Direct immersion in water flows (0-20 m depth), springs or as laboratory fluorometer for fast sample measurements. Can be as well used with quick-connect fittings and 6 mm tubings. Up to 4 light sources cover the whole optical spectrum. Casing : stainless steel. Optional: aluminium. The sonde connects through a 4-wire signal cable to a waterproof box hosting a datalogger and 1 or 2 batteries. The datalogger provides power, timing, clock and data storage capability. The signal is transmitted in digital form.