| 摘要 |
An electrometer system particularly adapted for non-contact measurement of electrostatic charges in electrostatography, such as the charge level on photoreceptor surface areas in xerographic machines. The electrometer circuit has a very high impedance normally floating input, and a simple D.C. measurement circuit. The measurement circuit output can be read by a conventional test meter. The electrometer is controlled by a simple switching arrangement providing an automatic zeroing position in which the initial level of the input circuit is automatically reset by a feedback amplifier from the output to compensate for any temperature induced or other variations in the measurement circuit. The power supply voltage is automatically monitored and the output meter is driven to a non-zeroing position in response to a low supply voltage by a feedback amplifier circuit operative only in the zeroing position, overriding the automatic zeroing circuit.
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