G2 Gas Fitter Practice Exam

If multiple flame sensors are properly installed, which one would you expect to have the fastest detection response time?

1. Flame rod

2. Thermocouple

3. Photoelectric sensor

4. Bimetallic sensor

The correct answer is: Flame rod

The flame rod is known for having the fastest detection response time among various flame detection devices. This is primarily due to its design and operational mechanism. The flame rod detects the presence of flame through the ionization of combustion gases. When a flame is present, it ionizes the air around it, creating a small electric current. This current can be detected almost instantaneously, allowing for rapid identification of flame presence and effectively ensuring safety in gas-fired applications. In contrast, other types of sensors, such as the thermocouple, rely on measuring temperature changes over a broader timeframe, which can lead to slower response times when detecting flame presence. Photoelectric sensors, while effective in certain conditions, typically require the flame to emit light that can be detected, which may introduce a lag depending on the intensity and nature of the combustion. Bimetallic sensors work based on temperature changes as well, which can also create a delay in response. In summary, the flame rod's ability to leverage electric ionization for immediate detection makes it the most responsive option in the context of flame sensing technology.