[time-nuts] Time Dilation tinkering

EWKehren at aol.com EWKehren at aol.com
Wed Mar 22 14:42:16 UTC 2017


I remember a time when some at PBT referred to the HP5065A as their  
precision pressure sensor
Bert Kehren
 
In a message dated 3/22/2017 10:03:58 A.M. Eastern Daylight Time,  
kb8tq at n1k.org writes:

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 at earthlink.net> wrote:
> 
> On 3/21/17 4:29 PM, Hal  Murray wrote:
>> 
>> scmcgrath at 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.
> 
> 
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