Electromagnetic Testing

For this example, the system parameters are as follows: (a) Unloaded coil
voltage equals 10 V. (b) Test object effective permeability equals 0.3 (c) Test
coil inside diameter equals 25.4 mm (1 in.) (d) Test object outside diameter
equals 22.9 mm (0.9 in.)
η (eta) = d 2 /D 2 , fill factor = (0.9/1) 2 = 0.81
An equation demonstrating coil loading is given by:
E = E o (1- η + η∙μ eff )
Where:
E o = Coil voltage with coil affected by air
E = Coil voltage with coil affected by the test material
η = Fill factor
μ eff = Effective Permeability
Charlie Chong/ Fion Zhang