Final report (draft B) on EUROMET Project No. 446: International comparison of magnetic flux density by means of field coil transfer standards

Abstract

Within the EUROMET Project No. 446 participants from eight European countries have measured the magnetic flux density with frequencies up to 20 kHz generated in a field coil acting as transfer standard. Different methods have been applied by the various institutes to determine the coil constant of the standard and its frequency dependence in ac and dc fields.

Magnetic Calibration System With Interference Compensation

“…Another option is to use a magnetic flux density standard based on a solenoid precisely wound on a quartz-support [17], in this case the achievable accuracy is about 60-ppm B. Calibration of the 60-cm coil system Our coil system ( comprising of one Merritt-coil-quaternion [18] with high homogeneity and two Helmholtz coil. We have done a 3-D FEM simulation (Cedrat FLUX3D) of the Meritt-coils showing that in an area of 12×12 cm 2 the inhomogeneity is below 50 ppm -see Fig.…”

“…Another option is to use a magnetic flux density standard based on a solenoid precisely wound on a quartz-support [17], in this case the achievable accuracy is about 60-ppm B. Calibration of the 60-cm coil system Our coil system (Fig. 1) with overall 60-cm dimensions Corresponding author: M. Janosek (e-mail: janosem@fel.cvut.cz) Digital Object Identifier (inserted by IEEE).…”

CCEM key comparison "Magnetic Flux Density by means of Field Coil Transfer Standard"

“…446 [1]. A field coil of the Garret type [2], [3] was prepared and provided as a transfer standard by PTB acting again as the pilot laboratory.…”

“…A field coil of the Garret type [2], [3] was prepared and provided as a transfer standard by PTB acting again as the pilot laboratory. The single layer coil with a winding length of about 382 mm and a diameter of 122 mm produces a field with a flux density of about 2 mT if it carries the maximum permitted current of 1 The field in the centre region is as homogeneous as necessary to enable NMR measurements by the free precession method even with fields larger than 1 mT. Four return leads, diametrically arranged along the coil and fixed at the same distance from the coil axis, ensure general compensation of field components perpendicular to the coil axis.…”

A reference system for the measurement of low-strength magnetic flux density

“…The lower portion of such a range, down to some 10 À5 T, is of special interest for all measurements dealing with the characterization of soft magnets, but the measuring accuracy is correspondingly low, because of the interference by the environmental fields and the limitations found with the use of quantum magnetometers. In this paper we discuss the development of a reference system for the magnetic flux density m 0 H aimed at covering the range $10 À5 Tpm 0 Hp$1 T. At the core of the calibration procedure is the use of nuclear magnetic resonance (NMR) magnetometers and a standard Garrett coil, previously characterized in an international comparison exercise [2]. The reference sources are realized by means of a stable electromagnet and built-on-purpose Helmholtz coils at high and low field strengths, respectively.…”