A thermocouple uses ------ measurement

The correct answer describes the method of measurement that a thermocouple employs. A thermocouple operates based on the principle of the thermoelectric effect, specifically the Seebeck effect, where two dissimilar metals joined at a junction produce a voltage that is directly proportional to the temperature difference between the junction and the reference point.

In the case of thermocouples, the measurement is made through a direct technique, where the temperature of the measured object affects the voltage produced across the junction. As such, the reading represents an immediate real-time measurement of temperature at the point where the thermocouple is placed.

This method is distinct from inferred or indirect measurements, which typically rely on calculations or estimations based on other parameters, rather than measuring the temperature at the point of interest directly. Understanding the mechanisms behind thermocouples reinforces the importance of direct measurements in applications like temperature sensing, making direct measurement a critical topic in instrumentation.