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NDIR Sensor Types
Non-Dispersive Infrared (NDIR) CO2 Sensor
- Example: NDIR CO2 sensor
- Infrared absorption of CO2 molecules at a specific wavelength of 4.26 μm
- Sensor consists of IR source, light path, active detector and reference detector
- Concentration of CO2 determines intensity of light striking active detector
- Reference detector provides a real-time signal to compensate the variation of light intensity due to ambient or sensor itself/
Single wavelength NDIR sensors
- Affected by:
- Humidity
- Temperature
- Pressure
- Aging of detector
- Dust
- Aging of IR-emitter
Double wavelength NDIR sensors
- Affected by:
- Humidity
- Temperature
- Pressure
- Aging of detector
- Not affected by:
- Dust
- Aging of IR-emitter
- Commonly used in many portable instruments
GfG IR sensor (Note longer pathlength)
"4 Series" sized format used by City Tech, Dynament and E2V infrared sensors (Note shorter pathlength)
Three wavelength NDIR sensors
- Simultaneous measurement CO2 and combustible gas
- LEL: 3.3 μm
- CO2: 4.3μm
- Ref: 4.0μm
Light path through two wavelength NDIR sensor
- Affected by:
- Humidity
- Temperature
- Pressure
- Ageing of detector
- Not affected by:
- Dust
- Ageing of IRemitter
Catalytic pellistor combustible gas response curves
Two wavelength NDIR combustible gas response curves
Next on the horizon: Four wavelength NDIR combustible gas sensors
- Measure at two wavelengths for combustible gas
- Measure at one reference wavelength
- Measure water vapor at another wavelength and deduct interfering effect from combustible gas reading
Four wavelength NDIR combustible gas response curves
Side by side comparison
