Electromagnetic Testing - Eddy Current Testing Applications Chapter 5 & 6

(d)
Perform conductivity measurements of the test part. Normally at least
three readings should be taken on each test part to obtain a conductivity
measurement, each reading being taken on a different area. The test
areas should be flat, of sufficient area to avoid edge effects, of sufficient
thickness that the thickness does not affect the reading, and, if a coating
is present, it should be thin enough not to affect the reading. If any of
these conditions cannot be met, with the instrument and frequency being
used, alternative frequency, probe, or instrument which allows these
conditions to be met should be used if this is not possible, a correction
must be determined experimentally for the particular material and test
conditions, and added to or subtracted from the instrument reading.
Charlie Chong/ Fion Zhang