Electromagnetic testing emt-mft chapter 9b

2.0 Experimental Techniques.
A typical setup for measuring the B-H characteristic of a rod specimen is
shown in Fig. 7. The essential elements are an electromagnet for generating
the magnetizing field, a coil wound around the specimen for measuring the
time rate of change of the magnetic flux, B, in the material, and a magnetic
field sensor, in this case a Hall effect probe, for measuring the magnetic field
strength, H, parallel to the surface of the part. The signal generator provides a
low-frequency magnetizing field, typically of the order of a few Hertz, and the
output of the flux measuring coil is integrated over time to give the flux density
in the material. In the arrangement shown in Fig. 7, an additional feature is
the provision for applying a tensile load to the specimen for studies of the
effects of stress on the hysteresis data. When using a rod specimen such as
this, it is important that the length-to-diameter ratio of the specimen be large
so as to minimize the effects of stray fields from the ends of the rod on the
measurements of B and H.
Charlie Chong/ Fion Zhang