Electromagnetic Testing Chapter 3- Electromagnetic Testing

Coil design can be an important design consideration in maximizing the
signal-to-noise ratio. A self-compensation differential coil compensates for
minor variations in diameter, chemical composition, and hardness. Circuits
that tend to minimize the effects of insignificant variables usually provide
signal amplitude, phase, or frequency compensation. Phase (signal timing)
analysis is frequently used to separate conductivity, permeability, and
dimensional variables. Higher test frequencies tend to minimize the effect of
varying test part thickness.Test frequency should be selected on the basis of
part thickness, the desired depth of penetration, and the purpose of the
inspection. Increasing circuit gain will decrease the signal-to-noise ratio if all
other test parameters are held constant.(?)
Charlie Chong/ Fion Zhang