SU1262421A2 - Method for measuring local density of surface charge - Google Patents

Abstract

The invention relates to electric meters, is an additional invention according to the author. St. No. 574684 and can be used in relief, electrography, etc. Otras x 1 V -: g, T. . fc a technology where it is necessary to measure the charge density on the surface of a WJ electric. The purpose of the invention is to increase the accuracy - it is achieved by additionally exciting the second quasistatic electric field with a different frequency and spatial distribution of the charge relative to the first. The charge density is determined from the system of solved equations using the results of the measurements made. The device for implementing the method includes a measuring probe 1, electrodes 2 and 3, a measuring electrode 4, a vibrator 5, generators 6, 7 and 20, i selective amplifiers 8-12, measuring devices 13-17, Dizlek (L trick 18, on which The local charge density has a metal substrate 19, to which a third generator 20, 1, or 6 is connected, N9 O) S Nd K5 w

Description

The invention relates to the field of electrical measurements, can be used, for example, in relief, electrography and other industries where it is necessary to measure the charge density on the surface of a dielectric, and is an improvement of the method according to ed. St. No. 574684.

The purpose of the invention is improving the accuracy of measurements. The goal is achieved in that they additionally excite a second quasistatic electric field having a different frequency relative to the first, and a different spatial distribution, measures alternating currents at a low frequency, at both high frequencies and at combination frequencies, and determine the charge density from the system of equations from the measurement results

I ₆ = H ^^ S ₄ / (H + S6 _d ) ² ,

I, "and, dC, / dt, 1 ₂ = and ₂ ac ₅ / ar,

Ι ₄ —Uq CjJj, _β where Η is the layer thickness;

£ is the dielectric constant;

And _o is the average distance from the charged surface to the measurement point;

4 * 1 - change during modulation;

- area of the measuring electrode;

- charge density;

- modulation frequency;

h) HuJ ₂ — frequencies of the first and second quasistatic high-frequency fields;

hUj are the amplitudes of the stresses exciting the high-frequency fields;

C, and C ₂ are capacitances in which high-frequency fields are excited;

1 ₅ and 1 ₄ are the amplitudes of the currents at frequencies, respectively, uJ,, uJ j, ll \ + S, <J ₂ + Q;

Ig is the amplitude of the current at a frequency of I.

The drawing shows an electrical schematic diagram of a device to illustrate the proposed method.

The device comprises a measuring probe 1 having electrodes 2 and 3 and a measuring electrode 4. The measuring probe 1 is mechanically connected to a vibrator 5 connected to the first generator 6, and the electrode 2 is connected to a common bus. The electrode 3 is connected to the second generator 7. The measuring electrode 4 is connected to the inputs of the selective amplifiers 8 - 12, tuned to the frequencies I, uJ,, respectively

o), + I, ul ^ + I. Measuring instruments 13-17 are connected to the outputs of the amplifiers. The dielectric 18, on which the local charge density is measured, is equipped with a metal substrate 19 to which a third generator 20 is connected.

The method of measuring the local surface charge density is as follows.

In the measurement region limited by the measuring probe 1, the first quasistatic electric field with a frequency of 7 is excited with a generator 7 and the second quasistatic electric field with a frequency of u) _? with the help of the generator 20. The excited electric fields are added to the electric field induced by the surface charge of the dielectric 18. The measuring probe 1 is driven by the vibrator 5 with the frequency I determined by the first generator 6. An alternating voltage arises on the measuring electrode 4 relative to the common bus by an electric field modulated with frequency I, using selective amplifiers 8-12 tuned to frequencies I, i), and b ₂ and the combination frequencies сЭ + Я h uJ ^ + I, and measuring instruments 13-17 measure alternating currents having corresponding frequencies.

The total current of the measuring electrode 4 depends on all system parameters that affect the measurement accuracy i _g = i _e + i, where ΐθ is the current determined by the surface charge;

i is the current determined by other parameters: the dielectric constant, the distance from the dielectric surface to the measurement point and its change, the area of the measuring electrode.

These parameters determine the capacitance between the electrodes 3 and 4 - C, and between the electrode 4 and the substrate 19 With ₅ . Knowing the quantities and U, as well as measuring the amplitudes of the currents, it is possible to determine all the parameters of the system from the equations

I, = U ₍ dC, / dt;

I _a "U ₄ dCj / dt;

I ₅ “U (C, ₄ ;

1 <= and ₄ C ₄ ^

From the values of Cj and C ₂ determine the parameters H, £, μ, and, substituting them in the equation

I _e = H _& fab2 / CH + Ch _o ) ', the local surface charge density is determined by the formula 5 = Ig. (H + 6h ₀ rAZHgah'S ^.

All parameters can be determined with high accuracy since. the values of voltages, frequencies of generators, as well as currents, are known. At 20, the error in determining the density of the surface charge does not depend on hard-to-account changes in the parameters.

Thus, the differences of the proposed method allow one to increase the accuracy of measuring the local surface charge density. When implementing the method, one can use the excitation of a larger number of quasi-ed static high-frequency electric fields.

Claims (1)

The invention relates to the field of electrical measurements, can be used, for example, in relief, electrophotography and other areas of the technique, where it is necessary to measure the density., Charge on the surface of the dielectric, and is an improvement of the method according to the author. St. No. 574684. The purpose of the invention is to reduce the measurement accuracy. The goal is achieved by additionally recovering a second quasi-static electric field having a different frequency relative to the first, and a different spatial distribution, measuring k) and alternating currents at a low frequency, both of their high frequencies, and at combination frequencies and measuring results determine the density charge from the system of equations i6 He uhas4 / (H - «- g),, dC, / dt, I, UjdC, / dt,, С, a),, I, U5C, a} ,, where Н is the thickness of the layer ; - dielectric constant; h is the average distance from the charged surface to the measurement point; L1 — change upon modulation; S is the area of the measuring electrode; B - charge density; - modulation frequency; i) I (x), 2 — frequencies of the first and second quasistatic high-frequency fields; and ii are the amplitudes of the voltages that excite the high-frequency field; and C - capacitances in which high-frequency fields 1, 2 I and 1 are excited - current amplitudes at frequencies uJ, (uJ aJ, .Q, 4j, + Q; Ig - current amplitude at frequency I.) The drawing shows the electrical circuit Devices for illustrating the proposed method. The device contains a measuring probe 1, electrodes 2 and 3, and a measuring electrode 4. Measuring probe 1 is mechanically connected to a vibrator 5 connected to the first generator 6, Electrode 2 is connected to a common busbar. with the second generator 7. Measuring electrode 4 is connected to the inputs of the selective amplifiers 8-12, which are tuned accordingly to the frequencies S1, uJ, 2; 1 to the outputs of the amplifiers are connected measuring instruments 13-17. Dielectric 18, on which the local charge density is measured, is provided with a metal substrate 19 to which the third generator 20. The method of measuring the local density of the surface charge is carried out as follows: In the measurement region bounded by the measuring probe 1, the first quasistatic electric field with a frequency oJ is excited with the help of a generator Ator 7 and the second quasistatic electric field with a frequency of cl), with the aid of the generator 20. The excited electric fields are added to the electric field induced by the surface charge of the dielectric 18. The measuring probe 1 is vibrated by a vibrator 5 of frequency 51, determined by the first generator 6. On the measuring electrode 4 with respect to the common bus, an alternating voltage arises, determined by the total electric field modulated with frequency. With the help of selective amplifiers 8-125 tuned to frequencies ft, and, respectively, the combination frequencies uJ + S ИЫ + Л, and measuring instruments 13-17 measure alternating currents having corresponding frequencies. The total current of the measuring electrode 4 depends on all the parameters of the system tt that affect the measurement accuracy, i: 6 - i where ig is the current determined by the surface charge; i is the current determined by other parameters: the thickness of the dielectric constant layer, the distance from the dielectric surface to the measurement point and its change, the area of the measuring electrode. These parameters determine the capacitances between electrodes 3 and 4 - C and between electrode 4 and the substrate 19. The value of U. and U .. and ft na / l 0 Jln irirlol (. P Jf. F can be determined by measuring the amplitudes of currents. all system parameters from equations I, U, dC, / dt; I, U, dC2 / dt; a3,; 1, U, C, J.. From the values of C. to C S. 2, the parameters H,,, are determined ,, t1 and, substituting their equation EonQ S / CH + eh), determine the local density of the surface charge by the formula. (rA2H ueiS,. All parameters can be determined with high accuracy, since the values of the voltages, frequencies of the oscillators, as well as currents known In this case, the error in determining the density of the surface charge does not depend on difficult-to-take changes in the parameters. Thus, the differences in the proposed method make it possible to increase the accuracy of measuring the local density of the surface charge. When implementing the method, one can use the excitation of a larger amount of quasi-static electric high frequency fields. The invention The method of measuring the local density of the surface charge on the author. St. No. 574684, characterized in that, in order to improve accuracy from the battery of the type of bit 10 for g. S., 1, in the field of measurements, the second is given. The quasi-static electric field, having a different hour relative to the first, and another the spatial distribution, of the alternating currents at the low hour, both of the high frequencies and at the com- munication frequencies, and based on the results of measurements, determine the density and from the system of equations H H € 4s 5 - (/ (),, dC- / dt, l5 UjdC2 / dt,, C, cJ,, I, U, C, u),, Н is the thickness of the charge layer; - dielectric constant; average distance from the charged surface to the measurement point; measurement when molud tsyug; the area of the measuring electrode; charge density; modulation frequency; frequencies of the first and second quasistatic high-frequency fields; amplitudes of voltages that excite a high-frequency field; and c, capacitances in which a high frequency field is excited; , g 1. the amplitudes of the currents at the frequencies uJ, jj-, «, + Л, Я; Ig current amplitude at a frequency of .si.