The DCM-2 is a modern microprocessor based instrument for measuring crack depth in metals undergoing materials testing. Building on the success of the DCM-1 this unit takes on board customer comments and suggestions, as shown in its impressive features list.
It utilises the pulsed current potential drop method (DCPD) which is an established technique also covered by the ASTM 647 standard. The technique involves passing a constant current through the metal under test and measuring the resultant voltage drop that is created across the specimen. The presence of a growing defect will alter this voltage and by suitable calibration, a measure of the defect depth can be obtained. DCPD is generally regarded as easier to set-up than ACPD, but care is required to attain comparable crack depth resolutions due to the extra opportunity for experimental noise.
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