What is the open circuit output of a thermocouple?

What is the open circuit output of a thermocouple?

• A. 0 mv
• B. 30 mv
• C. 60 mv
• D. 90 mv

Answer: (B)

Open-circuit output is the voltage the thermocouple itself generates when there is a temperature difference between its two junctions and no load is connected. This is the Seebeck emf that appears across the two dissimilar metals, measured with a high-impedance meter. The magnitude is typically in the tens of millivolts and depends on the thermocouple type and the delta between the hot and reference junctions. In the given scenario, a modest temperature difference yields about 30 millivolts, so the open-circuit voltage would be around 30 mV. If the temperatures were the same, the output would be near zero. Larger voltages (like 60 or 90 mV) would require a much larger delta-T or a thermocouple with a higher Seebeck coefficient.

Open-circuit output is the voltage the thermocouple itself generates when there is a temperature difference between its two junctions and no load is connected. This is the Seebeck emf that appears across the two dissimilar metals, measured with a high-impedance meter. The magnitude is typically in the tens of millivolts and depends on the thermocouple type and the delta between the hot and reference junctions. In the given scenario, a modest temperature difference yields about 30 millivolts, so the open-circuit voltage would be around 30 mV. If the temperatures were the same, the output would be near zero. Larger voltages (like 60 or 90 mV) would require a much larger delta-T or a thermocouple with a higher Seebeck coefficient.