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ELECTROSTATIC VOLTMETER SELF-TEST FEATURE

IP.com Disclosure Number: IPCOM000024517D
Original Publication Date: 1980-Dec-31
Included in the Prior Art Database: 2004-Apr-02
Document File: 2 page(s) / 65K

Publishing Venue

Xerox Disclosure Journal

Abstract

When an electrostatic voltmeter is to be used to perform a control function, it is important to insure its proper operation. Allowing the system to measure a test surface carrying a calibrated potential is a common procedure for accomplishing this. The circuit of the figure is disclosed as a method whereby the need for a special test surface and a calibrated power supply can be avoided.

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ELECTROSTATIC VOLTMETER SELF-TEST Proposed Classification FEATURE U.S. Cl. 324/32
J. E. Courtney Int. C1. GOlr 5/28

When an electrostatic voltmeter is to be used to perform a control function, it is important to insure its proper operation. Allowing the system to measure a test surface carrying a calibrated potential is a common procedure for accomplishing this. The circuit of the figure is disclosed as a method whereby the need for a special test surface and a calibrated power supply can be avoided.

Numeral 1 represents any surface whose potential is to be measured. Electrostatic voltmeter probe body 2 contains a sensing electrode 3, a self-test antenna member 4, and the shutter 5 whi& isolates the probe from the surface to be measured. The signal from the sensing electrode is fed via the input circuitry 6 to the variable power supply 7. The self-test antenna is normally connected to the circuit through resistor 8 during normal sense periods when the shutter is open. During self-test periods, when the mutter is closed, relay 9 is closed and the signal from the test input supply 10 is applied to the self-test antenna. The system reads this input as it would read the potential of the surface to be measured with the shutter open. The test input and the electrostatic voltmeter output are compared in comparator 11, and the error output 12 is fed to a microprocessor or another appropriate device. Because of the error comparison, the need for a calibrated input is elim...