JP7535361B2 - AC voltage source proximity detector - Google Patents

Description

This invention relates to an AC voltage source approach detection voltage detector that issues an alarm when a worker approaches an AC voltage source in order to prevent electric shock accidents or equipment accidents during electrical work such as inspection work or repair work on electrical equipment in buildings and factories, etc.

As shown in Figure 17, a conventional AC voltage source voltage detector uses a human body capacitively coupled to the ground as a reference, and when the electrodes of the voltage detector are brought close to the live part (the object to be measured), the detection circuit of the voltage detector detects a minute current flowing through the capacitance C1 between the live part and the voltage detector, the capacitance C2 between the voltage detector and the operator, and the capacitance C3 between the operator and the ground. If the current is equal to or greater than a certain value, it determines that the object to be measured has a voltage and displays or warns of this fact.

This type of voltage detector has been widely used in the past, and in Patent Document 1, a voltage detector is worn on the wrist with electrodes protruding from the main body of the voltage detector toward the hand tip, and the voltage detector is brought close to the object to be measured to detect voltage. In Patent Document 2, the voltage detector's voltage detection electrode is attached to the handle of a tool, and the worker holds the tool and brings it close to the object to be measured, detecting the voltage of the object and issuing an alarm.

Japanese Patent Application Publication No. 8-220151 Patent No. 6467447

These voltage testers require the worker to hold the tester over the object being measured, or to bring a tool held in hand close to it. In other words, the worker must use the tester correctly, without forgetting to perform voltage testing. Missing either of these steps increases the likelihood of the above-mentioned accidents.

The purpose of this invention is to solve the above-mentioned problems by providing a voltage detector that can alert a worker to the presence of a voltage source nearby, regardless of the worker's awareness, simply by wearing it on the worker's body.

Conventional voltage detectors measure the voltage of an AC voltage source such as an electric wire, and measure the current flowing into the human body which is capacitively coupled to the voltage source. However, the voltage detector of the present invention is significantly different in that it measures the voltage _V02 generated in the human body due to _V0 of the AC voltage source shown in FIG. 2, the capacitance _C01 between the charging part and the human body, and the capacitance _C02 between the human body and the ground, and measures the current flowing out of the human body due to this voltage.

Specifically, the invention of claim 1 is a voltage tester for detecting the approach of an AC voltage source, the detection circuit having a first electrode for measuring the voltage induced in the human body by the approach to the AC voltage source, and a second electrode for measuring the voltage via capacitance to the ground, and a circuit for outputting a signal from the detection circuit when the human body approaches the AC voltage source, the first electrode consisting of a plate having a certain area with a dielectric between it and the human body, and the second electrode having a shape which reduces the vertical projection area relative to the first electrode and increases its area relative to the ground.

The invention of claim 2 is an AC voltage source approach detection voltage detector as described in claim 1, in which the dielectric interposed between the human body is an insulating container that houses the first electrode and the second electrode, and any one of work clothes, a helmet, shoes, and a belt.

Furthermore, the invention of claim 3 is an AC voltage source approach detection voltage detector as described in claim 1 or 2, in which the first electrode is a flat plate and the second electrode is a pole-shaped electrode standing on the flat plate of the first electrode.

The invention of claim 4 is an AC voltage source approach detection voltage detector as described in claim 1 or 2, in which the first electrode is a flat plate and the second electrode is a cylindrical shape standing on the flat plate of the first electrode.

The invention of claim 5 is an AC voltage source approach detection voltage detector as described in any one of claims 1 to 4, in which the first electrode, the second electrode, and the detection circuit are housed in an insulating container.

According to the invention of claim 1, if the voltage detector is attached somewhere on the human body, a signal is output when the worker wearing the voltage detector approaches a voltage source. Therefore, even if a worker forgets to approach a live part during electrical work, etc., it is possible to alert the worker and prevent accidents such as electric shock.

Furthermore, according to the invention of claim 2, the work clothes, helmet, shoes, and belt are all worn by the worker when performing electrical work, and the insulating container containing the first and second electrodes can be attached to any of these items, making it easy for the worker to attach the voltage tester.

According to the third and fourth aspects of the present invention, the voltage generated between the electrodes 1 and 2 becomes large, and the voltage _V02 generated in the human body can be reliably detected.

Furthermore, according to the invention of claim 5, the voltage detector is housed in an insulating container, which is convenient and can be easily attached to the worker.

1 is a diagram illustrating the principle of current flowing through and from a human body when the human body approaches a voltage source; 1 is a schematic diagram showing the principle of a main circuit related to a voltage induced in a human body in accordance with a first embodiment of the present invention; FIG. 1A is a schematic diagram showing the principle of a detection circuit of a voltage detector according to a first embodiment of the present invention, and FIG. FIG. 1A is a front view of the appearance of a voltage detector according to a first embodiment of the present invention, FIG. 1B is a diagram showing the voltage detector attached to a human body, and FIG. FIG. 2 is a perspective view showing an example of the shape of a second electrode of the voltage detector according to the first embodiment of the present invention. FIG. 2 is a comparison table showing a comparison of sensitivity depending on the shape of the second electrode of the electroscope according to the first embodiment of the present invention. 1 is a configuration diagram of a detection circuit of a voltage detector according to a first embodiment of the present invention; FIG. 11 is a schematic vertical cross-sectional view showing an example of a voltage detector according to a second embodiment of the present invention. FIG. 11 is a perspective view showing an example of an electrode of a voltage detector according to a second embodiment of the present invention. FIG. 11 is a schematic vertical sectional view showing another example of the voltage detector according to the second embodiment of the present invention. FIG. 11 is a perspective view showing another example of an electrode of the voltage detector according to the second embodiment of the present invention. 1A and 1B are side views showing a state in which a voltage detector according to a second embodiment of the present invention is attached to a worker's helmet, in which FIG. 1A shows a clip fastening and FIG. 1A and 1B are side views showing a state in which a voltage detector according to a second embodiment of the present invention is attached to a work shoe, in which (a) shows the voltage detector fastened to the heel with a clip, and (b) shows the voltage detector fastened to the toe with a band. FIG. 1 is a table and graph showing the electric field strength measured for each voltage with respect to the distance between the voltage source and the human body. 1 is a graph showing the measurement results of the electric field strength in the space around the human body and head when a live line of 3.3 kV is used as a voltage source. 13 is a table showing the state of an alarm sound measured using a voltage detector according to the second embodiment of the present invention, the state being related to the distance from the human body when a live line of 3.3 kV was used as a voltage source. FIG. 1 is a schematic diagram illustrating the principle of a conventional voltage detector.

(Embodiment Example 1)
First, before explaining the voltage detection method and voltage detector of the first embodiment of the present invention with reference to the drawings, the potential of each part of the human body was measured. Note that in the main circuit of the voltage detector of the first embodiment, a " ₀ " is inserted into V or C to indicate voltage or capacitance, but in the detection circuit, V or C is not displayed with a " ₀ ".

First, we investigated the distribution of electric potential on the human body. To do this, we used an AC potential wireless meter to measure the electric potential at both wrists, both ankles, and the head of a human body that was close to an AC power line, as shown in Figure 1.

The measurement results showed that, naturally, an electric potential was generated in the hand that was extended towards the AC power line, but it was also confirmed that an electric potential was generated in the hand on the opposite side. Furthermore, there were many body positions in which the electric potential was greater on the feet than on the hand that was extended towards the AC power line. This demonstrated that an electric potential is generated throughout the entire human body. It was also discovered that the human body was at an electric potential that was floating above the ground, and that this electric potential differed in different parts of the body.

However, considering that the human body is a conductor of several kΩ and is isolated from AC power lines and the earth by an impedance of several MΩ or more, it is inconceivable that a potential difference of several tens of volts or more that would cause a voltage detector to operate could occur inside the human body.

As a result of the investigation, it was found that the radio AC potential meter was not measuring the electrode potential from the ground, but rather indicating the current level passing through the electrode. Furthermore, while the human body potential was floating above the ground, the human body itself was at the same potential, and the current values flowing through various parts of the body varied depending on the surrounding impedance relationships, and the measurements of the radio AC potential meter changed depending on the current value.

As shown in Figure 1, when a human body H approaches a 100V AC electric wire W, currents _i1 , _i2 , and _i3 flow from the AC electric wire W into the human body H through the arms, torso, and head. This current puts the human body H in a state where it has an AC voltage from the ground G. In this case, it is 30V. Then, due to the electric potential of the human body, currents _i4 , _i5 , _i6 , and _i7 flow through the arms, both legs, and head on the opposite side of the AC electric wire W via the capacitance between the human body H and the ground G.

The current ratio varies greatly depending on the relationship between the AC power line W, the human body H, and the earth G, but in an environment where one hand is brought close to the AC power line W and there is a wall on the other side of the AC power line W, the current values are as shown in Figure 1. _i1 = 0.1 μA, _i2 = 0.2 μA, _i3 = 0.1 μA, _i4 = 0.02 μA, _i5 = 0.18 μA, _i6 = 0.18 μA, _i7 = 0.02 μA. As a result, it is possible to detect a voltage even if the voltage detector is held on the arm opposite the AC power line W, and it is also thought that the foot will have better sensitivity than the arm.

Conventional general voltage detectors are set to detect the current levels _i1 and _i2 from an AC power line when the person approaches the line, and are therefore unable to detect low-level currents such as _i4 and _i7 flowing out of the human body. In addition, because they are based on the model that the human body is equal to the earth potential, they do not utilize the flows of currents _i5 and _i6 , which have relatively large current levels. Note that Figure 1 shows a typical current distribution. In reality, currents are input and output from a much more diverse range of parts of the human body.

In addition, when the human body has poor insulation and is at the same potential as the earth, only the inflow currents _i1 , _i2 , and _i3 can be used, so the human body potential cannot be detected. When a barefoot human body was actually brought to the same potential as the earth, the voltage detector on the opposite side to the AC power line did not react.

In this way, when the human body approaches a voltage source, current flows from the voltage source into the body through the arms, torso, and head, and this current puts the body in a state where it has an AC potential from the ground, and it was found that the body potential causes current to flow through the arms, legs, and head on the opposite side of the voltage source via the capacitance between the body and the ground.

This invention has been made based on this principle. The combined capacitance C0 (series connection of _C01 and C02) of the closed circuit (hereinafter referred to as the main circuit) flowing from the voltage source W through the human body H to the ground G shown in Fig. ₂ is given by the following equations 1 and _2. Note that _V0 is the potential of the voltage source W with respect to the ground G, _V01 is the potential due to the electrostatic capacitance _C01 between the voltage source W and the human body H, and _V02 is the potential due to the electrostatic capacitance _C02 of the human body H with respect to the ground G.

Therefore, equations 3 and 4 are obtained, and it is found that the human body H has a potential (V ₀₂ ) with respect to the ground G.

Furthermore, because of equations 5 and 6, the closer the human body H is to the charging part (the smaller d of _C01 becomes, and _C01 becomes larger), the larger _V02 becomes. As a result, if _V02 can be detected, it can be detected that "a person (human body H) is approaching the charging part."

3(a) is a schematic diagram showing the detection principle of part A in FIG. 2, that is, the voltage detector A of the present invention. This voltage detector A is an armband type that is wrapped around the arm of a human body H, and is composed of a first electrode 1 and a second electrode 2. Here, _C1 is the capacitance between the human body H and the first electrode 1, _C21 is the capacitance between the first electrode 1 and the second electrode 2, _C22 is the capacitance between the human body H and the second electrode 2, _C31 is the capacitance between the first electrode 1 and the ground G, and _C32 is the capacitance between the second electrode 2 and the ground G.

A detection circuit 4 is provided between the first electrode 1 and the second electrode 2. As shown in FIG. 4, the first electrode 1, the second electrode 2, and the detection circuit 4 are attached to the surface of an armband-shaped band 5, and the band 5 can be worn on the worker's arm by male and female hook-and-loop fasteners 5a, 5b provided on the front and back ends, respectively.

The overall combined capacitance of this electroscope A is expected to be expressed by the following formula 7. Moreover, the voltage V _C2 generated between the first electrode 1 and the second electrode 2 is expressed by formula 8. This V _C2 is the voltage that enables detection.

From the above formula 8, if _C1 is increased and _C2 is decreased, V _C2 becomes large, and it is possible to obtain a V _C2 effective for detection. Furthermore, if _C32 is large, an even more effective V _C2 can be obtained. Furthermore, if _C22 is small, it is possible to increase the current flowing through the detection circuit 4, which is advantageous for detection.

Therefore, "S" in C=εS/d is increased and "d" is decreased to increase C1. For this reason, the first electrode 1 is made a flexible electrode having a large area so as to be wrapped around the human body H, and the shape of the electrode in contact with the second electrode 2 is made thin to decrease "S _" in C=εS/d and to decrease _C21 . The first electrode 1 shown in Fig. 4 has electrode plates 1a on both sides in a rectangular shape to increase the area, and the connection portion 1b connecting these electrode plates 1a, 1a is made of a thin, band-like electrode plate to make the whole flexible.

The second electrode 2 has a smaller vertical projection area relative to the first electrode 1, which reduces the "S" and reduces the _C21 . The second electrode 2 has a smaller vertical projection area relative to the human body, which reduces the "S" and reduces the _C22 . The second electrode 2 also has an area (side area) relative to the space (ground), which increases the _C32 . The second electrode 2 shown in FIG. 4 has a cylindrical shape and stands upright on the connection portion 1b of the first electrode 1.

These configurations increase the voltage _Vc2 generated between the first electrode 1 and the second electrode 2, making detection possible. When the first electrode 1 is directly applied to the human body H and in close contact with it, _C1 becomes infinite, and _Vc2 becomes large as shown in the formula 8, improving sensitivity.

The shape of the first electrode 1 is not limited to that shown in FIG. 4. The shape of the second electrode 2 is also not limited to a cylindrical shape. For example, it may be a disk shape as shown in FIG. 5(a), or two semicircular plates crossed in a cross shape as shown in FIG. 5(b). FIG. 5(c) shows the cylindrical second electrode 2. Each of these second electrodes 2 is placed on the connection portion 1b of the first electrode 1 via a substrate 3 made of an insulating material.

Figure 6 shows the distance at which an alarm buzzer sounds when a person wearing each of the detectors A, whose second electrodes 2 are those shown in Figures 5(a), 5(b), and 5(c), approaches a voltage source with a certain voltage from the human body side (the side of the arm not wearing detector A) and when the person approaches the voltage source from the sensor side (the side of the arm wearing detector A).

As a result, it was demonstrated that, among the three types of second electrodes 2, the cylindrical second electrode 2 shown in Figure 5(c) had the best sensitivity.

7, the detection circuit 4 is provided with an amplifier circuit 6 for amplifying the voltage V _C2 generated by the current signal flowing through _C21 between the first electrode 1 and the second electrode 2, and a reference voltage generation circuit 7, and a sound generation circuit 9 and a light display circuit 10 are operated only when a signal is output by a comparison circuit 8 for comparing the output signal of the amplifier circuit 6 with the output signal of the reference voltage generation circuit 7. The detection circuit 4 is provided with a power supply 11, and power is supplied to each circuit by turning on a switch 12 of the power supply 11.

Next, a method for warning the approach of an AC voltage source using the voltage detector A of the present invention will be described.
When a worker wearing the voltage detector A starts working, he or she first turns on the switch 12 of the detection circuit 4. When the worker approaches an AC voltage source, a minute current flows into the worker. This current causes the human body to have a potential of _V02 . The first electrode 1 is divided from the potential _V02 through the capacitance _C1 to a potential _V2 . The voltage of the second electrode 2 is a potential obtained by dividing the current flowing out due to the potential _V2 by _C21 and _C32 . The detection circuit 4 detects the potential difference _VC2 across the capacitance _C21 caused by this outflow current i, and if the output signal obtained by amplifying the potential difference _VC2 across the capacitance _C21 caused by the outflow current i is greater than the reference voltage, an alarm is generated from the sound generation circuit 9 and the light display circuit 10 is turned on. This tells the worker wearing the voltage detector A that he or she is approaching an AC voltage source. Even if the operator turns on the switch 12, the sound generating circuit 9 and the light display circuit 10 will not operate unless the operator approaches an AC voltage source.

In the above embodiment 1, the voltage detector A is in the form of an armband, but this is not limiting and any part of the human body may be worn on the head, neck, torso, legs, upper body, or lower body. In the above embodiment 1, the voltage detector A is attached to an armband-shaped band 5, but this is not limiting and the voltage detector may be configured such that only the first electrode 1 is wrapped around the human body, the first electrode 1 and the second electrode 2 are separated, and the second electrode 2 is attached separately to another part of the human body. In addition, the first electrode 1 is a flexible flat plate, but this is not limiting and any conductor such as a braided conductor may be used.

(Embodiment 2)
Next, a voltage detector B according to a second embodiment of the present invention will be described with reference to FIGS.

In the first embodiment, the first electrode 1 is a flexible electrode having a large area so as to be wrapped around the human body H, and the shape of the electrode in contact with the second electrode 2 is made thin to reduce "S" in C=εS/d and to reduce the above-mentioned _C21 . However, it has been found that voltage detection is possible based on the above-mentioned principle even when the first electrode is not in close contact with the human body H. This is the second embodiment.

As shown in Figures 8 and 9, one example of the voltage detector B in embodiment 2 has a first electrode 16 made of a disk housed inside a box-shaped insulating case 15, a rod-shaped second electrode 17 is provided vertically in the center of one side of the first electrode 16, and a detection circuit 4, the same as in embodiment 1, is provided between the first and second electrodes. Also, a clip 15a is provided on the side of the insulating case 15.

In another example of the voltage detector B in the second embodiment, as shown in Figures 10 and 11, a first electrode 18 made of a disk is stored inside a box-shaped insulating case 15, a second electrode 19 in the shape of a cylinder is provided vertically in the center of one side of the first electrode 18, and a detection circuit 4 similar to that in the first embodiment is provided between the first and second electrodes. Also, a clip 15a is provided on the side of the insulating case 15.

As shown in Fig. 12(a), the insulating case 15 of this voltage detector B is attached to the rear of the work helmet 20 by a clip 15a. The clip 15a in Fig. 12(a) is slightly different from the clips in Figs. 8 and 10, but has the same gripping function. As shown in Fig. 12(b), the insulating case 15 may be attached to the work helmet 20 by a band 21. As shown in Fig. 13(a), the insulating case 15 may also be attached to the heel of a work shoe 22 by a clip 15a. As shown in Fig. 13(b), the insulating case 15 may also be attached to the instep of the toe of the work shoe 22 by a band 23.

In this way, the first electrode 16 or 18 is attached to the human body H via the helmet 20, work shoes 22, and insulating case 15, which are dielectric materials, and when the human body H approaches the voltage source W, a minute current flows into the human body H, who is the worker. Thus, although the electrostatic capacitance _C1 between the human body H and the first electrode 16 or 18 is smaller than that in the first embodiment, a current is generated between the first electrode 16 or 18 and the second electrode 17 or 19, which is detected by the detection circuit 14 and an alarm is issued.

Below, a demonstration test was conducted on voltage detector B.
First, the distance and electric field strength were measured for each voltage of the AC voltage source.

The electric field strength was measured using a digital electromagnetic wave meter (GM3120). The human body charge was measured by pressing the electrode part against the body to measure the electric field strength. The GND of the meter was also connected to the GND by a cable.

Figure 14 shows the results of the measurement in a table and graph that show the electric field strength values for each voltage and the distance between the voltage source and the human body. Looking at these, when the AC voltage source is 1 kV, 96 V/m was measured when the distance between the voltage source and the human body was 110 cm, and 240 V/m was measured when the AC voltage source was 3 kV. This shows that an electric field strength of 96 V/m can be detected at a distance of about 1 m for a voltage source of 1 kV or more.

Next, Figure 15 shows the results of measuring the electric field strength in the space around the human body and head when the AC voltage source is a live 3 kV line. Figure 16 shows the results when the voltage detector B is attached to the rear of the helmet, and measures how the alarm sound operates depending on the shape of the first and second electrodes and the distance from the 3 kV power source.

In FIG. 16, "sensor side electrode" refers to the second electrode, and "human body side electrode" refers to the first electrode. "Forward approach" refers to when a human body approaches a live line facing forward, and "backward approach" refers to when the human body approaches a live line facing backward. "Short series" means that the sound is almost continuous, "Short 4" means that the alarm sounds four times in 10 seconds, "Short 10" means that the alarm sounds 10 times in 10 seconds, and "Short 30" means that the alarm sounds 30 times in 10 seconds. Therefore, "Short 4" means that the electric field strength is weak, and "Short series" means that the electric field strength is strong.

From this table, the second electrode number 3, which is a rod-shaped electrode with a length of 10 mm, and the first electrode, which is a square plate-shaped electrode with a diameter of 60 x 30 mm, will sound an alarm 5 times every 10 seconds at a distance of 110 cm in the case of a "forward approach," and will sound an alarm 5 times every 10 seconds at a distance of 210 cm in the case of a "reverse approach." Also, the second electrode number 1, which is a rod-shaped electrode with a length of 20 mm, and the first electrode, which is a disk-shaped electrode with a diameter of 40 mm, will sound an alarm "short 30" at a distance of 70 cm in the case of a "forward approach," and will sound an alarm "short 4" at a distance of 230 cm in the case of a "reverse approach."

In addition, for the number 2, where the second electrode is a cylinder with a diameter of 35 mm and a height of 7 mm, and the first electrode is a disk-shaped electrode with a diameter of 40 mm, the alarm will sound a "short 21" at a distance of 190 cm even in a "forward approach," and a "short 15" at a distance of 330 cm in a "reverse approach." In addition, for the number 4, where the second electrode is a rod-shaped electrode with a length of 10 mm, and the first electrode is a disk-shaped electrode with a diameter of 40 mm, the alarm will sound a "short 27" at a distance of 190 cm even in a "forward approach," and a "short 4" at a distance of 330 cm in a "reverse approach."

In this way, if the AC power supply is 1000V or more, preferably 3000V or more, the voltage detector will function satisfactorily even if the first electrode is not in close contact with the human body and is placed through a dielectric such as a helmet or an insulating case for the detector. If the first electrode is placed in close contact with the human body, there is a risk that detection will become unreliable due to the effects of sweat, etc., but if the electrode is placed through a dielectric like this, it will not be affected by sweat, etc.

However, based on the results of the table in Figure 16 above, when using the voltage detector in question in electrical work, voltage detectors with configurations 3, 2, and 4, which start to sound an alarm 100 cm away from the power source, are practical.

In the above-mentioned first and second embodiments, the voltage detector A or B is provided with a sound generating circuit 9 and a light display circuit 10, but it is also possible to configure the voltage detector A or B without providing these circuits, so that the output from the comparison circuit 8 is received by a transmitter (not shown) and a signal is wirelessly transmitted to the outside, which is then received by a communication device or terminal device provided separately from the voltage detector A, and an alarm or display is issued by that device.

The above describes embodiment examples 1 and 2, but these are presented as examples and are not intended to limit the scope of the invention. This invention can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, as well as in the scope of the invention and its equivalents described in the claims.

A Voltage detector B Voltage detector G Earth H Human body W Voltage source
REFERENCE SIGNS LIST 1 First electrode 1a Electrode plate 1b Connection portion 2 Second electrode 3 Substrate 4 Detection circuit
5 Belt 5a Hook-and-loop fastener 5b Hook-and-loop fastener 6 Amplification circuit 7 Reference current generating circuit 8 Comparison circuit 8 Sound generating circuit 9 Lighting display circuit 11 Power supply 12 Switch 15 Insulating case 15a Clip 16 First electrode 17 Second electrode 18 First electrode 19 Second electrode 20 Helmet 21 Band 22 Work shoes 23 Band

Claims (5)

1. A voltage detector for detecting the approach of an AC voltage source, comprising: a detection circuit having a first electrode for measuring a voltage induced in a human body due to approach to the AC voltage source; and a second electrode for measuring a voltage via electrostatic capacitance to the ground; and a circuit for outputting a signal from said detection circuit when a human body approaches said AC voltage source, said first electrode consisting of a plate having a certain area with a dielectric between it and the human body, and said second electrode having a shape which reduces its vertical projection area relative to the first electrode and increases its area relative to the ground. The AC voltage source approach detection voltage detector according to claim 1, characterized in that the dielectric material interposed between the human body is an insulating container that houses the first electrode and the second electrode, and any one of work clothes, a helmet, shoes, and a belt. The AC voltage source approach detection voltage detector according to claim 1 or 2, characterized in that the first electrode is a flat plate, and the second electrode is a pole-shaped electrode standing on the flat plate of the first electrode. The AC voltage source approach detection voltage detector according to claim 1 or 2, characterized in that the first electrode is a flat plate and the second electrode is a cylindrical shape standing on the flat plate of the first electrode. 5. The AC voltage source approach detection voltage detector according to claim 1, wherein the first electrode, the second electrode and the detection circuit are housed in an insulating container.

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