[1C2] Multi-point calibration of a portable coercivity meter using BH curve analysis for improved accuracy
J Salas¹, Z Chen¹, R Lyu¹, D Brunt² and D Ryan²
¹Manchester Advanced Intelligent Equipment Research & Innovation Centre (MAIERIC) Ltd, UK
²National Physical Laboratory (NPL), UK
Magnetic coercivity in steel, which measures its resistance to demagnetisation, is strongly linked to its structural properties. A portable coercivity meter based on pulsed excitation was developed for non-destructive assessment of metallic plates. The measurement strategy allows single side 2D scanning of large samples, minimal sample preparation and fast measurements. However, the measurement strategy is not standardised. An initial calibration method to traceable coercivity was performed by assigning the system’s measurement result to coercivity, ie based on a single quantity, which can limit accuracy. An experimental measurement set-up has been devised in collaboration with the National Physical Laboratory (NPL) to establish a comprehensive set of reference values, derived from full BH curves, for more accurate calibration. The NPL team had previously measured bar-shaped samples and extended to rectangular plates. This work presents the multi-point relationship between the portable meter and the BH curve data obtained by standard methods. After calibration, there is good agreement between both systems. Moreover, the system limitations can be explained. Results cover plates with thickness up to 35 mm and a coercivity range from 500 A/m to 2000 A/m.
