Measurement of eddy-current conductivity

Author

Lynch, A.C. ; Drake, A.E. ; Dix, C.H.

Author_Institution

National Physical Laboratory, Division of Electrical Science, Teddington, UK

Volume

130

Issue

5

fYear

1983

fDate

7/1/1983 12:00:00 AM

Firstpage

254

Lastpage

260

Abstract

The conductivity of the surface layers of a metal is measured industrially by eddy-current conductivity meters which need to be calibrated. The method described here allows the resistivity of an annular specimen, as measured by the eddy-current losses at frequencies in the range 10¿¿100 kHz, to be measured in units traceable to national standards. The apparatus is based on a Heydweiller bridge which measures the mutual inductance and mutual resistance of two toroidal windings on the annular specimen. Corrections are needed for the effects of self capacitance and the capacitance between windings. The overall uncertainty in the measurement is from about 0.4% at 10 kHz to 0.6% at 100 kHz, and it could not easily be improved. This is adequate for present purposes.

Keywords

bridge instruments; eddy currents; electrical conductivity measurement; measurement standards; 10-100 kHz; Heydweiller bridge; annular specimen; eddy-current conductivity; electrical conductivity measurement; mutual inductance; mutual resistance; surface layers of metal; toroidal windings;

fLanguage

English

Journal_Title

Physical Science, Measurement and Instrumentation, Management and Education - Reviews, IEE Proceedings A

Publisher

iet

ISSN

0143-702X

Type

jour

DOI

10.1049/ip-a-1.1983.0047

Filename

4645823