Hydrogen sensor and hydrogen detection system

Abstract

The present disclosure provides a hydrogen sensor, comprising: a substrate; a sensing film disposed on a first surface of the substrate, including a catalyst for decomposing hydrogen molecules and tungsten oxide; a pair of electrodes disposed on the first surface of the substrate in contact with the sensing film; and an IC tag connected to the pair of electrodes, the IC tag including: an IC chip; an antenna connected to the IC chip; and a pair of sensor terminals connected to the IC chip and to the pair of electrodes, respectively, the IC chip being an open-circuit short-circuit type that determines a high resistance state when a resistance value between the sensor terminals is above a first threshold resistance value, and determines a low resistance state when the resistance value between the sensor terminals is below a second threshold resistance value that is less than the first threshold resistance value, the resistance value between the sensor terminals when the hydrogen concentration is zero being above the first threshold resistance value, and the resistance value between the sensor terminals when the hydrogen concentration is a set value being below the second threshold resistance value.

Description

Technical Field

[0001] This disclosure relates to hydrogen sensors and hydrogen detection systems. Background Technology

[0002] In recent years, from the perspective of protecting the Earth's environment and preventing the depletion of fossil fuels, there has been a desire to effectively utilize clean and renewable energy. In particular, research on using hydrogen as an energy source has been actively conducted, primarily focusing on fuel cells. On the other hand, the explosive limits of hydrogen range from 4% to 75%. Therefore, in order to make hydrogen a widely available energy source, the control of hydrogen storage and transportation, as well as safety devices to prevent hydrogen leaks, are indispensable.

[0003] For example, considering the odorants used in city gas, the use of hydrogen could lead to problems such as fuel cell poisoning and gas turbine degradation. Therefore, safety measures to replace odorants are needed. To this end, hydrogen sensors that detect hydrogen leaks are crucial to ensure safety.

[0004] Conventional hydrogen sensors primarily employ either contact combustion or semiconductor methods. Contact combustion hydrogen sensors use a heater to heat catalyst metals such as platinum or palladium, utilizing oxygen from the air to oxidize the hydrogen gas in contact with the catalyst. The heat generated during this oxidation is electrically detected as a change in the conductivity of the catalyst metal. Semiconductor hydrogen sensors detect changes in the electrical properties of the sensing membrane, i.e., changes in resistance, caused by the adsorption of hydrogen gas onto the sensing membrane. Like contact combustion sensors, semiconductor hydrogen sensors are also used under heating conditions. Therefore, conventional hydrogen sensors, including those using contact combustion and semiconductor methods, pose a risk to applications involving hydrogen gases requiring explosion-proof protection due to the heating process.

[0005] In addition, gas-color-changing hydrogen sensors have attracted much attention in recent years. These sensors utilize metal oxides such as tungsten trioxide, whose color changes according to hydrogen adsorption, and catalysts such as platinum, which decompose hydrogen gas into hydrogen atoms, to optically detect hydrogen. Since the electrical properties of metal oxides such as tungsten trioxide also change due to hydrogen adsorption, gas-color-changing hydrogen sensors can also detect hydrogen electrically. (See, for example, Patent Document 1)

[0006] Prior art literature

[0007] Patent documents

[0008] Patent Document 1: JP Patent No. 4496204 Summary of the Invention

[0009] -The problem the invention aims to solve-

[0010] In the wireless tag described in Patent Document 1, if the resonant circuit receives a wireless signal at its resonant frequency, it induces an alternating current, which is stored as starting power and used to transmit data. On the other hand, in the wireless tag, if hydrogen comes into contact with tungsten oxide, the tungsten oxide becomes conductive, short-circuiting the antenna coil. This causes a change in inductance, and consequently, a change in the resonant frequency of the resonant circuit. As a result, even if a wireless signal is received, no alternating current is induced, and no data is transmitted. Thus, the aforementioned wireless tag determines the presence or absence of hydrogen based on the presence or absence of a response from the wireless tag relative to the transmitted wireless signal. However, in the aforementioned wireless tag, only the presence or absence of hydrogen can be detected.

[0011] This disclosure was made in view of the above-mentioned circumstances, and its main purpose is to provide a hydrogen sensor capable of managing hydrogen concentration.

[0012] -Methods for solving problems-

[0013] This disclosure provides a hydrogen sensor comprising: a substrate; a sensing membrane disposed on a first surface of the substrate, comprising a catalyst for decomposing hydrogen molecules and tungsten oxide; a pair of electrodes disposed on the first surface of the substrate in contact with the sensing membrane; and an IC tag connected to the pair of electrodes, the IC tag comprising: an IC chip; an antenna connected to the IC chip; and a pair of sensor terminals connected to the IC chip and respectively connected to the pair of electrodes. The IC chip is an open-circuit / short-circuit type, i.e., it is determined to be in a high-resistance state when the resistance value between the sensor terminals is above a first threshold resistance value, and in a low-resistance state when the resistance value between the sensor terminals is below a second threshold resistance value which is smaller than the first threshold resistance value. When the hydrogen concentration is zero, the resistance value between the sensor terminals is above the first threshold resistance value, and when the hydrogen concentration is a set value, the resistance value between the sensor terminals is below the second threshold resistance value.

[0014] Other embodiments of this disclosure provide hydrogen detection systems that utilize the hydrogen sensor described above.

[0015] Other embodiments of this disclosure provide a hydrogen pipeline using the hydrogen detection system described above.

[0016] -Invention Effects-

[0017] The hydrogen sensor disclosed herein serves to manage hydrogen concentration. Attached Figure Description

[0018] Figure 1 This is a schematic top view illustrating the hydrogen sensor in this disclosure.

[0019] Figure 2 This is a graph illustrating the relationship between hydrogen concentration and the resistance value between the terminals of the sensor in the hydrogen sensor disclosed herein.

[0020] Figure 3 This is a graph illustrating the relationship between hydrogen concentration and the resistance value between sensor terminals in a hydrogen sensor that is not part of the embodiments of this disclosure.

[0021] Figure 4 This is a schematic top view illustrating the hydrogen sensor in this disclosure.

[0022] Figure 5 This is a schematic top view illustrating the hydrogen sensor in this disclosure.

[0023] Figure 6 This is a schematic top view illustrating the hydrogen sensor in this disclosure.

[0024] Figure 7 This is a schematic top view illustrating the hydrogen sensor in this disclosure.

[0025] Figure 8 This is a schematic top view illustrating the hydrogen sensor in this disclosure.

[0026] Figure 9 This is a schematic top view illustrating the hydrogen sensor in this disclosure.

[0027] Figure 10 This is a schematic top view illustrating the hydrogen sensor in this disclosure.

[0028] Figure 11 This is a schematic top view illustrating the hydrogen sensor in this disclosure.

[0029] Figure 12 This is a schematic top view illustrating the hydrogen sensor in this disclosure.

[0030] Figure 13 This is a schematic top view illustrating the hydrogen sensor in this disclosure.

[0031] Figure 14 This is a schematic top view illustrating the hydrogen sensor in this disclosure.

[0032] Figure 15 This is a schematic diagram illustrating the hydrogen detection system of this disclosure.

[0033] Figure 16 This is a schematic diagram illustrating the hydrogen detection system of this disclosure.

[0034] Figure 17 This is a schematic diagram illustrating the hydrogen detection system of this disclosure.

[0035] Figure 18 This is a graph showing the relationship between hydrogen concentration and the resistance value between the terminals of the sensor in the hydrogen sensor of Example 1.

[0036] Figure 19 This is a graph showing the relationship between hydrogen concentration and resistance between the terminals of the sensor in the hydrogen sensors of Comparative Examples 1 to 2. Detailed Implementation

[0037] The embodiments of this disclosure will now be described with reference to the accompanying drawings. However, this disclosure can be implemented in many different ways and is not intended to be limited to the embodiments illustrated below. Furthermore, in order to make the description clearer, the drawings sometimes schematically show the width, thickness, shape, etc. of each component compared to the embodiments, but this is merely an example and does not limit the interpretation of this disclosure. In addition, in this specification and the drawings, the same reference numerals are used for the same elements as described above in the figures that have already appeared, and detailed descriptions are sometimes appropriately omitted.

[0038] In this specification, when describing the arrangement of other components on a component, the terms "surface" or "surface" are used, unless otherwise specified, to include both the case where other components are arranged directly above or below a component in a manner connected to that component, and the case where other components are arranged above or below a component via another component.

[0039] Furthermore, in this specification, the terms "sheet," "membrane," and "plate" are not distinguished solely based on different names. For example, "sheet" is used to encompass components that can also be called membranes or plates.

[0040] The hydrogen sensor and hydrogen detection system disclosed herein will be described in detail below.

[0041] A. Hydrogen sensor

[0042] The hydrogen sensor disclosed herein utilizes a hydrogen sensor in which the resistance value decreases when a sensing membrane containing a catalyst and tungsten oxide reacts with hydrogen. The inventors of this disclosure have conducted in-depth research on components for detecting changes in the resistance value of the sensing membrane in such a hydrogen sensor, focusing on open-circuit / short-circuit type IC chips. An open-circuit / short-circuit type IC chip is one that determines a high resistance state when the resistance value between the terminals is above a first threshold, and a low resistance state when the resistance value between the terminals is below a second threshold, thereby detecting changes in resistance value. When using an open-circuit / short-circuit type IC chip in such a hydrogen sensor, it is important to design the sensor such that the resistance value between the terminals is above the first threshold in an atmospheric environment, and below the second threshold when the hydrogen concentration in the ambient atmosphere increases. This allows for the detection of hydrogen leakage. Here, to provide an inexpensive hydrogen sensor, it is preferable to use a commercially available open-circuit / short-circuit type IC chip. However, in commercially available open-circuit / short-circuit type IC chips, the first threshold and the second threshold are predetermined. Therefore, it was determined that simply applying an open-circuit / short-circuit type IC chip to a hydrogen sensor would result in the resistance between the terminals not falling below the second threshold, even if the resistance value between the terminals falls below the second threshold or the hydrogen concentration in the ambient atmosphere increases. In either an air atmosphere or a hydrogen atmosphere, if the resistance value between the terminals falls below the second threshold, it is determined that hydrogen is leaking in the air atmosphere as well. Furthermore, even if the hydrogen concentration in the ambient atmosphere increases, if the resistance value between the terminals does not fall below the second threshold, hydrogen leakage cannot be detected. The inventors of this disclosure further investigated and found that by appropriately designing the thickness of the sensing film, the spacing between the electrodes, and other parameters of the sensing film and the pair of electrodes according to the first and second thresholds of the open-circuit / short-circuit type IC chip, the resistance value between the terminals can be adjusted based on the hydrogen concentration. That is, it was found that when an open-circuit / short-circuit type IC chip is used in a hydrogen sensor as described above, it is possible to design the sensor such that the resistance value between the terminals is above the first threshold in an air atmosphere, and falls below the second threshold when the hydrogen concentration in the ambient atmosphere increases. This disclosure is based on this insight.

[0043] Furthermore, conventionally, open-circuit / short-circuit type IC chips have been used to detect breaks in wiring or circuits. Apart from the reports of the inventors of this disclosure, no examples of using open-circuit / short-circuit type IC chips in hydrogen sensors have been reported.

[0044] The hydrogen sensor disclosed herein includes: a substrate; a sensing membrane disposed on a first surface of the substrate, comprising a catalyst for decomposing hydrogen molecules and tungsten oxide; a pair of electrodes disposed on the first surface of the substrate in contact with the sensing membrane; and an IC tag connected to the pair of electrodes, the IC tag including: an IC chip; an antenna connected to the IC chip; and a pair of sensor terminals connected to the IC chip and respectively connected to the pair of electrodes. The IC chip is an open-circuit / short-circuit type, i.e., it is determined to be in a high-resistance state when the resistance value between the sensor terminals is above a first threshold resistance value, and in a low-resistance state when the resistance value between the sensor terminals is below a second threshold resistance value which is smaller than the first threshold resistance value; the resistance value between the sensor terminals is above the first threshold resistance value when the hydrogen concentration is zero, and the resistance value between the sensor terminals is below the second threshold resistance value when the hydrogen concentration is a set value.

[0045] Figure 1 This is a schematic top view illustrating an example of a hydrogen sensor in this disclosure. (See diagram below.) Figure 1 As shown, the hydrogen sensor 1 includes: a substrate 2; a sensing membrane 3 disposed on a first surface of the substrate 2, comprising a catalyst for decomposing hydrogen molecules and tungsten oxide; a pair of electrodes 4a and 4b, grounded and disposed on the first surface of the substrate 2; and an IC tag 5 connected to the pair of electrodes 4a and 4b. Figure 1 In the IC tag 5, a pair of electrodes 4a and 4b are a pair of comb-tooth electrodes. The electrodes 4a and 4b are alternately arranged, spaced apart by an interval d1 that detects changes in the resistance value of the sensing film 3. Furthermore, the IC tag 5 includes: a second substrate 21; an IC chip 22 disposed on a first surface of the second substrate 21; an antenna 23 disposed on the first surface of the second substrate 21 and connected to the IC chip 22; and a pair of sensor terminals 24a and 24b disposed on the first surface of the second substrate 21 and connected to the IC chip 22, respectively connected to the pair of electrodes 4a and 4b. In the IC tag 5, the IC chip 22 is an open-circuit / short-circuit type. A high-resistance state is determined when the resistance between the sensor terminals 24a and 24b connected to the IC chip 22 is above a first threshold resistance value, and a low-resistance state is determined when the resistance between the sensor terminals 24a and 24b is below a second threshold resistance value.

[0046] The hydrogen sensor disclosed herein utilizes the principle that the resistance decreases when a sensing membrane containing a catalyst and tungsten oxide reacts with hydrogen. The operating principle of the hydrogen sensor in this disclosure will be explained.

[0047] Tungsten oxide (WO3) has high resistance. Therefore, in the absence of hydrogen, the sensing membrane 3 has high resistance and is insulating. At this time, the pair of electrodes 4a and 4b are insulated and non-conductive. Therefore, even when power is supplied from the RFID reader to the IC tag 5, current will not flow through the sensing membrane 3 to the pair of electrodes 4a and 4b. In the IC chip 22, if the resistance between the sensor terminals 24a and 24b is above a first threshold resistance value, it becomes a high-resistance state, for example, the tag information becomes "0". In the IC tag 5, the above information is transmitted to the RFID reader via the antenna 23. In this case, it is determined that there is no hydrogen leakage.

[0048] On the other hand, when hydrogen molecules come into contact with a catalyst, they decompose and adsorb to produce hydrogen atoms. These hydrogen atoms reduce tungsten oxide (WO3) to generate a non-stoichiometric compound (H2O). x WO3 (0 < x < 1)). Non-stoichiometric compounds (H x WO3) is in W 5+ and W 6+ The tungsten oxide is in a mixed valence state, resulting in low resistance. Therefore, in the presence of hydrogen, the aforementioned reduction reaction of tungsten oxide occurs, reducing the resistance of the sensing film 3 and making it conductive. At this time, the pair of electrodes 4a and 4b are short-circuited, becoming conductive. Therefore, when power is supplied from the RFID reader to the IC tag 5, current flows through the sensing film 3 to the pair of electrodes 4a and 4b. In the IC chip 22, if the resistance between the sensor terminals 24a and 24b is below the second threshold resistance value, it becomes a low-resistance state, for example, the flag information becomes "1". In the IC tag 5, the above information is transmitted to the RFID reader via the antenna 23. In this case, it is determined that there is a hydrogen leak.

[0049] Thus, hydrogen gas can be detected in IC tag 5 by detecting the change in resistance between terminals 24a and 24b of the sensor.

[0050] Figure 2 This is a graph illustrating an example of the relationship between hydrogen concentration and the resistance value between the terminals of the sensor in the hydrogen sensor disclosed herein. Figure 2In this diagram, T1 represents the first threshold resistance value, T2 represents the second threshold resistance value, and S represents the set value of the hydrogen concentration. When the hydrogen concentration is zero, as described above, the resistance of the sensing membrane 3 is high, therefore the pair of electrodes 4a and 4b are in a non-conductive state. At this time, the resistance value R1 between the sensor terminals 24a and 24b is greater than or equal to the first threshold resistance value T1, thus becoming a high-resistance state, for example, the flag information becomes "0". On the other hand, if the hydrogen concentration increases, the resistance of the sensing membrane 3 decreases, and the pair of electrodes 4a and 4b become conductive. Furthermore, if the resistance value between the sensor terminals 24a and 24b becomes less than or equal to the second threshold resistance value T2, then it becomes a low-resistance state, for example, the flag information becomes "1". When the hydrogen concentration is the set value S, the resistance value R2 between the sensor terminals 24a and 24b is less than or equal to the second threshold resistance value T2. Therefore, if the hydrogen concentration becomes greater than or equal to the set value S, hydrogen leakage is detected. Therefore, in the hydrogen sensor of this disclosure, if the hydrogen concentration becomes greater than or equal to a given concentration, hydrogen leakage can be reliably detected, and the hydrogen concentration can be managed. Furthermore, the inventors of this disclosure conducted research and found that, in the embodiments described later... Figure 18 In such a double logarithmic graph, the hydrogen concentration and the resistance value between the sensor terminals are in a linear regression.

[0051] Figure 3 This is a graph illustrating an example of the relationship between hydrogen concentration and the resistance value between the terminals of a hydrogen sensor, which is not part of this disclosure. Figure 3 Examples include the resistance value between the sensor terminals when the hydrogen concentration is zero, which is not above the first threshold resistance value, and the resistance value between the sensor terminals when the hydrogen concentration is a set value, which is not below the second threshold resistance value. That is, Figure 3 These are examples of hydrogen sensors not disclosed herein. First, regarding the depiction of the black triangle, when the hydrogen concentration is zero, the resistance value R3 between the sensor terminals 24a and 24b is greater than the first threshold resistance value T1, therefore, for example, the flag information becomes "0". On the other hand, when the hydrogen concentration is a set value S, the resistance value R4 between the sensor terminals 24a and 24b is higher than the second threshold resistance value T2, therefore, for example, the flag information does not become "1". Therefore, even in a state of high hydrogen concentration and hydrogen leakage, hydrogen leakage cannot be detected. Next, regarding the depiction of the black quadrilateral, when the hydrogen concentration is zero, the resistance value R5 between the sensor terminals 24a and 24b is less than the second threshold resistance value T2, therefore, for example, the flag information becomes "1". Therefore, even if the hydrogen concentration is zero, it will be judged as a hydrogen leak. Therefore, in such a case, the hydrogen concentration cannot be managed.

[0052] Therefore, by using the hydrogen sensor of this disclosure, hydrogen leaks can be reliably detected and hydrogen concentrations can be managed.

[0053] Furthermore, conventional hydrogen sensors, such as semiconductor and contact combustion type sensors, require heating as mentioned above. Moreover, conventional contact combustion and semiconductor type hydrogen sensors detect hydrogen in the area where they are installed. Therefore, they can only detect hydrogen within a narrow range, approximately 10 cm around the sensor. For example, in suction nozzle type hydrogen sensors, it is difficult to detect hydrogen unless the nozzle is precisely pointed towards the hydrogen leak point, requiring highly skilled operators.

[0054] In contrast, the reduction reaction of tungsten oxide described above does not require an electrical supply. Therefore, the hydrogen sensor of this disclosure can be scaled up and can detect hydrogen over a relatively large area at low cost. Thus, by using the hydrogen sensor of this disclosure, hydrogen leaks can be detected not only in small devices such as fuel cells, but also in large devices such as hydrogen production facilities, hydrogen pipelines, transport tankers, storage tanks, hydrogen power plants, and hydrogen refueling stations.

[0055] Furthermore, in the wireless tag described in Reference 1, the circuit structure becomes complex and manufacturing costs increase in order to detect changes in the resonant frequency of the resonant circuit. In contrast, in the hydrogen sensor of this disclosure, by using the aforementioned open-circuit / short-circuit type IC chip, the circuit structure can be simplified and manufacturing costs can be reduced.

[0056] The hydrogen sensors in this disclosure are described below according to each structure.

[0057] 1. Characteristics of hydrogen sensors

[0058] In the hydrogen sensor disclosed herein, in the open-circuit / short-circuit type where the IC chip changes from a high resistance state when the resistance between the sensor terminals is above a first threshold resistance value and to a low resistance state when the resistance between the sensor terminals is below a second threshold resistance value which is smaller than the first threshold resistance value, the resistance between the sensor terminals is above the first threshold resistance value when the hydrogen concentration is zero, and below the second threshold resistance value when the hydrogen concentration is a set value.

[0059] In the hydrogen sensor disclosed herein, the resistance value between the sensor terminals when the hydrogen concentration is zero is greater than or equal to a first threshold resistance value. Here, the hydrogen concentration in the air is approximately 0.00005%. Therefore, in this specification, the case of zero hydrogen concentration includes the concept of a hydrogen concentration of 0.00005% or less.

[0060] Furthermore, in the hydrogen sensor disclosed herein, the resistance value between the sensor terminals when the hydrogen concentration is a set value is less than or equal to a second threshold resistance value. For example, when the hydrogen concentration is set to 1%, and the second threshold resistance value is set to 100%, the difference between the resistance value between the sensor terminals when the hydrogen concentration is set to the set value and the second threshold resistance value is preferably more than 1% of the second threshold resistance value, more preferably more than 5% of the second threshold resistance value, and even more preferably more than 10% of the second threshold resistance value. The characteristics of the IC chip can sometimes deviate. Therefore, considering safety, the above-mentioned difference is preferably within the above range. On the other hand, for example, when the hydrogen concentration is set to 1%, and the second threshold resistance value is set to 100%, the difference between the resistance value between the sensor terminals when the hydrogen concentration is set to the set value and the second threshold resistance value is preferably less than 20% of the second threshold resistance value, more preferably less than 15% of the second threshold resistance value, and even more preferably less than 10% of the second threshold resistance value. If the above difference is too large, the resistance value between the sensor terminals when the hydrogen concentration is significantly lower than the set value may also fall below the second threshold resistance value, potentially making hydrogen concentration management difficult. Specifically, when the hydrogen concentration is set to 1%, and the second threshold resistance value is set to 100%, the difference between the resistance value between the sensor terminals when the hydrogen concentration is set and the second threshold resistance value is preferably 1% or more and 20% or less of the second threshold resistance value, more preferably 5% or more and 15% or less of the second threshold resistance value.

[0061] The resistance between the sensor terminals at a given hydrogen concentration is determined using the following method: First, remove the IC tag from the hydrogen sensor. Next, while exposing the hydrogen sensor to an ambient atmosphere with a given hydrogen concentration, use an LCR meter at a frequency of 20 kHz to measure the impedance of a pair of electrodes connected to a pair of sensor terminals on the IC tag. Calculate the resistance between the electrodes based on this impedance. Perform five measurements. The average of the three measurements remaining after removing the maximum and minimum values ​​is taken as the resistance between the sensor terminals at the given hydrogen concentration.

[0062] As mentioned above, the hydrogen concentration in the air is approximately 0.00005%, and the case of zero hydrogen concentration also includes cases where the hydrogen concentration is below 0.00005%. Therefore, when measuring the resistance value between the terminals of the sensor when the hydrogen concentration is zero, the hydrogen sensor can be exposed to air.

[0063] Furthermore, when measuring the resistance between the sensor terminals at a set hydrogen concentration, the hydrogen sensor is sealed within a closed gas chamber connected to a gas mixing device via gas piping when exposed to an atmosphere of a given hydrogen concentration. For example, a gas mixing device with a built-in flow meter manufactured by Cefrol Corporation can be used. This allows for precise, safe, and repeatable mixing of hydrogen and air at any desired concentration. While the hydrogen sensor reacts very quickly to hydrogen, a time is required for resistance saturation; therefore, it is preferable to maintain the ambient atmosphere at the given hydrogen concentration for at least 10 minutes. The closed gas chamber is, for example, a metal-made closed gas chamber with a transparent window made of glass or resin and a gasket made of resin or rubber, preferably with a structure that does not interfere with RFID communication. This allows for the evaluation not only of separate IC tag-type hydrogen sensors where the IC tag and the substrate with the sensing film and a pair of electrodes are separate, but also of integrated IC tag-type hydrogen sensors where the IC tag and the substrate with the sensing film and a pair of electrodes are integrated. Furthermore, the sealed gas chamber can be, for example, a cylinder with a diameter of 100 mmφ and a height of 20 mm. The transparent window can be, for example, a 5 mm thick glass plate or a 5 mm thick acrylic sheet. The gasket can be made of silicone rubber, fluororubber, or nitrile rubber. The gas piping can be flexible piping made of resin or rubber, or fixed piping made of metal. The gas piping can be made of stainless steel or polypropylene. Furthermore, the gas piping can be, for example, pipes with a diameter of 5 mmφ or more and 10 mmφ or less. The LCR measuring instrument is installed outside the sealed gas chamber via electrical wiring and gaskets. Details regarding the measurement conditions are described in the embodiments described later.

[0064] In the hydrogen sensor disclosed herein, methods for adjusting the resistance value between the sensor terminals when the hydrogen concentration is zero include, for example, adjusting the spacing between a pair of electrodes, such as the spacing between a pair of comb electrodes, and adjusting the thickness of the sensing membrane. There is a tendency that if the spacing between the pair of comb electrodes widens, the resistance value between the sensor terminals when the hydrogen concentration is zero increases; conversely, if the spacing between the pair of comb electrodes narrows, the resistance value between the sensor terminals when the hydrogen concentration is zero decreases. Furthermore, there is a tendency that if the thickness of the sensing membrane increases, the resistance value between the sensor terminals when the hydrogen concentration is zero increases; conversely, if the thickness of the sensing membrane thins, the resistance value between the sensor terminals when the hydrogen concentration is zero decreases.

[0065] The method for adjusting the resistance between the sensor terminals when the hydrogen concentration is at a set value is the same as the method described above for adjusting the resistance between the sensor terminals when the hydrogen concentration is zero. There is a tendency that if the spacing between the pair of comb electrodes widens, the resistance between the sensor terminals when the hydrogen concentration is at the set value increases; conversely, if the spacing between the pair of comb electrodes narrows, the resistance between the sensor terminals when the hydrogen concentration is at the set value decreases. Furthermore, there is a tendency that if the thickness of the sensing film increases, the resistance between the sensor terminals when the hydrogen concentration is at the set value increases; conversely, if the thickness of the sensing film decreases, the resistance between the sensor terminals when the hydrogen concentration is at the set value decreases.

[0066] As mentioned above, the explosive limits of hydrogen are 4%-75%. Therefore, the set value for hydrogen concentration is less than 4%. Considering safety, the set value for hydrogen concentration is preferably, for example, 2% or less, more preferably 1% or less. On the other hand, if the set value for hydrogen concentration is too low, even if the concentration is not extremely low enough to cause an explosion, it will be judged as a hydrogen leak. Therefore, the set value for hydrogen concentration is preferably, for example, 1% or more. That is, the set value for hydrogen concentration is preferably 1% or more and less than 4%, more preferably 1% or more and less than 2%, and particularly preferably 1%.

[0067] The hydrogen concentration setpoint is determined using the following method. In the hydrogen sensor, as described above, there are cases where hydrogen leakage is detected as not occurring and cases where hydrogen leakage is detected. First, the hydrogen sensor is sealed within a closed gas chamber connected to a gas mixing device via gas piping. The gas mixing device, closed gas chamber, and gas piping are as described above. An IC tag can be placed inside the closed gas chamber or placed outside the closed gas chamber via electrical wiring through packing. The set temperature is set to 25°C. The target fluids are hydrogen and air. The flow rate of the hydrogen and air mixture is always set to 10 mL / min. Next, in the closed gas chamber, the hydrogen and air mixing ratio is set to 0% hydrogen and 100% air. Next, adjustments are made in the closed gas chamber to achieve an arbitrary hydrogen concentration. First, the hydrogen concentration is adjusted to 0.1%. As described above, the hydrogen sensor reacts very quickly to hydrogen, but time is required for resistance saturation; therefore, it is preferable to maintain this hydrogen concentration atmosphere for at least 10 minutes. Next, radio waves are transmitted from the RFID reader to confirm whether the hydrogen sensor reacts to detect hydrogen in an ambient atmosphere with the specified hydrogen concentration. Then, the sealed gas chamber is opened and maintained for 10 minutes to restore the ambient atmosphere. Next, the hydrogen concentration in the sealed gas chamber is increased by 0.1% each time, and the above operation is repeated. Then, the minimum hydrogen concentration at which a hydrogen leak is determined is calculated. The measurement is performed 5 times, and the average of the minimum hydrogen concentrations is taken as the set value for the hydrogen concentration.

[0068] 2. IC tag

[0069] The IC tag disclosed herein includes: an IC chip; an antenna connected to the IC chip; and a pair of sensor terminals connected to the IC chip, each connected to a pair of electrodes. The IC chip is an open-circuit / short-circuit type, meaning it is determined to be in a high-resistance state when the resistance between the sensor terminals is above a first threshold resistance value, and in a low-resistance state when the resistance between the sensor terminals is below a second threshold resistance value, which is smaller than the first threshold resistance value. Furthermore, the IC tag is also known as an RF tag, RFID tag, electronic tag, wireless tag, etc. If it is an IC tag, RFID can be used to detect hydrogen gas.

[0070] In IC chips, the first threshold resistance value and the second threshold resistance value are not particularly limited, as long as the second threshold resistance value is lower than the first threshold resistance value. The first threshold resistance value is preferably 1 MΩ or higher and 20 MΩ or lower, more preferably 10 MΩ or higher and 15 MΩ or lower. If the first threshold resistance value is too low, frequent changes in resistance value may be detected, potentially leading to frequent misjudgments of hydrogen leakage. Furthermore, if the first threshold resistance value is too low, the difference between the first and second threshold resistance values ​​becomes smaller, making design more difficult. The difference between the first and second threshold resistance values ​​is preferably 10 MΩ or higher and 100 MΩ or lower. A difference that is too small or too large also makes design difficult.

[0071] The first and second threshold resistance values ​​are determined using the following method. First, a fixed resistor with a known resistance value and a commercially available RFID reader are prepared. Additionally, an IC tag is removed from the hydrogen sensor. The fixed resistor is connected to a pair of sensors on the IC tag via terminals. A read signal is sent via the RFID reader, and confirmation is obtained by observing the reflected signal. In open-circuit and short-circuit type IC chips, an open circuit ideally refers to a state where the load (resistance, impedance) connected to the IC chip is infinitely large, i.e., a state where the external load connection terminals of the IC chip are released. Conversely, a short circuit ideally refers to a state where the load (resistance, impedance) connected to the IC chip is zero, i.e., a state where the external load connection terminals of the IC chip are short-circuited by a wire. However, in typical circuits, it is impossible to physically and mechanically discontinue the load. Therefore, a resistance value above a certain threshold is generally considered an open circuit, and a resistance value below a certain threshold is generally considered a short circuit. The threshold resistance value is set to a resistance value that is generally considered to be in an insulating state when open-circuited and a resistance value that is generally considered to be in a conductive state when short-circuited. In this disclosure, an open circuit is defined as a high-resistance state, and a short circuit as a low-resistance state. Therefore, a first threshold resistance value is set to a resistance value that can be considered as an insulating state. Specifically, the minimum resistance value among those considered as insulating states is set as the first threshold resistance value. Furthermore, a second threshold resistance value is set to a resistance value that can be considered as a conductive state. Specifically, the maximum resistance value among those considered as conductive states is set as the second threshold resistance value. Additionally, while the first and second threshold resistance values ​​are disclosed as characteristic data for commercially available IC chips, individual differences exist, hence the above-described measurement method is used.

[0072] For example, the UCODE G2iM+ manufactured by NXP is an open-circuit or short-circuit type IC chip.

[0073] An IC tag only needs to include an IC chip, an antenna connected to the IC chip, and a pair of sensor terminals connected to the IC chip and each connected to a pair of electrodes. The structure of an IC tag is the same as that of a general IC tag.

[0074] IC tags include active types with built-in power supplies (batteries) and passive types without built-in power supplies (batteries). Passive tags are preferred because they do not have their own power supply (battery) but instead obtain power from externally supplied radio waves via an antenna.

[0075] There must be at least one IC tag. There may be one or more IC tags.

[0076] IC tags can be integrated with a substrate containing a sensing film and a pair of electrodes, or they can be separate components. Figure 1In this configuration, the IC tag 5 is separate from the substrate 2, which is equipped with the sensing film 3 and a pair of electrodes 4a and 4b; they are separate components. On the other hand, in... Figure 4 In this design, an IC tag 5 is disposed on one side of substrate 1, and the IC tag 5 is integrated with substrate 2, which is equipped with a sensing film 3 and a pair of electrodes 4a and 4b. When the IC tag and the substrate with the sensing film and electrodes are separate, the substrate with the sensing film and electrodes can be directly disposed on the object to be detected for hydrogen leakage, and the IC tag can be configured to be detached from metals with electromagnetic shielding properties, or to be positioned so that the antenna is directly opposite an RFID reader for easier signal transmission and reception. On the other hand, when the IC tag and the substrate with the sensing film and electrodes are integrated, the hydrogen sensor can be placed in a more confined space.

[0077] 3. Sensing membrane

[0078] The sensing membrane in this disclosure comprises a catalyst for decomposing hydrogen molecules and tungsten oxide.

[0079] The sensing film can be a single layer containing a catalyst and tungsten oxide, or it can consist of a tungsten oxide layer containing tungsten oxide and a catalyst layer containing a catalyst, sequentially from the substrate side.

[0080] When the sensing membrane includes a tungsten oxide layer and a catalyst layer, the catalyst layer can be a continuous membrane or a discontinuous membrane.

[0081] As a catalyst, there are no particular limitations as long as it can decompose hydrogen molecules into hydrogen ions (protons), and noble metals such as palladium, platinum, and iridium can be cited as examples. A single catalyst can be used, or two or more catalysts can be used in combination.

[0082] Tungsten oxide is tungsten trioxide (WO3).

[0083] The sensing film only needs to be connected to a pair of electrodes, and the position of the sensing film is not particularly limited. For example, a pair of electrodes and a sensing film can be disposed sequentially on the first surface of the substrate, or a sensing film and a pair of electrodes can be disposed sequentially on the first surface of the substrate.

[0084] When the sensing membrane is a single layer containing a catalyst and tungsten oxide, there is no particular limitation on the thickness of the sensing membrane as long as it is thick enough to detect changes in the resistance value of the sensing membrane, for example, 100 nm or more and 3000 nm or less.

[0085] On the other hand, when the sensing film comprises a tungsten oxide layer and a catalyst layer, the thickness of the tungsten oxide layer is not particularly limited as long as it is thick enough to detect changes in the resistance value of the tungsten oxide layer; for example, it is 100 nm or more and 3000 nm or less. Furthermore, the thickness of the catalyst layer is appropriately selected depending on the method of forming the catalyst layer. When the catalyst layer is formed by vapor deposition, the thickness of the catalyst layer is, for example, 1 nm or more and 10 nm or less. On the other hand, when the catalyst layer is formed by coating, the thickness of the catalyst layer is, for example, 10 nm or more and 100 nm or less.

[0086] The top-view area of ​​the sensing film is not particularly limited, for example, it can be 1 cm². 2 Above and 9cm 2 the following.

[0087] When the sensing membrane is a monolayer containing a catalyst and tungsten oxide, a sol-gel method can be cited as an example of a method for forming the sensing membrane. For example, Japanese Patent No. 5152797 and Japanese Patent No. 5540248 can be consulted for methods of forming sensing membranes based on the sol-gel method.

[0088] On the other hand, when the sensing film includes a tungsten oxide layer and a catalyst layer, the method for forming the tungsten oxide layer is not particularly limited, and examples include sol-gel method, vacuum evaporation method, sputtering method, and ion plating method. The method for forming the catalyst layer is also not particularly limited, and examples include evaporation methods such as vacuum evaporation method, sputtering method, and ion plating method, as well as coating method using a resin composition containing a catalyst and a binder resin.

[0089] 4. A pair of electrodes

[0090] In this disclosure, a pair of electrodes are disposed grounded on a first surface of a substrate. The pair of electrodes are typically disposed with a gap between them that allows the change in the resistance value of the sensing film to be detected. In this specification, "the gap that allows the change in the resistance value of the sensing film to be detected" refers to the gap between the electrodes that allows a short circuit when the resistance value of the sensing film decreases due to the aforementioned reduction reaction of tungsten oxide.

[0091] The pair of electrodes is preferably a pair of comb-tooth electrodes. Specifically, as shown in the figure... Figure 5As shown, preferably, a pair of electrodes 4a and 4b includes multiple first sensor electrodes 11 and multiple second sensor electrodes 12, as well as a first bus electrode 13 connected to the first sensor electrodes 11 and a second bus electrode 14 connected to the second sensor electrodes 12. The multiple first sensor electrodes and multiple second sensor electrodes are disposed on a first surface of the substrate and grounded to the sensing film, and are alternately arranged at intervals that allow for the detection of changes in the resistance value of the sensing film. Electrode 4a includes multiple first sensor electrodes 11 and a first bus electrode 13 connected to the first sensor electrodes 11. Furthermore, electrode 4b includes multiple second sensor electrodes 12 and a second bus electrode 14 connected to the second sensor electrodes 12.

[0092] Examples of conductive materials used for the pair of electrodes include carbon and metallic materials. Carbon is preferred because it is inert to hydrogen and inexpensive. As described above, when a sensing film and a pair of electrodes are sequentially disposed on the first surface of a substrate, the conductive material used for the pair of electrodes is preferably inert to hydrogen. On the other hand, when a pair of electrodes and a sensing film are sequentially disposed on the first surface of a substrate, the conductive material used for the pair of electrodes is not exposed to hydrogen, and therefore can be either active or inert to hydrogen.

[0093] There is no particular limitation on the thickness of a pair of electrodes, as long as it is sufficient to function as an electrode, such as being between 0.1 μm and 2 μm.

[0094] There are no particular limitations on the method for forming a pair of electrodes; examples include methods for forming and patterning a conductive film, mask evaporation, and printing. Examples of methods for forming a conductive film include vacuum evaporation, sputtering, ion plating, and deposition. Examples of patterning methods include etching and stripping.

[0095] The following three examples illustrate three different approaches for a pair of electrodes.

[0096] (1) First method

[0097] In this pair of electrodes, a first bus electrode and a second bus electrode are configured as a line that can be drawn in one stroke, and one end of the first bus electrode and one end of the second bus electrode are connected to the aforementioned IC tag.

[0098] exist Figure 6 as well as Figure 7 In this configuration, the first bus electrode 13 and the second bus electrode 14 are arranged as lines that can be drawn in one stroke. Specifically, the first bus electrode 13 and the second bus electrode 14 are arranged as meandering lines. Figure 6 In this configuration, one end of the first bus electrode 13 and one end of the second bus electrode 14 are connected to the IC tag 5. Figure 7In the first IC tag 5a, one end of the first bus electrode 13 and one end of the second bus electrode 14 are connected to the first IC tag 5a, and the other end of the first bus electrode 13 and the other end of the second bus electrode 14 are connected to the second IC tag 5b.

[0099] The spacing between the first sensor electrode and the second sensor electrode can be any spacing sufficient to detect changes in the resistance of the sensing membrane. This spacing can be, for example, 100 μm or more, or 500 μm or more. As mentioned above, if the spacing is narrowed, the resistance between the sensor terminals when the hydrogen concentration is zero tends to decrease. Therefore, if the spacing is too narrow, the resistance between the sensor terminals when the hydrogen concentration is zero may be lower than the first threshold resistance value. Furthermore, the spacing can be, for example, 10 mm or less, or 5 mm or less. As mentioned above, if the spacing is widened, the resistance between the sensor terminals when the hydrogen concentration is a set value tends to increase. Therefore, if the spacing is too wide, the resistance between the sensor terminals when the hydrogen concentration is a set value may be higher than the second threshold resistance value. That is, the spacing can be, for example, 100 μm or more and 10 mm or less, or 500 μm or more and 5 mm or less.

[0100] The spacing between the first sensor electrode and the second sensor electrode refers to the distance from the end of the adjacent first sensor electrode to the end of the second sensor electrode. For example, in... Figure 6 In the diagram, the interval between the first sensor electrode 11 and the second sensor electrode 12 is represented by the shortest distance d1 of the line connecting the adjacent first sensor electrode 11 and the second sensor electrode 12.

[0101] The widths of the first and second sensor electrodes are only required to detect changes in the resistance of the sensing film. For example, the width can be 100 μm or more, or 500 μm or more. Alternatively, the width can be 10 mm or less, or 5 mm or less. That is, the width can be 100 μm or more and 10 mm or less, or 500 μm or more and 5 mm or less. For example, in... Figure 6 In this design, the width of the first sensor electrode 11 is represented by the length b1 of a direction orthogonal to the direction in which the first sensor electrode 11 extends. Similarly, the width of the second sensor electrode 12 is represented by the length b2 of a direction orthogonal to the direction in which the second sensor electrode 12 extends.

[0102] The lengths of the first and second sensor electrodes can be any length sufficient to detect changes in the resistance of the sensing film. For example, the length can be 10 mm or more, or 50 mm or more. Furthermore, the length can be 500 mm or less, or 100 mm or less. That is, the length can be 10 mm or more and 500 mm or less, or 50 mm or more and 100 mm or less. For example, in... Figure 6 In this diagram, the length of the first sensor electrode 11 is represented by the length a1 in the direction in which the first sensor electrode 11 extends. Furthermore, the length of the second sensor electrode 12 is represented by the length a2 in the direction in which the second sensor electrode 12 extends.

[0103] The overlap length of the first sensor electrode and the second sensor electrode can be any length sufficient to detect changes in the resistance of the sensing film. This overlap length can be, for example, 9 mm or more, or 45 mm or more. Furthermore, the overlap length can be, for example, 450 mm or less, or 90 mm or less. That is, the overlap length can be, for example, 9 mm or more and 450 mm or less, or 45 mm or more and 90 mm or less. For example, in... Figure 6 In the figure, the overlap length of the first sensor electrode 11 and the second sensor electrode 12 is represented by the length c of the portion of the first sensor electrode 11 and the second sensor electrode 12 that are opposite each other in the direction in which the first sensor electrode 11 and the second sensor electrode 12 extend.

[0104] The number of the first sensor electrode and the number of the second sensor electrode are appropriately set according to the size of the hydrogen sensor, the configuration of the first bus electrode, and the configuration of the second bus electrode.

[0105] The shapes of the first and second sensor electrodes are not particularly limited; for example, they can be straight, broken, or curved. For example, in... Figure 6 In the design, the first sensor electrode 11 and the second sensor electrode 12 are linear in shape. Furthermore, for example in... Figure 8 In the process, the first sensor electrode 11 has a straight line shape and a broken line shape, and the second sensor electrode 12 has a straight line shape.

[0106] The first bus electrode and the second bus electrode are configured as lines that can be drawn in one stroke. In this specification, "lines that can be drawn in one stroke" means a continuous line that does not have overlapping sections.

[0107] As long as the first bus electrode, second bus electrode, first sensor electrode, and second sensor electrode can be integrally disposed on the first surface of the substrate, there are no particular limitations, as long as they can be drawn as a single line. For example, examples include... Figure 6 as well as Figure 7 The winding line shown Figure 8 The design features a vortex-like pattern as shown. Preferably, the first and second bus electrodes are configured as meandering lines. In this configuration, the first and second bus electrodes can be formed using a roll-to-roll method, thus enabling efficient mass production of hydrogen sensors.

[0108] Since the multiple first sensor electrodes connected to the first bus electrode and the multiple second sensor electrodes connected to the second bus electrode are alternately arranged, the first bus electrode and the second bus electrode are configured to be aligned with each other.

[0109] The width of the first bus electrode and the width of the second bus electrode can be any width sufficient to function as electrodes. For example, the width can be 1 mm or more, or 5 mm or more. Furthermore, the width can be 50 mm or less, or 10 mm or less. That is, the width can be 1 mm or more and 50 mm or less, or 5 mm or more and 10 mm or less. For example, in... Figure 6 In this configuration, the width of the first bus electrode 13 is represented by the length e1 of a direction orthogonal to the direction in which the first bus electrode 13 extends. Similarly, the width of the second bus electrode 14 is represented by the length e2 of a direction orthogonal to the direction in which the second bus electrode 14 extends.

[0110] The spacing between the first bus electrode and the second bus electrode, which are positioned opposite each other and sandwich the first sensor electrode and the second sensor electrode, is only required to allow for proper configuration of the first sensor electrode and the second sensor electrode. This spacing can be, for example, 11 mm or more, or 55 mm or more. Furthermore, the spacing can be, for example, 550 mm or less, or 110 mm or less. That is, the spacing can be, for example, 11 mm or more and 550 mm or less, or 55 mm or more and 110 mm or less. For example, in... Figure 6 In the diagram, the distance between the first bus electrode 13 and the second bus electrode 14, which are positioned opposite each other and sandwiching the first sensor electrode 11 and the second sensor electrode 12, is represented by the shortest distance f of the line connecting the first bus electrode 13 and the second bus electrode 14, which are positioned opposite each other and sandwiching the first sensor electrode 11 and the second sensor electrode 12.

[0111] The spacing between the first and second bus electrodes, which are opposite each other without sandwiching the first and second sensor electrodes, is sufficient to prevent the detection of changes in the resistance value of the sensing film. This spacing can be, for example, 10 mm or more, or 50 mm or more. Alternatively, it can be, for example, 100 mm or less, or 70 mm or less. That is, the spacing can be, for example, 10 mm or more and 100 mm or less, or 50 mm or more and 70 mm or less. If the spacing is too small, the aforementioned tungsten oxide reduction reaction will occur, and when the resistance value of the sensing film decreases, there is a possibility that the first and second bus electrodes, which are opposite each other without sandwiching the first and second sensor electrodes, may easily conduct. The spacing can be appropriately selected based on the thickness of the sensing film. There is a tendency that if the thickness of the sensing film increases, the first and second bus electrodes, which are opposite each other without sandwiching the first and second sensor electrodes, will be difficult to short-circuit. Therefore, when the thickness of the sensing film is relatively thick, the spacing can be relatively small within the aforementioned range. On the other hand, if the thickness of the sensing film becomes thinner, the first bus electrode and the second bus electrode, which are not sandwiched between the first sensor electrode and the second sensor electrode, are prone to short-circuiting. Therefore, when the thickness of the sensing film is relatively thin, it is preferable that the above-mentioned spacing is relatively large within the above-mentioned range. For example, in Figure 6 In the diagram, the distance between the first bus electrode 13 and the second bus electrode 14, which are opposite each other without clamping the first sensor electrode 11 and the second sensor electrode 12, is represented by the shortest distance g of the line connecting the first bus electrode 13 and the second bus electrode 14, which are opposite each other without clamping the first sensor electrode 11 and the second sensor electrode 12.

[0112] The spacing between adjacent first bus electrodes and the spacing between adjacent second bus electrodes can be such that changes in the resistance of the sensing film cannot be detected. This spacing can be, for example, 10 mm or more, or 50 mm or more. Alternatively, it can be, for example, 100 mm or less, or 70 mm or less. That is, the spacing can be, for example, 10 mm or more and 100 mm or less, or 50 mm or more and 70 mm or less. If the spacing is too small, the reduction reaction of tungsten oxide occurs, and when the resistance of the sensing film decreases, adjacent first bus electrodes or adjacent second bus electrodes may easily become conductive. The spacing can be appropriately selected based on the thickness of the sensing film. There is a tendency that if the thickness of the sensing film increases, it becomes difficult for adjacent first bus electrodes or adjacent second bus electrodes to short-circuit. Therefore, when the thickness of the sensing film is relatively thick, the spacing can be relatively small within the aforementioned range. On the other hand, there is a tendency that if the thickness of the sensing film decreases, adjacent first bus electrodes or adjacent second bus electrodes are easily short-circuited. Therefore, when the thickness of the sensing film is relatively thin, it is preferable that the spacing be relatively large within the aforementioned range. For example in Figure 6 In this configuration, the spacing between adjacent first bus electrodes 13 is represented by the shortest distance h1 of the line connecting adjacent first bus electrodes 13. Furthermore, the spacing between adjacent second bus electrodes 14 is represented by the shortest distance h2 of the line connecting adjacent second bus electrodes 14.

[0113] In this method, the number of first bus electrodes and the number of second bus electrodes are typically one. Alternatively, as long as the first and second bus electrodes form a pair, the number of first bus electrodes and the number of second bus electrodes can also be two. For example, in... Figure 9 In the hydrogen sensor 1, there are two first bus electrodes 13a and 13b and two second bus electrodes 14a and 14b. The first bus electrode 13a and the second bus electrode 14a are a pair, and the first bus electrode 13b and the second bus electrode 14b are a pair.

[0114] (2) Second method

[0115] In this method, multiple first bus electrodes and multiple second bus electrodes are connected to the IC tag via a flexible printed circuit board.

[0116] exist Figure 10 In this configuration, multiple first bus electrodes 13 and multiple second bus electrodes 14 are connected to the IC tag 5 via a flexible printed circuit board 9. Figure 11 In the process, one end of multiple first bus electrodes 13 and one end of multiple second bus electrodes 14 are connected to the first IC tag 5a via a flexible printed circuit board 9, and the other end of multiple first bus electrodes 13 and the other end of multiple second bus electrodes 14 are connected to the second IC tag 5b via the flexible printed circuit board 9.

[0117] In this method, since the first bus electrode and the second bus electrode can be configured in a straight line, the risk of wire breakage can be reduced.

[0118] The spacing between the first sensor electrode and the second sensor electrode can be any spacing sufficient to detect changes in the resistance of the sensing membrane. This spacing can be, for example, 100 μm or more, or 500 μm or more. As mentioned above, if the spacing is narrowed, the resistance between the sensor terminals when the hydrogen concentration is zero tends to decrease. Therefore, if the spacing is too narrow, the resistance between the sensor terminals when the hydrogen concentration is zero may be lower than the first threshold resistance value. Furthermore, the spacing can be, for example, 10 mm or less, or 5 mm or less. As mentioned above, if the spacing is widened, the resistance between the sensor terminals when the hydrogen concentration is a set value tends to increase. Therefore, if the spacing is too wide, the resistance between the sensor terminals when the hydrogen concentration is a set value may be higher than the second threshold resistance value. That is, the spacing can be, for example, 100 μm or more and 10 mm or less, or 500 μm or more and 5 mm or less.

[0119] The spacing between the first sensor electrode and the second sensor electrode refers to the distance from the end of the adjacent first sensor electrode to the end of the second sensor electrode. For example, in... Figure 10 In the diagram, the interval between the first sensor electrode 11 and the second sensor electrode 12 is represented by the shortest distance d1 of the line connecting the adjacent first sensor electrode 11 and the second sensor electrode 12.

[0120] The widths of the first and second sensor electrodes are only required to detect changes in the resistance of the sensing film. For example, the width can be 100 μm or more, or 500 μm or more. Alternatively, the width can be 10 mm or less, or 5 mm or less. That is, the width can be 100 μm or more and 10 mm or less, or 500 μm or more and 5 mm or less. For example, in... Figure 10 In this design, the width of the first sensor electrode 11 is represented by the length b1 of a direction orthogonal to the direction in which the first sensor electrode 11 extends. Similarly, the width of the second sensor electrode 12 is represented by the length b2 of a direction orthogonal to the direction in which the second sensor electrode 12 extends.

[0121] The lengths of the first and second sensor electrodes can be any length sufficient to detect changes in the resistance of the sensing film. For example, the length can be 10 mm or more, or 50 mm or more. Furthermore, the length can be 500 mm or less, or 100 mm or less. That is, the length can be 10 mm or more and 500 mm or less, or 50 mm or more and 100 mm or less. For example, in... Figure 10 In this diagram, the length of the first sensor electrode 11 is represented by the length a1 in the direction in which the first sensor electrode 11 extends. Furthermore, the length of the second sensor electrode 12 is represented by the length a2 in the direction in which the second sensor electrode 12 extends.

[0122] The overlap length of the first sensor electrode and the second sensor electrode can be any length sufficient to detect changes in the resistance of the sensing film. This overlap length can be, for example, 9 mm or more, or 45 mm or more. Furthermore, the overlap length can be, for example, 450 mm or less, or 90 mm or less. That is, the overlap length can be, for example, 9 mm or more and 450 mm or less, or 45 mm or more and 90 mm or less. For example, in... Figure 10 In the above, the overlap length of the first sensor electrode 11 and the second sensor electrode 12 is represented by the length c of the opposite portions of the first sensor electrode 11 and the second sensor electrode 12 in the direction in which the first sensor electrode 11 and the second sensor electrode 12 extend.

[0123] The number of the first sensor electrode and the number of the second sensor electrode are appropriately set according to the size of the hydrogen sensor, the configuration of the first bus electrode, and the configuration of the second bus electrode.

[0124] The shapes of the first sensor electrode and the second sensor electrode are not particularly limited; for example, they can be straight, broken, or curved.

[0125] The first bus electrode and the second bus electrode are a pair, and are configured alternately.

[0126] The width of the first bus electrode and the width of the second bus electrode can be any width sufficient to function as electrodes. For example, the width can be 1 mm or more, or 5 mm or more. Alternatively, the width can be 50 mm or less, or 10 mm or less. That is, the width can be 1 mm or more and 50 mm or less, or 5 mm or more and 10 mm or less. For example, in... Figure 10 In this configuration, the width of the first bus electrode 13 is represented by the length e1 of a direction orthogonal to the direction in which the first bus electrode 13 extends. Similarly, the width of the second bus electrode 14 is represented by the length e2 of a direction orthogonal to the direction in which the second bus electrode 14 extends.

[0127] The spacing between the first bus electrode and the second bus electrode is only required to allow for the configuration of the first sensor electrode and the second sensor electrode. This spacing can be, for example, 11 mm or more, or 55 mm or more. Furthermore, the spacing can be, for example, 550 mm or less, or 110 mm or less. That is, the spacing can be, for example, 11 mm or more and 550 mm or less, or 55 mm or more and 110 mm or less. For example, in... Figure 10 In the diagram, the spacing between the first bus electrode 13 and the second bus electrode 14 is represented by the shortest distance f of the line connecting the first bus electrode 13 and the second bus electrode 14, which are positioned opposite each other and sandwich the first sensor electrode 11 and the second sensor electrode 12.

[0128] The number of first bus electrodes and the number of second bus electrodes can be multiple. The first bus electrodes and the second bus electrodes can be a pair; the number of first bus electrodes and the number of second bus electrodes can be the same or different. For example, in... Figure 10 In the first bus electrode 13, there are four electrodes, and in the second bus electrode 14, there are five electrodes. The number of electrodes in the first bus electrode is different from the number of electrodes in the second bus electrode.

[0129] Multiple first bus electrodes and multiple second bus electrodes are connected to the IC tag via a flexible printed circuit board (FPC). A standard FPC can be used as the FPC.

[0130] (3) Third method

[0131] In this configuration, a pair of electrodes comprises multiple first bus electrodes arranged along a first direction, and multiple second bus electrodes arranged along a second direction orthogonal to the first direction. In this configuration, the IC tag includes a third IC tag connected to one end of the multiple first bus electrodes and a fourth IC tag connected to one end of the multiple second bus electrodes. An insulating film is disposed between the first bus electrodes and the second bus electrodes in the region where they intersect.

[0132] exist Figure 12 In this configuration, multiple first bus electrodes 13 are arranged linearly along a first direction D1, and multiple second bus electrodes 14 are arranged linearly along a second direction D2 orthogonal to the first direction D1. The IC tag includes a third IC tag 5c connected to one end of each of the multiple first bus electrodes 13 and a fourth IC tag 5d connected to one end of each of the multiple second bus electrodes 14. An insulating film 15 is disposed between the first bus electrodes 13 and the second bus electrodes 14 in the region where they intersect.

[0133] In this method, it is not necessary to configure the first and second bus electrodes as lines that can be drawn in one stroke, thus reducing the risk of line breakage. Furthermore, as... Figure 12 As shown, the area of ​​the overlapping portion 10C of the first sensor electrode 11 and the second sensor electrode 12 can be kept constant, thus reducing signal deviation and improving detection sensitivity.

[0134] The spacing between the first sensor electrode and the second sensor electrode can be any spacing sufficient to detect changes in the resistance of the sensing membrane. This spacing can be, for example, 100 μm or more, or 500 μm or more. As mentioned above, if the spacing is narrowed, the resistance between the sensor terminals when the hydrogen concentration is zero tends to decrease. Therefore, if the spacing is too narrow, the resistance between the sensor terminals when the hydrogen concentration is zero may be lower than the first threshold resistance value. Furthermore, the spacing can be, for example, 10 mm or less, or 5 mm or less. As mentioned above, if the spacing is widened, the resistance between the sensor terminals when the hydrogen concentration is a set value tends to increase. Therefore, if the spacing is too wide, the resistance between the sensor terminals when the hydrogen concentration is a set value may be higher than the second threshold resistance value. That is, the spacing can be, for example, 100 μm or more and 10 mm or less, or 500 μm or more and 5 mm or less.

[0135] The spacing between the first sensor electrode and the second sensor electrode refers to the distance from the end of the adjacent first sensor electrode to the end of the second sensor electrode. For example, in... Figure 12 In the diagram, the interval between the first sensor electrode 11 and the second sensor electrode 12 is represented by the shortest distance d1 of the line connecting the adjacent first sensor electrode 11 and the second sensor electrode 12.

[0136] The widths of the first and second sensor electrodes are only required to detect changes in the resistance of the sensing film. For example, the width can be 100 μm or more, or 500 μm or more. Alternatively, the width can be 10 mm or less, or 5 mm or less. That is, the width can be 100 μm or more and 10 mm or less, or 500 μm or more and 5 mm or less. For example, in... Figure 12 In this design, the width of the first sensor electrode 11 is represented by the length b1 of a direction orthogonal to the direction in which the first sensor electrode 11 extends. Similarly, the width of the second sensor electrode 12 is represented by the length b2 of a direction orthogonal to the direction in which the second sensor electrode 12 extends.

[0137] The lengths of the first and second sensor electrodes can be any length sufficient to detect changes in the resistance of the sensing film. For example, the length can be 10 mm or more, or 50 mm or more. Furthermore, the length can be 500 mm or less, or 100 mm or less. That is, the length can be 10 mm or more and 500 mm or less, or 50 mm or more and 100 mm or less. For example, in... Figure 12 In this diagram, the length of the first sensor electrode 11 is represented by the length a1 in the direction in which the first sensor electrode 11 extends. Furthermore, the length of the second sensor electrode 12 is represented by the length a2 in the direction in which the second sensor electrode 12 extends.

[0138] The overlap length of the first sensor electrode and the second sensor electrode can be any length sufficient to detect changes in the resistance of the sensing film. This overlap length can be, for example, 9 mm or more, or 45 mm or more. Furthermore, the overlap length can be, for example, 450 mm or less, or 90 mm or less. That is, the overlap length can be, for example, 9 mm or more and 450 mm or less, or 45 mm or more and 90 mm or less. For example, in... Figure 12 In the figure, the overlap length of the first sensor electrode 11 and the second sensor electrode 12 is represented by the length c of the portion of the first sensor electrode 11 and the second sensor electrode 12 that are opposite each other in the direction in which the first sensor electrode 11 and the second sensor electrode 12 extend.

[0139] The number of the first sensor electrode and the number of the second sensor electrode are appropriately set according to the size of the hydrogen sensor, the configuration of the first bus electrode, and the configuration of the second bus electrode.

[0140] The shapes of the first and second sensor electrodes are not particularly limited; for example, they can be straight, broken, or curved. Furthermore, the shapes of the first and second sensor electrodes can also be branched. For example, in... Figure 12 In this configuration, the first sensor electrode 11 is linear in shape, while the second sensor electrode 12 is branched. Furthermore, for example in... Figure 13 In the first sensor electrode 11, the shape is straight, and the shape of the second sensor electrode 12 is broken.

[0141] Multiple first bus electrodes are arranged along a first direction, and multiple second bus electrodes are arranged along a second direction orthogonal to the first direction.

[0142] The width of the first bus electrode and the width of the second bus electrode can be any width sufficient to function as electrodes. For example, the width can be 1 mm or more, or 5 mm or more. Furthermore, the width can be 50 mm or less, or 10 mm or less. That is, the width can be 1 mm or more and 50 mm or less, or 5 mm or more and 10 mm or less. For example, in... Figure 12 In this configuration, the width of the first bus electrode 13 is represented by the length e1 of a direction orthogonal to the direction in which the first bus electrode 13 extends. Similarly, the width of the second bus electrode 14 is represented by the length e2 of a direction orthogonal to the direction in which the second bus electrode 14 extends.

[0143] The spacing between adjacent first bus electrodes and the spacing between adjacent second bus electrodes are only required to allow for the configuration of the first and second sensor electrodes. For example, the spacing can be 11 mm or more, or 55 mm or more. Furthermore, the spacing can be 550 mm or less, or 110 mm or less. That is, the spacing can be 11 mm or more and 550 mm or less, or 55 mm or more and 110 mm or less. For example, in... Figure 12 In this configuration, the spacing between adjacent first bus electrodes 13 is represented by the shortest distance k1 of the line connecting adjacent first bus electrodes 13. Furthermore, the spacing between adjacent second bus electrodes 14 is represented by the shortest distance k2 of the line connecting adjacent second bus electrodes 14.

[0144] The number of first bus electrodes and the number of second bus electrodes are multiple.

[0145] In this method, an insulating film is disposed between the first and second bus electrodes in the region where they intersect. The material of the insulating film is not particularly limited as long as it is insulating; examples include inorganic oxides, inorganic nitrides, inorganic carbides, and resins. The thickness of the insulating film is not particularly limited as long as it is sufficient to insulate the first and second bus electrodes; for example, it is 0.1 μm or more and 2 μm or less. The method for forming the insulating film is not particularly limited; examples include methods for forming and patterning the insulating film, mask evaporation, and printing. Examples of methods for forming the insulating film include vacuum evaporation, sputtering, ion plating, and deposition. Examples of patterning methods include etching and stripping.

[0146] In this approach, regarding the position of the sensing film, for example, the first sensor electrode, the second sensor electrode, and the sensing film can be sequentially arranged on the first surface of the substrate; the sensing film, the first sensor electrode, and the second sensor electrode can be sequentially arranged on the first surface of the substrate; the first sensor electrode, the sensing film, and the second sensor electrode can be sequentially arranged on the first surface of the substrate; or the second sensor electrode, the sensing film, and the first sensor electrode can be sequentially arranged on the first surface of the substrate.

[0147] In this embodiment, the IC tag includes a third IC tag connected to one end of a plurality of first bus electrodes and a fourth IC tag connected to one end of a plurality of second bus electrodes. Alternatively, the IC tag may include the aforementioned third IC tag, fourth IC tag, and a fifth IC tag connected to the other end of the plurality of first bus electrodes. Alternatively, the IC tag may include the aforementioned third IC tag, fourth IC tag, and a sixth IC tag connected to the other end of the plurality of second bus electrodes. Alternatively, the IC tag may include the aforementioned third IC tag, fourth IC tag, fifth IC tag, and sixth IC tag. For example, in... Figure 14 In the IC tag, there is a third IC tag 5c connected to one end of the plurality of first bus electrodes 13, a fourth IC tag 5d connected to one end of the plurality of second bus electrodes 14, and a fifth IC tag 5e connected to the other end of the plurality of first bus electrodes 13.

[0148] 5.Substrate

[0149] The substrate in this disclosure is a component that supports the sensing film and a pair of electrodes and has insulating properties.

[0150] The substrate only needs to be insulating and there are no particular limitations. Examples include glass substrates, resin substrates, ceramic substrates, and silicon substrates with an insulating film on the surface.

[0151] There is no particular limitation on the thickness of the substrate, for example, it can be 10μm or more and 2mm or less.

[0152] 6. Other structures

[0153] In this disclosure, it is sufficient to provide the aforementioned sensing film and a pair of electrodes on the first surface of the substrate. Alternatively, the sensing film and a pair of electrodes may be provided on only one side of the substrate, or they may be provided on both sides of the substrate respectively.

[0154] B. Hydrogen Detection System

[0155] The hydrogen detection system in this disclosure uses the hydrogen sensor described above.

[0156] Figure 15 This is a schematic diagram illustrating an example of a hydrogen detection system according to this disclosure. Figure 15 In this system, the hydrogen detection system 30 includes multiple hydrogen sensors 1, an RFID reader 31, and multiple antennas 32 connected to the RFID reader 31. The hydrogen sensors 1 are installed in an underground hydrogen pipeline 41. The RFID reader 31 and antennas 32 are fixed and can be placed anywhere near the ground.

[0157] Figure 16This is a schematic diagram illustrating another example of a hydrogen detection system in this disclosure. Figure 16 In this system, the hydrogen detection system 30 includes multiple hydrogen sensors 1, an RFID reader 31, and an antenna 32 connected to the RFID reader 31. The hydrogen sensors 1 are installed in an underground hydrogen pipeline 41. The RFID reader 31 and the antenna 32 are mounted on a mobile body 33, making it mobile.

[0158] Figure 17 This is a schematic diagram illustrating another example of a hydrogen detection system in this disclosure. Figure 17 In this system, the hydrogen detection system 30 is used in a hydrogen refueling station. The hydrogen detection system 30 includes multiple hydrogen sensors 1, an RFID reader 31, and an antenna 32 connected to the RFID reader 31. The hydrogen sensors 1 are installed in a distributor 42 that supplies hydrogen to vehicles, etc. The RFID reader 31 and the antenna 32 are fixedly mounted on a top cover (roof) 43.

[0159] In such a hydrogen detection system, the IC chip of the IC tag that constitutes the hydrogen sensor can be driven in a non-contact manner to detect changes in the resistance value of the sensing membrane, thereby detecting hydrogen gas.

[0160] The hydrogen detection system disclosed herein is not particularly limited to any system using a hydrogen sensor, but is preferably a system using RFID. Specifically, the hydrogen detection system disclosed herein includes a hydrogen sensor, an RFID reader / writer, and an antenna connected to the RFID reader / writer.

[0161] RFID readers can be fixed or mobile. Fixed RFID readers allow for continuous monitoring. Mobile RFID readers, on the other hand, enable tracking and inspection, achieving a high degree of automation, intelligence, and reduced manpower requirements.

[0162] The hydrogen detection system disclosed herein can be used not only in small devices such as fuel cells, but also in large devices such as hydrogen production facilities, hydrogen pipelines, transport tankers, storage tanks, hydrogen power generation facilities, and hydrogen refueling stations. As for hydrogen pipelines, in addition to underground pipelines, aerial pipelines can also be used.

[0163] Furthermore, this disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any technical concept that has a structure that is substantially the same as the technical concept described in the claims of this disclosure and achieves the same effect is included within the technical scope of this disclosure.

[0164] Example

[0165] The present disclosure is further illustrated below with examples and comparative examples.

[0166] [Example 1]

[0167] A pair of electrodes was formed on a 100 μm thick polyethylene terephthalate (PET) film using a printing method. In the pair of electrodes, the lengths a1 and a2 of the first and second sensor electrodes are both 5 mm, the widths b1 and b2 of the first and second sensor electrodes are both 0.5 mm, the spacing d1 between the first and second sensor electrodes is 0.5 mm, and the widths e1 and e2 of the first and second bus electrodes are both 0.5 mm. Furthermore, the thickness of the pair of electrodes is 0.15 μm.

[0168] Next, referring to Tomoji Ohishi et al., Materials Sciences and Applications, “Low-Temperature Formation of a WO3 Thin Film by the Sol-Gel Method Using to-Irradiation and Fabrication of a Flexible Hydrogen Sensor”, 2020, 11, pp. 135-149, a sensing film was formed on the aforementioned PET film using a sol-gel method to cover a pair of electrodes. Specifically, tungsten hexachloride (WCl6) manufactured by Sigma-Aldrich was used as the raw material for tungsten oxide, palladium acetate (II) manufactured by Kanto Chemical Co., Ltd. was used as the catalyst, and polystyrene (degree of polymerization 2000) manufactured by Wako Pure Chemical Co., Ltd. was used as the resin binder. The aforementioned tungsten oxide raw material was dissolved in ethanol and coated onto the aforementioned PET film to form a precursor film. Next, the precursor film was irradiated at 100°C with wavelengths of 254 nm and 185 nm and an illuminance of 12 mW / cm². 2 The ultraviolet light was applied for 20 minutes. Next, the above catalyst was added to a 10 wt% polystyrene toluene solution to prepare a 1 wt% Pd-containing solution. This Pd-containing solution was coated onto the precursor film and heated at 100°C for 10 minutes. The sensing film, from the PET film side, sequentially comprises a tungsten oxide layer and a catalyst layer, with the tungsten oxide layer having a thickness of 600 nm and the catalyst layer having a thickness of 90 nm.

[0169] Next, an IC tag containing an IC chip (NXP's UCODEG2iM+) and an antenna was fabricated. Specifically, copper foil was laminated onto a glass epoxy substrate and patterned according to a design drawing to form the antenna. The copper foil was patterned by etching or cutting with a grinder. Next, the aforementioned IC chip was installed to connect the antenna terminals and the antenna, thus fabricating the IC tag. The antenna was designed to be sensitive to UHF frequency waves. Finally, the IC tag was attached to a pair of electrodes to obtain the hydrogen sensor.

[0170] [Comparative Example 1]

[0171] The hydrogen sensor was fabricated in the same manner as in Example 1, except that the thickness of the tungsten oxide layer was set to 1.5 μm.

[0172] [Comparative Example 2]

[0173] Except that the distance d1 between the first sensor electrode and the second sensor electrode is set to 1.0 mm, the hydrogen sensor is fabricated in the same manner as in Example 1.

[0174] [evaluate]

[0175] It was confirmed that a UHF band RFID reader could be used to send readout waves to the hydrogen sensor of Example 1 and detect the reflected waves. Furthermore, while exposing the hydrogen sensor to hydrogen gas and sending waves in the same manner as described above, the signal level of the reflected waves changed. Thus, it was confirmed that hydrogen gas can be detected without a power source being installed on the hydrogen sensor itself.

[0176] Furthermore, the resistance value between the sensor terminals of the hydrogen sensor at a given hydrogen concentration was determined using the following method. First, the gas mixing device was connected to the sealed gas chamber via gas piping. The gas mixing device used was a GM-4B gas mixing device with an integrated flow meter, manufactured by Cofflock. The sealed gas chamber was a metal chamber with a glass window and rubber gaskets. The sealed gas chamber was cylindrical with a diameter of 100 mmφ and a height of 20 mm. Stainless steel fixed piping was used for the gas piping. The IC tag was removed from the hydrogen sensor, and the hydrogen sensor was sealed inside the sealed gas chamber connected to the gas mixing device. An LCR meter (Hiroki IM 3523) was connected to a pair of electrodes connected to a pair of sensor terminals on the IC tag. The LCR meter was installed outside the sealed gas chamber via electrical wiring and gaskets. The set temperature was set to 25°C. The target fluids were hydrogen and air. The flow rate of the hydrogen and air mixture was always set to 10 mL / min.

[0177] First, the hydrogen and air mixture ratio was set to 0% hydrogen and 100% air. Next, this hydrogen concentration was maintained for 10 minutes to achieve the desired hydrogen concentration within the sealed gas chamber. Then, the impedance was measured at 20kHz using an LCR meter (Hiroki IM 3523) for each pair of electrodes connected to a pair of sensors via terminals on the IC tag. The resistance between the electrodes was determined from the impedance readings. This measurement was performed five times, and the average of the three values ​​(excluding the maximum and minimum values) was taken as the resistance between the sensor terminals at the given hydrogen concentration.

[0178] When changing the hydrogen concentration and determining the resistance value between the terminals of the hydrogen sensor at a given hydrogen concentration, open the sealed gas chamber and maintain it for 10 minutes. After restoring the ambient air atmosphere, repeat the above operation.

[0179] The results of the hydrogen sensor in Example 1 are shown below. Figure 18 Furthermore, the results of the hydrogen sensors from Comparative Examples 1 to 2 are shown below. Figure 19 .

[0180] In Example 1, when the hydrogen concentration is 0.00005% (the hydrogen concentration in air), the resistance value between the sensor terminals is a first threshold resistance value T1 or higher; when the hydrogen concentration is a set value of 1%, the resistance value between the sensor terminals is a second threshold resistance value T2 or lower. On the other hand, in Comparative Example 1, because the thickness of the sensing film is increased, therefore... Figure 19 As shown, when the hydrogen concentration is the same as that in air (0.00005%), the resistance between the sensor terminals is lower than the first threshold resistance value T1. Furthermore, in Comparative Example 2, because the distance d1 between the first sensor electrode and the second sensor electrode was increased, as... Figure 19 As shown, when the hydrogen concentration is the set value of 1%, the resistance between the terminals of the sensor is higher than the second threshold resistance value T2.

[0181] -Explanation of Figure Markers-

[0182] 1 … Hydrogen sensor

[0183] 2…Substrate

[0184] 3 … Sensing membrane

[0185] 4a, 4b … A pair of electrodes

[0186] 5 … IC tag

[0187] 11 … First sensor electrode

[0188] 12 … Second sensor electrode

[0189] 13 … First bus electrode

[0190] 14 … Second bus electrode

[0191] 21 … Second substrate

[0192] 22 … IC chips

[0193] 23 … Antenna

[0194] 24a, 24b… Sensor terminals

[0195] 30 … Hydrogen detection system.

Claims

1. A hydrogen sensor, comprising: substrate; A sensing film, disposed on a first side of the substrate, includes a catalyst for decomposing hydrogen molecules and tungsten oxide; A pair of electrodes are grounded on the first surface of the substrate in relation to the sensing film; as well as An IC tag is connected to the pair of electrodes. The IC tag includes: an IC chip; an antenna connected to the IC chip; and a pair of sensor terminals connected to the IC chip and respectively connected to the pair of electrodes. The IC chip is an open-circuit / short-circuit type. It is determined to be in a high-resistance state when the resistance between the sensor terminals is above a first threshold resistance value, and in a low-resistance state when the resistance between the sensor terminals is below a second threshold resistance value, which is smaller than the first threshold resistance value. When the hydrogen concentration is zero, the resistance value between the terminals of the sensor becomes above the first threshold resistance value, and when the hydrogen concentration is a set value, the resistance value between the terminals of the sensor becomes below the second threshold resistance value.

2. The hydrogen sensor according to claim 1, wherein, The hydrogen concentration is set at 1% or more and less than 4%.

3. The hydrogen sensor according to claim 1, wherein, When the second threshold resistance value is set to 100%, the difference between the resistance value between the sensor terminals and the second threshold resistance value when the hydrogen concentration is the set value is more than 1% and less than 20% of the second threshold resistance value.

4. A hydrogen detection system, The hydrogen sensor according to any one of claims 1 to 3 was used.

5. A hydrogen pipeline, The hydrogen detection system described in claim 4 was used.

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