The DC voltage generated by a thermocouple or thermopile is directly related to what factor?

The DC voltage generated by a thermocouple or thermopile is directly related to the temperature difference between the junctions. A thermocouple consists of two dissimilar metals joined at two points, creating two junctions. When there is a temperature difference between these junctions, it generates a voltage due to the Seebeck effect, which states that a voltage is produced when there is a temperature gradient across two different conductive materials.

This voltage is proportional to the temperature difference between the hot junction, which is exposed to the measured temperature, and the cold junction. Therefore, the larger the temperature difference, the higher the voltage output from the thermocouple or thermopile, which is essential for accurately measuring temperature in various applications, including gas equipment.

The other options do not directly correlate with the voltage output from a thermocouple or thermopile. Measurement of circuit resistance, voltage supply, or gas flow amount does not influence the fundamental principle of how thermocouples and thermopiles operate regarding voltage generation based on temperature differences.