[time-nuts] Aging rate of crystals
Bruce Griffiths
bruce.griffiths at xtra.co.nz
Mon Feb 18 05:24:54 EST 2008
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
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