Pt100 and Pt1000: tolerance classes to DIN EN 60751
A Pt100 has exactly 100 Ω at 0 °C and 138.51 Ω at 100 °C. How far an individual resistor may deviate from this is defined in DIN EN 60751 — through four classes and two special classes.
A class only ever applies within its validity range, and for thin-film elements that range is narrower than for wire-wound ones. This is regularly overlooked in enquiries.
The tolerance classes to DIN EN 60751
| Class | Tolerance in °C | valid wire-wound | valid thin-film |
|---|---|---|---|
| Class AA | ± (0.10 + 0.0017 · |t|) | −50…+250 °C | 0…+150 °C |
| Class A | ± (0.15 + 0.002 · |t|) | −100…+450 °C | −30…+300 °C |
| Class B | ± (0.30 + 0.005 · |t|) | −196…+600 °C | −50…+500 °C |
| Class C | ± (0.60 + 0.01 · |t|) | −196…+600 °C | −50…+600 °C |
| 1/3 DIN B | ± (0.1 + 0.0017 · |t|) | restricted range | restricted range |
| 1/10 DIN B | ± (0.03 + 0.0005 · |t|) | restricted range | restricted range |
1/3 and 1/10 DIN B are not classes of the standard but divisors of class B established in the industry. We supply them, but always state the range in which they apply.
The tolerance increases with temperature. Class AA and 1/3 DIN B coincide mathematically but apply in different ranges.
Tolerance in °C, calculated
| °C | 1/10 B | 1/3 B | AA | A | B |
|---|---|---|---|---|---|
| −200 | ± 0.13 | ± 0.43 | ± 0.44 | ± 0.55 | ± 1.30 |
| −100 | ± 0.08 | ± 0.27 | ± 0.27 | ± 0.35 | ± 0.80 |
| 0 | ± 0.03 | ± 0.10 | ± 0.10 | ± 0.15 | ± 0.30 |
| 100 | ± 0.08 | ± 0.27 | ± 0.27 | ± 0.35 | ± 0.80 |
| 200 | ± 0.13 | ± 0.43 | ± 0.44 | ± 0.55 | ± 1.30 |
| 300 | ± 0.18 | ± 0.60 | ± 0.61 | ± 0.75 | ± 1.80 |
| 400 | ± 0.23 | ± 0.77 | ± 0.78 | ± 0.95 | ± 2.30 |
| 500 | ± 0.28 | ± 0.93 | ± 0.95 | ± 1.15 | ± 2.80 |
| 600 | ± 0.33 | ± 1.10 | ± 1.12 | ± 1.35 | ± 3.30 |
Calculated values — applicable only within the validity range of the respective class.
Reference values Pt100 and Pt1000
| °C | Pt100 in Ω | Pt1000 in Ω |
|---|---|---|
| −200 | 18.52 | 185.2 |
| −100 | 60.26 | 602.6 |
| −50 | 80.31 | 803.1 |
| 0 | 100.00 | 1000.0 |
| 50 | 119.40 | 1194.0 |
| 100 | 138.51 | 1385.1 |
| 150 | 157.33 | 1573.3 |
| 200 | 175.86 | 1758.6 |
| 300 | 212.05 | 2120.5 |
| 400 | 247.09 | 2470.9 |
| 500 | 280.98 | 2809.8 |
| 600 | 313.71 | 3137.1 |
| 700 | 345.28 | 3452.8 |
| 800 | 375.70 | 3757.0 |
| 850 | 390.48 | 3904.8 |
Characteristic curve to Callendar-Van Dusen with A = 3.9083·10−3, B = −5.775·10−7 and C = −4.183·10−12 (only for t < 0 °C).
Wire-wound or thin-film
- Wire-wound (ceramic) — wide temperature range up to +600 °C, very good long-term stability.
- Thin-film — robust, vibration-resistant, fast response, economical; in return the narrower validity range from the table above.
What counts in practice
The tolerance of the resistor is only part of the measurement error. In the plant, three points often cost more accuracy than the class:
- Immersion depth — to counter heat dissipation, immerse at least 6 to 8 times the thermowell diameter in liquids and 10 to 15 times in gases.
- Circuit — in a two-wire circuit the cable resistance enters the measurement in full. More on this under Two-, three- or four-wire.
- Cable routing — measuring cables at least 0.5 m away from power cables, twisted and screened.
Do you need class A or is B enough?
Tell us the measuring range and the required measurement uncertainty — we will tell you which class is valid at all in that range and what it costs.
The tolerance classes
Tolerance in °C
Reference values Pt100 / Pt1000
Wire-wound or thin-film
What counts in practice
All resistance thermometers
Thermowell thermometers
Sheathed resistance thermometers
Two-, three- or four-wire
Pt100 or thermocouple?
Question about the design?
Tell us medium, temperature and installation — you will receive a proposal within one working day.