SU135966A1 - Device for measuring the surface density of electrical charges - Google Patents

Description

In the known devices for measuring the surface density of electrical charges on electrically insulating materials using a metal charge-relieving charge collector, a mechanical converter of a constant voltage to charge into an alternating voltage is used, which complicates the circuit and is necessary to maintain with special attendants.

In order to eliminate these drawbacks, it is proposed to apply for this conversion a circuit on two nonlinear capacitors with a ferroelectric (as varicades) included in the shoulders of an electric AC bridge, to one of the indicator vertices of which a collector is connected, and a measuring capacitor is connected to the measuring diagonal in series active resistance, forming the output.

The operation of the proposed device is based on the appearance of even harmonics in the curved current flowing through a capacitor with a ferroelectric, is found in alternating and constant electric fields.

Structurally, the device is proposed to be made in the form of a body made of an insulating material, comprising a collector, capacitors, and a metal grounded pole with a handle attached to the end, which is intended to overlay the body of the device on the surface of the test material.

FIG. 1, 2 depict schematic diagrams of the proposed device.

The main element of the proposed device are capacitors, of which nonlinear capacitors / and 2 with ferroelectric are included in the shoulders of the electric bridge, and the separator, for example mica, capacitor 3 is included in its measuring diagonal

№ 1359662

in series with the active measuring resistance 4. A variable voltage is applied to the bridge through the differential transformer .5. A common collector 6 is connected to the common connection point of the three capacitors forming the top of the bridge diagonal.

In the absence of a constant field (no charges) and the symmetry of the bridge circuit, no current flows through the coupling capacitor. In the presence of static electricity, a flux of electrical induction passes the sea: co ;, - a vector and a constant field appears in the ferroelectric insulator of the capacitors / and 2, and a second harmonic current arises in the circuit of the capacitors. If the current is a variable and constant field, for example in a capacitor /. match, then in capacitor 2 they are opposite in direction. As a result, the phase of the second harmonic current in the capacitor / is shifted by 180 ° with respect to the phase of the second harmonic current in the capacitor 2. Therefore, these currents are closed through the middle branch with the capacitor: and, folding, form a voltage drop IJ on the measuring resistance 4 proportional to the measured charge density:

U KRS 3,

where R is the resistance value 4; S is the collector area b; 3 - charge density, K - coefficient.

The voltage from the resistance 4 is fed to the amplifier 7, operating in cathodic repetition mode, from which the signal is transmitted to the phase-sensitive rectifier 8 with a bridge circuit in the anode circuit, a microammeter is inserted in the diagonal with a zero in the middle of the scale. The cathodes of the lamp of the rectifier 5 are fed with a current of doubled frequency from the generator I, as a result of which only the component of doubled frequency is rectified. When changing the charge of the measured charges, the arrow of the microammeter is deflected to the opposite half.

Structurally, the collector 6 is attached (Fig. 2) in the housing 10 of polished Plexiglas. The housing is closed with a metal lid //, fitted with a metal grounded: rod 12 with plastic RZK 13. Insulated conductors 14 pass from the capacitors}, 2 to 3 inside the rod and handles to turn on the power and the input of the amplifier. When measuring, a plexiglass box is applied to the charged surface of the dielectric and the density is measured.

charges:; on the instrument graduated in sdint1x -j- I

Subject invention

Claims (2)

I. A device for measuring the surface density of electrical charges on electrical insulating materials with the help of a stripping metal collector and a constant-voltage-to-variable voltage converter, characterized in that, in order to simplify the device, by eliminating mechanical converters, the collector connected to the common connection point of three capacitors, two of which are non-linear (like a variconds) and are included on the shoulders of an alternating current electrical bridge, and the third is a disconnecting one is included into the measuring diagonal of the bridge in series with the active resistance forming the output. 2. Device pop. 1, different TL-M. that the collector, together with the capacitors, is enclosed in a general casing of electrically insulating material, mounted on the end of a grounded metal rod, with which the collector is applied to the surface of the test object. / KVAOH  cm /