EDDY-CURRENT DECAY RESISTIVITY MEASUREMENTS USING A DIGITAL-VOLTMETER

A digital voltmeter is shown to successfully capture the voltage decay signal during eddy current decay (ECD) measurements at cryogenic temp eratures on low-resistivity specimens. The use of a voltmeter simplifi es ECD measurements, typically made using a digital oscilloscope. An a dded benefit of using a voltmeter is that under certain circumstances, measurement precision exceeds that which is normally obtained with a preamplifier-digital oscilloscope combination. Results indicate that t he best combination of instruments for capturing extremely weak signal s (i.e., those with long exponential time constants) is a preamplifier -voltmeter configuration. Results of a comparative study using a pream plifier-digital oscilloscope configuration, a digital voltmeter alone and a preamplifier-digital voltmeter arrangement are presented and dis cussed.