The sensor unit consists of an array of 3 ultra-bright red LEDs which are optically filtered to a peak wavelength of 650 nm at a maximum intensity of up to 3,500 µmol m-2 s-1 at the sample surface. The LEDs are focused via lenses onto the leaf surface to provide uniform illumination over the area of leaf exposed by the leafclip. An optical feedback circuit monitors and corrects changes in the LED output intensity and compensates for intensity changes caused by variation in ambient temperature.
Up to 1,000 recordings of between 0.1 seconds – 300 seconds may be saved in the onboard memory of the Handy PEA+. Calculated parameters may be viewed onscreen with more comprehensive data display achieved by transferring saved data via USB to a PC where the supplied PEA+ Windows® software allows a variety of numerical and graphical presentation options.