GB1526196A - Capacitors - Google Patents

Abstract

1526196 Measuring capacitance PLESSEY CO Ltd 24 Nov 1975 [3 Sept 1974] 38343/74 Heading G1U In a method of aligning the sections of a multisection variable capacitor to bring the capacitances of all the sections substantially to equality, the sections of the capacitor are automatically sequentially monitored and values related to their capacitances are displayed. As described an A.C. current, from a source 7, Fig. 1, is applied, via a reference capacitor CR, to an amplifier 10 in opposition to a current from one of the sections 1 of the capacitor under test. The difference current is then phase-conscious rectified 12 to provide a voltage V o indicative of the value of the section 1 under examination. This process is repeated by the cyclic and sequential closure of contacts 4, so that a series of voltages V o appear corresponding to the capacitances of the successive sections 1. These voltages are displayed on a c.r.t., each as a short horizontal line (the c.r.t. x-drive being synchronized with the sequential closure of contacts 4) so that if all the sections have the same capacitance the succession of short horizontal lines forms a straight line across the c.r.t. Since the absolute values of the capacitances of the sections are not required, and to keep the display at a convenient place on the c.r.t., the effective size of the reference capacitor CR is varied by varying the gain of an amplifier 8, by a long time constant integrator 17, to maintain the average voltage V o constant.