The new OS5p+ is the most advanced addition to the ADC:OSI range of Chlorophyll Fluorometers. Weighing just 1.4kg and offering 12 hours of continuous use, the battery operated OS5p+ is set to offer new levels in portability and performance for a field pulse modulated fluorometer. Both ambient light and dark adaptation parameters may be determined by the OS5p+ including Fo, Fm, Fv/Fm, Fv/Fo, Y(II), Ft, Foq and Fms. Photochemical and non-photochemical quenching coefficients such as qP, qN and NPQ can be calculated. The OS5p+ offers researchers exceptional control over each experiment. This includes source intensity, saturating pulse intensity and a sampling rate of up to 10,000 samples a second. A two channel (660nm / 450nm) modulating light is provided, as is a 735nm LED for Fod determinations.