[time-nuts] Frequency referenced temperature regulator

Bob Camp lists at rtty.us
Tue Nov 9 00:51:53 UTC 2010


Hi

Actually a primary temperature standard (triple point cell) is about the cheapest primary standard you can buy these days. A very good one (~ 0.1 mK) is still in the $1K range.

If you are ok with basic glass work (or know somebody who is) you can make a quite adequate one (~1 mK) for sub $100. 

If only you could build your own Cesium standard for $100 ...

Bob


On Nov 8, 2010, at 7:45 PM, Neville Michie wrote:

> A hint for using peltiers,
> the resistive component in them has a problem with IsquaredR heating
> so that better performance is obtained by running them on filtered DC.
> PWM control works best if it is filtered to DC.
> 
> My choice for temperature control is a glass encapsulated thermistor,
> there are some quite small ones that have very fast response and good ageing
> performance.
> 
> Diodes and transdiodes also make good sensors and can come in good packages
> with rapid response.
> 
> For us the best temperature standard is ice point and that is only good to 10 mK.
> Anything better means a trip to a standards laboratory.
> 
> However, one is to be applauded for trying to link temperature to frequency,
> 
> cheers,
> Neville Michie
> 
> 
> On 09/11/2010, at 2:04 AM, Poul-Henning Kamp wrote:
> 
>> 
>> I'm contemplating building a small temperature control enclosure for
>> testing various electronics.
>> 
>> I have a handful of peltiers suitable for the purpose, and was
>> pondering the right control mechanism.
>> 
>> Most people would reach for a NTC, put it in a wien-brige etc etc.
>> 
>> But since I happen to have access to much more stable frequencies
>> than voltages, I thought of a different way:
>> 
>> 1. Mount a X-tal-osc with really lousy tempco inside the enclosure.
>> 
>> 2. Compare its output to a stable reference frequency.
>> 
>> 3. Use the output of the phase comparator to drive the Peltier.
>> 
>> It is basically a PLL where temperature is used as EFC...
>> 
>> Has anybody tried that ?
>> 
>> -- 
>> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
>> phk at FreeBSD.ORG         | TCP/IP since RFC 956
>> FreeBSD committer       | BSD since 4.3-tahoe
>> Never attribute to malice what can adequately be explained by incompetence.
>> 
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