What type of sensor is often referred to as a "flame detector"?

The reference to a "flame detector" typically indicates an optical sensor. These sensors are designed to detect the presence of flame based on the specific wavelengths of light emitted by a fire, particularly in the infrared and ultraviolet spectrums. Optical sensors analyze the light patterns and can differentiate between the light produced by flames and other sources, making them highly effective for early fire detection in powerplant environments.

In contrast, pneumatic detectors rely on pressure changes to identify fire conditions, whereas thermal switches and thermocouples respond to temperature changes. While these types of detectors can contribute to fire detection and monitoring systems, they do not specifically detect flames in the way that optical sensors do. This specificity in detecting flames is what classifies optical sensors as flame detectors.