Accession Number : AD0262934

Title :   EXACT EQUATIONS FOR THE RADIO FREQUENCY MAGNETIC PERMEAMTER

Corporate Author : NATIONAL BUREAU OF STANDARDS BOULDER COLO

Personal Author(s) : HOER,CLETUS A. ; RASMUSSEN,ALVIN L.

Report Date : 11 AUG 1961

Pagination or Media Count : 1

Abstract : A set of exact equations is derived for initial or reversible permeability (mu prime) and dissipation factor (tan delta) using the rf permeameter (an impedance transformer for measuring toroidally-shaped magnetic materials at radio frequencies) for which no assumptions regarding the arms of the equivalent T-network have been made. A low loss toroidally-shaped magnetic material is used as an impedance standard in calibrating the permeameter in terms of the exact equations. An evaluation is made of the results obtained using these equations and other equations based on assumptions regarding the Tnetwork. A frequency range from 0.1 mc to 50 mc and a tan delta range from 5 x .0001 to 5 are covered. The comparison shows that expressions for tan delta based on assumptions regarding the equivalent transformer structure produce errors of several orders of magnitude when applied to low loss materials, and that some equations for mu prime may be in error as much as an order of magnitude for high loss materials. The utility of the permeameter is particularly important in the measurement of magnetic materials in the 0.1 mc to 50 mc frequency range where it has a convenient impedance not readily obtained by using other techniques. (Author)

Descriptors :   *ELECTRICAL IMPEDANCE, *PERMEAMETERS, *TRANSFORMERS, CALIBRATION, EQUATIONS, MAGNETIC CORES, MAGNETIC MATERIALS, MATHEMATICAL ANALYSIS, MEASUREMENT, RADIOFREQUENCY

Distribution Statement : APPROVED FOR PUBLIC RELEASE