Measurements of the effective dielectric permittivity of suspensions

A technique to measure the effective dielectric permittivity of suspensions is described. In these measurements, test powders are suspended in petroleum jelly at any desired voidage. The technique is illustrated using spherical glass beads of various sizes, a catalyst powder with and without water contamination, metal spheres, and metal flakes. For each suspension, a model is selected to fit the data. In the context of metal flakes, a model is derived for the effective dielectric permittivity of a suspension of ellipsoids in an electric field of random orientation. For complex powders, the technique is shown to represent a necessary step towards quantitative measurements of voidage using capacitance diagnostics.