A device that generates a voltage proportional to temperature difference is called a

A device that generates a voltage proportional to temperature difference is called a

• A. Thermocouple
• B. Thermistor
• C. RTD
• D. Diode

Answer: (A)

The key idea is the Seebeck effect, where two dissimilar metals joined at a sensing point produce a voltage when there is a temperature difference between that point and the other ends of the wires. A thermocouple is exactly this setup: two different metals joined together at the tip, with a voltage generated that is roughly proportional to the temperature difference between the sensing junction and the reference ends. This small voltage can then be measured and converted to temperature. It’s a common, simple way to sense temperature in HVAC systems, and it inherently responds to temperature differences rather than absolute temperatures alone, which is why it’s described this way. Thermistors and RTDs sense temperature by changing their resistance with temperature, not by generating a voltage due to a junction temperature difference. A diode’s voltage changes with temperature too, but that’s a different mechanism tied to the diode’s forward voltage drop, not the two-junction Seebeck voltage that a thermocouple produces.

The key idea is the Seebeck effect, where two dissimilar metals joined at a sensing point produce a voltage when there is a temperature difference between that point and the other ends of the wires. A thermocouple is exactly this setup: two different metals joined together at the tip, with a voltage generated that is roughly proportional to the temperature difference between the sensing junction and the reference ends. This small voltage can then be measured and converted to temperature. It’s a common, simple way to sense temperature in HVAC systems, and it inherently responds to temperature differences rather than absolute temperatures alone, which is why it’s described this way.

Thermistors and RTDs sense temperature by changing their resistance with temperature, not by generating a voltage due to a junction temperature difference. A diode’s voltage changes with temperature too, but that’s a different mechanism tied to the diode’s forward voltage drop, not the two-junction Seebeck voltage that a thermocouple produces.