With some measurements there is the problem that the use of immersion probes is not
possible as the diameter of the pipe is too small. The flow-through cell has been developed
for such on-line measurements. It has a stainless steel body. The optical windows of the sample compartment are made of sapphire. This also enables the cell to be used under high pressure.

Fibre-optic cables link the measuring cell
with the spectrometer. As with cell measurements, the light beam passes through the sample compartment only once. This results in very low values for stray light and improves the quality of the measurement. In the case of cold liquid samples, condensation on the optics of the collimator and the insides of the windows could occur. To avoid this the measuring cell has flushing attachments for dry, oil-free air.