CN116165453A

CN116165453A - Surface charge measuring device

Info

Publication number: CN116165453A
Application number: CN202310440299.1A
Authority: CN
Inventors: 汪沨; 胡德雄; 宋兴硕; 钟理鹏; 陈赦
Original assignee: Hunan University
Current assignee: Hunan University
Priority date: 2023-04-23
Filing date: 2023-04-23
Publication date: 2023-05-26
Anticipated expiration: 2043-04-23
Also published as: CN116165453B

Abstract

The invention provides a surface charge measuring device, which comprises a metal shielding cover, a metal probe arranged in the metal shielding cover, and a discharging device for resetting initial charge of the metal probe, wherein the discharging device comprises a driving device and a wire, the wire is arranged in the metal shielding cover and is grounded, the driving device drives the wire to switch between a first position and a second position, the first position is in a state that the wire is not contacted with the metal probe, and the second position is in a state that the wire is contacted with the metal probe. The surface charge measuring device is suitable for experiments for measuring the surface charge of the insulating material in special occasions such as electrification and non-electrification, the metal probe adopts an automatic electricity leakage mode, the influence of a self-electrification field of a human body is avoided, the initial charge clearing effect of the metal probe is improved, and the reliability and the accuracy of the surface charge measurement are further improved.

Description

Surface charge measuring device

Technical Field

The invention belongs to the technical field of electrostatic measurement, and particularly relates to a surface charge measurement device.

Background

The surface charge measurement technique includes a dust pattern method, a Pockels electro-optical effect method, a capacitance probe method, an electrostatic capacitance probe method, and the like. The electrostatic capacitance probe used in the electrostatic capacitance probe method has the advantages of simple structure, good stability, capability of detecting some insulating materials with complex surface shapes, and the like, and is widely used. In measuring the surface charge of a solid insulating material, the surface charge density is typically obtained by applying a surface potential induced on a capacitance probe after the applied voltage is removed. Before measurement, the metal probe used for measuring the surface potential in the electrostatic capacitance probe can sense positive and negative ions in the air so that the metal probe has a certain voltage initial value. And at the next measurement, the initial voltage of the metal probe is the final voltage value after the previous measurement. The voltage on the metal probe is not zero, which affects the real surface potential of the measured insulating material, and the electrometer chip may be damaged due to exceeding the measuring range.

In general, the method for clearing the initial charge of the metal probe in the capacitance probe is to first make a grounding wire 8 closely contact with the tip of the metal probe 5 to drain the current, so that the initial potential of the metal probe 5 is zero, and then measure the surface potential of the insulating material 2, as shown in fig. 8. However, since the human body itself has static electricity, the amount of static electricity is larger especially in a dry environment, and electrostatic discharge may have an electromagnetic field around the human body. Since the vertical distance between the metal probe tip and the sample to be measured is very short, it is usually only about 3 mm. When a person holds the grounding wire close to the tip of the metal probe, the electrostatic field of the human body can influence the actual surface potential distribution condition of the sample to be measured, and the situation that the grounding wire is in false contact with the surface of the sample to be measured can possibly occur, so that the reliability and the accuracy of surface charge measurement are greatly influenced.

Meanwhile, a direct current power supply and a power switch for supplying power to the electrometer chip are usually packaged in a metal shielding cover, if the surface charge measurement is required, the metal shielding cover must be opened, the power supply switch must be manually turned on, and after the experiment is completed, the metal shielding cover must be opened again, and the power supply must be manually turned off. Such a capacitance probe can be used only in the case where the insulating material is not electrically measured, and thus has a very limited application. The requirements on the power supply reliability are high, and the electrified overhaul becomes a normalization, so that the development of the electrostatic capacitance probe suitable for electrified measurement and non-electrified measurement is significant.

Disclosure of Invention

The invention aims to solve the technical problem of overcoming the defects of the prior art and providing a surface charge measuring device which is convenient for clearing initial charge of a metal probe and has no limitation on application occasions.

The technical problems are solved, and the specific technical scheme of the invention is as follows:

the utility model provides a surface charge measuring device, this device includes the metal shield cover and sets up the metal probe in the metal shield cover is inside, still includes the electric installation that lets out that is used for letting out the initial charge of metal probe clear, let out electric installation including drive arrangement and wire, the wire setting is inside the metal shield cover just the wire is connected with the ground connection, drive arrangement drive wire switches between first position and second position, first position is the state that wire and metal probe do not contact, the second position is the state that wire and metal probe contact.

Therefore, by arranging the electricity leakage device in the metal shielding cover, the lead is preferably a copper bare lead, and the grounded lead is driven to contact with the metal probe during use, so that the aim of clearing initial charge of the metal probe is fulfilled, the metal probe avoids the influence of the electrostatic field of a human body on the actual surface potential distribution condition of a sample to be tested by the way of automatic electricity leakage, and the effect of clearing the initial charge of the metal probe is obvious.

Further, the electricity leakage device further comprises a guide rail arranged in the metal shielding cover, the guide wire is in sliding connection with the guide rail, a limiting device used for limiting the moving range of the guide wire is arranged on the guide rail, and the damage of the electricity leakage device or the metal probe caused by excessive movement of the guide wire can be prevented by arranging the limiting device.

Still further, drive arrangement is including setting up the outside motor of metal shield, the guide rail is for setting up the lead screw in metal probe both sides, the both ends of wire pass through the nut with the lead screw is connected, lead screw one end stretches out the metal shield is rotatory through motor drive, if install step motor or utilize wireless emitter to control the operation of letting out electric installation in the metal shield, electromagnetic interference can seriously influence the normal operating of electrometer chip to lead to the measuring result of surface charge inaccurate. The pure mechanical structure is arranged in the metal shielding cover, and any electronic component is not additionally arranged; the screw rod is penetrated through the rotatable mechanical metal knob which is arranged on the metal shielding cover, a stepping motor and other automatic control systems are arranged outside the metal shielding cover, and the stepping motor is connected with a screw rod guide rail in the electricity leakage device through the rotatable mechanical metal knob, so that the function of controlling the operation of the electricity leakage device inside the metal shielding cover from the outside of the metal shielding cover is achieved. Finally, the function of automatically discharging the electricity to the metal probe can be realized under the condition that the normal operation of the electrometer chip is not influenced.

Further, the guide rail is a movable channel arranged at two sides of the metal probe, two ends of the wire are in sliding connection with the movable channel through fasteners, one end of the movable channel is provided with a spring matched with the fasteners, when the wire is in a first position, the spring is in a free state, and when the wire is in a second position, the spring is in a compressed state; the driving device comprises a motor arranged outside the metal shielding cover and a rotating shaft extending into the metal shielding cover, the rotating shaft is connected with the fastening piece through a connecting rope, when the lead moves to the second position, the motor drives the rotating shaft to rotate so as to tighten the connecting rope, and the connecting rope pulls the fastening piece to move in the movable channel and compress the spring; when the lead moves to the first position, the motor drives the rotating shaft to rotate so as to loosen the connecting rope, and the spring restores the natural state and drives the fastener to move in the movable channel. The metal shielding cover is provided with a pure mechanical structure, no electronic components are additionally arranged, and the outside of the metal shielding cover is provided with a stepping motor and other automatic control systems; the rotatable rotating shaft is arranged on the metal shielding cover, the stepping motor is connected with the rotating shaft, the bearing pulley is arranged on the rotating shaft, and the rotating shaft and the copper bare conductor are connected together to move together through the fixed pulley, so that the function of controlling the operation of the electric leakage device in the metal shielding cover from the outside of the metal shielding cover is achieved.

In addition, a surface charge detection module is arranged in the metal shielding case, the surface charge detection module comprises a power supply module and an electrometer, the power supply module provides power for the electrometer, and the electrometer is electrically connected with the metal probe; the wire is provided with a deflector rod matched with the power switch of the power supply module, when the wire moves from the first position to the second position, the deflector rod turns on the power switch, and when the wire moves from the second position to the first position, the deflector rod turns off the power switch. By the mode, when the electrostatic meter chip is used, the metal shielding cover does not need to be opened for manual power supply, and the function of automatically discharging the metal probe can be realized under the condition that the normal operation of the electrostatic meter chip is not influenced. Therefore, the surface charge measuring device provided by the invention is suitable for experiments for measuring the surface charge of the insulating material in specific occasions such as electrification and non-electrification.

The surface charge measuring device has the following advantages: the surface charge measuring device is not limited by application occasions, the metal probe adopts an automatic discharging mode, the influence of a self-contained electrostatic field of a human body is avoided, the effect of zero clearing of initial charge of the metal probe is improved, and further the reliability and accuracy of surface charge measurement are improved.

Drawings

FIG. 1 is a schematic diagram of a surface charge measurement device according to the present invention;

FIG. 2 is a schematic structural view of a first embodiment of the present invention;

FIG. 3 is a schematic diagram of a second embodiment of the present invention;

FIG. 4 is a schematic diagram of a connection line of a surface charge detection module according to the present invention;

FIG. 5 is a graph comparing the surface charge measurements of different devices;

figure 6 is a graph of the results of a conventional capacitance probe;

figure 7 is a graph of the results of a capacitance probe with a bleed structure;

fig. 8 is a schematic diagram of a conventional surface charge measurement device.

The figure indicates: 1. a grounded metal plate; 2. an insulating material to be tested; 3. a metal shield; 4. polytetrafluoroethylene; 5. a metal probe; 6. a data acquisition device; 7. a discharging device; 8. a ground wire; 9. a surface charge detection module; 10. a power supply module; 11. an electrometer; 12. a power switch; 20. a plastic base; 21. a plastic connector; 71. a driving device; 72. a wire; 73. a deflector rod; 74. a guide rail; 741. a screw rod; 742. a movable channel; 75. a limiting device; 76. a nut; 77. a fastener; 78. a spring; 79. a motor; 80. a rotating shaft; 81. a connecting rope; 82. a bearing pulley; 83. a fixed pulley; 84. a conveyor belt; 85. an upper computer; 86. a metal knob; 87. a connecting rod; 88. a driver.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings for a better understanding of the objects, structures and functions of the present invention.

As shown in fig. 1 to 3, a surface charge measuring device of the present embodiment includes a metal shielding case 3, a metal probe 5 disposed inside the metal shielding case 3, a discharging device 7 for clearing an initial charge of the metal probe 5, and a surface charge detecting module 9, wherein the discharging device 7 includes a driving device 71, a wire 72, and a guide rail 74 disposed inside the metal shielding case 3, the wire 72 is disposed inside the metal shielding case 3, and the wire 72 is connected to a ground terminal, the driving device 71 drives the wire 72 to switch between a first position and a second position, the first position is a state in which the wire 72 is not in contact with the metal probe 5, and the second position is a state in which the wire 72 is in contact with the metal probe 5. The discharging device 7 further comprises a wire 72 slidably connected to a guide rail 74, and a limiting device 75 for limiting the movable range of the wire 72 is arranged on the guide rail 74. The surface charge detection module 9 comprises a power supply module 10 and an electrometer 11, wherein the power supply module 10 provides power for the electrometer 11, and the electrometer 11 is electrically connected with the metal probe 5. The wire 72 is provided with a lever 73 for cooperating with the power switch 12 of the power supply module 10, and when the wire 72 is moved from the first position to the second position, the lever 73 turns on the power switch 12, and when the wire 72 is moved from the second position to the first position, the lever 73 turns off the power switch 12.

The traditional electrostatic capacitance probe used in the prior art has certain limitation due to the structure, so that when the surface potential of the insulating material is measured, the ground wire is in contact with the tip of the metal probe manually, and the measurement can be started after the initial potential of the metal probe is zero. However, the human body has an electrostatic field, when the handheld ground wire is close to the tip of the metal probe, the hand is very close to the surface of the sample to be detected, and the electrostatic field of the human body can influence the actual distribution condition of the surface potential of the sample to be detected.

On the other hand, the static meter chip adopted by the traditional static capacitance probe is very sensitive, the input bias current can be as low as 20fA, and the static capacitance probe is easily influenced by electromagnetic interference generated by surrounding electric facilities and electric equipment on the measurement result. In experiments, the learner found that when the shielding measures were problematic, for example, the holes for wiring on the metal shield were not sealed, and as a result, some more pronounced clutter was found on the oscilloscope for data acquisition. When complete metal shielding is achieved, the clutter disappears. The actual shielding effect of the metal shielding box in the electrostatic capacity probe can be judged through the presence or absence of clutter on the oscilloscope.

As shown in fig. 1 and 2, as a first embodiment of the present invention, the driving device 71 includes a motor 79 provided outside the metal shield 3, the guide rail 74 is a screw 741 provided at both sides of the metal probe 5, both ends of the wire 72 are connected to the screw 741 through nuts 76, and one end of the screw 741 protrudes out of the metal shield 3 and is driven to rotate by the motor 79.

The mounting method of the first embodiment of the present invention includes the steps of:

step one: the plastic base 20 is fixed to the metal shield 3 by bolts with the metal probe 5 as a center point.

Step two: screw rods 741 are mounted on the plastic base 20, and a nut 76 is respectively mounted on each screw rod 741, wherein the nuts 76 are preferably metal round tables, and the upper ends of the two metal round tables are connected by a plastic connecting piece 21 to form a screw rod sliding table structure. The lower ends of the two metal round tables are fixedly provided with a copper bare wire, and the copper bare wire is connected with the grounding end.

Step three: the mechanical metal knob 86 is preferably installed on the corresponding metal shielding box under the screw rod sliding table, a connecting rod 87 penetrates through the metal knob 86, one end of the connecting rod 87 is connected with one end of the screw rod 741, the other end of the connecting rod 87 is connected with the motor 79 outside the metal shielding cover 3, and the motor 79 is also connected with the mechanical metal knob 86. The host computer 85 may be programmed with a driver 88, the driver 88 controlling the movement of the motor 79.

Step four: and the limiting device 75 is arranged on the screw rod sliding table at the first position and the second position, and the limiting device 75 is preferably polytetrafluoroethylene blocks. The purpose is in order to when the metal round platform moves to the second position department, motor 79 stop operation to the condition such as the naked wire of drive copper when having avoided motor 79 to continue to operate makes metal probe 5 atress and takes place the offset. The motor 79 rotates reversely after stopping running, the bare copper wire is driven to move to the first position, and when the metal round table touches the polytetrafluoroethylene block, the motor 79 stops running at the moment, and the whole process of discharging the electricity to the metal probe is finished.

The method for measuring surface charge by adopting the first embodiment of the invention comprises the following steps:

step one: before measurement, preparing a sample to be measured, namely a silicon rubber material, wherein the diameter of the sample to be measured is 10cm, the thickness of the sample to be measured is 2mm, firstly, washing the surface of the sample with absolute ethyl alcohol, and then, eliminating static electricity on the surface of the silicon rubber by using a static electricity eliminating ion fan, so that the potential of the surface of the silicon rubber tends to be zero.

Step two: the driver 88 is controlled by the upper computer 85, so that the motor 79 drives the metal round table and the copper bare conductor on the metal round table to move towards the direction of the metal probe 5.

Step three: when the metal round table touches the polytetrafluoroethylene block, the motor 79 stops running for 3s, so that the copper bare conductor is tightly contacted with the metal probe 5 to discharge electricity. Then the motor 79 is reversed to drive the metal round platform to move in the opposite direction of the metal probe 5, when the metal round platform touches the polytetrafluoroethylene block, the motor 79 stops running at the moment, and the whole process of discharging the electricity to the metal probe 5 is finished.

Step four: and starting a measurement experiment of the surface charge of the sample to be measured.

The technical difficulties of this embodiment are embodied in: if a stepping motor is installed in the metal shielding box or a wireless transmitting device is used for controlling the operation of the electricity discharging device, electromagnetic interference can seriously influence the normal operation of the electrometer chip, so that the measurement result of the surface charge is inaccurate. The idea adopted by the embodiment is as follows: the metal shielding box is provided with a pure mechanical structure, and no electronic component is additionally arranged. The rotatable mechanical metal knob 86 is arranged on the metal shielding box, some automatic control systems such as a stepping motor are arranged outside the metal shielding box, and the stepping motor is connected with a lead screw guide rail in the electricity leakage device through the rotatable mechanical metal knob 86, so that the function of controlling the operation of the electricity leakage device inside the metal shielding box from the outside of the metal shielding box is achieved. Finally, the function of automatically discharging the electricity to the metal probe can be realized under the condition that the normal operation of the electrometer chip is not influenced.

As shown in fig. 1 and 3, as a second embodiment of the present invention, the guide rail 74 is a movable channel 742 provided at both sides of the metal probe 5, both ends of the wire 72 are slidably connected to the movable channel 742 by a fastener 77, one end of the movable channel 742 is provided with a spring 78 engaged with the fastener 77, the spring 78 is in a free state when the wire 72 is in the first position, and the spring 78 is in a compressed state when the wire 72 is in the second position. The driving device 71 comprises a motor 79 arranged outside the metal shielding case 3 and a rotating shaft 80 extending into the metal shielding case 3, wherein the rotating shaft 80 is connected with the fastening piece 77 through a connecting rope 81, when the wire 72 moves to the second position, the motor 79 drives the rotating shaft 80 to rotate to tighten the connecting rope 81, and the connecting rope 81 pulls the fastening piece 77 to move in the movable channel 742 and compress the spring 78. When the wire 72 is moved to the first position, the motor 79 drives the shaft 80 to rotate to release the connecting cord 81, preferably nylon cord, and the spring 78 resumes its natural state and moves the fastener 77 within the movable channel 742.

The installation method of the second embodiment of the present invention includes the steps of:

step one: the movable channels 742 are respectively arranged on the left side and the right side of the metal probe in the metal shielding cover 3, the movable channels 742 are bridge-cut aluminum base, one ends of the bridge-cut aluminum base are respectively provided with a spring 78, the movable ends of the springs 78 are connected with the wires 72 through fasteners 77, the fasteners 77 are metal screws, rectangular aluminum gaskets are respectively arranged on the two metal screws, the wires 72 connected between the two metal screws are copper bare wires, and the copper bare wires are finally grounded.

Step two: and a limiting device 75 is arranged on the side face of the broken bridge aluminum base, the limiting device 75 is 4 aluminum blocks, and two aluminum blocks are arranged at the bottom of the side face of the broken bridge aluminum base and serve as initial positions of two metal screws. The other two aluminum square blocks are arranged at the 5mm position above the metal probe, and once the unexpected situation occurs, the metal screw drives the copper bare wire to continuously move, the aluminum square block positioned at the upper part can be forced to stop so as to prevent the copper bare wire from extruding the metal probe to deform the metal probe under the stress.

Step three: a through hole is formed in the top of the metal shielding cover 3, a rotating shaft 80 with the same size is inserted into the through hole, the rotating shaft 80 is preferably an aluminum rod, and the aluminum rod is ensured to be in close contact with the metal shielding cover 3 without gaps. The aluminum rod is provided at one end inside the metal shield 3 with two bearing pulleys 82 for tightening the connecting rope 81.

Step four: 2 fixed pulleys 83 are installed above the inside of the metal shielding case, one ends of two connecting ropes 81 are respectively fixed on two bearing pulleys 82, and the two fixed pulleys 83 are respectively wound around to be connected with rectangular aluminum gaskets at two ends of a lead 72.

Step five: a motor 79 is installed on the top of the metal shielding case, the motor 79 is a stepper motor, the stepper motor is connected with the aluminum rod through a conveyor belt 84, and the stepper motor is controlled by a host computer 85 to control the rotation speed and the rotation direction of the stepper motor.

Step six: one of the rectangular aluminum pads is mounted, and the power switch 12 of the surface charge detection module 9 is mounted on the moving track of the lever 73. The pin b1 of the electrometer chip in the surface charge detection module 9 is connected with a metal probe as an input end. The pin b6 and the pin b8 of the electrometer chip in the surface charge detection module are shorted together as an output end, as shown in fig. 4.

The method for measuring surface charge by adopting the second embodiment of the invention comprises the following steps:

Step two: when the power is discharged, the upper computer 85 controls the stepper motor to rotate forward at the speed of 120mm/min, the running time is 10s, the bare copper wire is driven to move to the position of the metal probe 5, and after the stepper motor moves for 2s, the deflector rod 73 touches the power switch 12, so that the power supply for the surface charge detection module is in an on state.

Step three: when the stepping motor is stopped after running for 10 seconds, the bare copper wire reaches the metal probe 5 and is in close contact with the metal probe, so that residual charges on the metal probe are discharged into a grounding end, and the voltage is measured to be zero from a measuring end, namely the fact that the electricity discharge is complete is indicated. After 5s, the stepping motor is controlled to reversely run for 2s, and then the stepping motor stops, so that the copper bare wire moves to an initial position far away from the metal probe. At this time, the electricity leakage is completed, and then the measurement experiment of the surface charge of the insulating material to be measured can be performed.

Step four: when the surface charge measurement experiment is completed, the stepping motor is controlled to rotate reversely for 8s, the bare copper wire returns to the initial position, and the deflector rod 73 touches the power switch 12 in the returning process, so that the power supply for the surface charge detection module is in a closed state, and the experiment is completed.

The specific composition of the automatic discharging structure in this embodiment is shown in fig. 3, and the whole discharging process is described as follows: the initial position of two slidable metal screws embedded in the middle of the broken bridge aluminum base is the position of two aluminum square blocks below the base, the two metal screws are connected by an aluminum connecting piece, the two metal screws are guaranteed to move together, a copper bare wire is further connected between the two metal screws and connected to a metal shielding box body by a wire, and the metal shielding box is connected with a grounding end. Firstly, measuring the vertical distance between the copper bare conductor and the metal probe, recording the data, controlling a driver through an upper computer, driving a stepping motor to rotate forward at a speed of 120mm/min, and obtaining the running time of the stepping motor by measuring the vertical distance between the copper bare conductor and the metal probe and the rotating speed. The stepping motor is provided with 1 bearing pulley, the aluminum rod is provided with 3 bearing pulleys, one bearing pulley on the aluminum rod is arranged outside the metal shielding box, the installation position is level with the position of the bearing pulley on the stepping motor, and the two bearing pulleys are connected by a conveying belt 84, so that the stepping motor drives the aluminum rod to synchronously move. The other two bearing pulleys on the aluminum rod are arranged inside the metal shielding boxes, one ends of the two connecting ropes 81 are respectively fixed on the bearing pulleys 82 inside the two metal shielding boxes, and respectively bypass the 2 fixed pulleys 83 to be connected with rectangular aluminum gaskets at two ends of the lead 72. When the motor 79 rotates positively, the bare copper wire moves towards the position where the metal probe is located, and the deflector rod 73 touches the power switch 12 during movement to enable the power switch 12 to be turned on, and the surface charge detection module 9 starts to work, wherein the detection module mainly comprises a DC-DC power supply and an electrometer chip, the model of the power supply is UWE1205S-1WR3, the function of the power supply is to provide stable positive and negative double-circuit power supply for the electrometer chip, the model ADA4530 of the electrometer chip inputs bias current as low as 20fA, and the detection sensitivity is high. The surface charge detection module is installed inside the metal shielding box, and a wiring mode schematic diagram and information of each chip pin are shown in fig. 4 and table 1 respectively. As shown in fig. 4, the a1 pin of the power supply is connected with the negative electrode of the 9V dry battery, the a2 pin of the power supply is connected with the positive electrode of the 9V dry battery, the a5 pin and the a7 pin of the power supply are respectively connected with the b5 pin and the b4 pin of the electrometer chip, and stable dual power supplies of +5v and-5V are input to the electrometer chip. The b1 pin of the electrometer chip is connected with the metal probe, the b6 pin and the b8 pin of the electrometer chip are short-circuited to be used as output ends, and the real-time voltage of the output ends, namely the surface voltage of the insulating material, can be measured through BNC connectors by the output ends.

At this point, since the discharging process is not complete, there is some residual charge on the metal probe such that the measured output voltage is not zero. When the stepping motor continues to rotate forward for a set stop time, the copper bare wire is just in close contact with the metal probe, residual charges on the metal probe are discharged to the grounding end through the copper bare wire, the measured voltage of the output end is observed to be zero at the moment, the current discharge is completed, then the stepping motor is controlled to rotate reversely for 2 seconds and then stop, at the moment, the two metal screws are also subjected to the reaction force of the springs, and the copper bare wire is driven to move for a certain distance towards the initial position direction, but the initial position is not reached yet. At this time, the residual charge on the metal probe is cleared, the measurement experiment of the surface charge of the sample to be measured can be formally started, after the experiment is finished, the stepping motor is controlled to rotate reversely, and the deflector rod 73 touches the power switch 12 when moving to the initial position, so that the power switch is turned off, and the whole experiment is finished.

In this example, the same piece of silicone rubber material was used, with a diameter of 10cm and a thickness of 2mm, and the first comparative experiment was: the electrostatic capacitance probe with the leakage device is used for measuring the surface charge attenuation of a certain point of the silicon rubber, the measurement result is shown in figure 5, and the surface potential curve measured by the electrostatic capacitance probe with the poor shielding effect is found to be not a smooth curve, which is caused by the unstable output of the electrometer due to the influence of an external electromagnetic field on an electrometer chip.

In this embodiment, static electricity is removed from the surface of the silicone rubber by using a static electricity removing ion fan, and the formal measurement is started after the surface potential of the silicone rubber tends to zero. Figure 6 shows the results of a conventional electrostatic capacitance probe, and it can be found that there is some positive charge with a larger amplitude on top of the silicone rubber (i.e. the measurement start point), up to 0.25V. The electrostatic capacity probe with the electricity leakage structure is adopted by the invention, the driver is controlled by the upper computer, the stepping motor is controlled by the driver, and the stepping motor drives the metal round table with the grounding wire to reciprocate, so that the grounding wire is contacted with the metal probe to achieve the purpose of resetting the initial charge of the metal probe. The process is fully automatically controlled, and the initial charge of the metal probe does not need to be cleared manually as in the conventional structure. Since the electrostatic field of the human body is not influenced, the result of measurement by using the electrostatic capacity probe with the electricity discharging structure is shown in fig. 7, the surface potential distribution of the silicon rubber is relatively uniform, and the situation of potential distortion is not generated. In conclusion, when the electrostatic capacitance probe with the electricity leakage structure provided by the invention is used for measuring the surface charge distribution condition of the insulating material, the reliability and the accuracy are improved.

It will be understood that the invention has been described in terms of several embodiments, and that various changes and equivalents may be made to these features and embodiments by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. The surface charge measuring device comprises a metal shielding cover (3) and a metal probe (5) arranged in the metal shielding cover (3), and is characterized by further comprising a discharging device (7), wherein the discharging device (7) comprises a driving device (71) and a wire (72), the wire (72) is arranged in the metal shielding cover (3) and is connected with a grounding end, the driving device (71) drives the wire (72) to switch between a first position and a second position, the first position is in a state that the wire (72) is not contacted with the metal probe (5), and the second position is in a state that the wire (72) is contacted with the metal probe (5);

the metal shielding cover (3) is internally provided with a surface charge detection module (9), the surface charge detection module (9) comprises a power supply module (10) and an electrometer (11), the power supply module (10) provides power for the electrometer (11), and the electrometer (11) is electrically connected with the metal probe (5);

the wire (72) is provided with a deflector rod (73) which is used for being matched with the power switch (12) of the power supply module (10), when the wire (72) moves from a first position to a second position, the deflector rod (73) turns on the power switch (12), and when the wire (72) moves from the second position to the first position, the deflector rod (73) turns off the power switch (12).

2. The surface charge measurement device according to claim 1, wherein the discharging device (7) further comprises a guide rail (74) arranged inside the metal shielding case (3), the guide rail (72) is slidably connected with the guide rail (74), and a limiting device (75) for limiting the movable range of the guide rail (72) is arranged on the guide rail (74).

3. The surface charge measurement device according to claim 2, wherein the driving device (71) comprises a motor (79) arranged outside the metal shielding case (3), the guide rail (74) is a screw rod (741) arranged at two sides of the metal probe (5), two ends of the wire (72) are connected with the screw rod (741) through nuts (76), and one end of the screw rod (741) extends out of the metal shielding case (3) and is connected with an output shaft of the motor (79).

4. The surface charge measurement device according to claim 2, wherein the guide rail (74) is a movable channel (742) arranged at two sides of the metal probe (5), two ends of the wire (72) are slidably connected with the movable channel (742) through a fastener (77), one end of the movable channel (742) is provided with a spring (78) matched with the fastener (77), when the wire (72) is in the first position, the spring (78) is in a free state, and when the wire (72) is in the second position, the spring (78) is in a compressed state; the driving device (71) comprises a motor (79) arranged outside the metal shielding cover (3) and a rotating shaft (80) extending into the metal shielding cover (3), the rotating shaft (80) is connected with the fastening piece (77) through a connecting rope (81), when the wire (72) moves to the second position, the motor (79) drives the rotating shaft (80) to rotate so as to tighten the connecting rope (81), and the connecting rope (81) pulls the fastening piece (77) to move in the movable channel (742) and compress the spring (78); when the wire (72) moves to the first position, the motor (79) drives the rotating shaft (80) to rotate to release the connecting rope (81), and the spring (78) restores the natural state and drives the fastening piece (77) to move in the movable channel (742).