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PT100 and PT1000 accuracy at -50 °C
What IEC 60751 allows a platinum resistance thermometer at -50 °C, class by class, and what the rest of the measurement adds.
Tolerance by class
| Class | Tolerance (°C) | PT100 (Ω) | PT1000 (Ω) |
|---|---|---|---|
| AA | ±0.19 | ±0.073 | ±0.73 |
| A | ±0.25 | ±0.099 | ±0.99 |
| B | ±0.55 | ±0.218 | ±2.18 |
| C | ±1.10 | ±0.437 | ±4.37 |
At -50 °C
- Resistance
- 80.306 Ω · 803.06 ΩPT100 / PT1000
- Sensitivity
- 0.3971 Ω/K · 3.971 Ω/KPT100 / PT1000
Example: the whole measurement
| Term | Assumption | Error |
|---|---|---|
| Sensor tolerance | PT100, Class A | ±0.250 K |
| Lead wires | 3-wire, 10 m, 0.5 mm² | ±0.043 K |
| Transmitter input | ±0.1 K | ±0.100 K |
| Analog output | ±0.03 % × 200 K | ±0.060 K |
| Ambient effect | ±0.1 % / 10 K × 20 K | ±0.400 K |
| Total probable error | RSS | ±0.49 K |
| Worst case | Σ | ±0.85 K |
An example with typical datasheet figures, not a statement about any product. Enter your own values in the calculator.
How the tolerance is defined
IEC 60751 gives each class as ±(a + b·|t|) °C within its own temperature range: AA 0.1 + 0.0017·|t|, A 0.15 + 0.002·|t|, B 0.3 + 0.005·|t|, C 0.6 + 0.01·|t|. The ranges here are those for wire-wound elements; thin-film elements often have narrower ones, so check the datasheet. The same limits in °C apply to PT100 and PT1000; in ohms the PT1000 figure is ten times larger.
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