PT100 / PT500 / PT1000 RTD Calculator
Calculate platinum RTD resistance using the CVD equation; editing resistance uses the App’s three-segment polynomial temperature approximation.
Inputs and reverse calculation
Calculated results
| Temperature T | 100 °C |
|---|---|
| Resistance R | 138.506 Ω |
How to interpret the result
PT100, PT500 and PT1000 have nominal resistances of 100, 500 and 1000 Ω at 0 °C. The forward CVD calculation includes its fourth-order correction below zero.
Formulas and units
R = R0[1 + AT + BT² + C(T−100)T³], with the C term omitted for T ≥ 0. A = 3.9083×10⁻³, B = −5.775×10⁻⁷ and C = −4.18301×10⁻¹². T is in °C and R in Ω.
Worked example
PT100 gives 138.5055 Ω at 100 °C and approximately 80.306281856 Ω at −50 °C. PT1000 gives 1385.055 Ω at 100 °C. The App inverse of 138.5055 Ω gives about 100.018881 °C, showing its approximation error.
Scope and limitations
The inverse uses x = R/H with H = 1/5/10. Decompiled conditions overlap; this implementation explicitly uses x < 100, 100 ≤ x ≤ 162 and x > 162. Unnamed hidden sensor types are excluded. For PT100, 18.5 Ω approximates −200.052 °C and 391 Ω approximates 851.774 °C, so these out-of-range results are rejected. C retains the App value −4.18301×10⁻¹², slightly different from −4.183×10⁻¹² in the TI guide. Lead resistance, self-heating, calibration and sensor tolerance are excluded.
Common questions
Why does an inverse conversion not return exactly the original temperature?
The forward path uses CVD; the reverse path follows the App’s three polynomial approximations. They are not exact inverses. Calibration work requires sensor-specific coefficients and a numerical inverse.
Can this convert an NTC thermistor reading?
No. This tool uses the specified platinum RTD curve. An NTC thermistor requires its beta value or Steinhart–Hart coefficients.
Related tools
Formula and data sources
- TI SBAA275A: A Basic Guide to RTD Measurements
- Analog Devices: RTD Measurement System Design Essentials
Rebuilt from the extracted Electrodoc Pro 5.2 specification. Added, inferred and corrected behavior is identified in the limitations. Updated 2026-11-13.