11
Coupling. Light-weight sample must be firmly coupled with a heavy base
plate. Both coupled surface must be flat and smooth. The impact direction
must be vertical to the coupled surface. When the sample is a big plate, or
long rod, it can be deformed and become unstable, even though its weight
and thickness is within allowable ranges, and accordingly, the test value
may not be accurate. So the sample should be reinforced or supported at
its back.
AVOID any object that has a strong Magnetic Force.