Automatically programmed inductive tester - is for coins or metal discs passing between transmitter and receiver coils and has comparator

摘要

A comparator and a D/A convertor are used for metal discs passing between transmitter and receiver coils has comparator. The enveloping voltage curve of the alternating field induced by the transmitter is passed after rectification and smoothing to a reference voltage store (7), a comparator (10) and a minimum circuit (12). The output of the reference voltage store (7) is connected to a D/A convertor (9) which receives digital nominal values from an ROM (8) via a control unit (13). The comparator (10) is connected to the digital-to-analogue converter (9) and enters the comparison values in a store and connecting circuit (11). The reference voltage system includes a pick-up coil and an operational amplifier.