Thermocouple EMF Reference Tables
Millivolt output vs temperature for all nine standardized thermocouple types. Cold junction reference 0°C. Per ASTM E230, E1751, E696 and NIST ITS-90 (NIST Monograph 175). Selected values at 50°C intervals.
Table Notes
All EMF values in millivolts (mV). Reference junction at 0.000°C. Values per NIST Monograph 175 (ITS-90) polynomial reference functions, which form the basis of ASTM E230, E1751, E696 and IEC 60584-1. Intermediate temperatures may be calculated using the polynomial coefficients in those standards. For full 1°C interval tables, consult NIST Monograph 175 directly (available free from NIST).
Type J — Iron / Constantan ASTM E230
Range: −40 to +750°C standard. Extended to −210°C (reduced accuracy).
| Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) |
|---|---|---|---|---|---|
| −210 | −8.096 | 200 | 10.779 | 500 | 27.393 |
| −150 | −6.500 | 250 | 13.555 | 550 | 30.210 |
| −100 | −4.633 | 300 | 16.327 | 600 | 33.102 |
| −50 | −2.431 | 350 | 19.090 | 650 | 36.071 |
| 0 | 0.000 | 400 | 21.848 | 700 | 39.132 |
| 50 | 2.585 | 420 | 22.952 | 750 | 42.283 |
| 100 | 5.269 | 450 | 24.610 | 760 | 42.922 |
| 150 | 8.010 | 480 | 26.276 |
Note: Sensitivity ≈ 51.7 µV/°C at 25°C. Sensitivity increases to ~59 µV/°C at 400°C, then decreases above the Curie point transition (~760°C for iron). Type J not recommended above 750°C in air due to iron oxidation.
Type K — Chromel / Alumel ASTM E230
Range: −200 to +1260°C standard. Extended to −270°C / +1372°C.
| Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) |
|---|---|---|---|---|---|
| −200 | −5.891 | 300 | 12.209 | 900 | 37.326 |
| −150 | −4.913 | 350 | 14.293 | 950 | 39.314 |
| −100 | −3.554 | 400 | 16.397 | 1000 | 41.276 |
| −50 | −1.889 | 450 | 18.516 | 1050 | 43.211 |
| 0 | 0.000 | 500 | 20.644 | 1100 | 45.119 |
| 50 | 2.023 | 550 | 22.776 | 1150 | 46.985 |
| 100 | 4.096 | 600 | 24.905 | 1200 | 48.838 |
| 150 | 6.138 | 700 | 29.129 | 1250 | 50.644 |
| 200 | 8.138 | 800 | 33.275 | 1260 | 51.292 |
| 250 | 10.153 | 850 | 35.313 | 1372 | 54.886 |
Note: Sensitivity ≈ 40.6 µV/°C at 25°C. Non-linear dip in sensitivity near 0°C due to magnetic transition in Alumel. Short-range ordering (SRO) can cause drift of 1–3°C below 300°C after thermal cycling.
Type T — Copper / Constantan ASTM E230
Range: −200 to +370°C standard. Extended to −270°C.
| Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) |
|---|---|---|---|---|---|
| −270 | −6.258 | 0 | 0.000 | 200 | 9.288 |
| −200 | −5.603 | 50 | 2.036 | 250 | 12.013 |
| −150 | −4.648 | 100 | 4.279 | 300 | 14.862 |
| −100 | −3.379 | 125 | 5.469 | 350 | 17.819 |
| −50 | −1.819 | 150 | 6.704 | 370 | 19.027 |
| −25 | −0.940 | 175 | 7.972 | 400 | 20.872 |
Note: Sensitivity ≈ 40.6 µV/°C at 25°C; increases to ~60 µV/°C at 350°C. Best sub-zero linearity and stability of all base-metal types. Copper conductor limits max service temperature due to oxidation above 370°C.
Type E — Chromel / Constantan ASTM E230
Range: −200 to +870°C standard. Highest EMF output of all standard types.
| Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) |
|---|---|---|---|---|---|
| −200 | −8.825 | 200 | 13.421 | 600 | 45.085 |
| −150 | −7.279 | 250 | 17.178 | 650 | 49.109 |
| −100 | −5.237 | 300 | 21.036 | 700 | 53.110 |
| −50 | −2.787 | 350 | 24.964 | 750 | 57.047 |
| 0 | 0.000 | 400 | 28.946 | 800 | 60.987 |
| 50 | 3.048 | 450 | 32.960 | 850 | 64.909 |
| 100 | 6.319 | 500 | 36.999 | 870 | 66.473 |
| 150 | 9.789 | 550 | 41.053 |
Note: Sensitivity ≈ 58.7 µV/°C at 25°C — highest of all standard types. Non-magnetic. Large EMF output gives best signal-to-noise ratio for low-level measurements.
Type N — Nicrosil / Nisil ASTM E230
Range: −200 to +1260°C standard. Improved long-term stability vs Type K above 1000°C.
| Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) |
|---|---|---|---|---|---|
| −200 | −3.990 | 300 | 9.341 | 900 | 28.455 |
| −100 | −2.407 | 400 | 12.974 | 1000 | 32.371 |
| −50 | −1.269 | 500 | 16.748 | 1050 | 34.341 |
| 0 | 0.000 | 600 | 20.613 | 1100 | 36.256 |
| 100 | 2.774 | 700 | 24.527 | 1200 | 43.846 |
| 200 | 5.913 | 800 | 28.455 | 1260 | 47.513 |
Note: Sensitivity ≈ 25.9 µV/°C at 25°C — lower than Type K, but more stable. Silicon additions suppress the ordering transitions that cause Type K drift. Preferred over Type K for long-term use above 1000°C in oxidizing atmospheres.
Type R — Pt-13%Rh / Pt ASTM E1751
Range: 0 to +1480°C standard. Noble metal — oxidizing atmospheres only above 700°C.
| Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) |
|---|---|---|---|---|---|
| 0 | 0.000 | 500 | 4.471 | 1100 | 11.846 |
| 100 | 0.647 | 600 | 5.583 | 1200 | 13.228 |
| 200 | 1.469 | 700 | 6.743 | 1300 | 14.629 |
| 300 | 2.401 | 800 | 7.950 | 1400 | 16.040 |
| 400 | 3.408 | 900 | 9.205 | 1480 | 17.366 |
| 450 | 3.933 | 1000 | 10.503 | 1769 | 21.101 |
Note: Sensitivity ≈ 10.0 µV/°C at 25°C. Low output requires high-quality nanovoltmeter. 1769.8°C = platinum melting point (ITS-90 fixed point). Must use alumina ceramic insulation above 1000°C — silica reacts with Rh.
Type S — Pt-10%Rh / Pt ASTM E1751
Range: 0 to +1480°C standard. ITS-90 gold point (1064.18°C) reference standard.
| Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) |
|---|---|---|---|---|---|
| 0 | 0.000 | 500 | 4.233 | 1100 | 11.361 |
| 100 | 0.646 | 600 | 5.239 | 1200 | 12.721 |
| 200 | 1.441 | 700 | 6.275 | 1300 | 14.095 |
| 300 | 2.323 | 800 | 7.345 | 1400 | 15.476 |
| 400 | 3.259 | 900 | 8.449 | 1480 | 16.588 |
| 450 | 3.741 | 1000 | 9.587 | 1064.18 | 10.579 |
Note: Type S historically used as the ITS-90 interpolating instrument between the Ag fixed point (961.78°C) and the Au fixed point (1064.18°C). EMF values for Type R and Type S are very close — verify type before use. Color codes are identical (ANSI and IEC).
Type B — Pt-30%Rh / Pt-6%Rh ASTM E1751
Range: +600 to +1700°C standard. Near-zero EMF below 50°C — cold junction compensation largely unnecessary.
| Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) |
|---|---|---|---|---|---|
| 0 | 0.000 | 700 | 2.431 | 1300 | 8.956 |
| 50 | 0.002 | 800 | 3.154 | 1400 | 11.062 |
| 100 | 0.033 | 900 | 3.957 | 1500 | 13.257 |
| 200 | 0.178 | 1000 | 4.834 | 1600 | 15.517 |
| 400 | 0.787 | 1100 | 5.780 | 1700 | 13.820 |
| 600 | 1.792 | 1200 | 6.786 | 1820 | 13.820 |
Note: Tolerance is percentage-only (no fixed °C limit). Both positive and negative conductors contain rhodium — highest oxidation resistance of all PtRh types. Not suitable below 600°C (insufficient EMF and tolerance specification). Near-zero EMF at room temperature means cold junction errors are minimal.
Type C — W5Re / W26Re ASTM E696 Vacuum / Inert Only
Range: 0 to +2315°C. Never use in oxidizing atmospheres at any temperature.
| Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) | Temp (°C) | EMF (mV) |
|---|---|---|---|---|---|
| 0 | 0.000 | 700 | 11.540 | 1600 | 27.388 |
| 100 | 1.545 | 800 | 13.277 | 1700 | 28.461 |
| 200 | 3.167 | 900 | 14.973 | 1800 | 29.422 |
| 300 | 4.832 | 1000 | 16.600 | 1900 | 30.283 |
| 400 | 6.504 | 1100 | 18.148 | 2000 | 31.060 |
| 500 | 8.148 | 1200 | 19.610 | 2200 | 32.277 |
| 600 | 9.843 | 1400 | 23.632 | 2315 | 32.773 |
Warning: Type C (W5Re/W26Re) becomes brittle after service above ~1200°C due to tungsten recrystallization. Treat as consumable above 1800°C. IEC 60584 does not define Type C — ASTM E696 is the sole standard. No IEC color code designation.