Micromachined Electric-Field Sensor to Measure AC and DC Fields in Power Systems

This paper describes a new type of electric-field sensor that has been fabricated using micromachining technology. This micromachined sensor is dramatically smaller than conventional field mills, possessing a field chopping shutter measuring only 1 mm² . The shutter is moved using thermal actuators, thereby eliminating the wear and tear associated with rotating and moving elements of field mills. The sensor requires minimal operating power, with the shutter being driven by a 75-mV drive signal while consuming only 70 muW. The field chopping shutter operates at ~ 4200 Hz, enabling the measurement of both ac and dc fields. Two sets of sense electrodes enable differential field measurements and, therefore, do not require a reference ground potential. The sensor has a linear response to the electric-field amplitude and has demonstrated that it is capable of measuring a dc field as small as 42 V/m. This miniature sensor is the smallest sensor with such a resolution for use in power engineering applications.