The Z980 AquaPen is a handheld fluorometer that enables rapid and accurate measurement of photosynthetic parameters in suspensions. The measurements are carried out by a submersible optical probe. The AquaPen excels in a very high sensitivity (up to 10 ng Chl/L) and it can measure natural water samples containing low concentrations of phytoplankton. It can be favorably used both for the lab and field applications. The Z980 AquaPen includes the Protocol Update and Software and Data Transfer option with Bluetooth technology.