Research On High-precision Linear Variable Differential Transformer Signal Conditioning Circui

Linear Variable Differential Transformer(LVDT)displacement sensor is an inductive displacement sensor,which can realize non-contact displacement measurement through the principle of magnetic induction electricity.In the process of detecting the change of displacement,friction and contact will not be produced,so it has the characteristics of long service cycle,fast response speed,high stability and good linearity.It is widely used in aerospace,construction,machinery,railway,electric power,textile,petroleum and other national economic industries.With the continuous and in-depth development of industrialization in various countries,in order to meet the rapid expansion of technology and the strict demand for the stability of the sensor itself,the requirements for LVDT displacement sensor performance are also gradually improving.Improving the accuracy has always been the trend of the development of LVDT sensor.There are many factors that affect the signal accuracy of LVDT sensor,and the signal conditioning circuit is one of the factors that affect the signal accuracy.Based on the bipolar integrated circuit technology,this paper designs a LVDT signal conditioning circuit that can work normally under the dual supply voltage of-15V～+15V.The circuit is composed of oscillator,fully differential op-amp,band gap reference circuit,two channel demodulation channels,divider and output operational amplifier.The function of oscillator and fully differential op-amp circuit is to generate fully differential sinusoidal excitation signal,and the excitation signal is induced by adjusting the moving position of LVDT core,and the induced excitation signal is transmitted to the two channel demodulation channels.Two binary multiplication signals can be obtained,and then the ratio can be obtained through the divider circuit.Finally,the ratio can be amplified through the output op-amp,and the output result can form a proportional relationship with the displacement of the LVDT core,which improves the accuracy of the LVDT feedback signal.In this paper,Spectre simulation software is used to comprehensively simulate the signal conditioning circuit of the designed high-precision linear variable differential transformer.The simulation results show that: Under all conditions,the effective value of the excitation voltage of the primary side part meets the expected requirements,the accuracy of the secondary side part is 1.179%,the maximum linearity is about 147.425 ppm of FS,the output voltage range is-11.326293 V ～ 11.3299888 V,and the gain error is 0.68944827% of FS.The maximum gain drift is about 25.68572ppm/℃ of FS,the maximum offset voltage is 0.97% of FS,the maximum offset drift voltage is 24.156ppm/℃ of FS,the maximum supply rejection ratio gain is 293.45ppm/V,and the maximum supply rejection ratio offset is 293.04ppm/V.The maximum value of CMRR gain is 1.32388ppm/V,and the maximum value of CMRR offset output is 3.7325ppm/V.The above simulation results meet the preset targets.The circuit layout drawing and overall layout routing are completed based on Virtuoso tool,and DRC and LVS verification are carried out by Calibre tool.