CN110596472A - Dielectric polarization capacitance type electrostatic field measuring method and system - Google Patents
Dielectric polarization capacitance type electrostatic field measuring method and system Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
- G01D5/24—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance
- G01D5/2405—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance by varying dielectric
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/12—Measuring electrostatic fields or voltage-potential
Abstract
The invention relates to a dielectric polarization capacitance type electrostatic field measuring method and system, and belongs to the technical field of electromagnetic field measurement technology and measuring instrument manufacturing. The capacitance sensor in the measuring system enables a measured electrostatic field and a voltage source electrostatic field to form the polarization interaction of a dielectric medium in two directions, so that the dielectric constant changes, the capacitance value changes, and the measured field intensity is converted into the change of the capacitance value of a sensor port. The capacitance value of the sensor port is measured by the capacitance measuring instrument, and the field intensity of the measured electrostatic field can be obtained. The voltage source can make the dielectric work at a proper working point, and the output-input proportionality coefficient of the sensor is improved. The electrostatic field measuring method can measure the weak electrostatic field, and has the advantages of large measuring range, high measuring sensitivity, high resolution and high accuracy. The electrostatic field measuring system provided by the invention is free of moving parts, and the system structure and the measuring circuit are simple, so that the electrostatic field measuring system has the advantages of high sensitivity, small volume, easiness in implementation, good stability and the like.
Description
Technical Field
The invention relates to a dielectric polarization capacitance type electrostatic field measuring method and system, and belongs to the technical field of electromagnetic field measurement technology and measuring instrument manufacturing.
Background
In many scientific research and engineering fields, electrostatic field measurement is a task that must be completed. For example, in a high voltage direct current transmission system, electrostatic field measurements around lines and equipment and on the surface of the ground are important basic data for determining whether the system meets electromagnetic environment requirements and the operational reliability of the system.
For electrostatic field measurement, the conventional measurement systems are mainly classified into two types: an electrostatic field measuring system based on a charge induction principle and an electrostatic field measuring system based on a photoelectric principle. Both have significant disadvantages.
The structure of the first type of electrostatic field measurement system based on the charge induction principle is shown in FIG. 1 (references: Zhang Jian Gong, et al. DC electric field measurement device develops [ J ]. high voltage technology, 2009, 35(12): 3027-. A typical configuration of a sensor based on the charge induction principle used in this system is a "field mill", as shown in fig. 2. The working principle is as follows: the motor 202 drives the grounded metal blade, i.e. the grounded shield 204, to rotate at a constant speed through the rotating shaft 203, and the lower electrode 205 is grounded through the resistor 206. When the blade rotates to coincide with the electrode, the detected electrostatic field 201 is shielded, the electrode cannot sense the electrostatic field, and no induced charge exists on the electrode or the existing charge is discharged to the ground; when the blade rotates to the state that the blade gap is opposite to or exposed from the electrode (as shown in the state of fig. 2), the electrode senses an electrostatic field 201, charges are induced on the electrode, and the accumulation and the dispersion of the charges are conducted through a resistor, so that the grounding wire of the electrode forms a current, a voltage is formed on the resistor, the voltage drives a subsequent circuit, and the corresponding field intensity can be obtained by measuring the current or the voltage.
It can be seen that a "field mill" is a sensor that converts the measured static field strength into current pulses. If there is no rotating shield blade, since the electrostatic field does not change with time, there will only be a change from no charge to induced charge on the electrodes, only one current pulse will be generated, and the field strength error calculated by current driving the following circuit with only one pulse will be large. The advantage of this "field mill" type is that the electrostatic field is converted into a continuous current pulse. The defects of the device are that the device is provided with moving parts, is easy to age and damage, and has poor stability, low resolution and large volume. It is obvious that a rotating or moving part in an electrical quantity measuring instrument is not the state that a general measuring instrument should have.
The second type of electrostatic field measurement system based on photoelectric principle is shown in FIG. 3 (refer to the issued patent of invention: a photoelectric integrated strong electric field measurement system, grant No. CN 1844941B, Zen , good and short). In fig. 3, a laser light source 301 outputs a linearly polarized light beam, which is coupled to a sensor 303 through a polarization maintaining fiber 302, the polarized light is modulated by an external measured electrostatic field 304, the output laser light is transmitted to a photoelectric converter 306 through a single mode fiber 305, and the conversion from the optical power to a voltage signal is completed, the voltage signal is input to an electrical signal detector 308 through a cable 307, and the measured field strength can be obtained through the detection of the voltage signal.
The electric field sensor based on photoelectric principle (refer to the patent of invention granted: an antenna-free photoelectric integrated sensor for measuring strong electric field, publication No. CN 1858602B, Zhang , He jin Liang) used in the system is made by utilizing the phenomenon that the electric field affects the polarization of light in transmission, the structure is very simple, and a common structure is as shown in FIG. 4, a wafer 401 with photoelectric effect is adopted, light waveguides 402 with two Y-shaped branches at two ends and mutually parallel middle are formed on the surface, and a metal shielding layer 403 is additionally arranged on one of two parallel light waveguides. When the electric field sensor is in the measured electrostatic field 404, the two optical waveguides form a differential sensor, one optical waveguide is used as the electric field sensor and is normally acted by the electric field, and the other optical waveguide is provided with a metal shielding layer and cannot sense the electric field, so that the light characteristics in the two optical paths are different, and the size of the measured electrostatic field can be reflected by measuring the difference of the light characteristics in the two optical fibers.
Although the photoelectric principle type sensor has a simple structure, the optical system is very complex, so that the measurement stability is poor, the cost is high, and the maintenance is complex. And the light is affected to a very low degree by the electric field, the sensitivity and accuracy of such a sensor or system is low and not suitable for measuring low electric fields.
Disclosure of Invention
The invention aims to provide a dielectric polarization capacitance type electrostatic field measuring method and system aiming at the defects that the existing 'field mill' type electrostatic field measuring system has moving parts and the photoelectric type system is complex to implement. The measuring method and the measuring system adopt the capacitance type electrostatic field sensor as a measuring key component, convert the measured field intensity into the change of the capacitance value of the sensor port by utilizing the dielectric polarization characteristic, and obtain the size of the measured electrostatic field by measuring the capacitance value.
The invention provides a dielectric polarization capacitance type electrostatic field measuring method, which comprises the following steps:
(1) preparing a sensor, wherein the sensor consists of a pair of electrodes and a capacitor core, the pair of electrodes are two conductor plates and are bonded on the end surfaces of two sides of the capacitor core, and the two conductor plates are connected with two leads to form a port of the sensor;
(2) applying a voltage to the sensor port prepared in the step (1), so that the dielectric medium forming the capacitor core is polarized in the direction vertical to the conductor plate, and the dielectric medium of the capacitor core works at the working point with large variation of the capacitance value of the sensor port;
(3) placing the sensor added with the voltage in the step (2) into a measured electrostatic field, wherein the measured electrostatic field polarizes the dielectric medium of the capacitor core in the vertical direction, namely the direction vertical to the transverse direction, so as to form the polarization of the dielectric medium in the vertical and transverse directions, so as to form a coupling relation between the polarization generated by the measured electrostatic field on the capacitor core and the polarization generated by a voltage source on the capacitor core in the two directions, and the measured electrostatic field enables the dielectric constant of the dielectric medium of the capacitor core to change, so that the capacitance of a sensor port changes;
(4) and (4) determining the relation between the capacitance change of the sensor port in the step (3) and the measured electrostatic field, wherein the specific process is as follows: the method comprises the steps of taking the field intensity of a measured electrostatic field as the input quantity of a sensor, taking the capacitance change of the sensor as the output quantity, determining the proportional coefficient of the output quantity and the input quantity, determining the proportional coefficient by adopting a calibration method, namely applying a known standard electrostatic field source to the sensor, obtaining the proportional coefficient by measuring the capacitance change of the sensor, repeating the process for multiple times by adopting the standard electrostatic field sources with different intensities to obtain a plurality of proportional coefficients, and fitting a relation curve between the capacitance change of the sensor and the measured electrostatic field according to the proportional coefficients;
(5) and (4) obtaining the size of the electrostatic field where the current sensor is located according to the capacitance change value of the sensor port obtained in the step (3) by using the relation curve in the step (4), so as to realize the measurement of the electrostatic field.
The invention provides a dielectric polarization capacitance type electrostatic field measuring system, which comprises:
the sensor comprises a pair of electrodes and a capacitor core, wherein the pair of electrodes are two conductor plates which are bonded on the end surfaces of two sides of the capacitor core 2, and the two conductor plates are connected with two leads to form a port of the sensor so as to form the sensor for measuring the capacitive electrostatic field;
the voltage source is a direct-current power supply, one end of the voltage source is connected with one electrode on one side of the sensor, the other end of the voltage source is connected with the other electrode of the sensor through the capacitance measuring instrument, and the voltage source is used for applying bias voltage to the sensor to enable the dielectric medium forming the capacitor core 2 to be polarized and enable the dielectric medium to work in an area with large capacitance value variation of the sensor;
the capacitance measuring instrument is connected to a port of the sensor after being connected with the voltage source in series and is used for measuring the capacitance value of the sensor port and uploading the measured capacitance value of the sensor port to the processor;
and the processor is connected with the output end of the capacitance measuring instrument and used for receiving the capacitance measuring data of the sensor port output by the capacitance measuring instrument, converting the measured capacitance into a field intensity value of the electrostatic field according to the relation between the capacitance value change of the sensor obtained by calibration and the measured electrostatic field, and outputting the measuring result of the measured electrostatic field.
Compared with the prior art, the dielectric polarization capacitance type electrostatic field measuring method and the dielectric polarization capacitance type electrostatic field measuring system provided by the invention have the following advantages:
(1) the dielectric polarization capacitance type electrostatic field measuring method reflects the measured electrostatic field by using the parameter change of the dielectric material, and the method is unique:
the measuring method of the invention adopts the capacitive electrostatic field sensor, converts the field intensity of the measured electrostatic field into the change of the capacitance value of the port of the capacitive sensor by utilizing the influence of the measured electrostatic field on dielectric parameters, and obtains the measured electrostatic field by measuring the change of the capacitance value. The working principle of the magnetic field sensor is similar to that of an existing static magnetic field measuring system based on a Hall effect sensor and a fluxgate sensor, and the measurement is realized by using the principle that the material parameters change under the action of the material field.
(2) According to the dielectric polarization capacitance type electrostatic field measuring system, the measured electrostatic field enters the sensor capacitor core from the side without the electrode, the shielding influence of the metal electrode on the measured electrostatic field is effectively avoided, and the sensor is ingenious in structure. The capacitance sensor adopted by the measuring method of the invention is composed of a cylindrical capacitor core and a pair of electrodes attached to the end faces of the capacitor core, the electrodes form two terminals of the sensor to output capacitance values, the end faces without the electrodes can enable a measured electrostatic field to enter the capacitor core of the sensor and act on a dielectric material of the capacitor core, the shielding influence of a metal electrode on the measured electric field is avoided, and the capacitance of the sensor is formed by the metal electrode.
(3) The electric field measuring method of the invention effectively improves the sensitivity and the accuracy of the sensor by two measures. Forming a relation between a measured electrostatic field and the capacitance value variation of the sensor by utilizing the polarization interaction of the dielectric material in two directions; applying bias voltage to the sensor to make the dielectric work at the nonlinear inflection point of the dielectric; both measures can increase the variation of the capacitance value of the sensor along with the field intensity to be measured, thereby improving the sensitivity and the accuracy of the measuring method and the system of the invention.
(4) In the measuring system of the invention, no moving part is contained, and the size of the sensor is small:
the measuring system of the invention adopts the capacitance type electrostatic field sensor to replace the traditional 'field mill' type sensor as a measuring key component, does not contain moving components, and fundamentally overcomes the defects that the 'field mill' type sensor is easy to age and damage, has large volume and the like due to the moving components. In addition, the sensor of the present invention has a small size and can measure an electrostatic field in a narrow area.
(5) The measuring system of the invention has simple structure, easy realization and low cost:
the capacitance measuring instrument is adopted to directly measure the capacitance values at two ends of the sensor, and the strength and the small value of the static field to be measured can be obtained through the change of the capacitance values. Compared with the photoelectric circuit and processing in the existing photoelectric measuring system, the measuring system of the invention has much lower complexity and cost.
Drawings
Fig. 1 is a schematic structural diagram of a conventional electrostatic field measurement system based on a charge induction principle.
Fig. 2 is a schematic diagram of a specific structure of a sensor 101 in the measurement system shown in fig. 1, wherein the sensor 101 is colloquially called a "field mill".
Fig. 3 is a schematic structural diagram of an existing electrostatic field measurement system based on the photoelectric principle.
Fig. 4 is a schematic diagram showing a specific structure of the sensor 303 in the measurement system shown in fig. 3.
Fig. 5 is a schematic structural diagram of a dielectric polarization capacitance type electrostatic field measurement system according to the present invention.
Fig. 6 is a schematic diagram of the voltage source 3 in the measurement system shown in fig. 5.
In fig. 5 and 6, 1 is an electrode, 2 is a capacitor core, 3 is a voltage source, 4 is a capacitance measuring instrument, 5 is a processor, 6 is a measured electrostatic field, 601 is a dc power supply, 602 is a first switch, 603 is a second switch, and 604 is a commutation bypass line.
Detailed Description
The invention provides a dielectric polarization capacitance type electrostatic field measuring method, which comprises the following steps:
(1) preparing a sensor, wherein the sensor is structurally shown in FIG. 1 and comprises a pair of electrodes 1 and a capacitor core 2, the pair of electrodes 1 are two conductor plates and are bonded on the end surfaces of the two sides of the capacitor core 2, and the two conductor plates are connected with two leads to form a port of the sensor;
(2) applying a voltage to the sensor port prepared in step (1), the voltage being supplied from a voltage source 3, so that the dielectric constituting the capacitor core 2 is polarized in a direction perpendicular to the conductor plate, and the dielectric of the capacitor core 2 is operated at an operating point where the variation in capacitance value of the sensor port is large;
(3) placing the sensor added with the voltage in the step (2) in a measured electrostatic field 6, wherein the measured electrostatic field polarizes the dielectric medium of the capacitor core 2 in the vertical direction, namely the direction vertical to the transverse direction, so as to form the polarization of the dielectric medium in the vertical and transverse directions, forming a coupling relation between the polarization generated by the measured electrostatic field on the capacitor core 2 and the polarization generated by the voltage source 3 on the capacitor core 2 in the two directions, and the measured electrostatic field enables the dielectric constant of the dielectric medium of the capacitor core 2 to change, so that the capacitance of a sensor port changes;
(4) and (4) determining the relation between the capacitance change of the sensor port in the step (3) and the measured electrostatic field, wherein the specific process is as follows: the method comprises the steps of taking the field intensity of a measured electrostatic field as the input quantity of a sensor, taking the capacitance change of the sensor as the output quantity, determining the proportional coefficient of the output quantity and the input quantity, determining the proportional coefficient by adopting a calibration method, namely applying a known standard electrostatic field source to the sensor, obtaining the proportional coefficient by measuring the capacitance change of the sensor, repeating the process for multiple times by adopting the standard electrostatic field sources with different intensities to obtain a plurality of proportional coefficients, and fitting a relation curve between the capacitance change of the sensor and the measured electrostatic field according to the proportional coefficients;
(5) and (4) obtaining the size of the electrostatic field where the current sensor is located according to the capacitance change value of the sensor port obtained in the step (3) by using the relation curve in the step (4), so as to realize the measurement of the electrostatic field.
The structure of the dielectric polarization capacitance type electrostatic field measurement system provided by the invention is shown in fig. 2, and the system comprises:
the sensor comprises a pair of electrodes 1 and a capacitor core 2, wherein the pair of electrodes 1 are two conductor plates which are bonded on the end surfaces of two sides of the capacitor core 2, and two conducting wires are connected with the two conductor plates to form a port of the sensor, so that the sensor for measuring the capacitive electrostatic field is formed;
the voltage source 3 is a direct-current power supply, one end of the voltage source 3 is connected with the electrode 1 on one side of the sensor, the other end of the voltage source 3 is connected with the other electrode 1 of the sensor through the capacitance measuring instrument 4, and the voltage source 3 is used for applying bias voltage to the sensor to enable the dielectric medium forming the capacitor core 2 to be polarized and enable the dielectric medium to work in an area with large capacitance value variation of the sensor;
the capacitance measuring instrument 4 is connected to a port of the sensor after being connected with the voltage source 3 in series, and is used for measuring the capacitance value of the sensor port and uploading the measured capacitance value of the sensor port to the processor 5;
and the processor 5 is connected with the output end of the capacitance measuring instrument 4 and used for receiving the capacitance measurement data of the sensor port output by the capacitance measuring instrument 4, converting the measured capacitance value into the field intensity value of the electrostatic field according to the relationship between the capacitance value change of the sensor obtained by calibration and the measured electrostatic field, and outputting the measurement result of the measured electrostatic field.
The following describes the embodiments and steps of the dielectric polarization capacitance electrostatic field measurement method and system according to the present invention with reference to fig. 5 and 6:
(1) sensor fabrication
The sensor is composed of a pair of electrodes 1 and a capacitor core 2, wherein the pair of electrodes are two conductor plates which are respectively bonded on the end surfaces of two sides of the capacitor core, and two conducting wires are connected with the two conductor plates to form a port of the sensor; the sensor is used for sensing the measured electrostatic field, and the measured electrostatic field enters the sensor capacitor core from the side surface of the cylindrical capacitor core without the electrode.
The two electrodes 1 of the sensor can be a copper plate, an aluminum plate and a stainless steel plate; the thickness is about 1 mm; the shape of the capacitor core 2 is consistent with the end face shape of the capacitor core, and can be round or square; the size should be slightly smaller than the end face of the condenser core 2. The capacitor core 2 is made of a dielectric material, which can be a material with a large dielectric constant, such as deionized water, liquid ammonia, mica, barium titanate composite material, and the like, and the larger the dielectric constant is, the better the non-linearity degree is, and the larger the capacitance value and the capacitance variation are. For liquid dielectrics a plastic container is made which is filled with the dielectric and sealed. The shape of the condenser core 2 can be a cylinder, a drum (the shape that two round end surfaces are smaller and the middle is thicker) or a rectangular surface. The two electrodes 1 are firmly fixed to the end faces with an adhesive, respectively. The length of the condenser core 2 (the distance between the two electrodes 1) is typically more than 2 times the diameter (or width).
In order to measure the ground electrostatic field of the HVDC line, the value is generally in the order of 4kV/m, and the capacitance value in the order of pF is considered in the range of a common capacitor measuring instrument (like a Whlcr digital bridge tester TH2838), so the capacitor core of the sensor can be made into the area of 100mm2The capacitor core is a sintered barium titanate sheet with the maximum relative dielectric constant of 160.
(2) Voltage source 3 and commutation and voltage value-taking strategies thereof
And (2) applying a voltage source 3 to the port of the sensor manufactured in the step (1), wherein the voltage source 3 is used for enabling the dielectric medium of the capacitor core 2 to work at a proper working point and generating transverse polarization, and the transverse polarization and the polarization of the dielectric medium by the electrostatic field to be measured form two-direction polarization, so that the coupling relation between the electrostatic field to be measured and the capacitance value of the sensor is formed. Therefore, the voltage of the voltage source is taken into consideration that the dielectric medium works at a reasonable working point, and the proportional relation of the sizes of the electrostatic fields in the two directions is also considered, so that the proportional coefficient of the sensor is made to be as large as possible.
The voltage source 3 can adopt a positive-negative reversing structure, as shown in fig. 6, a first switch 602 and a second switch 603 are connected in series with a direct current power supply 601, and a reversing bypass line 604 is arranged beside the first switch and the second switch; when the first switch 602 and the second switch 603 are closed downward, the voltage at the port of the voltage source 3 is positive left and negative right, and both are closed upward and connected to the commutation bypass line 604, the voltage at the port of the voltage source 3 is positive left and negative right, and the polarities of the voltages applied to the sensor before and after each commutation are opposite, so as to obtain two measured electrostatic field values in different voltage directions, which are used as the basis for judging whether the sensor is orthogonal to the measured electrostatic field direction or not, and when the two values are the same, the sensor is orthogonal to the measured electrostatic field direction, thereby realizing the direction measurement of the measured electrostatic field and the accurate measurement of the size of the electrostatic field. For measuring the ground electrostatic field of the hvdc transmission line the voltage value of the voltage source is taken to be 40V, which generates an electric field of about 2kV/m, around 1/2 measured. The performance requirement for the voltage source 3 is that the output voltage is stable and is affected as little as possible by temperature and external environmental changes. The switch in the voltage source can use a common relay or a semiconductor switch, and the closing frequency of the switch can be about 5 times per second.
(3) And determining the relation between the capacitance change of the sensor port and the measured electrostatic field.
Placing the sensor applied with the voltage source in the step (2) in a measured electrostatic field, enabling the measured electrostatic field to enter the capacitor core from the cylindrical surface of the capacitor core, polarizing the dielectric medium of the capacitor core in the vertical direction (namely, the transverse polarization direction of the voltage source 3 to the dielectric medium), forming the polarization of the dielectric medium in the vertical direction and the transverse direction, and forming a coupling relation between the polarization of the measured electrostatic field to the capacitor core and the polarization of the voltage source to the capacitor core in the two directions; through the coupling relation, the capacitance of the sensor port is changed by the measured electrostatic field;
the method comprises the steps of using the field intensity of a measured electrostatic field as the input quantity of a sensor, using the capacitance change of the sensor as the output quantity, determining the proportional coefficient of the output quantity and the input quantity, determining the proportional coefficient by adopting a calibration method, namely applying a known standard electrostatic field source to the sensor, obtaining the proportional coefficient by measuring the capacitance change of the sensor, and obtaining a plurality of proportional coefficients or a proportional coefficient table by adopting the standard electrostatic field sources with different intensities and repeating the process for a plurality of times.
The larger the proportionality coefficient of the output quantity, namely the capacitance variation, of the sensor to the input quantity, namely the measured electrostatic field value, the better, and the larger the proportionality coefficient, namely the capacitance variation, of the sensor to the input quantity, namely the measured electrostatic field value, the better, and the performance of the measuring system, such as accuracy. When the electrostatic field to be measured is absent, the transverse electrostatic field generated by the voltage source 3 causes the degree of polarization of the dielectric material of the condenser core 2 to be determined, the dielectric constant epsilon of which is also a fixed value, the sensor having a fixed capacitance value C, given a sensor geometry chosen with respect to the dielectric material0. When the measured electrostatic field (denoted as E)t) When present, it will polarize the dielectric material in the vertical direction, causing the direction and magnitude of the polarized dipole created by the transverse polarization to change, thereby reducing the dielectric constant E, E of the dielectric materialtThe larger the value of (E), the larger the reduction degree of epsilon, so that the relation between the reduction of capacitance and the measured electrostatic field is formed, namely deltaC (E) Kt)EtCoefficient K (E)t) For sensor output input proportionality coefficient, EtIs related to sensor geometry, voltage value of bias voltage source, dielectric material characteristics, etc. This coefficient K needs to be obtained by calibration after the measurement system has been made using known standard electrostatic field sources.
(4) Model selection of the capacitance measuring instrument 4:
the capacitance measuring instrument can adopt any type based on inductance-capacitance resonance, like a LCR digital bridge tester TH2838, and is connected to two ends of the capacitance sensor through a voltage source 3 to measure capacitance values of the two ends of the sensor; and uploads the measured capacitance values to the processor 5.
(5) The processor 5 effects the conversion from the measured capacitance value to the electrostatic field value:
and (4) injecting the capacitance change of the sensor port obtained in the step (3) and the proportionality coefficient of the measured electrostatic field into the processor 5, fitting a proportionality coefficient curve based on the proportionality coefficients, and converting the measured capacitance change value of the sensor port into the size of the electrostatic field according to the curve to realize the measurement of the electrostatic field.
(6) Debugging and measuring after the measuring system is manufactured:
the output and input proportionality coefficients are obtained by calibration after the measuring system is manufactured. The calibration method can utilize two circular plate electrodes which are more than 10 times of the probe to form a parallel plate capacitor, the distance between the two plates is smaller than the diameter of a polar plate of 1/5, and the direct current voltage applied between the polar plates is controlled to obtain electrostatic fields with different values, so that the electrostatic fields are used as standard electrostatic fields for calibration. A plurality of proportionality coefficients can be obtained through calibration, and curve fitting is carried out on the proportionality coefficients so as to adapt to accurate measurement of the electrostatic field on the non-calibration point. During calibration, the sensor is placed in a direction which is vertical to the transverse direction of the sensor.
When the measurement is performed, if the direction of the measured electrostatic field is known, for example, when the electrostatic field on the ground surface below the high-voltage direct-current power transmission line is measured (which is one of the main measurement objects of the measurement system of the present invention), it is known that the direction of the electric field is always perpendicular to the ground surface, and at this time, only the sensor is ensured to be horizontally placed (a level gauge can be additionally installed on the sensor), and a correct electric field measurement result can be obtained. Because the sensor is a unidirectional sensor, if the electrostatic field with unknown direction needs to be measured, the sensor must be correctly placed, and the measured electric field is transversely vertical to the sensor, so that the consistency of the measurement state and the calibration state of the sensor can be ensured, and an accurate measurement result can be obtained. Because a reversing voltage source is adopted, the transverse polarization direction of the dielectric medium can be reversed, if the electric field values measured in the two directions are different, the transverse direction of the sensor is not perpendicular to the direction of the measured electrostatic field, the system can obtain the direction deviation of the sensor according to the measured values in the two directions, a prompt function is set to prompt a user to adjust the direction of the sensor, and the user adjusts the direction of the sensor according to the prompt until the system requirement is met, so that the accurate measurement of the size of the electrostatic field can be realized, the direction of the electric field is just above the probe, and the direction of the electric field is upward (corresponding to the right direction) or downward according to the positive and negative values given by the system.
Claims (2)
1. A dielectric polarization capacitance type electrostatic field measurement method is characterized by comprising the following steps:
(1) preparing a sensor, wherein the sensor consists of a pair of electrodes and a capacitor core, the pair of electrodes are two conductor plates and are bonded on the end surfaces of two sides of the capacitor core, and the two conductor plates are connected with two leads to form a port of the sensor;
(2) applying a voltage to the sensor port prepared in the step (1), so that the dielectric medium forming the capacitor core is polarized in the direction vertical to the conductor plate, and the dielectric medium of the capacitor core works at the working point with large variation of the capacitance value of the sensor port;
(3) placing the sensor added with the voltage in the step (2) into a measured electrostatic field, wherein the measured electrostatic field polarizes the dielectric medium of the capacitor core in the vertical direction, namely the direction vertical to the transverse direction, so as to form the polarization of the dielectric medium in the vertical and transverse directions, so as to form a coupling relation between the polarization generated by the measured electrostatic field on the capacitor core and the polarization generated by a voltage source on the capacitor core in the two directions, and the measured electrostatic field enables the dielectric constant of the dielectric medium of the capacitor core to change, so that the capacitance of a sensor port changes;
(4) and (4) determining the relation between the capacitance change of the sensor port in the step (3) and the measured electrostatic field, wherein the specific process is as follows: the method comprises the steps of taking the field intensity of a measured electrostatic field as the input quantity of a sensor, taking the capacitance change of the sensor as the output quantity, determining the proportional coefficient of the output quantity and the input quantity, determining the proportional coefficient by adopting a calibration method, namely applying a known standard electrostatic field source to the sensor, obtaining the proportional coefficient by measuring the capacitance change of the sensor, repeating the process for multiple times by adopting the standard electrostatic field sources with different intensities to obtain a plurality of proportional coefficients, and fitting a relation curve between the capacitance change of the sensor and the measured electrostatic field according to the proportional coefficients;
(5) and (4) obtaining the size of the electrostatic field where the current sensor is located according to the capacitance change value of the sensor port obtained in the step (3) by using the relation curve in the step (4), so as to realize the measurement of the electrostatic field.
2. A dielectric polarization capacitance electrostatic field measurement system, the measurement system comprising:
the sensor comprises a pair of electrodes and a capacitor core, wherein the pair of electrodes are two conductor plates which are bonded on the end surfaces of two sides of the capacitor core 2, and the two conductor plates are connected with two leads to form a port of the sensor so as to form the sensor for measuring the capacitive electrostatic field;
the voltage source is a direct-current power supply, one end of the voltage source is connected with one electrode on one side of the sensor, the other end of the voltage source is connected with the other electrode of the sensor through the capacitance measuring instrument, and the voltage source is used for applying bias voltage to the sensor to enable the dielectric medium forming the capacitor core 2 to be polarized and enable the dielectric medium to work in an area with large capacitance value variation of the sensor;
the capacitance measuring instrument is connected to a port of the sensor after being connected with the voltage source in series and is used for measuring the capacitance value of the sensor port and uploading the measured capacitance value of the sensor port to the processor;
and the processor is connected with the output end of the capacitance measuring instrument and used for receiving the capacitance measuring data of the sensor port output by the capacitance measuring instrument, converting the measured capacitance into a field intensity value of the electrostatic field according to the relation between the capacitance value change of the sensor obtained by calibration and the measured electrostatic field, and outputting the measuring result of the measured electrostatic field.
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