The ALGcontrol uses fluorescence excitation for detection. When chlorophyll molecules absorb light, a fraction of the energy absorbed is reemitted as fluorescence. Algae of the same classes contain a similar quantity and quality of pigments, their fluorescence excitation spectrum (with a fixed emission wavelength at 680nm) is significant. Thus, it is possible to differentiate divisions of algae by their fluorescence excitation spectrum. Other fluorescing matter (for example, DOM = dissolved organic matters measured with the 365nm wavelength and turbidity, measured with the 710nm wavelength) are detected to enhance the accuracy of the ALGcontrol.

LEDs for fluorescence excitation

The ALGcontrol uses 7 Light Emitting Diodes or LEDs for fluorescence excitation. The LEDs emit light at 7 selected wavelengths (365nm, 450nm, 525nm, 570nm, 590nm,615nm and 710nm). The LEDs in l are switched on, one after the other, at high frequency. The fluorescence signal for each LED is measured and averaged during a pre-defined time. The concentration of the algae will be calculated and the results are displayed in a graph. Correction for other fluorescing matters (DOM and turbidity) will also be calculated automatically.
The ALGcontrol can also be integrated into the TOXcontrol to have algae and toxicity monitoring in one sample.