Our LSE monitors are able to detect NH3 or N2O when its concentration is in the ppb-range. This is achieved by implementing a photoacoustic detection technique.
An infrared laser light beam is directed through a sample cell. If the gas of interest is present in this sample cell, a fraction of the laser light is absorbed. This results in a small pressure increase of the gas in the cell. By modulating the laser beam, pressure waves are created. These pressure waves are amplified and detected with small microphones. By scanning the laser light over a small spectral range, the concentration of the gas of interest can be determined from the recorded microphone signal.