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Point probes: A new generation of magnetic sensors for the measurement of local magnetic fields

: Sheikh Amiri, Meisam; Szielasko, Klaus; Altpeter, Iris; Boller, Christian; Fischer, Dieter; Hahn, Jens


European School of Materials Engineering -EEIGM-:
6th EEIGM International Conference on Advanced Materials Research 2011 : 7-8 November 2011, European School of Materials Engineering (EEIGM), Nancy, France
Bristol: IOP Publishing, 2012 (IOP conference series. Materials science and engineering 31)
Paper 012021
International Conference on Advanced Materials Research (AMR) <6, 2011, Nancy>
Conference Paper
Fraunhofer IZFP ()
point probe

In several magnetic Non-Destructive Testing (NDT) methods, the local measurement of the magnetic field inside the material is required. Moreover, looking at difficult part geometries, magnetic field sensors have to be small enough in order to reach the measuring position. The most-used magnetic field sensors are coils, Hall-effect sensors, flux gates and magnetoresistive sensors. However, regarding the industrial application, those sensors are often packaged and cannot be placed close enough to the measuring position.
As part of an ongoing research project funded by the German Ministry of Economics and Technology (BMWi), a new kind of magnetic field sensor was developed and used in order to measure the strength of remanent magnetic field spots. This so-called 'Point Probe' is based upon a needle-shaped ferromagnetic core having a primary coil as a magnetic field source and a secondary coil as an inductive pick-up. This contribution describes the details of the sensor design and its operating principle. The sensitivity of the measured signals for local magnetic fields is described. Finally, a method for nondestructive hardness estimation of materials by using the Point Probe is presented. The results show a high correlation between hardness and a new coercivity-dependent testing parameter.