Using Tunable Diode Laser Absorption Spectroscopy (TDLAS)
The LGA-4000 is comprised of a laser transmitter, receiver with electronic interface, and optional central processing unit. The transmitter and receiver are installed directly opposite one another on the process pipe / duct work. The transmitter launches a laser beam with a selected wavelength across the diameter of the pipe to the receiver unit.
The resulting electrical signal is then sent to the electronic interface or central processing unit.
TDLAS Advantages & Benefits
TDLAS Theory of Operation:
Gas molecules absorb energy at specific wavelengths in the electromagnetic spectrum. At wavelengths slightly different than these absorption lines, there is essentially no absorption.
By transmitting a beam of light through a sample gas mixture containing the compound of interest, and tuning the beam's wavelength to one of the target gas's absorption lines and then measuring the absorption of that beam, we can monitor the concentration of the gas of interest over the beam's path length.
The laser's fast tuning capability is used to quickly and repeatedly scan the wavelength across the selected gas absorption line. For O2, the absorption line is 760 nanometers.
During the scanning process the portion of emitted laser power that is passed through the sample gas is measured by a photodetector. When the wavelength is tuned to be off of the absorption line, the transmitted power is higher than when it is on the line.
By measuring the relative amplitudes of the off-line to on-line transmission, the LGA-4000 is able to provide an accurate and highly sensitive analysis of the gas of interest.
Relevant Application Bulletins
- Applying the LGA-3500/LGA-4000 in the Steel industry
- Applying the LGA-3500/LGA-4000 in the Petrochemical industry
- Applying the LGA-4000 - Ammonia Slip Monitoring
- Trace moisture analysis in chlorine alkali, toluene diisocyanate (TDI), and polyurethane industries
- Trace moisture analysis in electron dichloride (EDC), carbon tetrachloride, and MCB in PVC and MDI industries
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