RTD Calculator
A Pt100 sensor at 100 °C reads 138.5055 Ω, from the IEC 60751 Callendar–Van Dusen equation.
IEC 60751 range −200 °C to 850 °C.
138.5055 Ω
Full answer, then cut to fewer decimals (not rounded):
- 138.5055 Ω
- 138.505 Ω
- 138.50 Ω
- 138.5 Ω
- Linear estimate R₀(1 + 0.00385 T)
- 138.5 Ω
- Sensitivity dR/dT
- 0.37928 Ω/°C
Step-by-step solution
- R = R₀(1 + AT + BT²) with A = 3.9083 × 10⁻³, B = −5.775 × 10⁻⁷
- R = 100 × (1 + 0.39083 + -0.005775)
- R = 138.5055 Ω
RTD Formula
R = R₀(1 + AT + BT²) for T ≥ 0 °C
A = 3.9083 × 10⁻³, B = −5.775 × 10⁻⁷; below 0 °C add C(T − 100)T³, C = −4.183 × 10⁻¹²
Worked Example
A Pt100 at 100 °C:
- R = R₀(1 + AT + BT²) with A = 3.9083 × 10⁻³, B = −5.775 × 10⁻⁷
- R = 100 × (1 + 0.39083 + -0.005775)
- R = 138.5055 Ω
Sensitivity dR/dT: 0.37928 Ω/°C
GATE tip
GATE often gives R = R₀(1 + αT) with α = 0.00385/°C or 0.004/°C. Use the value stated; this calculator’s linear row shows the α = 0.00385 answer for comparison.
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Frequently asked questions
What is α = 0.00385?
The average sensitivity of IEC platinum between 0 and 100 °C: (R₁₀₀ − R₀)/(100 R₀). It gives a quick linear estimate.
Why use 3- or 4-wire connections?
Lead resistance adds directly to a 2-wire reading: 1 Ω of leads is a 2.6 °C error on a Pt100. Three wires cancel matched leads; four wires remove them entirely.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
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APA
Scientific Converters. (2026, October 15). RTD Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/rtd-calculator/
IEEE
Scientific Converters, "RTD Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/rtd-calculator/