Water level and conductivity detection device, conductivity detection device, hydrogen generator, water level and conductivity detection method, and conductivity detection method

Abstract

To detect the conductivity by utilizing a structure of a water level sensor.SOLUTION: Disclosed is a water level and conductivity detecting device which includes a reference electrode (110) to be inserted into a tank in which the liquid should be stored and one or more detection electrodes, and detects the water level in the tank by detecting the presence or absence of continuity between the reference electrode and one or more detection electrodes. One or more detection electrodes includes an object detection electrode (111) covered with an insulator. An electrode portion (110a) other than the reference exposure part (110b) including the lower end of the reference electrode among the reference electrodes and an electrode portion (111a) other than a detection exposure part (111b) including the lower end of the object detection electrode among the object detection electrodes are covered with the insulator, and the conductivity of the liquid in the tank is detected using the reference electrode and the object detection electrode.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a water level and conductivity detection device, a conductivity detection device, a hydrogen generator, a water level and conductivity detection method, and a conductivity detection method. [Background technology]

[0002] A water level sensor is used to detect the water level in a tank. For example, in a hydrogen generator that generates hydrogen by electrolyzing water using an electrolytic cell, a water level sensor is used to monitor the water level in a tank for storing pure water.

[0003] On the other hand, there are cases where it is required to detect the conductivity of the liquid in the tank. For example, in the above-mentioned hydrogen generator, an increase in the conductivity of the water used for electrolysis accelerates the deterioration of the electrolysis cell. For this reason, there are cases where it is required to monitor the conductivity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2004-510151 Summary of the Invention [Problem to be solved by the invention]

[0005] If a conductivity meter is installed in the tank in addition to a water level sensor for detecting the water level, it is possible to detect both the water level and the conductivity (see Figure 15; an explanation of Figure 15 will be provided later). However, this method requires space to install the conductivity meter in the tank, and the cost increases by the installation of the conductivity meter. Also, some ingenuity is required to accurately detect conductivity using the structure of the water level sensor.

[0006] On the other hand, temperature compensation is often required when detecting conductivity. Temperature compensation can be achieved by installing a temperature sensor inside the tank, but there is a concern that components of the temperature sensor (metal ions, etc.) may leak into the liquid inside the tank.

[0007] An object of the present invention is to provide a water level and conductivity detection device that enables accurate detection of water level and conductivity while suppressing increases in installation space or costs, a hydrogen generator using the same, and a water level and conductivity detection method.Another object of the present invention is to provide a conductivity detection device that contributes to suppressing the above concerns, a hydrogen generator using the same, and a conductivity detection method. [Means for solving the problem]

[0008] The water level and conductivity detection device of the present invention is a water level and conductivity detection device that includes a reference electrode and one or more detection electrodes that are inserted into a tank to contain liquid, and detects the water level in the tank by detecting whether or not there is continuity between the reference electrode and the one or more detection electrodes, wherein the one or more detection electrodes include a target detection electrode that is covered with an insulator, and an electrode portion of the reference electrode other than a reference exposed portion including the lower end of the reference electrode, and an electrode portion of the target detection electrode other than a detection exposed portion including the lower end of the target detection electrode, are covered with an insulator, and the conductivity of the liquid in the tank is detected using the reference electrode and the target detection electrode.

[0009] The conductivity detection device of the present invention is a conductivity detection device that detects the conductivity of a liquid in a tank, and is equipped with a temperature sensor that measures the temperature at a measurement target location outside the tank, and performs temperature compensation for the detected conductivity based on the temperature measured by the temperature sensor. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a water level and conductivity detection device that enables accurate conductivity detection while suppressing increases in installation space or costs, a hydrogen generator using the same, and a water level and conductivity detection method. Furthermore, according to the present invention, it is possible to provide a conductivity detection device that contributes to suppressing the above concerns, a hydrogen generator using the same, and a conductivity detection method. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an overall configuration diagram of a hydrogen generator according to a first embodiment of the present invention. [Figure 2] 1 is a schematic perspective view of an electrode unit according to a first embodiment of the present invention. [Figure 3] 3 is a diagram illustrating the positional relationship between a reference electrode and a plurality of detection electrodes and the water level range according to the first embodiment of the present invention. FIG. [Figure 4] FIG. 10 is a diagram showing the results of an experiment (first experiment) using a comparison configuration. [Figure 5] FIG. 1 is an explanatory diagram of a coating structure according to a first embodiment of the present invention. [Figure 6] FIG. 10 is a diagram showing the results of an experiment (second experiment) using a coating configuration. [Figure 7] 4 is a view showing the covered portion and the exposed portion when the exposed portion has no length in the vertical direction according to the first embodiment of the present invention. FIG. [Figure 8] FIG. 10 is a diagram showing the results of an experiment (third experiment) using a coating configuration. [Figure 9] 10A and 10B are diagrams for explaining the behavior of electrons when an exposed portion of a reference electrode and an exposed portion of a detection electrode face each other. [Figure 10] 10A and 10B are diagrams for explaining the behavior of electrons when the exposed portion of the reference electrode and the exposed portion of the detection electrode have no length in the vertical direction. [Figure 11] FIG. 10 is a diagram showing a partial internal configuration of a detection circuit according to Example EX1_1 belonging to the first embodiment of the present invention. [Figure 12] 10 is a flowchart of a calibration process according to Example EX1_1 belonging to the first embodiment of the present invention. [Figure 13] FIG. 10 is a diagram showing a partial internal configuration of a detection circuit according to Example EX1_2 belonging to the first embodiment of the present invention. [Figure 14] FIG. 10 is a diagram illustrating the structure of a reference electrode and a plurality of detection electrodes according to Example EX1_3 belonging to the first embodiment of the present invention. [Figure 15] FIG. 10 is a diagram showing a state in which a conductivity meter is installed in a tank according to a reference method. [Figure 16] FIG. 10 is a diagram illustrating a configuration for performing temperature compensation of electrical conductivity according to a second embodiment of the present invention. [Figure 17] FIG. 10 is a diagram illustrating the structure of an electrolytic cell and a method for setting a measurement target position according to a second embodiment of the present invention. [Figure 18] FIG. 10 is a configuration diagram of a conductivity detecting device according to Example EX2_2 of the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, examples of embodiments of the present invention will be described in detail with reference to the drawings. In each of the drawings, identical parts are designated by the same reference numerals, and redundant explanations of identical parts will be omitted as a general rule. For the sake of simplicity, the present specification may use symbols or signs referring to information, signals, physical quantities, components, etc., and omit or abbreviate the names of the information, signals, physical quantities, components, etc. corresponding to the symbols or signs. For example, the reference electrode referred to by "110" (see FIG. 2) described below may be written as reference electrode 110 or abbreviated as electrode 110, but these all refer to the same thing.

[0013] <<First Embodiment>> A first embodiment of the present invention will be described. Fig. 1 shows an overall configuration diagram of a hydrogen generator 1 according to the first embodiment of the present invention. The hydrogen generator 1 generates hydrogen by electrolyzing water using an electrolysis cell. The hydrogen generator 1 includes a housing CS and components referenced by the reference numerals 10 to 14, 20, 30 to 33, 40 to 42, 50 to 59, 60 to 64, and 70 to 72. The components referenced by the reference numerals 10 to 14, 20, 30 to 33, 40 to 42, 50 to 57, and 60 to 64 are housed within the housing CS. The components referenced by the reference numerals 58, 59, and 70 to 72 are attached to the outer wall of the housing CS.

[0014] Water is stored in the tank 10. The tank 10 has a cylindrical or prismatic cavity inside as a water storage space 10R, and water is stored in the water storage space 10R. However, the shape of the water storage space 10R shown here is merely an example, and the shape can be modified in various ways. In this embodiment, storing water in the tank 10 and storing water in the water storage space 10R are synonymous. The water to be stored in the tank 10 is classified as pure water. A supply port 11 is provided at one end of the upper part of the tank 10, and water is supplied to the tank 10 through the supply port 11.

[0015] An electrode unit 12 is attached to the tank 10. The electrode unit 12 includes a reference electrode and one or more detection electrodes (three detection electrodes in the example of FIG. 1) to be inserted into the tank 10. The water level in the tank 10 (hereinafter simply referred to as the water level) can be detected by detecting the presence or absence of continuity between the electrodes. Furthermore, the electrode unit 12 can also be used to detect the conductivity of the water in the tank 10; details of the electrode unit 12 will be described later. An exhaust trap 13 is also attached to the tank 10.

[0016] The bottom of the tank 10 is connected to a pipe 30 via a check valve 14. Water in the tank 10 is supplied to the electrolytic cell 20 via the pipe 30 via the check valve 14. The electrolytic cell 20 electrolyzes the water supplied via the pipe 30. A portion of the oxygen and water produced by electrolysis in the electrolytic cell 20 is sent to the supply port 11 via a pipe 31. Another portion of the hydrogen and water produced by electrolysis in the electrolytic cell 20 is sent to a water separation trap 40. The water sent to the water separation trap 40 is sent into the tank 10 via a pipe 32 and an exhaust trap 13. The hydrogen-containing gas sent to the water separation trap 40 is sent to a dryer 42 via a hydrogen pipe 41.

[0017] The hydrogen generated in the electrolytic cell 20 and whose purity has been increased in the dryer 42 is sent to a hydrogen pipe 50. The hydrogen pipe 50 is connected to a hydrogen pipe 51 via a water discharge prevention filter 54, and the hydrogen pipe 51 is connected to one end of a hydrogen pipe 52 via a solenoid valve 55. The other end of the hydrogen pipe 52 is connected to a hydrogen generation port 58. The solenoid valve 55 is controlled to an open or closed state by a control and display unit 60. Only when the solenoid valve 55 is in an open state is hydrogen in the hydrogen pipe 51 sent to the hydrogen pipe 52, and as a result, hydrogen generated in the electrolytic cell 20 is output from the hydrogen generation port 58.

[0018] Furthermore, the hydrogen pipe 50 is connected to one end of a hydrogen pipe 53 via a safety valve 56, and the other end of the hydrogen pipe 53 is connected to a hydrogen release port 59. When the pressure inside the hydrogen pipe 50 exceeds a predetermined value, the safety valve 56 connects the hydrogen pipe 50 to the hydrogen pipe 53, causing the hydrogen inside the hydrogen pipe 50 to be released from the hydrogen release port 59. A pressure sensor 57 detects the hydrogen pressure in the hydrogen pipe 50. The hydrogen in each hydrogen pipe is gaseous hydrogen (hydrogen gas).

[0019] A power supply voltage V is applied from the outside of the hydrogen generator 1 to the power supply port 71. POW is input. Power supply voltage V POW is, for example, a commercial AC voltage. The control and display unit 60 is connected to a power port 71, and the power supply voltage V POWThe control and display unit 60 controls the overall operation of the hydrogen generator 1. The control and display unit 60 is driven based on the power supply voltage V POW The control unit 60 includes a power supply circuit that supplies the internal power supply voltage required for operation to each component of the hydrogen generator 1 based on the above. An electrolytic cell power supply circuit 61 included in the control unit 60 supplies a constant current to the electrolytic cell 20. The electrolytic cell 20 performs water electrolysis based on the supplied current. The electrolytic cell 20 is made of a solid polymer membrane.

[0020] The control and display unit 60 further includes a display unit 62, an alarm output unit 63, and a water level and conductivity detection circuit 64. The control and display unit 60 is connected to a signal port 70. An external device (not shown) can be connected to the signal port 70 outside the hydrogen generator 1, and in this case, various signals can be sent and received between the control and display unit 60 and the external device via the signal port 70.

[0021] The display unit 62 is made up of light-emitting diodes, etc. The display unit 62 may be provided with a display screen made up of a liquid crystal display panel, etc.

[0022] The alarm output unit 63 outputs various alarms. The alarm output unit 63 outputs a water level alarm when the water level in the tank 10 falls below a predetermined lower limit water level (corresponding to a state where the water level belongs to the water level range WL0 described below; see Figure 3). The alarm output unit 63 outputs a pressure alarm when the pressure detected by the pressure sensor 57 deviates from a predetermined normal pressure range. The alarm output unit 63 outputs a cell alarm when an abnormality is detected in the cell voltage supplied to the electrolytic cell 20. The output of any alarm includes displaying a predetermined alarm on the display unit 62 and transmitting an alarm signal via the signal port 70. The alarm signal is transmitted to an external device via the signal port 70.

[0023] The water level / conductivity detection circuit 64 (hereinafter may be abbreviated as the detection circuit 64) works in cooperation with the electrode unit 12 to detect the water level in the tank 10. Therefore, the detection circuit 64 and the electrode unit 12 form a water level sensor. Furthermore, the detection circuit 64 works in cooperation with the electrode unit 12 to detect the conductivity of the water in the tank 10. Therefore, it can be said that the detection circuit 64 and the electrode unit 12 form a water level sensor with a conductivity detection function (a water level and conductivity detection device).

[0024] The control and display unit 60 can cause the display section 62 to display the cell voltage or the pressure detected by the pressure sensor 57. The control and display unit 60 can also cause the display section 62 to display the water level and conductivity detected by the detection circuit 64.

[0025] Furthermore, when the water level in the tank 10 falls below a predetermined lower limit, the control and display unit 60 may be able to transmit a water replenishment request signal requesting the replenishment of water to an external device via the signal port 70. Furthermore, when a predetermined emergency stop command signal is input to the control and display unit 60 from the external device via the signal port 70, the control and display unit 60 stops the generation of hydrogen (hydrogen gas) by the electrolytic cell 20 and stops the output of hydrogen from the hydrogen generation port 58 by switching the solenoid valve 55 to a closed state.

[0026] If necessary, the water in the tank 10 can be discharged to the outside via the drain pipe 33 and the drain port 72.

[0027] FIG. 2 is a schematic perspective view of the electrode unit 12. FIG. 3 shows a schematic diagram of the positional relationship between the tank 10 and the electrode unit 12 when the tank 10 and the electrode unit 12 are observed from the side. Note that the refill port 11 and the exhaust trap 13 are not shown in FIG. 3. The bottom surface of the tank 10 is referred to by the symbol "10B." The bottom surface 10B corresponds to the bottom surface of the water storage space 10R of the tank 10. When the bottom surface 10B is observed from the vertical direction, the shape of the bottom surface 10B is, for example, a circle or a polygon.

[0028] The electrode unit 12 includes a reference electrode 110, detection electrodes 111 to 113, and an electrode support 120. The upper end of the reference electrode 110 and the upper ends of the detection electrodes 111 to 113 are supported by the electrode support 120.

[0029] The electrode unit 12 is fixed at a predetermined position in the tank 10 by inserting the electrode support 120 into an electrode support receiving opening (not shown) provided on the upper surface of the tank 10 and fixing the electrode support 120 inside the electrode support receiving opening. However, the electrode unit 12 is configured to be detachable from the tank 10. In this embodiment, unless otherwise specified, it is assumed that the electrode unit 12 is fixed at a predetermined position in the tank 10, and that the hydrogen generator 1 is installed so that the bottom surface 10B is parallel to a horizontal plane. Note that, in the electrode support 120, the electrodes 110 to 113 may be arranged concentrically around an axis parallel to the vertical direction (FIG. 2 shows this state schematically). However, in the electrode support 120, the electrodes 110 to 113 may be arranged in a horizontal line. In some reference drawings (e.g., FIG. 3), the electrodes 110 to 113 are shown arranged horizontally.

[0030] The reference electrode 110 and the detection electrodes 111-113 are rod-shaped electrodes extending downward from the electrode support 120 and are inserted into the tank 10. The electrode support 120 supports the upper ends of the reference electrode 110 and the detection electrodes 111-113 while insulating them from each other. A wiring group 130 is provided in the electrode unit 12 to electrically connect the reference electrode 110 and the detection electrodes 111-113 to the detection circuit 64. The wiring group 130 is taken out from the top of the electrode support 120 as a cable.

[0031] The outer shape of the electrode support 120 is a substantially cylindrical shape having a height in the vertical direction, and the lower surface 120B of the electrode support 120 is parallel to the horizontal plane. The reference electrode 110 and the detection electrodes 111 to 113 project downward from the lower surface 120B of the electrode support 120. When comparing the lengths of the reference electrode 110 and the detection electrodes 111 to 113 that project from the lower surface 120B of the electrode support 120, their lengths are different from each other. Among those lengths, the length of the reference electrode 110 is the largest, the length of the detection electrode 111 is the second largest, the length of the detection electrode 112 is the third largest, and the length of the detection electrode 113 is the smallest. Therefore, “d0 < d1 < d2 < d3” holds. Here, d0, d1, d2, and d3 represent the distances from the bottom surface 10B to the lower end of the reference electrode 110, the lower end of the detection electrode 111, the lower end of the detection electrode 112, and the lower end of the detection electrode 113, respectively. Therefore, the lower end of the reference electrode 110 is closer to the bottom surface 10B than the lower ends of the respective detection electrodes.

[0032] The reference electrode 110 and the detection electrodes 111 to 113 are rod-shaped electrodes made of titanium and having the same cross-sectional area with each other. In the present embodiment, the shape of each cross-section (a cross-section parallel to the horizontal plane) of the reference electrode 110 and the detection electrodes 111 to 113 is a circle with a diameter of 1.4 mm (millimeters). Also, in the present embodiment, the lengths of the reference electrode 110, the detection electrodes 111, 112, and 113 that project from the lower surface 120B of the electrode support 120 are 13 cm, 12 cm, 9 cm, and 5 cm, respectively. However, the shape, size, and length of each cross-section of the reference electrode 110 and the detection electrodes 111 to 113 can be variously deformed.

[0033] Referring to FIG. 3, the water level sensor including the electrode unit 12 and the detection circuit 64 detects which of the water level ranges WL0, WL1, WL2, and WL3 the water level in the tank 10 belongs to. This detection is realized by detecting the presence or absence of conduction between the reference electrode 110 and each of the detection electrodes 111 to 113. A state where conduction exists between any two electrodes is referred to as a conduction state, and a state where conduction does not exist between any two electrodes is referred to as a non-conduction state.

[0034] With respect to a target detection electrode, which is any one of the detection electrodes 111 to 113, a conductive state between the reference electrode 110 and the target detection electrode refers to a state in which the value of the electrical resistance between the reference electrode 110 and the target detection electrode is equal to or less than a predetermined reference resistance value, and a non-conductive state between the reference electrode 110 and the target detection electrode refers to a state in which the value of the electrical resistance between the reference electrode 110 and the target detection electrode exceeds the predetermined reference resistance value. The conductivity between the reference electrode 110 and the target detection electrode is achieved by electrically connecting the reference electrode 110 and the target detection electrode through the water in the tank 10.

[0035] The water level in the tank 10 refers to the height of the water surface in the tank 10 as viewed from the bottom surface 10B. The water level range WL3 is the range in which the water surface height is equal to or greater than distance d3. The water level range WL2 is the range in which the water surface height is equal to or greater than distance d2 but less than distance d3. The water level range WL1 is the range in which the water surface height is equal to or greater than distance d1 but less than distance d2. The water level range WL0 is the range in which the water surface height is less than distance d1.

[0036] When the water level in the tank 10 falls within the water level range WL3, a portion of the reference electrode 110 and a portion of the detection electrode 113 are submerged in water, establishing electrical continuity between the electrodes 110 and 113. When the water level in the tank 10 falls within the water level range WL2, the detection electrode 113 does not come into contact with water, establishing electrical continuity between the electrodes 110 and 113, while a portion of the reference electrode 110 and a portion of the detection electrode 112 are submerged in water, establishing electrical continuity between the electrodes 110 and 112. When the water level in the tank 10 falls within the water level range WL1, the detection electrodes 112 and 113 do not come into contact with water, establishing electrical continuity between the electrodes 110 and 112 and between the electrodes 110 and 113, while a portion of the reference electrode 110 and a portion of the detection electrode 111 are submerged in water, establishing electrical continuity between the electrodes 110 and 111. When the water level in the tank 10 falls within the water level range WL0, the detection electrodes 111 to 113 are not in contact with the water, and therefore there is no electrical continuity between the reference electrode 110 and each of the detection electrodes 111 to 113.

[0037] Therefore, the detection circuit 64 can detect the water level in four stages by detecting the presence or absence of continuity between the reference electrode 110 and each of the detection electrodes 111-113. That is, when the electrodes 110 and 113 are conductive, the detection circuit 64 determines that the water level belongs to the water level range WL3. When the electrodes 110 and 113 are not conductive and the electrodes 110 and 112 are conductive, the detection circuit 64 determines that the water level belongs to the water level range WL2. When the electrodes 110 and 112 are not conductive and the electrodes 110 and 111 are conductive, the detection circuit 64 determines that the water level belongs to the water level range WL1. When the electrodes 110 and 111 are not conductive, the detection circuit 64 determines that the water level belongs to the water level range WL0. In this way, the water level sensor can detect whether the water level is higher than the height of the lower end of each detection electrode.

[0038] Many hydrogen generators that generate hydrogen using the electrolysis of water detect the water level to ensure proper water replenishment. However, if the conductivity of the water supplied to the electrolytic cell (electrolytic cell 20 in the hydrogen generator 1) is high, deterioration of the electrolytic cell will be accelerated, and depending on the conductivity, the electrolytic cell may fail after a short period of operation. For this reason, it is often necessary to detect the conductivity of the water.

[0039] To detect conductivity, a reference method has been considered in which a conductivity meter is installed separately from the water level sensor, as shown in Figure 15. In the reference method of Figure 15, the conductivity meter is installed inside the tank separately from the electrode unit that forms the water level sensor. However, this reference method requires space to install the conductivity meter inside the tank, and the installation of the conductivity meter increases costs.

[0040] Taking this into consideration, in this embodiment, both water level detection and conductivity detection are achieved using a water level sensor configuration. The following first, second, and third experiments were conducted to examine a configuration for effectively detecting the water level and conductivity. In this embodiment, the reference electrode 110 and the detection electrode 111 are actually partially covered with an insulator. However, in the first experiment, a comparison configuration was adopted in which the reference electrode 110 and the detection electrode 111 protruding from the electrode support 120 are not entirely covered with an insulator.

[0041] In each experiment, several types of water with known conductivities were prepared, and the conductivity of the water between the reference electrode 110 and the detection electrode 111 was measured with an experimental conductivity meter while a portion of each of the reference electrode 110 and the detection electrode 111 was in contact with the water. The experimental conductivity meter was a conductivity meter prepared specifically for the experiment.

[0042] The results of the first experiment are shown in Figure 4. In the graph of Figure 4, the horizontal axis corresponds to the conductivity of the water in the tank 10, and the conductivity on the horizontal axis can be interpreted as representing the true conductivity of the water in the tank 10 (the same applies to the graphs of Figures 6(a) to 6(c) and Figures 8(a) to 8(c) described below). In the first experiment, an experimental conductivity meter was connected to the reference electrode 110 and the detection electrode 111, which were configured for comparison, and the output value of the experimental conductivity meter was read. The output value of the experimental conductivity meter is proportional to the magnitude of the current flowing between the electrodes 110 and 111 when a predetermined AC voltage is applied between them. For convenience, the output value of the experimental conductivity meter is referred to as the reference detected conductivity. In each experiment, the experimental conductivity meter was insufficiently calibrated, and therefore the reference detected conductivity does not represent the true conductivity. However, the linearity of the experimental conductivity meter is sufficiently high. That is, when the conductivity of water is multiplied by k in each experiment, the reference detected conductivity is also multiplied by k with sufficiently high accuracy (k is any positive value).

[0043] Here, the distance from the bottom of the reference electrode 110 to the water surface in the tank 10 is defined as D W In the graph of FIG. 4, the plots represented by black circles are the distances D WThe graph in Figure 4 shows the relationship between the true conductivity and the reference detected conductivity for the comparison configuration when the distance D is 10 cm. W The graph in Figure 4 shows the relationship between the true conductivity and the reference detected conductivity for the comparison configuration when the distance D is 6 cm. W This shows the relationship between the true conductivity and the reference detected conductivity for the comparison configuration when the distance is 3 cm.

[0044] In the comparison configuration, linearity is obtained at each water level, but it can be seen that the reference detected conductivity changes depending on the water level. This is because the electrode area in contact with the water changes as the water level changes. The detected conductivity by a conductivity meter depends on a constant (called the cell constant) determined by the electrode area in contact with the water and the distance between the electrodes, so if the electrode area changes depending on the water level, the detected conductivity (here, the reference detected conductivity) also changes. For example, when the comparison configuration is adopted, the distance D W When the distance D is 3cm, W If the distance is increased to 6 cm, the contact area between the reference electrode 110 and the water and the contact area between the detection electrode 111 and the water will each be approximately doubled, and as a result, the obtained reference detection conductivity will also be approximately doubled.

[0045] Therefore, in the second and third experiments, a covering configuration was adopted in which the portions of the reference electrode 110 and the detection electrode 111 protruding from the electrode support 120 were covered with an insulator.

[0046] The structures of the reference electrode 110 and the detection electrode 111 related to the covering configuration will be described with reference to Fig. 5. In the hydrogen generator 1 according to this embodiment, actually, each of the detection electrodes 112 and 113 can also be partially covered with an insulator, but Fig. 5 shows the covering configuration related only to the reference electrode 110 and the detection electrode 111.

[0047] The electrode portion of the reference electrode 110 protruding from the electrode support 120 (the titanium electrode portion) is composed of a covered portion 110a and an exposed portion 110b. The exposed portion 110b is the portion of the reference electrode 110 that includes the lower end of the reference electrode 110. The covered portion 110a is the portion of the reference electrode 110 that extends from the lower surface 120B of the electrode support 120 to the exposed portion 110b. The covered portion 110a is covered with an insulator. Therefore, the electrode portion of the covered portion 110a does not come into contact with the water in the tank 10 regardless of the water level, and does not actually function as an electrode. In this covering configuration, it is preferable that there is no gap between the lower surface 120B of the electrode support 120 and the covered portion 110a, and that the entire electrode portion of the reference electrode 110 from the lower surface 120B of the electrode support 120 to the exposed portion 110b is covered with an insulator. On the other hand, the exposed portion 110b is not covered with an insulator, and the electrode portion in the exposed portion 110b is exposed to the water containing space 10R. Therefore, when the water level is equal to or greater than the distance d0, the electrode portion in the exposed portion 110b comes into contact with the water in the tank 10.

[0048] The electrode portion of the detection electrode 111 protruding from the electrode support 120 (the electrode portion made of titanium) is composed of a covered portion 111a and an exposed portion 111b. The exposed portion 111b is the portion of the electrode portion of the detection electrode 111 that includes the lower end of the detection electrode 111. The covered portion 111a is the portion of the electrode portion of the detection electrode 111 that extends from the lower surface 120B of the electrode support 120 to the exposed portion 111b. The covered portion 111a is covered with an insulator. Therefore, the electrode portion of the covered portion 111a does not come into contact with the water in the tank 10 regardless of the water level, and does not substantially function as an electrode. In the covering configuration, it is preferable that there is no gap between the lower surface 120B of the electrode support 120 and the covered portion 111a, and that the entire electrode portion of the detection electrode 111 from the lower surface 120B of the electrode support 120 to the exposed portion 111b be covered with an insulator. On the other hand, the exposed portion 111b is not covered with an insulator, and the electrode portion in the exposed portion 111b is exposed to the water containing space 10R. Therefore, when the water level is equal to or greater than the distance d1, the electrode portion in the exposed portion 111b comes into contact with the water in the tank 10.

[0049] The length of the exposed portion 110b of the reference electrode 110 in the vertical direction is represented by the symbol "Lb 110 The length of the exposed portion 111b of the detection electrode 111 in the vertical direction is referred to as "Lb 111 In the vertical direction, the length Lb of the exposed portion 110b is 110 is sufficiently shorter than the length of the covered portion 110a, and the length Lb of the exposed portion 111b 111 is sufficiently shorter than the length of the covering portion 111a. 110 and length Lb 111 are basically the same as each other, but modifications that make them different from each other are possible.

[0050] The insulators in the coverings 110a and 111a have a sufficiently high electrical resistivity so as not to affect the detection of the water level and conductivity. For example, heat-shrinkable tubing made of silicone rubber or fluorine-based resin can be used as the insulator. In the second and third experiments, heat-shrinkable tubing was used as the insulator. However, the insulators in the coverings 110a and 111a may also have the form of an insulating tube. Alternatively, for example, the covering 110a may be formed by coating a portion of the reference electrode 110 with an insulator (the same applies to the detection electrode 111).

[0051] In the second experiment, the length Lb 110 and Lb 111 The length Lb was set to about 2 mm (millimeters). The results of the second experiment are shown in Figures 6(a) to 6(c). In the second experiment, the coating structure (however, the length Lb 110 and Lb 111 An experimental conductivity meter was connected to the reference electrode 110 and the detection electrode 111, which had a distance D of approximately 2 mm, and the output value of the experimental conductivity meter was read as the reference detected conductivity. W The graph in Fig. 6(b) shows the relationship between the true conductivity and the reference detected conductivity in the second experiment when the distance D is 10 cm. W The graph in Fig. 6(c) shows the relationship between the true conductivity and the reference detected conductivity in the second experiment when the distance D is 6 cm.W This shows the relationship between the true conductivity and the reference detected conductivity in the second experiment when the distance is 3 cm.

[0052] If the plots shown in Figures 6(a) to 6(c) were plotted on a single graph, the plots represented by black circles, open triangles, and open squares would overlap and be indistinguishable, so they are shown on separate graphs. This shows that the reference detected conductivity in the second experiment is completely or almost independent of the water level. Although it is not clear from Figures 6(a) to (c), in the second experiment, the error in the reference detected conductivity due to the water level was about 1%. In other words, when water of a certain conductivity was used in the second experiment, the error in the distance D W First reference detection conductivity when distance D is 10 cm W The second reference detection conductivity and distance D when W The third reference detection conductivity is measured when the distance is 3 cm, and the absolute value of the difference between the obtained conductivities is calculated. This absolute value is approximately 1% or less of the first, second, or third reference detection conductivity.

[0053] When the covering structure is adopted, the area of ​​the electrode part of the reference electrode 110 that is in contact with water, i.e., the surface area of ​​the exposed part 110b, is constant regardless of the water level (however, when the height of the water surface is (d0 + Lb 110 When the covering structure is adopted, the area of ​​the electrode part of the detection electrode 111 that is in contact with water, that is, the surface area of ​​the exposed part 111b, is constant regardless of the water level (however, when the height of the water surface is (d1 + Lb 111 Therefore, it is assumed that the exposed portions 110b and 111b are entirely in contact with water (i.e., the water surface is at a height of (d1+Lb 111 ) or higher), the reference detected conductivity is independent of the water level.

[0054] Furthermore, the coating configuration of the second experiment provides good linearity in the reference detected conductivity over a wide conductivity range, i.e., the true conductivity and the reference detected conductivity are proportional to each other over a wide conductivity range.

[0055] In the third experiment, the length Lb 110 and Lb 111 was set to substantially 0 mm (millimeters). In this case, the exposed portion 110b is made up of only the lower surface of the reference electrode 110 as shown in Fig. 7(a), and the exposed portion 111b is made up of only the lower surface of the detection electrode 111 as shown in Fig. 7(b).

[0056] The results of the third experiment are shown in Figures 8(a) to 8(c). In the third experiment, the coating structure (however, the length Lb 110 and Lb 111 An experimental conductivity meter was connected to the reference electrode 110 and the detection electrode 111, for which the distance D was substantially 0 mm, and the output value of the experimental conductivity meter was read as the reference detected conductivity. In the graph of FIG. 8(a), the plots represented by black circles indicate the distance D W The graph in Fig. 8(b) shows the relationship between the true conductivity and the reference detected conductivity in the third experiment when the distance D is 10 cm. W The graph in Fig. 8(c) shows the relationship between the true conductivity and the reference detected conductivity in the third experiment when the distance D is 6 cm. W This shows the relationship between the true conductivity and the reference detected conductivity in the third experiment when the distance is 3 cm.

[0057] 8(a) to 8(c) on a single graph, the plots represented by black circles, open triangles, and open squares would overlap and be indistinguishable, so they are shown on separate graphs. This indicates that the reference detected conductivity in the third experiment is completely or almost completely independent of the water level.

[0058] However, the linearity of the reference detected conductivity is lost in the coating configuration of Experiment 3. In particular, in the coating configuration of Experiment 3, the proportional relationship between the true conductivity and the reference detected conductivity is lost in the relatively high conductivity range.

[0059] Therefore, the length Lb 110 and Lb 111It is desirable to make the length Lb greater than zero, that is, to make the exposed portions 110b and 111b have a length in the vertical direction. 110 and Lb 111 If is too large, the change in cell constant due to the water level becomes too large to be ignored. 110 and Lb 111 It is desirable to make the length Lb greater than 0 and less than a predetermined length. 110 and Lb 111 It is desirable to set the length within the range of 2 mm to 3 mm, but the length Lb 110 and Lb 111 The length Lb may be less than 2 mm (for example, 1 mm) or may be slightly more than 3 mm. For example, the predetermined length may be 5 mm or 10 mm. 110 and Lb 111 It is considered that there will be no problem in the accuracy of detecting the conductivity if the length Lb is set to be greater than 0 and equal to or less than 10 mm. 110 and the ratio of the length Lb to the total length of the covered portion 111a and the exposed portion 111b. 111 The ratio may be set to be greater than 0 and equal to or less than a predetermined value (for example, equal to or less than 5% or equal to or less than 3%).

[0060] In order to prevent erroneous detection of the water level due to condensation, a reference configuration has been considered in which only a small portion of the upper side of the reference electrode and a small portion of the upper side of the detection electrode are covered with an insulator. However, even if an attempt is made to measure the conductivity with this reference configuration, it is difficult to obtain the desired linearity. At least in the vertical direction, the length Lb of the exposed portion 110b of the reference electrode 110 is 110 is shorter than the length of the covering portion 110a, and the length Lb of the exposed portion 111b of the detection electrode 111 is 111 By making the length shorter than the length of the covering portion 111a, it is possible to ensure a certain degree of linearity (linearity superior to that of the above-mentioned reference configuration can be obtained).

[0061] Here, the length Lb 110 and Lb111 Figure 9 shows the behavior of the length Lb 110 and Lb 111 9 shows a schematic diagram of the current line distribution when a voltage is applied between the electrodes 110 and 111 when the electrodes 110 and 111 have a suitable size (e.g., 2 mm). In the state of FIG. 9, a part of the side surface of the exposed portion 110b and a part of the side surface of the exposed portion 111b face each other. Therefore, when a voltage is applied between the electrodes 110 and 111, the path that connects the exposed portions 110b and 111b over the shortest distance is dominant as the current path. In reality, there are also curved current paths, but in the state of FIG. 9, the current line distribution between the electrodes 110 and 111 is kept or easily kept constant regardless of the conductivity of water. Therefore, in the state of FIG. 9, high linearity can be obtained in conductivity measurement. Note that technical documents regarding the current line distribution in conductivity measurement include the non-patent document "General Explanation of Conductometric Titration Method," [online], [searched September 9, 2021], and the Internet.<URL:https: / / www.jstage.jst.go.jp / article / revpolarography1955 / 10 / 3 / 10_3_102 / _pdf> " are cited as examples.

[0062] In Figure 10, the length Lb 110 and Lb 111 10 shows a schematic diagram of a current line distribution when a voltage is applied between electrodes 110 and 111 when σ is zero. In the state of FIG. 10, exposed portion 110b and exposed portion 111b do not have electrode portions facing each other. Therefore, when a voltage is applied between electrodes 110 and 111 in the state of FIG. 10, a current flows along a curved path between exposed portion 110b, which corresponds to the lower surface of reference electrode 110, and exposed portion 111b, which corresponds to the lower surface of detection electrode 111. In other words, in the state of FIG. 10, a linear current distribution that satisfies Ohm's law is not formed, and the current line distribution varies depending on the conductivity of water, which is thought to make it easy for the linearity of conductivity measurement to be lost.

[0063] In this embodiment, unless otherwise specified, the above-described covering configuration is adopted for the reference electrode 110 and the detection electrode 111, and the length Lb 110 and Lb 111is set to a length within the range of 2 mm to 3 mm.

[0064] The following Examples EX1_1 to EX1_6 belong to the first embodiment. In Examples EX1_1 to EX1_6, several specific configuration examples, operation examples, application techniques, modified techniques, etc. related to the hydrogen generator 1 (particularly the water level sensor) will be described. The matters described above in this embodiment are applied to each of the following Examples unless otherwise specified and unless there is a contradiction. If there are any matters in each Example that contradict the matters described above, the description in each Example may take precedence. Furthermore, unless there is a contradiction, the matters described in any of the following Examples can also be applied to any of the other Examples (i.e., any two or more of the multiple Examples can also be combined).

[0065] [Example EX1_1] An example EX1_1 will be described. Fig. 11 shows the internal configuration of a detection circuit 64 according to the example EX1_1. However, Fig. 11 shows only the configuration related to the electrodes 110 and 111 of the detection circuit 64 (the same applies to Fig. 13 described later).

[0066] In the configuration of FIG. 11, the detection circuit 64 includes an AC voltage source 210, an IV conversion unit 220, a water level determination unit 230, and a conductivity conversion unit 240.

[0067] The AC voltage source 210 supplies an AC voltage V having a predetermined frequency. AC Generates and outputs AC voltage V AC is supplied between the reference electrode 110 and the detection electrode 111. AC The frequency of the AC voltage V is set to a value ranging from several tens of Hz to several megahertz. AC The amplitude of the AC voltage V is fixed at a predetermined value. AC The waveform of is a sine wave, but may be other than a sine wave. AC The current flowing between the electrodes 110 and 111 when the voltage is applied is the current I S It is called.

[0068] The IV conversion unit 220 converts the current I S A shunt resistor is inserted in series on the wiring through which the current I flows. S The amplitude of the voltage is converted into a voltage. The voltage obtained by this conversion is the detection voltage value V S The current I S As the amplitude of increases, the detected voltage value V S increases. Here, the current I S and the detected voltage value V S The detection voltage value V S is generated.

[0069] The water level determination unit 230 detects the voltage value V S The detected voltage value V is compared with a predetermined threshold value TH1, and a water level determination signal WD1 is generated and output in accordance with the comparison result. S When the detected voltage value V is equal to or greater than the threshold value TH1, a water level determination signal WD1 having a value of "1" is generated. S is less than the threshold value TH1, a water level determination signal WD1 having a value of "0" is generated. A water level determination signal WD1 of "1" indicates that there is electrical continuity between the electrodes 110 and 111, and therefore indicates that the water level in the tank 10 is higher than the lower end of the detection electrode 111 (i.e., indicates that the water level belongs to one of the water level ranges WL1 to WL3). A water level determination signal WD1 of "0" indicates that there is no electrical continuity between the electrodes 110 and 111, and therefore indicates that the water level in the tank 10 is lower than the lower end of the detection electrode 111 (i.e., indicates that the water level belongs to the water level range WL0).

[0070] Although not specifically shown, the detection circuit 64 detects the AC voltage V AC When the AC voltage V is applied between the electrodes 110 and 112, the detection circuit 64 generates a detection voltage value corresponding to the amplitude of the current flowing between the electrodes 110 and 112, and generates a water level determination signal WD2 based on the detection voltage value. The water level determination signal WD2 indicates whether the water level in the tank 10 is higher than the lower end of the detection electrode 112 (in other words, whether the electrodes 110 and 112 are in a conductive state or a non-conductive state). Furthermore, the detection circuit 64 detects the AC voltage V ACWhen a voltage is applied between the electrodes 110 and 113, a detection voltage value corresponding to the amplitude of the current flowing between the electrodes 110 and 113 is generated, and a water level determination signal WD3 is generated based on the detection voltage value. The water level determination signal WD3 indicates whether the water level in the tank 10 is higher than the lower end of the detection electrode 113 (in other words, whether the electrodes 110 and 113 are in a conductive state or a non-conductive state). The water level determination signals WD2 and WD3 are generated in the same manner as the water level determination signal WD1. The water level determination signals WD1 to WD3 identify which of the water level ranges WL0 to WL3 the water level belongs to.

[0071] The conductivity conversion unit 240 converts the detected voltage value V S is converted into conductivity to detect conductivity EC DET Detected conductivity EC DET represents the conductivity of the water in the tank 10 detected by the detection circuit 64. However, unless the exposed portions 110b and 111b are immersed in water, the conductivity of the water in the tank 10 cannot be detected correctly. Therefore, the conductivity conversion unit 240 converts the detected conductivity EC DET That is, the detection circuit 64 detects the conductivity of the water in the tank 10 when the water level in the tank 10 is higher than the lower end of the detection electrode 111, and converts the detection result into a detected conductivity EC DET Obtain as.

[0072] The conversion algorithm can be created in advance by a calibration process using water with a known conductivity. Figure 12 shows a flowchart of the calibration process. In the calibration process, first, in step S11, a known conductivity EC P A standard solution having a conductivity (e.g., 50 μS / cm) and a calibration container are prepared, and the required amount of the standard solution is poured into the calibration container to achieve the calibration state. In the calibration state, the reference electrode 110 and the detection electrode 111 are immersed in the standard solution in the calibration container so that the exposed portions 110b and 111b come into contact with the standard solution. The tank 10 can be used as the calibration container, but any other container can also be used.

[0073] In the subsequent step S12, an AC voltage V is applied between the electrodes 110 and 111 in the calibration state. AC By applying the voltage V S In the following step S13, the detected voltage value V obtained in step S12 is S and electrical conductivity EC P Based on this, the detected voltage value V S and the detected conductivity EC DET A conversion algorithm is created that defines the relationship between the detected voltage value V S If you enter DET Conductivity EC as P You will be able to obtain the following.

[0074] The conversion algorithm is based on the detected voltage value V S and the detected conductivity EC DET The conversion algorithm may be configured by a mathematical formula that defines the relationship between the conductivity of the water in the tank 10 and the detected conductivity EC. A program (software) including the conversion algorithm may be created during the design or manufacturing stage of the hydrogen generator 1. After the calibration process, the program is executed by an arithmetic processing circuit (not shown) that can be built into the detection circuit 64 to calculate the conductivity of the water in the tank 10, and the calculation result is used as the detected conductivity EC. DET can be obtained as:

[0075] When the water level is higher than the lower end of the detection electrode 111, in the comparative configuration in which the electrodes 110 and 111 are not covered with any insulator, the detection voltage value V S The detected voltage value V S It is also possible to determine the water level while taking into consideration the change in the detection voltage V S The change in the detection voltage V depending on the water level can act as an error factor and lead to erroneous detection of the water level. SSince the change in conductivity is suppressed, erroneous detection of the water level is suppressed. In addition, the linearity provided by the adoption of the above-mentioned coating configuration makes it possible to accurately detect the conductivity regardless of the water level. In other words, the water level sensor can accurately detect the water level and conductivity (in other words, the structure of the water level sensor can be used to accurately detect not only the water level but also the conductivity). Furthermore, compared to the configuration of Figure 15, costs and installation space can be reduced.

[0076] [Example EX1_2] An example EX1_2 will be described. When the circuit constants of the IV conversion unit suitable for water level detection and the circuit constants of the IV conversion unit suitable for conductivity detection are significantly different, the detection circuit 64 may be provided with an IV conversion unit for water level detection and an IV conversion unit for conductivity detection separately. That is, the detection circuit 64 may be configured as shown in Fig. 13. The detection circuit 64a is the detection circuit 64 according to the example EX1_2.

[0077] The detection circuit 64a in Fig. 13 is based on the detection circuit 64 in Fig. 11, in that the IV conversion unit 220 is replaced with an IV conversion unit 221 for water level detection and an IV conversion unit 222 for conductivity detection, and a changeover switch 225 is added. Except for this replacement and addition, the detection circuit 64a in Fig. 13 has the same configuration as the detection circuit 64 in Fig. 11.

[0078] In the detection circuit 64a, the first detection state and the second detection state are alternately realized using the changeover switch 225. In both the first and second detection states, the AC voltage V AC is supplied between the reference electrode 110 and the detection electrode 111. However, in the first detection state, the current I S flows through the IV conversion unit 221, and in the second detection state, the current I S flows through the IV conversion unit 222.

[0079] In the first detection state, the IV conversion unit 221 converts the current I S The first shunt resistor is inserted in series on the wiring through which the current I flows. S The amplitude of the voltage is converted to the detected voltage value VS In the second detection state, the IV conversion unit 222 generates and outputs the current I S A second shunt resistor is inserted in series on the wiring through which the current I flows. S The amplitude of the voltage is converted to the detected voltage value V S Generate and output.

[0080] In the first detection state, the water level determination unit 230 detects the detected voltage value V S The water level determination signal WD1 is generated based on the detected voltage value V S In the second detection state, the conductivity conversion unit 240 generates the water level determination signal WD1 based on the detected voltage value V from the IV conversion unit 222. S Based on the detected conductivity EC DET The detected voltage value V S Detected conductivity based on EC DET The method of deriving is as described in Example EX1_1.

[0081] [Example EX1_3] Example EX1_3 will be described. The covering configuration may be applied to each of the detection electrodes other than the detection electrode 111. That is, each of the detection electrodes 112 and 113 may be partially covered with an insulator. In this case, as shown in Fig. 14, the electrode portion of the detection electrode 112 protruding from the electrode support 120 (the electrode portion made of titanium) is composed of a covered portion 112a and an exposed portion 112b, and the electrode portion of the detection electrode 113 protruding from the electrode support 120 (the electrode portion made of titanium) is composed of a covered portion 113a and an exposed portion 113b.

[0082] The exposed portion 112b is the electrode portion of the detection electrode 112 that includes the lower end of the detection electrode 112. The covered portion 112a is the electrode portion of the detection electrode 112 that extends from the lower surface 120B of the electrode support 120 to the exposed portion 112b. The covered portion 112a is covered with an insulator. It is preferable that there is no gap between the lower surface 120B of the electrode support 120 and the covered portion 112a, and that the entire electrode portion of the detection electrode 112 from the lower surface 120B of the electrode support 120 to the exposed portion 112b is covered with an insulator. On the other hand, the exposed portion 112b is not covered with an insulator, and the electrode portion at the exposed portion 112b is exposed to the water storage space 10R.

[0083] The exposed portion 113b is the electrode portion of the detection electrode 113 that includes the lower end of the detection electrode 113. The covered portion 113a is the electrode portion of the detection electrode 113 that extends from the lower surface 120B of the electrode support 120 to the exposed portion 113b. The covered portion 113a is covered with an insulator. It is preferable that there is no gap between the lower surface 120B of the electrode support 120 and the covered portion 113a, and that the entire electrode portion of the detection electrode 113 from the lower surface 120B of the electrode support 120 to the exposed portion 113b is covered with an insulator. On the other hand, the exposed portion 113b is not covered with an insulator, and the electrode portion of the exposed portion 113b is exposed to the water storage space 10R.

[0084] By covering a portion of each electrode with an insulator as described above, not only the detected voltage value based on the current between electrodes 110 and 111, but also the detected voltage value based on the current between electrodes 110 and 112 and the detected voltage value based on the current between electrodes 110 and 113 become independent of the water level. Therefore, error factors are reduced not only in water level detection using detection electrode 111 but also in water level detection using detection electrodes 112 and 113, and as a result, erroneous detection of the water level is suppressed.

[0085] Furthermore, if it is considered that portions of the detection electrodes 112 and 113 are covered with insulating material not from the viewpoint of ensuring linearity in conductivity detection but from the viewpoint of preventing erroneous detection of water level, the length of each of the exposed portions 112b and 113b in the vertical direction may be longer than the length of each of the exposed portions 110b and 110b (however, it is also possible to set all of these lengths to be the same).

[0086] [Example EX1_4] Example EX1_4 will be described. The hydrogen generator 1 according to this embodiment is provided with three detection electrodes 111 to 113 as a plurality of detection electrodes.

[0087] Of the multiple detection electrodes, the detection electrode used to detect conductivity is referred to as the target detection electrode. In this case, in this embodiment, of the multiple detection electrodes, the detection electrode (111) that is the shortest distance from the bottom surface 10B of the tank 10 is set as the target detection electrode. This allows conductivity to be detected even when the water level is lower than when another detection electrode (112 or 113) is set as the target detection electrode. However, a modification in which the detection electrode 112 or 113 is used as the target detection electrode is also possible.

[0088] [Example EX1_5] Example EX1_5 will be described. In Example EX1_5, the calibration process (see FIG. 12) in the hydrogen generator 1 will be supplementarily described in comparison with the configuration of FIG.

[0089] In order to calibrate the conductivity meter in the configuration of FIG. 15, the following first to third steps are required. In the first step, a standard solution having a known conductivity is poured into a tank (for example, a tank having a volume of 2 liters). In the subsequent second step, parameters for calibration are calculated based on the conductivity meter measurement value and the known conductivity. This completes the calibration of the conductivity meter. Then, in the third step, the tank is washed with deionized water of sufficiently high purity. The cleaning in the third step requires pure water equal to or greater than the volume of the tank (for example, 2 liters or more). Thus, in order to calibrate the conductivity meter in the configuration of FIG. 15, a large amount of standard solution and deionized water is required. Furthermore, in the configuration of FIG. 15, it is difficult (a large burden) for the customer (the user of the hydrogen generator) to calibrate the conductivity meter, and therefore, it basically needs to be performed by the manufacturer.

[0090] In contrast, in the hydrogen generator 1 according to the present embodiment, the water level sensor includes a conductivity meter (in other words, the water level sensor and the conductivity meter are integrated), so a calibration container having a smaller volume than the tank 10 can be used in the calibration process (see FIG. 12). For example, while the volume of the tank 10 (i.e., the volume of the water storage space 10R) is 2 liters, a cylinder 600 having a volume of about 100 milliliters can be used as the calibration container. This makes it possible to significantly reduce the amount of standard solution and pure water required for calibration. Furthermore, calibration can be easily performed on the customer side.

[0091] The operation modes of the hydrogen generator 1 are a normal mode and a calibration mode. In the normal mode, the water level and conductivity in the tank 10 are detected by the configuration and operation shown in Example EX1_1 or EX1_2. For example, the operation mode of the hydrogen generator 1 is set to the calibration mode by inputting a predetermined calibration execution instruction operation to an operation unit (not shown) provided in the hydrogen generator 1, or by inputting a predetermined calibration execution instruction signal from an external device to the control display unit 60 via the signal port 70. In the calibration mode, the calibration process shown in FIG. 12 is executed. At this time, the conductivity EC of the standard solution used in the calibration process is Pis given to the control and display unit 60. The conversion algorithm itself may be created at the design or manufacturing stage of the hydrogen generator 1, and then, when a calibration process is performed on the customer side, only the parameters of the conversion algorithm are adjusted.

[0092] [Example EX1_6] Example EX1_6 will be described. In Example EX1_6, supplementary matters, applied techniques, modified techniques, etc. to the above-mentioned configuration will be described.

[0093] The above-mentioned Patent Document 1 (JP 2004-510151 A) discloses a method for estimating the water level in a tank based on the electrical resistance between a water level electrode and a reference electrode and the electrical resistance between a reference electrode and a reference electrode (see claim 1 of Patent Document 1). Let us compare Patent Document 1 with the configuration of this embodiment. First, the water level estimation method of Patent Document 1 differs from the method of this embodiment, which detects the water level based on the presence or absence of conduction between the reference electrode and the detection electrode. Furthermore, in Patent Document 1, the reference electrode (corresponding to electrode 143 in Figure 2 of Patent Document 1) is not covered with an insulator. Therefore, even if an attempt is made to measure conductivity using the water level sensor of Patent Document 1 as in this embodiment, accurate conductivity measurement is difficult due to the lack of linearity. Furthermore, in the configuration of Patent Document 1, the upper region of the water level electrode (corresponding to upper region 1412 in Figure 2 of Patent Document 1) is exposed, which raises concerns about erroneous water level detection due to the formation of water droplets, such as condensation, on the exposed region.

[0094] Although the electrodes 110 to 113 are described above as being made of titanium, the material of the electrodes 110 to 113 is not limited to titanium. The electrodes 110 to 113 may be made of any material that is a good conductor and has a conductivity that is sufficiently higher than that of the liquid (water) to be contained in the tank 10. The material of the electrodes 110 to 113 may be a metal other than titanium, or may be a conductive resin. However, the electrodes 110 to 113 should be made of a material that does not dissolve in water.

[0095] In this embodiment, three detection electrodes are provided in the electrode unit 12, but the number n of detection electrodes provided in the electrode unit 12 may be any number as long as it is equal to or greater than 1. For example, the detection electrodes 112 and 113 may be omitted from the electrode unit 12 so that "n=1".

[0096] Although the above describes an example in which the water level sensor according to the present invention is applied to the hydrogen generator 1, the water level sensor according to the present invention can be applied to any application requiring detection of the level and conductivity of a liquid in a tank. For example, the water level sensor according to the present invention may be applied to a functional water production device that produces various types of functional water. Furthermore, the liquid in the tank may be something other than water.

[0097] <<Second embodiment>> A second embodiment of the present invention will be described. The second embodiment is an embodiment based on the first embodiment, and with regard to matters not described in the second embodiment, unless otherwise specified and unless there is a contradiction, matters described in the first embodiment may be applied to the second embodiment. In the second embodiment, a temperature compensation technique for conductivity that can be applied to the hydrogen generator 1 according to the first embodiment will be described.

[0098] First, the significance of temperature compensation will be explained. The results of detecting the conductivity of the water in the tank 10 include a detected conductivity without temperature compensation and a detected conductivity with temperature compensation.

[0099] The detected conductivity without temperature compensation refers to the detection result of the actual conductivity of the water in the tank 10. The actual conductivity of the water in the tank 10 increases as the liquid temperature rises due to an increase in the speed of ion migration, etc., and conversely decreases as the liquid temperature drops. In other words, the actual conductivity of the water in the tank 10 depends on the liquid temperature. Here, the liquid temperature refers to the temperature of the water in the tank 10.

[0100] On the other hand, the detected conductivity with temperature compensation refers to the detection result of the conductivity of the water in the tank 10 when it is assumed that the liquid temperature is at a predetermined reference temperature. Temperature compensation corresponds to converting the actual conductivity of the water in the tank 10 to the conductivity at the reference temperature (the conductivity of the water in the tank 10 when it is assumed that the liquid temperature is at the reference temperature) according to the liquid temperature. Since 25°C is generally used as the reference temperature, the reference temperature in this embodiment is also considered to be 25°C. However, the reference temperature may be other than 25°C.

[0101] For example, even if the sample of water in the tank 10 is the same, if the liquid temperature is 50°C, the above-mentioned detected voltage value V S (See Figure 11, etc.) has a relatively large value corresponding to the conductivity of water at 50°C, and if the liquid temperature is 10°C, the detected voltage value V S has a relatively small value corresponding to the conductivity of water at 10°C. Therefore, the detected conductivity EC DET (See FIG. 11, etc.) is the detected conductivity without temperature compensation, even if the water sample in the tank 10 is the same, the detected conductivity EC DET also increases or decreases.

[0102] In the first embodiment, the detected conductivity EC DET may be a detected conductivity without temperature compensation. In this case, the conductivity conversion unit 240 converts the detected voltage value V into a value using a predetermined conversion algorithm that is independent of the liquid temperature. S is converted to conductivity, the detected conductivity EC without temperature compensation DET The detected conductivity without temperature compensation, EC DET represents the actual conductivity of the water in the tank 10 and is dependent on the liquid temperature. The control and display unit 60 measures the detected conductivity EC without temperature compensation. DET may be displayed on the display unit 62 or transmitted to an external device (not shown) connected to the signal port 70.

[0103] In the first embodiment, the detected conductivity EC DET may be a temperature-compensated detected conductivity. In this case, the conductivity conversion unit 240 converts the detected voltage value V into a temperature-compensated value using a predetermined conversion algorithm that depends on the liquid temperature. Sis converted to conductivity, the temperature-compensated detected conductivity EC DET The temperature-compensated detected conductivity EC DET represents the conductivity of the water in the tank 10 when the liquid temperature is assumed to be at a reference temperature. The control and display unit 60 detects the temperature-compensated detected conductivity EC DET may be displayed on the display unit 62 or transmitted to an external device (not shown) connected to the signal port 70. The method of performing temperature compensation is known, and a known temperature compensation method may be incorporated into the above conversion algorithm. Linear or non-linear temperature compensation may be employed.

[0104] In the second embodiment, the detected conductivity with temperature compensation is hereinafter referred to as the detected conductivity EC DET In order to perform temperature compensation, it is necessary to measure the liquid temperature. For this reason, a temperature sensor 80 shown in FIG. 16 is added to the hydrogen generator 1.

[0105] The temperature sensor 80 has a temperature measuring element 81 installed at the measurement target position, and measures the temperature at the measurement target position using the temperature measuring element 81. The temperature measured by the temperature sensor 80 is referred to as the measured temperature T DET The measured temperature T DET represents the measured temperature at the measurement target position. Here, the temperature measuring element 81 is configured by a platinum resistance thermometer, and the resistance value of the temperature measuring element 81 changes depending on the temperature at the measurement target position. The temperature sensor 80 outputs a signal according to the resistance value of the temperature measuring element 81 as the measured temperature T DET The temperature at the measurement position is output to the conductivity conversion unit 240 as a signal representing the measured temperature T DET The type of the temperature measuring element 81 and the configuration of the temperature sensor 80 are arbitrary as long as the temperature measuring element 81 and the temperature sensor 80 can be obtained.

[0106] 11 or 13 can be used as the conductivity converter 240 according to the second embodiment. S and the measured temperature T DET Temperature-compensated conductivity detection based on EC DET is derived.

[0107] A simple method for measuring the liquid temperature is to insert a metal temperature sensor, such as a sheathed thermocouple, into the water in the tank 10. However, inserting a metal temperature sensor into the water in the tank 10 raises concerns about metal ions leaking out due to component deterioration over the long term. If metal ions leak into the water in the tank 10, the (pure) water in the tank 10 will deteriorate, which will shorten the lifespan of the electrolysis cell 10. Note that while the leakage of metal ions can be prevented by using a plastic temperature sensor, the introduction of a plastic temperature sensor will result in a significant increase in costs.

[0108] Taking these factors into consideration, in this embodiment, a position outside the tank 10 is set as the measurement position, and temperature compensation is performed by using the temperature of the measurement position outside the tank 10 instead of the liquid temperature. For this reason, it is preferable to set the measurement position at a position whose temperature changes in the same way as the liquid temperature and whose deviation from the liquid temperature is constant or as small as possible. Specifically, it is preferable to measure the temperature of the electrolytic cell 20 as the temperature of the measurement position.

[0109] It is also possible to set the measurement target position on the outer wall of the tank 10. However, it is considered that setting the measurement target position on the electrolytic cell 20 makes it less likely that a difference will occur with the liquid temperature. This is because, when the temperature measuring element 81 is installed on the outer wall of the tank 10, the temperature measuring element 81 is likely to be strongly affected by the environmental temperature, making it difficult to accurately reflect the liquid temperature. The measured temperature T when the temperature measuring element 81 is installed on the electrolytic cell 20 DET is affected by the heat generated by the electrolytic cell 20 and the ambient temperature. DET The former effect on the temperature (the effect of heat generation by the electrolytic cell 20) is greater when the temperature measuring element 81 is installed on the electrolytic cell 20 than when the temperature measuring element 81 is installed on the outer wall of the tank 10. On the other hand, the temperature of the water in the tank 10 is linked to the temperature of the water in the electrolytic cell 20, and rises / falls in response to an increase / decrease in the amount of heat generated by the electrolytic cell 20. For this reason, it is considered that the temperature of the water in the tank 10 can be more accurately estimated by installing the temperature measuring element 81 at a position above the electrolytic cell 20, which is a position that effectively reflects the amount of heat generated by the electrolytic cell 20.

[0110] Furthermore, placing the temperature measuring element 81 closer to the center of the surface of the electrolytic cell 20 tends to reduce the difference with the liquid temperature. The reason for this is thought to be that placing the temperature measuring element 81 in the center of the surface of the electrolytic cell 20 (surface SF1 or SF2 described below) is less susceptible to the environmental temperature and more susceptible to the amount of heat generated by the electrolytic cell 20 than placing it at the edge of the surface of the electrolytic cell 20 (surface SF1 or SF2 described below). It is also thought that water electrolysis is relatively more active near the center of the surface than near the edge, and the amount of heat generated by the electrolytic cell 20 is more accurately reflected. Placing the temperature measuring element 81 in a position that better reflects the amount of heat generated by the electrolytic cell 20 is thought to enable more accurate estimation of the water temperature in the tank 10.

[0111] According to this embodiment, temperature compensation of conductivity is possible without directly measuring the liquid temperature. Since the liquid temperature is not measured directly by immersing a sheathed thermocouple or the like in the water in the tank 10, there is no concern about metal ions leaking out.

[0112] The following Examples EX2_1 to EX2_3 belong to the second embodiment. The matters described above in this embodiment apply to the following Examples unless otherwise specified and unless there is a contradiction. In each Example, if there is a matter that contradicts the matters described above, the description in that Example may take precedence. Furthermore, unless there is a contradiction, matters described in any of the following Examples can also be applied to any of the other Examples (i.e., any two or more of the multiple Examples can also be combined).

[0113] [Example EX2_1] An example EX2_1 will be described. This example is unique in that the temperature measuring element 81 is installed outside the tank 10 and temperature compensation is performed based on the temperature measured at a position outside the tank 10.

[0114] Therefore, the installation position of the temperature measuring element 81 (i.e., the measurement target position) can be set to a position on the outer wall of the tank 10 or a position on the electrolytic cell 20. It is also possible to set the measurement target position to a position other than these as long as the position can accurately reflect the temperature of the water in the tank 10.

[0115] However, as described above, it is preferable to install a temperature measuring element 81 in the electrolytic cell 20 and have the temperature sensor 80 measure the temperature of the electrolytic cell 20 .

[0116] To explain how to set the measurement target position in the electrolytic cell 20, the structure of the electrolytic cell 20 will be described with reference to Figures 17(a) to 17(c). For concrete explanation, three mutually perpendicular axes, the X axis, the Y axis, and the Z axis, are defined. The Z axis is parallel to the up-down direction (i.e., the vertical direction). Figure 17(a) is a schematic perspective view of the electrolytic cell 20. Figure 17(b) is a plan view of the electrolytic cell 20 when observed from a direction perpendicular to the X axis and the Z axis. Figure 17(c) is a structural diagram of the components of the electrolytic cell 20 that are involved in the electrolysis of water.

[0117] The electrolysis cell 20 includes a solid polymer membrane 21 and two electrodes, a cathode 22 and an anode 23, sandwiching the solid polymer membrane 21. The solid polymer membrane 21, the cathode 22, and the anode 23 are housed in a case for the electrolysis cell 20. In this embodiment, the case for the electrolysis cell 20 has a cylindrical shape. One of the top and bottom surfaces of the cylindrical case shape of the electrolysis cell 20 is surface SF1, and the other is surface SF2. The bottom surface of the cylinder is also referred to as the bottom surface. Surfaces SF1 and SF2 are flat surfaces facing each other and parallel to the X-axis and Y-axis. Here, surface SF1 is the top surface and surface SF2 is the bottom surface. The direction from the positive side to the negative side of the Z-axis corresponds to the downward direction (i.e., the direction of gravity), and therefore the top surface SF1 is located closer to the positive side of the Z-axis than the bottom surface SF2. The outer shapes of the top surface SF1 and the bottom surface SF2 are circles of the same size.

[0118] Within the case of the electrolysis cell 20, the solid polymer membrane 21, the cathode 22, and the anode 23 are disposed between an upper surface SF1 and a lower surface SF2. In this case, the cathode 22 is disposed between the solid polymer membrane 21 and the upper surface SF1, and the anode 23 is disposed between the solid polymer membrane 21 and the lower surface 23. Although not clear from FIG. 17(c), the solid polymer membrane 21, the cathode 22, and the anode 23 may each have a disk shape having a thickness in the Z-axis direction.

[0119] The electrolytic cell 20 has an upper output port 25 on its upper surface SF1, and an input port 24 and a lower output port 26 on its lower surface SF2. The input port 24 is connected to a pipe 30 (see FIG. 1) and receives water from the tank 10 via the pipe 30. The electrolytic cell power supply circuit 61 (see FIG. 1) can supply a constant current to the electrolytic cell 20 by applying a positive voltage to the anode 23 relative to the potential of the cathode 22. The electrolytic cell 20 electrolyzes water supplied to the input port 24 based on the supplied current. Hydrogen generated at the cathode 22 by electrolysis of water is output from the upper output port 25. Oxygen generated at the anode 23 by electrolysis of water is output from the lower output port 26. A portion of the water supplied to the input port 24 is electrolyzed and converted into hydrogen and oxygen. The remainder of the water supplied to the input port 24 (water that was not electrolyzed) is output from the upper output port 25 or the lower output port 26.

[0120] The upper outlet 25 is connected to a water separation trap 40 (see FIG. 1), and the hydrogen and water output from the upper outlet 25 are sent to the water separation trap 40. As described above, the water sent to the water separation trap 40 is returned to the tank 10 via the pipe 32 and the exhaust trap 13. The lower outlet 26 is connected to the pipe 31 (see FIG. 1). The oxygen and water output from the lower outlet 26 are sent to the supply port 11 via the pipe 31. As a result, the water output from the lower outlet 26 is returned to the tank 10 via the supply port 11.

[0121] The installation position of the temperature measuring element 81 (i.e., the measurement target position) may be set on the upper surface SF1 or on the lower surface SF2. Setting the measurement target position on the upper surface SF1 refers to installing and fixing the temperature measuring element 81 at the measurement target position on the upper surface SF1 in a manner that it contacts the upper surface SF1, and in this case, the temperature measuring element 81 is located above the upper surface SF1. Setting the measurement target position on the lower surface SF2 refers to installing and fixing the temperature measuring element 81 at the measurement target position on the lower surface SF2 in a manner that it contacts the lower surface SF2, and in this case, the temperature measuring element 81 is located below the lower surface SF2.

[0122] Furthermore, it is more preferable to install the temperature measuring element 81 in the center of the surface SF1 or SF2 than at the end of the surface SF1 or SF2. A preferred position for the measurement target position will be described with reference to Fig. 17(d).

[0123] In FIG. 17(d), the distance d1 REF represents the minimum distance from the center position 620 of the upper surface SF1 to the edge of the upper surface SF1. When the outer shape of the upper surface SF1 is a circle (a perfect circle), the distance d1 REF is equal to the radius of the upper surface SF1. The hydrogen generator 1 may be provided with an electrolytic cell 20 whose outer shape of the upper surface SF1 is different from a circle. For example, when the outer shape of the upper surface SF1 is a square, the distance between the midpoint of one side of the square and the center position 620 is distance d1. REF On the upper surface SF1, a predetermined distance d1 from the center position 620 TH The area within this range is referred to as area 625. That is, the distance between any position within area 625 and center position 620 is distance d1. TH When the measurement target position is set on the upper surface SF1, it is preferable to set the measurement target position within the region 625.

[0124] Here, “d1 TH / d1 REF Therefore, when the measurement target position is set within the region 625 on the upper surface SF1, the distance d1 REF The distance from the center position 620 to the measurement target position (≦d1 TH ) is equal to or smaller than M. M has a value less than 1, for example, "M=1 / 2". It is not essential that "M=1 / 2" holds; for example, "M=3 / 5" or "M=1 / 3" may also be used, but it is preferable to set the measurement target position as close to the center position 620 as possible.

[0125] In FIG. 17(d), the distance d2 REF represents the minimum value of the distance from the center position 630 of the lower surface SF2 to the edge of the lower surface SF2. When the outer shape of the lower surface SF2 is a circle (a perfect circle), the distance d2 REFis equal to the radius of the lower surface SF2. The hydrogen generator 1 may be provided with an electrolytic cell 20 whose outer shape of the lower surface SF2 is different from a circle. For example, when the outer shape of the lower surface SF2 is a square, the distance between the midpoint of one side of the square and the center position 630 is a distance d2 REF On the lower surface SF2, a predetermined distance d2 TH The area within this range is referred to as area 635. That is, the distance between any position within area 635 and the center position 630 is a distance d2 TH When the measurement target position is set on the lower surface SF2, it is preferable to set the measurement target position within the region 635.

[0126] Here, “d2 TH / d2 REF Therefore, when the measurement target position is set within the region 635 on the lower surface SF2, the distance d2 REF The distance from the center position 630 to the measurement target position (≦d2 TH ) is equal to or less than M. As described above, M has a value less than 1, for example, "M=1 / 2". It is not essential that "M=1 / 2" holds; for example, "M=2 / 5" or "M=1 / 3" may also be used, but it is preferable to set the measurement target position as close to the center position 630 as possible.

[0127] In addition, if the case of the electrolysis cell 20 has a cylindrical shape, as is mainly assumed in this embodiment, "d1 REF =d2 REF " and "d1 TH =d2 TH " is fine.

[0128] [Example EX2_2] Example EX2_2 will be described. Detecting conductivity EC with temperature compensation using the electrode unit 12 according to the first embodiment (see FIG. 5, etc.) DET The temperature compensation technique according to the second embodiment has been described on the assumption that the following is derived. However, the temperature compensation technique according to the second embodiment can be applied to any conductivity detection device.

[0129] That is, as shown in Fig. 18, the conductivity detecting device according to the second embodiment includes a conductivity meter CM and a temperature sensor 80 including a temperature measuring element 81. The conductivity meter CM is connected to the temperature sensor 80, and a measured temperature T DET receives a signal representing

[0130] The conductivity meter CM may be any conductivity meter that detects (measures) the conductivity of the water in the tank 10. For example, the conductivity meter CM has first and second electrodes that are inserted into the water in the tank 10 and spaced apart, and detects the conductivity of the water in the tank 10 based on the amplitude of the AC current that flows between the first and second electrodes when a predetermined AC voltage is applied between the first and second electrodes. In this case, the conductivity meter CM detects the conductivity of the water in the tank 10 based on the amplitude of the AC current that flows between the first and second electrodes when a predetermined AC voltage is applied between the first and second electrodes. DET The conductivity meter CM performs temperature compensation of the detected conductivity based on the amplitude of the AC current and the measured temperature T DET Based on this, the conductivity of the water in the tank 10 when it is assumed that the liquid temperature is at a predetermined reference temperature may be calculated as the temperature-compensated conductivity.

[0131] When the configuration of the first embodiment is used, the conductivity meter CM is made up of the electrode unit 12 and the detection circuit 64 (FIG. 11) or the detection circuit 64a (FIG. 13).

[0132] [Example EX2_3] Example EX2_3 will be explained.

[0133] As already mentioned, the outer shapes of the upper surface SF1 and the lower surface SF2 are not limited to circles and may be any shape. The outer shapes of the upper surface SF1 and the lower surface SF2 may be different.

[0134] Of the surfaces SF1 and SF2, it is assumed that surface SF1 is the upper surface and surface SF2 is the lower surface, but the positional relationship between surfaces SF1 and SF2 is not limited to this. For example, surface SF1 may be the lower surface and surface SF2 may be the upper surface. Surfaces SF1 and SF2 may be arranged side by side in the left-right direction. Furthermore, an anode 23 may be arranged between surface SF1 and the solid polymer membrane 21, and a cathode 22 may be arranged between surface SF2 and the solid polymer membrane 21.

[0135] Although the example of applying the conductivity detecting device according to the present invention to the hydrogen generator 1 has been described above, the conductivity detecting device according to the present invention can be applied to any application requiring detection of the conductivity of a liquid in a tank. For example, the conductivity detecting device according to the present invention may be applied to a functional water production device that produces various types of functional water. Furthermore, the liquid in the tank may be something other than water.

[0136] The embodiments of the present invention can be modified in various ways as appropriate within the scope of the technical ideas set forth in the claims. The above-described embodiments are merely examples of the present invention, and the meanings of the terms of the present invention and each constituent element are not limited to those described in the above-described embodiments. The specific numerical values ​​shown in the above description are merely examples, and as a matter of course, they can be changed to various numerical values. [Explanation of symbols]

[0137] 1 Hydrogen generator CS chassis 10 Tank 10R Water storage space 11 Supply port 12 electrode units 13 Exhaust trap 14 Check valve 20 electrolysis cells 21 Solid polymer membrane 22 Cathode 23 Anode 24 input ports 25 Upper output port 26 Downward output port SF1 top SF2 bottom side 30~32 Piping 33 Drain piping 40 Water Separator Trap 41 Hydrogen piping 42 Dryer 50~53 Hydrogen piping 54 Water discharge prevention filter 55 Solenoid valve 56 Safety valve 57 Pressure Sensor 58 Hydrogen generator 59 Hydrogen release port 60 Control and display unit 61 Electrolytic cell power supply circuit 62 Display section 63 Alarm output section 64 Water level and conductivity detection circuit 70 signal ports 71 Power Port 72 drain port 80 Temperature Sensor 81 Temperature measuring element 110 Reference electrode 111~113 Detection electrodes 110a~113a Covering part 110b~113b Exposed part 120 Electrode support 130 Wiring group 210 AC voltage source 220~222 IV conversion section 230 Water level determination section 240 Conductivity conversion unit CM conductivity meter

Claims

1. A water level and conductivity detection device that includes a reference electrode and one or more detection electrodes inserted into a tank in which a liquid is to be stored, and detects the water level in the tank by detecting the presence or absence of conduction between the reference electrode and the one or more detection electrodes, wherein the one or more detection electrodes include target detection electrodes covered with an insulator, wherein, among the reference electrodes, an electrode portion other than a reference exposed portion including the lower end of the reference electrode, and, among the target detection electrodes, an electrode portion other than a detection exposed portion including the lower end of the target detection electrode, are covered with an insulator, and detects the conductivity of the liquid in the tank using the reference electrode and the target detection electrode , a water level and conductivity detection device.

2. The lower end of the reference electrode is closer to the bottom surface of the tank than the lower end of the target detection electrode, and a detection circuit is provided that detects whether the water level in the tank is higher than the lower end of the target detection electrode based on the current between the reference electrode and the target detection electrode when an alternating voltage is applied between the reference electrode and the target detection electrode, and detects the conductivity of the liquid in the tank based on the current when the water level in the tank is higher than the lower end of the target detection electrode , the water level and conductivity detection device according to Claim 1.

3. As the one or more detection electrodes, a plurality of detection electrodes having different distances from the bottom surface of the tank are provided, the lower end of the reference electrode is closer to the bottom surface of the tank than the lower ends of the respective detection electrodes, and the detection circuit detects, for each of the detection electrodes, whether the water level in the tank is higher than the lower end of the detection electrode based on the current between the reference electrode and the detection electrode when the alternating voltage is applied between the reference electrode and the detection electrode , the water level and conductivity detection device according to Claim 2.

4. The target detection electrode is the detection electrode having the shortest distance from the bottom surface of the tank among the plurality of detection electrodes , the water level and conductivity detection device according to Claim 3.

5. Also, for detection electrodes different from the target detection electrode among the plurality of detection electrodes, an electrode portion other than an exposed portion including the lower end of the detection electrode is covered with an insulator , the water level and conductivity detection device according to Claim 3.

6. The reference electrode and the one or more detection electrodes extend downward from an electrode support that supports the reference electrode and the one or more detection electrodes, and in the vertical direction, the reference exposed portion and the detection exposed portion have lengths , the water level and conductivity detection device according to any one of claims 1 to 5.

7. In the vertical direction, the length of the reference exposed portion and the length of the detection exposed portion are each greater than 0 and less than or equal to 10 mm. , the water level and conductivity detection device according to claim 6.

8. The reference electrode has the reference exposed portion and a reference covering portion that is an electrode portion from the electrode support to the reference exposed portion. The target detection electrode has the detection exposed portion and a detection covering portion that is an electrode portion from the electrode support to the detection exposed portion. The reference covering portion and the detection covering portion are covered with an insulator. In the vertical direction, the length of the reference exposed portion is shorter than the length of the reference covering portion, and the length of the detection exposed portion is shorter than the length of the detection covering portion. , the water level and conductivity detection device according to claim 6.

9. It includes a temperature sensor that measures the temperature of the measurement target position outside the tank. Based on the measured temperature of the temperature sensor, temperature compensation of the detected conductivity is performed. , the water level and conductivity detection device according to any one of claims 1 to 5.

10. The temperature sensor measures the temperature of an electrolytic cell that generates hydrogen by electrolyzing water supplied from the tank. , the water level and conductivity detection device according to claim 9.

11. The electrolytic cell has a first surface and a second surface facing each other, and an anode and a cathode of the electrolytic cell are arranged between the first surface and the second surface. The measurement target position is set on the first surface or the second surface. , the water level and conductivity detection device according to claim 10.

12. A tank for storing water as a liquid. An electrolytic cell that generates hydrogen by electrolyzing water supplied from the tank. , including the water level and conductivity detection device according to any one of claims 1 to 5. , a hydrogen generator.

13. A water level and conductivity detection method for detecting the water level in a tank by using a reference electrode and one or more detection electrodes inserted into the tank for storing a liquid, and detecting the presence or absence of conduction between the reference electrode and the one or more detection electrodes. The method includes: including a target detection electrode covered with an insulator on the one or more detection electrodes. covering, with an insulator, an electrode portion other than the reference exposed portion including the lower end of the reference electrode among the reference electrodes and an electrode portion other than the detection exposed portion including the lower end of the target detection electrode among the target detection electrodes. detecting the conductivity of the liquid in the tank by using the reference electrode and the target detection electrode. , Water level and conductivity detection method.

14. In a conductivity detection device for detecting the conductivity of a liquid in a tank, it is provided with a temperature sensor for measuring the temperature of a measurement target position outside the tank, and based on the measured temperature of the temperature sensor, temperature compensation of the detected conductivity is performed , Conductivity detection device.

15. The temperature sensor measures the temperature of an electrolytic cell that generates hydrogen by electrolyzing water supplied from the tank , The conductivity detection device according to claim 14.

16. The electrolytic cell has a first surface and a second surface facing each other, and an anode and a cathode of the electrolytic cell are arranged between the first surface and the second surface, and the measurement target position is set on the first surface or the second surface , The conductivity detection device according to claim 15.

17. In a conductivity detection method for detecting the conductivity of a liquid in a tank, based on the measured temperature of the measurement target position outside the tank, temperature compensation of the detected conductivity is performed , Conductivity detection method.

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