[time-nuts] How to accurately measure an oscillator's temperature.

EWKehren at aol.com EWKehren at aol.com
Thu Apr 24 13:42:46 UTC 2014

 I am not sure if you want to measure temperature or control a fan. To  
measure there are many options depending on how much money you want to spend. 
To control I suggest either a LM 335 or a NTC resistor. I have worked  
extensively with both and for measuring I have now downsized to a YSI. Used to  
have a HP XTAL thermometer.
Spend a lot of time and money on temperature control on Rb's and OCXO's all 
 part of GPSDO's and have come to the conclusion on OCXO's a combination of 
 thermal Isolation and thermal mass is the best solution and on Rb's fans. 
Spend  a year playing with concepts on the FE5680 with all kind of fans and 
heat sinks  and aluminum shapes till it hit me the answer was right in front 
of me. In my  opinion a fan/heat pipe out of an old laptop is the cheapest 
and best solution,  low cost, low noise, no special assemblies and easy to 
control. Use an aluminum  plate as the interface or use the bottom plate 
directly and use one of the  bottom screws to hold your sensor it is internally 
directly tied to the spine of  the Rb. Wide variety available on ebay under 
CPU fan.
Bert Kehren
In a message dated 4/23/2014 10:38:11 P.M. Eastern Daylight Time,  
albertson.chris at gmail.com writes:

I have  both an OCXO and an FE-5680 Rb oscillator and I'd like to track
their  temperatures.

What is the best why to measure?   Maybe each  has a different best method

The OCXO is just a small steel can.   Is measuring the steel can temperature
the best why to go.  Epoxy some  kind of sensor to it?

The Rb is mounded to a large heat sink and there  is a fan.  I want to
control the fan so as to keep the Rb temperature  constant.

In both cases I tried using TMP36 three terminal sensors and  just got
noise.  The reported temperature was up and down more than  2C.    The fan
controller just chases noise.

BTW the fan  based temperature control is effective.  The FE5680 gets very
warm in  it's box but if I give the 12V fan even 8 volts the heat sink
quickly  cools.  I want to throttle the fan to keep the Rb at  constant
temperature but the temperature data I'm getting is not very  good.

The problem I think is that any sensor I have is on the outside  of the
oscillator and is effected by cooling air   What are  others doing?   What's
the best kind of sensor.


Chris Albertson
Redondo Beach,  California
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