Arbitrary waveform impedance spectroscopy for accurate contact-free dielectric characterization

Abstract

Solid dielectric material characterization is commonly performed through measurement of dielectric frequency response. A technique, called arbitrary waveform impedance spectroscopy (AWIS), has been developed as one of its modified versions. It is capable, among other features, of obtaining a broad dielectric response spectrum from one single measurement, provided the applied test voltage is rich in harmonic components. As AWIS is a technique, rather than an instrument, it can be optimized to reach signal to noise ratio in the 106 range. However, both the electrode arrangements as well as the accuracy of the measurement setup limit the precision of the characterization. An air reference method and a contact-free electrode arrangement are presented in this paper for enhancing the dielectric characterization accuracy through avoiding problems introduced by electrode contacts. It is shown that by performing a calibration with electrode gap filled with air under the same conditions as the material is tested, the air reference method can improve the measurement accuracy substantially. This type of approach also eliminates the need for a detailed model of the analog measurement circuit. In conjunction with the contact-free measurements and harmonic-rich waveforms, the approach allows for avoiding complicated and time-consuming sample preparation procedures. Both the measurement methodology as well as the electrode arrangement are presented and evaluated by comparing results obtained with different instruments.