Solution
When talking about accuracy, you should consider the accuracy of the measurement hardware, as well as the inherent accuracy of the thermocouple. The accuracy of a thermocouple is affected by its type and temperature. See the table below for the maximum permitted error (in degree Celsius) for various common thermocouples that comply with IEC 584-2 (1982).
| Temperature | B Type | E Type | J Type | K Type | N Type | R Type | S Type | T Type |
|---|
| -200 | - | - | - | 3.0 | 3.0 | - | - | 3.0 |
| -100 | - | - | - | 2.5 | 2.5 | - | - | 1.5 |
| 0 | - | 1.7 | 1.5 | 1.5 | 1.5 | 1.0 | 1.0 | 0.5 |
| 200 | - | 1.7 | 1.5 | 1.5 | 1.5 | 1.0 | 1.0 | 0.8 |
| 400 | - | 2.0 | 1.6 | 1.6 | 1.6 | 1.0 | 1.0 | - |
| 600 | 1.5 | 3.0 | 2.4 | 2.4 | 2.4 | 1.0 | 1.0 | - |
| 800 | 2.0 | 4.0 | - | 3.2 | 3.2 | 1.0 | 1.0 | - |
| 1000 | 2.5 | - | - | 4.0 | 4.0 | 1.0 | 1.0 | - |
| 1200 | 3.0 | - | - | 9.0 | 9.0 | 1.3 | 1.3 | - |
| 1400 | 3.5 | - | - | - | - | 1.9 | 1.9 | - |
| 1600 | 4.0 | - | - | - | - | 2.5 | 2.5 | - |
In addition to accuracy based on the type of thermocouple, thermocouples have a specified range of temperatures over which they can operate. This can become a problem when extreme high temperatures are being read. Their ranges are determined by numerous variables, including the following:
- Type (i.e. J, K, E, T, RX/SX, N, CX)
- Sheath material
- Sheath diameter