The PAM-2500 chlorophyll fluorometer is an extremely compact and powerful measuring system. All optical and electronic components are located in a 23 cm x 10.5 cm x 10.5 cm housing. The light sources of the PAM-2500 are light-emitting diodes (LEDs) permitting quasi-rectangular light intensity changes.
The PAM-2500 employs measuring light of 630 nm consisting of 1 μs pulses given at frequencies from 10 Hz to 200 kHz. Strong red actinic light of 630 nm is provided by a Chip-On-Board LED array. The fluorometer also features a blue actinic light source having the peak emission at 455 nm. In addition, a far-red LED with peak at 750 nm permits selective excitation of PS I.
The PAM-2500 chlorophyll fluorometers employs pulse-amplitude-modulated (PAM) measuring light to excite chlorophyll fluorescence. The intensity of the PAM excitation light can be sufficiently low for monitoring fluorescence yield without affecting the state of photosynthesis.
The resulting modulated chlorophyll fluorescence is detected with high sensitivity and selectivity, but the fluorometer is virtually insensitive to even strong unmodulated light like full sunlight or saturation pulses at up to 25,000 μmol m-2 s-1.
In addition to the current fluorescence yield in continuous light (Ft) and the maximum yield during saturation pulses (Fm or Fm') it is also possible to determine the minimum yield after dark-acclimation (Fo) or in illuminated state (Fo').
The PamWin-3 software calculates automatically four quenching coefficients (qP, qL, qN, and NPQ), the effective yield of PS II photochemistry (Y(II)=ΔF/Fm') and the complementary yields of non-photochemical energy dissipation (Y(NO) and Y(NPQ)) as well as the apparent electron transport rate (ETR).