Simultaneous Absolute and Differential Operation of Eddy Current Bobbin Probes for Heat Exchange Tube Inspection
Figure 4-6
Figure 4 — Computer simulation of absolute anomaly signals from (a) a true absolute probe; (b) an absolute/differential probe with drive current in one coil 180 degrees out of phase with the other, and (c) an absolute/differential probe with drive current in phase in both coils.
Figure 5 — Laboratory measured differential probe signals with drive current (a) in one coil 180 degrees out of phase with the other; (b) in phase in both coils. The lower traces are strip chart displays of the respective imaginary (left) and real (right) components of the eddy current probe signals.
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Figure 6 — Laboratory measured absolute anomaly signals from (a) a true absolute probe; (b) an absolute/differential probe with drive current in one coil 180 degrees out of phase with the other; and (c) in phase in both coils.
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