[time-nuts] High accuracy temp controller ckt

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And if you are not in a well air conditioned room....
Gilles.

Envoyé de mon iPad

> Le 12 juil. 2019 à 18:12, Javier Herrero <jherrero at hvsistemas.es> a écrit :
> 
> Hello,
> 
> A TEC is good if you want to maintain the resistors at 25ºC, that seems the zero TC point for some precision low TCR resistors (for example, the Vishay VFCP or VSMP series)
> 
> Regards,
> 
> Javier
> 
>> On 12/7/19 10:06, Dr. David Kirkby wrote:
>>> On Fri, 12 Jul 2019 at 08:07, Bernd Neubig <BNeubig at t-online.de> wrote:
>>> 
>>> AXTAL has a miniature oven for heating precision resistors or other
>>> components to a constant temperature. It is housed in a small DIP8 package.
>>> See attached AXR135 data sheet.
>>> Optionally this device can be offered unsealed, ready for inserting the
>>> component by yourself
>>> 
>>> Regards
>>> Bernd
>> 
>> The resistors I am using are made by Caddock, are 1 M ohm & 10 M ohm, 0.01%
>> tolerance and 5 ppm / deg C. They are much too large to fit in a DIP8
>> package. A quick check with a ruler indicates that the 10 M ohm is 38 x 12
>> mm and the 1 M ohm is 19 x 10 mm.
>> 
>> A quick photograph shows this half finished project. Unfortunately, even
>> before I have finished it, I am wishing I had done a better job. However,
>> my original reason for doing this was to check the stability of a data
>> acquisition unit before sending it to Keysight. I think this will be good
>> enough for that, but I could certainly have done a job with some thought.
>> 
>> The thermocouple is just meant to be a temperature sensor that dissipates
>> no power. A thermistor or RTD buried in the polystyrene would have just got
>> hot. The resistors should not get hot, as the power dissipated will be
>> under 1 uW.
>> 
>> I also intend putting in a 100 M ohm resistor, but the specification of
>> that is much poorer (5%, 100 ppm/ deg C. )
>> 
>> I partially read the paper mentioned. I note that the authors used a thermo
>> electric cooler (TEC) as they wanted get low temperatures. I assume that
>> for crystals or resistors dissipating little heat, a TEC would be
>> unnecessary, and just a resistor acting as a heater would be fine. But will
>> read some of the references. Obviously for controlling a crystal
>> oscillator, or my resistor, stability is most important, whereas for the
>> authors of the paper, stability was not their major concern.
>> 
>>> --
>> Dr. David Kirkby,
>> 
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> 
> -- 
> ---------------------------------------------------------------------------------
> Javier Herrero
> Chief Technology Officer                           EMAIL: jherrero at hvsistemas.com
> HV Sistemas S.L.                                   PHONE:         +34 949 336 806
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