ACFM in Detail

ACFM vs Eddy Current

TABLE 2 - SUMMARY OF DIFFERENCES BETWEEN ACFM AND EDDY CURRENT

 
ACFM
EDDY CURRENTS
Crack Depth Measurement without Calibration
Yes
No
Maximum Depth *
about 30 mm
about 5 mm
Crack Length Measurement
Yes
Yes
Crack Detection and Location
Yes
Yes
Signal Variations due to Lift-off
Low (Bx only)
High
Easy deployment in transition region (eg Weld)
Yes
No
Easy to automate probe scanning
Yes
No

* N.B. Depth is the distance down a crack face from a metal surface to the crack tip - not the distance from the metal surface to a buried defect.

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