Which environmental factor can primarily distort Eddy Current Testing results?

Humidity can significantly impact Eddy Current Testing results due to its influence on the electrical conductivity of materials and the formation of surface films. High humidity levels can lead to the absorption of moisture on the surfaces being inspected, which in turn can create a resistive layer that affects the accuracy of the measurements. Eddy currents are induced in conductive materials, and any variations in surface conditions, including moisture content, can alter the impedance presented to the testing probe, leading to erroneous readings or inconsistent results.

In contrast, while factors like natural light and surface cleanliness can affect the overall visibility and accessibility of the test area or influence sensor performance, they do not have the same direct and pronounced impact on the fundamental electromagnetic principles utilized in Eddy Current Testing. Operator fatigue can influence the attention and accuracy of testing procedures but does not have the direct physical impact on the testing environment that humidity does.