Design And Implementation Of LVTD Measuring System And Signal Conditioning Circuit

Linear Variable Differential Transformer(LVDT)has been widely used in various fields by virtue of its simple and reliable structure,long service life,high accuracy and sensitivity,strong adaptability to the environment and many other advantages.However,there are few theoretical studies on LVDT in China,especially in the aspect of signal conditioning.There are two main problems in the use of LVDT displacement sensor: LVDT conditioning circuit is expensive and difficult to popularize;The chip technology needed to condition the circuits is plagued by a "choke" problem.Make our country dependent on others in this respect.To solve the above problems,this paper designs a set of conditioning circuit and measurement system based on LVDT precision displacement sensor,and the circuit working principle of each module is analyzed and discussed in detail and simulation experiment.The conditioning circuit uses low cost chip,can complete the excitation signal generation,received signal amplification,filtering and other functions.The carrier signal can be extracted more completely under the condition of low signal-to-noise ratio.The design and manufacture of hardware integrated circuit mainly includes two parts: excitation signal generator circuit and receiving signal processing circuit.The excitation signal generating circuit can form a sinusoidal signal with adjustable amplitude range,and the frequency of the generating signal is easy to adjust.The signal conditioning integrated circuit mainly consists of three parts: high gain instrument amplifier circuit in the front section,double amplifier bandpass filtering circuit in the middle section,and controlled gain amplifier circuit at the end.By modifying the single resistance of the band-pass filter,the passband bandwidth can be adjusted without affecting the center frequency of the band-pass filter.By adjusting the potentiometer in the circuit,high magnification of weak signal can be realized.The simulation experiment shows the practicability of the signal conditioning circuit.Finally,the design of the circuit PCB and the production of the material.Aiming at the nonlinear problem of LVDT sensor with domestic GD32F303 processor,this paper starts with the basic principle of least square method and uses Matlab software system to fit the curve,reducing the nonlinear degree of the system from 3.56% to 0.96%.And finally use LCD display to display the measurement results.At the same time,because the signal conditioning circuit system is easy to adjust,it can also be used in other weak signal processing with similar needs.