NDIR against Metal Oxide Films in CO2 Measurement
NDIR sensors provide definitive CO2 accuracy through direct mid-IR light absorption, while low-cost metal oxide films infer CO2 via prone cross-reactive surface chemistry.
NDIR
Detection Technique
Non dispersive infrared spectroscopy employs ndir as a sensing method to identify specific gas molecules based on their unique absorption spectra. A light source sends infrared radiation through a chamber containing the gas sample toward a detector.
Spectral Filter
Narrow bandpass filters are placed in front of the sensor to block all wavelengths except the one where the target gas absorbs energy. This selection allows the system to isolate carbon dioxide from other gases like methane or water vapor. The filter must be thermally stable to prevent shifts in the transmission window.
Gas Identification
The reduction in light intensity at the specific wavelength indicates the concentration of the gas. This measurement follows a non linear relationship that requires a mathematical linearization during processing. Multiple sensors with different filters can be placed in a single chamber to detect several gases at once.
Accuracy Limit
Environmental factors like temperature and pressure change the density of the gas and the intensity of the light source. Built in sensors measure these conditions to apply real time corrections to the output. Long term drift is managed through the use of a reference channel that monitors the source without the gas interference.