Physical property analyzers – For years refineries are measuring the formation of crystals once the temperature drops in gasoil (Diesel).
The measuring principle is simple, trap the sample in a flow-through cell, cool it, while a light beam passes the sample. Once scattering is detected in the flow through cell caused by the formation of crystals the Cloud Point is determined based on the current temperature at that moment.
Light path design for physical property analyzers
The 90-degree geometry makes a big difference. Firstly, the signal to noise ratio is much lower as the detector is essentially looking for a small increase in light intensity against a zero (dark) background unlike non physical property analyzers where crystal formation attenuates light from the 100% light transmission, this is just basic physics easy to visualize.
Secondly the Icon 90-degree geometry is impervious to color variation and small amounts of dissolved water, it is simply seeing reflected light from a crystal whereas others design of detector has some light attenuation due to color changes and water, it is far more complex and maintenance intensive than needed and not as sensitive.
On a historical note, back in the day of Hone Instruments, Total had an analytical instruments research center and held the patent on the 90-degree geometry for Cloud and Freeze Points, it is Totals design and idea. Hone Instruments licensed the technology from Total and paid a royalty for each analyzer sold, Obviously the patent expired after 20 years so anyone can use the idea, but the fact remains the idea for the 90-degree geometry comes from Total originally and is by far the best way of doing the do.
Looking at ICON ‘s physical property analyzer design, they have improved on the original Total design with modern LED and detector technology, the use of the vacuum chamber eliminates moisture from the area around the cell, light source and detector thus eliminates optical issues due to moisture and ice from the ambient air and greatly lowers maintenance requirements as the detector electronics and detector and light source is dry and does not see moisture from the ambient air.