PSI Fluormeters include:

  • Double-Modulation Fluorometers
  • Algal Online Monitor and OnlineFlow Fluoromete, for the continuous monitoring of  photosynthetic microorganisms.

PSI fluorometers measure:
Various Chl fluorescence parameters, ratios, and quenching coefficients that provide information on the functionality of the photosynthetic apparatus. These are five basic fluorescence parameters – F0, Fm, F0, Fm’, Fs – and a number of differences and fluorescence ratios. Such as, for instance:

  • Maximum quantum yield of Photosystem II
  • Non-photochemical quenching NPQ
  • Effective quantum yield of Photosystem II
  • Non-photochemical quenching of variable Chl fluorescence
  • Photochemical quenching of variable Chl fluorescence

Other supported protocols:

  • Flash fluorescence induction (one flash)
  • Fast OJIP transients
  • Rapid QA-reoxidation kinetics
  • S-states
  • Effective antenna size
  • PSII connectivity (J parameter)

How PSI fluorometers measure:
Measured fluorescence emission is excited by a set of light emitting diodes that generate measuring flashes. The photochemistry is driven by single-turnover flashes or by continuous actinic irradiance. The FL3500 has two input channels. One channel is used for a PIN photodiode with 1 MHz A/D converter and 16-bit resolution. The second channel can be configured according to a customer’s request.


  • Double-Modulation Fluorometer FL 3500 measures Chl-fluorescence signal with a time resolution of up to 1 µs in the Fast FL3500/F version or up to 4 µs in the Standard FL3500/S version.

The core of the instrument is the measuring optical head which contains a standard cuvette for sample suspensions (10 x 10 mm base, up to 4 ml of internal volume). Measured fluorescence emission is excited by a set of light-emitting diodes that generate short measuring flashes; the photochemistry is driven by single-turnover flashes or by continuous actinic irradiance. Chlorophyll fluorescence is detected by a PIN photodiode and digitized by a 16-bit A/D converter. The instrument supports Pulse Amplitude Modulation measurements and, at the same time, can capture fast OJIP transients or perform rapid measurements of QA– reoxidation kinetics, S-states, or of the effective antenna size. The major novel feature of this fluorometer is the capacity of the instrument to generate rectangular actinic flashes of extremely high power. Full reduction of QA acceptor can be achieved within 25 µs and the instrument can measure fluorescence induction during such a single-turnover saturating flash. This technique is used to determine the effective antenna size of the Photosystem II as well as its heterogeneity and connectivity without disturbing the measured system by DCMU or other herbicides. Photosynthetically active samples, either suspensions, leaves, or even corals, can be investigated for their photochemical yields, quenching parameters, state transitions, or for the kinetics of photosynthetic redox reactions.

SuperHead Standard Fluorometer


  • Algal Online Monitor is a portable and robust device for online detection and continuous monitoring of photosynthetic microorganisms in both natural and artificial water bodies. It detects variety of cyanobacteria, green and brown algae, diatoms, and other microbes. Its extremely high sensitivity (30 ng Chl/l) allows early detection of very low concentrations of these organisms.

Algal Online Monitor


  • OnlineFlow Fluorometer FFL-2012 is an autonomously operated measuring station intended for continuous in situ monitoring of active fluorescence emitted by photosynthetic freshwater and marine microorganisms. Implementation of Fast Repetition Rate Fluorometry (FRRF) permits determination of the functional absorption cross-section of Photosystem II (σPSII), energy transfer between Photosystem II units (p), F0, F’0 and FM, F’M in intervals of as little as few seconds. From these variables, real-time estimates of photosynthetic electron transport rates through photosystem II (Pe) can then be obtained. These measurements can then be used in environmental models for phytoplankton productivity assessment.

Built-in double color (450 nm and 590 nm) LED actinic light sources, individual light and dark acclimation chambers, stirrer and a solenoid control panel allow measurements of Rapid Light Curve (RLC), that expresses the irradiance dependency of the quantum yield of PSII (φPSII(E)), which can be further converted to Pe versus E curves.

OnlineFlow Fluorometer