The dielectric constant of air has a tempco of about 5ppm/C The variation of the dielectric constant of air with humidity is about + 1.4ppm per %RH. The dielectric constant of air has a pressure coefficient of about 100ppm/atm.
The rapid variations in frequency may be due to variation of fringing capacitances and the capacitance of any air dielectric trimmer caps with humidity. The time constants for the absorption and desorption of water by epoxies and other plastics may be so long that the effects of the variation of water content of circuit board and other plastics surrounding the oscillator components on oscillator frequency are masked by aging. Bruce _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
