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Originally Posted by bigben2k
RTDs suck!
I was set on using RTDs for my testbench, and I'm finding out that thermocouples would be more appropriate, for a number of reasons:
1-the response slope of an RTD is almost flat, making it virtually impossible to detect temperatures with a resolution of 0.01 or smaller. Thermocouples have a nice slope, but it's not quite linear. Omega does however carry "linear response" TCs...
2-Going over Omega.com 's PRTD elements, class A or class B, the response time is really poor, compared to thermocouples.
PRTDs have an advantage where their linearity varies very little, over a very wide temperature range. Useless to me, I'll be measuring temps within a very narrow range, and response time is actually important!!!
I might get one PRTD, but just for the sake of getting an accurate reference point, checking temps alongside thermocouples. BTW, a class A PRTD has an accuracy of +/- 0.15 deg C (element alone, not counting the temp reader).
Anyone want links to the PRTD info from Omega?
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As a long time user of RTDs, they do have their problems, but by calibration, they can be used. Try this link for a better precision product
http://www.airpaxtsp.com/tspsite/3000.html
You will want a 4 wire reader and you will want to cross calibrate the probes, but should be able to get +/-0.03 C pretty easily after cross-calibration.