Multi-Pass LaserGas Monitor
The Multi-Pass monitor is, in difference to the other models, an extractive monitor in which the gas is led into a special measurement cell, a so-called Herriott cell, where the laser beam is reflected multiple times between two spherical mirrors. This is why a long (11,4 m) optical path length can be achieved making the instrument able to detect very low gas concentrations (down to ppb levels).
The most common applications for the Multi Pass monitor is trace measurement of contaminants in pure gasses, low ppm H2S measurement in process gases and ppm NO measurement for emission control.