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
[email protected] | 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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