SU1307395A1 - Method of measuring surface charge density of dielectric - Google Patents

Abstract

The invention relates to a technique for measuring the electrical characteristics of polarized dielectrics. The purpose of the invention is the innovation of measurement accuracy and safety. The proposed method is as follows. Excite mechanical oscillations of the electrode located above the surface of the dielectric instigated. Measure current, induction) and the moving electrode circuit at two different values of the compensating voltage and lower ionic compensation voltages. The charge surface density is determined by a formula using measured values as variables. A schematic of the method is illustrated in the drawing, where the following designations are given: C5 surface density of the dielectric charge; O is the surface density of the charge induced on the upper electrode; U is the constant voltage applied to the electrodes from an external power source; I is the current in the external circuit; o (j is the thickness of the dielectric; Eg and E. are the magnitudes of the electric field intensity, respectively, in the gap and inside the sample; d is the electrode-electret gap value. 1 CT. (About the current) Measuring instrument: npuSop

Description

Measure current I at And, 0,

(I)

The invention relates to a technique for measuring the electrical characteristics of polarized dielectrics, and specifically to methods for determining the magnitude of the surface density of charge 5, the current I, with a small amount (of the order of nonelectrets).

The aim of the invention is to improve the accuracy and safety of measurements.

The essence of the method of measuring the surface density of the charge dielectric dielectric 6L

 -eT

how many volts)

V .. -g on Uj (2)

Comparing formulas 1 and 2, we get:

  (% IV) §Е °.

It is carried out by a vibration method under conditions of partial compensation of a dielectric field by applying to the measuring capacitor with a dielectric two compensating voltages that are much smaller than the potential of the electret surface. The current in the capacitor circuit is measured, and the surface charge density is determined from the measured values of current under conditions of partial compensation.

G iu iMeep.-ii-L i, -i,

The essence of the invention and the derivation of the calculation formula is illustrated in the drawing. Letters on the drawing are marked:

G is the surface charge density of the dielectric;

the surface density of the charge induced on the upper electrode;

and - a constant voltage applied to the electrodes from an external power source; I is the current in the external circuit; L is the dielectric thickness; Eg is the magnitude of the voltage of the cacical floor in the gap; E is the intensity of the electric field inside the sample; d - the size of the electrode gap-electret.

When mechanical oscillations of the electrode are excited, alternating Tok will flow in the circuit:

15

I, se

The surface charge density of the dielectric can be calculated by the formula

  . 1a

L.

I, -Ii

(3)

20

G

moreover, according to this formula, both the magnitude of surface charge density i and the sign of charge can be determined. The measurement of the surface density of the charge according to the proposed method is carried out as follows.

The measured sample is placed in a measuring cell consisting of two electrodes, one of which (vibrating) is located at a distance d from the surface of the electret. The vibration of the electrode is carried out with a magnetoelectric vibrator. A small constant voltage, U, is applied to the electrodes from an external power source. In the particular case, it may be zero. Measure current

thirty

in the external circuit I.

Then on elec

 dt

- if

where S is the electrode area.

The value of the current in the circuit is directly proportional to the applied voltage:

.- | fcstrodes supply a voltage equal to several volts, measure it with a voltmeter, and determine the current Ij. By the formula (3), the surface density of charge С is calculated.

Claims (1)

Invention Formula 45 The method of measuring the surface the density of the charge of the dielectric, which consists in the excitation of mechanical oscillations of the electrode, 50 located above the fixed surface of the dielectric, the alternating current in the electrode circuit is measured, applied to the electrode and the compensation voltage measured, which is due to the fact that, in order to improve the accuracy and increase the safety of the measurements, the current induced in the circuit is measured. of the moving electrode at two different values, the current I is measured at I, 0,  current I, with a small (by (I)  I, with a little (order of  6L  -eT  current I, at low (order how many volts) V .. -g on Uj (2) Comparing formulas 1 and 2, we get:   (% IV) §Е °. I, se The surface charge density of the dielectric can be calculated by the formula   . 1a L. I, -Ii (3) 20 moreover, according to this formula, both the magnitude of surface charge density i and the sign of charge can be determined. The measurement of the surface density of the charge according to the proposed method is carried out as follows. The sample to be measured is placed in a measuring cell consisting of two electrodes, one of which (vibrating) is located at a distance d from the electret surface. The vibration of the electrode is carried out with a magnetoelectric vibrator. A small constant voltage, U, is applied to the electrodes from an external power source. In the particular case, it may be zero. Measure current thirty in the external circuit I. Then on elec Trodes supply a voltage and, equal to several volts, measure it with a voltmeter and determine the current Ij. By the formula (3), the surface density of charge С is calculated. 3 13073954 compensation voltage, the product of dielectric voltages with a full compensated constant for dielectric, and the surface density of the dielectric constant of the dielectric is determined by the formletric; / tt tt h t5 L dielectric thickness; GlUi-U, with t   ----- I,, 1 - values of induced currents, respectively, when pergda b - surface density at the second and the second voltage p yes; compensation.