Design and verification of a custom electrostatic probe used to measure surface charge densities of dielectric materials

Date

2022-05

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Abstract

Unwanted charge can accumulate on dielectric surfaces causing dielectric breakdown or surface flashover that can damage sensitive electronics. Understanding charge accumulation and charge decay can help prevent unwanted dielectric breakdown events from occurring. Electrostatic probes can observe surface voltage; however, commercial probes have a measuring limit of +/- 20 kV. Insulating materials that have become electrostatically charged can easily surpass the 20 kV threshold, making commercially available probes ineffective when measuring a realistic charging limit.

A custom electrostatic probe was designed to surpass the measuring limit of commercially available probes. The custom probe is a coaxial geometry that creates a capacitive voltage divider between the probe and the measuring sample. A probe response function can then be deconvolved from the output of the custom probe using an inverse Wiener filter to obtain a surface charge density. A commercially available probe, the Trek 341B with a 3455ET probe, was used to compare against the custom probe. The Trek probe can measure actual surface potential; by using the potential map acquired from the Trek probe, COMSOL Multiphysics can be used to determine the surface charge density. The surface charge density obtained from COMSOL was used to compare the experimental surface charged density acquired using the post-processing technique developed.

Two different dielectric samples were used to observe how material properties affect surface charge distribution and decay. The samples were PTFE and Acrylic, respectively. The effect charging polarity has on surface charge density and decay was also observed, as acrylic can charge either positive or negative depending on the material used for triboelectric charge. 2D surface charge density maps were measured to observe both distribution and dispersion of charge on a samples surface through time.


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Keywords

Custom Electrostatic Diagnostic Probe, Surface Charge Density of Dielectric Materials

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