Design Of Amplifier And Filter Circuit For Electrostatic Sensor And Its Electromagnetic Compatibility

In industrial production,it is often necessary to measure the parameters of the wind powder particle in the pipe of Gas-Solid two phase flow.The most common method is electrostatic measurement.Therefore,the quality of the electrostatic signal is a key factor for the measurement of the parameters of the wind powder particle.Usually,the electrostatic signals induced by electrostatic sensors are extremely weak,and mixed with a variety of noise signals and have a low signal noise ratio(SNR),which is not conducive to the acquisition and calculation.In this paper,the mechanism of the generation of wind powder electrostatic signals,the principle of electrostatic sensors inducing the electrostatic signals,the design of amplifying and filtering circuits of the wind powder electrostatic signals,the electromagnetic interference of the system,and the communication and preservation of multi-channel sensor data are studied and analyzed.Following is the main content of this paper:This paper analyzes the generating mechanism of the wind powder particle static electricity and the factors which affect the charging of the wind powder particle,establishes the mathematic model of the point charge of the wind powder particle,and analyzes the parameters of the wind powder particle by measuring the electrostatic signals of it.This paper compares the advantages and disadvantages of different types of electrostatic sensors,and puts forward an approach of applying the AC-coupling technology to the plug-in electrostatic sensor,and combines the advantages of the direct contact sensor that has a large scale measurement,simple installation and small error,and the advantages of the non-direct contact sensor that with having a small influence on the flow pattern of wind powder particles and high sensitivity,and avoids the effect that direct contact sensor probe made on the flow pattern of wind powder particles and the insensitivity of inductive sensor to wind powder particles in the center of pipe.This paper also researches the principle of electrostatic sensor acquiring the wind powder electrostatic signals,models electrostatic sensor and analyzes its equivalent model and then regulates the output signals of the sensor by using the method of voltage detection.And in this paper,the experimental platform for measuring the parameters of the wind powder particle was built under the laboratory environment.Next this paper analyzes the characteristics of the wind powder particle electrostatic signals and designs the signal conditioning circuits,and then confirms various interference signals in the acquisition process of the wind powder particle electrostatic signals,and makes an electromagnetic compatibility analysis on the possible interferences signals caused by ground design,electromagnetic shielding,bypass and decoupling and finally formulates corresponding anti-interference and shielding measures to make the system meet the electromagnetic compatibility design requirements.In this paper,the communication and the data preservation of multi-channel sensor system is designed.This paper puts three groups of six-route sensors as objects and uses RS485 field bus technology to realize its communication,and meanwhile develops the upper computer monitoring interface and data storage system through VB6.0.Finally,this paper simulates the system of the wind powder particle electrostatic signals conditioning circuit with Multisim,and tests its gain characteristics and frequency characteristics respectively.And in this paper sand was used to simulate the Gas-Solid two phase flow signal to measure the wind powder particle electrostatic signal in the laboratory and compares it to the output signal of the electrostatic sensor.The experimental results show that the signal noise ratio of the signal output by the signal conditioning circuit is greatly improved.Using this signal to calculate the parameters of the wind powder particles can improve the measurement accuracy,thus verifying the feasibility of the system.