JP6818328B2 - Static electricity measuring device - Google Patents

Description

The present invention relates to an electrostatic measuring device that detects a charging potential of a charged object, an electrostatic electric field based on a charged object, and the like.

Conventionally, an electrostatic measuring device that detects an electrostatic field based on the charging potential of a charged object has been known. The detection principle utilizes the fact that when a detection electrode is opposed to a charged object, an electric charge corresponding to the charging potential of the charged object and the distance to the charged object is induced in the detection electrode.

The charged objects include, for example, silos, powders and droplets floating and flowing in a transport pipe, and the like.
Particle groups such as powders and droplets are likely to be positively or negatively charged due to friction between the particles and friction with the inner wall of a silo or a transport pipe. If the amount of charge due to such friction becomes large, electrostatic discharge may occur. If this discharge is an ignitable discharge, it becomes an ignition source for flammable powder, gas, vapor, etc., and causes an explosion or fire. Therefore, the static electricity measuring device is used for continuously measuring the charged state of particles and the like and monitoring so that the ignitable discharge does not occur.
Therefore, this type of static electricity measuring device has been provided with explosion-proof measures so that it does not cause ignition by itself.

For example, the conventional static electricity measuring device shown in FIG. 5 includes a detection electrode 2 in a tubular casing 1 and responds to the charge induced in the detection electrode 2 based on the charge potential of the charged object 3 outside the casing 1. It is a device that detects the induced current generated.
The detection electrode 2 is an electrode provided with a plurality of fan-shaped plates 2a as shown by a broken line in FIG. 6, and a rotating shaft 4 made of a conductor is attached to a center O1 connecting them. The rotating shaft 4 is connected to the electric motor 6 via an insulating connecting member 5, and the detection electrode 2 is rotated by the driving force of the electric motor 6. The rotating shaft 4 is electrically connected to the detection circuit 7.

Further, the opening 1a of the casing 1 is closed by the ground electrode 8, and the ground electrode 8 is formed with a plurality of slits 8a kept at equal intervals in the rotation direction of the detection electrode 2. Therefore, when the fan-shaped plate 2a of the detection electrode 2 rotates, the detection electrode 2 and the charged object 3 face each other through the slit 8a, or the opposite is blocked.
Further, the rotating shaft 4 made of the conductor is connected to the ground via a detection circuit 7 that detects an induced current. Therefore, the detection circuit 7 can detect the induced current generated according to the electric charge induced in the detection electrode 2.

The reason why the detection electrode 2 and the ground electrode 8 are relatively rotated as described above so that the detection electrode 2 and the charged object 3 face each other through the slit 8a or the opposite is blocked is blocked. The reason is as follows.
In the device as described above, the detection electrode 2 gradually moves toward the slit 8a from the position where the contact electrode 2 is blocked from facing the charged object 3, and the facing area between the charged object 3 and the detection electrode 2 As the value gradually increases, the electric charge in the detection electrode 2 is guided to the surface of the detection electrode 2. For example, as shown in FIG. 7A, when the polarity of the charging potential of the charged object 3 is positive and the detection electrode 2 and the charged object 3 face each other through the slit 8a, the charged object 3 of the detection electrode 2 and the charged object 3 The negative charge in the detection electrode 2 is attracted to the facing surface of the detection electrode 2. When the negative charge is attracted to the charged object 3 in this way, a positive charge equal to the negative charge is induced on the surface on the detection circuit 7 side.

Then, as the facing area between the detection electrode 2 and the charged object 3 increases, the negative charge attracted to the charged object 3 increases accordingly, and as shown in FIG. 7B, the detection electrode 2 has the slit 8a. When the position overlaps with all the openings, the negative charge attracted to the charged object 3 becomes maximum. In this way, in the process of increasing the amount of negative charge attracted to the charged object 3 side, the positive charge induced to the detection circuit 7 side also increases.
Further, in the process in which the detection electrode 2 moves from the state of FIG. 7B and the facing area between the charged object 3 and the detection electrode 2 gradually decreases, the contact with the charged object 3 is blocked by the ground electrode 8. Since the attracted negative charge becomes free, it is neutralized with the positive charge on the detection electrode 7 side. Therefore, as shown in FIG. 7C, the induced charge induced on the surface of the detection electrode 2 is reduced.

Further, when the detection electrode 2 moves and the ground electrode 8 completely blocks the opposition between the detection electrode 2 and the charged object 3, the detection electrode 2 is not affected by the charged object 3 and the induced charge becomes zero.
The change in charge induced on the surface of the detection electrode 2 on the detection circuit 7 side as described above is shown in FIG. FIG. 8 shows the induced charge q induced on the surface of the detection electrode 2 on the side of the detection circuit 7. The induced charge q has a peak value when the facing area between the detection electrode 2 and the charged object 3 is maximum, and a minimum value when the facing area is minimum, and the polarity matches the charging polarity of the charged object 3.

Since the induced charge q flows to the ground via the detection circuit 7, the induced current I based on the induced charge q can be detected by the detection circuit 7. Since this induced current I is the time derivative value of the induced charge q, a phase difference is generated with respect to the change in the induced charge q shown in FIG. 8, for example, the current flowing from the detection electrode 2 to the ground is regarded as a positive current, and the current flows from the ground The signal waveform as shown in FIG. 9 is obtained by using the current flowing through the detection electrode 2 as a negative current.

In this way, the detection circuit 7 can detect the induced current each time the detection electrode 2 and the charged object 3 are opposed to each other through the slit 8a or the opposite is cut off. Then, as the number of detections increases, the detection accuracy can be improved.
The number of detections is determined by the interval in the rotation direction of the slit 8a and the rotation speed of the detection electrode 2. In order to increase the number of detections in this way, the detection electrode 2 and the ground electrode 8 are relatively rotated.

Further, the magnitude of the induced current depends on the facing area between the detection electrode 2 and the charged object 3, that is, the opening area of the slit 8a.
As is clear from the above, the detection accuracy of the induced current depends on the relative rotation speed between the detection electrode 2 and the ground electrode 8 and the opening area of the slit 8a.
Therefore, if the opening area of the slit 8a is small, the detection accuracy of the induced current will be low.
In the above description, the case where the polarity of the charged object 3 is positive has been described, but when the charged object 3 is negative, the direction of the induced current is opposite to the above.

U.S. Pat. No. 8,536,879 Japanese Unexamined Patent Publication No. 2003-021656

Further, in the above-mentioned conventional static electricity measuring device, an electric motor 6 is used as a drive source for relatively rotating the detection electrode 2 and the ground electrode 8, but it is assumed that the electric motor 6 is short-circuited to generate sparks. Explosion-proof measures were taken. That is, the internal pressure of the casing 1 is made higher than the external pressure to prevent external flammable substances from entering the casing 1.
In this way, in order to maintain the internal pressure of the casing 1 high, a high-pressure gas is supplied to the casing 1 from the explosion-proof gas supply source 9. However, even if the explosion-proof gas supply source 9 is provided, the internal pressure cannot be increased if the opening of the slit 8a is large.

In this way, in order to maintain the internal pressure of the casing 1 higher than a certain level, the opening area of the slit 8a has to be reduced in the conventional device. However, as described above, if the opening area of the slit 8a is small, the facing area between the detection electrode 2 and the charged object 3 becomes small, and there is a problem that the detection accuracy becomes low.
Reference numeral 10 in FIG. 5 is a pressure sensor, and reference numeral 12 is a polarity determination circuit for determining the charging polarity of the charged object 3.

The pressure sensor 10 detects the internal pressure of the casing 1 that changes according to the relative position between the slit 8a and the detection electrode 2. When the detection electrode 2 and the charged object 3 face each other via the slit 8a, the slit 8a is blocked by the detection electrode 2, so that the internal pressure of the casing 1 becomes relatively high, and the detection electrode 2 and the charged object 3 are opposed to each other. When the contact with 3 is blocked by the ground electrode 8, the inside and outside of the casing 1 communicate with each other through the slit 8a, so that the internal pressure of the casing 1 becomes relatively low.

From the change in the internal pressure of the casing 1 as described above, it can be determined whether the detection electrode 2 is facing the charged object 3 or the facing is blocked. Therefore, the polarity determination circuit 12 can determine the charge polarity of the charged object 3 based on the detection signal of the pressure sensor 10 and the detection signal from the detection circuit 7.
An object of the present invention is to provide an electrostatic measuring device that can be used in an environment that requires explosion-proof specifications such as a flammable atmosphere and has a high detection sensitivity of an induced current.

The first invention comprises a casing, a detection electrode provided in the casing and outputting an induced current induced according to the charging potential of an opposing charged object, and the detection electrode and the charged object in the casing. An air motor that relatively rotates the ground electrode provided between them, the detection electrode and the ground electrode, a rotation position sensor that detects the relative position between the detection electrode and the ground electrode, and an induction output from the detection electrode. A detection circuit for detecting the current and a polarity determination circuit for specifying the polarity from the signal of the detection circuit and the signal of the rotation position sensor are provided, and the air motor is driven to rotate the detection electrode and the ground electrode relative to each other. In the process of the relative rotation, the facing area between the detection electrode and the charged object is changed at a constant cycle.

Further , an introduction portion for guiding a part or all of the exhaust gas from the air motor into the casing is provided, and an exhaust hole for discharging the exhaust gas guided from the introduction portion is formed around the detection electrode. ..

In the second invention, the detection electrode includes a fan-shaped plate, and the ground electrode includes either a fan-shaped plate having the same shape and the same size as the fan-shaped plate of the detection electrode or a fan-shaped opening, and the detection electrode and the ground electrode In the process of relative rotation with, the total area of the sector plate on the detection electrode becomes the maximum value of the facing area between the detection electrode and the charged object, and the total area of the sector plate of the detection electrode becomes the detection electrode. It keeps the size that is half of the area of the circle drawn by the outer circumference of.
The fan-shaped circle of the detection electrode may be a semicircle, or may be formed by a plurality of fan shapes smaller than the semicircle.
The facing area between the detection electrode and the charged object is maximized when the fan-shaped plate of the detection electrode and the fan-shaped plate of the ground electrode do not overlap, or when the fan-shaped opening of the ground electrode completely overlaps. is there.

According to the first invention, since the air motor is used to rotate the detection electrode and the ground electrode relative to each other, there is no concern that discharge sparks or the like are generated from the air motor. Therefore, it is no longer necessary to maintain the internal pressure of the casing higher than a certain level to realize internal pressure explosion-proof as in the conventional case using an electric motor.
Since it is not necessary to maintain the pressure inside the casing above a certain value in this way, for example, the opening area of the ground electrode is increased, and the facing area where the detection electrode and the charged object face each other through the opening is sufficiently large. can do. If the area facing the charged object becomes large, the induced current value becomes large and the detection sensitivity can be increased.
Moreover, by using an air motor, it is possible to realize an explosion-proof static electricity measuring device simply by making the detection circuit or the like intrinsically safe and explosion-proof, and this device can be used even in an environment requiring explosion-proof specifications.

Further, in the present invention, it is not essential to eject compressed air from the detection electrode side. Therefore, for example, it can be used for measuring the static electricity of charged powder floating in space. If explosion-proof gas is ejected from the casing in order to realize internal pressure explosion-proof, and the gas agitates the powder, the state of static electricity may change and accurate measurement may not be possible. With the measuring device of the invention, there is no such concern.

Further, according to the present invention, since the exhaust gas of the air motor can be guided around the detection electrode, the detection electrode can be cleaned by blowing off foreign matter such as dust adhering to the detection electrode by this exhaust flow. If an insulator adheres to the surface of the detection electrode, the induced current due to the charged object changes and the measurement accuracy deteriorates. In the present invention, the surface of the detection electrode can be kept clean by the exhaust of the air motor, so that the detection accuracy can be maintained.

According to the second invention, the entire surface of the detection electrode can be periodically opposed to the charged object, and the detection sensitivity can be sufficiently increased.

It is a block diagram of the static electricity measuring apparatus of 1st Embodiment of this invention. It is a top view of the detection electrode of 1st Embodiment. It is a top view of the ground electrode of 1st Embodiment. It is a top view of the ground electrode of the 2nd Embodiment. It is a block diagram of the conventional static electricity measuring apparatus. It is a top view of the conventional ground electrode. It is the schematic for demonstrating the detection principle of an induced current. This is an example of a change in induced charge. This is an example of the detected waveform of the induced current.

The first embodiment of the present invention will be described with reference to FIGS. In FIG. 1, the same reference numerals as those in FIG. 5 are used for the same components as in the conventional case, and the description of each is omitted.
In this first embodiment, the detection electrode 13 is fixed to the opening 1a side of the cylindrical casing 1.

As shown in FIG. 2, the detection electrode 13 is composed of four fan-shaped plates 13a having a central angle of 45 °, and although omitted in FIG. 2, the surface of the insulating support plate 14 is grounded as described later. It is kept at equal intervals in the relative rotation direction with the electrode 15. Therefore, the total area of these sector plates 13a occupies half the area of the circle drawn by the outer circumference of the detection electrode 13.
Further, the support plate 14 has a disk shape and its outer circumference is fixed to the inner wall of the casing 1. The support plate 14 may be fixed to the casing 1, and its entire outer circumference need not be in close contact with the inner wall of the casing 1. Further, an opening may be formed in the support plate 14, and the space provided with the air motor 18 and the detection circuit 7 described later communicates with the outside of the casing 1, and foreign matter enters the casing 1. It doesn't matter if something like this happens.

Further, a shaft hole 13b is formed at the center of the detection electrode 13 to which the fan-shaped plate 13a is connected so as to penetrate the rotating shaft 16 attached to the ground electrode 15. A shaft hole 14a corresponding to the shaft hole 13b is formed in the center of the support plate 14, and a bearing member 17 that rotatably supports the rotating shaft 16 is provided in the shaft hole 14a.

Further, a ground electrode 15 located between the detection electrode 13 and the charged object 3 is provided on the opening 1a side of the casing 1.
As shown in FIG. 3, the ground electrode 15 is a metal plate member having an outer shape equal to that of the detection electrode 13. That is, similarly to the detection electrode 13, a plurality of fan-shaped plates 15a are arranged at equal intervals in the rotation direction. The fan-shaped plate 15a has a shape that matches the fan-shaped plate 13a of the detection electrode 13, and a fan-shaped space portion 15b indicated by a one-point chain line is interposed between the fan-shaped plates 15a and 15a adjacent to each other in the rotation direction. The space portion 15b coincides with the fan-shaped plate 15a and the fan-shaped plate 13a of the ground electrode 13.

Further, a conductive rotating shaft 16 is attached to the center O2 of the plurality of fan-shaped plates 15a, and the output shaft of the air motor 18 is connected to the rotating shaft 16 via a connecting member 5. The air motor 18 is connected to a compressed air supply source 19 such as a compressor, and is rotated by the compressed air to rotate the ground electrode 15. The ground electrode 15 is grounded via the rotating shaft 16.

In the static electricity measuring device configured as described above, when the ground electrode 15 rotates, the overlapping area between the fan-shaped plate 15a and the fan-shaped plate 13a of the detection electrode 13 periodically increases or decreases, and the detection electrode 13 and the charged object 3 The facing area will change periodically. Therefore, an induced charge corresponding to the facing area and the charging potential of the charged object 3 is induced on the surface of the detection electrode 13, and the detection circuit 7 detects the dielectric current I based on the induced charge.
Then, when the fan-shaped plate 15a completely overlaps the fan-shaped plate 13a in the rotation process of the ground electrode 15, the facing area between the charged object 3 and the detection electrode 13 becomes zero, and the space portion 15b becomes the fan shape of the detection electrode 13. When it coincides with the plate 13a, the entire area of the sector plate 13a becomes the area facing the charged object 3.
When the space 15b of the ground electrode 15 and the detection electrode 13 overlap in this way, the facing area between the detection electrode 13 and the charged object 3 is maximized, and the amount of induced charge q induced in the detection electrode 13 is maximized. Become.

On the other hand, the induced current I flowing between the detection electrode 13 and the ground is a value obtained by time-differentiating the induced charge q of the detection electrode 13 as described above, so that the change of the induced charge q and the change causing the phase difference are generated. Become. As a result, the peak value of the induced current I is obtained when half of the area of the detection electrode 13 faces the charged object 3 via the space portion 15b of the ground electrode 15, and the peak current value is detected by the detection circuit 7. Will be done. Since the magnitude of the peak value of the induced current I corresponds to the peak value of the induced charge q, the larger the maximum value of the facing area between the detection electrode 13 and the charged object 3, the larger the magnitude. Since the facing area is determined by the size of the space portion 15b of the ground electrode 15, the larger the space portion 15b, the higher the detection sensitivity of the induced current I.

In this first embodiment, the air motor 18 is used to rotate the detection electrode 13 and the ground electrode 15 relative to each other. Therefore, it is not necessary to consider the possibility of sparks of the electric motor 6 as in the conventional case. That is, by using the air motor 18, the drive source that relatively rotates the detection electrode 13 and the ground electrode 15 does not cause ignition, and intrinsically safe explosion-proof can be realized. Therefore, it is not necessary to maintain the internal pressure of the casing 1 higher than a certain level to realize the internal pressure explosion proof as in the conventional case. Since it is not necessary to maintain the internal pressure of the casing 1 high in this way, the opening 1a of the casing 1 does not have to be blocked by the ground electrode 15, and the space 15b is made sufficiently larger than the slit 8a of FIG. be able to.
As a result, the facing area between the detection electrode 13 and the charged object 3 facing each other via the space 15b can be increased, and the detection sensitivity can be increased.

Further, as described above, the polarity of the induced charge q induced toward the detection circuit 7 when the detection electrode 13 faces the charged object 3 matches the polarity of the charged object 3. Therefore, the flow direction of the induced current I detected by the detection circuit 7 differs depending on the charging polarity of the charged object 3. However, the induced current I detected by the detection circuit 7 is both positive and negative as shown in FIG.
Therefore, in order to determine the charging polarity of the charged object 3, it is necessary to detect the process of increasing the facing area between the detection electrode 13 and the charged object 3. This is because the polarity of the induced current I detected in the process of increasing the facing area matches the charging polarity of the charged object 3.
In this first embodiment, the rotation position sensor 20 for detecting the relative rotation position between the ground electrode 15 and the detection electrode 13 is provided, and the detection signal thereof is polarized together with the detection signal of the induced current I from the detection circuit 7. It is input to the determination circuit 12.

The rotation position sensor 20 includes a marker 20a attached to the rotation shaft 16 and a detection unit 20b that detects the position of the rotating marker 20a. For example, when the marker 20a is a permanent magnet and the detection unit 20b is provided with a Hall element, the detection unit 20b detects a magnetic field that changes according to the rotation position of the rotation shaft 16, and the rotation shaft 16 according to the detected value. The rotation angle of can be specified. However, the rotational position sensor 20 may use any principle as long as the positional relationship between the ground electrode 15 and the detection electrode 13 can be grasped.
Then, the polarity determination circuit 12 identifies the rotation position of the ground electrode 15 from the detection signal of the rotation position sensor 20, and the induction detected by the detection circuit 7 in the process of increasing the facing area between the detection electrode 13 and the charged object 3. The polarity of the charged object 3 is determined based on the direction of the current I, that is, the polarity of the detected value, and the result is output to the output unit 11.

Further, in the first embodiment, the exhaust gas of the air motor 18 is ejected to the outside of the casing 1 as shown by the arrow x in FIG. 1, but the exhaust gas may be guided to the casing 1. For example, the exhaust introduction portion may be configured by a pipe or the like as shown by the alternate long and short dash line, or the exhaust port of the air motor 18 may be located in the casing 1.
Then, if the exhaust guided into the casing 1 is discharged from a discharge hole (not shown) provided around the detection electrode 13, the surface of the detection electrode 13 can be cleaned by the exhaust flow.

If dust or the like adheres to the surface of the detection electrode 13, it will not be possible to accurately measure the induced current or the like, but if the detection electrode 13 is kept clean by the exhaust flow, the detection accuracy can be maintained. it can.
The exhaust hole for discharging the exhaust gas guided into the casing 1 from the periphery of the detection electrode 13 may be formed in, for example, the support plate 14 supporting the detection electrode 13, or between the support plate 14 and the inner wall of the casing 1. It may be provided as a gap.

Further, a branch passage may be provided in the introduction portion so that a part of the exhaust gas from the air motor 18 is used as the flow rate for cleaning the detection electrode 13 and the rest is directly ejected to the outside of the casing 1. Further, the branch passage may be provided with a flow rate adjusting means such as a valve for adjusting the exhaust flow rate ejected from the detection electrode 13 side.
For example, in the case of powder in which a charged object flows, if the exhaust flow rate ejected from the detection electrode 13 side is large, the powder is blown off by the ejection pressure of the exhaust, and the detected value such as the induced current changes. However, if the flow rate of the exhaust flow for cleaning the surface of the detection electrode 13 can be adjusted according to the form of the charged object, accurate measurement can always be performed.

FIG. 4 is a plan view of the ground electrode 21 of the second embodiment. In this second embodiment, the ground electrode 15 of the first embodiment is replaced with the ground electrode 21, and other configurations are the same as those of the first embodiment.
The ground electrode 21 has a fan-shaped opening 21a having the same shape and dimensions as each fan-shaped plate 13a of the detection electrode 13 formed around the center 03 of the disk-shaped metal plate. Then, a conductive rotating shaft 16 is attached to the center O3, and the ground electrode 21 is rotated by the air motor 18.

In the ground electrode 21, the fan-shaped closing portion 21b between the openings 21a and 21a adjacent to each other in the rotation direction corresponds to the fan-shaped plate 15a of the ground electrode 15 of the first embodiment. Then, in the relative rotation process between the ground electrode 21 and the detection electrode 13, when the fan-shaped plate 13a of the detection electrode 13 exactly overlaps the fan-shaped opening 21a, the facing area between the detection electrode 13 and the charged object 3 becomes maximum. When the detection electrode 13 and the closed portion 21b are exactly overlapped with each other, the facing area between the detection electrode 13 and the charged object 3 becomes zero. Then, in the process of changing the facing area, the detection circuit 7 detects the induced current I whose flow direction periodically changes according to the change of the induced charge induced on the surface of the detection electrode 13.

Also in this second embodiment, since the air motor 18 is used instead of the electric motor, it is not necessary to maintain the internal pressure of the casing 1 higher than a certain level. Therefore, the area of the fan-shaped opening 21a can be sufficiently increased to increase the detection sensitivity. Moreover, it can be used in an environment that requires explosion-proof specifications.
Further, since the ground electrode 21 of the second embodiment has a disk shape as a whole, the outer circumference is less likely to shake during rotation and is more stable than the one formed by a plurality of fan-shaped plates as in the first embodiment. Can be rotated. If there is no deviation in the rotation of the ground electrode 21, the reproducibility of the detected value becomes higher without causing an error in the area facing the detection electrode 13 and the charged object 3.

In the first and second embodiments, the detection electrode 13 is composed of four fan-shaped plates 13a, and the openings of the ground electrodes 15 and 21 have the same shape as the fan-shaped plate 13a, but the detection electrode 13 and the ground are grounded. If the facing area between the detection electrode 13 and the charged object 3 periodically changes from zero to the maximum value due to the relative rotation with the electrodes 15 and 21, the shape of the detection electrode 13 and the shape of the ground electrodes 15 and 21 And size are not limited.
However, if the shape and dimensions of the space portion 15b of the ground electrode 15 and the fan-shaped opening 21a of the ground electrode 21 match the detection electrode 13, the maximum facing area between the detection electrode 13 and the charged object 3 is defined as the area of the detection electrode 13. It can be made equal, and the entire surface of the detection electrode 13 can be opposed to the charged object 3.

Further, in the detection electrode 13, the total area of the plurality of fan-shaped plates 13a is arranged at equal intervals so as to be half the area of the circle drawn by the outer circumference of the detection electrode 13, so that the detection electrode 13 and the charged object are charged. The facing time with the charged object 3 can be maximized while continuously changing the facing area with 3 from zero to the maximum area. Then, the dielectric current I detected by the detection circuit 7 has a well-balanced waveform as shown in FIG.

Further, in the first and second embodiments, the ground electrodes 15 and 21 are rotated with respect to the fixed detection electrodes 13, but the ground electrodes 15 and 21 are fixed and the detection electrodes 13 are rotated. You may do so. However, when rotating the detection electrode 13, the contact for extracting the induced current I and the rotating shaft 16 must be slid. If the contact portion slides, noise may enter the detection circuit 7. Therefore, it is possible to eliminate the influence of noise and improve the detection accuracy by fixing the detection electrode 13 rather than rotating it.

Further, the detection circuit 7 detects the induced current I induced in the detection electrode 13. In this static electricity measuring device, not only the induced current I but also the induced charge amount induced in the detection electrode and the charged object are charged. It is also possible to measure the charging potential, the amount of surface charge, the electric field strength formed by the charged object 3, and the like.
In the above embodiment, in order to make the measuring device intrinsically safe and explosion-proof, the detection circuit 7 and the polarity determination circuit 12 provided in the casing 1 can be operated with a weak power source, and between the wirings in the circuit. It is designed so that a short circuit does not occur.

It is most suitable as an electrostatic measurement device used in environments that require explosion-proof specifications.

1 Casing 3 Charged object 7 Detection circuit 12 Polarity determination circuit 13 Detection electrode 15 Ground electrode 15b (Opening of ground electrode) Space 18 Air motor 20 Rotational position sensor 21 Ground electrode 21a Opening

Claims (2)

Casing and
A detection electrode provided in the casing and outputting an induced current induced according to the charging potential of the opposing charged object,
In this casing, a ground electrode provided between the detection electrode and the charged object, and
An air motor that relatively rotates the detection electrode and the ground electrode,
A rotation position sensor that detects the relative position between the detection electrode and the ground electrode, and
A detection circuit that detects the induced current output from the detection electrode and
A polarity determination circuit for specifying the polarity from the signal of the detection circuit and the signal of the rotation position sensor is provided.
An electrostatic measuring device that drives the air motor to rotate the detection electrode and the ground electrode relative to each other, and changes the facing area between the detection electrode and the charged object in a fixed cycle in the process of the relative rotation .
An static electricity measuring device in which an introduction portion for guiding a part or all of the exhaust gas from the air motor into the casing is provided, and an exhaust hole for discharging the exhaust gas guided from the introduction portion is formed around the detection electrode. .. The detection electrode has a fan-shaped plate,
The ground electrode is provided with either a fan-shaped plate or a fan-shaped opening having the same shape and dimensions as the fan-shaped plate of the detection electrode.
In the process of relative rotation between the detection electrode and the ground electrode, the total area of the fan-shaped plate in the detection electrode becomes the maximum value of the facing area between the detection electrode and the charged object, and at the same time.
The static electricity measuring device according to claim 1, wherein the total area of the fan-shaped plates of the detection electrodes is halved from the area of the circle drawn by the outer circumference of the detection electrodes .

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