Development and application of an electrostatic microprobe

Powders with a wide particle size distribution often display bipolar tribocharging characteristics. Also, triboelectrification of solid insulating surfaces generally produce a non-uniform charge density. The standard Faraday cup method of measuring charge is incapable of detecting bipolar charging and non-uniformity in surface charge density. An electrostatic microprobe has been developed which is capable of detecting charge on individual particles as small as 50μm as well as resolving charge density variations on continuous surfaces. This paper describes the microprobe and the results of its application.