[time-nuts] Fury - Rubidium
Don @ True-Cal
True-Cal at swbell.net
Wed Jul 28 16:18:44 UTC 2010
I would like to take advantage of the Fury TempCo capabilities when using an Rb. I have been looking for the thru-hole pad which you say is next to C67 but I can't find a C67. Consider that I am over 60 and eyesight is challenged but I have found C68 with nearby pads. Can you give us some additional components nearby to zero in on this allusive component. Thanks!
----- Original Message -----
From: SAIDJACK at aol.com
To: time-nuts at febo.com
Sent: Tuesday, July 27, 2010 9:07 PM
Subject: Re: [time-nuts] Fury - Rubidium
yes the pads are there, you can use the through-hole pad right next to C67
and a standard ground pad for the Thermistor. There will be 10.5V across
the thermistor. Connect the thermistor to your Rb case.
You should be able to connect two 10K Thermistors in parallel to get a good
reading without excessive self-heating of the thermistors, while
generating enough current through them that can be measured by the ADC.
You can check the thermistor current using the meas? command. If the
thermistor is not drawing enough current for the ADC, then simply place a 2.2K
resistor in parallel to it.
The software needs to be enabled to support measuring and applying a tempco
correction, by default I think the boards were shipped with only aging
Us the following command to enable tempco correction:
Check the settings with:
The first number is the mode (0 is all off, 1 is aging only, 2 is aging and
tempco correction). The second number is the memory usage, 288 points in
this case. The third number is the sensing frequency in seconds, so 10
minute intervals in this example. 288 points * 10 minutes is 48 hours of memory.
The fourth number is the maximum phase offset allowed for a sense point,
in this case +/-50ns. The last item is the required frequency error
estimate for a sense point, in this case +/-0.05ppb.
In a message dated 7/27/2010 17:07:31 Pacific Daylight Time, smace at intt.net
Said, Did the OEM units (from way back) ship with an open pad for the
thermistor? I thought that wouldn't work unless it was drawing oven
current from the Fury. It would be neat to add some tempco into the mix
instead of just trying to shield it from HVAC cycling. The particular
LPRO-101 that I'm using now, doesn't seem to be as sensitive as others
to temp. I was using a different LPRO originally and when I plotted the
Fury board temp sensor with GPSCON you could see the impact of the
cycling, now with this one you would be hard pressed to pick it out.
The X72 was very sensitive to temp changes, EFC tracked the temp quite
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