Sensitivity control manner and electrostatic sensor null of electrostatic

摘要

PURPOSE: To reduce the load on an operator and shorten regulating time. ;CONSTITUTION: A voltage controlling oscillating circuit 2 repeatedly changes the frequency of a standard frequency signal within a determined frequency range on the basis of a standard frequency sweep control voltage VC supplied from a standard frequency sweep circuit 20. A resonator 3 outputs a high frequency voltage changed in amplitude according to its resonance characteristic and the change of frequency of the standard frequency signal. A wave detector 7 outputs a DC voltage according to the amplitude of the high frequency voltage. The sensitivity of an electrostatic sensor 1 is regulated so that the DC voltage is within a determined change range. Thus, it is not required to repeatedly pass a test piece between detecting electrodes.;COPYRIGHT: (C)1994,JPO&Japio