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Hi all,

i have to monitor a fridge temperature which has to be around -80°C but cannot find a (possibily wireless) sensor that supports such a low temperature.
do you know of any?

thanks in advance,

Christian
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All the chip temperature sensors I know of seem to have a bottom end of -55°C.  I think you may have to use a thermocouple.
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thanks for the answer.
termocouples sounds ok, but can you give me some directions for learning how to use them? i'm a newbie smiley

thanks a lot
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- http://en.wikipedia.org/wiki/Thermocouple -
- http://reprap.org/wiki/Thermocouple_Sensor_1.0 -

Just curious, what do you keep at -80C? assume that it is not your beer smiley-wink
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don't you like frozen beers? smiley

biological stuff at the university, mainly cell coltures smiley-wink

thanks a lot for the links
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ryanjmclaughlin.com/wiki/Single_Thermocouple_Interface
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ok, thanks to your links all is a bit clear to me now.
anyway, i'm wondering if it's possible to use some kind of wireless thermocouples, because it' difficult to have a cable coming out of a -80C freezer.

i think that xbee should be the way to go, but maybe you know something better. of course, the transmitter has to stay at -80C, so electronic part has to be as simple as possible i guess.

ideas?
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Quote
i'm wondering if it's possible to use some kind of wireless thermocouples, because it' difficult to have a cable coming out of a -80C freezer.

First check if wifi or GSM or whatever wireless protocoll you have in mind work in the freezer.

idea: If there is electric light in the freezer you might use some signal over powerline technique.?



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Rob Tillaart

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Good luck finding chips that will run at -80C to send the data out. ATmegas have a range down to -40C. I don't think that's arbitrary.

OTOH if you always keep current running through your circuits they may never get so cold and you won't have to worry about using heat sinks! Maybe it would be good to feed the regulator 12V-18V and wrap the unit in some amount of insulation even. This might be analogous to running water in a pipe to keep it from freezing solid, how much trickle is enough?

Semiconductors don't semi-conduct the same when they're too cold. It's just that simple.





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