The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 02, 1982
Filed:
Feb. 11, 1980
Ricoh Company, Ltd., Tokyo, JP;
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.