SU974431A1 - Three-electrode variable capacitor - Google Patents

Description

i (54) THREE-ELECTRODE CONDENSER VARIABLE CAPACITY

The invention relates to electrical measuring technology and can be used in transformer measuring bridges of alternating current.

Known high-frequency capacitor variable capacitance coaxial-cylindrical type with a contactless piston, the so-called piston capacitor 1.

The main disadvantage of the known capacitor is the substantial linearity at the edges of the capacitance range, due to the edge effects.

Closest to the invention to the technical essence is a three-electrode variable capacitor, containing coaxially arranged stationary external and internal electrodes and a movable shielding cylindrical electrode 2.

The disadvantage of such a variable capacitor is a change in the capacitance between the stationary electrodes and the screen as the main (pass-through) capacitance changes, as a result of which the capacitance changes, shunting the transformer arms

or other elements of the bridge (depending on the chosen scheme of the transformer bridge). For this reason, the frequency and depth measurements and the measurement accuracy of transformer bridges are significantly reduced.

The purpose of the invention is to improve the measurement accuracy.

This goal is achieved by the fact that in a three-electrode variable capacitor containing a coaxially arranged stationary external and internal electrodes and a movable shielding cylindrical electrode placed between them, the length of the stationary external and movable shielding cylindrical electrodes are related by the following relation

2,

17

where 1 is the length of the stationary external 25 electrode;

1, is the length of the movable screened cylindrical electrode. .

To hell (the design of the proposed capacitor is shown on the same day).

Between the outer 1 and inner 2 stationary cylindrical electrodes there is a movable screening cylindrical electrode 3 displaced along them. The porous electrode is equipped with electrical leads 4, 5 and b for connecting to the transformer bridge circuit. Since the shielding cylindrical electrode lere part of the electric field in space to the meiod by electrodes i and 2, the extracted electrode 3 corresponds to the maximum capacitor capacitance, and the introduced one corresponds to the minimum.

The proposed design of a variable capacitor track electrode capacitor provides the constancy of the capacitance between the external (elongated) electrode 1 and the electrode 3 when the shielding cylindrical electrode is moved, which provides a positive effect. The capacitance between the internal electrode and the movable cylindrical shielding electrode changes as a result, however, this is H (% decreases the measurement accuracy, so to & to: the ecological capacitance is connected parallel to the input of the null indicator and therefore does not

The use of the proposed design of a three-electrode variable capacitor provides an increase in the accuracy of measurement of transformer bridges when operating in the latitude frequency range.

Claims (2)

1. Measuring equipment. W .11, 1961, p. 48. 2. Grinevich FB and others. Transformer, datum measuring bridges. M., Energie, 1970, p. 235 (prototype).