COSA Xentaur Xentaur XDTL-HT User Manual
Page 9
Theory of Operation
9
In typical laser absorption instruments, light beam is reflected on one or two mirrors inside the sample
cell before reaching to the photodetector. When the mirror becomes fouled due to particulates or
contamination, measurement will no longer be possible. The angle of reflection may change and the
received light intensity may decrease too much affecting the calibration. Unlike these instruments, the
XTDL-HT™ does not use any mirror in its sample cell; it uses a black body target allowing light to scatter
inside the cell. It measures the water vapor concentration as a ratio of the harmonic amplitude to the
absorbed light intensity. This allows accurate measurement regardless of how much light is received
from scattering.