Breath analysis Fire detection Leakage detection Process control Gas Detection Session: Current and Future Areas of Application for MIR technologies Combustion control Peter Geiser, Norsk Elektro Optikk Air quality control Food quality control Emission control Environmental monitoring Security control
Norsk Elektro Optikk (NEO) NEO is a SME and was founded in 1985 as an offspring of the Norwegian Defense Research Establishment. Early idea to do research for the offshore oil and gas industry, and underwater optics. Space projects for the European Space Agency (ESA) from the beginning to mid-nineties and new activities in recent years. Research in electro optics with the objective to develop state of the art products for an international market; mainly in hyperspectral imaging and gas sensing. Worldwide market coverage through distributors, OEM manufacturing agreements and license agreements. By end of 2013 approx. 7000 gas sensors sold
In principle we can divide gas sensors into two categories: Compact ones for everyday life Fire detector Alcohol detector Lambda probe Sources: 1. http://joyequipment.com/products 2. http://www.buybreathalyzer.ca/breathalyzer.html 3. http://www.mekonomen.se
and then there are bigger ones for industrial use. Emission Monitoring Combustion Control Process Control Sources: 1. NEO 2. http://www.icg.group.shef.ac.uk 3. Bernt GmbH
There are many different techniques to measure gases: Metal Oxide Sensors Opto-chemical Sensors Biomimetic Sensors Catalytic Bead Sensors Capacitance Sensors Electrochemical Sensors Thermal Conductivity Sensors Optical Sensors Field Effect Transistor Sensors MEMS Resonator Sensors
Optical Sensors: Nondispersive Infrared Spectroscopy Gas type: Theoretically any gas that absorbs in the IR Principle of operation: IR light is directed through a gas cell. The detector has an optical filter in front that eliminates all light except the wavelength that the selected gas molecules can absorb. Advantages: - Selectivity - Compact - Fast response time c(methane) = 10 ppm Optical path length = 10 cm Pressure = 1 atm Temperature = 23 C Disadvantages: - Not well suited for multi-gas detection - Can be affected by humidity - Cross-interference - Higher costs Source: http://www.intlsensor.com/pdf/infrared.pdf
Optical Sensors: Tunable Diode Laser Spectroscopy Gas type: Theoretically any gas Principle of operation: The wavelength of a cw single-mode laser is scanned over an absorption line. This allows interference-free measurements also in complex gas mixtures. Scanning range To increase sensitivity detection is moved to the second harmonic is used to determine the concentration.
Optical Sensors: Tunable Diode Laser Spectroscopy This allows a very selective detection of gases, since each species has its own characteristic absorption spectrum (fingerprint). NIR spectrometer: 10-6 [rel. abs.] CO LDL approx. 30 ppm m @ 1.6 µm 10-5 [rel. abs.] CO LDL approx. 0.3 ppm m @ 2.3 µm MIR spectrometer: 10-4 [rel. abs.] CO LDL approx. 0.02 ppm m @ 4.6 µm Advantages: - Selectivity - Sensitivity - Fast response time Disadvantages: - More complex system - High costs
Optical Sensors: Next generation of TDLS sensors Reduce size, increase functionality, reduce price
Optical Sensors: Example Application Which molecules to detect? Carbon monoxide (CO) Carbon dioxide (CO 2 ) Water vapor (H 2 O) What are possible applications? Fire detector and air quality monitor (Process control in steel plants) Which detection technique could be used? Short absorption path (e.g. 10 cm) Highly compact multi-pass cells Photo acoustic detection
Optical Sensors: Wavelength selection (overview) Water vapor (1 % ) Methane (1.76 ppm) Carbon dioxide (400 ppm) Nitrogen dioxide (317 ppb) Carbon monoxide (200 ppb) Oxygen (21 %) Optical path length = 10 cm Pressure = 1 atm Temperature = 23 C Source: HITRAN2012
Optical Sensors: Wavelength selection (1.6 µm) Carbon dioxide (400 ppm) Carbon monoxide (10 ppm) Optical path length = 10 cm Pressure = 1 atm Temperature = 23 C Source: HITRAN2012
Optical Sensors: Wavelength selection (2.3 µm) Carbon dioxide (400 ppm) Carbon monoxide (10 ppm) Optical path length = 10 cm Pressure = 1 atm Temperature = 23 C Source: HITRAN2012
Optical Sensors: Wavelength selection (4.6 µm) Carbon dioxide (400 ppm) Carbon monoxide (10 ppm) Water vapor (1 %) 200 cm -1 Optical path length = 10 cm Pressure = 1 atm Temperature = 23 C Source: HITRAN2012
Optical Sensors: What do we need? Operation: cw single-mode Wavelength: 2100 cm -1 2300 cm -1 4.35 µm 4.75 µm Tuning range: 200 cm -1 Line width: 10-4 cm -1 Operating temperature: +10 C +40 C Optical power: a few mw for optical detection more for photo acoustic detection Power consumption: < 1 W Price: Emission/Process control: 3000 /unit Mass-Market: << 300 /gas Array of Quantum Cascade Lasers Micro External Cavity Lasers Interband Cascade Lasers with Binary Superimposed Gratings
Summary Tunable Diode Laser Spectroscopy with widely tunable laser sources and highly compact detection techniques is a very promising combination and provides the opportunity to Increase the functionality of gas sensors, Reduce the size of current TDLS sensors, Reduce the price. This auspicious combination will open up many new and exciting possibilities in gas sensing. Thank you for your attention!
Additional information: Compact electronics