Electrometer probe
US4318042A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 11, 1980 |
| Grant date | Mar 2, 1982 |
| Priority date | — |
| Expiry date | Feb 11, 2000 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R29/12
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A detecting electrode (22) is formed on a substrate (28), an amount of potential from a charged surface (23) induced in the detecting electrode (22) corresponding to a potential on the surface (23). A guard electrode (26) formed on the same surface of the substrate (28) as the detecting electrode (22) surrounds the detecting electrode (22). Part of the guard electrode (26b) is formed on the back surface of the substrate (28). The detecting electrode (22) is connected to a non-inverting input of an operational amplifier (24). The output of the operational amplifier (24) is connected to the inverting input thereof and also to the guard electrode (26) to produce unity gain and place the guard electrode (26) at the same potential as the detecting electrode (22). The substrate (28) is formed of a material such that the electrical resistance between the detecting electrode (22) and the guard electrode (26) is at least 10.sup.9 ohms to reduce zero drift to a negligible value.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.