Quality Control Of Permanent Magnets For Industrial Applications: Integrating Magnetic Field Mapping And Crack Detection

The characteristics of permanent magnets must be carefully controlled when applied in automotive, industrial and consumer products. In this paper we present a novel measurement system for quality control of permanent magnets by integrating magnetic field mapping and crack detection. The novel system is introduced that combines in a single device the features of a magnetic field mapper, the eddy-current measurements and a touch stylus. The magnetic field sensitive area of the 3D Hall probe is 100x100um; the selectable measurement range is 50mT-2T; the probe positioning accuracy is 2 mu m/0.02 degrees; and the measurement accuracy is 0.1%. The angular error of the sensitivity vectors of the 3D Hall probe are less than 0.1 degrees. The system integrates various tools for in-situ automatic calibration, e.g. the precise determination of the magnetic field sensitive volume. The mapping system allows a smart and easy interchangeability of various measurement probes. Further in this paper we present several industrial applications that apply the novel measurement system for quality control of their permanent magnets and magnetized and non-magnetized parts: one application is the quality control of segment magnets for rotors; another application is crack detection in magnetized and non-magnetized parts; further applications include high-resolution magnetic field mapping of an area around permanent magnets in the form of a disc, block or electronic circuit PCB's such as smartphones or tablets.