Design of an adaptive soft calibration circuit for LVDT

This paper presents a soft calibration technique for displacement measurement using Linear Variable Differential Transducer (LVDT). The objective of the proposed work is to design a circuit, which will calibrate automatically the output of LVDT based on the range set by the user. The output of LVDT is drawn from both the secondary coils, and is acquired on to the system through the DAQ card (NIElvis). The acquired AC signal is first converted to pure DC by the help of rectifiers and filters. The two secondary coil signals which have been obtained from filters are passed through comparators circuits. The gain of filters and comparator circuits are controlled based on the user choice of range. The circuit once design is tested using practical setup, proposed setup produced accurate results and avoided repeated calibration which otherwise would be needed whenever the range of measurement was changed.