Measurement of insulation resistance op high quality insulating materials

It bas been customary until very recently to report measurements of volume resistivity high quality insulating materials as greater than some figure such as 10¹⁵ ohm-cm. This was partially due to the lack of proper instruments for measuring the high values characteristic of the better insulating materials such as polystyrene, teflon and polyethylene, but primarily due to the fact that few insulator applications existed until recently which required extremely low direct current leakage. The work with which this paper is concerned was initiated by the Signal Corps Engineering Laboratories as a result of difficulties encountered in various instruments used for measuring high energy radiation such as, for example, the ionization chamber type consisting essentially of a charged capacitor whose charge is neutralized to a measurable extent by ionizing radiation. It is apparent that leakage in supporting insulators which is not constant and low under all operational conditions will cause errors in the measurements.