In situ Measurement of Capacitors under High Hydrostatic Pressure

The application of pressure tolerant medium- and high voltage electronic circuits in deep-sea environments, requires pretesting of all electrical or electronic components. A laboratory measurement technique is presented with which capacitance can be determined over a range of frequencies while the capacitor is under high hydrostatic pressure, using a pressure vessel, a benchtop impedance analyser and standard consumables. A test circuit and method are presented to demonstrate how to compensate for the parasitic impedances caused by unavoidably long test leads. Experiments were performed to evaluate the method and results are presented to show the observed effect of pressure on capacitance for three different capacitors: metallised film polypropylene, film foil polypropylene and multilayer ceramic.