Hall, M; Bartholomew, J G; Harmon, S A C; Henderson, L C A (2001) The calibration and use of commercial low relative magnetic permeability measurement equipment in mass metrology. In: National Measurement Conference (NMC) 2001, 6-8 November 2001, Harrogate, UK.
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Abstract
The relative magnetic permeability (magnetic susceptibility) of a material determines how a magnetic field is influenced when this material is introduced. When a magnetic field gradient exists a force will be exerted on the material. The magnitude of this force depends on the value of the permeability and the volume of the material. In modern mass balances, force compensation is achieved using a permanent magnet. A magnetic field gradient therefore exists in the space occupied by the mass. For mass calibration purposes it is therefore necessary to specify the permeability of the materials used. These specifications and recommended commercial instrumentation for measuring the permeability are given in the OIML Recommendation R111 (Organisation Internationale De Métrologie Légale) [1]. These include an indicator, which uses inserts to determine the permeability range of the material being tested. For the traceable measurement of permeability these instruments and indicators require calibration. This can be achieved using special NPL standards of appropriate values. How these reference standards are used to determine the effective magnetic field of the instruments probe will be presented and discussed. A method of calibrating the inserts used in the permeability indicator will be presented and a number of considerations when using the commercial instruments discussed.
Item Type: | Conference or Workshop Item (UNSPECIFIED) |
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Keywords: | magnetic permeability, NPL reference standards, mass metrology, OIML R111 |
Subjects: | Electromagnetics Electromagnetics > Electromagnetic Materials |
Last Modified: | 02 Feb 2018 13:17 |
URI: | http://eprintspublications.npl.co.uk/id/eprint/2175 |
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