Absolute capacitor and differential capacitor measuring circuit

Abstract

The invention discloses an absolute capacitor and differential capacitor measuring circuit and method. The absolute capacitor and differential capacitor measuring circuit comprises a crystal oscillation circuit for measuring an absolute capacitor and a circuit for measuring a differential capacitor, and the absolute capacitor and differential capacitor measuring method comprises a method for measuring the absolute capacitor and a method for measuring the differential capacitor. According to the absolute capacitor and differential capacitor measuring circuit, the principle of the crystal oscillation circuit is utilized, all elements are common electronic elements, the structure is simple, the floor area of the circuit is small, and the elements are convenient to purchase, low in power consumption and extremely low in cost; a single power supply is adopted for supplying electricity to the circuit, voltage of a VCC of the power supply ranges from 2V to 6V, a TTL and a CMOS level are completely compatible, and the circuit has a wider application range; the resolution of the circuit mainly depends on frequency measurement precision, an existing frequency measurement technology is mature, and high-precision capacitance measurement can be achieved; according to the circuit for measuring the differential capacitor, a frequency difference is extracted only by using a data flip-flop; the circuit for measuring the differential capacitor is simple and can be used for measuring not only the differential capacitor but also the absolute capacitor.

Description

technical field [0001] The invention relates to a capacitance measuring circuit and method, in particular to a capacitance measuring circuit and method using a crystal oscillator circuit to measure absolute capacitance and differential capacitance, and belongs to the field of electrical and electronic measurement methods and devices. Background technique [0002] At present, capacitance measurement and processing circuits can be roughly divided into: frequency modulation circuit, bridge method, DC charging and discharging circuit, synchronous demodulator method, etc. [0003] (1) The frequency modulation method is also called the oscillation circuit method, which is based on the idea of ​​capacitance / frequency conversion to detect the measured capacitance. This method is to place the capacitive sensor in the LC or RC resonant circuit to form an oscillating circuit. When the measured capacitance changes, the oscillating frequency of the oscillating circuit will change accordi...

AI Technical Summary

Problems solved by technology

The main problems are: large output nonlinearity; poor dynamic characteristics

This method has high measurement accuracy, but it needs to provide sine wave or square wave and positive and negative power supply, so the measurement circuit is complicated and the cost is high

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