||The BackScat fluorometers series 1100, 1200 and 1300 are designed for the in situ measurement of Chlorophyll a, phycoerythrin, Rhodamine B, sulforhodamine, humic acids (Gelbstoff), fluorescein, hydrocarbons and other fluorescent agents. The instruments of the series 1100 are measuring the fluorescence and optionally the turbidity by means of the elastically backscattered light entering the same window. The fluorometers of the series 1200 are designed to measure two fluorescent agents simultaneously through a single window. The series 1300 fluorometers are equipped with two windows for two different channels designed for those combinations of fluorescent agents, the spectra of which would cross each other either in emission or in excitation. The light source of this series of fluorometers is Xenon flashlight, which covers the spectral range from the UV near 300 nm to the IR at 1100 nm. A special UV Xenon flashtube extends the UV range to about 220 nm. The tuning to specific fluorescent agents is realized by special filters and dichroic beam-splitters. Spectrally improved photodiodes convert the received light to electric signals. Optional sensors: depth, turbidity, temperature, etc. The instrument has spectral ranges of 360 - 800 nm (Vis), with options: 320 nm - 1100 nm (UV1), 220 nm - 1100 nm (UV2). Filter units include: Chlorophyll a, Phycoerythrin, Phycocyanin (Vis), humic acids (UV1), Rhodamine (Vis), Sulforhodamine (Vis), Fluorescein (Vis), 3-cyclic hydrocarbons (UV2), others are available on request. The standard operational depth is 1500 m, but options include 3000 m and 6000 m depth ratings.