The FMS 2+ chlorophyll fluorimeter consists of a control unit housing all of the electronics, optics and light sources necessary to derive most common chlorophyll fluorescence parameters. These are optically linked to the sample by a statistically randomised fibre-optic cable that is positioned in the FMS/PTL PAR/temperature leafclip. The fibre-optic cable is also suitable for insertion into a range of sample containers such as oxygen electrode chambers, older gas-analysis chambers, petri dishes and microtitre plates.

The system may be operated in several different modes: serial connection to a Windows® PC enables real-time instrument control and data presentation. Captured data is simultaneously presented as a real-time chart recorder emulation and parameters-only format for easy identification of key experimental events. This PC mode of operation is suitable for development of complex protocols which may be programmed into the instrument using the simple drag-and-drop editor to generate user-defined scripts. These scripts automate the execution of experiments in the field, allowing complex protocols involving many control events to be operated with the same ease as single control event measurement such as . Once programmed, the FMS 2+ can be used as a stand-alone chlorophyll fluorimeter in either laboratory or field situations, running from internal batteries with all measurement data and calculated parameters saved to integral protected memory. The unit can store up to six experimental protocols, any one of which may be accessed and executed using the built-in menu system. When data collection is complete the results can be downloaded to the Windows® software for full analysis.

All of the light sources required for modulated measurement of common chlorophyll fluorescence parameters are self-contained within the instrument.