AUTIXON / ELECTRONICS & INSTRUMENTATION
FormulaR(T) = R₀ [1 + A T + B T² + C(T − 100)T³]; C term only below 0 °C
Callendar–Van Dusen model for platinum α = 0.00385: A = 3.9083×10⁻³, B = −5.775×10⁻⁷, C = −4.183×10⁻¹². Supported mathematical range: −200…850 °C.
Two-wire mode adds or subtracts the known total lead resistance. Compensated mode assumes lead effects have already been removed. Sensor tolerance, self-heating and instrument errors are not included; the probe’s usable range may be narrower.
Analog Devices — CN0383 RTD transfer function ↗A PT100 has a nominal resistance of 100 Ω at 0 °C; a PT1000 has 1,000 Ω at the same temperature. This converter uses the platinum α = 0.00385 Callendar–Van Dusen model rather than a constant ohms-per-degree approximation.
| Temperature | PT100 | PT1000 |
|---|---|---|
| −200 °C | 18.52008 Ω | 185.2008 Ω |
| −100 °C | 60.25584 Ω | 602.5584 Ω |
| 0 °C | 100 Ω | 1000 Ω |
| 100 °C | 138.5055 Ω | 1385.055 Ω |
| 200 °C | 175.856 Ω | 1758.56 Ω |
| 850 °C | 390.481125 Ω | 3904.81125 Ω |
The nominal model gives 138.5055 Ω for a PT100 and 1385.055 Ω for a PT1000. A real reading also depends on sensor tolerance, wiring and the measuring instrument.
If the terminal reading is 140.5055 Ω and both leads total 2 Ω, the corrected PT100 resistance is 138.5055 Ω, corresponding to 100 °C in the nominal model.
No. It is the range supported by the mathematical model. Check the actual probe’s construction, rated temperature range and tolerance. The calculation does not include self-heating or measurement uncertainty.