Thermocouple Selection Tool

Compare thermocouple types by temperature range, atmosphere compatibility, and AMS 2750 / CQI-9 requirements — then pick the right type for your furnace.

Thermocouple Type Comparison
Type Range Accuracy Atmosphere AMS 2750 Life Best For
K –200 to 1260 °C ±2.2 °C / 0.75% Inert, oxidising 3 months General purpose, carburising, annealing
N –270 to 1300 °C ±2.2 °C / 0.75% Inert, oxidising 3 months Higher stability, cycling furnaces
J 0 to 760 °C ±2.2 °C / 0.75% Reducing, vacuum 3 months Low-temperature, reducing atmospheres
S 0 to 1600 °C ±1.5 °C / 0.25% Oxidising, vacuum 6 months High-temp, aerospace, Nadcap
R 0 to 1600 °C ±1.5 °C / 0.25% Oxidising, vacuum 6 months High-temp, hardening, sintering
B 200 to 1820 °C ±0.5% Oxidising, inert 12 months Ultra-high-temp, vacuum sintering
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Selection Tool Features

  • Filter by process temperature, atmosphere, and accuracy class
  • AMS 2750 Rev G calibration interval by TC type and use class
  • Drift rate comparison — when to recalibrate vs replace
  • Wire gauge and sheath material recommendations
  • Noble metal vs base metal cost comparison
  • Compatibility with common controller input types

AMS 2750 Thermocouple Requirements

Use class Max calibration interval
Control TCs (Type 1, 2, 3) 6 months (noble), 3 months (base)
Load TCs (expendable) Single use
SAT reference TCs Per SAT frequency
TUS survey TCs Per TUS schedule

Choosing the Right Thermocouple for Your Furnace

Thermocouple selection is a balance between temperature range, atmosphere compatibility, accuracy requirement, calibration interval, and cost. Type K is the most widely used thermocouple in heat treatment — it covers virtually all carburising, annealing, and hardening temperatures up to 1260 °C and is suitable for most controlled atmospheres.

For aerospace applications governed by AMS 2750, thermocouple type dictates calibration interval and affects your Instrumentation Type classification. Noble metal thermocouples (S, R, B) require less frequent calibration but cost significantly more. Our selection tool walks you through the decision based on your specific process conditions and compliance requirements.

Find the Right Thermocouple Free

Answer 4 questions about your process and get a thermocouple recommendation with compliance notes.

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Related: AMS 2750 Pyrometry Tool · All Tools · Thermocouple Selection Guide