What device measures temperature using two dissimilar conductors?

What device measures temperature using two dissimilar conductors?

• A. Thermometer
• B. Pyrometer
• C. Barometer
• D. Thermocouple

Answer: (D)

Two dissimilar metals joined at a junction produce a voltage when their temperatures differ. This is the Seebeck effect: heating one junction creates an electrical potential that is proportional to the temperature difference between the hot junction and a reference junction. By measuring that voltage and knowing the reference temperature (or compensating for it), you can determine the temperature at the hot junction. That is exactly how a thermocouple works, using two different conductors to convert a temperature difference into an electrical signal for measurement. In contrast, a thermometer relies on liquid expansion in a glass tube, a pyrometer uses emitted radiation to infer temperature, and a barometer measures atmospheric pressure. Hence, the device described by two dissimilar conductors is a thermocouple.

Two dissimilar metals joined at a junction produce a voltage when their temperatures differ. This is the Seebeck effect: heating one junction creates an electrical potential that is proportional to the temperature difference between the hot junction and a reference junction. By measuring that voltage and knowing the reference temperature (or compensating for it), you can determine the temperature at the hot junction. That is exactly how a thermocouple works, using two different conductors to convert a temperature difference into an electrical signal for measurement.

In contrast, a thermometer relies on liquid expansion in a glass tube, a pyrometer uses emitted radiation to infer temperature, and a barometer measures atmospheric pressure. Hence, the device described by two dissimilar conductors is a thermocouple.