Alternative to the dual-beam method for absorption measurement that uses a compensation flow cell to eliminate the sources of error introduced by the flow cell, the carrier medium and window contamination.
Fig. 10: Differential measurement method
The beam of light is divided and sent through two layers of different thickness. Both beams are influenced in the same way by window contamination so that the difference between both measuring values corresponds to a photometric measurement with an effective layer corresponding to the difference of both layer thicknesses.