Which of the following lists the correct thermocouple types?

• A. J, K, E
• B. S, B, E
• C. J, K, T
• D. N, R, T

Answer: (C)

Thermocouple types are defined by the metal combinations they use and each type has a characteristic temperature range and behavior. In everyday instrumentation, three base-metal thermocouples stand out as the most common for general-purpose sensing: J, K, and T. Type K (Chromel–Alumel) is the workhorse, offering a wide usable range and good sensitivity at a reasonable cost. Type J (Iron–Constantan) covers moderate temperatures and is widely used, though it can oxidize at higher temperatures, which limits its life in extreme heat. Type T (Copper–Constantan) excels at lower temperatures and performs well in moist environments, with excellent stability there. Because these three together represent the typical, broadly used base-metal thermocouples in most instrumentation setups, they form the best, most universally recognized trio for a question asking for the correct thermocouple types. The other groupings mix in noble-metal types that are more specialized or use different characteristics, so they aren’t the standard trio for general-purpose use.