Comparison of vibrating and fixed Kelvin probe for non-destructive evaluation

The electrical potential over the surface of the multi-layer object was measured with the classic vibrating Kelvin probe and the fixed probe with the charge measuring electrometer. The study demonstrated that while both methods provide comparable data for the space charge located on the external surface of the object, the fixed, static probe is notably more sensitive (in some instances >6 times) than the vibrating Kelvin probe in the case of the space charge source buried under the layer with the slow polarization. These results correlate with spectra of dielectric loss, which were measured for the evaluated samples. Thus, the advantage of the fixed probe for non-destructive evaluation of multi-layer structures, for example - detection and localization of corrosion under the paint, or the remote measurement of the electric potential in the conductor through the isolation, is demonstrated.