The Probe Type Dynamic Condenser Electrometer

Abstract

A dynamic condenser electrometer of probe type was constructed and its operating characteristics were investigated. Such an electrometer may be veryuseful in a measurement of the surface potential distributions over an area, or, in some cases, in a work on a specimen which is too small to be measured with the condenser electrometer of ordinary type.
The operating sensitivity of ca. ± 10m V was attained with a vibrating probe of about 1mm diameter. Measuring the capacity charge by Inoue circuit, the upper limit of sensitivity was estimated to be a few millivolts.
The resolving power was then examined by probing a goldplated surface partly covered with a thin foil of tin. It was found that the probe could fairly distinguish the inhomogeneity in surface potential so far as its extension is larger than or comparable with the cross-sectional area of the vibrating probe.
As an example of a practical application, an obliquely cut surface of a selenium rectifier wasi examined. The tripple, layers of surface metal, selenium and base metal were clearly recognized.