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Eddy current method (phase sensitive)

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Eddy current method (phase sensitive)

The phase sensitive eddy current method according to DIN EN ISO 21968 is, like the amplitude sensitive eddy current method and the magnetic induction method, a contact measurement method.

 

It is often used to determine the thickness of metallic coatings on mass produced parts (e.g. steel or NF metals) with alternating and very small geometries. How does the phase sensitive eddy current method work? Firstly, a high frequency magnet field is generated by an exciter current. This induces eddy currents in both the coating to be tested and the base material. The varying levels of these eddy currents in the coat and base material enable the measurement of the coat thickness. This occurs as follows: The phase shift “Phi” between the exciter current and the measurement signal on the measurement device is recorded via the probe characteristics – the functional interrelation between measurement signal and coat thickness – and then converted into a coat thickness value.

 

Illustration of the principle of the phase sensitive eddy current method.