The basic principle of TDLAS relies on absorption spectroscopy. Gas molecules absorb specific wavelengths of light, converting photon energy into heat. Each gas has a unique “fingerprint” of absorption lines in the gas absorption spectrum.

The principle is similar to all TDLAS systems: a narrow-band laser is scanned across an absorption line. For each target gas, we optimize the light source based on its absorption spectrum, selecting the wavelength with the highest absorption and no interference from other gases.

Since we know the light intensity from the transmitter, any absorption by gas molecules reduces the light reachig the detector. If the target gas is present we will see a small dip in the light intensity reaching the receiver at that specific wavelength.

We turn the dip in the measured light intensity into an absorption spectrum, which allows us to calculate the gas concentration, temperature, and pressure. The technique is inherently self-referencing, and free from regular recalibrations.