RTD Element Tolerance Calculator

How the calculator works

Nominal resistance is calculated from the Callendar-Van Dusen equations that IEC 60751:2022 specifies as the normative definition of a conforming sensor:

R(t) = R₀ (1 + At + Bt²) for 0 °C ≤ t ≤ 850 °C

R(t) = R₀ [1 + At + Bt² + C(t − 100 °C)t³] for −200 °C ≤ t < 0 °C

with A = 3.9083 × 10⁻³ °C⁻¹, B = −5.775 × 10⁻⁷ °C⁻², C = −4.183 × 10⁻¹² °C⁻⁴. The permitted tolerance for each element class is ±(a + b |t|) per Table 1 of the standard, and a class only applies inside its temperature range of validity. The equivalent temperature error of a measured resistance is the deviation divided by the local sensitivity dR/dt.

Notes

• This calculator covers platinum resistors (sensing elements) — Table 1 of IEC 60751:2022. Complete thermometers use classes AA to C from Table 2, with different ranges of validity; see IEC 60751 Explained.
• Outside a class's range of validity the standard makes no promise on the sensor's behalf, so no tolerance is shown.
• Tighter interchangeability than W 0.1 is available from TDI as an R₀ selection at 0 °C, down to ±0.01 % of R₀ (traditionally described as "1/10 DIN"). This is a 0 °C interchangeability figure, not automatically a full-range IEC special class under clause 5.2.3.2 — read about what fractional tolerances promise, or ask us for a quotation.
• Results are for guidance only and round to displayed precision; refer to IEC 60751:2022 for the authoritative specification.
• This calculator covers element (Table 1) classes only. For complete-thermometer classes and other RTD calculators, calibration.info offers a related set of tools.