The effect of humidity on the calibration of air-type capacitance standards

This paper describes our observation of the effect of humidity on a four-terminal-pair (4TP) air capacitance standard set. A standard set (Agilent 16380A) has been monitored four fourteen days at 1 kHz frequency using an AH 2500A capacitance bridge. Consistent increment of measured capacitance was observed for all the capacitors in the set as the humidity increases. In addition, the analysis on the humidity-dependent capacitance reveals that the capacitance value follows the humidity changes with a delay of about 0.7 day.