LVDT Position Sensing System

A Linear Variable Differential Transformer (LVDT) and analog signal conditioning circuit are used for a position sensing system. An oscillator provides a sinusoidal excitation signal to the primary winding of the LVDT. The differential secondary winding outputs are rectified and low-pass filtered. The difference voltage, which is proportional to the mechanical displacement of the LVDT core, is the measurement result.

This virtual prototype can be used to select the low pass filter frequency, so it is low enough that the oscillation frequency is mostly removed from the output signal, yet high enough to track the natural frequency of mechanical system the sensor is intended to measure. It can also be used to analyze parasitic effects, such as the resistance of the wires connecting the sensor to the signal conditioning circuits. This resistance affects the output voltage and therefore corrupts the measurement results. Likewise, the non-linear behavior of the rectifier diodes affects the linearity of the position measurement.This can be seen if the force input is slowly ramped from -1000N to 1000N over a 1 second interval.

Adam GM's picture



Adam GM

Joined December 31, 2013
Design added Friday, September 4, 2015 | 8:49 am PDT