Behavior and frequency dependence of AC-DC high voltage transfer standard under humidity step changes

AC-DC difference from different type of AC-DC transfer standards placed under step humidity change conditions were measured at 200 V, 600 V, and 1 kV in the frequency range from 40 Hz to 100 kHz. The measured results have shown that the humidity affects the AC-DC difference of a high voltage AC-DC transfer standard significantly at high frequencies and that a first order differential equation can be used to model the behavior. The humidity coefficients of the model are found to be frequency dependent and the time constants are related to the change of the humidity. Furthermore, the humidity effect was also found to be device dependent due to the construction of the range resistor. It will imply consequences for the measuring procedures of further international comparisons in the field of AC-DC transfer.