Type K thermocouple
Ni-Cr / Ni-Al · -270 … 1372 °C · IEC 60584-1
At a glance
- Conductors (+ / −)
- Ni-Cr / Ni-Al
- Range of the reference function
- -270 … 1372 °C
- Sensitivity at 400 °C
- 42.24 µV/°C
- Class 1 tolerance
- ±1.5 °C or ±0.004 × |t|, whichever is larger, -40 to 1000 °C
- Class 2 tolerance
- ±2.5 °C or ±0.0075 × |t|, whichever is larger, -40 to 1200 °C
Wire colours
| Positive | Negative | Sheath / Jacket | |
|---|---|---|---|
| IEC 60584-3 (international) | green | white | green |
| ASTM E230 / ANSI (USA), extension wire | yellow | red | yellow |
Colours identify the type, not the quality of the cable. Older national codes (e.g. BS 1843, DIN 43714, JIS) used other colours; check before reusing existing cable.
EMF at common temperatures (0 °C reference)
| Temperature (°C) | EMF (mV) | Sensitivity (µV/°C) |
|---|---|---|
| -200 | -5.891 | 15.26 |
| 0 | 0.000 | 39.45 |
| 100 | 4.096 | 41.37 |
| 200 | 8.138 | 39.97 |
| 400 | 16.397 | 42.24 |
| 600 | 24.905 | 42.51 |
| 800 | 33.275 | 41.00 |
| 1000 | 41.276 | 38.98 |
| 1200 | 48.838 | 36.49 |
Typical use and limits
The general-purpose type: wide range, inexpensive and accepted by almost every instrument. Two drift mechanisms limit long-term accuracy: short-range ordering in the positive leg between about 250 and 600 °C, and preferential oxidation of chromium ("green rot") in low-oxygen atmospheres at high temperature. For long service above about 800 °C, type N is often the better choice.
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