Micro capacitance difference detection method based on switching circuit

Abstract

The invention discloses a micro capacitance difference detection method based on a switching circuit. The switching circuit comprises a variable voltage source V1, a variable voltage source V2, an electronic switch S1, an electronic switch S2, a to-be-detected capacitive sensor output capacitor, a reference capacitor and an amplification circuit. One end of the electronic switch S1 is connected with the variable voltage source V1, the other end of the electronic switch S1 is connected with one end of the to-be-detected capacitive sensor output capacitor, and the other end of the to-be-detected capacitive sensor output capacitor is grounded. One end of the electronic switch S2 is connected with the variable voltage source V2, the other end of the electronic switch S2 is connected with one end of the reference capacitor, and the other end of the reference capacitor is grounded; the electronic switch S1 and the electronic switch S2 are connected in parallel and then connected with one end of the amplification circuit, and the other end of the amplification circuit is output voltage. According to the method, the variable quantity of the capacitive sensor output capacitor can be directly measured, and the influence of the background capacitor on the measuring result is eliminated; the measuring resolution ratio depends on the switch-on frequency n of the electronic switches, and measured resolution ratio can continuously change as needed.

Description

technical field [0001] The invention relates to the technical field of capacitance detection, in particular to a method for detecting output capacitance variation of a continuously variable resolution capacitance sensor based on a switch circuit. Background technique [0002] With the development and integration of emerging interdisciplinary subjects such as semiconductor microelectronics, materials, micro-electromechanical systems, and biomedicine, capacitive sensors have been valued and studied by researchers and engineers, and are widely used in chemical, medical, and manufacturing industries. middle. [0003] Capacitive sensors have the advantages of simple structure, high sensitivity, good dynamic performance, and not easily affected by temperature changes. They can be widely used in the precise measurement of physical quantities such as pressure, distance, and liquid level, and have broad application prospects. Therefore, for capacitance It is very important to accura...

AI Technical Summary

Problems solved by technology

[0005] 1. With the wide application of nanotechnology, traditional capacitive displacement sensors are developing towards high precision and miniaturization, and the requirements for capacitance detection are getting higher and higher. The capacitance change caused by physical quantities is very small, and the background capacitance of the capacitance itself is relatively small. The words are very large. For example, MEMS capacitive sensors usually have a detection capacitance of 10 -12 F, the change range of detection capacitance is 10 -15 Class F. For example, in the research of three-dimensional capacitive displacement sensors, the background capacitance is as high as 20pF, but the variable capacitance is only a dozen fF. With such a small variable capacitance, the useful output signal is very weak. At the same time, due to the influence of parasitic capacitance, Capacitive sensor signals are often submerged in external interference, which increases the difficulty of measurement, and stray capacitance and parasitic capacitance will vary with factors such as circuit structure, ambient temperature, and internal and external electric fields, and have great uncertainty. How to improve measurement sensitivity and signal-to-noise ratio become the key to microcapacitive detection.

[0006] 2. The existing micro-detection technology can be divided into two types according to the degree of integration. One is the measurement circuit designed using discrete components. The other is the measurement circuit designed using integrated chips. The detection circuit using discrete components has a wide range, However, due to poor anti-interference and poor resolution, generally only 0.1pF. Using integrated chip detection technology, the resolution is as high as 0.1fF, but the range is not wide, generally only a few pF. It can be seen that due to the design of the traditional capacitance transmission detection method itself There is a contradictory relationship between the measurement range and the measurement resolution, either at the expense of resolution for range, or at the expense of range for resolution, which severely limits the performance of traditional capacitance detection methods in measuring small capacitance changes.

[0008] (1) The traditional measurement method measures the absolute value of the capacitance, and the local capacitance has an impact on the output result;

[0009] (2) Once the range of the traditional measurement method is determined, the resolution cannot be changed.

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