Surface acoustic-wave device for measuring high voltages

Abstract

A surface acoustic-wave (SAW) device for measuring high voltages is described. The device consists of two SAW oscillators fabricated on a 128° rotated Y-cut LiNbO3 substrate. The voltage to be measured is applied to one of the oscillators while the other oscillator acts as the reference oscillator for temperature compensation purposes. The frequency of the perturbed oscillator varies linearly with the applied voltage. An oscillator fabricated on a 0.5-mm-thick substrate can withstand greater than 9 kV of voltage giving a fractional frequency deviation greater than 1630 parts per million. Attractive features of this technique include: (1) direct measurement of high voltages without the need for resistive or capacitive voltage dividers, (2) very high input resistance, (3) direct conversion of voltage to frequency, and (4) resolution better than 0.01% of full scale. This paper will discuss the basic operation and present experimental data on the performance of the device. A technique for obtaining improved temperature compensation in SAW sensors will also be presented.