What does cold-junction compensation do in thermocouple measurements?

• A. It corrects for ambient humidity.
• B. It corrects for reference junction temperature.
• C. It calibrates the sensor to a standard.
• D. It filters electrical noise.

Answer: (B)

Thermocouples generate a voltage based on the temperature difference between the hot junction (where you’re measuring) and the reference or cold junction. Cold-junction compensation accounts for the actual temperature at that reference point so the measured voltage can be translated into the correct hot-junction temperature. In practice, the instrument measures the reference junction temperature (or knows it from a nearby sensor) and adjusts the signal accordingly. Without this, a nonzero reference temperature would skew the reading. This function is distinct from humidity effects, standard calibration, or noise filtering.