The ECO FLNTU sensor is built by WETLab and combines a fluorometer and a nephelometer. It measures simultaneously the algal fluorescence and the turbidity. It is equipped with a bio-wiper that cleans the window with each measure.
The fluorometer
Principle
The fluorometer emits a blue light (470 nm) that excites the chlorophyll molecules that emits a red light (695 nm) when they get back to their initial energy level. The amount of reemitted light gives the chlorophyll concentration expressed in µg/l.
The chlorophyll a is an indicator of phytoplanktonic biomass. This pigment is present in any photosynthetic organism.
The measures range from 0.01 to 50 µg/l with a resolution of 0.01 µg/l.
The turbidity meter or the nephelometer
Principle
The turbidity measure is done withe the Wet Lab FLNTU nephelometer. This sensor detects the amount of light reemitted by particles in the environment. It emits a 700 nm spectrum light. The diffracted and / or refracted light by the particles is detected by a photo-diode. The matching electrical signal gives the amount of particles expressed in NTU.
The measured range from 0.01 to 25 NTU with a resolution of 0.01 NTU.