RTD Callendar-Van Dusen

Formula

Description

The Callendar-Van Dusen equation describes the resistance-temperature relationship of RTD (Resistance Temperature Detector) sensors, most commonly Pt100 and Pt1000 platinum elements. For temperatures above 0°C, the second-order polynomial provides accuracy within ±0.01°C. The coefficients A and B are standardized in IEC 60751. Platinum RTDs are the gold standard for precision temperature measurement because of their excellent linearity, stability, and repeatability. The R0 value indicates the resistance at 0°C (100Ω for Pt100, 1000Ω for Pt1000).

Variables

• R(T) — RTD resistance at temperature T (Ω)
• R0 — Resistance at 0°C (Ω)
• A — First coefficient (3.9083 × 10⁻³ °C⁻¹ for IEC 60751)
• B — Second coefficient (-5.775 × 10⁻⁷ °C⁻² for IEC 60751)
• T — Temperature (°C)

Practical Notes

IEC 60751 standard coefficients: A = 3.9083e-3, B = -5.775e-7. Below 0°C, a third term C×(T-100)×T³ is added. RTD accuracy classes: Class A ±0.15°C at 0°C, Class B ±0.30°C. Always use 4-wire measurement to eliminate lead resistance errors. Self-heating from the excitation current must be minimized (typically < 1 mA for Pt100).