A Tunable Diode Laser (TDL) works by tuning the wavelength of a diode laser across the absorption peak of the gas of interest (e.g. oxygen), which creates the fingerprint of this gas, which can be used to determine its concentration. Gasmet Technologies uses a specific kind of TDL known as VCSEL (Vertical Cavity Surface Emitting Laser), which have more circular output, more competitive price and are easier to manufacture than regular TDL’s.
TDL has several advantages over traditional techniques:
- Paramagnetic sensors require moisture free sample, which means that a separate sample conditioning unit is needed. With a VCSEL the sample can be measured without sample conditioning.
- Finally, with a VCSEL there’s very little concern of interference from other gases, since the VCSEL utilizes a part of the spectrum where O2 absorption band is virtually interference free from other gases.
Gasmet Technologies is the only company in the world that has incorporated a complete VCSEL assembly into the enclosure of an extractive FTIR gas analyzer. Hence a single Gasmet CX4000 FTIR gas analyzer is capable of measuring H2O, CO2, CO, NO, NO2, N2O, SO2, HCl, HF, NH3, TOC and O2 (and many other gases). The VCSEL uses the same rhodium-gold coated sample cell as the FTIR gas analyzer. The sample cell is designed to withstand very high concentrations of H2O and corrosive gases, such as HCl and SO2. The O2 concentration is stored on the hard-drive of an industrial computer along with other measurement results.