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Tiny capacitance measurement circuit based on TDC

A technology for measuring circuits and tiny capacitance, which is applied in capacitance measurement, measurement of electrical variables, measurement of resistance/reactance/impedance, etc.

Inactive Publication Date: 2017-05-31
祁艳
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Most of the current measurement circuits use the charge transfer method or the AC method, which converts the capacitance into a voltage or current. The circuit is often affected by the charge injection effect of the electronic switch, and the contradiction between improving the measurement speed and improving the resolution is difficult to solve.

Method used

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  • Tiny capacitance measurement circuit based on TDC
  • Tiny capacitance measurement circuit based on TDC
  • Tiny capacitance measurement circuit based on TDC

Examples

Experimental program
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Effect test

Embodiment Construction

[0018] like figure 1 As shown, the TDC-based tiny capacitance measurement circuit mainly includes battery, sensor, power management module, control module, analog front end, data readout interface and so on. The PS∅21 chip converts the capacitive signal generated by the sensor into a corresponding 24-bit digital quantity; the MSP430 controls and sets the PS∅21 through the SPI interface, and stores the digital quantity into the flash memory of the MSP430; Use the VisualBasic 6.0 soft panel to display the measurement result curve in the computer; the power management department can provide time-sharing controllable power supply to MSP430 and PS∅21.

[0019] like figure 2 As shown, in order to achieve low power consumption, the system enters the ultra-low power consumption state LPM4 after power-on. In order to avoid malfunction of the system, when the capacitance signal needs to be measured, the ON signal is set high. If the ON signal has been set high within 30s, the system ...

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Abstract

The present invention designs a tiny capacitance measurement circuit based on a TDC. The circuit mainly comprises a battery, a sensor, a power supply management module, a control module, a simulation front end and a data reading-out interface, etc. The tiny capacitance measurement circuit based on the TDC can convert the capacitance measurement to accurate time measurement, and the ratio of the sensor capacitance to the reference capacitance is equal to the ratio of the discharge time therebetween. The internal algorithm can greatly inhibit the influence of a stray capacitance on the measurement result, and the internally integrated temperature compensation module can ensure good stability. A high-performance simulation switch is selected to greatly reduce the influence of the charge injection effect, and the high precision refresh rate can mitigate the contradiction of the measuring speed and the resolution.

Description

technical field [0001] The invention relates to a tiny capacitance measuring circuit, in particular to a TDC-based tiny capacitance measuring circuit. Background technique [0002] The capacitive signal output by capacitive sensors is often very small (1 fF~10 pF), and there is also the influence of stray capacitance and parasitic capacitance of the sensor and its connecting wires, which puts forward very high requirements for the measurement circuit of the capacitive signal, so small The measurement of the capacitive signal has become the bottleneck of the development of capacitive sensor technology. [0003] Capacitance measurement circuits (including general-purpose capacitance detection chips) have a process of charging and discharging the sensor capacitance, converting the capacitance into non-capacitance such as voltage and current. Most of the current measurement circuits use the charge transfer method or the AC method, which converts the capacitance into a voltage o...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R27/26
CPCG01R27/2605
Inventor 祁艳
Owner 祁艳
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