[time-nuts] Thunderbolt temperature measuring

[Arnold Tibus]

Hi Mats,

welcome!

As you are working already with a wired interface, I think 
you don't risk anything when trying it - you can not really lose anything, 

I think you may have a problem to see a difference because 
the missing reference.measurements. I do not expect a EMC problem, 
but it's as well not impossible. At least you will get the true 
OCXO's surface temperature (which should be somewhat higher 
due to the heat dissipation of the oven).

The thermal coupling via the glue I would not see a point to think about 
because the plastic case of the DS1620 chip does isolate anyway more 
then the thin glue will do and the add.  in relation to the total coupling
factor will be negligable. 

But how you will verify the effects and judge about the results? 
As already mentioned by the experts perhaps nothing will be seen, 
because other environmental effects may mask the (small) differences...

About your actual temperature readout. My experience is that TB 
does show more or less 7 to 10 deg. C above the environment with
a stabilized box - did you have a so low room temperature? 
(My TBs does report actually 34 to 36 deg. C at ~24 de. C. environment)

Congratulation to the already working repair solution, 
good luck for further actions!

regards

Arnold


On Sun, 26 Jul 2009 22:14:20 +0400, Mats Engstrom wrote:

>Hi,

>I've been lurking on this list for a long time but now it's time to unlurk.

>I don't remember if it's appropriate to introduce oneself on this
>list, but I'll do it anyways. :)

>I've been tinkering with electronics for some thirty odd years now -
>mostly just as a hobby but also occasionally semi-professionally.
>Most of my stuff is microcontroller based (AVR and/or PIC) - mostly in
>assembly,but C is also ok for some projects - higher level languages
>are for whimps :).  I'm Swedish by birth but living and working in
>Dubai in the IT/Finance industry since a couple of years.

>I just bought a Thunderbolt from flyingbest at Ebay to use as a nice
>timebase for my counters and signal gens.  I discovered that it had a
>bad DS1620 tempsensor that always reported -55 C so I replaced it with
>a thru-hole version that I happened to have some spares of. I then got
>a nice 24.xxxxx C temperature readout in Lady Heather. (When I tested
>the tbolt without the DS1620 it reported a temperature between -0.5 to
>-1.5 C)

>Now I'm finally coming to the question: Since I'm using a thru-hole
>version of the DS1620 and have to use cables between the chip and the
>circuit board I could possibly extend the cables a bit so I can glue
>(with a non termo-insulating glue) the chip onto the ocxo itself to
>have a tighter coupling between them.  Would that improve the
>stability or is it better to just measure the air temperature in the
>box?

>/mats

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