Which of the following are thermocouple types?

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

Answer: (D)

Thermocouple types are named by the metal pairs that make up the junction, and each type has its own characteristic sensitivity and operating range. The set with J, K, and T is the best choice because these three are the most commonly used in general instrumentation, offering a good mix of sensitivity, cost, and a wide usable temperature span. J is iron–constantan, good for moderate temperatures; K is chromel–constantan, versatile for a wide range; T is copper–constantan, excellent at low temperatures with high stability. Together they cover a broad range and are standard references in many manuals and specifications.

Other options list other valid thermocouple types as well, including high-temperature noble-metal types, but J, K, and T are the trio most frequently emphasized for typical instrumentation work due to their balance of performance and practicality.