[time-nuts] OCXO Adjustment Question -- Oven Cycling

Magnus Danielson magnus at rubidium.dyndns.org
Thu May 9 07:00:17 EDT 2013

On 05/09/2013 01:52 AM, Bob Camp wrote:
> Hi
> Clip a DVM on the power leads of the OCXO and see if the supply swings at the same rate as the frequency. It doesn't have to be anything fancy. If the problem is the supply, the swing will be obvious with>= 3 1/2 digits of resolution.
> To be *really* sure, put a DVM in series with the oven supply lead and watch the current. That will also tell you if it's cycling due to an internal problem.

I've seen ovens that had this issue, and it out of luck that I saw the 
current fluctuate on power-up (as the HP supply had both voltage and 
current reading) and then I hooked up a DMM in series and could see the 
same fluctuation in the more fine-grained structure too. Turned out to 
be a badly designed oven, or rather, the original design was good 
enough, but then transferred to another product with new conditions, it 
was no longer stable.

It can be good to understand what that "bump" comes from, it can be a 
severe systematic flaw, but ADEV doesn't help you to understand what it is.


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