Additive Manufacturing (AM), or 3D printing, is a powerful technology that is revolutionizing the way designers create products across many industries. AM technology is severely limited by the lack of effective methods for in situ characterization of multi-material properties and composition during printing. The ability to detect the composition of multi-material printed inks in real time is an emerging need for a wide range of manufacturing applications. In this study, dielectric properties of embedded metal microparticles in a dielectric matrix are measured and characterized as a function of particle size, shape, volume percentage and frequency. Unexpectedly, there was no observation of any percolation threshold. The impedance was found to decrease with the percentage of metal filler as expected. While particle shape seemed to have significant effect on the impedance, there was little to no correlation between particle size and impedance. The resulting data can be used to generate a calibration curve correlating metal loading with impedance or capacitance. We discuss how this data can be used for in situ sensing of local ink composition, which does not currently exist, to facilitate greater control over the resulting properties and functionality of printed materials.