Engineering reference data for temperature sensor selection, application, and specification. RTD accuracy classes, thermocouple type comparison, standard wire resistivity, and relevant international standards — consolidated for design engineers.
| IEC 60751 Class | Tolerance Formula | At 0°C | At 100°C | At 400°C | Valid Range |
|---|---|---|---|---|---|
| Class AA (1/3 DIN) | ±(0.1 + 0.0017|t|) °C | ±0.10°C | ±0.27°C | ±0.78°C | −50 to 250°C |
| Class A | ±(0.15 + 0.002|t|) °C | ±0.15°C | ±0.35°C | ±0.95°C | −100 to 450°C |
| Class B | ±(0.3 + 0.005|t|) °C | ±0.30°C | ±0.80°C | ±2.30°C | −196 to 850°C |
| Class C | ±(0.6 + 0.01|t|) °C | ±0.60°C | ±1.60°C | ±4.60°C | −196 to 600°C |
For temperatures above 0°C: R(T) = R₀[1 + AT + BT²]. For temperatures below 0°C: R(T) = R₀[1 + AT + BT² + C(T−100)T³]. Standard IEC 60751 coefficients: A = 3.9083×10⁻³ °C⁻¹, B = −5.775×10⁻⁷ °C⁻², C = −4.183×10⁻¹² °C⁻⁴ (below 0°C only). R₀ = 100.000 Ω (nominal for Pt100).
| Type | EMF at 100°C (mV) | Sensitivity (µV/°C) | Atmosphere | Avoid |
|---|---|---|---|---|
| K (NiCr/NiAl) | 4.096 | ~41 | Oxidizing, inert | Reducing, sulfurous, vacuum above 400°C |
| J (Fe/Con) | 5.269 | ~53 | Reducing, inert, vacuum | Oxidizing above 550°C, moisture |
| T (Cu/Con) | 4.279 | ~43 | Oxidizing, reducing, moist | Above 370°C (Cu oxidizes) |
| E (NiCr/Con) | 6.319 | ~63 | Oxidizing, inert | Reducing, sulfurous |
| N (Nicrosil/Nisil) | 2.774 | ~28 | Oxidizing, inert | Reducing above 400°C |
| R (Pt13Rh/Pt) | 0.647 | ~10 | Oxidizing, inert | Reducing, metallic vapor, carbon |
| S (Pt10Rh/Pt) | 0.646 | ~10 | Oxidizing, inert | Reducing, metallic vapor, carbon |
| B (Pt30Rh/Pt6Rh) | — | ~6 (above 500°C) | Oxidizing, inert | Reducing; negligible output below 50°C |
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