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thermocouple Fe-CuNi and analog multimeter about measuring temps

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Kiriakos-GR:
I am translating the German manual of my analog meter ( 80s) ,
and I got to the point that I need some help.

It says that it can measure temperature by the use of one thermocouple Fe-CuNi .
And it will be connected on the analog , by having set the selector to the range of 75mV DC ??

How is that possible ?

How is possible one thermocouple Fe-CuNi to produce voltage ?
So to be measured by the meter ?

It sounds like that the thermocouple Fe-CuNi has the ability to convert heat to DC !!  

From the translation it looks that the what ever temperature  measurement ,
does not scale in such detail , so its no good for finding differences of just 2-3C , rather than 20 50 150 300 up to  900C .

I found only that this element called as Type L

And an sample of it here ..

https://www1.elfa.se/elfa3/elfa/init.do?item=76-689-11&toc=19402&name=mantle_thermocouple_fe-cuni

alm:
Look up the Seebeck effect, this is also used in modern day thermocouples (eg. the type K ones often shipped with DMMs). Sounds like they might be using a type J thermocouple. Thermocouples can be fairly accurate, down to +/- 1-2 Kelvin or so, but probably not with just a voltmeter. The V-T curve is not completely linear, real thermometers (or DMMs with thermometer function) should compensate for this.

Jon Chandler:

--- Quote from: Kiriakos-GR on April 09, 2011, 11:45:01 pm ---
It sounds like that the thermocouple Fe-CuNi has the ability to convert heat to DC !!  


--- End quote ---

Any two dissimilar metals will produce a voltage when heated.  It's a small but measurable voltage.

Here's a method I used to measure the (<50 mV) small voltage generated and some background information.

Alex:
And the inverse of the Seebeck effect exploited by thermocouples is the Peltier effect exploited by thin thermoelectric coolers/heat pumps/peltier elements usually found in car chillers, heatsinks and to control the temperature of laser diodes.

I had seen a guy powering a laptop with a thermocouple. It was actually a series of Peltier elements with one end on a heatsink and fan and the other end on a gas stove. The temperature difference created electric current.

One of Dave's blogs has a cheap 'environmental chamber' that if I remember correctly uses Peltier elements.

Simon:

--- Quote from: Alex on April 10, 2011, 02:30:30 am ---
I had seen a guy powering a laptop with a thermocouple. It was actually a series of Peltier elements with one end on a heatsink and fan and the other end on a gas stove. The temperature difference created electric current.


--- End quote ---

There are commercially available peltier cell generators normally used in cold regions of the planet and run off oil

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