Moisture sensors and their applications

Abstract

To provide a moisture sensor with improved responsiveness and its applications. [Solution] A moisture sensor according to one embodiment of the present invention comprises an insulating substrate and at least two fine wire electrodes arranged adjacently on the insulating substrate at a fine interval, and is a moisture sensor that detects the presence or absence of liquid droplets in contact with the fine wire electrodes by current flowing between the fine wire electrodes, characterized in that it is possible to measure the current flowing between the fine wire electrodes while a DC current is flowing by applying a predetermined voltage between the fine wire electrodes for a certain period of time.

Description

[Technical Field]

[0001] This invention relates to a moisture sensor and its applications. [Background technology]

[0002] Conventionally, wet / dry response sensors based on galvanic action have been developed. For example, Patent Document 1 discloses a sensor having a structure in which two different types of fine metal wires are placed side by side on an insulating substrate at minute intervals. Furthermore, Patent Document 2 proposes improving the detection sensitivity of a sensor having a structure similar to that of Patent Document 1 by making the surface between the metal wires hydrophilic or hydrophobic.

[0003] In the sensors described in Patent Documents 1 and 2, since the fine wires (electrodes) are made of different metals, when conductive droplets such as water droplets connect the metal fine wires, a galvanic current flows due to the difference in the electrochemical potential of the materials constituting each metal fine wire. A galvanic sensor that measures such a galvanic current has the advantage of not necessarily requiring an external power supply for driving the sensor. Furthermore, by using fine metal wires, the area in which each metal fine wire is in close proximity to the detection area of ​​the sensor can be made longer, which has the advantage of increasing the battery capacity, and thus increasing the galvanic current that can be extracted.

[0004] On the other hand, in practical applications, if the measured galvanic current of the aforementioned galvanic sensor is used directly (i.e., as the raw sensor signal) for the required analysis, the influence of noise signals and other factors that inevitably occur may not be negligible. Therefore, a configuration is usually adopted in which an amplifier is connected to the current collector that bundles each thin metal wire to amplify the galvanic current. However, depending on the application and operating environment of the sensor, it may be desirable to use a configuration that does not use signal amplification means such as an amplifier, and there is still a need to improve the responsiveness of the sensor. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2016 / 013544 [Patent Document 2] International Publication No. 2019 / 044640 [Non-patent literature]

[0006] [Non-Patent Document 1] Yusuke Kubota et al., Micro / nano galvanic-coupled arrays for early and initial detection and prediction of dew condensation, SENS ACTUATOR A PHYS, Vol. 303, 2020, 111838. [Overview of the project] [Problems that the invention aims to solve]

[0007] In view of the above circumstances, the present invention aims to provide a moisture sensor with improved responsiveness. Furthermore, the present invention also aims to provide applications for the moisture sensor. [Means for solving the problem]

[0008] In the conventional galvanic sensors described above, the measurement principle did not anticipate any electrical treatment being applied between the metal wires to prevent water droplets (liquid droplets) present between the metal wires from impairing their ability to connect the electrodes. Specifically, it was believed that if a voltage was intentionally applied between the metal wires while water droplets were present, electrolysis of the water would occur, causing the galvanic current that should have been obtained to disappear.

[0009] However, the inventors, free from such preconceptions, conducted repeated trials and errors and found that the above objective can be achieved with the following configuration.

[0010] The moisture sensor according to the present invention includes an insulating substrate and at least two or more fine wire electrodes adjacently arranged on the insulating substrate at a fine interval. In the moisture sensor capable of detecting the presence or absence of droplets contacting the fine wire electrodes by the current flowing between the fine wire electrodes, a predetermined voltage is applied between the fine wire electrodes for a certain period of time to measure the current flowing between the fine wire electrodes while passing a direct current, thereby solving the above problems. Here, the value and application time of the voltage may be variable, and it may be configured to measure the current flowing between the fine wire electrodes while passing a direct current between the fine wire electrodes by combining a plurality of conditions. The plurality of conditions may include a condition where no voltage is applied between the fine wire electrodes.

[0011] The fine wire electrodes may have a certain interval, and the interval may be 5 nm or more and less than 20,000 nm. Here, the interval may be 100 nm or more and 1000 nm or less. The fine wire electrodes may be composed of a first fine wire electrode and a second fine wire electrode. At least one of the first fine wire electrode and the second fine wire electrode may be provided in a plurality of numbers, and the first fine wire electrode and the second fine wire electrode may extend from the direction facing each other toward the other side, and may run parallel to each other. The first fine wire electrode and the second fine wire electrode may be made of the same kind of metal or the same kind of carbon material. Here, the metal may be selected from the group consisting of gold (Au), platinum (Pt), silver (Ag), titanium (Ti), iron (Fe), cobalt (Co), chromium (Cr), nickel (Ni), molybdenum (Mo), manganese (Mn), and alloys thereof. Alternatively, the first fine wire electrode and the second fine wire electrode may be made of different materials. Here, the material of the first fine wire electrode may be selected from the group consisting of gold (Au), platinum (Pt), silver (Ag), titanium (Ti), iron (Fe), cobalt (Co), chromium (Cr), nickel (Ni), molybdenum (Mo), manganese (Mn), and alloys thereof, and carbon materials, and the material of the second fine wire electrode may be selected from the group consisting of silver (Ag), copper (Cu), iron (Fe), nickel (Ni), cobalt (Co), tin (Sn), chromium (Cr), molybdenum (Mo), manganese (Mn), aluminum (Al), zinc (Zn), magnesium (Mg), and alloys thereof.

[0012] The dew condensation detection device according to the present invention includes the above-described moisture sensor and voltage application means, and has a configuration in which at least the moisture sensor is disposed in a predetermined closed space, thereby solving the above problems. Here, the dew condensation detection device may detect the dew condensation state of the object to be measured disposed in the closed space and / or the dew condensation state of the member constituting the closed space. The dew condensation detection device may have a configuration in which the moisture sensor and the voltage application means are disposed in the closed space. The object to be measured may include an electronic substrate, and the voltage application means may be configured using an electronic circuit formed on the electronic substrate. The moisture sensor may be disposed to face at least a part of the substrate of the electronic substrate or an electronic circuit formed on the electronic substrate.

[0013] The dew condensation detection system according to the present invention includes the above-described dew condensation detection device, thereby solving the above problems. [[ID=IP18]]Here, the dew condensation detection system may include data extraction means, data analysis means, and / or data display means.

Advantages of the Invention

[0014] The present invention provides a moisture sensor with improved responsiveness. Furthermore, the present invention provides, for example, a condensation detection device comprising the moisture sensor and a voltage application means as an application of the moisture sensor. Moreover, the condensation detection device can also constitute a condensation detection system comprising it.

[0015] The moisture sensor of the present invention has a responsiveness superior to conventional galvanic sensors, enabling highly sensitive detection of condensation even in the very early stages of condensation formation on the object being measured. In other words, the moisture sensor of the present invention is capable of detecting the presence of latent moisture before condensation becomes apparent on the object being measured, and in this sense can be described as a "latent moisture sensor." This allows for, for example, if the object being measured is an electronic substrate or electronic circuit, to take action at the very early stages of condensation formation, before problems such as corrosion or short circuits occur on the object, enabling necessary inspections and repairs. Furthermore, because the moisture sensor of the present invention exhibits small hysteresis in the response current from the sensor in response to voltage application and adjustment, it is easy to ensure the reproducibility, stability, time dependence, and linearity of the output current value. This reduces errors associated with repeated measurements, and the sensor can be implemented in various devices and equipment as a maintenance-free sensor that does not require calibration and has a long lifespan. In addition, the moisture sensor of the present invention can perform stable measurements even in enclosed environments such as small devices and equipment with small housing volumes, making it suitable for integration into electronic circuit boards and other components already present in the components of the object being measured to detect condensation. [Brief explanation of the drawing]

[0016] [Figure 1] A diagram showing an example of the configuration of the main parts of a moisture sensor according to one embodiment of the present invention. (a) Top view, (b) Cross-sectional view. [Figure 2] (a), (b) Diagrams showing an example configuration of a condensation detection device according to one embodiment of the present invention. [Figure 3] (a), (b) Diagrams showing an example configuration of a condensation detection system according to one embodiment of the present invention. [Figure 4]Measurement results for Example 1. (a) A figure showing the time change of the applied voltage to the moisture sensor (fine wire electrode spacing: 10 μm) and the sensor's response current under the condition of a humidity of 20% RH inside the test enclosure. (b) A graph plotting the relationship between the applied voltage value and the response current value. [Figure 5] Measurement results for Example 1. (a) A figure showing the time change of the applied voltage to the moisture sensor (fine wire electrode spacing: 10 μm) and the sensor's response current under the condition of a humidity of 90% RH inside the test enclosure. (b) A graph plotting the relationship between the applied voltage value and the response current value. [Figure 6] Measurement results for Example 1. (a) A figure showing the time change of the applied voltage to the moisture sensor (fine wire electrode spacing: 10 μm) and the response current of the sensor under conditions of humidity of 140% RH inside the test enclosure. (b) A graph plotting the relationship between the applied voltage value and the response current value. [Figure 7] This figure, created based on the experimental results described in Non-Patent Document 1, summarizes the time evolution of the relative humidity (%RH) on the sensor surface and the sensor's response current (A). [Figure 8] Measurement results for Example 2. (a) A figure showing the time change of the applied voltage to the moisture sensor (fine wire electrode spacing: 0.5 μm) and the response current of the sensor under the condition of a humidity of 20% RH inside the test enclosure. (b) A graph plotting the relationship between the applied voltage value and the response current value. [Figure 9] Measurement results for Example 2. (a) A figure showing the time change of the applied voltage to the moisture sensor (fine wire electrode spacing: 0.5 μm) and the response current of the sensor under conditions of 90% RH humidity inside the test enclosure. (b) A graph plotting the relationship between the applied voltage value and the response current value. [Figure 10-1] Measurement results for Example 2. (a) A figure showing the time change of the applied voltage to the moisture sensor (fine wire electrode spacing: 0.5 μm) and the response current of the sensor under the condition that the humidity inside the test enclosure is 150% RH. (b) A graph plotting the relationship between the applied voltage value and the response current value. [Figure 10-2]Measurement results for Example 2. (c) Figure showing the time change of the applied voltage to the moisture sensor (fine wire electrode spacing: 0.5 μm) and the sensor's response current under the condition that the humidity inside the test enclosure is 150% RH. (d) Graph plotting the relationship between the applied voltage value and the response current value. [Figure 11-1] Measurement results for Example 3 (1st cycle). (a) Figure showing the time change of the applied voltage to the moisture sensor (fine wire electrode spacing: 0.5 μm) and the sensor's response current under the condition that the humidity inside the test enclosure is 15% RH. (b) Graph plotting the relationship between the applied voltage value and the response current value. [Figure 11-2] Measurement results for Example 3 (1st cycle). (c) Figure showing the time change of the applied voltage to the moisture sensor (fine wire electrode spacing: 0.5 μm) and the response current of the sensor under conditions of a humidity of 150% RH inside the test enclosure. (d) Graph plotting the relationship between the applied voltage value and the response current value. [Figure 12-1] Measurement results for Example 3 (3rd cycle). (a) Figure showing the time change of the applied voltage to the moisture sensor (fine wire electrode spacing: 0.5 μm) and the sensor's response current under the condition that the humidity inside the test enclosure is 15% RH. (b) Graph plotting the relationship between the applied voltage value and the response current value. [Figure 12-2] Measurement results for Example 3 (3rd cycle). (c) Figure showing the time change of the applied voltage to the moisture sensor (fine wire electrode spacing: 0.5 μm) and the response current of the sensor under conditions of a humidity of 150% RH inside the test enclosure. (d) Graph plotting the relationship between the applied voltage value and the response current value. [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described in detail below with reference to the attached drawings. The following description of the constituent elements may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.

[0018] [Moisture Sensor] A moisture sensor according to one embodiment of the present invention (hereinafter also referred to as "the moisture sensor of this embodiment") comprises an insulating substrate and at least two fine wire electrodes arranged adjacently on the insulating substrate at a fine interval, and can detect the presence or absence of liquid droplets in contact with the fine wire electrodes by the current flowing between the fine wire electrodes. Here, the moisture sensor of this embodiment is configured to measure the current flowing between the fine wire electrodes while a predetermined voltage is applied between the fine wire electrodes for a certain period of time to allow a DC current to flow.

[0019] Conventionally, attempts have been made to measure the presence and amount of water (water droplets) between predetermined electrodes by applying an AC voltage and calculating the impedance value from the response current, or by analyzing the response current to obtain the resistance and capacitance components. However, the amount (amplitude) of the AC voltage in this case is generally relatively small, around 10mV to 100mV, and the response current obtained is also small, making it susceptible to the influence of noise signals and the like. In addition, since analysis at all frequencies is time-consuming, in practice the impedance value at a specific frequency is used, but it is uncertain whether this value directly reflects the presence and amount of water being measured. In other words, as long as an AC voltage is used, it is practically difficult to avoid doubts about whether the measurement is being affected by noise signals and the like due to the measurement environment. In contrast, the present invention applies a DC voltage between thin wire electrodes and measures the current flowing between the thin wire electrodes while a DC current is flowing between them, thereby detecting the presence or absence of liquid droplets such as water droplets in contact with the thin wire electrodes. This has technical significance beyond simply changing the voltage from AC to DC. In one respect, as will be shown in the embodiments described later, the present invention provides a steady response current even when a voltage exceeding 1.23V, the theoretical decomposition voltage of water, is applied, and the current value changes significantly in response to the absence and presence of liquid droplets between the fine wire electrodes (dry state and wet state), thus exhibiting an excellent sensitivity improvement effect that could not be expected from the conventional level of technology.

[0020] Figure 1 shows an example of the configuration of the main part (detection unit) of the moisture sensor of this embodiment. Figure 1(a) is a top view, and Figure 1(b) is a cross-sectional view taken along line A-A'.

[0021] As shown in Figure 1(a), the moisture sensor 100 comprises a substrate (insulating substrate) 110 and a fine wire electrode 120.

[0022] Typically, the insulating substrate 110 can be a silicon substrate with an oxide film (SiO2 film) formed on its surface. However, the insulating substrate 110 is not limited to such a silicon substrate; for example, plastics such as polycarbonate, rubber, and various other insulating materials can also be used. Furthermore, even if the substrate body is a conductor such as metal, a substrate that provides insulation in relation to the fine wire electrode 120 by forming an insulating coating or covering on it is also included in the category of "insulating substrate" in this application.

[0023] The fine wire electrode 120 is composed of a first fine wire electrode 122 and a second fine wire electrode 124. The first fine wire electrode 122 and the second fine wire electrode 124 are placed side by side on an insulating substrate 110. That is, the first fine wire electrode 122 and the second fine wire electrode 124 are placed adjacent to each other on the insulating substrate 110 with a fine gap between them. Here, it is preferable that the gap between the first fine wire electrode 122 and the second fine wire electrode 124 (i.e., the values ​​of d1 and d2 in Figure 1(b)) is constant. From the viewpoint of the manufacturing process, the lower limit of this gap may be 5 nm. Also, the upper limit of this gap is not particularly limited, but it can be less than 20 μm (20,000 nm). In other words, it is preferable that the gap is 5 nm or more and less than 20,000 nm. Any value can be selected within this range, but for example, the interval may be 20 nm to 15,000 nm, 50 nm to 12,500 nm, or 100 nm to 10,000 nm. The examples described later show measurement examples when the spacing of the fine wire electrodes is 0.5 μm (500 nm) and 10 μm (10,000 nm). In one case, the diameter of a water droplet that has just condensed in the atmosphere and is floating in the air before growing due to collisions with other water droplets is approximately 1 μm to 10 μm, so if the intention is to achieve a resolution of 1 / 10 of this diameter, the interval may be 100 nm to 1,000 nm. This makes it easier to ensure the sensitivity and accuracy of the moisture sensor.

[0024] In the moisture sensor 100, it is preferable that at least one of the first nanowire electrode 122 and the second nanowire electrode 124 is provided in multiple quantities. In the example configuration shown in Figure 1, four first nanowire electrodes 122 and four second nanowire electrodes 124 are provided, but this is merely an example.

[0025] In the configuration example shown in Figure 1, the first thin wire electrode 122 and the second thin wire electrode 124 are each connected at one end to the first current collector 130 and the second current collector 140. That is, the first thin wire electrode 122 and the second thin wire electrode 124 extend toward each other from the first current collector 130 and the second current collector 140, which are positioned opposite each other, and thus run parallel to each other. Here, increasing the length of the portion where the first thin wire electrode 122 and the second thin wire electrode 124 are in close proximity and facing each other (hereinafter referred to as the parallel running distance) can increase the battery capacity. For this reason, in one embodiment, it is preferable to arrange the first thin wire electrode 122 and the second thin wire electrode 124 substantially parallel to each other over a long distance. Configurations that make this possible include, in addition to the comb-shaped structure shown in Figure 1, making the thin wire electrode 120 a double spiral structure, for example. Furthermore, since the structure for maximizing the parallel distance between two wires within a certain planar area is well known in the semiconductor device field and other areas, such a structure can be adopted as needed. In this invention, "arranging fine wire electrodes side by side on a substrate" does not specify the relative orientation of multiple fine wire electrodes placed on the substrate, but rather means arranging the fine wire electrodes spaced apart on the same plane of the substrate.

[0026] In one embodiment, the first fine wire electrode 122 and the second fine wire electrode 124 are made of the same metal or the same carbon material. Here, the metal can be selected from the group consisting of gold (Au), platinum (Pt), silver (Ag), titanium (Ti), iron (Fe), cobalt (Co), chromium (Cr), nickel (Ni), molybdenum (Mo), manganese (Mn), and alloys thereof. The carbon material can be selected from the group consisting of carbon (C) and its allotropes.

[0027] In another embodiment, the first nanowire electrode 122 and the second nanowire electrode 124 are composed of different materials. Here, as the material for the first nanowire electrode 122, when the first nanowire electrode 122 is the anode, examples include gold (Au), platinum (Pt), silver (Ag), titanium (Ti), iron (Fe), cobalt (Co), chromium (Cr), nickel (Ni), molybdenum (Mo), manganese (Mn) and their alloys, as well as carbon materials (carbon (C) and its allotropes), iridium oxide, and ruthenium oxide. Furthermore, when the second fine wire electrode 124 is used as the cathode, examples of materials for the second fine wire electrode 124 include silver (Ag), copper (Cu), iron (Fe), nickel (Ni), cobalt (Co), tin (Sn), chromium (Cr), molybdenum (Mo), manganese (Mn), aluminum (Al), zinc (Zn), magnesium (Mg), and alloys thereof. However, when silver (Ag), iron (Fe), cobalt (Co), chromium (Cr), nickel (Ni), molybdenum (Mo), manganese (Mn), and their alloys are used as the first fine wire electrode 122, materials other than silver (Ag), iron (Fe), cobalt (Co), chromium (Cr), nickel (Ni), molybdenum (Mo), manganese (Mn), and their alloys are used as the material for the second fine wire electrode 124.

[0028] The latter embodiment can refer to the combination of electrode materials in conventional galvanic sensors. However, since the moisture sensor of this embodiment improves the responsiveness of the sensor without relying on the conventional galvanic method, the former embodiment can be adopted. In other words, in the moisture sensor of this embodiment, the configuration of the thin wire electrode may be such that a galvanic current can be generated, but this configuration is not an essential requirement.

[0029] The moisture sensor of this embodiment can be used to detect the condensation state of an object being measured, specifically by detecting the transition from a state where no condensation has occurred to a state where condensation has occurred. In other words, in this embodiment, the sensor can be said to have fulfilled its required performance if it can detect the state where condensation has occurred at least once. On the other hand, the moisture sensor of this embodiment is not limited to this embodiment, but can also be used to detect the transition from a state where condensation has occurred to a state where condensation has been resolved, while ensuring reproducibility and stability of operation.

[0030] This finding was confirmed through the inventors' experimental verification, and while it may have seemed possible in terms of the measurement principle when using conventional galvanic type sensors, it was not necessarily clear.

[0031] In other words, as mentioned above, in conventional galvanic sensors, it was thought that if a voltage was intentionally applied between metal wires with water droplets attached, electrolysis of the water would occur, and the galvanic current that should have been obtained would disappear. Therefore, the idea of ​​applying a voltage during measurement was ruled out, and instead, the focus was on amplifying the galvanic current output from the sensor using an amplifier or the like.

[0032] However, the inventors have found that even when a voltage is applied between metal nanowires while a liquid droplet is in contact with the electrodes, the sensor signal does not disappear; rather, the output current value increases. Furthermore, it is noteworthy that when the applied voltage value is changed, an increase or decrease in the output current value is observed, and the hysteresis of the response current from the sensor in response to the application or increase / decrease of voltage is small. This is a desirable feature from the standpoint of reducing or eliminating the influence of noise signals and other factors that can be a concern with conventional galvanic type sensors.

[0033] As a result, the moisture sensor of this embodiment can easily ensure superior time response and linearity of the output signal compared to conventional galvanic sensors. Having these characteristics, the moisture sensor of this embodiment is suitable for use in environments where continuous detection of changes in condensation conditions over long periods is required.

[0034] In embodiments used in such environments, the moisture sensor of this embodiment may have a constant voltage applied between the nanowire electrodes. In this case, examples of such voltage values ​​include 3.3V and 5V, which are typical power supply voltages for electronic circuits. Alternatively, an arbitrary value may be set based on the power supply voltage of the electronic circuit being measured, as long as it does not exceed the aforementioned voltage value. Furthermore, the moisture sensor of this embodiment may have a variable voltage value and application time between the nanowire electrodes, and may be configured to measure the current flowing between the nanowire electrodes while a DC current flows between them by combining multiple conditions. In addition, the above multiple conditions may include a condition in which no voltage is applied between the nanowire electrodes. In this case, for example, the response current values ​​obtained when applying arbitrary different voltages in an actual usage environment or under conditions that simulate the environment can be confirmed, and based on these results, conditions that increase from a small voltage value (which may be zero) to a large voltage value, conditions that decrease from a large voltage value to a small voltage value (which may be zero), or conditions that combine these can be adopted. Here, the application time at each voltage value may be the same or different. Furthermore, the upper limit of the voltage value is intended to be a value that does not exceed the power supply voltage of the electronic circuit being measured.

[0035] The environment in which the moisture sensor of this embodiment can be applied is not particularly limited, as long as a configuration that allows voltage to be applied between fine wire electrodes can be adopted. Examples include environments in which objects whose electrical, chemical, and / or physical properties may be impaired due to condensation are installed or used. Specifically, for example, the inside of the casing of electronic equipment, the inside of the casing of devices that utilize chemical reactions (such as lithium-ion batteries), and / or the casings of various devices and equipment themselves can be targeted, and the moisture sensor of this embodiment can be used to detect the condensation state in these environments.

[0036] [Condensation detection device] Next, the condensation detection device of the present invention will be described.

[0037] A condensation detection device according to one embodiment of the present invention (hereinafter also referred to as "the condensation detection device of this embodiment") comprises at least the above-described moisture sensor and a voltage application means. The moisture sensor and the voltage application means may be arranged within a predetermined closed space, or the moisture sensor may be arranged within the closed space and the voltage application means may be arranged outside the closed space. Typically, the condensation detection device of this embodiment detects the condensation state of an object to be measured, which is placed within the closed space in which the moisture sensor is located, and / or the condensation state of the members constituting the closed space.

[0038] In this specification, "closed space" refers to the internal space of an enclosure, storage box, etc. (hereinafter referred to and collectively as "enclosure" for convenience) having a certain volume. Here, the enclosure may or may not have slits or holes for ventilation purposes. Furthermore, regardless of the presence or absence of such slits, the internal space will be treated as a "closed space" even if defects such as cracks occur due to aging or unintended impacts. In this context, "components constituting the closed space" means the "enclosure" as described above.

[0039] In an exemplary embodiment, the "closed space" may be the internal space of an electronic device enclosure, in which an electronic circuit board (including electronic circuits formed on the circuit board, etc.) constituting the electronic device may be arranged. Alternatively, in another exemplary embodiment, the "closed space" may be the internal space of an enclosure (storage box, storage room, etc.) in which various devices and equipment such as electronic devices are stored.

[0040] In the former embodiment, the object to be measured for detecting condensation may be the electronic substrate and / or an electronic circuit formed on the electronic substrate. Here, it is preferable that the moisture sensor is positioned in close proximity to the object to be measured within the closed space. Furthermore, it is more preferable that the moisture sensor is positioned on the substrate of the electronic substrate or opposite at least a part of the electronic circuit formed on the electronic substrate. This makes it easier to ensure the sensitivity and accuracy of the moisture sensor.

[0041] In the latter embodiment, the moisture sensor may be placed in the closed space together with the voltage application means described later, and additional devices may be placed together with the moisture sensor. For example, a temperature control device may be provided as an additional device, and the temperature control device may be thermally connected to the moisture sensor. This makes it possible to adjust the temperature of the moisture sensor, more specifically the temperature of the detection part of the moisture sensor, and to control the relative humidity near the fine wire electrode that constitutes the detection part. Here, an example of the temperature control device is a Peltier element. Alternatively, a configuration with high thermal conductivity can be adopted by thermally connecting the moisture sensor and the temperature control device using a heat pump or the like. In this way, by controlling the relative humidity near the fine wire electrode in advance, the responsiveness of the moisture sensor to changes (increases) in the relative humidity of the internal space of the housing can be further improved.

[0042] As a variation of the latter embodiment described above, a temperature control device may be used to intentionally lower the temperature of the moisture sensor below the dew point, thereby actively inducing condensation on the moisture sensor. This variation may be effective when it is difficult to detect condensation using a combination of a moisture sensor and a voltage application means due to the type of object being measured, the measurement environment, etc. For example, if the "closed space" is the internal space of piping or the like that which constitutes a certain piece of equipment or device, by further combining it with a temperature control device, it may be possible not only to detect the condensation state of the piping or other components that constitute the closed space, but also to detect water (water vapor or fog) in the gas (fluid flowing through the closed space) present in the closed space.

[0043] Furthermore, in another variation of the latter embodiment described above, the "closed space" may be the internal space of a refrigeration enclosure (refrigerator, refrigerator compartment, etc.). In this case, the moisture sensor may be placed inside the closed space together with the voltage application means described later, or the moisture sensor may be placed inside the closed space and the voltage application means may be placed outside the closed space together with the refrigeration electronic circuit. In this variation, the temperature of the moisture sensor is adjusted when the enclosure is closed, so the relative humidity near the aforementioned thin wire electrode is also controlled. When the enclosure is opened, outside air flows into the internal space of the enclosure, causing the relative humidity of the internal space to change (typically increase), and this change can be monitored with high accuracy by the moisture sensor.

[0044] Furthermore, an example of a case where the voltage application means is located outside the closed space where the moisture sensor is placed is, for example, when detecting condensation in air conditioning equipment, ventilation equipment, electric motors, fans (for cooling, etc.). In these types of equipment and devices, even if an electronic circuit board is located in the closed space where the moisture sensor is placed, and the voltage application means can be configured using that electronic circuit board, intentionally placing the voltage application means outside the closed space may help avoid the influence of noise signals and the like during measurement.

[0045] The voltage application means described above is configured to allow a DC current to flow by applying a predetermined voltage between the thin wire electrodes of the moisture sensor for a certain period of time. Here, the voltage application means is not particularly limited, but in a typical embodiment of the condensation detection device of this embodiment, the voltage application means can be configured using the configuration (or part thereof) of the object to be measured for which the condensation state is detected. That is, if the object to be measured for which the condensation state is detected is equipped with an electronic circuit board, the voltage application means can be configured using the electronic circuit formed on the electronic circuit board. Here, it is preferable that the moisture sensor is positioned on the substrate of the electronic circuit board or opposite at least a part of the electronic circuit formed on the electronic circuit board. This simplifies the wiring connecting the moisture sensor and the voltage application means. Furthermore, since the moisture sensor can be positioned in close proximity to the object to be measured, the condensation state of the object to be measured can be detected more accurately.

[0046] Figure 2 shows an example configuration of a condensation detection device according to one embodiment of the present invention. Figure 2(a) is one aspect of the configuration example, and Figure 2(b) is another aspect of the configuration example.

[0047] The condensation detection device 200 according to the embodiment shown in Figure 2(a) has a closed space CS as the internal space of the housing 210. A test object Obj, which is used to detect condensation, is placed in the closed space CS. In this embodiment, the test object Obj is intended to be an electronic circuit board and an electronic circuit formed on the electronic circuit board. Here, the moisture sensor 100 is placed on one of the test objects Obj (electronic circuit board) and is placed in close proximity to the other test object Obj (electronic circuit). The voltage application means 220 is configured using (part of) the configuration of the electronic circuit which is the test object Obj. The voltage application means 220 is connected to the moisture sensor 100 by wiring 230 and is configured to allow a DC current to flow by applying a predetermined voltage between the thin wire electrodes of the moisture sensor 100 for a certain period of time.

[0048] In the condensation detection device 200 according to the embodiment shown in Figure 2(b), the moisture sensor 100 is positioned opposite a part of the object to be measured Obj (electronic substrate and electronic circuit). The other components are the same as in the embodiment shown in Figure 2(a), so the same reference numerals as in Figure 2(a) are used, and their explanation is omitted.

[0049] In addition, in any of the embodiments described above, it is also possible to include the housing 210 itself, or more specifically, the inner portion of the housing 210, in the object Obj under measurement.

[0050] [Condensation detection system] Next, the condensation detection system of the present invention will be described.

[0051] A condensation detection system according to one embodiment of the present invention (hereinafter also referred to as "the condensation detection system of this embodiment") comprises at least the condensation detection device described above. In addition to the condensation detection device, the condensation detection system of this embodiment may be configured to include, for example, data extraction means, data analysis means, data display means, etc.

[0052] The data extraction means, data analysis means, and data display means described above are not particularly limited, but in a typical embodiment of the condensation detection system of this embodiment, these means can be configured using (part of) the configuration of the object being measured for detecting the condensation state. That is, if the object being measured for detecting the condensation state is, for example, an electronic circuit board constituting a portable terminal and / or an electronic circuit formed on said electronic circuit board, the system can be configured to extract, analyze, and display output data from a moisture sensor using the data extraction function, data analysis function, data display function, etc., provided in the terminal.

[0053] Figure 3 shows an example configuration of a condensation detection system according to one embodiment of the present invention. Figure 3(a) is one aspect of the configuration example, and Figure 3(b) is another aspect of the configuration example.

[0054] In the condensation detection system 300 according to the embodiment shown in Figure 3(a), a data display means 310 is formed in a part of the housing of the condensation detection device 200. In this embodiment, the means for realizing the above-mentioned data extraction function, data analysis function, data display function, etc., can be configured by utilizing (part of) the configuration of the electronic circuit formed on the electronic circuit board arranged inside the condensation detection device 200. In other words, in this embodiment, the data extraction means 320, data analysis means 330, etc., can be arranged inside the housing of the condensation detection device 200.

[0055] Alternatively, as schematically shown in Figure 3(b), a separate device (or instrument) may be provided in addition to the condensation detection device 200, and this device (or instrument) may have functions such as data extraction, data analysis, and data display. Here, Figure 3(b) shows an example where there is only one such device (or instrument), but a configuration using separate devices (or instruments) for each required function is also possible. Furthermore, in Figure 3(b), the condensation detection device 200 and the aforementioned device (or instrument) are connected by solid lines, but this merely schematically shows that data from the condensation detection device 200 is transferred. In other words, data from the condensation detection device 200 may be transferred via wired communication, wireless communication, or a recording medium, etc.

[0056] Embodiments of the present invention will be described in more detail below based on the following examples. However, the scope of the present invention should not be interpreted as being limited by the following examples. [Examples]

[0057] [Example 1] A silicon wafer (500 μm thick) with an SiO2 film (100 nm thick) formed on its surface was prepared as the substrate. A comb-shaped structure of nanowire electrodes was formed on this silicon wafer by placing a first nanowire electrode and a second nanowire electrode side by side (see Figure 1). Here, the material of the first nanowire electrode and the first current collector was gold, and the material of the second nanowire electrode and the second current collector was aluminum. The wire width of the first nanowire electrode and the second nanowire electrode was 2 μm, the height was 200 nm, and the length was 1300 μm. The distance between the first nanowire electrode and the second nanowire electrode was 10 μm, and the number of pairs consisting of the first nanowire electrode and the second nanowire electrode was 47.

[0058] A moisture sensor with the above configuration as its detection unit was installed inside a housing (external dimensions: approximately 30 mm x 40 mm x 20 mm). A voltage application means was placed inside the housing, and a predetermined voltage was configured to be applied to the first and second current collectors of the moisture sensor for a certain period of time. A ventilation slit was provided at one end of the housing. Hereafter, the housing with the moisture sensor and voltage application means installed inside will also be referred to as the "test housing".

[0059] This test enclosure was placed inside a measurement chamber. This measurement chamber (also simply referred to as the "chamber") has a gas inlet, through which conditioned gas supplied from a humidity control device is introduced into the chamber. A temperature and humidity probe is inserted into the chamber, allowing for monitoring of the temperature and humidity inside the chamber. A temperature control device is located at the bottom of the chamber, and the test enclosure is placed on top of this temperature control device. This allows for control of the temperature (and humidity) environment inside the enclosure by changing the temperature of the test enclosure in accordance with the operation of the temperature control device (heating up or cooling down). A Peltier element was used as the temperature control device. Although wiring necessary for measurement is inserted into the chamber as appropriate, the chamber's airtightness is maintained during measurement.

[0060] Using the measurement chamber described above, the humidity inside the chamber was varied, and the applied voltage by the voltage application means was changed to allow a DC current to flow between the thin wire electrodes. The response current output from the moisture sensor was then measured. The applied voltage was increased stepwise from zero to 5 volts (V) by 0.5V every minute, and then decreased stepwise by 0.5V every minute until it reached zero. The results are shown in Figures 4 to 6.

[0061] Figure 4(a) shows the time variation of the applied voltage and the sensor's response current (Output) under the condition that the humidity inside the test enclosure is 20% RH. Under these humidity conditions, the inside of the test enclosure can be considered dry. As shown in Figure 4(a), in the applied voltage profile described above, the sensor's response current is 1 × 10⁻⁶. -12 ~1 × 10 -10 It remained fairly stable in the range of less than amperes (A).

[0062] Figure 4(b) is a graph plotting the relationship between the applied voltage value and the response current value based on the results in Figure 4(a). According to Figure 4(b), it was found that the degree of agreement between the maximum, minimum, and average values ​​of the response current measured under the same applied voltage was high in both the stage of increasing the applied voltage (Upward) and the stage of decreasing the applied voltage (Downward).

[0063] Figure 5(a) shows the time evolution of the applied voltage and the sensor's response current under the condition that the humidity inside the test enclosure is 90% RH. Under these humidity conditions, the inside of the test enclosure is in a high-humidity state, and condensation can occur on components placed inside the enclosure. As shown in Figure 5(a), in the applied voltage profile described above, the sensor's response current is 1 × 10⁻¹⁰ when the applied voltage is less than 3V. -12 ~1 × 10 -10 It is in the range of less than A, but an increase in current value is observed when it is 3V or higher, and when it is 4V or higher, 1 × 10 -10 A was reached.

[0064] Figure 5(b) is a graph plotting the relationship between the applied voltage value and the response current value based on the results in Figure 5(a). According to Figure 5(b), similar to Figure 4(b) (under the condition of 20% RH humidity), it was found that there was a high degree of agreement between the maximum, minimum, and average values ​​of the response current measured under the same applied voltage in the stage of increasing the applied voltage and the stage of decreasing the applied voltage.

[0065] Figure 6(a) shows the time evolution of the applied voltage and the sensor's response current under conditions where the humidity inside the test enclosure is 140%RH. Under these humidity conditions, condensation occurs inside the test enclosure, and if this condition persists, it is highly likely that defects will occur in the components placed inside the enclosure or in the enclosure itself. As shown in Figure 6(a), in the applied voltage profile described above, the sensor's response current tends to increase with increasing applied voltage, and at 3V it is 1 × 10⁻⁶. -9 If it reaches A, and furthermore, if it is 4V or higher, then 1 × 10 -8 The value was greater than or equal to A.

[0066] Figure 6(b) is a graph plotting the relationship between the applied voltage value and the response current value based on the results in Figure 6(a). According to Figure 6(b), similar to Figure 4(b) (under conditions of 20% RH humidity) and Figure 5(b) (under conditions of 90% RH humidity), it was found that there was a high degree of agreement between the maximum, minimum, and average values ​​of the response current measured under the same applied voltage in the stages of increasing and decreasing the applied voltage.

[0067] [Comparative Example] Here, for comparison with conventional galvanic sensors, we refer to the experimental results reported in Non-Patent Document 1.

[0068] The galvanic sensor described in Non-Patent Document 1 uses, as a substrate, a silicon wafer (thickness: 500 μm) with a SiO2 film (thickness: 150 nm) formed on its surface. On the silicon wafer, a first fine wire electrode and a second fine wire electrode are juxtaposed to form a fine wire electrode having a comb-shaped structure. Here, the material of the first fine wire electrode (anode) is gold, and the material of the second fine wire electrode (cathode) is aluminum. The wire width of the first fine wire electrode and the second fine wire electrode is 1 μm, the height is 150 nm, and the length is 1000 μm. The distance between the first fine wire electrode and the second fine wire electrode is 10 μm and 0.5 μm. Also, the number of pairs consisting of the first fine wire electrode and the second fine wire electrode is 50.

[0069] FIG. 7 is a diagram collectively showing the time changes of the relative humidity (%RH) on the sensor surface and the response current (A) of the sensor, created based on the experimental results described in Non-Patent Document 1.

[0070] In FIG. 7, when the distance between the fine wire electrodes is 10 μm, it can be seen that under the condition where the relative humidity on the sensor surface is 90%RH, the response current of the sensor is less than 1×10 -12 A. Comparing this with FIG. 5(a) above, when the applied voltage is 4 V or more, a current value of about 1×10 -10 A is obtained. Therefore, it can be said that the moisture sensor of the present invention has a response current of the sensor improved by two digits or more compared with the conventional galvanic sensor.

[0071] [Example 2] A test housing was fabricated in the same procedure as in Example 1 above. Here, the distance between the first fine wire electrode and the second fine wire electrode in the moisture sensor was set to 0.5 μm, and the number of pairs consisting of the first fine wire electrode and the second fine wire electrode was set to 92.

[0072] This test enclosure was placed inside a measurement chamber. The configuration of the measurement chamber was the same as in Example 1. Using this measurement chamber, the humidity inside the chamber was changed, and the applied voltage by the voltage application means was changed to flow a DC current between the thin wire electrodes, while the response current output from the moisture sensor was measured. Here, the applied voltage was increased stepwise from zero to 5 volts (V) by 0.5V every minute, and then decreased stepwise by 0.5V every minute until it reached zero. The results are shown in Figures 8 to 10.

[0073] Figure 8(a) shows the time variation of the applied voltage and the sensor's response current (Output) under the condition that the humidity inside the test enclosure is 20% RH. Under these humidity conditions, the inside of the test enclosure can be considered dry. As shown in Figure 8(a), in the applied voltage profile described above, the sensor's response current is 1 × 10⁻⁶. -12 ~1 × 10 -10 It remained fairly stable in the range of less than amperes (A).

[0074] Figure 8(b) is a graph plotting the relationship between the applied voltage value and the response current value based on the results in Figure 8(a). According to Figure 8(b), it was found that the degree of agreement between the maximum, minimum, and average values ​​of the response current measured under the same applied voltage was high in both the stage of increasing the applied voltage (Upward) and the stage of decreasing the applied voltage (Downward).

[0075] Figure 9(a) shows the time evolution of the applied voltage and the sensor's response current under the condition that the humidity inside the test enclosure is 90% RH. Under these humidity conditions, the inside of the test enclosure is in a high-humidity state, and condensation can occur on the components placed inside the enclosure. As shown in Figure 9(a), in the applied voltage profile described above, the sensor's response current is 1 × 10⁻¹⁰ when the applied voltage is less than 3V. -12 ~1 × 10 -10 It is in the range of less than A, but an increase in current value is observed when it is 3V or higher, and when it is 4V or higher, 1 × 10 -10 The value was greater than or equal to A.

[0076] Figure 9(b) is a graph plotting the relationship between the applied voltage value and the response current value based on the results in Figure 9(a). According to Figure 9(b), similar to Figure 8(b) (under the condition of 20% RH humidity), it was found that the degree of agreement between the maximum, minimum, and average values ​​of the response current measured under the same applied voltage was high in both the stage of increasing the applied voltage and the stage of decreasing the applied voltage.

[0077] Figures 10(a) and 10(c) show the time evolution of the applied voltage and the sensor's response current under the condition that the humidity inside the test enclosure is 150% RH. Under these humidity conditions, condensation occurs inside the test enclosure, and if this condition persists, it is highly likely that defects will occur in the components placed inside the enclosure or in the enclosure itself. Here, Figure 10(a) shows the range of the response current value to be the same as that of Figures 4 to 9 described above, and Figure 10(c) shows the range of the response current value to be expanded and the upper limit set to 1 × 10⁻⁶. -3 This is denoted as A. As shown in Figures 10(a) and 10(c), in the above applied voltage profile, the sensor response current tends to increase with increasing applied voltage, and in the case of 1V, it is 1 × 10⁻⁶. -8 It reaches A, and furthermore, in the case of 5V, 1 × 10 -4 The value exceeded A.

[0078] Figures 10(b) and 10(d) are graphs plotting the relationship between the applied voltage value and the response current value based on the results from Figures 10(a) and 10(c). As shown in Figures 10(b) and 10(d), similar to Figure 8(b) (under conditions of 20% RH humidity) and Figure 9(b) (under conditions of 90% RH humidity), it was found that there was a high degree of agreement between the maximum, minimum, and average values ​​of the response current measured under the same applied voltage in both the stage of increasing and decreasing the applied voltage.

[0079] Now, referring again to Figure 7 mentioned above, we will explain the comparison with a conventional galvanic sensor.

[0080] In Figure 7, when the spacing between the fine wire electrodes is 0.5 μm, and the relative humidity of the sensor surface is 90% RH, the sensor's response current is 1 × 10⁻¹⁰ -12 It can be seen that it is approximately A. Furthermore, even under conditions where the relative humidity of the sensor surface exceeds 100%RH, the sensor's response current is 1 × 10⁻⁶. -11 Even if the value is less than A and the spacing between the thin wire electrodes is 10 μm, 1 × 10 -11 ~2×10 -11 It can be said that it is approximately A. Comparing these with Figure 10(c) above, when the applied voltage is 1V, it is 1 × 10 -8 It has reached A, and in the case of 5V it is 1 × 10 -4 Since it exceeds A, it can be said that the moisture sensor of the present invention has an improved response current of at least three orders of magnitude compared to conventional galvanic type sensors, and that by adjusting the applied voltage, an improvement in responsiveness of about seven orders of magnitude can be obtained.

[0081] [Example 3] A test enclosure was fabricated using the same procedure as in Example 2 described above, and this test enclosure was placed inside the measurement chamber described above. The distance between the first nanowire electrode and the second nanowire electrode in the moisture sensor was 0.5 μm, and the number of pairs consisting of the first nanowire electrode and the second nanowire electrode was 92.

[0082] Using this measurement chamber, the humidity inside the test enclosure was changed from 15%RH (dry state) to 150%RH (condensation state), and the response current output from the moisture sensor was measured while a DC current was passed between the thin wire electrodes by changing the applied voltage using the voltage application means (1st cycle). Here, the applied voltage was increased stepwise from zero to 5 volts (V) by 0.5V every second, and then decreased stepwise by 0.5V every second until it reached zero. After that, the humidity inside the chamber was reduced to return the inside of the test enclosure to a dry state, and then the inside of the test enclosure was changed again to a condensation state, and the response current of the moisture sensor was measured using the above applied voltage profile (2nd cycle). Subsequently, this procedure was repeated several times to perform measurements in the 3rd cycle and beyond.

[0083] Figure 11 shows the measurement results for the first cycle, and Figure 12 shows the measurement results for the third cycle.

[0084] Figures 11(a) and 12(a) show the time evolution of the applied voltage and the sensor's response current (Output) under the condition that the humidity inside the test enclosure is 15% RH. As shown in Figures 11(a) and 12(a), in the applied voltage profile described above, the sensor's response current is approximately 1 × 10⁻¹⁶ in both the first and third cycles. -12 ~1 × 10 -9 It remained fairly stable in the range of less than amperes (A).

[0085] Figures 11(b) and 12(b) are graphs plotting the relationship between the applied voltage value and the response current value, respectively, based on the results from Figures 11(a) and 12(a). Figures 11(b) and 12(b) show that the degree of agreement between the maximum, minimum, and average values ​​of the response current measured under the same applied voltage was high in both the stage of increasing the applied voltage (Upward) and the stage of decreasing the applied voltage (Downward).

[0086] Figures 11(c) and 12(c) show the time evolution of the applied voltage and the sensor's response current under conditions of a humidity of 150% RH inside the test enclosure. As shown in Figures 11(c) and 12(c), in the applied voltage profile described above, the sensor's response current tends to increase with increasing applied voltage in both the first and third cycles, and is approximately 1 × 10⁻¹⁶ at 1V. -9 It reaches A, and furthermore, in the case of 5V, 1 × 10 -4 The value exceeded A.

[0087] Figures 11(d) and 12(d) are graphs plotting the relationship between the applied voltage value and the response current value, respectively, based on the results from Figures 11(c) and 12(c). As can be seen from Figures 11(d) and 12(d), similar to Figures 11(b) and 12(b) (under the condition of 15% RH humidity), the degree of agreement between the maximum, minimum, and average values ​​of the response current measured under the same applied voltage was high in both the stage of increasing and decreasing the applied voltage.

[0088] Although not shown in the figures, the same results as those obtained for the first and third cycles described above were obtained in measurements from the fourth cycle onward.

[0089] These results indicate that the moisture sensor of the present invention exhibits low hysteresis in the response current from the sensor in response to voltage application and adjustment, and reduced errors associated with repeated measurements, resulting in a sensor with excellent reproducibility and stability of output current values. This means that the moisture sensor of the present invention can be used not only to detect the transition from a state without condensation to a state where condensation has occurred, but also to detect the transition from a state where condensation has occurred to a state where condensation has been resolved on the object being measured, while ensuring reproducibility and stability of operation. [Industrial applicability]

[0090] The moisture sensor with improved responsiveness according to the present invention is suitable for use in detecting the condensation state of an object to be measured placed in a specific enclosed space. Specifically, for example, in portable terminals (smartphones, wearable devices, etc.); various indoor or outdoor measuring devices, monitoring equipment, IoT sensors; the vehicle and aerospace field (battery control devices for automobiles and aircraft, etc.); and the information and communication field (servers and network equipment placed in server rooms, etc.), the object to be measured can be the electronic circuit board and / or the electronic circuit formed on the electronic circuit board that constitute the target equipment or device. Furthermore, since the moisture sensor of the present invention is also suitable for modularization, it is expected that it can be standardized in the design and development of the above-mentioned equipment and devices, and thus developed as a security standard related to operation and maintenance. Alternatively, it is considered possible to construct safety devices that utilize information on the humidity state of the target environment as an indicator by combining the moisture sensor of the present invention with existing circuit breakers, etc. [Explanation of symbols]

[0091] 100 Moisture Sensor 110 Insulating substrate 120 Fine wire electrode 122 First thin wire electrode 124 Second nanowire electrode 130 First current collector 140 Second current collector 200 Condensation detection device 210 cabinets 220 Voltage application means 230 Wiring CS closed space Obj Object to be measured 300 Condensation Detection System 310 Data display means 320 Data extraction means 330 Data Analysis Methods

Claims

1. A moisture sensor comprising an insulating substrate and at least two fine wire electrodes arranged adjacently on the insulating substrate at fine intervals, wherein the presence or absence of liquid droplets in contact with the fine wire electrodes can be detected by current flowing between the fine wire electrodes, The system is configured to measure the current flowing between the thin wire electrodes while a predetermined voltage is applied between the thin wire electrodes for a certain period of time to allow a direct current to flow. The voltage value and application time are variable, and the system is configured to measure the current flowing between the thin wire electrodes while a direct current is flowing between them by combining multiple conditions. The aforementioned conditions include a moisture sensor in which no voltage is applied between the thin wire electrodes.

2. The moisture sensor according to claim 1, wherein the fine wire electrodes are spaced at a certain interval, and the interval is 5 nm or more and less than 20,000 nm.

3. The moisture sensor according to claim 2, wherein the interval is 100 nm or more and 1000 nm or less.

4. The aforementioned thin wire electrode is composed of a first thin wire electrode and a second thin wire electrode. Multiple instances are provided of at least one of the first thin wire electrode and the second thin wire electrode. The moisture sensor according to claim 1, wherein the first thin wire electrode and the second thin wire electrode extend from opposite directions toward each other, thereby running parallel to each other.

5. The moisture sensor according to claim 4, wherein the first fine wire electrode and the second fine wire electrode are made of the same metal or the same carbon material.

6. The moisture sensor according to claim 5, wherein the metal is selected from the group consisting of gold (Au), platinum (Pt), silver (Ag), titanium (Ti), iron (Fe), cobalt (Co), chromium (Cr), nickel (Ni), molybdenum (Mo), manganese (Mn), and alloys thereof.

7. A moisture sensor comprising an insulating substrate and at least two fine wire electrodes arranged adjacently on the insulating substrate at fine intervals, wherein the presence or absence of liquid droplets in contact with the fine wire electrodes can be detected by current flowing between the fine wire electrodes, The system is configured to measure the current flowing between the thin wire electrodes while a predetermined voltage is applied between the thin wire electrodes for a certain period of time to allow a direct current to flow. The aforementioned thin wire electrode is composed of a first thin wire electrode and a second thin wire electrode. Multiple instances are provided of at least one of the first thin wire electrode and the second thin wire electrode. The first thin wire electrode and the second thin wire electrode extend from opposite directions toward each other, so that they run parallel to each other. A moisture sensor in which the first and second thin wire electrodes are made of different materials.

8. The moisture sensor according to claim 7, wherein the material of the first fine wire electrode is selected from the group consisting of gold (Au), platinum (Pt), silver (Ag), titanium (Ti), iron (Fe), cobalt (Co), chromium (Cr), nickel (Ni), molybdenum (Mo), manganese (Mn) and alloys thereof, and carbon materials.

9. The moisture sensor according to claim 7, wherein the material of the second fine wire electrode is selected from the group consisting of silver (Ag), copper (Cu), iron (Fe), nickel (Ni), cobalt (Co), tin (Sn), chromium (Cr), molybdenum (Mo), manganese (Mn), aluminum (Al), zinc (Zn), magnesium (Mg), and alloys thereof.

10. The moisture sensor according to claim 7, wherein the voltage value and application time are variable, and the sensor is configured to measure the current flowing between the thin wire electrodes while a direct current is flowing between the thin wire electrodes by combining multiple conditions.

11. The moisture sensor according to claim 10, wherein the aforementioned conditions include a condition in which no voltage is applied between the thin wire electrodes.

12. The moisture sensor according to claim 7, wherein the portion on the insulating substrate in which the first fine wire electrode and the second fine wire electrode run parallel to each other has a comb-shaped structure, and in the comb-shaped structure, the first fine wire electrode and the second fine wire electrode are spaced at a certain distance apart, the distance being 5 nm or more and less than 20,000 nm.

13. The moisture sensor according to claim 12, wherein the interval is 100 nm or more and 1000 nm or less.

14. A condensation detection device comprising a moisture sensor according to any one of claims 1 to 13 and a voltage application means, wherein at least the moisture sensor is arranged in a predetermined closed space.

15. A condensation detection device according to claim 14, which detects the condensation state of an object to be measured placed in the closed space, and / or the condensation state of a member constituting the closed space.

16. The condensation detection device according to claim 14, wherein the moisture sensor and the voltage application means are arranged within the closed space.

17. The object to be measured, placed within the closed space, comprises an electronic circuit board, and the voltage application means is configured using an electronic circuit formed on the electronic circuit board. A condensation detection device according to claim 16, which detects the condensation state of the object to be measured and / or the condensation state of the members constituting the closed space.

18. The condensation detection device according to claim 17, wherein the moisture sensor is disposed on the substrate of the electronic substrate or opposite to at least a portion of an electronic circuit formed on the electronic substrate.

19. A condensation detection system comprising the condensation detection device described in claim 14.

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