A voltage sensing device comprising a liquid crystal cell (10) electrically connected to a charged surface and having a light transmissivity varying with applied voltage. A light source (30) is directed through the liquid crystal cell, and a light detector (32) detects changes in the intensity of light directed through the cell and providing an output indicative of variations in voltage on the charged surface. Polarizers (24, 26), which polarize light from the light source directed through the liquid crystal cell, and analyze light exiting the cell, convert electro-optically induced phase changes into intensity changes. A saturation level biasing voltage is periodically applied to the liquid crystal cell to set the cell to a reference level, clearing the cell of transient polarization effects. A second reference liquid crystal cell may be provided, electrically coupled to a reference voltage. Signals from the charged surface derived by the liquid crystal cell connected to the surface are compared with reference signals derived by the reference cell prior to output of the signal to eliminate a time-based drift component from the output.