New aspects concerning isothermal current and voltage measurement on electrets

Isothermal current and voltage measurements were done on poly(ethylene terephthalate), (PET), to obtain information about charge storage and discharging current mechanism. The discharging current has three characteristic zones. The first zone fits well with the Maxwell relaxation function. The last zone offers important information concerning the most stable stored charge. The discharging of the sample on internal resistance plays a minor role. If the external resistance is higher than the internal resistance, the voltage on the sample increases in time and the logarithmic plot is a straight line for not too long Fp time intervals. A new experimental procedure is proposed for measuring the most stable stored charge. The total charge flowing through the circuit during the polarization is almost equal with the total charge released from the sample