scmcgrath@gmail.com said: > However CSAC not subject to barometric effects as Rb units are Does anybody tried to measure CSAC vs pressure? -- These are my opinions. I hate spam.

On 3/21/17 4:29 PM, Hal Murray wrote: > > scmcgrath@gmail.com said: >> However CSAC not subject to barometric effects as Rb units are > > Does anybody tried to measure CSAC vs pressure? > > > The physics package in a CSAC is a vacuum, so it probably won't make much difference. But, as a practical matter, I have a system with a CSAC going through thermal vacuum testing as I write this. We'll get some test data and we can compare the frequency against GPS and a OCXO at room temp/pressure, and at various temps in vacuum. Remind me in 2 weeks, and I should have the data plotted.

Hi In this case, the vacuum might work against you. You change the pressure outside the package and you get a flex. Flex translates to dimensional changes. That gives you a frequency shift. People make absolute pressure sensors this way :) Rb’s are by no means the only frequency standard impacted by this effect. Precision OCXO’s have the same issue. If you had enough room inside the package, you could do a “can in a can” sort of approach. The outer vacuum sealed can flexes. The inner vacuum sealed can does not see anything. You don’t eliminate the sensitivity this way, you do attenuate it quite a bit with each layer. The question then becomes - is is worth the increase in size? Since the pressure sensitivity is well below many other environmental factors …. probably not. Bob > On Mar 22, 2017, at 1:04 AM, jimlux <jimlux@earthlink.net> wrote: > > On 3/21/17 4:29 PM, Hal Murray wrote: >> >> scmcgrath@gmail.com said: >>> However CSAC not subject to barometric effects as Rb units are >> >> Does anybody tried to measure CSAC vs pressure? >> >> >> > The physics package in a CSAC is a vacuum, so it probably won't make much difference. > > But, as a practical matter, I have a system with a CSAC going through thermal vacuum testing as I write this. We'll get some test data and we can compare the frequency against GPS and a OCXO at room temp/pressure, and at various temps in vacuum. > > Remind me in 2 weeks, and I should have the data plotted. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

On 3/22/17 4:28 AM, Bob Camp wrote: > Hi > > In this case, the vacuum might work against you. You change the pressure outside > the package and you get a flex. Flex translates to dimensional changes. That gives you > a frequency shift. People make absolute pressure sensors this way :) Rb’s are by no > means the only frequency standard impacted by this effect. Precision OCXO’s have the > same issue. > > If you had enough room inside the package, you could do a “can in a can” sort of approach. > The outer vacuum sealed can flexes. The inner vacuum sealed can does not see anything. > You don’t eliminate the sensitivity this way, you do attenuate it quite a bit with each layer. > The question then becomes - is is worth the increase in size? Since the pressure sensitivity > is well below many other environmental factors …. probably not. > The CSAC is a can within a can (or more properly, the physics package is inside a sealed can) but I don't know if there's vacuum inside the can.

Hi The outer can is at best only “sort of” sealed. Bob > On Mar 22, 2017, at 10:58 AM, jimlux <jimlux@earthlink.net> wrote: > > On 3/22/17 4:28 AM, Bob Camp wrote: >> Hi >> >> In this case, the vacuum might work against you. You change the pressure outside >> the package and you get a flex. Flex translates to dimensional changes. That gives you >> a frequency shift. People make absolute pressure sensors this way :) Rb’s are by no >> means the only frequency standard impacted by this effect. Precision OCXO’s have the >> same issue. >> >> If you had enough room inside the package, you could do a “can in a can” sort of approach. >> The outer vacuum sealed can flexes. The inner vacuum sealed can does not see anything. >> You don’t eliminate the sensitivity this way, you do attenuate it quite a bit with each layer. >> The question then becomes - is is worth the increase in size? Since the pressure sensitivity >> is well below many other environmental factors …. probably not. >> > > The CSAC is a can within a can (or more properly, the physics package is inside a sealed can) but I don't know if there's vacuum inside the can. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.