Thermocouple Tolerances
Practical Tolerances
In practice, thermocouples can’t always be made to conform exactly to the published tables. So thermocouple output tolerances for both noble and base metal thermocouples are published as IEC 60584-2, and ASTM E-230, and manufacturers provide the sensors to these agreed limits (Table 3.3).
The tolerance values are for thermocouples manufactured from wires normally in the diameter range of 0.1mm to 3.0mm and do not allow for calibration drift during use. Thermocouples other than those listed in these standards are usually supplied with the manufacturers calibration tables.
Technical Data
| Conductor Combination | Approximate generated EMF change in µV per ºC change (referenced to 0ºC) at: |
Approximate Working Temperature Range |
Thermocouple Output Tolerances to IEC 60584-1 |
|||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Type | + Leg | - Leg | 100ºC | 500ºC | 1000ºC | Continuous | Short Term | Type | Class 1 | Class 2 |
| K | NICKEL - CHROMIUM Also known as: Chromel™, Thermokanthal KP*, NiCr, T1*, Tophel™ |
NICKEL - ALUMINIUM (magnetic) Also known as: Ni-Al, Alumel™, Thermokanthal KN™, T2™, NiAl™ |
42 | 43 | 39 | 0 to +1100ºC | -180 to +1350ºC | Temperature Range Tolerance Value Temperature Range Tolerance Value |
–40°C to +375°C ±1.5°C 375°C to 1000°C ±0.004 ⋅ |t| |
–40°C to +333°C ±2.5°C 333°C to 1200°C ±0.0075 ⋅ |t| |
| T | COPPER |
COPPER - NICKEL Also known as: Constantan, Advance™, Cupron™ |
46 | – | – | –185 to +300°C | –250 to +400°C | Temperature Range Tolerance Value Temperature Range Tolerance Value |
–40°C to +125°C ±0.5°C 125°C to 350°C ±0.004⋅ |t| |
–40°C to +133°C ±1.0°C 133°C to 350°C ±0.0075 ⋅ |t| |
| J | IRON (magnetic) Also known as: Fe | COPPER - NICKEL Also known as: Nickel-Copper, Constantan, Advance™, Cupron™ |
54 | 56 | 59 | +20 to +700°C | –180 to +750°C | Temperature Range Tolerance Value Temperature Range Tolerance Value |
–40°C to +375°C ±1.5°C 375°C to 750°C ±0.004⋅ |t| |
–40°C to +333°C ±2.5°C 333°C to 750°C ±0.0075 ⋅ |t| |
| N | NICKEL - CHROMIUM -SILICON Also known as: Nicrosil | NICKEL - SILICON - MAGNESIUM Also known as: Nisil |
30 | 38 | 39 | 0 to +1150ºC | -270 to +1300ºC | Temperature Range Tolerance Value Temperature Range Tolerance Value |
–40°C to +375°C ±1.5°C 375°C to 1000°C ±0.004⋅ |t| |
–40°C to +333°C ±2.5°C 333°C to 1200°C ±0.0075⋅ |t| |
| E | NICKEL - CHROMIUM Also known as: Chromel™, Tophel™, Chromium, Nickel | NICKEL - ALUMINIUM Also known as: Nickel-Copper, Constantan, Advance™, Cupron™ |
68 | 81 | – | 0 to +800ºC | -40 to +900ºC | Temperature Range Tolerance Value Temperature Range Tolerance Value |
–40°C to +375°C ±1.5°C 375°C to 800°C ±0.004⋅ |t| |
–40°C to +333°C ±2.5°C 333°C to 900°C ±0.0075 ⋅ |t| |
| S | PLATINUM -
10% RHODIUM | PLATINUM |
8 | 9 | 11 | 0 to +1550ºC | -50 to +1750ºC | Temperature Range Tolerance Value Temperature Range Tolerance Value |
0°C to +1100°C ±1.0°C 1100°C to 1600°C ±(1 +0.003 (t ⋅ 1100)°C |
0°C to +600°C ±1.5°C 600°C to 1600°C ±0.0025 ⋅ |t| |
| R | PLATINUM -
13% RHODIUM |
PLATINUM |
8 | 10 | 13 | 0 to +1600ºC | -50 to +1700ºC | Temperature Range Tolerance Value Temperature Range Tolerance Value |
0°C to +1100°C ±1.0°C 1100°C to 1600°C ±(1 +0.003 (t ⋅ 1100)°C |
0°C to +600°C ±1.5°C 600°C to 1600°C ±0.0025 ⋅ |t| |
2. Thermocouple materials are normally supplied to meet the tolerances specified in the table for temperatures above –40 deg C. These materials however, may not fall within the tolerances for low temperatures given under Class 3 for Types T, E and K thermocouples. If thermocouples are required to meet limits of Class 3, as well as those of Class 1 and/or Class 2, the purchaser should state this, as selection of materials is usually required.
