Eddy current testing is different from other non-destructive testing method in one important respect: the equipment used, in particular the probes, is specific to the inspection task. Eddy current testing is therefore inherently flexible. In order to get the best results, it is vitally important to choose the optimum equipment for each task.The notes below offer a guide on to how to select the right probe for your application. The selection depends on many factors:
Define the Task
Is Eddy Currents the best modality for the inspection? Points to considerThe component to be inspected, material type – Is it Conductive?The size, location and orientation of the flaw to be found.Access in inspection area – Probe shape and size.The inspection environment – Probe can be designed to withstand a variety of temperature condition, oily surfaces, to be waterproof or ware resistant.
Once you have defined the inspection task there are 4 possible choices involved in selecting a probe:FrequencyShielded or unshielded.Probe size and configuration.Type of instrument to be used.
The aims when selecting a probe are:To ensure that an eddy current of sufficient strength passes through the volume of the component under inspection i.e. Frequency.To maximise the signal caused by flaws of interest.To minimise effects caused by other features - e.g. edge effect, geometry etc.