Non-Dispersive Infrared (NDIR) Gas Detection
Non-Dispersive Infrared (NDIR) quantifies known gases. While the technology has long existed, LumaSense Technologies’ ANDROS® brand pioneered NDIR gas analysis for automotive emissions and patient monitoring.
Non-dispersive Infrared (NDIR) Technology
Non-Dispersive Infrared (NDIR) technology utilizes a broadband infrared (IR) emitter, which covers all of the wavelengths of interest for a given set of gases to be measured. Optical Band Pass filters allow that portion of IR wavelengths at which a specific gas absorbs IR energy. For typical gasoline exhaust, the IR spectra are shown below.
Mathematical Model Derived from Actual Spectrographic Data
Each band pass filter is attached to an infrared sensor (detector). The detector produces a signal that is proportional to the amount of IR energy absorbed by the gas of interest. This signal is electronically processed to develop gas concentration information reported in engineering units of interest.
NDIR is the heart of our suite of SmartDGA products designed for the Energy industry for Dissolved Gas Analysis (DGA) of transformers and load tap changers (LTCs).
With ANDROS® NDIR modules, the cost of gas measurement is greatly reduced because our modules can measure multiple gases and field calibration is not needed using our unique single path approach.
Andros NDIR Technology
As an OEM only supplier, the focus of our Andros NDIR designs is to address specific measurement needs for the more common measurement applications. This is accomplished by selecting the appropriate Optical Band Pass Filters required for the measurement. Our goal is to develop NDIR technology that can be mass-produced while maintaining high performance, high quality and reliability, all at a reasonable cost to our customers.
Key features of the design:
- High reproducibility between production runs
- Automated pre-inspection, set up, calibration and final verification
- Well-defined communications protocol to facilitate HOST software development
- Minimal customer requirements for field span
- Modular functionality for serviceability
- Conforms to current world wide requirements such as RoHS compliance
- Manufactured in accordance with ISO 9001: 2000 and ISO 13485
The main components of NDIR gas sensors are: an infrared (IR) source (lamp), a gas sample chamber or light tube, an optical bandpass filter and the infrared detector. The gas is pumped or diffuses into the sample chamber and the gas concentration is measured optically by its absorption of a specific wavelength in the IR spectrum. The IR light is directed through the sample chamber towards the detector. The detector has an optical filter in front of it that eliminates all light except the wavelength that the selected gas molecules can absorb (see diagram).
The IR signal from the source is modulated so that thermal background signals can be offset from the desired signal. In some applications, it may be necessary to compensate for the presence of non-target gases which absorb in the same portion of the IR spectrum.
Using an automated calibration process provides the capability to fully characterize each gas channel for response curve fit and gas channel interference correction. This process is performed at multiple temperatures to determine each channel's temperature coefficient. At the completion of a successful calibration, the calibration curve data and compensation coefficients are stored in the unit's flash memory.
Our applications engineers and scientists work closely with customers to determine what is required for a precise and accurate gas measurement.