Microcomputer based phase sensitive detector

Abstract

A fully digital phase sensitive detector which utilises a microprocessor card is presented. This unit can replace a sophisticated lock-in amplifier in most applications. The instrument stores the signal in a 1024 channel memory, thus permitting further numerical processing of the data. The programs for data processing can be implemented by the use to suit each particular experimental situation. The noise bandwidth of the instrument has been theoretically evaluated, and compared with that of a conventional phase detector, a degradation of the S/N ratio of 1.6 was obtained. The prototype has been used for the detection of the signal in a wide line NMR spectrometer substantially confirming the theoretical results. The instrument operates from 1 Hz to 32.25 kHz.