The reason I'm asking this is because I can't figure out from
your descriptions or from the plots a clear way to distinguish
between unintended oven current-induced changes in applied
EFC voltage vs. direct temperature-induced changes in OCXO
frequency output. It seems both would have the same effect.
I wonder if there is a clear test that would tell you one way or
the other.
Maybe change oven voltage quite suddenly. That should cause
a change in oven current. If the measured EFC voltage or the
measured frequency also changes suddenly then that might
indicate it's not really temperature that's being compensated for.
Can I do these tests on my double oven Fury? Or is this something
only for the single oven version.
/tvb
----- Original Message -----
From: saidj...@aol.com
To: time-nuts@febo.com ; t...@leapsecond.com
Sent: Thursday, February 05, 2009 10:22 AM
Subject: Re: [time-nuts] Tbolt temperature sensor
Hi Tom,
I re-connected the antenna to that unit just now, so it is now GPS locked
again.
Forgot to mention: another reason why ground loop currents for these single
oven units are not an issue is that the current changes very little with
temperature. In the plots you can see that the OCXO current is typ. less than
50mA, and the variation is typically less than 4mA peak to peak.
A 4mA change is a very small change to affect ground-loop induced voltage
offset errors across the ground plane, OCXO pin, etc. Nevertheless we do Kelvin
sensing to avoid any issues for ovens with higher current variations.
bye,
Said
In a message dated 2/5/2009 09:32:31 Pacific Standard Time, saidj...@aol.com
writes:
>In your plots the EFC correction seems to match so well with
>oven current (without clear evidence of the usual thermal lag)
>could it be that what you're seeing, and what you're correcting,
>is not resonator temperature at all but simply the voltage offset
>due to ground currents?
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