The accuracy (or tolerance) of thermocouples varies from type to type, and is specified by international standard.
BS EN 60584-1:2013 is widely used in the UK and Europe. The table below shows the tolerance, which is the greater of the two terms in each temperature range.
Class 1 material has the tightest tolerance, Thermal Detection only uses Class 1
| Tolerance v Temperature and Limits of Validity as BS EN 60584-1:2013 | |||
| Type | Class 1 | Class 2 | Class 3 |
| J | -40 to +750°C : +/-1.5°C or (t x 0.004) |
-40 to +750°C : +/-2.5°C or (t x 0.0075) |
|
| K | -40 to +1000°C: +/-1.5°C or (t x 0.004) |
-40 to +1200°C: +/-2.5°C or (t x 0.0075) |
-200 to +40°C: +/-2.5°C or (t x 0.015) |
| T | -40 to +350°C: +/-0.5°C or (t x 0.004) |
-40 to +350°C: +/-1.0°C or (t x 0.0075) |
-200 to +40°C: +/-1.0°C or (t x 0.015) |
| E | -40 to +800°C: +/-1.5°C or (t x 0.004) |
-40 to +900°C: +/-2.5°C or (t x 0.0075) |
-200 to +40°C: +/-2.5°C or (t x 0.015) |
| N | -40 to +1000°C: +/-1.5°C or (t x 0.004) |
-40 to +1200°C: +/-2.5°C or (t x 0.0075) |
-200 to +40°C: +/-2.5°C or (t x 0.015) |
| R | 0.0 to 1099°C: +/-1.0°C 1100°C to 1600°C: +/-1+[0.003 x (t-1100)] |
0 to 1600°C: +/-1.5°C or ±t x 0.0025 |
|
| S | 0.0 to 1099°C: +/-1.0°C 1100°C to 1600°C: +/-1+[0.003 x (t-1100)] |
0 to 1600°C: +/-1.5°C or ±t x 0.0025 |
|
| B | +600 to 1700°C: +/-t x 0.01 |
+600 to 1700°C: +/-4.0°C or (t x 0.005) |
|
So, for example, a Type T Class 1 thermocouple would have the following accuracy:
At 0°C +/- 0.5°C ( greater of 0.5 or 0 x 0.004)
At 200°C +/- 0.8°C (greater of 0.5 or 200 x 0.004)
