Noncontact test signal acquisition

Abstract

An arrangement of electrostatic pickups for logic signals is described; this allows data over a wide range of repetition rates to be acquired from insulated wires or from insulation-covered printed circuits. Minimum coupling capacities are of the order of 1 pF and it is shown that 5 V pulses from 0.5 Hz to 5 MHz can be detected and reproduced. Preliminary results are also reported for an electrostatic pickup system for audio frequency analogue signals. Applications are suggested in high voltage DC isolation of analogue or digital circuits, noncontact computer bus couplers and diagnostic probes.