What principle does the pneumatic heat detection system use to detect leaks?

What principle does the pneumatic heat detection system use to detect leaks?

• A. Electrical current and resistance.
• B. Capacitive coupling.
• C. Magnetic flux.
• D. Optical attenuation.

Answer: (A)

Heat transfer from a heated sensor to the surrounding air is used to detect leaks. A heater is powered to keep the element at a set temperature, and the electrical resistance of the sensor is monitored. If a leak carries cool air past the element, the sensor cools slightly, causing its resistance to change. The detection circuitry tracks this resistance (and the resulting current needed to maintain the temperature) and triggers a leak indication when the change exceeds the threshold. This reliance on temperature-induced resistance change is why electrical current and resistance is the correct principle. Other methods—capacitance, magnetic flux, or optical attenuation—don’t describe how a pneumatic leak would influence a heated element’s temperature and resistance.

Heat transfer from a heated sensor to the surrounding air is used to detect leaks. A heater is powered to keep the element at a set temperature, and the electrical resistance of the sensor is monitored. If a leak carries cool air past the element, the sensor cools slightly, causing its resistance to change. The detection circuitry tracks this resistance (and the resulting current needed to maintain the temperature) and triggers a leak indication when the change exceeds the threshold. This reliance on temperature-induced resistance change is why electrical current and resistance is the correct principle. Other methods—capacitance, magnetic flux, or optical attenuation—don’t describe how a pneumatic leak would influence a heated element’s temperature and resistance.