Nondispersive infrared sensor

A nondispersive infrared sensor (or NDIR sensor) is a simple spectroscopic sensor often used as a gas detector. It is nondispersive in the sense of optical dispersion since the infrared energy is allowed to pass through the atmospheric sampling chamber without deformation.^[1]

NDIR-analyzer with one double tube for CO and another double tube for hydrocarbons

Principle

The main components of an NDIR sensor are an infrared source (lamp), a sample chamber or light tube, a light filter and an infrared detector. The IR light is directed through the sample chamber towards the detector. In parallel there is another chamber with an enclosed reference gas, typically nitrogen. The gas in the sample chamber causes absorption of specific wavelengths according to the Beer–Lambert law, and the attenuation of these wavelengths is measured by the detector to determine the gas concentration. The detector has an optical filter in front of it that eliminates all light except the wavelength that the selected gas molecules can absorb.

Ideally other gas molecules do not absorb light at this wavelength, and do not affect the amount of light reaching the detector however some cross-sensitivity is inevitable.^[2] For instance, many measurements in the IR area are cross sensitive to H₂O so gases like CO₂, SO₂ and NO₂ often initiate cross sensitivity in low concentrations. Part 1065.350(b) states that H₂O can interfere with an NDIR analyzer's response to CO₂. (http://www.ecfr.gov/cgi-bin/text-idx?sid=b09e0b356089f50988feae6565ed426a&c=ecfr&tpl=/ecfrbrowse/Title40/40tab_02.tpl)

The IR signal from the source is usually chopped or modulated so that thermal background signals can be offset from the desired signal.^[3]

Applications

References

↑ "Dispersive Waves". University of Saskatchewan. Akira Hirose. Retrieved 9 May 2016.
↑ "NDIR Gas Sensor Light Sources". International Light Technologies. Retrieved 9 May 2016.
↑ Seitz, Jason; Tong, Chenan (May 2013). SNAA207 - LMP91051 NDIR CO2 Gas Detection System (PDF). Texas Instruments.

External links

NDIR Gas Sensors Explained, The Gas Detector Encyclopedia, Edaphic Scientific Knowledge Base
NDIR Gas Sensor Lamp Selection Application Notes
NDIR Technology for gasoline exhaust
NDIR detectors for CO&CO₂ in internal combustion engine exhaust

Sensors

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Automotive, transportation	Air–fuel ratio meter Blind spot monitor Crankshaft position sensor Curb feeler Defect detector Engine coolant temperature sensor Hall effect sensor MAP sensor Mass flow sensor Omniview technology Oxygen sensor Parking sensors Radar gun Speed sensor Speedometer Throttle position sensor Tire-pressure monitoring system Torque sensor Transmission fluid temperature sensor Turbine speed sensor Variable reluctance sensor Vehicle speed sensor Water sensor Wheel speed sensor

Chemical	Breathalyzer Carbon dioxide sensor Carbon monoxide detector Catalytic bead sensor Chemical field-effect transistor Electrochemical gas sensor Electrolyte–insulator–semiconductor sensor Electronic nose Fluorescent chloride sensors Holographic sensor Hydrocarbon dew point analyzer Hydrogen sensor Hydrogen sulfide sensor Infrared point sensor Ion selective electrode Microwave chemistry sensor Nitrogen oxide sensor Nondispersive infrared sensor Olfactometer Optode Oxygen sensor Pellistor pH glass electrode Potentiometric sensor Redox electrode Smoke detector Zinc oxide nanorod sensor

Electric, magnetic, radio	Current sensor Electroscope Galvanometer Hall effect sensor Hall probe Magnetic anomaly detector Magnetometer MEMS magnetic field sensor Metal detector Planar Hall sensor Radio direction finder Test light

Environment, weather, moisture	Actinometer Bedwetting alarm Ceilometer Dew warning Electrochemical gas sensor Fish counter Frequency domain sensor Gas detector Hook gauge evaporimeter Humistor Hygrometer Leaf sensor Psychrometer Pyranometer Pyrgeometer Rain gauge Rain sensor SNOTEL Snow gauge Soil moisture sensor Stream gauge Tide gauge Weather radar

Flow, fluid velocity	Air flow meter Anemometer Flow sensor Gas meter Mass flow sensor Water metering

Ionising radiation, subatomic particles	Bubble chamber Cloud chamber Geiger counter Neutron detection Particle detector Scintillation counter Scintillator Wire chamber

Navigation instruments	Airspeed indicator Machmeter Altimeter Attitude indicator Depth gauge Fluxgate compass Gyroscope Inertial navigation system Inertial reference unit Magnetic compass MHD sensor Ring laser gyroscope Turn coordinator Variometer Vibrating structure gyroscope Yaw-rate sensor

Position, angle, displacement	Accelerometer Auxanometer Capacitive displacement sensor Capacitive sensing Gravimeter Inclinometer Integrated circuit piezoelectric sensor Laser rangefinder Laser surface velocimeter Lidar Linear encoder Linear variable differential transformer Liquid capacitive inclinometers Odometer Photoelectric sensor Piezoelectric accelerometer Position sensor Rate sensor Rotary encoder Rotary variable differential transformer Selsyn Sudden Motion Sensor Tachometer Tilt sensor Ultrasonic thickness gauge Variable reluctance sensor Velocity receiver

Optical, light, imaging	Charge-coupled device Contact image sensor Electro-optical sensor Flame detector Infrared Kinetic inductance detector LED as light sensor Light-addressable potentiometric sensor Nichols radiometer Optical fiber Photodetector Photodiode Photoelectric sensor Photoionization detector Photomultiplier Photoresistor Photoswitch Phototransistor Phototube Position sensitive device Scintillometer Shack–Hartmann wavefront sensor Single-photon avalanche diode Superconducting nanowire single-photon detector Transition edge sensor Tristimulus colorimeter Visible-light photon counter Wavefront sensor

Pressure	Barograph Barometer Boost gauge Bourdon gauge Hot-filament ionization gauge Ionization gauge McLeod gauge Oscillating U-tube Permanent Downhole Gauge Piezometer Pirani gauge Pressure gauge Pressure sensor Tactile sensor Time pressure gauge

Force, density, level	Bhangmeter Force gauge Hydrometer Level sensor Load cell Magnetic level gauge Nuclear density gauge Piezoelectric sensor Strain gauge Torque sensor Viscometer

Thermal, heat, temperature	Bimetallic strip Bolometer Calorimeter Exhaust gas temperature gauge Flame detection Gardon gauge Golay cell Heat flux sensor Infrared thermometer Microbolometer Microwave radiometer Net radiometer Quartz thermometer Resistance thermometer Silicon bandgap temperature sensor Special sensor microwave/imager Thermistor Thermocouple Thermometer

Proximity, presence	Alarm sensor Doppler radar Motion detector Occupancy sensor Passive infrared sensor Proximity sensor Reed switch Stud finder Touch switch Triangulation sensor Wired glove

Sensor technology	Active pixel sensor Back-illuminated sensor Biochip Biosensor Capacitance probe Carbon paste electrode Catadioptric sensor Digital sensors Displacement receiver Electromechanical film Electro-optical sensor Fabry–Pérot interferometer Fisheries acoustics Image sensor Image sensor format Inductive sensor Intelligent sensor Lab-on-a-chip Leaf sensor Machine vision Microelectromechanical systems Photoelasticity Quantum sensor Radar Ground-penetrating radar Synthetic aperture radar Radar tracker Sensor array Sensor fusion Sensor grid Sensor node Soft sensor Sonar Staring array Transducer Ultrasonic sensor Video sensor technology Visual sensor network Wheatstone bridge Wireless sensor network

Related	List of sensors

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