hydrogen gas in the atmosphere to speed up the response speed;
A low-concentration side composed of a combination of a plurality of types of sensors arranged in a space on the downstream side of the branch flow path and having a lower-concentration lower-limit measurement range than the lower-limit measurement range of the thermal conductivity sensor. a sensor;
a second suction means provided at a confluence portion of the branched flow path with the downstream side of the gas flow path for suctioning the hydrogen gas branched on the upstream side of the gas flow path;
When it is determined that the concentration of hydrogen gas measured by the thermal conductivity sensor is equal to or lower than the lower limit of the measurement range after turning on the measurement power supply of the thermal conductivity sensor, the plurality of types of the low concentration side sensor constituting the and control means for selectively turning on any of the measurement power sources of the sensors to measure the concentration of the hydrogen gas.

According to the present invention, hydrogen gas concentration can be measured in a wide measurement range (several ppm to 100%) using a plurality of types of sensors with different detection methods.

1 is a schematic diagram of the internal structure of a hydrogen sensor according to the present invention; FIG. 1 is a block diagram showing the electrical configuration of a hydrogen sensor according to the present invention; FIG. 1 is a schematic diagram of a circuit configuration of an electrochemical sensor used in a hydrogen sensor according to the present invention; FIG. 4 is a flow chart of a measurement algorithm for the hydrogen sensor according to the present invention; FIG. 4 is a diagram showing measurement ranges of multiple types of hydrogen sensors with different detection methods.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated in detail, referring attached drawings.

[Usage of hydrogen sensor]
The hydrogen sensor according to the present invention measures the concentration of hydrogen gas in a target atmosphere, and is used for leak detection in infrastructure facilities that use hydrogen gas, such as hydrogen stations, hydrogen plants, transportation, and storage. .

[Regarding the structure of the hydrogen sensor]
Next, the configuration of the hydrogen sensor of this embodiment will be described with reference to FIG. As shown in FIG. 1, the hydrogen sensor 1 has a gas inlet 3 formed on the upper surface of a rectangular device main body 2 and a gas outlet 4 formed on the lower surface of the device main body 2 so as to face the gas inlet 3 . A gas flow path R1 composed of a linear through-hole is formed between the gas inlet 3 and the gas outlet 4. As shown in FIG. The gas inlet 3 is provided with a suction means 5 such as a fan or a pump for sucking hydrogen gas in the atmosphere to speed up the response speed.

As a result, the hydrogen gas in the atmosphere is sucked into the gas flow path R1 from the gas introduction port 3 of the apparatus main body 2 by the suction means 5, as indicated by the white arrows A1→A2→A3→A4 in FIG. and is led out from the gas outlet 4 through the gas flow path R1.

In the gas flow path R1, as indicated by the black arrows B1->B2->B3 in FIG. A branch flow path R2 is formed that flows parallel to R1 and joins downstream of the gas flow path R1. A suction means 6 such as a fan or a pump is provided at the junction of the branched flow path R2 and the downstream side of the gas flow path R1 to suck the hydrogen gas branched off from the upstream side of the gas flow path R1.

In the branch flow path R2, the thermal conductivity sensor S1 is arranged in the space R2a on the upstream side, and the electrochemical sensor S2 as a low concentration side sensor is arranged in the space R2b on the downstream side. In such an arrangement configuration, the electrochemical sensor S2 turns on the measurement power source and starts measurement, as will be described later, unless the concentration of hydrogen gas measured by the thermal conductivity sensor S1 becomes 1% or less. Therefore, it is possible to prevent deterioration and failure of the electrochemical sensor S2 due to exposure to high-concentration hydrogen gas.

As shown in FIG. 5, the thermal conductivity sensor S1 has a hydrogen gas measurement range of 1% (lower limit) to 100% (upper limit), and the thermal conductivity between hydrogen gas and a reference gas (for example, air) is used to detect the concentration of hydrogen gas flowing in the branch flow path R2.

As shown in FIG. 5, the electrochemical sensor S2 has a hydrogen gas measurement range of 0.01 (lower limit) to 1% (upper limit), and the lower limit of the measurement range is the measurement of the thermal conductivity sensor S1. It is on the lower concentration side than the lower limit of the range, and the two electrodes are electrically connected with a conductor through the electrolyte. The concentration of hydrogen gas flowing in the branch flow path R2 is detected from the magnitude of the flowing current.

[Regarding the electrical configuration of the hydrogen sensor]
Next, the electrical configuration of the hydrogen sensor 1 will be described with reference to FIG. As shown in FIG. 2, the output of the thermal conductivity sensor S1 is input to the A/D conversion circuit 12 via the thermal conductivity measuring circuit 11. As shown in FIG. The output of the electrochemical sensor S2 is connected to the A/D conversion circuit 12 via the electrochemical measurement circuit 13. FIG.

The A/D conversion circuit 12 converts output voltages (analog signals) corresponding to the concentrations of hydrogen gas measured by the measurement circuits 11 and 13 into digital data.

A control circuit (CPU) 14 controls ON/OFF of the measurement ON/OFF circuit 15 according to the hydrogen gas concentration based on the digital data of the thermal conductivity sensor S1 input from the A/D conversion circuit 12 .

More specifically, the control circuit 14 calculates the hydrogen gas concentration from the output voltage value obtained from the thermal conductivity sensor S1, and when the hydrogen gas concentration is 1% (the lower limit of the measurement range) or less, the measurement is turned on. Measurement ON/OFF switches SW1, SW2, and SW3, which will be described later, are turned on via the /OFF circuit 15, and control is performed so that the measurement of the electrochemical sensor S2 is also started.

On the other hand, when the hydrogen gas concentration calculated from the output voltage value obtained from the thermal conductivity sensor S1 is greater than 1% (the lower limit of the measurement range), the control circuit 14 controls the measurement ON/OFF circuit 15. Then, measurement ON/OFF switches SW1, SW2, and SW3, which will be described later, are kept OFF, and control is performed so that the concentration of hydrogen gas is measured only by the thermal conductivity sensor S1.

The D/A conversion circuit 16 as an output circuit finally converts the concentration of hydrogen gas calculated based on the output of the thermal conductivity sensor S1 into an analog signal (hydrogen concentration value) if the concentration of hydrogen gas is greater than 1%. If the concentration of hydrogen gas is 1% or less, the concentration of hydrogen gas calculated based on the output of the electrochemical sensor S2 is converted into an analog signal (hydrogen concentration value) and output.

Here, the circuit configuration of the electrochemical measurement circuit 13 to which the electrochemical sensor S2 is connected will be described with reference to FIG.

As shown in FIG. 3, the electrochemical measurement circuit 13 includes a preamplifier circuit 13a, a voltage follower circuit 13b, and an IV conversion circuit 13c. is applied, the current corresponding to the hydrogen concentration between the counter electrode CE and the sensing electrode WE of the electrochemical sensor S2 is measured.

In the preamplifier circuit 13a, the non-inverting input terminal of the operational amplifier OP1 is grounded via a resistor R1, the bias voltage Vref is input to the inverting input terminal, and the output terminal is connected to the electrochemical sensor S2 via the measurement ON/OFF switch SW1. It is connected to the counter electrode CE.

In the voltage follower circuit 13b, the non-inverting input terminal of the operational amplifier OP2 is connected to the reference electrode RE of the electrochemical sensor S2 via the measurement ON/OFF switch SW2, and the inverting input terminal of the operational amplifier OP2 is connected to the output terminal. is connected to the inverting input terminal of the operational amplifier OP1 of the preamplifier circuit 13a.

The voltage follower circuit 13b prevents current from flowing into the reference electrode RE of the electrochemical sensor S2 and keeps the potential of the reference electrode RE at the bias voltage Vref.

The IV conversion circuit 13c is a circuit that converts the measured current from the electrochemical sensor S2 into a voltage. It is connected to the detection electrode WE of the sensor S2 and to the output terminal of the operational amplifier OP3 via the resistor R3. A measurement ON/OFF switch SW3 is connected to the output of the operational amplifier OP3 of the IV conversion circuit 13c.

In the circuit configuration of FIG. 3, the electrochemical sensor S2 reacts chemically when the measurement ON/OFF switches SW1, SW2, and SW3 controlled by the control circuit 14 of FIG. stops and no current flows.

[Method for measuring concentration of hydrogen gas]
Next, a method for measuring the concentration of hydrogen gas in the atmosphere with the hydrogen sensor 1 configured as described above will be described with reference to the measurement algorithm shown in FIG.

To measure the concentration of hydrogen gas in the atmosphere, first, the measurement power source of the thermal conductivity sensor S1 is turned on (ST1). When the measurement power supply is turned on, the thermal conductivity sensor S1 starts measuring the concentration of hydrogen gas in the atmosphere (ST2).

Next, the control circuit 14 determines whether the hydrogen concentration measured by the thermal conductivity sensor S1 is 1% or less (ST3). When it is determined that the hydrogen concentration measured by the thermal conductivity sensor S1 is 1% or less (ST3-Yes), the measurement ON/OFF circuit 15 turns on the measurement ON/OFF switches SW1, SW2, and SW3, The measurement power source of the electrochemical sensor S2 is turned on (ST4). Then, when the power source for measurement is turned on, the electrochemical sensor S2 starts measuring the concentration of hydrogen gas in the atmosphere (ST5). As a result, the concentration of hydrogen gas in the atmosphere is measured by the thermal conductivity sensor S1 and the electrochemical sensor S2.

After that, the control circuit 14 determines whether or not the measurement has ended (ST6), and if it determines that the measurement has ended (ST6-Yes), it outputs the hydrogen concentration value obtained by the electrochemical sensor S2 at that time (ST7). On the other hand, if it is determined that the measurement is not completed (ST6-No), the process returns to ST2, and the measurement of the hydrogen gas concentration in the atmosphere is continued by the thermal conductivity sensor S1 and the electrochemical sensor S2.

On the other hand, when the control circuit 14 determines in ST3 that the hydrogen concentration measured by the thermal conductivity sensor S1 is not 1% or less, that is, the hydrogen concentration is less than 1% (ST3-No), the electrochemical sensor The measurement power supply in S2 is kept OFF (ST8), and it is determined whether or not the measurement is completed (ST9).

When the control circuit 14 determines that the measurement is completed (ST9-Yes), it outputs the hydrogen concentration value obtained by the thermal conductivity sensor S1 at that time (ST10). On the other hand, if it is determined that the measurement is not finished (ST9-No), the process returns to ST2, and the measurement of the hydrogen gas concentration in the atmosphere by the thermal conductivity sensor S1 is continued.

Thus, according to the present embodiment, a thermal conductivity sensor and an electrochemical sensor with different detection methods are used. Continue to measure the concentration of hydrogen gas with the sensor, and if the concentration of hydrogen gas in the atmosphere measured by the thermal conductivity sensor is 1% or less, turn on the measurement power supply of the electrochemical sensor and check the concentration of hydrogen gas. take measurements. As a result, it is possible to measure the concentration of hydrogen gas over a wide measurement range (several ppm to 100%) by compensating for the shortcomings of the thermal conductivity sensor and the electrochemical sensor, which have different detection methods. can be used without

In addition, a thermal conductivity sensor is placed upstream of the gas flow path through which hydrogen gas in the atmosphere is introduced/discharged, and an electrochemical sensor is placed downstream of the gas flow path. By ON/OFF-controlling the measurement power supply of the electrochemical sensor according to the gas concentration, it is possible to prevent deterioration and failure when the electrochemical sensor is exposed to high-concentration hydrogen gas.

Furthermore, since a thermal conductivity sensor and an electrochemical sensor with different detection methods are used together, when used in a high-humidity environment, the thermal conductivity sensor may be affected by humidity and cause indication deviation. The chemical sensor is almost unaffected and can be corrected.

By the way, in the above-described embodiment, the control circuit 14 controls ON/OFF of the measurement power supply of the electrochemical sensor S2 according to the concentration of hydrogen gas measured by the thermal conductivity sensor S1. When the concentration of hydrogen gas suddenly increases and the amount of change in the concentration of hydrogen gas measured by the thermal conductivity sensor S1 or the electrochemical sensor S2 exceeds a predetermined amount, the measurement power supply of the electrochemical sensor S2 is turned off. You may

Further, in the above-described embodiment, as shown in FIG. 1, in order to reduce the influence of the flow velocity of the hydrogen gas, after the hydrogen gas introduced from the gas inlet 3 is branched upstream of the gas flow path R1, A branch flow path R2 that flows in parallel with the gas flow path R1 and merges on the downstream side of the gas flow path R1 is formed. An electrochemical sensor S2 is arranged on the side. Also, in order to allow the hydrogen gas introduced from the gas inlet 3 to reach the electrochemical sensor S2, the gas inlet 3 and the gas outlet 4 are provided with suction means 5 and 6 . However, it is not limited to these configurations. For example, the thermal conductivity sensor S1 and the electrochemical sensor S2 may be arranged so as to face the gas flow path R1 with their detection surfaces facing the gas flow path R1.

Furthermore, in the above-described embodiment, two types of sensors with different detection methods, the thermal conductivity sensor S1 and the electrochemical sensor S2, are incorporated in the device main body 2, but the configuration is not limited to this. .

That is, in the present embodiment, the thermal conductivity sensor S1 with a hydrogen concentration of 1% or more is essential, but the low-concentration sensor is higher than the lower limit of the measurement range of the thermal conductivity sensor S1. A sensor other than the electrochemical sensor S2 (for example, a semiconductor sensor, a catalytic combustion sensor, etc.) may be used as long as the sensor has a lower limit of the measurement range on the low concentration side.

Further, a plurality of types of sensors are appropriately combined to constitute a low concentration side sensor, and when the hydrogen concentration measured by the thermal conductivity sensor S1 becomes 1% or less, the plurality of types of sensors constituting the low concentration side sensor The concentration of hydrogen gas can also be measured by selectively turning on any measurement power source. For example, when three types of sensors, an electrochemical sensor, a semiconductor sensor, and a catalytic combustion sensor, are used as low-concentration sensors, when the hydrogen concentration measured by the thermal conductivity sensor S1 becomes 1% or less, , when the hydrogen concentration is 0.1 to 1%, the catalytic combustion sensor is turned on, and when the hydrogen concentration is 0.01 to 0.1%, the electrochemical sensor is turned on. At 1%, the measurement power source of the semiconductor sensor is turned on to measure the concentration of hydrogen gas.

Although the best mode of the hydrogen sensor according to the present invention has been described above, the present invention is not limited by the description and drawings according to this mode. In other words, other forms, embodiments, operation techniques, etc. made by those skilled in the art based on this form are all included in the scope of the present invention.

1 Hydrogen sensor 2 Apparatus body 3 Gas inlet 4 Gas outlet 5, 6 Suction means 11 Thermal conductivity measurement circuit 12 A/D conversion circuit 13 Electrochemical measurement circuit 13a Preamplifier circuit 13b Voltage follower circuit 13c IV Conversion circuit 14 control circuit (CPU)
15 Measurement ON/OFF circuit 16 D/A conversion circuit S1 Thermal conductivity sensor S2 Electrochemical sensor R1 Gas channel R2 Branch channel SW1, SW2, SW3 Measurement ON/OFF switch RE Reference electrode CE Counter electrode WE Detection electrode

Claims (2)

A hydrogen sensor that measures the concentration of hydrogen gas in an atmosphere using a plurality of types of sensors with different detection methods,
a gas flow path through which the hydrogen gas in the atmosphere is introduced/outflowed;
a branch flow path that branches upstream of the gas flow path and merges on the downstream side of the gas flow path;
a thermal conductivity sensor arranged in a space on the upstream side of the branch flow path ;
a first suction means provided at the gas introduction port of the gas flow path for suctioning hydrogen gas in the atmosphere to speed up the response speed;
a low-concentration-side sensor disposed in a space on the downstream side of the branch flow path and having a lower limit of the measurement range on the lower-concentration side than the lower limit of the measurement range of the thermal conductivity sensor;
a second suction means provided at a confluence portion of the branched flow path with the downstream side of the gas flow path for suctioning the hydrogen gas branched on the upstream side of the gas flow path;
When the measurement power source of the thermal conductivity sensor is turned on and the concentration of hydrogen gas measured by the thermal conductivity sensor is determined to be equal to or lower than the lower limit of the measurement range, the measurement power source of the low concentration side sensor is turned on. and control means for controlling to measure the concentration of the hydrogen gas. A hydrogen sensor that measures the concentration of hydrogen gas in an atmosphere using a plurality of types of sensors with different detection methods,
a gas flow path through which the hydrogen gas in the atmosphere is introduced/outflowed;
a branch flow path that branches upstream of the gas flow path and merges on the downstream side of the gas flow path;
a thermal conductivity sensor arranged in a space on the upstream side of the branch flow path ;
a first suction means provided at the gas introduction port of the gas flow path for suctioning hydrogen gas in the atmosphere to speed up the response speed;
A low-concentration side composed of a combination of a plurality of types of sensors arranged in a space on the downstream side of the branch flow path and having a lower-concentration lower-limit measurement range than the lower-limit measurement range of the thermal conductivity sensor. a sensor;
a second suction means provided at a confluence portion of the branched flow path with the downstream side of the gas flow path for suctioning the hydrogen gas branched on the upstream side of the gas flow path;
When it is determined that the concentration of hydrogen gas measured by the thermal conductivity sensor is equal to or lower than the lower limit of the measurement range after turning on the measurement power supply of the thermal conductivity sensor, the plurality of types of the low concentration side sensor constituting the and control means for selectively turning on any measurement power source of the sensor to measure the concentration of the hydrogen gas.

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