T.O. 33B-1-14-334.3.5 ImpedancePlaneAnalysis.Most eddy current inspection applications have two major problems to overcome. The first is to ignore changes inparameters not of interest during the test; an example is lift-off variation while inspecting for cracks. The second is torecognize valid indications while other changes are occurring. Another way of stating this is that variations in aparameter such as lift-off should not be mistaken for valid defect indications and valid defect indications should not behidden by changes in parameters such as lift-off. Impedance plane analysis, also called phase analysis, is a tool that iseffective in solving these problems.4.3.5.1 PhaseAdjustment.In eddy current instruments with two dimensional displays, the signals displayed can be rotated to align the direction ofchanges caused by the variable of no interest with the horizontal (or vertical, if so desired) axis as shown in Figure 4-31. This is also called phase adjustment and its purpose is to position the response associated with lift-off variations ina direction that does not interfere with the interpretation of responses from variables of interest. The effectiveness ofthis technique increases as the phase difference between lift-off and the variable of interest increases from 0o to 90o.Figure 4-31. Impedance Diagram Showing the Effect of a Crack.
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business
