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.