Thermocouple type comparison: E, J, K, N and T
E, J, K, N, T compared: temperature ranges, alloys, EMF tolerances.
| Type | Alloy | Temperature range | EMF tolerance | Details |
|---|---|---|---|---|
| Type E | Chromel / Constantan | −200 … +900 °C | ±1.5°C (0–275°C) / ±0.4% (275–900°C) | Type E overview |
| Type J | Iron / Constantan | −40 … +750 °C | ±1.5°C (0–275°C) / ±0.4% (275–750°C) | Type J overview |
| Type K | Chromel / Alumel | −200 … +1370 °C | ±1.5°C (0–375°C) / ±0.4% (375–1000°C) | Type K overview |
| Type N | Nicrosil / Nisil | −270 … +1300 °C | ±1.5°C (0–375°C) / ±0.4% (375–1000°C) | Type N overview |
| Type T | Copper / Constantan | −200 … +350 °C | ±0.5°C (−40–125°C) / ±0.4% (125–350°C) | Type T overview |
Values above are quoted from each product line's own datasheet fields. Confirm the alloy, diameter and tolerance class against your own specification before ordering.
Type E · −200 … +900 °C
Highest EMF output per degree (68 µV/°C) — best sensitivity among base metal thermocouples. Non-magnetic.
Type J · −40 … +750 °C
Higher EMF output than Type K in the 0–400°C range. Cost-effective due to iron positive leg. Good for reducing atmospheres.
Type K · −200 … +1370 °C
Industry standard for general-purpose high-temperature measurement. Wide temperature range, good oxidation resistance in clean oxidising atmospheres.
Type N · −270 … +1300 °C
Superior oxidation resistance vs Type K. No green-rot phenomenon. Longer service life in vacuum and inert atmospheres. Lower drift rate above 1000°C.
Type T · −200 … +350 °C
Best accuracy in sub-zero range (±0.5°C). Excellent corrosion resistance. Preferred for cryogenic and pharmaceutical applications.
Listed per type, taken from each datasheet's own stated limitations — the section most supplier comparison pages leave out.
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Type E
Limited high-temperature range compared to Type K/N. Not as widely adopted.
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Type J
Iron leg oxidises rapidly above 550°C. Not for oxidising atmospheres above 750°C. Not for vacuum or sulphur-containing atmospheres.
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Type K
Avoid reducing atmospheres (800–1050°C). Susceptible to green-rot chromium oxidation. Not for vacuum above 800°C without protection.
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Type N
Slightly higher cost than Type K. Less established EMF reference data compared to Type K.
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Type T
Copper leg oxidises above 350°C. Limited upper temperature range.
- Start from the operating temperature and check it against the range column above.
- Then check the EMF tolerance you actually need — the tighter the class, the more testing and certification each coil carries.
- Read the limitations section before committing; a type that is wrong for vibration, oxidising or reducing atmospheres will fail regardless of its tolerance class.
- Send the specification and we quote against it with the MTC and EMF calibration certificate scope included.
Frequently Asked Questions
Which thermocouple type covers the widest temperature range?
Type K reaches +1370 °C — the highest ceiling of the five — followed by Type N at +1300 °C, Type E at +900 °C, Type J at +750 °C and Type T at +350 °C. At the cold end Type N reaches −270 °C, Types E and K −200 °C, and Type J is limited to −40 °C.
Which types use Constantan as the negative leg?
Three of the five: Type E (Chromel / Constantan), Type J (Iron / Constantan) and Type T (Copper / Constantan). Type K pairs Chromel with Alumel, and Type N pairs Nicrosil with Nisil, instead.
Which type is the most accurate below 0 °C?
Type T — ±0.5 °C between −40 °C and 125 °C, the tightest sub-zero tolerance of the five and the only one quoted below 0 °C. Types E, J, K and N are all quoted at ±1.5 °C in their first range segment.
Which type should I choose for a general-purpose furnace above 1000 °C?
Type K is the industry standard in this band and the cheaper of the two. Type N also covers +1300 °C, with better oxidation resistance, no green-rot phenomenon and a lower drift rate above 1000 °C, at a higher cost. Check both against the atmosphere in your furnace — see the limitations above.
Bottom line: above 1000 °C choose between Type K and Type N — Type N costs more but resists oxidation and green rot. Below 400 °C, Type T is the most accurate and Type J the most cost-effective in reducing atmospheres. Type E is the sensitivity pick where the signal must survive electrical noise. All values above are quoted from each type's own datasheet fields.