GB1457748A - Method of operation of a varistor - Google Patents

Abstract

1457748 Biasing radiation detectors GENERAL ELECTRIC CO 27 Dec 1973 [29 Dec 1972] 59806/73 Heading G1A [Also in Division H1] In a method of operating a photo-conductive varistor of the kind described in Specification 1457749, (see Division H1) comprising a sintered polycrystalline body of zinc oxide with a minor constituent consisting of at least one other metal oxide and/or halide, a pair of electrodes being disposed on a surface of the body and being separated by a gap, a potential difference applied between the electrodes is selected to determine the sensitivity and magnitude of current flowing between the electrodes when the gap is illuminated, so that the said current, which actuates a recording or control device, is a function of both the potential difference and the intensity of the illumination. To eliminate dark current in a device comprising main electrodes 11a, 12a Fig. 2, separated by a gap 15, a pair of reference electrodes 11b, 12b, shielded from incident radiation, are connected in a bridge circuit in opposition to the main electrodes. Alternatively, the reference electrodes may be disposed on the surface of the varistor opposite to that receiving the radiation. In a variant, Fig. 3 (not shown) one electrode (12c) is circular and is disposed concentrically within another annular electrode (11c), the gap 15 between them also being annular.