Low-Cost Return-Voltage Measurement of Dielectric Absorption in a Multilayer Plasticized-PVC Capacitor with a Quantified Instrument Bound

Abstract

Return-voltage measurement (RVM) has proved useful for characterizing slow polarization in insulating dielectrics, but normally requires a laboratory electrometer. In this work, an RVM front end was assembled using a single, commercially available, off-the-shelf CMOS operational amplifier (with a typical input bias current of 10 fA) and a handheld multimeter, then applied to a multilayer capacitor made of ordinary plasticized poly(vinyl chloride) (PVC) with a capacitance of 14.75 nF. The results showed that the open-circuit voltage, following poling at 9.56 V for anywhere from 60 to 1800 seconds and a 10-second short circuit, reached a maximum, Vmax at time tmax, before decaying. Vmax increased from 0.584 ± 0.009 V to 1.295±0.008 V with increasing poling time (run-to-run standard deviation ≤1.5%), while tmax was delayed (from 48 ± 5 s to 66±5 s) and the subsequent voltage decay became slower. Control runs with no poling identified a background of 0.097 ± 0.005 V. A single-layer prototype with a capacitance of 0.15 nF could not resolve the return voltage because of drift, implying that a specimen capacitance of 14.75 nF is sufficient to resolve return voltage with a cheap buffer. Using a polypropylene reference capacitor and following the same protocol, the instrumental contribution was 4.5 ± 0.1 mV (less than 1% of the smallest Vmax measured).