v1.02, calculation revised 4/9/2026. The previous v1.01 audit is superseded. Confirm suitability before use.
About RTD Coefficients
The Callendar-Van Dusen equation describes the relationship between temperature and resistance in platinum resistance thermometers. The coefficients A, B, and C are determined through calibration at specific temperature points.
This calculator determines these coefficients using temperature and resistance measurements. The reference measurement may be at 0°C, the water triple point (0.01°C), or another non-negative temperature. The calculator solves R₀, A and B simultaneously from the reference point and two positive temperature points. For coefficient C, include one negative temperature point.
Measurement Input
Reference Point Selection
This measured value is R₀ directly.
Point 1 (≈100°C)
Point 2 (≈260°C)
Point 3 (≈-50°C, optional)
Calculated Coefficients
Technical Information
Callendar-Van Dusen Equations
For temperatures ≥ 0°C:
R(t) = R₀ × (1 + A×t + B×t²)
For temperatures < 0°C:
R(t) = R₀ × (1 + A×t + B×t² + C×(t-100)×t³)
For a reference measurement above 0°C, the measured reference resistance is not treated as R₀. R₀, A and B are solved simultaneously from the three non-negative calibration points.
Standard Values (IEC 60751)
- A = 3.9083 × 10⁻³ °C⁻¹
- B = -5.775 × 10⁻⁷ °C⁻²
- C = -4.183 × 10⁻¹² °C⁻⁴
- α = 0.00385 °C⁻¹
- δ = 1.4999
- β = 0.10863
Measurement Recommendations
- Use a reference measurement at 0°C, the water triple point (0.01°C), or another non-negative temperature
- Take measurements at approximately 100°C and 260°C for positive coefficients
- Include a measurement at approximately -50°C if coefficient C is needed
- Use high-precision temperature and resistance measurements
- Ensure good thermal equilibrium before taking measurements
- Consider self-heating effects in measurements
- Use proper 4-wire resistance measurement technique