Sign indicator for rotating voltmeters - has optical chopper system using IR emitting diodes and IR sensitive diodes or phototransistors

摘要

The rotating voltmeter with sign indicator for high-voltage DC measurements comprises a high-voltage electrode above a perforated, fixed cover plate. Between the fixed plate and a measuring electrode is located a rotating perforated chopping disc driven from a motor shaft passing through the base plate and measuring electrode. The exciter source for the optical chopper system uses an infra-red emitting diode. The photo-electric sensor uses a photo diode or photo-transistor sensitive to infrared light. These elements are housed in a light proof enclosure in the base of the rotating voltmeter assembly. This form of construction avoid amplitude modulation effects and the need for large motors associated with earlier types of sign indicators.