RU1803883C - Device for measuring capacitance - Google Patents

Abstract

Usage: in electrical engineering, in devices with capacitive measuring transducers of non-electrical quantities. SUMMARY OF THE INVENTION: the device comprises a measured capacitor 1, a reference capacitor 2, a power supply 3, two diodes 4, 5, a differential DC amplifier 6, a measuring device 7. A feature of the invention is the connection of the output of a power source 3 to the anodes of diodes 4, 5, the connection of the cathodes of the diodes, the second plates of the measured and reference capacitors and with the first and second inputs of the differential DC amplifier, as well as the implementation of the power source in the form of a generator of unipolar pulses, sk which is more than two azhnost. 2 ill.

Description

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The invention relates to an electrical measuring technique, in particular to measuring capacitance of capacitors, and can be used in devices with capacitive measuring transducers of non-electric quantities.

An object of the invention is to increase the accuracy of measurement of a device.

In FIG. 1 shows a schematic diagram of a device; in FIG. 2 is a form of electrical voltage at various points in the circuit.

The device contains capacitors 1 and 2, one of which, for example, capacitor 1, measured, the other is a reference, power supply 3, made in the form of a generator of unipolar rectangular pulses, the duty cycle of which is more than two, diodes 4 and 5, differential amplifier 6 constant direct current (UPT), the output of which is connected to a dc meter 7. The general conclusions of the power supply, differential CTF and measuring device are connected to the first plates of the measured and reference capacitors. The output of the power source is connected to the anodes of the diodes, the cathodes of which are connected to the second plates of the measured and reference capacitors and to the first and second inputs of the differential CTD.

The device operates as follows.

The power source 3 generates rectangular voltage pulses (Fig. 2a) with a peak value of E, a repetition period T and a duration of T, where y is the relative duration of the pulses - lies in the range 0 to 0.5. During the time T of the presence of these pulses, both capacitors 1 and 2 are charged through diodes 4 and 5, respectively, to voltage E (voltage Dei and UC2 in Fig. 2, b, c). In the intervals between the power pulses, the capacitors are discharged through the input circuits of the differential circuit breaker 6: during the discharge of the capacitors, the voltages on them are represented by segments of the exponentials in Figs. 2, b, c. The voltage difference AU of the capacitors (Fig. 2d) is fed to the input of the CTF. The average Do value of this voltage is a measure of the difference in capacitance between the measured and the reference capacitors: after amplification

it is recorded by meter 7.

The occurrence of the differential voltage A U is explained as follows. If, for example, the capacitance Ci of the capacitor 1

If the capacitor 1 is larger than the capacitor C2, then the discharge of the capacitor 1 is slower than the discharge of the capacitor 2. As a result, at the end of the discharge process, the voltage Ui UC1 is greater than the voltage U2 Uc2. The difference voltage U U UC1 to UC2 and its constant component U0 are shown in FIG. 2 g for the case of Ci € 2. In the case when Ci C2, the difference voltage AU has

opposite polarity. The introduction of new communications in the device for measuring capacitance and the implementation of the power source in the form of a generator of unipolar rectangular pulses with a duty cycle of more than two

improves measurement accuracy by increasing the sensitivity and linearity of the conversion characteristics of the device.

Claims (1)

The claims A capacitance measuring device comprising a power source, a measured and a reference capacitor, two diodes and a differential DC amplifier, the output of which is connected to a measuring device / general conclusions of a power source, a differential DC amplifier and a measuring device are connected to the first plates of the measured and reference capacitors, in that, in order to improve accuracy, the output of the power source is connected to the anodes of the diodes, the cathodes of which are connected to the second plates of the a removable and a reference capacitor and with first and second inputs of a differential direct current amplifier, the power supply is made in the form of a unipolar pulse generator, the duty cycle of which is more than two. Phi & 1