Discussion in 'Electronic Design' started by Paul Taylor, Oct 27, 2004.

1. ### Paul TaylorGuest

Has any one built a circuit to change from kelvin to degrees centigrade? any help on this is much appreciated.

2. ### leggGuest

What are you starting with, a signal level or data?

RL

3. ### Paul TaylorGuest

Sorry, Yes I am starting with a signal level from a thermocouple chip.

-------------------------------------------------------
Paul Taylor BSC (Hons)
Electronics Technician
School of Environmental Science
University of East Anglia
Norwich
NR4 7TJ

Phone: +44 (0)1603 592502
Fax: +44 (0)1603 591327

Email:
Web: http://www.uea.ac.uk/~e087

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4. ### Don PearceGuest

If you really need to do this in the electronics, simply put a voltage
in series equivalent to the output at 0C, and of the opposite
polarity.

Far better though to get it into an ADC as quickly as possible, and do
it with Maths.

d
Pearce Consulting
http://www.pearce.uk.com

5. ### Bob StephensGuest

It's just a fixed offset of 273 degrees isn't it?

Bob

6. ### Don PearceGuest

Yup - 273.15 if we're being picky.

d
Pearce Consulting
http://www.pearce.uk.com

8. ### Tim WescottGuest

This should be a simple op-amp cookbook exercise to subtract an offset
and (possibly) multiply by a gain.

What are you using for a cold junction that you get an answer in Kelvin
instead of relative to room temperature?

9. ### Spehro PefhanyGuest

'~' is right. ;-)

Maybe you're thinking of the triple-point (of water) = +0.01°C =
+273.16 K

0°C = -273.15 K

Best regards,
Spehro Pefhany

10. ### Eric PearsonGuest

http://www.speff.com

If you currently have a thermocouple attached to an instrument and it reads
in K, then
its has a cold junction compensation for 0K (which is 0 uVolts)

To make it read in C, just add another thermocouple in series (but reversed)
to create a
real cold juntion, and put it in a tub of ice water at 0 C, and your
instrument will now read in C.

Eric Pearson

11. ### Spehro PefhanyGuest

Where the heck is your reference junction?
How convenient. ;-)
Nope. Try again. ;-)

Best regards,
Spehro Pefhany

12. ### Rich GriseGuest

This is every circuit anybody's built, ever.

Degrees Kelvin Circuit o-----o Meter calibrated in Centigrade

Cheers!
Rich

13. ### Rich GriseGuest

What would happen if anybody ever really achieved absolute zero?

Would the universe implode into the Final Black Hole?

Thanks,
Rich

15. ### Spehro PefhanyGuest

Almost unbelievably cold ;-) +, of course.

Best regards,
Spehro Pefhany

16. ### Jonathan KirwanGuest

Temperature is better thought of in inverse-Kelvins. It does better at getting
the point across about absolute zero. T usually winds up in the denominator of
various expressions, anyway. Might as well elevate the idea to a multiplier,
where it belongs.

Jon

17. ### Chaos MasterGuest

Quoting Rich Grise [], that posted to sci.electronics.design on
Wed, 27 Oct 2004 20:52:00 GMT under article
Would be cool for some overclocking!
I can imagine a CPU cooled at this level.

[]s

18. ### Pooh BearGuest

You don't need a 'circuit' !

Degrees C = degrees K +273

How you choose to achieve the addition / subtraction ( either in
software or in harware ) and input and present the data is up to you.

Graham