Proficiency Test Reference Lab:

David L. Ellis Co.

The David L. Ellis Company establishes the artifact reference value of hardness on the Rockwell C Scale for the test blocks that MeasurePT uses in its proficiency test, Hardness #1.

This NVLAP and A2LA accredited calibration laboratory regularly performs intercomparisons for hardness measurements with NIST (USA), NPL (UK), PTB (Germany) and IEN (Italy).  The approximate uncertainty associated with establishing hardness values of test blocks is 0.30 - 0.40 hardness units for the Rockwell C scale.