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 <bneu...@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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