Instrument: Fluorometer
A fluorometer or fluorimeter is a device used to measure parameters of fluorescence: its intensity and wavelength distribution of emission spectrum after excitation by a certain spectrum of light. The instrument is designed to measure the amount of stimulated electromagnetic radiation produced by pulses of electromagnetic radiation emitted into a water sample or in situ.
A Walz Water PAM (pulse amplitude modulation) fluorometer was used to determine Fv:Fm. PAM fluorometers emit a range of pulsed lights to measure photosynthesis. The pulses of light are modulated, and the amplitude of the pulse of light governs its intensity. See more information from the manufacturer.