A technique for measuring impedance of cryogenic eddy current sensors using dual switched oscillators

Sagar, P and Hassan, H K and Karunanithi, R (2018) A technique for measuring impedance of cryogenic eddy current sensors using dual switched oscillators. In: JOURNAL OF INSTRUMENTATION, 13 .

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Abstract

Electrical conductivity measurement using an eddy current sensor requires measuring the absolute change in the impedance of the sensing coil. There have been many different attempts at this by using phase sensing circuits, utilizing impedance analyzers etc. This work utilizes two different oscillator circuit (LC oscillator using an unbuffered inverter and Relaxation Oscillator) to determine the change in impedance of the coil. The LC oscillator is designed in such a way that the circuit is insensitive to change in the series resistance of the sensing coil and hence, only a function of the inductance of the coil. Once the inductance of the coil is determined, a relaxation oscillator is used in an operating region in which the output frequency is a strong function of the series resistance of the coil. This switched oscillator circuit technique is used to determine the impedance of a cryogenic sensing coil at 295K and 77K with a Niobium (Nb) target kept at specific distance. Experimental data is compared with that of an impedance analyzer circuit and measurement errors are presented.

Item Type:	Journal Article
Publication:	JOURNAL OF INSTRUMENTATION
Publisher:	IOP PUBLISHING LTD, TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND
Additional Information:	Copy right for this article belong to IOP PUBLISHING LTD, TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND
Department/Centre:	Division of Physical & Mathematical Sciences > Centre for Cryogenic Technology
Date Deposited:	30 Aug 2018 15:41
Last Modified:	30 Aug 2018 15:41
URI:	http://eprints.iisc.ac.in/id/eprint/60526

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