Hydrogen sulfide-induced malfunction risk detection device

Abstract

To provide a device detecting defect risk due to hydrogen sulfide, which enables the progress of corrosion due to hydrogen sulfide to be automatically and constantly monitored, a hydrogen sulfide monitoring device capable of automatically and constantly monitoring hydrogen sulfide in an installation environment of electric equipment, and a hydrogen sulfide concentration reduction device.SOLUTION: A defect risk detection device includes: a light reflection portion 114 in which silver Ag is arranged; a light emission portion 102 irradiating the silver with light; a light detection portion 106 detecting reflected light from the silver; a measurement portion measuring the voltage corresponding to the current of the light detection portion while the silver is irradiated with the light; and a detection portion detecting a defect risk due to hydrogen sulfide on the basis of the measured voltage, wherein the detection portion determines whether or not a risk presage time has passed and whether or not the difference in the measured voltage is less than a second threshold less than a first threshold to thereby detect a risk. As a result, the progress of corrosion due to hydrogen sulfide can be monitored automatically and constantly, and a defect risk due to the hydrogen sulfide can be accurately detected.SELECTED DRAWING: Figure 2

Description

Technical Field

[0005]

[0001] The present invention relates to a defect risk detection device for hydrogen sulfide that detects the risk of defects occurring in a printed circuit board or the like due to corrosion by hydrogen sulfide, a hydrogen sulfide monitoring device that monitors the generation of hydrogen sulfide, and a hydrogen sulfide concentration reduction device.

Background Art

[0002] In sewage treatment facilities and the like, hydrogen sulfide is likely to be generated, and the metal parts (such as electrical wiring patterns) of printed circuit boards used in electrical equipment (including electrical facilities) are corroded by hydrogen sulfide. When the metal parts of the printed circuit board are corroded by hydrogen sulfide, defects such as short circuits in adjacent wiring patterns occur. For the maintenance of installed electrical equipment, it is preferable to monitor the concentration of hydrogen sulfide in the installation environment and detect signs of defects due to corrosion by hydrogen sulfide.

[0003] As a method for diagnosing the presence and degree of corrosiveness of corrosive substances in the atmosphere, ECOCHECKA (registered trademark) II manufactured by Nippon Finetech FQL Co., Ltd. is known. This includes five types of test metal pieces (silver, copper, iron-nickel alloy, aluminum, iron). After exposing these metal pieces to the measurement environment for a certain period (one month), the presence of corrosive gas and the approximate degree of corrosion (corresponding to the reference concentration of corrosive gas) are determined by comparing the discoloration of the test metal pieces afterwards with the color samples attached to the product. If the metal pieces after exposure are sent to Nippon Finetech FQL Co., Ltd. for analysis, for example, the hydrogen sulfide concentration (reference concentration) based on the result of quantitatively analyzing the corrosion amount of silver by fluorescence X-ray analysis or the like is reported.

[0004] Also, Patent Document 1 below discloses a corrosion environment monitoring device. This corrosion environment monitoring device constantly monitors the resistance of a printed circuit board pattern made of silver, and monitors an increase in the resistance value due to corrosion of the pattern (silver changing to silver oxide), thereby monitoring the concentration of corrosive substances (hydrogen sulfide) in the environment over a long period.

[0005] Patent Document 2 below discloses an environmental measuring device for accurately measuring corrosive gases in the atmosphere. This environmental measuring device detects the weight increase due to silver sulfidation (sulfur deposition) using a QCM (Quartz Crystal Microbalance) sensor. The QCM sensor is a mass sensor that utilizes the property that when the mass of the electrodes of a quartz oscillator changes due to corrosion, the resonant frequency decreases in proportion to the amount of corrosion.

[0006] Patent Document 3 discloses an environmental measuring device capable of quickly, accurately, and easily measuring the concentration of a target gas. Specifically, it involves photographing the degree of discoloration of a metal thin film sample (e.g., an alloy made of Cu-Ag-Sn) that discolors upon exposure to corrosive gases (e.g., sulfur dioxide, hydrogen sulfide, chlorine, ammonia, nitrogen oxides), and estimating the corrosive gas concentration by analyzing the intensity and proportion of the three color elements (red, blue, and green). For estimation purposes, the degree of discoloration is confirmed in advance through tests with various gases. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2019-113433 [Patent Document 2] International Publication No. 2013 / 186856 [Patent Document 3] Japanese Patent Publication No. 2011-196985 [Overview of the project] [Problems that the invention aims to solve]

[0008] In the maintenance of electrical equipment installed in environments where hydrogen sulfide may be generated, it is desirable to be able to automatically and continuously monitor the hydrogen sulfide concentration in the environment and the progression of corrosion caused by hydrogen sulfide. However, the method of exposing test metal pieces for a predetermined period and then analyzing them using fluorescent X-rays has the problem that the evaluation period, including the exposure period, takes more than one month. The evaluation results are the result of one month of exposure and can be said to be an average value for one month. Fluctuations in concentration within the one-month period cannot be evaluated. In addition, the installation, retrieval, and evaluation of test metal pieces are cumbersome and time-consuming, making it unsuitable for automatic, continuous monitoring.

[0009] In Patent Document 1, for the resistance of the silver pattern to clearly increase, the cross-section of the pattern must be completely sulfurized. In other words, by the time an increase in the resistance of the silver pattern is detected, a malfunction has already occurred. Therefore, the sensitivity is too low to detect the signs of malfunction due to corrosion of the printed circuit board.

[0010] Patent Document 2 requires a function to detect fluctuations in the resonant frequency, and the equipment for this purpose is expensive. Furthermore, it also reacts to weight increases due to phenomena other than sulfidation (for example, moisture adhesion or oxidation due to high humidity), so the accuracy as a method for detecting hydrogen sulfide is not sufficient.

[0011] Patent Document 3 describes a method that detects changes in the sample surface by color change, resulting in high sensitivity and the ability to evaluate multiple gases. However, it requires imaging the sample, decomposing it into individual color elements, and performing calculations, which necessitates expensive equipment. Furthermore, it requires a dedicated alloy substrate for evaluation, and the degree of color change must be confirmed beforehand through tests with various gases, making it unsuitable for automated, continuous monitoring applications.

[0012] When actually installing electrical equipment (such as switchboards) in water treatment facilities, etc., a hydrogen sulfide corrosion test is performed on a sample at the installation site beforehand. If no corrosion due to hydrogen sulfide is detected in the sample, it is assumed that hydrogen sulfide is not present, and the electrical equipment is installed without taking any corrosion countermeasures. The absence of hydrogen sulfide does not only mean that it is completely absent, but also includes cases where the hydrogen sulfide concentration is below a specified value and cannot be detected. However, hydrogen sulfide may be generated after the installation of electrical equipment due to changes in the conditions of the installation site.

[0013] Furthermore, if corrosion of samples due to hydrogen sulfide is detected as a result of corrosion measurements taken on samples before installation of electrical equipment, measures to counter hydrogen sulfide corrosion will be taken on the electrical equipment before installation. These measures include making the electrical equipment airtight and placing hydrogen sulfide adsorbents and ventilation fans inside the equipment. However, these measures are not permanent and may deteriorate over time (decreased airtightness, decreased adsorption capacity of the adsorbent).

[0014] Therefore, even for electrical equipment installed in an environment where hydrogen sulfide is not expected to be present, and even for electrical equipment that has already been mitigated, it is preferable to monitor for hydrogen sulfide after installation. In this case, since the presence of hydrogen sulfide is not assumed, the monitoring method should preferably be simple and inexpensive. However, neither the method of exposing the test metal piece for a predetermined period as described above, nor any of the methods described in Patent Documents 1 to 3, are suitable.

[0015] Therefore, the first objective of the present invention is to provide a hydrogen sulfide-induced malfunction risk detection device that can automatically and continuously monitor the progress of corrosion caused by hydrogen sulfide and detect the risk of malfunctions occurring in printed circuit boards and the like due to corrosion. The second objective of the present invention is to provide a hydrogen sulfide monitoring device and a hydrogen sulfide concentration reduction device that can automatically and continuously monitor the presence or absence of hydrogen sulfide in an environment in which electrical equipment is installed. [Means for solving the problem]

[0016] The malfunction risk detection device according to the first aspect of the present invention includes a reflective section on which silver is placed on its surface, a light-emitting section that irradiates light onto the silver on the surface of the reflective section, a light-detecting section that detects the light reflected by the silver on the surface of the reflective section, a measurement terminal that generates a voltage corresponding to the current flowing to the light-detecting section while light is irradiated from the light-emitting section onto the silver on the surface of the reflective section, a measurement section that measures the voltage of the measurement terminal, and a detection section that detects the risk of malfunction occurring due to corrosion by hydrogen sulfide on a printed circuit board placed around the reflective section based on the voltage measured by the measurement section. The elapsed time from the start of voltage measurement by the measurement section when the difference obtained by subtracting the minimum value in the time-series data composed of the voltages measured by the measurement section from the voltage measured by the measurement section becomes greater than a first threshold is defined as the reference time, and the time obtained by multiplying the reference time by a real number greater than 1 is defined as the risk prediction time. The detection section detects the risk by determining whether the risk prediction time has elapsed and whether the difference has become smaller than a second threshold, which is smaller than the first threshold, after the reference time has elapsed. This allows for automatic and continuous monitoring of the corrosion progress of printed circuit boards, enabling accurate detection of the risk of malfunctions due to corrosion.

[0017] Preferably, the failure risk detection device further includes a presentation unit that presents predetermined information, and the presentation unit presents information representing the risk when the detection unit determines that the difference has become smaller than a second threshold before the risk prediction time has elapsed, or that the risk prediction time has elapsed before the difference becomes smaller than the second threshold. This suppresses false detection of failure risk due to corrosion and enables accurate detection of failure risk due to corrosion even for various change patterns of hydrogen sulfide concentration.

[0018] More preferably, the display unit, upon determining the reference time, displays information indicating that corrosion due to hydrogen sulfide is progressing. This allows for notification of corrosion progression well before the risk of malfunction due to corrosion occurs.

[0019] More preferably, the real number is between 4 and 6. This allows for accurate estimation of the time when the concentration-day product reaches approximately 10,000 ppb-day, i.e., the time when the risk of malfunctions increases.

[0020] A hydrogen sulfide monitoring device according to the second aspect of the present invention includes a reflective section with silver on its surface, a light-emitting section that irradiates light onto the silver on the surface of the reflective section, a light-detecting section that detects the light reflected by the silver on the surface of the reflective section, a measuring terminal that generates a voltage corresponding to the current flowing through the light-detecting section while light is irradiated from the light-emitting section onto the silver on the surface of the reflective section, a measuring section that measures the voltage of the measuring terminal, and a determination section that determines whether or not it is necessary to reduce the hydrogen sulfide concentration based on the voltage measured by the measuring section. The determination section determines that it is necessary to reduce the hydrogen sulfide concentration when the voltage measured by the measuring section falls below a lower threshold. This makes it possible to automatically and continuously monitor the presence or absence of hydrogen sulfide and changes in its concentration in an environment where electrical equipment is installed, and to take measures to reduce the hydrogen sulfide concentration on the electrical equipment as needed.

[0021] Preferably, the determination unit, upon receiving notification that the voltage measured by the measurement unit has fallen below a higher threshold value which is greater than a lower threshold value, will indicate that a reduction in hydrogen sulfide concentration is necessary. This allows for ample time to prepare measures to reduce the hydrogen sulfide concentration in advance.

[0022] More preferably, the hydrogen sulfide monitoring device further includes a display unit that displays predetermined information after the determination unit has determined that a reduction in hydrogen sulfide concentration is necessary. This allows for measures to be taken against corrosion caused by hydrogen sulfide in electrical equipment that has not been protected against it, such as making it airtight and placing a hydrogen sulfide adsorbent inside the electrical equipment. If the electrical equipment already has a hydrogen sulfide adsorbent inside, the device can indicate the appropriate time to replace the adsorbent.

[0023] The hydrogen sulfide concentration reduction device according to the third aspect of the present invention is a hydrogen sulfide concentration reduction device provided inside an electrical device with an airtight structure, including a ventilation fan arranged inside the electrical device, an adsorbent arranged inside the electrical device for adsorbing hydrogen sulfide from the air flow formed by the ventilation fan, and the above-mentioned hydrogen sulfide monitoring device arranged inside the electrical device. The hydrogen sulfide monitoring device prompts the replacement of the adsorbent upon receiving a determination that the reduction of the hydrogen sulfide concentration is necessary. Thereby, the adsorbent can be replaced at an appropriate time.

[0024] Preferably, when prompting the replacement of the adsorbent, the presentation unit presents a message prompting the replacement of the reflection unit of the hydrogen sulfide monitoring device. Thereby, the reflection unit whose silver plating or the like has been corroded and cannot be used for measurement can be replaced, and the monitoring of the hydrogen sulfide concentration can be continued.

Advantages of the Invention

[0025] According to the present invention, the progress of corrosion caused by hydrogen sulfide can be automatically and constantly monitored, and the sign before a malfunction occurs can be detected. Further, according to the present invention, the generation of hydrogen sulfide and the change in the hydrogen sulfide concentration in the environment where the electrical device is installed can be automatically and constantly monitored.

Brief Description of the Drawings

[0026] [Figure 1] Figure 1 is a graph showing the results of exposing a printed circuit board to environments with various hydrogen sulfide concentrations. [Figure 2] Figure 2 is a block diagram showing the schematic configuration of a malfunction risk detection device according to the first embodiment of the present invention. [Figure 3] Figure 3 is a circuit diagram showing the optical detection system of the malfunction risk detection device shown in Figure 2. [Figure 4] Figure 4 is a flowchart showing the detection process of the malfunction risk executed by the malfunction risk detection device shown in Figure 2. [Figure 5] Figure 5 is a cross-sectional view showing the arrangement of the optical detection system according to the first modification. [Figure 6] Figure 6 is a cross-sectional view showing the arrangement of the optical detection system according to the second modification. [Figure 7] Figure 7 is a cross-sectional view showing the arrangement of the photodetector system according to the third modified example. [Figure 8] Figure 8 is a block diagram showing the schematic configuration of a hydrogen sulfide monitoring device according to a second embodiment of the present invention. [Figure 9] Figure 9 is a circuit diagram showing the optical detection system of the hydrogen sulfide monitoring device shown in Figure 8. [Figure 10] Figure 10 is a flowchart showing the hydrogen sulfide concentration monitoring process performed by the hydrogen sulfide monitoring device shown in Figure 8. [Figure 11] Figure 11 is a block diagram showing the schematic configuration of a hydrogen sulfide concentration reduction device. [Figure 12] Figure 12 is a flowchart showing the monitoring process for hydrogen sulfide concentration related to the fifth modified example. [Figure 13] Figure 13 is a graph showing the results of measurements taken in multiple environments using the defect risk detection device shown in Figure 2. [Figure 14] Figure 14 is a graph showing the measurement data from Figure 13, with the product of hydrogen sulfide concentration and number of days on the horizontal axis. [Figure 15] Figure 15 is a table showing the reference time T1, estimated A and B, and the corresponding concentration-day product for each time series of measurement data shown in Figure 13. [Figure 16] Figure 16 is a graph showing the results of the defect risk detection process performed by the defect risk detection device shown in Figure 2, overlaid on the data measured during that process (Figure 13). [Figure 17] Figure 17 is a graph that shows the results of the defect risk detection process performed by the defect risk detection device shown in Figure 2, overlaid on the graph shown in Figure 14. [Figure 18] Figure 18 is a graph showing the results of measurements taken at multiple locations using the hydrogen sulfide monitoring device shown in Figure 8. [Modes for carrying out the invention]

[0027] In the following embodiments, identical parts are assigned the same reference numeral. Their names and functions are also identical. Therefore, detailed descriptions of them will not be repeated.

[0028] (First Embodiment) The following (1) and (2) are known to be typical defects that occur when printed circuit boards are exposed to hydrogen sulfide. (1) Copper sulfide propagates (corrodes) from the printed circuit board pattern (wiring, land, etc.) to the surrounding area, reaching the adjacent pattern and causing a short circuit. (2) The entire cross-section inside the pattern of the printed circuit board becomes sulfurized, and the resistance value of that part increases. An investigation of past malfunctions revealed that in most cases, malfunction (1) occurred before malfunction (2). Therefore, it is preferable to be able to detect the precursors to malfunction (1) before it occurs. In this embodiment, the objective is to detect the risk of malfunction (1), such as short circuits in wiring, occurring due to corrosion of printed circuit boards, etc., contained in electrical equipment installed in an environment where hydrogen sulfide may be generated, by hydrogen sulfide (hereinafter referred to as the hydrogen sulfide malfunction risk).

[0029] Figure 1 shows the degree of corrosion of printed circuit boards in a hydrogen sulfide environment. Specifically, simulated printed circuit boards were exposed to multiple hydrogen sulfide environments with different concentrations, and the corrosion progression distance was measured according to the elapsed time from the start of exposure. The vertical axis represents the corrosion progression distance (μm), and the horizontal axis represents the product of the hydrogen sulfide concentration at the time of measurement and the number of days elapsed from the start of exposure to the time of measurement (concentration-days product (ppb-days)).

[0030] Typically, the distance between printed circuit board patterns is 100 μm or more, so if the corrosion progression distance is up to about 20 μm, it will not lead to insulation degradation (short circuits, etc.). That is, as shown by the downward arrow in Figure 1, if the corrosion progression distance is 20 μm or less, it is considered that there is no risk of malfunction occurring (including cases where the risk is small). On the other hand, as shown by the upward arrow, if the corrosion progression distance is 50 μm or more, the risk of malfunction occurring increases. From the measurement results shown in Figure 1, it can be seen that if the concentration-day product is approximately 15,000 ppb-day or less, the corrosion progression distance is 20 μm or less (see the shaded area). Therefore, to be on the safe side, it is preferable to be able to detect the time when the concentration-day product becomes approximately 10,000 ppb-day. It is even more preferable if the time when the concentration-day product becomes approximately 10,000 ppb-day can be predicted as early as possible. The malfunction risk detection device according to the first embodiment of the present invention predicts the time when the concentration-day product becomes approximately 10,000 ppb-day.

[0031] (Configuration of the malfunction risk detection device) Referring to Figure 2, the malfunction risk detection device 100 according to the first embodiment includes a light-emitting unit 102 that emits light, a power supply unit 104 that supplies power to the light-emitting unit 102, a light detection unit 106 that detects light, a control unit 108, a storage unit 110, a timer 112, and a light-reflecting unit 114. The malfunction risk detection device 100 also includes a power supply (not shown) for operating each unit, and an operating device (not shown) for inputting instructions to the control unit 108. For example, a computer keyboard, mouse, and touch panel can be used as the operating device. Figure 2 shows a printed circuit board 900 as an example of a target for corrosion caused by hydrogen sulfide.

[0032] The light-emitting unit 102 is implemented by, for example, a light-emitting diode (hereinafter referred to as an LED). The light-emitting unit 102 is not limited to an LED; any light-emitting element that can stably output light of a predetermined intensity in a predetermined direction for a predetermined time (for example, 0.1 to several seconds) is acceptable. The light-emitting unit 102 emits red light (for example, with a central wavelength of 630 nm). The power supply unit 104, under the control of the control unit 108, supplies power to the light-emitting unit 102 to light it up.

[0033] The light detection unit 106 is implemented, for example, by a phototransistor. The light detection unit 106 is not limited to a phototransistor; any element capable of detecting the light emitted from the light-emitting unit 102 and outputting an electrical signal (e.g., voltage, current) of a magnitude corresponding to its intensity (light quantity) is acceptable. Preferably, the light detection unit 106 has the central wavelength of the light emitted from the light-emitting unit 102, 630 nm, near the center of its detection sensitivity.

[0034] The light-reflecting portion 114 includes an L-shaped member 116 and silver Ag. Silver Ag is arranged on the two orthogonal surfaces 120 and 122 of the L-shaped member 116 on the side facing the light-emitting portion 102. Silver Ag may be arranged on the entire surface of surfaces 120 and 122, or on only a portion of surfaces 120 and 122. For example, surfaces 120 and 122 are silver-plated. As a result, as shown by the dotted arrow in Figure 2, the light emitted from the light-emitting portion 102 is reflected by the silver Ag and incident on the light-detecting portion 106. The L-shaped member 116 is formed in an L-shape in cross-section, allowing the optical path from the light-emitting portion 102 to the light-detecting portion 106 to be contained in a relatively narrow space. The L-shaped member 116 only needs to be arranged so that the two surfaces 120 and 122 form approximately 90°, and the term L-shape includes such shapes. The L-shaped member 116 can be formed, for example, by bending a metal plate. The L-shaped member 116 may also be formed by joining two planar members so that they are substantially perpendicular to each other.

[0035] The light-emitting unit 102 and the light-detecting unit 106 can be realized, for example, by a photoreflector, which is an element that houses an LED and a phototransistor in a single package. This reduces the number of components and allows for a compact light-detecting system.

[0036] The light-emitting unit 102, the light-detecting unit 106, and the light-reflecting unit 114 constitute a light detection system. The light detection system of the malfunction risk detection device 100 is located, for example, near a printed circuit board 900 inside electrical equipment installed in an environment where hydrogen sulfide may be generated. However, it is not limited to inside electrical equipment; it is sufficient that light emitted from the light-emitting unit 102 is detected by the light-detecting unit 106, and the light-emitting unit 102, the light-detecting unit 106, and the light-reflecting unit 114 are located in an environment where ambient light can be shielded. The location of the power supply unit 104, the control unit 108, the storage unit 110, and the timer 112 is arbitrary and may be located inside or outside the electrical equipment being monitored.

[0037] The control unit 108 is a CPU (Central Processing Unit) and controls the output of the power supply unit 104 to turn the light-emitting unit 102 on or off. For example, when the control unit 108 outputs a high-level signal (e.g., 5V) to the power supply unit 104, the power supply unit 104 supplies power to the light-emitting unit 102. As a result, the light-emitting unit 102 lights up. When the control unit 108 outputs a low-level signal (e.g., 0V) to the power supply unit 104, the power supply unit 104 stops supplying power to the light-emitting unit 102. As a result, the light-emitting unit 102, which was lit, turns off.

[0038] Furthermore, the control unit 108 acquires the output signal from the light detection unit 106 at predetermined timings. For example, if the light detection unit 106 has an A / D conversion function, the control unit 108 acquires the digital data output from the light detection unit 106. If the light detection unit 106 outputs an analog signal, the control unit 108 samples the input analog signal at predetermined time intervals to generate digital data.

[0039] The memory unit 110 is a volatile or non-volatile memory that stores data input from the control unit 108. The timer 112 outputs the current time upon request from the control unit 108. When the timer 112 receives a reset request from the control unit 108, it resets the current time to 0, then counts the elapsed time to set the current time.

[0040] As described above, the light emitted from the light-emitting unit 102 is reflected by the silver Ag on the surface 120, reflected again by the silver Ag on the surface 122, and returns to approximately parallel to the optical axis of the light-emitting unit 102, where it is detected by the light-detecting unit 106. The amount of light measured by the light-detecting unit 106 changes depending on the state of the silver Ag on the light-reflecting unit 114. As the silver Ag is corroded by hydrogen sulfide, the reflectivity of light decreases, so the measured value becomes smaller. The degree of corrosion of the silver Ag on the light-reflecting unit 114 increases with the hydrogen sulfide concentration in the surrounding environment and the time elapsed since the light-reflecting unit 114 was installed in the electrical equipment. Therefore, by periodically controlling the power supply unit 104 with the control unit 108 to turn on the light-emitting unit 102 and measuring the amount of light detected by the light-detecting unit 106, changes in the corrosion state of the silver Ag can be observed.

[0041] Figure 3 shows an example of a light detection system circuit using an LED in the light-emitting section 102 and a phototransistor in the light-detecting section 106. Referring to Figure 3, the light-emitting section 102 includes an LED 130 and a resistor R1 connected in series between terminals 140 and 142. In Figure 3, the silver Ag arranged or formed (silver-plated) on the light-reflecting section 114 is shown as a flat plate for convenience. The light-detecting section 106 includes a phototransistor 132, resistors R2 and R3 connected in series between terminals 144 and 146.

[0042] With terminals 142 and 146 grounded, the LED 130 emits light (red light) when a DC voltage is applied from the power supply unit 104 between terminals 140 and 142 of the light-emitting unit 102. When a predetermined DC voltage is applied between terminals 144 and 146, the light detection unit 106 detects when light (the light emitted from the light-emitting unit 102 reflected by silver Ag (red light)) is incident on the phototransistor 132, causing the phototransistor 132 to turn on and current to flow (current flows between terminals 144 and 146). The control unit 108 measures the voltage generated at the measurement terminal 134 due to the resulting voltage drop (hereinafter referred to as the generated voltage). Since the current value flowing through the phototransistor 132 depends on the amount of light incident on the phototransistor 132, the generated voltage measured at the measurement terminal 134 represents the amount of light incident on the phototransistor 132. Note that resistors R1, R2, and R3 should have appropriate resistance values ​​corresponding to the LED 130 and the phototransistor 132. Resistors R1, R2, and R3 may be variable resistors.

[0043] It is efficient if the generated voltage can be evaluated as a relative value. At the start of measurement, the silver Ag of the light reflecting part 114 is in an uncorroded state (hereinafter also referred to as the initial state). Therefore, for example, by adjusting the circuit in Figure 3 so that the value of the generated voltage measured in the initial state of the silver Ag of the light reflecting part 114 becomes a predetermined value (e.g., "130"), the generated voltage can be evaluated as a relative value. The circuit in Figure 3 is adjusted by adjusting the value of any of the resistors R1 to R3.

[0044] (Detection process for defect risk) The following describes the process for detecting the risk of malfunctions caused by hydrogen sulfide in printed circuit boards of electrical equipment, as performed by the malfunction risk detection device 100 in Figure 2, with reference to Figure 4. As described above, the risk of malfunctions caused by hydrogen sulfide is detected by detecting the time when the concentration-day product reaches approximately 10,000 ppb-day.

[0045] The process shown in Figure 4 is performed by the control unit 108 reading a predetermined program stored in the storage unit 110 and executing it. The light-emitting unit 102 and the light-detecting unit 106 constitute the circuit shown in Figure 3, and the light-detecting system of the malfunction risk detection device 100 is assumed to be located inside electrical equipment (such as a power distribution board) (a dark place where external light does not enter).

[0046] The storage unit 110 of the malfunction risk detection device 100 stores information for identifying the time to perform a measurement (hereinafter referred to as measurement time information), a first threshold K1, a second threshold K2, a constant N, and a message. The measurement time information can be any information, as long as it is specified according to when the measurement is to be performed. For example, if measurements are to be performed at regular time intervals, the measurement time information can be the start time and the time interval Δt. If measurements are to be performed at a predetermined time, the measurement time information can be any information that directly represents the time. Here, we assume that measurements are to be performed every hour (Δt = 1 (hour)). In the process shown below, the time is represented by the elapsed time from the start of the measurement (the time of the first measurement). For example, when the control unit 108 starts a series of measurements, it resets the timer 112, so the current time output by the timer 112 represents the elapsed time from the first measurement.

[0047] The first threshold K1 and the second threshold K2 are real numbers, and if the circuit in Figure 3 is pre-adjusted so that the generated voltage measured in the initial state of the silver Ag of the light reflecting part 114 is "130", then for example, 5≦K1≦15 and 3≦K2≦10. The constant N is a real number greater than 1, for example, 4≦N≦6. The message includes a message indicating that corrosion by hydrogen sulfide is progressing (hereinafter referred to as a corrosion progression alarm) and a message indicating the risk of malfunction due to hydrogen sulfide (hereinafter referred to as a malfunction risk alarm).

[0048] In step 300, the control unit 108 obtains the current time from the timer 112 and refers to the measurement time information stored in the memory unit 110 to determine whether or not the measurement time has arrived. If it is determined that the measurement time has arrived, the control proceeds to step 302. Otherwise, the control proceeds to step 322.

[0049] In step 302, the control unit 108 turns on the light-emitting unit 102 and measures the voltage generated at the measurement terminal 134. The measured voltage is stored in the storage unit 110 in correspondence with the elapsed time T from the start of measurement. After that, the control unit 108 turns off the light-emitting unit 102 and the control proceeds to step 304. Step 302 is executed repeatedly, so a series of time-series data is stored in the storage unit 110.

[0050] In step 304, the control unit 108 determines whether the singularity can be removed. If it is determined that it can be removed, the control proceeds to step 306. Otherwise, the control proceeds to step 322. When the door is opened during inspection of electrical equipment, external light may enter the equipment, and the light detection system may also be illuminated. In such a state, if the measurement timing for the generated voltage arrives and the measurement is performed, the measured value will be larger than the original value. Also, due to condensation, the measured value may be smaller than the original value. In order to appropriately evaluate the degree of silver corrosion by hydrogen sulfide, it is preferable to remove these abnormal measurement values ​​as singularities. To remove singularities, for example, the moving median can be used as the representative value. Specifically, in time-series data, the value located in the middle (median) when a predetermined number of consecutive data (for example, 25 (number of measurements in 24 hours)) are arranged in order of magnitude is used as the representative value. That is, since a predetermined number of measurement data is required to calculate the moving median, it is not determined that the singularity has been removed until the predetermined number of measurement data is obtained.

[0051] In step 306, the control unit 108 removes singularities from the series of time-series data measured in step 302. Specifically, the control unit 108 calculates a moving median for a predetermined number of past measurement data consecutive to the most recent measurement data (the data measured when step 302 was last executed), and stores this moving median in the storage unit 110, corresponding it to the measurement time of the most recent measurement data. After that, control proceeds to step 308. As described above, once the process of calculating the moving median is possible, step 306 is executed each time new measurement data is acquired. Therefore, the time-series data from which singularities have been removed from the time-series data measured in step 302 is stored in the storage unit 110. The data from which singularities have been removed (generated voltage) is represented by Y. As described above, in step 302, the measured generated voltage and the elapsed time T are associated and stored in the storage unit 110. Therefore, the data determined in step 306 (data from which singularities have been removed) corresponds to the elapsed time T stored in step 302, which was the last step performed before the data was determined.

[0052] In step 308, the control unit 108 reads the time-series data Y stored in the storage unit 110 and determines its minimum value Ymin. The control unit 108 stores the determined minimum value Ymin in the storage unit 110. After that, the control proceeds to step 310.

[0053] In step 310, the control unit 108 determines whether or not the estimated A, described later, has been determined. Specifically, the control unit 108 determines whether or not estimated A is stored in the memory unit 110. If it is stored, estimated A is determined to be determined, and control proceeds to step 316. Otherwise, control proceeds to step 312.

[0054] In step 312, the control unit 108 reads the first threshold K1 and the minimum value Ymin from the storage unit 110, subtracts the minimum value Ymin from the data Y (let's call it Ylst) determined in the last executed step 306 to calculate the difference ΔY (ΔY = Ylst - Ymin), and determines whether the difference ΔY is greater than the first threshold K1. If it is determined that ΔY > K1, the control proceeds to step 314. Otherwise (ΔY ≤ K1), the control proceeds to step 316.

[0055] In step 314, the control unit 108 reads from the storage unit 110 the time (elapsed time) T1 (hereinafter referred to as the reference time) and a constant N when the voltage generated at the measurement terminal 134 was measured in the last executed step 302, and takes the value obtained by multiplying the reference time T1 and the constant N as the estimated A (estimated A = T1 × N). Estimated A is an estimate of the time when the concentration-day product becomes approximately 10,000 ppb-day, as will be described later as an example. Estimated A is also called the risk prediction time. The control unit 108 stores estimated A in the storage unit 110. After that, the control proceeds to step 315.

[0056] In step 315, the control unit 108 reads out and presents the corrosion progress warning from the storage unit 110. As described above, the corrosion progress warning is a message indicating that the corrosion by hydrogen sulfide is progressing. If the defect risk detection device 100 includes an acoustic output device or an image display device, the message can be presented as sound or an image. Data representing the message to be presented may be transmitted from the defect risk detection device 100 to an external acoustic output device or image display device by wired communication or wireless communication. Thereby, the message is presented by the acoustic output device or image display device arranged in a management room or the like. As will be described later, the reference time T1 is a time considerably before the defect risk becomes high, but the corrosion by hydrogen sulfide is progressing. If the electrical equipment continues to be used in this environment, the defect risk becomes high when approximately 3 to 5 times the reference time T1 has elapsed. Therefore, it is preferable to present the corrosion progress warning at the timing when it is determined in step 312 that ΔY>K1 and the reference time T1 is specified in step 314. Thereafter, the control proceeds to step 316.

[0057] [[ID=???]] In step 316, the control unit 108 determines whether the estimated A (risk omen time) determined in step 314 has elapsed. Specifically, the control unit 108 acquires the current time (elapsed time since the start of measurement) from the timer 112 and compares the acquired current time with the estimated A. If it is determined that the estimated A has elapsed, the control proceeds to step 320. Otherwise, the control proceeds to step 318.

[0058] In step 318, the control unit 108 reads out the second threshold value K2 and the minimum value Ymin from the storage unit 110, subtracts the minimum value Ymin from the data Ylst determined in the last executed step 306 to calculate the difference ΔY (ΔY = Ylst − Ymin), and determines whether the difference ΔY is less than the second threshold value K2. If it is determined that ΔY<K2, the control proceeds to step 319. Otherwise (ΔY≧K2), the control proceeds to step 322.

[0059] It seems there is an issue with ID=5 in the original text as it's repeated in the translation part. Please check and correct if needed. Also, the "??? " in the translation for ID=4 seems incorrect, it should be the correct ID number as in the original text.In step 319, the control unit 108 reads from the storage unit 110 the elapsed time when the generated voltage of the measurement terminal 134 was measured by the last executed step 302, and sets it as estimated B. The control unit 108 stores estimated B in the storage unit 110. Thereafter, the control proceeds to step 320.

[0060] In step 320, the control unit 108 reads the defect risk warning from the storage unit 110 and presents it. As described above, the defect risk warning is for notifying the defect risk due to hydrogen sulfide. For example, it presents that there is a high possibility that a defect has occurred in the printed circuit board inside the electrical equipment.

[0061] In addition to the defect risk warning, estimated A or estimated B may be presented as the risk timing. In that case, if estimated B is stored in the storage unit 110, estimated B is presented. If estimated B is not stored in the storage unit 110 (estimated A has elapsed before estimated B is determined), estimated A is presented. Note that as long as a message notifying the defect risk due to hydrogen sulfide can be presented, step 319 may not be necessary when the risk timing is not presented. That is, even if it is determined YES in step 318, the process may proceed to step 320 without performing the process of determining estimated B (step 319).

[0062] Step 320 is executed when either the elapse of the risk omen time (estimated A) (the determination result in step 316 is YES) or ΔY < K2 (the determination result in step 318 is YES) is realized. When the risk omen time has elapsed, as described above, it means that the time when the concentration·days product becomes about 10,000 ppb·days has arrived, and the possibility of a defect due to hydrogen sulfide occurring becomes high. Also, as will be described later as an example, even when ΔY < K2 is realized before the risk omen time has elapsed, the concentration·days product becomes a value close to 10,000 ppb·days. Therefore, when ΔY < K2 is realized before the risk omen time has elapsed, it is notified at that point that there is a high possibility that a defect due to hydrogen sulfide has occurred.

[0063] In step 322, the control unit 108 determines whether or not it has received a termination instruction. If it has received a termination instruction, the program terminates. Otherwise, control returns to step 300 and repeats the above process. The termination instruction is given, for example, by turning off the power to the malfunction risk detection device 100.

[0064] As a result, the risk of malfunctions due to hydrogen sulfide in printed circuit boards within electrical equipment can be automatically detected without calculating the hydrogen sulfide concentration in the surrounding environment where the electrical equipment is located. In other words, when the hydrogen sulfide concentration-day product reaches approximately 10,000 ppb-day, that is, when the risk of malfunction is likely to occur, the system can automatically and continuously monitor the situation, and even if the hydrogen sulfide concentration changes, the system can accurately detect the signs of malfunction risk. By detecting signs of malfunction risk, countermeasures can be taken before performance degradation or failure occurs in the electrical equipment, allowing for proper management of the electrical equipment.

[0065] The above describes the case in which a corrosion progression alarm is issued in step 315, but is not limited to this. As mentioned above, the reference time T1 is well before the risk of failure becomes high, and it is not necessary to issue a corrosion progression alarm. As long as a failure risk alarm is issued in step 320, as mentioned above, measures can be taken to address corrosion and the electrical equipment can be properly managed.

[0066] The reference time T1, estimated A, and estimated B are expressed as elapsed time from the start of measurement, as described above. The elapsed time may be expressed in units of days, hours, minutes, and seconds, or in combination of these units. For example, when expressing the elapsed time in units of days, it may be expressed as a real number including decimal places, or rounded to a predetermined number of digits. Since the presentation of the risk of malfunction due to hydrogen sulfide is not urgent enough to require expression in units of hours, minutes, and seconds, the reference time T1, estimated A, and estimated B may be rounded to the nearest day.

[0067] The malfunction risk detection device 100 has a relatively simple equipment configuration and can be realized as an inexpensive device. By silver-plating the L-shaped member 116, the light-reflecting part 114 can be easily and inexpensively realized.

[0068] By forming the light-reflecting section 114 in an L-shape, the light detection system can be made compact. Furthermore, since the light from the light-emitting section 102 is incident at an oblique angle on the reflective surface of the light-reflecting section 114, the area of ​​the light-reflecting portion can be increased. This allows the effect of the discoloration of silver (Ag) over a wider area to be reflected in the generated voltage, resulting in more stable measurement data.

[0069] By observing the corrosion of silver (Ag) as a change in light reflectivity (change in generated voltage), early signs of malfunction risk due to hydrogen sulfide can be detected with high accuracy. Since the measurement result (generated voltage) is an electrical signal, remote monitoring is easily possible. Furthermore, the malfunction risk detection device 100 can easily continue observation simply by replacing the light reflecting part 114. For example, if the message (malfunction risk alarm) presented in step 320 includes a statement that the light reflecting part 114 needs to be replaced, the accuracy of detecting malfunction risk due to hydrogen sulfide can be maintained at a high level by replacing the light reflecting part 114.

[0070] The values ​​of the first threshold K1, the second threshold K2, and the constant N described above are examples and are not limited to the above values. For example, from the measurement results, a constant N can be determined that is appropriate for estimating the risk period (concentration-day product = approximately 10,000 (ppb-day)) by estimation A or estimation B. It is preferable that N = 5.

[0071] Furthermore, the measurement time interval and the number of data points used to calculate the moving median are not limited to the values ​​mentioned above. The measurement time interval may be between 1 minute and 1 hour, and the number of data points used to calculate the moving median may be data measured between half a day and 2 days.

[0072] The above describes the use of the moving median to remove singularities from measurement data, but it is not limited to this. For example, a moving mean may be used instead of the moving median. Furthermore, instead of a simple moving mean, the mean of a series of consecutive measurement data points arranged in descending order may be used. For example, when dealing with 25 consecutive measurement data points, the mean of the 11th to 15th measurement data points can be used.

[0073] (First variation) The above describes a case where silver Ag is placed on surfaces 120 and 122 of the L-shaped member 116 to reflect the radiant light from the light-emitting part 102, but the invention is not limited to this. As shown in Figure 5, silver Ag may be placed on only one of the surfaces 120 and 122. For example, Figure 5(a) shows a configuration in which silver Ag is placed (e.g., silver plating) on ​​a horizontal surface 120. Silver Ag may be placed on the entire surface 120, or only on a part of it. Figure 5(b) shows a configuration in which silver Ag is placed (e.g., silver plating) on ​​a vertical surface 122. Silver Ag may be placed on the entire surface 122, or only on a part of it. In both cases of Figure 5(a) and (b), it is preferable that the surface on which silver Ag is not placed is made of a material that is not corroded by hydrogen sulfide and is mirror-finished to reflect light.

[0074] (Second variation) The above describes a case where silver Ag is placed directly on the surface of the L-shaped member 116, but it is not limited to this. A configuration using a silver-plated plate is also possible. For example, as shown in Figure 6, a configuration in which a silver-plated plate 124 is placed on top of the L-shaped member 116 is possible. The surface 122 where silver Ag is not placed is preferably made of a material that is not corroded by hydrogen sulfide and is mirror-finished to reflect light. With such a configuration, even after a malfunction risk alarm is issued as described above, measurement can be easily resumed by simply replacing the corroded silver-plated plate 124 with a new one.

[0075] (Third variation) The above describes the case in which an L-shaped member 116 with an L-shaped cross-section and a light-reflecting part 114 containing silver Ag are used, but the invention is not limited to this. Instead of the light-reflecting part 114, a flat plate 126 and a light-reflecting part 118 containing silver Ag may be used, as shown in Figure 7. Silver Ag is arranged (for example, silver-plated) on one of the planes of the flat plate 126, and the light emitted from the light-emitting part 102 is reflected once by the silver Ag and detected by the light-detecting part 106.

[0076] As shown in the first to third modified examples, by reflecting the synchrotron radiation from the light-emitting unit 102 only once by silver Ag, it is possible to suppress the attenuation of reflected light from becoming too small when the silver Ag is corroded and discolored. As shown in Figure 2, if the synchrotron radiation from the light-emitting unit 102 is reflected twice by corroded and discolored silver Ag (silver sulfide), the amount of light incident on the light-detecting unit 106 becomes too small. Consequently, the measured generated voltage also becomes too small, and the measurement accuracy decreases. By configuring as in the first to third modified examples, the decrease in measurement accuracy can be suppressed, and the decrease in the detection accuracy of risks due to corrosion by hydrogen sulfide can be suppressed.

[0077] (Fourth variation) Figures 2, 5, and 6 illustrate the case where the light-detecting unit 106 is positioned above the light-emitting unit 102, but the case is not limited to this. In Figures 2, 5, and 6, the positions of the light-emitting unit 102 and the light-detecting unit 106 may be swapped, with the light-emitting unit 102 positioned above the light-detecting unit 106.

[0078] (Second Embodiment) The first embodiment described above is effective for electrical equipment installed in an environment where hydrogen sulfide is present and for which no measures have been taken to prevent corrosion by hydrogen sulfide. On the other hand, even for electrical equipment installed in an environment where hydrogen sulfide is not detected (although there is a possibility of hydrogen sulfide generation), or for electrical equipment for which measures have been taken to reduce hydrogen sulfide concentration, it is necessary to constantly monitor hydrogen sulfide, but it is preferable to be able to monitor hydrogen sulfide in a simpler way. The hydrogen sulfide monitoring device according to the second embodiment of the present invention monitors hydrogen sulfide in a simpler way than the malfunction risk detection device of the first embodiment.

[0079] The detection of hydrogen sulfide before the installation of electrical equipment is performed, for example, by measuring the degree of corrosion using metal (silver) samples. Specifically, this is done using the EcoChecker II manufactured by Eurofins FQL Co., Ltd. That is, the EcoChecker II, containing five types of test metal pieces (silver, copper, iron-nickel alloy, aluminum, and iron), is exposed to the measurement environment for a certain period (1 month), then retrieved, and the presence or absence of corrosive gases and their approximate concentration are determined by comparing the discoloration of the test metal pieces with the color chart provided with the product. The approximate concentration is the degree of corrosiveness of the atmosphere to the metal during the period of exposure, converted into the concentration of corrosive components (hydrogen sulfide concentration).

[0080] Hydrogen sulfide is detected by the discoloration of a silver test metal piece. If the target concentration, determined by comparing the discoloration of the silver test metal piece with a corresponding color chart, is less than, for example, 3 ppb, it is determined that hydrogen sulfide is not present, and electrical equipment is installed without taking measures against hydrogen sulfide. Otherwise (if the target concentration is 3 ppb or higher), the electrical equipment is installed after taking measures to reduce the hydrogen sulfide concentration. Measures to reduce the hydrogen sulfide concentration in electrical equipment include making the electrical equipment airtight and placing hydrogen sulfide adsorbents and ventilation fans inside the electrical equipment, as described later. Alternatively, the metal piece after exposure may be sent to Eurofins FQL Co., Ltd. for analysis, and the results of a quantitative analysis of the amount of silver corrosion by fluorescent X-ray analysis, etc., can be obtained and used to determine whether hydrogen sulfide countermeasures are necessary for the electrical equipment.

[0081] (Configuration of the hydrogen sulfide monitoring device) Referring to Figure 8, the hydrogen sulfide monitoring device 200 according to the second embodiment of the present invention includes a light-emitting unit 202 that emits light, a power supply unit 104 that supplies power to the light-emitting unit 202, a light-detecting unit 206 that detects light, a control unit 208, a storage unit 110, a timer 112, and a light-reflecting unit 114. The hydrogen sulfide monitoring device 200 is arranged, for example, inside electrical equipment 910 such as a power distribution board. The hydrogen sulfide monitoring device 200 is the same as the malfunction risk detection device 100 shown in Figure 2, except that the light-emitting unit 102, the light-detecting unit 106, and the control unit 108 are replaced by the light-emitting unit 202, the light-detecting unit 206, and the control unit 208, respectively. The configuration other than the light-emitting unit 202, the light-detecting unit 206, and the control unit 208 is the same as the malfunction risk detection device 100. Therefore, in the following, we will mainly explain the differences without repeating redundant explanations.

[0082] The light-emitting unit 202 is implemented by, for example, an LED. The light-emitting unit 202 is not limited to an LED; any light-emitting element capable of stably outputting light of a predetermined intensity in a predetermined direction for a predetermined time (for example, 0.1 to several seconds) is acceptable. The wavelength of the light emitted from the light-emitting unit 202 is arbitrary, as long as it is a wavelength that can be detected by the light-detecting unit 206. The light emitted from the light-emitting unit 202 is, for example, visible light, infrared light, or ultraviolet light. The power supply unit 104, under the control of the control unit 208, supplies power to the light-emitting unit 202 to light it up. It is desirable that the light emitted from the light-emitting unit 202 be red light, as this allows the hydrogen sulfide monitoring device 200 to be made common with the malfunction risk detection device 100 of the first embodiment.

[0083] The light detection unit 206 is implemented, for example, by a phototransistor. The light detection unit 206 is not limited to a phototransistor; any element capable of detecting the light emitted from the light-emitting unit 202 and outputting an electrical signal (e.g., voltage, current) of a magnitude corresponding to its intensity (amount of light) is acceptable. Preferably, the light detection unit 206 has the central wavelength of the light emitted from the light-emitting unit 202 near the center of its detection sensitivity.

[0084] The light-emitting unit 202, the light-detecting unit 206, and the light-reflecting unit 114 are arranged inside the electrical equipment 910. However, they are not limited to being inside the electrical equipment; it is sufficient that the light emitted from the light-emitting unit 202 is detected by the light-detecting unit 206, and the light-emitting unit 202, the light-detecting unit 206, and the light-reflecting unit 114 are arranged in an environment that can shield them from ambient light. In Figure 8, the entire hydrogen sulfide monitoring device 200 is shown to be arranged inside the electrical equipment 910, but the locations of the power supply unit 104, the control unit 208, the memory unit 110, and the timer 112 are arbitrary and may be arranged inside or outside the electrical equipment 910 that is being monitored.

[0085] The light-emitting unit 202, the light-detecting unit 206, and the light-reflecting unit 114 constitute a light detection system. The detection system of the hydrogen sulfide monitoring device 200 is implemented by a circuit similar to that of the malfunction risk detection device 100. Figure 9 shows an example of a light detection system circuit using an LED for the light-emitting unit 202 and a phototransistor for the light-detecting unit 206. Figure 9 is a circuit similar to that of Figure 3. Unlike Figure 3, the light emitted from the LED 230 in Figure 9 is not limited to red light. The phototransistor 232 detects the light emitted from the LED 230.

[0086] The control unit 208, like the control unit 108 of the malfunction risk detection device 100, is a CPU that controls the output of the power supply unit 104 to control the lighting of the light-emitting unit 202 and detects light with the light detection unit 206. The difference between the control unit 208 and the control unit 108 is that while the control unit 108 detects malfunction risks caused by hydrogen sulfide (such as short circuits due to corrosion of printed circuit board patterns), the control unit 208 detects the presence of hydrogen sulfide.

[0087] (Monitoring and processing of hydrogen sulfide) The following describes the process of detecting hydrogen sulfide in the installation environment of electrical equipment using the hydrogen sulfide monitoring device 200 shown in Figure 8, with reference to Figure 10. Here, it is assumed that the hydrogen sulfide monitoring device 200 is located inside electrical equipment 910 that has not been protected against corrosion by hydrogen sulfide. At least the light detection system (light-emitting unit 202, light-detecting unit 206, and light-reflecting unit 114) must be located inside the electrical equipment (such as a distribution board) (in a dark place where external light does not enter).

[0088] The process shown in Figure 10 is performed by the control unit 208 reading and executing a predetermined program that is pre-stored in the memory unit 110. The light-emitting unit 202 and the light-detecting unit 206 constitute the circuit shown in Figure 9, and the circuit in Figure 9 (resistors R1, R2, and R3) is pre-adjusted so that the generated voltage measured in the initial state of the silver Ag of the light-reflecting unit 114 is "130".

[0089] Assume that the storage unit 110 of the hydrogen sulfide monitoring device 200 stores measurement time information, a predetermined threshold Th, and a warning message. The measurement time information can be any information, as long as it is specified according to when the measurement is to be performed. For example, if measurements are to be taken at regular time intervals, the measurement time information can be the start time and the time interval Δt. If measurements are to be taken at a predetermined time, the measurement time information can be any information that directly represents the time. Here, we assume that measurements are taken every hour (Δt = 1 (hour)). In the process shown below, the time is represented by the elapsed time from the start of measurement (the first measurement). For example, when the control unit 208 starts a series of measurements, it resets the timer 112, so the current time output by the timer 112 represents the elapsed time from the first measurement.

[0090] The threshold Th is a positive real number, and if the circuit in Figure 9 is pre-adjusted so that the generated voltage measured in the initial state of the silver Ag in the light reflecting section 114 is "130", then for example, Th = 70. The threshold Th is not limited to this value, and any value of about 0.8 to 0.5 times the generated voltage measured in the initial state of the silver Ag is acceptable. The warning message indicates that a reduction in hydrogen sulfide concentration (measures against corrosion by hydrogen sulfide) is necessary.

[0091] In step 400, the control unit 208 obtains the current time from the timer 112 and refers to the measurement time information stored in the memory unit 110 to determine whether or not the measurement time has arrived. If it is determined that the measurement time has arrived, the control proceeds to step 402. Otherwise, the control proceeds to step 412.

[0092] In step 402, the control unit 208 turns on the light-emitting unit 202 and measures the voltage generated at the measurement terminal 134. The measured voltage is stored in the storage unit 110. After that, the control unit 208 turns off the light-emitting unit 202, and the control proceeds to step 404. Step 402 is executed repeatedly, so a series of time-series data is stored in the storage unit 110 by storing the measured voltages in the order they were measured. Note that it is not necessary to store all the data from the start of measurement; it is sufficient to store data for at least the period necessary to remove singularities in the storage unit 110.

[0093] In step 404, the control unit 208 determines whether the singularity can be removed, similar to step 304 (see Figure 4). If it is determined that it can be removed, the control proceeds to step 406. Otherwise, the control proceeds to step 412.

[0094] In step 406, the control unit 208 removes outliers from the series of time-series data measured in step 402, similar to step 306 (see FIG. 4). Thereafter, the control proceeds to step 408. As a result, the time-series data with outliers removed from the time-series data measured in step 402 is stored in the storage unit 110. Let the data (generated voltage) with outliers removed be represented by Y.

[0095] In step 408, the control unit 208 reads out the threshold Th stored in the storage unit 110 and determines whether the data Y determined in the last executed step 406 is greater than or equal to the threshold Th. If it is determined that Y≥Th, the control proceeds to step 412. If Y≥Th, it can be said that the decrease in the generated voltage is relatively small and the corrosion of silver Ag in the light reflection unit 114 has not occurred or is not progressing. Otherwise (Y<Th), the control proceeds to step 410. If Y<Th, since the generated voltage is relatively small, it can be said that the corrosion of silver Ag in the light reflection unit 114 is progressing and the hydrogen sulfide concentration is increasing.

[0096] In step 410, the control unit 208 reads out and presents a warning message from the storage unit 110. As described above, if Y≥Th is not satisfied (Y<Th), since the hydrogen sulfide concentration is increasing, for example, a warning message indicating that it is necessary to reduce the hydrogen sulfide concentration is presented. If the hydrogen sulfide monitoring device 200 includes an acoustic output device or an image display device, the warning message can be presented as sound or an image. Data representing the warning message to be presented may be transmitted from the hydrogen sulfide monitoring device 200 to an external acoustic output device or image display device by wired or wireless communication. As a result, the warning message is presented by the acoustic output device or image display device arranged in the management room or the like.

[0097] In step 412, the control unit 208 determines whether an end instruction has been received. If an end instruction has been received, this program ends. Otherwise, the control returns to step 400 and repeats the above processing. The end instruction is performed, for example, by an operation of turning off the power of the hydrogen sulfide monitoring device 200.

[0098] As a result, in environments where electrical equipment without hydrogen sulfide countermeasures is installed, the system can automatically detect the generation of hydrogen sulfide or an increase in hydrogen sulfide concentration. Therefore, administrators can know when it is necessary to implement hydrogen sulfide countermeasures for installed electrical equipment, take action before performance degradation or malfunction occurs, and properly manage the electrical equipment.

[0099] (Reduction of hydrogen sulfide concentration) When implementing measures against hydrogen sulfide in electrical equipment that has not been protected, an airtight structure is created by using materials to fill gaps in the electrical equipment, and a device to reduce the hydrogen sulfide concentration is placed inside the electrical equipment. Referring to Figure 11, the hydrogen sulfide concentration reduction device 250 includes the hydrogen sulfide monitoring device 200 shown in Figure 8 and the hydrogen sulfide adsorption device 252, and is placed inside the electrical equipment 912. The electrical equipment 912 is, for example, an electrical equipment 910 (see Figure 8) that has been protected against hydrogen sulfide and formed into an airtight structure.

[0100] The hydrogen sulfide adsorption device 252 includes a ventilation fan 254, an adsorbent 256, and a housing 258. The adsorbent 256 is made of a material that adsorbs hydrogen sulfide. The adsorbent 256 is housed in the housing 258. The housing 258 has ventilation holes 260 and 262. The ventilation fan 254 is connected to the ventilation holes 260 of the housing 258. The ventilation fan 254 is, for example, a rotary fan, and the rotation of its blades creates an airflow above the ventilation fan 254. As a result, air is drawn into the housing 258 from the ventilation holes 262, and the drawn-in air is discharged through the ventilation holes 260 and the ventilation fan 254, creating an airflow that moves from bottom to top as indicated by the dotted arrows. When the air drawn into the housing 258 from the ventilation holes 262 passes through the adsorbent 256, the hydrogen sulfide contained therein is adsorbed by the adsorbent 256. The air with reduced hydrogen sulfide concentration is discharged through the vents 260 and the ventilation fan 254. The air discharged from the hydrogen sulfide adsorption device 252 is again drawn in through the vents 262, where hydrogen sulfide is adsorbed by the adsorbent 256, and the air with reduced hydrogen sulfide concentration is discharged. In this way, by circulating the air inside the airtight electrical equipment 912 and passing it through the adsorbent 256 in the housing 258, the hydrogen sulfide concentration inside the electrical equipment 912 can be gradually reduced.

[0101] Various known hydrogen sulfide adsorbents can be used for the adsorbent 256. For example, Colline®, a desulfurization filter manufactured by Okamoto Electric Co., Ltd., can be used. This desulfurization filter is formed by impregnating a corrugated honeycomb substrate with an adsorbent mainly composed of iron oxide. By passing air through the columnar (cylindrical, prismatic) structure formed by stacking multiple substrates, the air can come into contact with the adsorbent over a wider surface area, efficiently adsorbing hydrogen sulfide (generating iron sulfide from iron oxide and hydrogen sulfide) and reducing the concentration of hydrogen sulfide in the air. In addition, iodate-impregnated carbon can be used for the adsorbent 256. For example, Sunplif® Y-SC·O and Starcol® Y-AC·I, iodate-impregnated activated carbons manufactured by Suntex Co., Ltd., may be used. Hydrogen sulfide is oxidized and reacts with moisture in the air, and is adsorbed onto the activated carbon as sulfuric acid.

[0102] After reducing the hydrogen sulfide concentration inside the electrical equipment 912, the hydrogen sulfide is monitored by the hydrogen sulfide monitoring device 200 as described above. That is, by executing the same processing as the flowchart shown in FIG. 10, an increase in the hydrogen sulfide concentration inside the electrical equipment 912 can be detected. In this case, since countermeasures against hydrogen sulfide (adsorption of hydrogen sulfide by the adsorbent 256) have already been taken, a determination of NO (Y < Th) in step 408 means that the adsorption performance of the adsorbent 256 has deteriorated. Therefore, a warning message recommending replacement of the adsorbent 256 and the light reflection part 114 is stored in the storage part 110, and in step 410, the warning message may be read out from the storage part 110 and presented. By replacing the adsorbent 256 with a new one, the hydrogen sulfide concentration inside the electrical equipment 912 can be reduced, and by replacing the light reflection part 114 with a new one, the monitoring of hydrogen sulfide by the hydrogen sulfide monitoring device 200 can be resumed inside the electrical equipment 912.

[0103] The hydrogen sulfide monitoring device 200 has a relatively simple device configuration and can be realized as an inexpensive device. By plating the L-shaped member 116 with silver, the light reflection part 114 can be easily and inexpensively realized.

[0104] By forming the light reflection part 114 in an L shape, the light detection system can be formed compactly. Furthermore, since the light from the light emitting part 202 is incident obliquely on the reflection surface of the light reflection part 114, the area of the portion where the light is reflected can be increased. Since the influence of discoloration of silver Ag in a wider area can be reflected in the generated voltage, the measurement data is stabilized.

[0105] By observing the corrosion of silver (Ag) as a change in light reflectivity (change in generated voltage), the generation of hydrogen sulfide or an increase in hydrogen sulfide concentration can be accurately estimated. Since the measurement result (generated voltage) is an electrical signal, remote monitoring is easily possible. Furthermore, the hydrogen sulfide monitoring device 200 can easily continue monitoring simply by replacing the light reflecting part 114. The warning message presented in step 410 includes a statement that the light reflecting part 114 needs to be replaced, so by replacing the light reflecting part 114, the accuracy of hydrogen sulfide monitoring can be maintained at a high level.

[0106] The above describes a case where the hydrogen sulfide concentration at the installation site is evaluated using EcoChecker II before installing electrical equipment, but it is not limited to this. The method for evaluating the hydrogen sulfide concentration is arbitrary. For example, the presence or absence of hydrogen sulfide may be detected using a device similar to the malfunction risk detection device 100 or the hydrogen sulfide monitoring device 200. The circuit shown in Figure 3 or Figure 9 is placed at the location where the electrical equipment is to be installed, and the generated voltage is measured at predetermined intervals for a predetermined period, and time-series data is acquired. For example, data such as that shown in Figure 13, which will be described later as an example, is acquired. At the start of measurement, the silver Ag of the light reflecting part 114 is in its initial state without corrosion. Let Y(T) be the generated voltage measured during the elapsed time T (in days) from the start of measurement, and the estimated value C (in ppb) of the hydrogen sulfide concentration can be calculated using the following formula. C = -(ΔY / ΔT) / L ···(Equation 1)

[0107] In Equation 1, ΔY(days) is the difference in generated voltage Y between elapsed time T and T-ΔT, i.e., ΔY = Y(T) - Y(T-ΔT), where L is a constant. The graph of generated voltage against the concentration-day product can be approximated by a straight line in the range where the concentration-day product is relatively small, and its slope (corresponding to the coefficient L) is a constant value. Equation 1 is based on this finding. For example, the graphs in Figure 13(a) to (f), described later as examples, decrease linearly from the start of measurement, although this is for a relatively short period. The generated voltage Y can be evaluated as a relative value. For example, if the circuit in Figure 3 or Figure 9 is adjusted so that the value of generated voltage Y measured in the initial state of silver Ag in the light reflecting part 114 is "130", then L = 0.075.

[0108] If the hydrogen sulfide concentration calculated by Equation 1 is less than a predetermined value (e.g., 3 ppb), it is determined that hydrogen sulfide is not present, and the electrical equipment is installed without taking any measures against hydrogen sulfide. Otherwise (if the hydrogen sulfide concentration is 3 ppb or higher), the electrical equipment is installed after taking measures to reduce the hydrogen sulfide concentration, as described above.

[0109] The first to fourth modifications described above with respect to the first embodiment are also possible in the second embodiment. When adopting the configuration of the second modification (see Figure 6), the warning message presented in step 410 of Figure 10 should include a statement that the silver-plated plate 124 needs to be replaced. By replacing the silver-plated plate 124, the accuracy of hydrogen sulfide monitoring can be maintained at a high level.

[0110] (Fifth variation) The above describes the case where hydrogen sulfide concentration is monitored using one threshold value Th, but it is not limited to this. For example, two threshold values ​​may be used, and the flowchart shown in Figure 10 may be modified as shown in Figure 12, for example. The flowchart in Figure 12 is the same as the flowchart in Figure 10, but with steps 408 and 410 replaced by steps 502 and 506, respectively, and steps 500 and 504 added. Therefore, in the following, we will mainly explain steps 500 to 506, which differ from those in Figure 10, without repeating any explanations.

[0111] Here, it is assumed that the hydrogen sulfide monitoring device 200 is located inside electrical equipment that has not been fitted with countermeasures against corrosion caused by hydrogen sulfide. The memory unit 110 of the hydrogen sulfide monitoring device 200 stores measurement time information, upper threshold Th1, lower threshold Th2, first message, and second message. The upper threshold Th1 and lower threshold Th2 are positive real numbers, and Th1 > Th2. The lower threshold Th2 corresponds to the threshold Th mentioned above. If the circuit in Figure 9 is pre-adjusted so that the generated voltage measured in the initial state of the silver Ag of the light reflecting unit 114 is "130", then for example, Th1 = 80 and Th2 = 70 are set. Note that the upper threshold Th1 and lower threshold Th2 are not limited to these values, but are values ​​of about 0.8 to 0.5 times the generated voltage measured in the initial state of the silver Ag, as long as Th1 > Th2 is satisfied.

[0112] The second message corresponds to the warning message described above with respect to Figure 10. That is, the second message is a message informing that a reduction in hydrogen sulfide concentration (measures against corrosion caused by hydrogen sulfide) is necessary. The first message is a cautionary message informing that a reduction in hydrogen sulfide concentration (measures against corrosion caused by hydrogen sulfide) will be necessary in the near future.

[0113] In steps 400 to 404, the control unit 208 lights up the light-emitting unit 202, measures the voltage generated at the measurement terminal 134, and stores the measurement data in the storage unit 110. If it becomes possible to remove the singularity, in step 406, the control unit 208 stores the data Y from which the singularity has been removed in the storage unit 110. Steps 400 to 406 are repeated until a series of time-series data Y from which the singularity has been removed is stored in the storage unit 110.

[0114] In step 500, the control unit 208 reads the upper threshold value Th1 (for example, Th1 = 80) stored in the storage unit 110, and determines whether the data Y determined by the last executed step 406 is greater than or equal to the upper threshold value Th1. If it is determined that Y ≥ Th1, the control proceeds to step 412. If Y ≥ Th1, it can be said that the generated voltage is relatively large and the corrosion of silver Ag in the light reflection unit 114 has not occurred or has hardly progressed. Otherwise (Y < Th1), the control proceeds to step 502.

[0115] In step 502, the control unit 208 reads the lower threshold value Th2 (for example, Th2 = 70) stored in the storage unit 110, and determines whether the data Y determined by the last executed step 406 is greater than or equal to the lower threshold value Th2. That is, since the data Y determined in step 406 has already been determined to be smaller than the upper threshold value Th1 (step 500), it is compared with the smaller lower threshold value Th2. If it is determined that Y ≥ Th2, the control proceeds to step 504. Otherwise (Y < Th2), the control proceeds to step 506.

[0116] In step 504, the control unit 208 reads and presents the first message from the storage unit 110. As a result, a caution message is presented as the first message, informing that it will be necessary to reduce the hydrogen sulfide concentration soon. Thereafter, the control proceeds to step 412. Since the determination result in step 502 is YES (Y ≥ Th2), it can be said that the generated voltage is relatively large and the corrosion of silver Ag in the light reflection unit 114 has not occurred or has not progressed. However, since the determination result in step 500 is NO (Y < Th1) and the generated voltage is approaching the lower threshold value Th2, the above caution message is displayed.

[0117] In step 506, the control unit 208 reads and presents the second message from the storage unit 110. As a result, a warning message is presented as the second message, informing that it is necessary to reduce the hydrogen sulfide concentration. Thereafter, the control proceeds to step 412. If the determination result in step 502 is NO (Y < Th2), it can be said that the generated voltage is relatively small, the corrosion of silver Ag in the light reflection unit 114 progresses, and the hydrogen sulfide concentration is increasing.

[0118] The processes of steps 400 to 406 and steps 500 to 506 are repeated until it is determined that an end instruction has been received in step 412.

[0119] As described above, in an environment where an electrical device without countermeasures against hydrogen sulfide is installed, it is possible to automatically detect the generation of hydrogen sulfide or an increase in the hydrogen sulfide concentration. Before a warning message notifying that countermeasures against corrosion by hydrogen sulfide are necessary is presented, a caution message notifying that it will be necessary to reduce the hydrogen sulfide concentration soon is presented. Therefore, an administrator or the like can make preparations (arrangement of members for an airtight structure and a hydrogen sulfide adsorption device, etc.) for taking countermeasures against hydrogen sulfide for the electrical device. Therefore, when the warning message is presented, countermeasures against hydrogen sulfide can be promptly taken for the electrical device, performance degradation, failure, etc. of the electrical device can be avoided, and the electrical device can be appropriately managed.

[0120] In the fifth modification, regarding the electrical device (see FIG. 11) after a warning message notifying that it is necessary to reduce the hydrogen sulfide concentration is presented and countermeasures against hydrogen sulfide are taken, hydrogen sulfide can be monitored as described above. In that case, the second message is a warning message recommending replacement of the adsorbent and the light reflection unit, and the first message is a caution message notifying that replacement of the adsorbent and the light reflection unit will be necessary soon.

[0121] Determining NO (Y < Th2) in step 502 means that the adsorption performance of the adsorbent 256 has deteriorated. Therefore, in step 506, the control unit 208 reads the second message from the storage unit 110 and presents a warning message recommending replacement of the adsorbent and the light reflection unit.

[0122] If NO (Y < Th1) in step 500 but YES (Y ≥ Th2) in step 502, the adsorption performance of the adsorbent 256 has deteriorated, but not to the extent that immediate replacement of the adsorbent 256 is necessary. Therefore, in step 504, the control unit 208 reads the first message from the storage unit 110 and presents a caution message indicating that replacement of the adsorbent and the light reflection unit will be required soon. Administrators, etc. can arrange for new adsorbents and light reflection units for replacement in advance, and when the warning message is presented, they can promptly replace the adsorbent to reduce hydrogen sulfide and replace the light reflection unit to resume monitoring of hydrogen sulfide.

Example

[0123] The experimental results regarding the first embodiment are shown below to demonstrate the effectiveness of the present invention. Measurements were made in three environments with different hydrogen sulfide concentrations using a defect risk detection device (see Figure 2) employing the optical detection system with the circuit configuration shown in Figure 3.

[0124] The configuration shown in Figure 6 (second modification example) was adopted for the optical detection system. A plurality of silver-plated flat plates placed on the L-shaped member were fabricated. The silver plating was hard and shiny silver plating, formed to a thickness of 3 μm. The purity of silver is approximately 99%. Since it was hard silver plating, it contains trace amounts of additives other than silver. A red LED with a center wavelength of 630 nm was used as the light source. A variable resistor was used as the resistor R1 in the circuit of the optical detection system. In each environment, before starting the experiment, as described above, the value of the resistor R1 was adjusted so that the measured value of the generated voltage (value after AD conversion) would be approximately "130" (error ±3) using the silver-plated plate in the initial state (non-corroded state). <{

[0125] Figures 13(a) to (f) show the results of measurements taken every hour over a period of several months or more. In each graph, the vertical axis represents the generated voltage (relative value), and the horizontal axis represents the measurement date (month and day displayed without year) and the elapsed time (days). One division on the horizontal axis represents approximately 3 months. As mentioned above, the measurement data shown is obtained by removing singularities from time-series data of actual measurements using the moving median of 25 consecutive data points. (a) to (d) are the measurement results from November 19 of a certain year to May 20 of the year after next, and (e) and (f) are the measurement results from September 14 of the following year to May 20 of the year after next.

[0126] To evaluate the variability of the fault risk detection device as a sensor, two fault risk detection devices were placed close to each other in each environment and measurements were taken. Figures 13(a) and (b) show the measurement results of a fault risk detection device placed in an environment with a hydrogen sulfide concentration of 10-15 ppb. Figures 13(c) and (d) show the measurement results of a fault risk detection device placed in an environment with a hydrogen sulfide concentration of 50-200 ppb. Figures 13(e) and (f) show the measurement results of a fault risk detection device placed in an environment with a hydrogen sulfide concentration of 10-50 ppb. The hydrogen sulfide concentration in each environment was measured using EcoChecker II. From the graph in Figure 13, it can be seen that the measurement results of two fault risk detection devices placed in the same environment are similar, while the measurement results of fault risk detection devices placed in different environments are significantly different. Thus, the fault risk detection device can accurately detect fault risks caused by hydrogen sulfide.

[0127] For the measurement data (generated voltage (relative value)) of each environment, the concentration-day product S was calculated as described above, and the measurement data was plotted with the concentration-day product S (ppb·day) on the horizontal axis to generate the graph shown in Figure 14. Graphs (a) to (f) in Figure 14 were generated from the measurement data shown in (a) to (f) in Figure 13, respectively. The number of days used to calculate the concentration-day product S is the number of days elapsed since the start of measurement. The hydrogen sulfide concentration used to calculate the concentration-day product S was measured using EcoChecker II, as described above. Specifically, EcoChecker II was installed in each environment and replaced approximately every month, and the hydrogen sulfide concentration (reference concentration) was obtained from the recovered EcoChecker II. The obtained hydrogen sulfide concentration can be said to be the average hydrogen sulfide concentration during the period in which EcoChecker II was installed. Therefore, in the concentration-day product S, the hydrogen sulfide concentration (reference concentration) obtained from each EcoChecker II was used as the hydrogen sulfide concentration during the period in which that EcoChecker II was installed.

[0128] Regarding the measurement data from the malfunction risk detection devices installed in each environment (Figure 13), the reference time T1, estimated A (risk prediction time), and estimated B obtained by the malfunction risk detection process shown in Figure 4 are shown in Figure 15, with a first threshold K1=8, a second threshold K2=5, and a constant N=5. The date and time and elapsed time are displayed in daily units, rounded from the calculation results for each hour. The measurement environments shown (a) to (f) correspond to (a) to (f) in Figure 13, respectively. The information in the area enclosed by the thick border in Figure 15 indicates the timing when step 320 of the malfunction risk detection process shown in Figure 4 is executed and a message is presented. Values ​​labeled "extrapolated estimates" are values ​​for periods when hydrogen sulfide concentration was not measured, and are calculated assuming that the concentration from the last month (May) when hydrogen sulfide concentration was measured persists thereafter.

[0129] Figures 16 and 17 are Figures 13 and 14, respectively, with the reference time T1, estimated A, and estimated B shown in Figure 15 added. The reference time T1, estimated A, and estimated B are indicated by white circles, with arrows indicating the corresponding notation.

[0130] Regarding Figures 16(a) and (b), Estimate B is determined before Estimate A, which is determined from the reference time T1, is reached, and at the point when Estimate B is determined, a message informing of the risk of malfunction due to hydrogen sulfide is displayed. As can be seen from Figures 17(a) and (b), which correspond to Figures 16(a) and (b), respectively, the concentration-day product in Estimate B is close to 10,000 ppb·day. The specific values ​​of Estimate B are 9,450 ppb·day and 9,318 ppb·day, respectively, as shown in Figures 15(a) and (b). Note that in Figures 16(a) and (b), the measurement was completed before Estimate A was reached, so Estimate A is not shown.

[0131] Regarding Figures 16(c) and (d), Estimate B was determined after Estimate A, which was determined from the reference time T1, had elapsed. Regarding Figures 16(c) and (d), a message informing of the risk of malfunction due to hydrogen sulfide is displayed when Estimate A is determined. As can be seen from Figures 17(c) and (d), which correspond to Figures 16(c) and (d), respectively, the concentration-day product in Estimate A is close to 10,000 ppb·day. The specific values ​​of Estimate A are 7,080 ppb·day and 8,360 ppb·day, respectively, as shown in Figures 15(c) and (d).

[0132] In Figure 16(e), Estimate B is determined before Estimate A, which is determined from the reference time T1, is reached, and at the point where Estimate B is determined, a message informing of the risk of malfunction due to hydrogen sulfide is displayed. In Figure 16(f), Estimate B is not determined by the time the measurement is completed, and the measurement is completed before Estimate A is reached. However, if the measurement is continued, Estimate A will be reached, and at that point, a message informing of the risk of malfunction due to hydrogen sulfide is displayed. As can be seen from Figures 17(e) and (f), which correspond to Figures 16(e) and (f), respectively, the concentration-day product for Estimate B in Figure 16(e) and Estimate A in Figure 16(f) is close to 10,000 ppb·day. Referring to Figures 15(c) and (d), the specific value of Estimate B in Figure 16(e) is 9,102 ppb·day, and the specific value of Estimate A in Figure 16(f) is 11,152 ppb·day.

[0133] Thus, at the earlier of Estimates A and B, the hydrogen sulfide concentration-day product is close to 10,000 ppb·day (approximately 7,000-10,000 ppb·day). Therefore, the earlier of Estimates A and B is achieved is an appropriate time to present the risk of malfunction due to hydrogen sulfide. Furthermore, considering the time required from risk detection to remediation, it is desirable from an operational standpoint to present the risk of malfunction due to hydrogen sulfide before it reaches 10,000 ppb·day. Except for (f) of the six cases described above, the message can be presented before it reaches 10,000 ppb·day, demonstrating that the malfunction risk detection device is effective in operational settings.

[0134] Furthermore, by using the earlier of the two estimations, A and B, the accuracy of risk detection can be improved compared to conventional methods. Considering Figures 13 and 14, the measurement data shown in Figure 13 contains extreme values ​​(maximum and minimum values). For example, it is conceivable to detect the point at which the maximum value occurs (hereinafter referred to as the maximum point) and estimate the point at which the risk is reached (the point at which the concentration-day product is 10,000 ppb-day in each graph of Figure 14). However, there are cases where it is difficult to detect extreme values, such as when there are multiple peaks and valleys in the graph, or when the changes are small. For example, in Figures 13(c) to (f), two maximum points can be seen, and the estimated value of the point at which the risk is reached differs greatly depending on which maximum point is used for judgment. Also, in Figures 13(c) and (d), the concentration change (generated voltage change) is gradual, making it difficult to identify the maximum point. In some cases, a maximum value may occur considerably before the actual malfunction risk occurs, resulting in a false detection. In addition, the process of detecting the maximum point of measurement data generally places a heavy computational load on the measuring device. In contrast, the malfunction risk detection device of the present invention, using computationally intensive processing (see Figure 4), can detect the point at which the risk is reached, whichever is earlier between estimation A and estimation B, in any of the cases (a) to (f) in Figure 13. Furthermore, since it does not use extreme values, it can avoid false detections even when a local maximum occurs considerably before the malfunction risk actually occurs. [Examples]

[0135] The following shows experimental results relating to the second embodiment, demonstrating the effectiveness of the present invention. Figure 18 shows the results of measurements taken in three environments with different hydrogen sulfide concentrations using a hydrogen sulfide monitoring device (see Figure 8) employing a photodetector system with the circuit configuration shown in Figure 9.

[0136] The photodetector adopted the configuration shown in Figure 6 (second modified example). A silver-plated flat plate, mounted on the L-shaped member, was fabricated in the same manner as in Example 1. A red LED with a center wavelength of 630 nm was used as the light source. A variable resistor was used as resistor R1 in the photodetector circuit. In each environment, before starting the experiment, the value of resistor R1 was adjusted as described above using a silver-plated plate in its initial state (corrosion-free state) so that the measured value of the generated voltage (value after AD conversion) was approximately "130" (error ±3).

[0137] Figures 18(a) to (d) show the results of measurements taken every hour over a period of several months or more. In all graphs, the vertical axis represents the generated voltage (relative value), and the horizontal axis represents the measurement date (month and day displayed, year omitted) and the elapsed time (days). One division on the horizontal axis represents approximately 3 months. As mentioned above, the measurement data shown is obtained by removing singularities from time-series data of actual measurements using the moving median of 25 consecutive data points. The hydrogen sulfide concentration in the environment was measured using EcoChecker II.

[0138] Figure 18(a) shows the measurement results of a hydrogen sulfide monitoring device placed in an environment where corrosion due to hydrogen sulfide is not a problem (hydrogen sulfide concentration less than 10 ppb). The measurement period for (a) is from November 19 of a certain year to May 24 of the year after next. Figures (b) and (c) show the measurement results of hydrogen sulfide monitoring devices placed in switchboards installed in different locations, each with measures taken to reduce the hydrogen sulfide concentration as described above. The measurement period for (b) and (c) is from July 9 of the following year to May 20 of the year after next. Figure (d) shows the measurement results of a hydrogen sulfide monitoring device placed in an environment with a hydrogen sulfide concentration of 10-15 ppb. The measurement period for (d) is from November 19 of a certain year to May 20 of the year after next.

[0139] The dashed lines in each graph of Figure 18, representing a generated voltage of 70, correspond to the threshold Th used in the determination in step 408 (see Figure 10) described above. The following can be seen from graphs (a) to (c) in Figure 18. That is, in environments with low hydrogen sulfide concentrations, the generated voltage decreases gradually in the initial stages of measurement (within 3 to 8 months from the start of measurement), and although there is variation depending on the measurement environment, it decreases to about 120 to 110 from the initial value of approximately 130. After the generated voltage decreases to about 120 to 110, the rate of further decrease slows down. The amount of decrease in the generated voltage slows down to about 5 per year, and at most 10 or less, so the generated voltage remains above the dashed line for a long period of time. On the other hand, from graph (d) in Figure 18, in environments where the hydrogen sulfide concentration is 10 to 15 ppb, no slowing of the decrease in generated voltage is observed, and the generated voltage is located below the dashed line in the initial stages of measurement.

[0140] Therefore, in environments where hydrogen sulfide is almost absent, the phenomenon of a slower decrease in the generated voltage can be utilized, and as shown in the second embodiment, changes in hydrogen sulfide concentration can be detected by comparing the generated voltage with a predetermined threshold Th (e.g., Th=70). That is, if the generated voltage is above the threshold Th, it can be confirmed that a state where hydrogen sulfide is almost absent is maintained. If the generated voltage falls below the threshold Th, it can be determined that the hydrogen sulfide concentration is increasing and risks such as corrosion are occurring.

[0141] The threshold Th can be set to a value of, for example, 70-100 (approximately 0.8-0.5 times the generated voltage measured in the initial state of Ag). However, it is not limited to this. Increasing the threshold Th shortens the period during which hydrogen sulfide can be monitored. Decreasing the threshold Th lengthens the period during which hydrogen sulfide can be monitored, but it delays the detection of increases in hydrogen sulfide concentration. Therefore, as mentioned above, the threshold Th should be determined by considering that the rate of decrease in generated voltage slows down after the generated voltage decreases from its initial value of approximately 130 to approximately 110. For example, if Th=70, even if the rate of decrease in generated voltage is 10 / year after the generated voltage decreases from its initial value of 130 to 110, hydrogen sulfide can be monitored for more than 4 years.

[0142] The present invention has been described above by describing embodiments, but the embodiments described above are illustrative, and the present invention is not limited to the embodiments described above. The scope of the present invention is given with reference to the description in the detailed description of the invention, and includes all modifications within the meaning and scope equivalent to the wording contained herein. [Explanation of Symbols]

[0143] 100 Malfunction Risk Detection Device 102, 202 Light-emitting part 104 Power supply section 106, 206 Light detection unit 108, 208 Control Unit 110 Storage section 112 timers 114, 118 Light reflecting part 116 L-shaped member 120, 122 surface 124 Silver-plated plate 126 flat plate 130, 230 LEDs 132, 232 phototransistors 134 Measuring terminals Terminals 140, 142, 144, 146 200 Hydrogen sulfide monitoring device 250 Hydrogen sulfide concentration reduction device 252 Hydrogen sulfide adsorption device 254 Ventilation fan 256 Adsorbent 258 cabinets 260, 262 ventilation holes 900 Printed Circuit Boards 910, 912 Electrical equipment Ag silver R1, R2, R3 resistance

Claims

1. A reflective means with silver arranged on its surface, A light-emitting means for irradiating light onto the silver arranged on the surface of the reflective means, A light detection means for detecting light reflected by the silver arranged on the surface of the reflective means, With light irradiated from the light-emitting means onto the silver arranged on the surface of the reflective means, a measuring terminal that generates a voltage corresponding to the current flowing through the light-detecting means, A measuring means for measuring the voltage of the aforementioned measuring terminal, The system includes a detection means that detects the risk of malfunction occurring due to corrosion by hydrogen sulfide in a printed circuit board arranged around the reflecting means, based on the voltage measured by the measuring means, The time elapsed since the start of voltage measurement by the measuring means when the difference obtained by subtracting the minimum value in the time-series data composed of voltages measured by the measuring means from the voltage measured by the measuring means becomes greater than the first threshold is defined as the reference time, and the time obtained by multiplying the reference time by a real number greater than 1 is defined as the risk prediction time. The detection means detects the risk by determining whether the risk prediction time has elapsed and whether the difference has become smaller than a second threshold that is smaller than the first threshold after the reference time has elapsed. In the initial state of the reflecting means where corrosion due to hydrogen sulfide has not occurred, with the voltage measured by the measuring means being 130, the first threshold value is 5 or more and 15 or less, and the second threshold value is 3 or more and 10 or less. A malfunction risk detection device characterized in that the aforementioned real number is between 4 and 6.

2. It further includes a means for presenting predetermined information, The malfunction risk detection device according to claim 1, characterized in that the presentation means presents information representing the risk when the detection means determines that the difference has become smaller than the second threshold before the risk prediction time has elapsed, or that the risk prediction time has elapsed before the difference becomes smaller than the second threshold.

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