Challenges and Pitfalls of PEA Calibration with Fast Charge Accumulating Materials

One of the most used techniques for the detection of space charge is the Pulsed Electro-Acoustic (PEA) method. Calibration of signals is usually done by investigating a “reference” signal, which must be acquired while the material is free of accumulated charge. Often one of the first acquisition obtained from the system during polarization is used. While this is usually a reasonable choice, testing on materials capable of very fast charge accumulation is more and more often encountered, and most of the commercially available systems are not able to extract a calibration signal before charge accumulation. Authors propose a procedure to correctly obtain a calibration pulse in presence of fast charge accumulating materials, with standard equipment. Experimental validation was done on polyimide samples tested at 90° C with electric fields from 10 to 50 kV/mm, capable of fast charge accumulation, demonstrating how to correctly obtain a charge-free calibration pulse within 0.3 s. The results obtained were confirmed by measurements from a custom system with non-standard fast acquisitions capabilities.