Silicon rubber is quite transparent to water vapour, at least in the concentrations that are important to the HP 10811. The seal on the screw will only slow the response of the oscillator to humidity. Epoxy is a much better barrier but not perfect. Vapour barriers must be perfect. Water vapour adheres to oxygen atoms, so has an affinity to all metals which have an oxide film. It will also adhere to quartz being SiO2. The glass frequency trim capacitor is a good candidate for humidity sensitivity, but so are all the insulating materials. Solder seals are good against humidity as are glass to metal seals. The way to make a HP10811 immune to humidity is to seal it in a metal container with glass leadthrough seals after it has been flushed with dry nitrogen for a few days. Another method is to seal a small quantity of P2O5 in it as a humidity "getter". An added improvement is to wind two platinum wires on a P2O5 containing fibre glass pad, and electrolyse any water absorbed to oxygen and hydrogen gas after it is sealed. Vacuum tube sealing and evacuation works well. cheers, Neville MIchie
On 20/07/2008, at 8:54 PM, Mike S wrote: > At 01:17 AM 7/20/2008, Ed Palmer wrote... >> If their intent was to hermetically seal the oscillator, why would >> they >> leave the screw in the front that covers the adjustment hole (which >> nobody could possibly get to!)? Would the seal around the screw be >> good >> enough to make it worth the effort to seal the rest of the unit? > > That screw has a silicone (?) o-ring on it. Why do you think that > wouldn't make a sufficient seal? > > > _______________________________________________ > 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. _______________________________________________ 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.
