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Typical applications for the EMHT40 include measuring the surface and coating hardness of
installed machines and components, die molding surfaces and bearings. Up to 1250 test
results can be stored in the EMHT40's memory and ported to a PC for display as an Excel table
or graph.
Leeb hardness testing produces so-called Leeb hardness values for a target metal (the work
piece). To measure hardness, the user cocks a spring-loaded, pen-shaped plunger and
squeezes a trigger at one end of the instrument to fire the plunger (the impact device) against
the work piece at the other end. A permanent magnet close to the work piece senses the
impact and generates two voltages: one proportional to the plunger's impact velocity and the
other proportional to the velocity with which the plunger rebounded from the work piece.
To determine the target's Leeb hardness value—a parameter designated HL—an algorithm
within the EMHT40 divides the voltage representing the plunger's rebound velocity by the
voltage representing its impact velocity and multiplies by 1000. The following formula is used
for the computation:
HL=1000 × (V
/V
)
b
a
-3-
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