0
\$\begingroup\$

I'm currently using a cubic fit formula I found online to derive the temperature of a PT100/385 RTD using resistance. The formula is -247.29 + 2.3992*R + 0.00063962 *R^2 + 0.0000010241 *R^3 where R is Ohms. Does anyone know where I could find a similar formula for a 39250 RTD? I've tried to find one online, but I have had no luck.

I need to use this instead of the standard Linear one because I need more accurate readings at high temperatures.

\$\endgroup\$
1
  • \$\begingroup\$ Where's the link to the datasheet? Does it give you three or more R-T values? You also need to specify whether the formula gives you °C or °F. There's an edit link under your question. Welcome to EE.SE. \$\endgroup\$
    – Transistor
    Commented Feb 28, 2019 at 19:13

1 Answer 1

Reset to default
0
\$\begingroup\$

Assuming you're talking about the old-fashioned so-called "American standard" RTD, they're seldom used these days. You can find Callendar-Van Dusen equation coefficients for those, and some other types, on this National Instruments web page.

enter image description here

If your RTD is 50 ohms, just scale it (double the measured resistance) so it fits the 100 ohm equation.

\$\endgroup\$
2
  • \$\begingroup\$ Thank you! Would you happen to know the variation of the Callendar-Van Dusen equation which solves for temperature with an input resistance? \$\endgroup\$
    – Trubsworth
    Commented Mar 1, 2019 at 0:11
  • \$\begingroup\$ Ah, I would use a search to invert it but you could fit it to a polynomial for least squares error. I don’t think the results would be as good with the latter. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Mar 1, 2019 at 0:24

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.