Electromagnetic Testing - Eddy Current Testing Applications Chapter 5 & 6

5.1.3.3 Reference blocks
It is essential to use a reference block containing one or more known real or
artificial surface flaws to check that the equipment is functioning satisfactorily
and to set the gain to an appropriate level. A typical reference block for
surface flaws is a block of material of conductivity similar to that being tested,
with three spark-eroded slots across one face (see FIG. 5.3), The slots are
0.2 mm, 0.5 mm, and 1.0 mm deep respectively, An aluminium alloy
reference block, usually manufactured from aluminium alloy 7075-T6, is
suitable for use when testing all aluminium alloys, brass, and other materials
of similarly relatively high conductivity, it can also be used for testing
magnesium alloys, but because their conductivity is somewhat lower, a
magnesium reference standard is preferred, Carbon steel, stainless steel, and
titanium alloy reference blocks are also available, and the appropriate block
should be used when testing these materials.
Charlie Chong/ Fion Zhang