Optical Instrument
Spectroscopic gas detection relies on the absorption of infrared radiation at specific wavelengths characteristic of target gas molecules. An ndir gas sensor utilizes an infrared source, a sample chamber, and a bandpass filter to measure the concentration of gases like carbon dioxide. Because it does not require chemical reactions, the sensor provides a non-depleting method for continuous monitoring of gas concentrations.
Waveguide Geometry
Designing the optical path length of the measurement chamber determines both the sensitivity and the measurement range of the detector. The ndir gas sensor relies on a reflective chamber or waveguide to maximize the interaction of the infrared light with the target gas. A longer optical path allows the detection of lower gas concentrations, while a shorter path is preferred for high-concentration measurements to prevent signal saturation.
Drift Mitigation
Degradation of the infrared source or accumulation of dirt on the optical surfaces causes measurement drift over time. To counteract this, the ndir gas sensor often includes a dual-channel design with a reference channel filtered at a wavelength that is not absorbed by any target gas. Comparing the active signal to the reference signal allows the system to compensate for light source aging, temperature changes, and window contamination.
This differential measurement technique significantly reduces the need for manual zero-point calibration, making the sensor suitable for long-term deployment in remote or inaccessible monitoring locations.
Reference Calibration
Metrological accuracy is maintained through periodic calibration with certified span and zero gases. Calibration of the ndir gas sensor establishes the relationship between optical absorption and gas concentration, adjusting for non-linearities in the sensor response.
