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Differential capacitance PWM converter

A differential capacitance and converter technology, applied in the direction of measuring electrical variables, instruments, measuring resistance/reactance/impedance, etc., can solve problems such as high cost, complex implementation, unsatisfactory stability, and reliability

Inactive Publication Date: 2010-06-30
SHANGHAI UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

These methods are relatively complex to implement, not ideal in stability and reliability, difficult to integrate, and relatively high in cost

Method used

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  • Differential capacitance PWM converter
  • Differential capacitance PWM converter
  • Differential capacitance PWM converter

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0047] PWM Capacitance Meter

[0048] PWM capacitance measuring instrument circuit such as Figure 12 shown.

[0049] In the application of capacitance measurement, the capacitor C12 to be measured and the reference capacitor C11 are connected to form a differential capacitor in the form of a half bridge. The reference capacitor C11 adopts a high-precision and high-stable capacitor with a capacity close to that of the capacitor C12 to be measured.

[0050] The differential capacitor and the PWM signal generating unit form a PWM converter.

[0051] The PWM capacitance measuring instrument is composed of a PWM converter and a low-pass filter. The output of the PWM converter is connected to the input of the low-pass filter. The low-pass filter usually adopts the inertial circuit form composed of operational amplifier A3, resistors R30, R31, R32, and capacitor C31.

[0052] The relationship between the average value Uo of the output voltage Uo of A4 and the peak voltage Up of ...

Embodiment 2

[0062] Capacitive PWM differential pressure detector

[0063] Capacitive PWM differential pressure detector circuit such as Figure 14 shown.

[0064] The capacitive PWM differential pressure detector uses a differential capacitive pressure sensor with two internal capacitors C11 and C12 and protective capacitors C01 and C02 to form a differential capacitor, and a PWM converter with a PWM signal generating unit.

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Abstract

The present invention relates to a difference capacitor PWM convertor which belongs to the field of automatic control and measuring technique. The difference capacitor PWM convertor is composed of a difference capacitor and a PWM signal generating unit. The common end of the difference capacitor is commonly earthed. The signal end of the difference capacitor is connected with the signal input endof the PWM signal generating unit. The signal output end of the PWM signal generating unit is connected with the PWM signal output end of the difference capacitor PWM convertor. The PWM signal generating unit is composed of a reversing element, a holding ring comparator, a voltage follower and a converting resistor. The left signal end of the reversing element is connected with the signal input end of the PWM signal generating unit. The right signal end of the reversing element is connected with the signal end of the voltage follower. The converting resistor is cross-connected between the signal input end and the signal output end of the holding ring comparator, and at the same time the signal input end of the holding ring comparator is connected with the signal end of the voltage follower. The signal output end of the holding ring comparator is connected with the signal output end of the PWM signal generating unit. The difference capacitor PWM convertor has the advantages of simple and reliable structure and large practicability.

Description

technical field [0001] The invention relates to a differential capacitance PWM (pulse width modulation) converter (PWM converter for short), which belongs to the technical field of automatic control and measurement. Background technique [0002] Differential capacitive pressure sensors are commonly used in measurement and control systems such as pressure and flow in industrial sites. Their structures are equivalent to two half-bridged differential capacitors. Change, the relationship between the pressure difference and the capacitance value is as follows: [0003] ΔP = K P C 2 - C 1 C 2 + C 1 [0004] Among them, Kp is approximately a constant, that is, the pressure difference is propor...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R27/26G01L13/06
Inventor 朱明刘晖陈怡张英姿张金龙司霞
Owner SHANGHAI UNIV