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SAMPLED AC REFERENCE

IP.com Disclosure Number: IPCOM000023615D
Original Publication Date: 1978-Jun-30
Included in the Prior Art Database: 2004-Mar-31
Document File: 2 page(s) / 304K

Publishing Venue

Xerox Disclosure Journal

Abstract

An electrometer and associated circuitry for measuring elec-trostatic charge levels on a text surface 10 such as a photoreceptor utilized in xerographic copying machines. The charge on the surface 10 is sensed by probe 12 and con-verted to a corresponding voltage level by a variety of known circuits in the head 14, with this level being represented by curve C in Figure 2. A constant amplitude AC reference signal B derived, for example, from a typical AC transformer sup-plying signal A, is coupled to the head 14 and to a zero detector 16. When signals C and B are at the same potential, zero detector 16 supplies a signal D to a sample and hold circuit 18 through optical isolator 20. Consequently, circuit 18 provides an output signal E representative of the potential on test surface 10 by reading the instantaneous voltage level of signal B at the time when it corresponds to the potential on test surface 10.

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Page 1 of 2

XEROX DISCLOSURE JOURNAL

SAMPLED AC REFERENCE
Robert F, Buchheit

Proposed U~S~C1~ Into Cl~

Classification

324/72

G01r 31/02

FIG. /

FIG. 2

Volume 3 Number 3 May/June 1978 181

I -~-~

C

B

0

[This page contains 1 picture or other non-text object]

Page 2 of 2

SAMPLED AC REFERENCE (Cont'd)

An electrometer and associated circuitry for measuring elec-
trostatic charge levels on a text surface 10 such as a
photoreceptor utilized in xerographic copying machines.

The charge on the surface 10 is sensed by probe 12 and con-
verted to a corresponding voltage level by a variety of known
circuits in the head 14, with this level being represented by
curve C in Figure 2. A constant amplitude AC reference signal
B derived, for example, from a typical AC transformer sup-
plying signal A, is coupled to the head 14 and to a zero
detector 16. When signals C and B are at the same potential,
zero detector 16 supplies a signal D to a sample and hold
circuit 18 through optical isolator 20. Consequently, circuit
18 provides an output signal E representative of the potential
on test surface 10 by reading the instantaneous voltage level
of signal B at the time when it corresponds to the potential on
test surface 10.

               XEROX DISCLOSURE JOURNAL
182 Volume 3 Number 3 May/June 1978

[This page contains 1 picture or other non-text object]