Tunable diode laser (TDLAS) based gas detectors and monitors – PKL Technologies Inc

Introducing Mr. Perry Kain from PKL Technologies

I recently met Mr. Perry Kain (President and Technical Director at PKL Technologies Inc.) from Edmonton, Canada and he is sharing with us some interesting information about tunable diode laser (TDLAS) based gas detectors and monitors.

TDLAS Open Path Advantages

•Specific to one gas – no interferences •Fast response times (< 1 second) •No consumables •Direct gas concentration measurement •Wide dynamic range (3+ orders) •Robust, reliable technology •Not affected by humidity, dust, heat, cold or rapid changes in temperature •No memory effects •Can’t be poisoned by exposure to ammonia •Better coverage (long open path monitoring covers large area) •Very low associated O&M costs

What else they provide...

PKL Technologies Inc. manufactures tunable diode laser (TDLAS) based gas detectors and monitors. Spectra-1 open path gas sensors are used in a variety of environmental and safety remote sensing applications. Spectra-1 gas sensors have been designed in a compact, easy to use, robust and portable format. Spectra-1 has been developed using proprietary hardware and software, to produce a low-cost alternative for open path gas monitoring. Spectra-1 can operate from a 1 to 1000 meter path length. Spectra-1 units are available in hydrogen fluoride (HF), ammonia (NH3), carbon dioxide (CO2), Carbon monoxide (CO), methane (CH4), acetylene (C2H2), ethylene (C2H4), and others. Spectra-1 is used for: portable gas detection, open path gas detection, landfill gas detection, continuous emission monitoring, emission reduction, ambient air monitoring, carbon dioxide monitoring, methane monitoring, HF monitoring, leak detection, fugitive emissions, gas monitoring and others.

Laser Gas Detection Principles of Operation

The identification of gas species by absorption spectroscopy goes back several decades. A molecule can be identified by its characteristic absorption spectra. If the frequency (or wavelength) of the infrared (IR) light source matches the vibrational frequency of the molecule, then light will be absorbed. The Beer-Lambert law is the linear relationship we use to calculate molecule concentration (ppm) from the characteristic absorption a molecule exhibits.

The Beer-Lambert law is written as: A = a(λ) * b * c

Where A is the measured absorbance, a(λ) is a wavelength-dependent absorptivity coefficient, b is the path length, and c is the molecule concentration.

Infrared Absorption spectra of Methane

One of these absorption features is chosen, that does not coincide with any other molecules absorption spectra. The wavelength of the tuneable laser is set very close to the absorption feature we want to measure. A laser is ideally suited for this as the light output is monochromatic. The laser wavelength is then scanned back and forth over this absorption feature. The resulting change in laser intensity when scanned over the absorption feature provides the information required to calculate the molecule concentration.

Open Path Laser Gas Detection

Open path gas detection is accomplished by transmitting the laser light through the area to be monitored for the specific molecule, and onto a photodiode for analysis. One way to perform this is to have the laser source and photodiode in one enclosure, and to use a reflective element to return the laser light back to the instrument.

TDLAS Open Path Advantages

•Specific to one gas – no interferences

•Fast response times (< 1 second)

•No consumables

•Direct gas concentration measurement

•Wide dynamic range (3+ orders)

•Robust, reliable technology

•Not affected by humidity, dust, heat, cold or rapid changes in temperature

•No memory effects

•Can’t be poisoned by exposure to ammonia

•Better coverage (long open path monitoring covers large area)

•Very low associated O&M costs

PKL Technologies Inc.

A206 2011 – 94th Street Edmonton,

Alberta, Canada T6N 1H1 780-486-9564

www.pkltechnologies.com sales@pkltechnologies.com

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