Introduction
Pyroelectric sensors are widely used in flame detectors for industrial safety systems. Unlike motion detection, flame detection relies on sensing the characteristic flicker of flames and their spectral signature.
Flame Characteristics
Flames from hydrocarbon fires have two key properties useful for detection:
- Spectral emission: Strong emission bands from CO2 at 4.3 µm.
- Flicker frequency: Flames flicker at characteristic frequencies, typically 1-20 Hz.
How Pyroelectric Sensors Detect Flames
- An optical filter that passes only the flame-specific wavelength (e.g., 4.3 µm for CO2).
- A pyroelectric detector that responds to modulated IR (the flame flicker).
- Signal processing that looks for the characteristic flicker frequency.
Multi-Spectral Flame Detection
To reduce false alarms, professional flame detectors use multiple sensors with different filters:
- Channel A: Flame wavelength (e.g., 4.3 µm).
- Channel B: Reference wavelength (e.g., 5.0 µm) where flames don’t emit.
Applications
- Industrial plants: Petrochemical, oil & gas, power generation.
- Aircraft hangars: Detection of fuel fires.
- Mining: Conveyor belt fire detection.
Conclusion
Pyroelectric sensors are a proven technology for flame detection. By combining spectral filtering and flicker analysis, they provide reliable fire detection.