Automatic gain control for electrostatic voltmeters

Details Automatic gain control for electrostatic voltmeters Automatic gain control for electrostatic voltmeters

2000-11-30

2002-04-30

Grimley, Arthur T. (Department: 2852)

Electrophotography

Control of electrophotography process

Electrometer detail

C324S457000, C399S048000

Reexamination Certificate

active

06381426

ABSTRACT:

CROSS-REFERENCES TO RELATED APPLICATIONS
This application is related to Xerox docket No. 0740 (IP/A00102).
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to gain control, and more particularly, to such control when used with ESVs (electrostatic voltmeters) in xerographic copying machines.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In xerographic copying machines it is desired to measure the potential on a photoreceptor to achieve better copy quality. This is done using an ESV. However, the standard “feedback” ESV is a second order feedback system. The “speed of response” of the ESV is dependent on the open loop gain of the system, which is dependent on both the spacing between a sense probe or head and the mechanical modulation (change in the spacing). In practice, there is an electronic gain control that is adjusted in the factory setup procedure to give the desired output response at the calibration spacing and the assumption is made that the amount of modulation stays constant. If the system gain is “high”, the output will overshoot the final value. If it is “low”, it will be slow or underdamped. If it is “optimized”, it is “critically” damped, i.e., it is going as fast as possible without overshooting.
In the past, it has been assumed that the amount of gain remains constant. In fact, it is dependent on a stable modulating structure, such as the standard tuning fork and the newer ASIC (application specific integrated circuit) ESV “vibrating beam. Such structures can gave gains that vary with time, temperature, etc. Also, circuits in such structures can be floating at the high photoreceptor voltage, thereby making gain adjustment difficult.
It is therefore desirable to have an adjustable gain, even when the ESV is floating at a high voltage, in order to maintain optimum gain, and thus response speed.
BRIEF SUMMARY OF THE INVENTION


REFERENCES:
patent: 4106869 (1978-08-01), Buchheit
patent: 4417804 (1983-11-01), Werner, Jr.
patent: 5243292 (1993-09-01), Borton et al.
patent: 5950040 (1999-09-01), Mestha et al.

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