Offset adjustement device for direct current measuring apparatus

摘要

The zero reset has a sensor (1) associated with a clip on ammeter using Hall effect or magnetoresistive cells supplying an amplifier (2) which has an output terminal (3). The gain of the amplifier may be varied by adjusting the value of the feed back resistors (23) by switches (22). A microprogrammed system (10) controls (17) a two way switch (5) connected either to earth (7) or the output terminal (3). The resulting signal passes through a convertor (11) to the microprogrammed system (10) which generates a correcting signal and feeds it through a convertor (13) to the amplifier (2).