Quasi-analytical Design of a Square Helmholtz Coil with Finite Cross-sectional Area as a Magnetic Flux Density Standard

Sakda Somkun, Thepbodin Borirak-Arawin

Abstract

This paper describes a design methodology of a square Helmholtz coil with finite cross-sectional area to be used as a magnetic flux density standard up to 50 mT at NIMT. Magnetic field inside the square Helmholtz coil was considered to be assembled from the magnetic fields produced by every pair of square loops, which were analytically derived from the Biot-Savart law. This design technique, based on physical properties of the copper wires, allows the coil resistance to be easily predicted to match the output characteristics of the DC power supply. Temperature rise in the coil and the decrease of the coil constant due to thermal expansion were also taken into account. The calculated magnetic field was found to be closely agreed with finite element modelling (FEM). A design prototype was constructed and results showed good agreements with the numerical calculation.

Keywords

magnetic flux density, Helmholtz coils, magnetic standard

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IMEKO-TC4-2013-028.pdf

DOI

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IMEKO TC

TC4 - Measurement of Electrical Quantities

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