SU1647457A1 - Method for lossy capacitance measurement - Google Patents

Abstract

The invention relates to electrical measuring equipment and can be used to measure the capacitance of high-loss capacitors. The purpose of the invention, the improvement of measurement accuracy, is achieved by selecting an operating point that ensures maximum sensitivity of the measuring device. The method consists in supplying a variable voltage of a fixed frequency m from the generator to a measuring circuit consisting of series-connected capacitance Sev and a parallel oscillatory circuit formed by inductance L and total capacitance Cx + Co (measured and reference capacitances) , change the capacitance Co to obtain the minimum value of the voltage Umin on the measuring circuit, then change the capacitance Co again to obtain the maximum value of the voltage. Umaks fix the average value (Umak Umich +) / 2 e otschityvayu1 measuring circuit and the value of the measured capacitance of the capacitor on a scale model. 2 or

Description

The invention relates to electrical measuring equipment, is designed to measure the capacitance of high-loss capacitors, and can be used to create moisture meters.

The purpose of the invention is to improve the measurement accuracy by selecting the operating point of the measuring circuit, in which the systematic error is maximally compensated, due to the influence of the leakage resistance of the measured capacitance.

The goal is achieved by supplying a measuring voltage of a fixed frequency from the generator to the measuring circuit, changing the value of the reference capacitance to obtain the minimum value of UMHH on this circuit, then changing the value of the reference capacitance to obtaining the maximum value of the Umax voltage on the measuring loop, fixing the average mean Umaks + Umin

on the measuring circuit and read the value of the measured capacitance on the scale of the reference capacitor.

The method can be implemented using the device shown in Fig. 1, the dependence of the output voltage on the magnitude of the reference capacitance is shown in Fig. 2.

The device includes a generator 1, a voltmeter 2, a capacitance 3 communications (Sev), an exemplary inductance 4 (L), a variable exemplary capacitance 5 (Co), a key 6 terminals 7, 8 for connecting the measured capacitance Cx

The device works as follows.

The value of capacitance 5 (Co) is changed to achieve a minimum reading of a voltmeter that fixes the voltage on the measuring circuit formed by the series connection of capacitance 3 (Sev) and parallel oscillatory circuit containing inductance 4 (L), reference capacitance 5 (Co) and the capacity (Cx). The obtained minimum value UMHH (point I in the dependence of FIG. 2) corresponds to the voltage resonance in the measuring circuit. Then, the value of Co is again changed until the maximum value of the Umax voltage on the measuring circuit is reached. This corresponds to the lit point in the dependence of FIG. In this case, a resonance of currents takes place in a parallel oscillatory circuit. The average value of Vmax + UMHH Ux is determined, which is set using a voltmeter, changing the value of Co (point II in the dependence of figure 2). The obtained value of the model capacity corresponds to the measured one. In this case, the sample capacity has a calibration characteristic

Cx - ht Sev So,

arl

0

five

0

five

key costs 6. The presence of the key b in the device circuit is not critical.

The choice of the operating point on the dependency section that has the greatest steepness leads to a decrease in the instrumental error of the device, due to the influence of the leakage resistance of the measured capacitance.

Claims (1)

Invention Formula The method of measuring the high-loss capacitance, which consists in supplying a variable voltage of a fixed frequency from the generator to the measurement circuit, changes the value of the reference capacitance until a minimum value is obtained on this circuit, characterized in that, in order to improve the accuracy, the value of the model capacitance to obtain the maximum value on the measuring circuit, fix the half-sum of the minimum and maximum values of the voltages on the measurement circuit and count the value of the measured capacitance and a scale model of the capacitor: Cx one  f-gf G | G NE 0 where O) is the frequency variable. It follows from the condition of equality of the modules of the impedances of the measuring circuit and the capacitance of the North. That is, when setting the value of Co in accordance with the calibration expression, the voltage monitored by the voltmeter remains constant when closed and open where Cx is the value of the measured capacitance connected in parallel with the model capacitance Co and inductance L; Sev is a communication capacitor, connected in series with the parallel oscillatory circuit L, (Cx + Co) and forming a measuring circuit with it; u is the frequency of the variable current. FIG. one Umak with tt t FIG. 2