GB1398310A - Apparatus for checking an electrical device especially a voltage tester - Google Patents

Abstract

1398310 Testing high voltage detectors IPA INTERNATIONALE PATENT-UND LIZENZ-ANSTALT 6 June 1972 [7 June 1971] 26366/72 Heading G1U [Also in Division H2] A probe for detecting the presence of a high voltage on a power line includes, or can be associated with, a Piezo-electric crystal, which either by having a high-pressure applied to it or by being hit, causes a voltage commensurate with that whose presence is to be detected to be applied to the probe thereby to test that it is operating correctly. Two main arrangements are described. In the first, a Piezo-electric crystal 1, Fig. 3, is positioned at the end of a cylinder containing a piston M latched at the bottom of the cylinder by a lever O. Depression of a test button Q compresses a spring V, thereby loading the piston, and eventually when the button is fully depressed its end rocks a lever J to unlatch the piston which is then propelled rapidly, by the compressed spring V, against the crystal 1. The resulting potential appearing across the crystal is applied directly to one end 15b of a glow discharge tube 15 in the probe, and via the probe contact 18 and a spark gap 13 to the other end 15a of the glow discharge tube 15, so that an operator can be sure that the tube is working correctly. Release of the button allows a relatively weak return spring U to relatch the piston in its normal position as shown. In the second arrangement two crystals 1, 2, Fig.1, are used, so arranged that a sideways force by a member 10 displaces the crystals to a more in-line position thereby applying a considerable longitudinal pressure to the crystals. The potentials appearing across the two crystals are paralleled, outputs being taken from a centre connection 11, and an end connection 12. The two-crystal arrangement may also be used with impulsive force as shown in Fig.4a, in which in use the contact 18 of the probe is withdrawn against a spring 28 and let go, thereby causing a hammer 27 forceably to strike the end of the two crystals 1, 2. The probe shown in Fig.4a is of the kind in which light from the glow discharge tube 15 is conducted by a glass fibre 24 to a photo-cell 25, Fig.4b, whose output is amplified 31, 33, to energize a buzzer 30.