Electric field sensor using electrostatic force deflection of a micro-spring supported membrane

An electric field sensor is shown which uses a micromachined micro-spring supported membrane as the sensing element. The sensing mechanism involves electrostatic force to deflect the membrane, and an optical position sensor to measure membrane movement. Measurement resolution was 5 kV/m for a dc field and 140 V/m for a 49 Hz ac field. It is shown that a bias voltage applied to the membrane can be used to increase measurement sensitivity. With a 17 kV/m dc bias field, a 0.3 V/m ac field at 97 Hz was detectable.