Ammonia sensors and ammonia detection systems

Abstract

We provide an ammonia sensor that can remotely detect ammonia. [Solution] An ammonia sensor comprising a substrate, a sensitive film disposed on the first surface of the substrate and containing a substance whose resistance changes upon contact with ammonia, a pair of electrodes disposed on the first surface of the substrate in contact with the sensitive film, and a communication unit connected to the pair of electrodes and having a detection unit for detecting changes in resistance.

Description

Technical Field

[0001] The present disclosure relates to an ammonia sensor and an ammonia detection system.

Background Art

[0002] Ammonia (NH3) is an industrially useful substance and is used in various applications. In recent years, from the viewpoints of global environmental protection and prevention of depletion of fossil fuels, it is desired to utilize clean and recyclable energy. In particular, research for using hydrogen gas as an energy source has been actively conducted mainly on fuel cells. Since ammonia contains hydrogen, it is expected to be used as a medium for hydrogen. Furthermore, research for using ammonia gas as an energy source has also been advanced.

[0003] However, ammonia is highly toxic and flammable. Therefore, various ammonia sensors have been developed conventionally. In order to ensure safety, it is desirable to detect ammonia leakage remotely.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present disclosure has been made in view of the above circumstances, and the main object thereof is to provide an ammonia sensor capable of remotely detecting ammonia.

Means for Solving the Problems

[0006] One embodiment of the present disclosure provides an ammonia sensor comprising: a substrate; a sensitive film disposed on a first surface of the substrate and containing a substance whose resistance changes upon contact with ammonia; a pair of electrodes disposed on the first surface of the substrate in contact with the sensitive film; and a communication unit connected to the pair of electrodes and having a detection unit for detecting changes in resistance.

[0007] Another embodiment of this disclosure provides an ammonia detection system using the ammonia sensor described above.

[0008] Another embodiment of this disclosure provides an ammonia pipeline using the ammonia detection system described above. [Effects of the Invention]

[0009] The ammonia sensor in this disclosure has the effect of being able to detect ammonia remotely. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic plan view illustrating an ammonia sensor in this disclosure. [Figure 2] This is a schematic plan view illustrating an ammonia sensor in this disclosure. [Figure 3] This is a schematic plan view illustrating an ammonia sensor in this disclosure. [Figure 4] This graph illustrates the relationship between ammonia concentration and the resistance value between the sensor terminals in the ammonia sensor described herein. [Figure 5] This graph illustrates the relationship between ammonia concentration and the resistance value between the sensor terminals in an ammonia sensor that does not have a specific IC tag. [Figure 6] This graph illustrates the relationship between ammonia concentration and the resistance value between the sensor terminals in the ammonia sensor described herein. [Figure 7] This graph illustrates the relationship between ammonia concentration and the resistance value between the sensor terminals in an ammonia sensor that does not have a specific IC tag. [Figure 8] It is a schematic plan view illustrating the ammonia sensor in the present disclosure. [Figure 9] It is a schematic plan view illustrating the ammonia sensor in the present disclosure. [Figure 10] It is a schematic plan view illustrating the ammonia sensor in the present disclosure. [Figure 11] It is a schematic plan view illustrating the ammonia sensor in the present disclosure. [Figure 12] It is a schematic plan view illustrating the ammonia sensor in the present disclosure. [Figure 13] It is a schematic plan view illustrating the ammonia sensor in the present disclosure. [Figure 14] It is a schematic plan view illustrating the ammonia sensor in the present disclosure. [Figure 15] It is a schematic plan view illustrating the ammonia sensor in the present disclosure. [Figure 16] It is a schematic plan view illustrating the ammonia sensor in the present disclosure. [Figure 17] It is a schematic plan view illustrating the ammonia sensor in the present disclosure. [Figure 18] It is a schematic diagram illustrating the ammonia detection system in the present disclosure. [Figure 19] It is a schematic diagram illustrating the ammonia detection system in the present disclosure. [Figure 20] It is a schematic diagram illustrating the ammonia detection system in the present disclosure. [Figure 21] It is a schematic diagram illustrating the ammonia detection system in the present disclosure.

Embodiments for Carrying out the Invention

[0011] Embodiments of this disclosure will be described below with reference to drawings and other figures. However, this disclosure can be implemented in many different ways and should not be interpreted as being limited to the embodiments described below. In addition, in order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each component compared to the embodiments, but these are merely examples and should not limit the interpretation of this disclosure. Furthermore, in this specification and each figure, elements similar to those described above with respect to previously shown figures will be denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

[0012] In this specification, when describing a configuration in which one member is placed on top of another member, the terms "on the surface side" or "on the surface" include, unless otherwise specified, both cases in which the other member is placed directly above or below the other member so as to be in contact with it, and cases in which the other member is placed above or below the other member via yet another member.

[0013] Furthermore, in this specification, terms such as "sheet," "film," and "board" are not distinguished from each other solely based on differences in name. For example, "sheet" is used to include components that may also be called films or boards.

[0014] The ammonia sensor and ammonia detection system described in this disclosure will be explained in detail below.

[0015] A. Ammonia sensor The ammonia sensor in this disclosure comprises a substrate, a sensitive film disposed on a first surface of the substrate and containing a substance whose resistance changes upon contact with ammonia, a pair of electrodes disposed on the first surface of the substrate in contact with the sensitive film, and a communication unit connected to the pair of electrodes and having a detection unit for detecting changes in resistance.

[0016] Figure 1 is a schematic plan view showing an example of an ammonia sensor in this disclosure. As shown in Figure 1, the ammonia sensor 1 includes a substrate 2, a sensitive film 3 disposed on the first surface of the substrate 2 and containing a substance whose resistance changes upon contact with ammonia, a pair of electrodes 4a and 4b disposed on the first surface of the substrate 2 in contact with the sensitive film 3, and a communication unit 5 connected to the pair of electrodes 4a and 4b and having a detection unit for detecting changes in resistance. In Figure 1, the pair of electrodes 4a and 4b are a pair of comb-tooth electrodes. The pair of electrodes 4a and 4b are arranged alternately with an interval d1 that allows for the detection of changes in the resistance of the sensitive film 3.

[0017] The ammonia sensor in this disclosure contains a substance whose resistance changes when it comes into contact with ammonia, and utilizes the fact that the resistance of the sensitive film changes when it comes into contact with ammonia.

[0018] Substances whose resistance changes upon contact with ammonia include two types: a first type whose resistance increases upon contact with ammonia, and a second type whose resistance decreases upon contact with ammonia.

[0019] First, the operating principle of the ammonia sensor in this disclosure will be explained, assuming that the sensitive film contains a first substance whose resistance increases upon contact with ammonia.

[0020] As will be described later, polyaniline can be cited as the first substance. Polyaniline is a p-type semiconductor, and protons act as carriers, exhibiting conductivity. Therefore, in an atmosphere without ammonia, the sensitive film containing polyaniline has low resistance and is conductive. At this time, the pair of electrodes short-circuit and become conductive.

[0021] On the other hand, when polyaniline reacts with ammonia, it undergoes localized deprotonation, increasing its resistance. Therefore, in an atmosphere containing ammonia, the sensitive film containing polyaniline becomes highly resistive and insulating. At this time, the pair of electrodes are insulated and become non-conductive.

[0022] A communication unit, which has a detection unit that detects changes in resistance, is connected to a pair of electrodes. By detecting changes in resistance using the detection unit, ammonia gas can be detected. Furthermore, the communication unit allows for the detection of ammonia gas from a remote location.

[0023] Next, the operating principle of the ammonia sensor in this disclosure will be described when the sensitive film contains a second substance whose resistance decreases upon contact with ammonia.

[0024] As will be described later, an oxide semiconductor can be used as the second material, specifically tin oxide. When using tin oxide, since tin oxide has a high operating temperature, the ammonia sensor is used by heating the sensing film. Oxygen from the atmosphere is adsorbed on the surface of the tin oxide, and the oxygen traps electrons from the tin oxide, making it difficult for electrons to move and increasing the resistance. Therefore, in an atmosphere where ammonia is not present, the sensing film containing tin oxide has a high resistance and is insulating. In this case, the pair of electrodes are insulated and are in a non-conductive state.

[0025] On the other hand, when ammonia comes into contact with tin oxide on which oxygen is adsorbed, the oxygen reacts with the ammonia and is released, allowing electrons that were trapped by the oxygen to move freely, thus lowering the resistance. Therefore, in an atmosphere where ammonia is present, the sensitive film containing tin oxide becomes less resistive and more conductive. At this time, the pair of electrodes short-circuit, resulting in a conductive state.

[0026] A communication unit, which has a detection unit that detects changes in resistance, is connected to a pair of electrodes. By detecting changes in resistance using the detection unit, ammonia gas can be detected. Furthermore, the communication unit allows for the detection of ammonia gas from a remote location.

[0027] The ammonia sensor described in this disclosure will be explained below for each component.

[0028] 1. Sensitive membrane The sensitive film in this disclosure includes a substance whose resistance changes upon contact with ammonia.

[0029] Substances whose resistance changes upon contact with ammonia include a first substance whose resistance increases upon contact with ammonia, and a second substance whose resistance decreases upon contact with ammonia.

[0030] The first substance is not particularly limited as long as it is a substance whose resistance increases upon contact with ammonia, and examples include polyaniline, polysiloxane, polyphenylsulfone, and PEDOT:PSS (Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)). Among these, polyaniline is preferred because it exhibits a large change in resistance.

[0031] Polyanilines are generally known to have four types of structures: emeraldine salt type, emeraldine base type, pernigranin type, and leucoemeraldine type. Of these, only the emeraldine salt type of polyaniline exhibits conductivity. In this disclosure, the emeraldine salt type of polyaniline is used. The emeraldine salt type of polyaniline can be represented, for example, by the following general formula.

[0032] [ka]

[0033] In the above general formula, A - As for, Cl - , OH - NO3 - These are some examples.

[0034] In the reaction between polyaniline and ammonia, as shown below, the emeraldine salt type polyaniline reacts with ammonia, and the ammonia combines with a proton to form a quaternary ammonium salt, i.e., deprotonation, resulting in the formation of the emeraldine base type polyaniline. Furthermore, protonation of the emeraldine base type polyaniline results in the formation of the emeraldine salt type polyaniline. The emeraldine salt type polyaniline exhibits conductivity, while the emeraldine base type polyaniline exhibits insulating properties.

[0035] [ka]

[0036] The second substance is not particularly limited as long as it is a substance whose resistance decreases upon contact with ammonia, for example, an oxide semiconductor. The oxide semiconductor is preferably tin oxide. Tin oxide is widely used as a semiconductor gas sensor.

[0037] In particular, polyaniline is preferred as the substance whose resistance changes upon contact with ammonia. Since polyaniline and ammonia react at room temperature, heating is unnecessary. Therefore, the risk to ammonia, which requires explosion-proof measures, can be reduced. Furthermore, since heating is unnecessary, electricity supply is not required. Therefore, ammonia sensors can be made to have a large surface area and can detect ammonia gas over a relatively wide area. Consequently, by using ammonia sensors, ammonia gas leaks can be detected not only in small devices such as fuel cells, but also in large facilities such as ammonia production facilities, ammonia pipelines, transport tankers, storage tanks, ammonia power generation facilities, and ammonia hydrogen stations.

[0038] Conventional semiconductor-type ammonia sensors detect ammonia gas in the area where they are installed. Therefore, they can only detect ammonia gas in a narrow range, such as within approximately 10 cm around the sensor.

[0039] The sensitive film only needs to be positioned in contact with the pair of electrodes, and its position is not particularly limited. For example, the pair of electrodes and the sensitive film may be arranged in this order on the first surface of the substrate, or the sensitive film and the pair of electrodes may be arranged in this order on the first surface of the substrate.

[0040] The thickness of the sensitive film is not particularly limited, as long as it is thick enough to detect changes in the resistance of the sensitive film. When the sensitive film contains polyaniline, the thickness of the sensitive film is, for example, 200 nm to 5000 nm, preferably 500 nm to 2000 nm. When the sensitive film contains an oxide semiconductor, the thickness of the sensitive film is, for example, 100 nm to 1000 nm, preferably 200 nm to 800 nm.

[0041] The method for forming the sensitive film is appropriately selected depending on the type of substance. When the sensitive film contains polyaniline, one method for forming the sensitive film is to use a composition in which polyaniline is dissolved or dispersed in a solvent and then coat the composition. When the sensitive film contains an oxide semiconductor, one method for forming the sensitive film is the sol-gel method, sputtering method, etc.

[0042] 2. Communications Department The communication unit in this disclosure has a detection unit connected to a pair of electrodes that detects changes in resistance.

[0043] Examples of communication systems include those that perform wireless communication. Specifically, these include short-range wireless communication such as IC tags, Bluetooth®, and Wi-Fi®, as well as long-range wireless communication such as LPWA. IC tags are also referred to as RF tags, RFID tags, electronic tags, and wireless tags.

[0044] The detection unit can be any unit capable of detecting changes in resistance, and can be appropriately selected depending on the type of communication unit.

[0045] In the IC tag, an IC chip that detects changes in resistance is used as the detection unit. An open-short type IC chip can be used as the IC chip. The open-short type is an IC chip that detects changes in resistance by entering a high-resistance state and flag information becoming "0" when the resistance value between terminals is equal to or greater than a first threshold resistance value, and entering a low-resistance state and flag information becoming "1" when the resistance value between terminals is less than or equal to a second threshold resistance value which is less than the first threshold resistance value. Alternatively, a capacitive type IC chip may be used as the IC chip. A capacitive type is typically an IC chip that detects the change in impedance when the antenna is detuned when liquid ammonia comes into contact with the antenna. In this disclosure, when a capacitive type IC chip is used, the above-mentioned sensitive film is separately placed in contact with the antenna of the IC tag described later, and the change in impedance is detected.

[0046] The IC tag has the above-mentioned IC chip as a detection unit and also has an antenna. Any IC tag having the above-mentioned IC chip and antenna will suffice; a general-purpose IC tag can be used. If an IC tag is used, ammonia can be detected using RFID.

[0047] IC tags come in two types: active tags, which have a built-in power source (battery), and passive tags, which do not. Of these, passive tags are preferred because they do not have their own power source (battery) and instead obtain power by receiving radio waves supplied from an external source via an antenna.

[0048] In Bluetooth®, Wi-Fi®, and LPWA, a microcomputer is used as the detection unit. Hereafter, the microcomputer may be referred to as a microcontroller. Any microcontroller with A / D converter functionality is acceptable, and a general-purpose microcontroller can be used. The microcontroller converts the analog signal into a digital signal, and ammonia leakage is determined by comparing the digital signal with a preset reference value.

[0049] There is at least one communications unit. There may be one communications unit or there may be multiple communications units.

[0050] The communication unit may be integrated with the substrate on which the sensitive film and pair of electrodes are arranged, or it may be a separate unit. In Figure 1, the IC tag 5 and the substrate 2 on which the sensitive film 3 and pair of electrodes 4a and 4b are arranged are separate units. On the other hand, in Figure 2, the IC tag 5 is arranged on one side of the substrate 2, and the IC tag 5 and the substrate 2 on which the sensitive film 3 and pair of electrodes 4a and 4b are arranged are integrated units. When the communication unit is separate from the substrate on which the sensitive film and pair of electrodes are arranged, the substrate on which the sensitive film and pair of electrodes are arranged can be placed directly on the object to be detected for ammonia leakage, while the communication unit can be placed away from metals or other materials that shield radio waves, or facing equipment that transmits and receives radio waves, thus facilitating radio wave transmission and reception. On the other hand, when the IC tag is integrated with the substrate on which the sensitive film and pair of electrodes are arranged, the ammonia sensor can be installed in a narrower space.

[0051] In particular, the communication unit is preferably an IC tag, and the detection unit is preferably an open-short type IC chip. An example of an open-short type IC chip is NXP's UCODE G2iM+.

[0052] The IC tag has 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 a pair of electrodes. The IC chip preferably has an open-short type that changes to a high-resistance state when the resistance value between the sensor terminals is greater than or equal to a first threshold resistance value, and changes to a low-resistance state when the resistance value between the sensor terminals is less than or equal to a second threshold resistance value that is smaller than the first threshold resistance value. In FIG. 3, the IC tag 5 has a second substrate 21, an IC chip 22 disposed on the 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, 24b disposed on the first surface of the second substrate 21, connected to the IC chip 22, and respectively connected to a pair of electrodes 4a, 4b. In the IC tag 5, the IC chip 22 has an open-short type, and when the resistance value between the sensor terminals 24a, 24b connected to the IC chip 22 is greater than or equal to the first threshold resistance value, it is in a high-resistance state, and when the resistance value between the sensor terminals 24a, 24b is less than or equal to the second threshold resistance value, it changes to a low-resistance state.

[0053] When the sensing film contains a first substance whose resistance value increases upon contact with ammonia, in the IC chip, the resistance value between the sensor terminals when the ammonia concentration is zero is less than or equal to the second threshold resistance value, and the resistance value between the sensor terminals when the ammonia concentration is the set value is greater than or equal to the first threshold resistance value. In this case, an example of the operating principle of the ammonia sensor in the present disclosure when the communication unit is an IC tag will be described.

[0054] As described above, when the sensitive film contains polyaniline as the first substance, in an atmosphere where ammonia is absent, the sensitive film 3 has low resistance and is conductive. At this time, the pair of electrodes 4a and 4b are short-circuited and in a conductive state. Therefore, when power is supplied from the RFID reader / writer to the IC tag 5, current flows through the sensitive film 3 to the pair of electrodes 4a and 4b. In the IC chip 22, when the resistance value between the sensor terminals 24a and 24b is below the second threshold resistance value, it enters a low-resistance state, and for example, the flag information becomes "1". In the IC tag 5, the above information is transmitted to the RFID reader / writer via the antenna 23. In this case, it is determined that no ammonia gas is leaking.

[0055] On the other hand, as mentioned above, if the sensitive film contains polyaniline as the first substance, in an atmosphere where ammonia is present, the polyaniline reacts with ammonia and is deprotonated, causing the sensitive film 3 to have a high resistance and become insulating. At this time, the pair of electrodes 4a and 4b are insulated and become non-conductive. Therefore, even when power is supplied from the RFID reader / writer to the IC tag 5, no current flows through the sensitive 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 greater than or equal to the first threshold resistance, a high-resistance state is entered, and for example, the flag information becomes "0". In the IC tag 5, the above information is transmitted to the RFID reader / writer via the antenna 23. In this case, it is determined that ammonia gas is leaking.

[0056] In this way, the IC tag 5 can detect ammonia gas by detecting a change in the resistance value between the sensor terminals 24a and 24b.

[0057] Figure 4 is a graph showing an example of the relationship between ammonia concentration and the resistance value between the sensor terminals in the ammonia sensor of this disclosure. In Figure 4, T1 is the first threshold resistance value, T2 is the second threshold resistance value, and S is the set value of the ammonia concentration. When the ammonia concentration is zero, as described above, the resistance value of the sensitive film 3 is low, so the pair of electrodes 4a and 4b become conductive. At this time, the resistance value R1 between the sensor terminals 24a and 24b is less than or equal to the second threshold resistance value T2, so it becomes a low resistance state, and for example the flag information becomes "1". On the other hand, when the ammonia concentration increases, the resistance value of the sensitive film 3 increases, and the pair of electrodes 4a and 4b become non-conductive. Then, when the resistance value between the sensor terminals 24a and 24b becomes greater than or equal to the first threshold resistance value T1, it becomes a high resistance state, and for example the flag information becomes "0". When the ammonia concentration is the set value S, the resistance value R2 between the sensor terminals 24a and 24b is greater than or equal to the first threshold resistance value T1. Therefore, when the ammonia concentration exceeds a set value S, an ammonia leak is detected. Thus, the ammonia sensor in this disclosure can accurately detect an ammonia leak when the ammonia concentration exceeds a predetermined concentration, and it is possible to manage the ammonia concentration.

[0058] Figure 5 is a graph showing an example of the relationship between ammonia concentration and the resistance value between sensor terminals in an ammonia sensor without the IC tag described above. First, for the plotted black triangles, when the ammonia concentration is zero, the resistance value R3 between sensor terminals 24a and 24b is greater than or equal to the first threshold resistance value T1, so the flag information will be "0". Also, when the ammonia concentration is the set value S, the resistance value R4 between sensor terminals 24a and 24b is greater than or equal to the first threshold resistance value T1, so the flag information will be "0". Therefore, even if the ammonia concentration is zero, it will be judged that ammonia is leaking. Next, for the plotted black squares, when the ammonia concentration is zero, the resistance value R5 between sensor terminals 24a and 24b is less than or equal to the second threshold resistance value T2, so the flag information will be "1". On the other hand, when the ammonia concentration is the set value S, the resistance value R6 between sensor terminals 24a and 24b is lower than the first threshold resistance value T1, so the flag information will not be "0". Therefore, even if the ammonia concentration is high and an ammonia leak is occurring, the leak cannot be detected. Consequently, in such cases, it is impossible to control the ammonia concentration.

[0059] Therefore, by using the ammonia sensor in this disclosure, it is possible to accurately detect ammonia leaks and manage ammonia concentrations.

[0060] If the sensitive film contains a second substance whose resistance decreases upon contact with ammonia, then in the IC chip, the resistance between the sensor terminals when the ammonia concentration is zero will be equal to or greater than the first threshold resistance, and the resistance between the sensor terminals when the ammonia concentration is a set value will be equal to or less than the second threshold resistance. In this case, an example of the operating principle of the ammonia sensor in this disclosure, where the communication unit is an IC tag, will be described.

[0061] As described above, when the sensitive film contains tin oxide as the second substance, in an atmosphere where ammonia is absent, the sensitive film 3 has high resistance and acts as an insulator. In this case, the pair of electrodes 4a and 4b are insulated and non-conductive. Therefore, even when power is supplied from the RFID reader / writer to the IC tag 5, no current flows through the sensitive 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 greater than or equal to the first threshold resistance, it enters a high-resistance state, and for example, the flag information becomes "0". In the IC tag 5, the above information is transmitted to the RFID reader / writer via the antenna 23. In this case, it is determined that no ammonia gas is leaking.

[0062] On the other hand, as mentioned above, if the sensitive film contains tin oxide as the second substance, in an atmosphere where ammonia is present, the oxygen adsorbed on the surface of the tin oxide reacts with the ammonia and is released, allowing the electrons trapped by the oxygen to move freely. As a result, the sensitive film 3 becomes less resistive and more conductive. At this time, the pair of electrodes 4a and 4b short-circuit and become conductive. Therefore, when power is supplied from the RFID reader / writer to the IC tag 5, current flows through the sensitive 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, it enters a low-resistance state, and for example, the flag information becomes "1". In the IC tag 5, the above information is transmitted to the RFID reader / writer via the antenna 23. In this case, it is determined that ammonia gas is leaking.

[0063] In this way, the IC tag 5 can detect ammonia gas by detecting a change in the resistance value between the sensor terminals 24a and 24b.

[0064] Figure 6 is a graph showing an example of the relationship between ammonia concentration and the resistance value between the sensor terminals in the ammonia sensor of this disclosure. In Figure 6, T1 is the first threshold resistance value, T2 is the second threshold resistance value, and S is the set value of the ammonia concentration. When the ammonia concentration is zero, as described above, the resistance value of the sensitive film 3 is high, so 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, so it becomes a high-resistance state, and for example the flag information becomes "0". On the other hand, when the ammonia concentration increases, the resistance value of the sensitive film 3 decreases, and the pair of electrodes 4a and 4b become conductive. Then, when the resistance value between the sensor terminals 24a and 24b becomes less than or equal to the second threshold resistance value T2, it becomes a low-resistance state, and for example the flag information becomes "1". When the ammonia 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, when the ammonia concentration exceeds a set value S, an ammonia leak is detected. Thus, the ammonia sensor in this disclosure can accurately detect an ammonia leak when the ammonia concentration exceeds a predetermined concentration, and it is possible to manage the ammonia concentration.

[0065] Figure 7 is a graph showing an example of the relationship between ammonia concentration and the resistance value between sensor terminals in an ammonia sensor without the IC tag described above. First, for the plotted black triangles, when the ammonia concentration is zero, the resistance value R3 between sensor terminals 24a and 24b is greater than or equal to the first threshold resistance value T1, so the flag information will be "0". On the other hand, when the ammonia concentration is the set value S, the resistance value R4 between sensor terminals 24a and 24b is higher than the second threshold resistance value T2, so the flag information will not be "1". Therefore, even if the ammonia concentration is high and an ammonia leak is occurring, the ammonia leak cannot be detected. Next, for the plotted black squares, when the ammonia concentration is zero, the resistance value R5 between sensor terminals 24a and 24b is less than or equal to the second threshold resistance value T2, so the flag information will be "1". Furthermore, when the ammonia concentration is at the set value S, the resistance R6 between sensor terminals 24a and 24b is less than or equal to the second threshold resistance T2, so the flag information becomes "1," for example. Therefore, even if the ammonia concentration is zero, it will be judged that ammonia is leaking. Consequently, in such cases, it is not possible to manage the ammonia concentration.

[0066] Therefore, by using the ammonia sensor in this disclosure, it is possible to accurately detect ammonia leaks and manage ammonia concentrations.

[0067] Furthermore, in the wireless tag described in Reference 1, the circuit configuration becomes complex and manufacturing costs are high in order to detect fluctuations in the resonant frequency of the resonant circuit. In contrast, in the ammonia sensor in this disclosure, when the above-mentioned open-short type IC chip is used, the circuit configuration can be simplified and manufacturing costs can be reduced.

[0068] As described above, if the sensitive film contains a first substance whose resistance increases upon contact with ammonia, then in the IC chip, the resistance between the sensor terminals when the ammonia concentration is zero will be less than or equal to the second threshold resistance, and the resistance between the sensor terminals when the ammonia concentration is set to a specific value will be greater than or equal to the first threshold resistance. In this case, for example, if the set value of the ammonia concentration is 0.5%, and the first threshold resistance is set to 100%, the difference between the resistance between the sensor terminals when the ammonia concentration is set to a specific value and the first threshold resistance is preferably 1% or more of the first threshold resistance, more preferably 5% or more, and even more preferably 10% or more. Variations may occur in the characteristics of the IC chip. Therefore, considering safety, it is preferable that the above difference be within the above range. On the other hand, for example, if the set value for ammonia concentration is 0.5%, and the first threshold resistance is set to 100%, the difference between the resistance value between the sensor terminals when the ammonia concentration is at the set value and the first threshold resistance is preferably 20% or less of the first threshold resistance, more preferably 15% or less of the first threshold resistance, and even more preferably 10% or less of the first threshold resistance. If the above difference is too large, the resistance value between the sensor terminals when the ammonia concentration is significantly lower than the set value may also exceed the first threshold resistance, which may make it difficult to control the ammonia concentration. Specifically, if the set value for ammonia concentration is 0.5%, and the first threshold resistance is set to 100%, the difference between the resistance value between the sensor terminals when the ammonia concentration is at the set value and the first threshold resistance is preferably 1% to 20% of the first threshold resistance, and more preferably 5% to 15% of the first threshold resistance.

[0069] On the other hand, as described above, if the sensitive film contains a second substance whose resistance decreases upon contact with ammonia, then in the IC chip, the resistance between the sensor terminals when the ammonia concentration is zero will be equal to or greater than the first threshold resistance, and the resistance between the sensor terminals when the ammonia concentration is set to a specific value will be equal to or less than the second threshold resistance. In this case, for example, if the set value of the ammonia concentration is 0.5%, and the second threshold resistance is set to 100%, the difference between the resistance between the sensor terminals when the ammonia concentration is set to a specific value and the second threshold resistance is preferably 1% or more of the second threshold resistance, more preferably 5% or more, and even more preferably 10% or more. Variations may occur in the characteristics of the IC chip. Therefore, considering safety, it is preferable that the above difference be within the above range. On the other hand, for example, if the set value for ammonia concentration is 0.5%, and the second threshold resistance is set to 100%, the difference between the resistance value between the sensor terminals when the ammonia concentration is at the set value and the second threshold resistance is preferably 20% or less of the second threshold resistance, more preferably 15% or less of the second threshold resistance, and even more preferably 10% or less of the second threshold resistance. If the above difference is too large, the resistance value between the sensor terminals when the ammonia concentration is significantly lower than the set value may also fall below the second threshold resistance, which may make it difficult to control the ammonia concentration. Specifically, if the set value for ammonia concentration is 0.5%, and the second threshold resistance is set to 100%, the difference between the resistance value between the sensor terminals when the ammonia concentration is at the set value and the second threshold resistance is preferably 1% to 20% of the second threshold resistance, and more preferably 5% to 15% of the second threshold resistance.

[0070] Here, the concentration of ammonia in the atmosphere varies depending on the region and season, but is typically between 1 ppb and 10 ppb. Therefore, in this specification, the concept of an ammonia concentration of zero includes cases where the ammonia concentration is 10 ppb or less.

[0071] The resistance between the sensor terminals at a given ammonia concentration is determined by the following method. First, the IC tag is removed from the ammonia sensor. Next, while exposing the ammonia sensor to the given ammonia concentration, the impedance of the pair of electrodes connected to the pair of sensor terminals of the IC tag is measured at a frequency of 20 kHz using an LCR meter, and the resistance between the pair of electrodes is determined from the impedance. Five measurements are taken, and the average of the three measurements obtained by subtracting the maximum and minimum values ​​from the five measurements is taken as the resistance between the sensor terminals at the given ammonia concentration.

[0072] In the ammonia sensor described herein, methods for adjusting the resistance between the sensor terminals when the ammonia concentration is zero include, for example, adjusting the distance between a pair of electrodes, such as the distance between a pair of comb-tooth electrodes, and adjusting the thickness of the sensitive film. When the distance between the pair of comb-tooth electrodes is increased, the resistance between the sensor terminals when the ammonia concentration is zero tends to increase, while when the distance between the pair of comb-tooth electrodes is decreased, the resistance between the sensor terminals when the ammonia concentration is zero tends to decrease. Similarly, when the thickness of the sensitive film is increased, the resistance between the sensor terminals when the ammonia concentration is zero tends to increase, while when the thickness of the sensitive film is decreased, the resistance between the sensor terminals when the ammonia concentration is zero tends to decrease. The method for adjusting the resistance between the sensor terminals when the ammonia concentration is a set value is the same as the method for adjusting the resistance between the sensor terminals when the ammonia concentration is zero described above.

[0073] The explosive limit concentration for ammonia gas is between 15% and 28%, while ammonia is highly toxic, so the permissible concentration is, for example, 50 ppm, and the lethal dose is 6500 ppm. Note that these figures vary depending on the literature and are for reference only. However, ammonia used as a green energy source is managed even more strictly than hydrogen, and containment devices are installed as a countermeasure in case of leakage, so the possibility of direct human exposure is low. If the ammonia concentration is set too low for safety reasons, it would frequently be mistaken for an ammonia leak. Therefore, a setting of 0.5% or higher is preferable for the ammonia concentration.

[0074] In an IC chip, the first and second threshold resistance values ​​are not particularly limited, except that the second threshold resistance value is lower than the first threshold resistance value. However, the first threshold resistance value is preferably between 1 MΩ and 20 MΩ, and more preferably between 10 MΩ and 15 MΩ. If the first threshold resistance value is too low, changes in resistance may be detected frequently, which could lead to frequent misdiagnosis of ammonia leakage. Also, if the first threshold resistance value is too low, the difference between the first and second threshold resistance values ​​becomes small, making design difficult. The difference between the first and second threshold resistance values ​​is preferably between 10 MΩ and 100 MΩ. If the above difference is too small or too large, design becomes difficult.

[0075] The first and second threshold resistance values ​​are determined by the following method. First, prepare a fixed resistor with a known resistance value and a commercially available RFID reader / writer. Also, remove the IC tag from the ammonia sensor. Connect the fixed resistor to the pair of sensor terminals on the IC tag, transmit a readout signal using the RFID reader / writer, and verify the value using the flag of the reflected signal. In an open-short type IC chip, "open" ideally means that the load (electrical resistance, impedance) connected to the IC chip is infinite, that is, the external load connection terminals of the IC chip are open. "Short" ideally means that the load (electrical resistance, impedance) connected to the IC chip is zero, that is, the external load connection terminals of the IC chip are short-circuited by a wire. However, in a normal electrical circuit, it is not possible to physically or mechanically disconnect the load, so it is common to determine that a resistance value above a certain level is open, and a resistance value below a certain level is short. The threshold resistance values ​​are set to be the resistance values ​​that can generally be considered as an insulating state in the case of an open circuit, and the resistance values ​​that can generally be considered as a conductive state in the case of a short circuit. In this disclosure, an open circuit is considered a high-resistance state, and a short circuit is considered a low-resistance state. Therefore, the first threshold resistance value is set to the resistance value that can be considered as an insulating state. Specifically, the minimum value among the resistance values ​​that can be considered as an insulating state is set as the first threshold resistance value. The second threshold resistance value is set to the resistance value that can be considered as a conductive state. Specifically, the maximum value among the resistance values ​​that can be considered as a conductive state is set as the second threshold resistance value. Although the first and second threshold resistance values ​​are published as characteristic data for commercially available IC chips, there are individual differences, so the above measurement method is adopted.

[0076] 3. A pair of electrodes In this disclosure, a pair of electrodes are arranged on the first surface of a substrate in contact with the sensitive film. The pair of electrodes are usually spaced apart so as to be able to detect changes in the resistance of the sensitive film. In this specification, if the sensitive film contains a first substance whose resistance increases upon contact with ammonia, "spaces apart so as to be able to detect changes in the resistance of the sensitive film" means that in an atmosphere where ammonia is absent, the pair of electrodes can be short-circuited, and that when the first substance and ammonia come into contact and a predetermined reaction occurs, causing the resistance of the sensitive film to increase, the pair of electrodes can be insulated. On the other hand, if the sensitive film contains a second substance whose resistance decreases upon contact with ammonia, "spaces apart so as to be able to detect changes in the resistance of the sensitive film" means that in an atmosphere where ammonia is absent, the pair of electrodes can be insulated, and that when the second substance and ammonia come into contact and a predetermined reaction occurs, causing the resistance of the sensitive film to decrease, the pair of electrodes can be insulated.

[0077] Preferably, the pair of electrodes are a pair of comb-tooth electrodes. Specifically, as shown in Figure 8, the pair of electrodes 4a and 4b have a plurality of first sensor electrodes 11 and a plurality of second sensor electrodes 12, 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, and preferably the plurality of first sensor electrodes and the plurality of second sensor electrodes are arranged on the first surface of the substrate in contact with the sensitive film and are arranged alternately with intervals that allow for detection of changes in the resistance value of the sensitive film. Electrode 4a has a plurality of first sensor electrodes 11 and a first bus electrode 13 connected to the first sensor electrodes 11. Electrode 4b has a plurality of second sensor electrodes 12 and a second bus electrode 14 connected to the second sensor electrodes 12.

[0078] Examples of conductive materials used for a pair of electrodes include carbon and metallic materials. As described above, when the sensitive film and the pair of electrodes are arranged in that order on the first surface of the substrate, it is preferable that the conductive material used for the pair of electrodes is inert to ammonia gas. On the other hand, when the pair of electrodes and the sensitive film are arranged in that order on the first surface of the substrate, the conductive material used for the pair of electrodes is not exposed to ammonia gas, so it may be active or inert to ammonia gas.

[0079] The thickness of the pair of electrodes is not particularly limited as long as it is a thickness that can function as an electrode, for example, between 0.1 μm and 2 μm.

[0080] The method for forming a pair of electrodes is not particularly limited and includes, for example, a method of forming a conductive film and patterning it, a mask deposition method, and a printing method. Examples of methods for forming a conductive film include vacuum deposition, sputtering, ion plating, and plating. Examples of patterning methods include etching and lift-off methods.

[0081] Below, three embodiments of a pair of electrodes are illustrated.

[0082] (1) First aspect In the pair of electrodes of this embodiment, one first bus electrode and one second bus electrode are arranged in a linear shape that can be drawn in a single stroke, and one end of the first bus electrode and one end of the second bus electrode are connected to the IC tag.

[0083] In Figures 9 and 10, the first bus electrode 13 and the second bus electrode 14 are arranged in a linear fashion that can be drawn in a single stroke. Specifically, the first bus electrode 13 and the second bus electrode 14 are arranged in a meandering linear fashion. In Figure 9, one end of the first bus electrode 13 and one end of the second bus electrode 14 are connected to the IC tag 5. In Figure 10, 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.

[0084] The distance between the first and second sensor electrodes may be any distance that allows for the detection of changes in the resistance of the sensitive film. For example, the distance may be 100 μm or more, or 500 μm or more. Alternatively, the distance may be 10 mm or less, or 5 mm or less. That is, for example, the distance may be 100 μm or more and 10 mm or less, or 500 μm or more and 5 mm or less.

[0085] The distance between the first and second sensor electrodes is the shortest distance from the end of one adjacent first sensor electrode to the end of the second sensor electrode. For example, in Figure 9, the distance between the first sensor electrode 11 and the second sensor electrode 12 is shown by the shortest distance d1 of the line connecting the adjacent first and second sensor electrodes 11 and 12.

[0086] The widths of the first and second sensor electrodes should be such that they can detect changes in the resistance of the sensitive film. For example, the width may be 100 μm or more, or 500 μm or more. Alternatively, the width may be 10 mm or less, or 5 mm or less. That is, for example, the width may be 100 μm or more and 10 mm or less, or 500 μm or more and 5 mm or less. For example, in Figure 9, the width of the first sensor electrode 11 is shown by the length b1 in the direction perpendicular to the direction in which the first sensor electrode 11 extends. Similarly, the width of the second sensor electrode 12 is shown by the length b2 in the direction perpendicular to the direction in which the second sensor electrode 12 extends.

[0087] The lengths of the first and second sensor electrodes should be such that they can detect changes in the resistance of the sensitive film. For example, the lengths may be 10 mm or more, and 50 mm or more. Alternatively, the lengths may be 500 mm or less, and 100 mm or less. That is, for example, the lengths may be 10 mm or more and 500 mm or less, and 50 mm or more and 100 mm or less. For example, in Figure 9, the length of the first sensor electrode 11 is shown by the length a1 in the direction in which the first sensor electrode 11 extends. The length of the second sensor electrode 12 is shown by the length a2 in the direction in which the second sensor electrode 12 extends.

[0088] The overlap length of the first sensor electrode and the second sensor electrode should be such that a change in the resistance value of the sensitive film can be detected. The overlap length may be, for example, 9 mm or more, and may be 45 mm or more. Alternatively, the overlap length may be, for example, 450 mm or less, and may be 90 mm or less. That is, the overlap length may be, for example, 9 mm or more and 450 mm or less, and 45 mm or more and 90 mm or less. For example, in Figure 9, the overlap length of the first sensor electrode 11 and the second sensor electrode 12 is indicated by the length c of the portion where the first sensor electrode 11 and the second sensor electrode 12 face each other in the direction in which the first sensor electrode 11 and the second sensor electrode 12 extend.

[0089] The number of first and second sensor electrodes is set appropriately according to the size of the ammonia sensor, the arrangement of the first and second bath electrodes, and so on.

[0090] The shapes of the first and second sensor electrodes are not particularly limited and can be, for example, linear, bent, or curved. For example, in Figure 9, the shapes of the first sensor electrode 11 and the second sensor electrode 12 are linear. Also, for example, in Figure 11, the shapes of the first sensor electrode 11 are linear and bent, and the shape of the second sensor electrode 12 is linear.

[0091] The first and second bus electrodes are arranged in a linear pattern that can be drawn in a single continuous line. In this specification, "linear pattern that can be drawn in a single continuous line" means that the line consists of a single continuous line and has no overlapping sections.

[0092] The linear arrangement that can be drawn in a single stroke is not particularly limited as long as the first bus electrode, second bus electrode, first sensor electrode, and second sensor electrode can be arranged evenly on the first surface of the substrate. Examples include a meandering linear arrangement as shown in Figures 9 and 10, and a spiral arrangement as shown in Figure 11. In particular, it is preferable that the first bus electrode and second bus electrode are arranged in a meandering linear arrangement. In this case, the first bus electrode and second bus electrode can be formed by a roll-to-roll method, allowing for efficient mass production of ammonia sensors.

[0093] 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 arranged alternately, the first bus electrode and the second bus electrode are arranged so as to be aligned with each other.

[0094] The widths of the first and second bus electrodes are limited to widths that allow them to function as electrodes. For example, the width may be 1 mm or more, and may be 5 mm or more. Alternatively, the width may be 50 mm or less, and may be 10 mm or less. That is, for example, the width may be 1 mm or more and 50 mm or less, and 5 mm or more and 10 mm or less. For example, in Figure 9, the width of the first bus electrode 13 is shown by the length e1 in the direction perpendicular to the direction in which the first bus electrode 13 extends. Similarly, the width of the second bus electrode 14 is shown by the length e2 in the direction perpendicular to the direction in which the second bus electrode 14 extends.

[0095] The distance between the first bus electrode and the second bus electrode, which face each other with the first sensor electrode and the second sensor electrode in between, is sufficient to allow the first sensor electrode and the second sensor electrode to be placed. The above distance may be, for example, 11 mm or more, and may be 55 mm or more. Alternatively, the above distance may be, for example, 550 mm or less, and may be 110 mm or less. That is, the above distance may be, for example, 11 mm or more and 550 mm or less, and 55 mm or more and 110 mm or less. For example, in Figure 9, the distance between the first bus electrode 13 and the second bus electrode 14, which face each other with the first sensor electrode 11 and the second sensor electrode 12 in between, is shown by the shortest distance f of the line connecting the first bus electrode 13 and the second bus electrode 14, which face each other with the first sensor electrode 11 and the second sensor electrode 12 in between.

[0096] The distance between the first and second bus electrodes, which face each other without the first and second sensor electrodes in between, should be such that a change in the resistance of the sensitive film cannot be detected. The above distance may be, for example, 10 mm or more, and may be 50 mm or more. Alternatively, the above distance may be, for example, 100 mm or less, and may be 70 mm or less. That is, the above distance may be, for example, 10 mm or more and 100 mm or less, and 50 mm or more and 70 mm or less. If the sensitive film contains a first substance whose resistance increases when in contact with ammonia, if the above distance is too small, there is a possibility that the first and second bus electrodes, which face each other without the first and second sensor electrodes in between, may easily conduct electricity when the resistance of the sensitive film is low in an atmosphere where ammonia is absent. Furthermore, if the sensitive film contains a second substance whose resistance decreases upon contact with ammonia, when the second substance and ammonia come into contact and a predetermined reaction occurs, the first and second bus electrodes, which face each other without the first and second sensor electrodes in between, may become more conductive when the resistance of the sensitive film decreases. For example, in Figure 9, the distance between the first bus electrode 13 and the second bus electrode 14, which face each other without the first sensor electrode 11 and the second sensor electrode 12 in between, is shown by the shortest distance g of the line connecting the first bus electrode 13 and the second bus electrode 14, which face each other without the first sensor electrode 11 and the second sensor electrode 12 in between.

[0097] The spacing between adjacent first bath electrodes and between adjacent second bath electrodes should be such that a change in the resistance of the sensitive film cannot be detected. The spacing may be, for example, 10 mm or more, and may be 50 mm or more. Alternatively, the spacing may be, for example, 100 mm or less, and may be 70 mm or less. That is, the spacing may be, for example, 10 mm or more and 100 mm or less, and 50 mm or more and 70 mm or less. If the sensitive film contains a first substance whose resistance increases upon contact with ammonia, if the spacing is too small, there is a possibility that adjacent first bath electrodes or adjacent second bath electrodes may become more conductive when the resistance of the sensitive film is low in an atmosphere where ammonia is absent. Also, if the sensitive film contains a second substance whose resistance decreases upon contact with ammonia, there is a possibility that adjacent first bath electrodes or adjacent second bath electrodes may become more conductive when the second substance and ammonia come into contact, a predetermined reaction occurs, and the resistance of the sensitive film decreases. For example, in Figure 9, the distance between adjacent first bus electrodes 13 is shown by the shortest distance h1 between adjacent first bus electrodes 13. Similarly, the distance between adjacent second bus electrodes 14 is shown by the shortest distance h2 between adjacent second bus electrodes 14.

[0098] In this embodiment, the number of first and second bus electrodes is usually one. However, if the first and second bus electrodes form a pair, the number of first and second bus electrodes may be two. For example, in Figure 12, the ammonia sensor 1 has two first bus electrodes 13a and 13b and two second bus electrodes 14a and 14b, with the first bus electrode 13a and the second bus electrode 14a forming a pair, and the first bus electrode 13b and the second bus electrode 14b forming a pair.

[0099] (2) Second aspect In this embodiment, a pair of electrodes consists of multiple first bus electrodes and multiple second bus electrodes connected to an IC tag via a flexible printed circuit board.

[0100] In Figure 13, the multiple first bus electrodes 13 and the multiple second bus electrodes 14 are connected to the IC tag 5 via a flexible printed circuit board 9. In Figure 14, one end of the multiple first bus electrodes 13 and one end of the multiple second bus electrodes 14 are connected to the first IC tag 5a via the flexible printed circuit board 9, and the other end of the multiple first bus electrodes 13 and the other end of the multiple second bus electrodes 14 are connected to the second IC tag 5b via the flexible printed circuit board 9.

[0101] In this embodiment, the first bus electrode and the second bus electrode can be arranged in a straight line, thereby reducing the risk of wire breakage.

[0102] The distance between the first and second sensor electrodes may be any distance that allows for the detection of changes in the resistance of the sensitive film. For example, the distance may be 100 μm or more, or 500 μm or more. Alternatively, the distance may be 10 mm or less, or 5 mm or less. That is, for example, the distance may be 100 μm or more and 10 mm or less, or 500 μm or more and 5 mm or less.

[0103] The distance between the first and second sensor electrodes refers to the distance from the end of one adjacent first sensor electrode to the end of the second sensor electrode. For example, in Figure 13, the distance between the first sensor electrode 11 and the second sensor electrode 12 is shown by the shortest distance d1 of the line connecting the adjacent first and second sensor electrodes 11 and 12.

[0104] The widths of the first and second sensor electrodes should be such that they allow for the detection of changes in the resistance of the sensitive film. These widths may be, for example, 100 μm or more, or 500 μm or more. Alternatively, they may be, for example, 10 mm or less, or 5 mm or less. That is, for example, the widths may be between 100 μm and 10 mm, or between 500 μm and 5 mm. For example, in Figure 13, the width of the first sensor electrode 11 is shown by the length b1 in the direction perpendicular to the direction in which the first sensor electrode 11 extends. The width of the second sensor electrode 12 is shown by the length b2 in the direction perpendicular to the direction in which the second sensor electrode 12 extends.

[0105] The lengths of the first and second sensor electrodes should be such that they can detect changes in the resistance of the sensitive film. For example, the lengths may be 10 mm or more, and 50 mm or more. Alternatively, the lengths may be 500 mm or less, and 100 mm or less. That is, for example, the lengths may be 10 mm or more and 500 mm or less, and 50 mm or more and 100 mm or less. For example, in Figure 13, the length of the first sensor electrode 11 is shown by the length a1 in the direction in which the first sensor electrode 11 extends. The length of the second sensor electrode 12 is shown by the length a2 in the direction in which the second sensor electrode 12 extends.

[0106] The overlap length of the first sensor electrode and the second sensor electrode should be such that a change in the resistance value of the sensitive film can be detected. The overlap length may be, for example, 9 mm or more, and may be 45 mm or more. Alternatively, the overlap length may be, for example, 450 mm or less, and may be 90 mm or less. That is, the overlap length may be, for example, 9 mm or more and 450 mm or less, and 45 mm or more and 90 mm or less. For example, in Figure 13, the overlap length of the first sensor electrode 11 and the second sensor electrode 12 is indicated by the length c of the portion where the first sensor electrode 11 and the second sensor electrode 12 face each other in the direction in which the first sensor electrode 11 and the second sensor electrode 12 extend.

[0107] The number of first and second sensor electrodes is set appropriately according to the size of the ammonia sensor, the arrangement of the first and second bath electrodes, and so on.

[0108] The shape of the first sensor electrode and the shape of the second sensor electrode are not particularly limited and include, for example, a straight, bent, or curved shape.

[0109] The first bus electrode and the second bus electrode are paired and arranged alternately.

[0110] The widths of the first and second bus electrodes are limited to widths that allow them to function as electrodes. The above widths may be, for example, 1 mm or more, and 5 mm or more. Alternatively, the above widths may be, for example, 50 mm or less, and 10 mm or less. That is, the above widths may be, for example, 1 mm or more and 50 mm or less, and 5 mm or more and 10 mm or less. For example, in Figure 13, the width of the first bus electrode 13 is shown by the length e1 in the direction perpendicular to the direction in which the first bus electrode 13 extends. The width of the second bus electrode 14 is shown by the length e2 in the direction perpendicular to the direction in which the second bus electrode 14 extends.

[0111] The distance between the first bus electrode and the second bus electrode may be any distance that allows the first sensor electrode and the second sensor electrode to be placed. The distance may be, for example, 11 mm or more, and 55 mm or more. Alternatively, the distance may be, for example, 550 mm or less, and 110 mm or less. That is, the distance may be, for example, 11 mm or more and 550 mm or less, and 55 mm or more and 110 mm or less. For example, in Figure 13, the distance between the first bus electrode 13 and the second bus electrode 14 is shown by the shortest distance f of the line connecting the first bus electrode 13 and the second bus electrode 14 that face each other with the first sensor electrode 11 and the second sensor electrode 12 in between.

[0112] 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 only need to be in pairs, and the number of first bus electrodes and the number of second bus electrodes can be the same or different. For example, in Figure 13, there are 4 first bus electrodes 13 and 5 second bus electrodes 14, so the number of first bus electrodes and the number of second bus electrodes are different.

[0113] 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.

[0114] (3) Third aspect In the pair of electrodes of this embodiment, a plurality of first bus electrodes are arranged along a first direction, and a plurality of second bus electrodes are arranged along a second direction perpendicular to the first direction. In this embodiment, the IC tag has a third IC tag connected to one end of the plurality of first bus electrodes and a fourth IC tag connected to one end of the plurality of second bus electrodes, and an insulating film is placed between the first bus electrode and the second bus electrode in the region where the first bus electrode and the second bus electrode intersect.

[0115] In Figure 15, the multiple first bus electrodes 13 are arranged linearly in a first direction D1, and the multiple second bus electrodes 14 are arranged linearly in a second direction D2 perpendicular to the first direction D1. The IC tag has a third IC tag 5c connected to one end of the multiple first bus electrodes 13 and a fourth IC tag 5d connected to one end of the multiple second bus electrodes 14. In the region where the first bus electrodes 13 and the second bus electrodes 14 intersect, an insulating film 15 is placed between the first bus electrodes 13 and the second bus electrodes 14.

[0116] In this embodiment, since it is not necessary to arrange the first bus electrode and the second bus electrode in a linear shape that can be drawn in a single stroke, the risk of wire breakage can be reduced. Also, as shown in Figure 12, the area of ​​the overlapping portion 10C of the first sensor electrode 11 and the second sensor electrode 12 can be kept constant, so the variation in the signal is reduced and the detection sensitivity is improved.

[0117] The distance between the first and second sensor electrodes may be any distance that allows for the detection of changes in the resistance of the sensitive film. For example, the distance may be 100 μm or more, or 500 μm or more. Alternatively, the distance may be 10 mm or less, or 5 mm or less. That is, for example, the distance may be 100 μm or more and 10 mm or less, or 500 μm or more and 5 mm or less.

[0118] The distance between the first and second sensor electrodes refers to the distance from the end of one adjacent first sensor electrode to the end of the second sensor electrode. For example, in Figure 15, the distance between the first sensor electrode 11 and the second sensor electrode 12 is shown by the shortest distance d1 of the line connecting the adjacent first and second sensor electrodes 11 and 12.

[0119] The widths of the first and second sensor electrodes should be such that they can detect changes in the resistance of the sensitive film. The above widths may be, for example, 100 μm or more, or 500 μm or more. Alternatively, the above widths may be, for example, 10 mm or less, or 5 mm or less. That is, the above widths may be, for example, 100 μm or more and 10 mm or less, or 500 μm or more and 5 mm or less. For example, in Figure 15, the width of the first sensor electrode 11 is shown by the length b1 in the direction perpendicular to the direction in which the first sensor electrode 11 extends. The width of the second sensor electrode 12 is shown by the length b2 in the direction perpendicular to the direction in which the second sensor electrode 12 extends.

[0120] The lengths of the first and second sensor electrodes should be such that they can detect changes in the resistance of the sensitive film. For example, the lengths may be 10 mm or more, and 50 mm or more. Alternatively, the lengths may be 500 mm or less, and 100 mm or less. That is, for example, the lengths may be 10 mm or more and 500 mm or less, and 50 mm or more and 100 mm or less. For example, in Figure 15, the length of the first sensor electrode 11 is shown by the length a1 in the direction in which the first sensor electrode 11 extends. The length of the second sensor electrode 12 is shown by the length a2 in the direction in which the second sensor electrode 12 extends.

[0121] The overlap length of the first sensor electrode and the second sensor electrode should be such that a change in the resistance value of the sensitive film can be detected. The overlap length may be, for example, 9 mm or more, and may be 45 mm or more. Alternatively, the overlap length may be, for example, 450 mm or less, and may be 90 mm or less. That is, the overlap length may be, for example, 9 mm or more and 450 mm or less, and 45 mm or more and 90 mm or less. For example, in Figure 15, the overlap length of the first sensor electrode 11 and the second sensor electrode 12 is indicated by the length c of the portion where the first sensor electrode 11 and the second sensor electrode 12 face each other in the direction in which the first sensor electrode 11 and the second sensor electrode 12 extend.

[0122] The number of first and second sensor electrodes is set appropriately according to the size of the ammonia sensor, the arrangement of the first and second bath electrodes, and so on.

[0123] The shapes of the first and second sensor electrodes are not particularly limited and include, for example, straight, bent, and curved shapes. Furthermore, the shapes of the first and second sensor electrodes may have branches. For example, in Figure 15, the shape of the first sensor electrode 11 is straight, and the shape of the second sensor electrode 12 has branches. Also, for example, in Figure 16, the shape of the first sensor electrode 11 is straight, and the shape of the second sensor electrode 12 is bent.

[0124] Multiple first bus electrodes are arranged along a first direction, and multiple second bus electrodes are arranged along a second direction perpendicular to the first direction.

[0125] The widths of the first and second bus electrodes are limited to widths that allow them to function as electrodes. The above widths may be, for example, 1 mm or more, and 5 mm or more. Alternatively, the above widths may be, for example, 50 mm or less, and 10 mm or less. That is, the above widths may be, for example, 1 mm or more and 50 mm or less, and 5 mm or more and 10 mm or less. For example, in Figure 15, the width of the first bus electrode 13 is shown by the length e1 in the direction perpendicular to the direction in which the first bus electrode 13 extends. The width of the second bus electrode 14 is shown by the length e2 in the direction perpendicular to the direction in which the second bus electrode 14 extends.

[0126] The spacing between adjacent first bus electrodes and between adjacent second bus electrodes may be any spacing that allows for the placement of the first and second sensor electrodes. For example, the spacing may be 11 mm or more, and may be 55 mm or more. Alternatively, the spacing may be 550 mm or less, and may be 110 mm or less. That is, for example, the spacing may be 11 mm or more and 550 mm or less, and 55 mm or more and 110 mm or less. For example, in Figure 15, the spacing between adjacent first bus electrodes 13 is shown by the shortest distance k1 of the line connecting adjacent first bus electrodes 13. Similarly, the spacing between adjacent second bus electrodes 14 is shown by the shortest distance k2 of the line connecting adjacent second bus electrodes 14.

[0127] The number of first bus electrodes and the number of second bus electrodes are multiple.

[0128] In this embodiment, the insulating film is placed between the first and second bus electrodes in the region where the first and second bus electrodes intersect. The material of the insulating film is not particularly limited as long as it is an insulating material, and 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 thick enough to insulate the first and second bus electrodes, and is for example, 0.1 μm or more and 2 μm or less. The method for forming the insulating film is not particularly limited, and examples include a method of forming the insulating film and then patterning it, a mask deposition method, and a printing method. Examples of methods for forming the insulating film include vacuum deposition, sputtering, ion plating, and plating. Examples of patterning methods include etching and lift-off methods.

[0129] In this embodiment, regarding the position of the sensitive membrane, for example, the first sensor electrode and the second sensor electrode and the sensitive membrane may be arranged on the first surface of the substrate in this order, the sensitive membrane, the first sensor electrode and the second sensor electrode may be arranged on the first surface of the substrate in this order, the first sensor electrode, the sensitive membrane and the second sensor electrode may be arranged on the first surface of the substrate in this order, or the second sensor electrode, the sensitive membrane and the first sensor electrode may be arranged on the first surface of the substrate in this order.

[0130] In this embodiment, the IC tag has 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 have the third IC tag, the fourth IC tag, and a fifth IC tag connected to the other end of a plurality of first bus electrodes. Alternatively, the IC tag may have the third IC tag, the fourth IC tag, and a sixth IC tag connected to the other end of a plurality of second bus electrodes. Alternatively, the IC tag may have the third IC tag, the fourth IC tag, the fifth IC tag, and the sixth IC tag. For example, in Figure 17, the IC tag has a third IC tag 5c connected to one end of a plurality of first bus electrodes 13, a fourth IC tag 5d connected to one end of a plurality of second bus electrodes 14, and a fifth IC tag 5e connected to the other end of a plurality of first bus electrodes 13.

[0131] 4. Circuit board The substrate in this disclosure is an insulating component that supports a sensitive film and a pair of electrodes.

[0132] The substrate is not particularly limited as long as it has insulating properties, and examples include glass substrates, resin substrates, ceramic substrates, and silicon substrates having an insulating film on their surface.

[0133] The thickness of the substrate is not particularly limited, for example, it can be between 10 μm and 2 mm.

[0134] 5. Other configurations In this disclosure, the sensitive film and the pair of electrodes may be arranged on the first surface of the substrate. The sensitive film and the pair of electrodes may be arranged on only one side of the substrate, or the sensitive film and the pair of electrodes may be arranged on both sides of the substrate.

[0135] B. Ammonia detection system The ammonia detection system in this disclosure uses the ammonia sensor described above.

[0136] Figure 18 is a schematic diagram illustrating an ammonia detection system in this disclosure. In Figure 18, the ammonia detection system 30 is used in an ammonia cylinder 41. The ammonia detection system 30 comprises an ammonia sensor 1, an RFID reader / writer 31, and a plurality of antennas 32 connected to the RFID reader / writer 31. The ammonia sensor 1 is attached to the valve portion 42 of the ammonia cylinder 41.

[0137] Figure 19 is a schematic diagram illustrating an ammonia detection system in this disclosure. In Figure 19, the ammonia detection system 30 is used in an ammonia pipeline 43. The ammonia detection system 30 comprises an ammonia sensor 1, an RFID reader / writer 31, and a plurality of antennas 32 connected to the RFID reader / writer 31. The ammonia sensor 1 is attached to a valve portion 44 of the ammonia pipeline 43.

[0138] Figure 20 is a schematic diagram illustrating an ammonia detection system in this disclosure. In Figure 20, the ammonia detection system 30 is used in an ammonia pipeline 43. The ammonia detection system 30 comprises an ammonia sensor 1, an RFID reader / writer 31, and a plurality of antennas 32 connected to the RFID reader / writer 31. The ammonia sensor 1 is attached to the flange portion 45 of the ammonia pipeline 43.

[0139] Figure 21 is a schematic diagram illustrating an ammonia detection system in this disclosure. In Figure 21, the ammonia detection system 30 is used in an ammonia vaporizer 46. The ammonia detection system 30 comprises an ammonia sensor 1, an RFID reader / writer 31, and a plurality of antennas 32 connected to the RFID reader / writer 31. The ammonia sensor 1 is attached to the joint portion of the spiral pipe of the ammonia vaporizer 46.

[0140] In such an ammonia detection system, ammonia gas can be detected by detecting a change in the resistance value of the sensitive membrane using the detection unit of the ammonia sensor's communication unit, without contact.

[0141] The ammonia detection system in this disclosure is not particularly limited as long as it uses an ammonia sensor, but it is preferably a system that uses RFID. Specifically, the ammonia detection system in this disclosure comprises an ammonia sensor, an RFID reader / writer, and an antenna connected to the RFID reader / writer.

[0142] RFID reader / writers may be fixed or mobile. Using a fixed RFID reader / writer allows for continuous monitoring. On the other hand, using a mobile RFID reader / writer enables traceability inspection, making the traceability inspection more sophisticated, smarter, and less labor-intensive.

[0143] The ammonia detection system described herein can be used in any equipment in which ammonia accumulates or moves within it. For example, it can be used in small equipment such as fuel cells, as well as in large equipment such as ammonia cylinders, ammonia vaporizers, ammonia production facilities, ammonia pipelines, transport tankers, storage tanks, ammonia power generation facilities, and ammonia hydrogen stations.

[0144] In an ammonia detection system, it is preferable that ammonia sensors be installed primarily in locations where ammonia leakage is more likely compared to other locations, such as the flanges and valves of ammonia pipelines. In the flanges of ammonia pipelines, the surface of the sensitive membrane of the ammonia sensor is positioned along the flange boundary so that leaked ammonia can be immediately detected. The RFID reader / writer can be installed at any location. The antenna only needs to be installed so that it can send and receive radio waves to the communication section of the ammonia sensor, and should be installed while maintaining an optimal transmission and reception environment in terms of position, distance, and angle. The same applies to RFID reader / writer antennas, where the RFID reader / writer and antenna are integrated.

[0145] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of this disclosure and achieves similar effects is included within the technical scope of this disclosure.

[0146] This disclosure provides the following inventions. [1] circuit board and A sensitive film is placed on the first surface of the above substrate and contains a substance whose resistance changes upon contact with ammonia. A pair of electrodes are arranged on the first surface of the substrate in contact with the sensitive film, A communication unit having a detection unit connected to the pair of electrodes mentioned above and detecting a change in resistance value, An ammonia sensor having the following features. [2] The ammonia sensor according to [1], wherein the above substance is polyaniline or tin oxide. [3] The above substance is polyaniline, The above communication unit is an IC tag, The above IC tag has 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 the pair of electrodes. The above IC chip is of the open-short type, which changes to a high-resistance state when the resistance value between the sensor terminals is equal to or greater than a first threshold resistance value, and to a low-resistance state when the resistance value between the sensor terminals is less than or equal to a second threshold resistance value, which is less than the first threshold resistance value. The ammonia sensor according to [1] or [2], wherein the resistance between the sensor terminals when the ammonia concentration is zero is less than or equal to the second threshold resistance value, and the resistance between the sensor terminals when the ammonia concentration is a set value is greater than or equal to the first threshold resistance value. [4] The ammonia sensor according to [3], wherein, when the above-mentioned first threshold resistance value is set to 100%, the difference between the resistance value between the sensor terminals when the ammonia concentration is the above-mentioned set value and the above-mentioned first threshold resistance value is 1% or more and 20% or less of the above-mentioned first threshold resistance value. [5] The above substance is tin oxide. The above communication unit is an IC tag, The above IC tag has 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 the pair of electrodes. The above IC chip is of the open-short type, which changes to a high-resistance state when the resistance value between the sensor terminals is equal to or greater than a first threshold resistance value, and to a low-resistance state when the resistance value between the sensor terminals is less than or equal to a second threshold resistance value, which is less than the first threshold resistance value. The ammonia sensor according to [1] or [2], wherein the resistance between the sensor terminals when the ammonia concentration is zero is equal to or greater than the first threshold resistance value, and the resistance between the sensor terminals when the ammonia concentration is a set value is equal to or less than the second threshold resistance value. [6] The ammonia sensor according to [5], wherein, when the above-mentioned second threshold resistance value is set to 100%, the difference between the resistance value between the sensor terminals when the ammonia concentration is the above-mentioned set value and the above-mentioned second threshold resistance value is 1% or more and 20% or less of the above-mentioned second threshold resistance value. [7] An ammonia detection system using an ammonia sensor as described in any of [1] to [6]. [8] An ammonia pipeline using the ammonia detection system described in [7]. [Explanation of Symbols]

[0147] 1… Ammonia sensor 2… Circuit board 3. Sensitive membrane 4a, 4b... A pair of electrodes 5… IC tags 11 … First sensor electrode 12 … Second sensor electrode 13 … First bus electrode 14 … Second bus electrode 21 … Second substrate 22… IC chip 23… Antenna 24a, 24b… Sensor terminals 30… Ammonia detection system

Claims

1. circuit board and A sensitive film is placed on the first surface of the substrate and contains a substance whose resistance changes upon contact with ammonia. A pair of electrodes are arranged on the first surface of the substrate in contact with the sensitive film, A communication unit having a detection unit connected to the pair of electrodes and detecting a change in resistance value, An ammonia sensor having the following features.

2. The ammonia sensor according to claim 1, wherein the substance is polyaniline or tin oxide.

3. The substance is polyaniline, The aforementioned communication unit is an IC tag, The IC tag comprises 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 the pair of electrodes. The IC chip is of an open-short type, where it changes to a high-resistance state when the resistance value between the sensor terminals is equal to or greater than a first threshold resistance value, and to a low-resistance state when the resistance value between the sensor terminals is less than or equal to a second threshold resistance value, which is less than the first threshold resistance value. The ammonia sensor according to claim 1, wherein the resistance value between the sensor terminals when the ammonia concentration is zero is less than or equal to the second threshold resistance value, and the resistance value between the sensor terminals when the ammonia concentration is a set value is greater than or equal to the first threshold resistance value.

4. The ammonia sensor according to claim 3, wherein, when the first threshold resistance value is set to 100%, the difference between the resistance value between the sensor terminals when the ammonia concentration is the set value and the first threshold resistance value is 1% or more and 20% or less of the first threshold resistance value.

5. The aforementioned substance is tin oxide, The aforementioned communication unit is an IC tag, The IC tag comprises 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 the pair of electrodes. The IC chip is of an open-short type, where it changes to a high-resistance state when the resistance value between the sensor terminals is equal to or greater than a first threshold resistance value, and to a low-resistance state when the resistance value between the sensor terminals is less than or equal to a second threshold resistance value, which is less than the first threshold resistance value. The ammonia sensor according to claim 1, wherein the resistance between the sensor terminals when the ammonia concentration is zero is greater than or equal to the first threshold resistance value, and the resistance between the sensor terminals when the ammonia concentration is a set value is less than or equal to the second threshold resistance value.

6. The ammonia sensor according to claim 5, wherein, when the second threshold resistance value is set to 100%, the difference between the resistance value between the sensor terminals when the ammonia concentration is the set value and the second threshold resistance value is 1% or more and 20% or less of the second threshold resistance value.

7. An ammonia detection system using an ammonia sensor according to any one of claims 1 to 6.

8. An ammonia pipeline using the ammonia detection system described in claim 7.

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