BH Loop or Hysteresis Loop plotting machine is capable of plotting magnetisation curves at various frequencies (AC measurements) or at near zero frequency (DC measurement). Various properties such as permeability, coercivity, watt loss etc are measured using closed loop geometries such as washers (also known as lamination).
Main advantage of BH curves is it enables the user to know all important magnetic properties at any given magnetisation level. Hence it is not only used as a qualifying parameter in the inspection plan but also used to fine tune manufacturing processes.
Only drawback is its limitations on using washers (closed loop geometries) for the measurements.