Question

The electrical output down a thermocouple circuit is detected by using:

• A. Wheatstone bridge
• B. Voltage balancing circuit
• C. Current sensitive device
• D. Current balancing circuit

Hint:

Thermocouples produce \textbf{millivolt-range output}; for accuracy, always use a \textbf{voltage balancing method}, not current-based detection.

Answer 1

The Correct Option is B

A thermocouple is a temperature-measuring device that works on the principle of the Seebeck effect, where a voltage is generated due to a temperature difference across the junctions of two different metals.
This voltage is typically in the millivolt range and needs to be accurately measured to determine the temperature.
To precisely measure this small voltage, a voltage balancing circuit is employed.
In this method:
- A known voltage is applied in opposition to the thermocouple voltage.
- The balancing continues until null deflection is achieved on a galvanometer, indicating that the applied voltage equals the thermocouple output.
- This approach allows for accurate and sensitive detection of the thermoelectric voltage.
Why not the others?
- A Wheatstone bridge is more suitable for resistance measurement (e.g., strain gauges).
- Current-sensitive devices and current balancing circuits are not appropriate because thermocouples produce voltage, not current as the primary measurable output.
Thus, the correct technique is the use of a voltage balancing circuit.