The emitter-detector unit, of the CUVETTE version features a cylindrical holder for a 15 mm diameter quartz glass cuvette (WATER-K). The cuvette is surrounded by light-emitting diodes (LED) delivering PAM measuring light and actinic illumination to the sample.

Detection of fluorescence at wavelengths longer than 710 nm occurs at the bottom of the cuvette. Best results are achieved using sample volumes between 2 and 3 ml.


The emitter detector unit is available with two different LED colors. The blue LED version (WATER-ED/B) exhibits lowest stray light interference. This WATER-ED/B has additional far-red LEDs light source for fast PS I-driven opening of PS II reaction centers required for evaluations of Fo’ fluorescence levels.

The red LED version (WATER-ED) is frequently used to analyze cyanobacteria which tend to absorb inefficiently in the blue: this version is available with far-red or blue photosystem I light.