in situ FIRe Fluorescence Induction and Relaxation System

In Situ FIRe Fluorescence Induction and Relaxation System

The next generation submersible FIRe system capable of measuring variable fluorescence in photosynthetic organisms in situ.

The In Situ FIRe (Fluorescence Induction and Relaxation) system is the next generation submersible FIRe sensor capable of measuring the variable fluorescence of photosynthetic organisms in situ.

The FIRe technique is based on the research of Dr. Maxim Gorbunov and Dr. Paul Falkowski from Rutgers University and uses active stimulation and highly resolved detection of the induction and subsequent relaxation of chlorophyll fluorescence yields on micro- and millisecond time scales.

This approach provides:

  • Minimum and maximum fluorescence yields in the dark and under natural light (Fo, Fm, Fo', and Fm')
  • Maximum quantum efficiency of photochemistry in PSII in the dark (Fv/Fm) and effective quantum efficiency under natural light (Fv'/Fm')
  • Quantum yield of photochemistry in PSII (ΔF'/Fm', or σPSII)
  • Functional absorption cross-section of PSII (σPSII)
  • Rates of electron transport on the acceptor and donor sides of PSII (tQa and tPQ)

System Features

  • Wide dynamic range of fluorescence signals (four orders of magnitude)
  • Comprehensive suite of fluorescence and photosynthetic parameters
  • Internal logging with removable multimedia card
  • Optional flow cell for dark adaptation and pumped operations
  • Built-in pressure sensor
  • Optional PAR sensor available
  • FIReCom software for easy set-up, data viewing and post-processing

Typical Applications

  • Quantify environmental stress responses
  • Assess primary productivity in aquatic ecosystems
  • Ecophysiological studies


Excitation light source:blue LED (maximum emission 450 nm, 50 nm bandwidth)
Emission detection:678 nm, 22 nm bandwidth
Detector:Auto gain ranging
Pulse control:Programmable 1 μsec – 1000 msec
Data acquisition:14 bit, 1 MHz
Operating Platform:Intel PXA270 / Embedded Linux
Power Requirements:6 – 18 VDC or 19 – 72 VDC, 7 W
Operating Temperature:0°C to + 50°C
Dimensions (Length x Diameter):50.3 cm (19.8”) x 10.2 cm (4.0”)
Depth rating:200 m
Weight (in air):3.8 kg (8.5 lbs)
Housing materials:Acetal plastic and aluminum


FIReCom is an easy-to-use software application for configuring and controlling all aspects of In Situ FIRe, and for interactively setting up experiments, collecting data, and analyzing results.

FIReCom software features include:

  • User-friendly configuration for basic instrument operation
  • Graphic plots for processed and/or raw profile data in real time or via file playback
  • Data management capabilities over USB and/or serial interface
  • Flexible setup options for multiple measurement protocols simultaneously
  • Utility for reprocessing previously logged FIRe data files. Experiment with different processing parameters to re-calculate processed values
  • Tool to convert raw or processed data to calibrated comma separated values suitable for import to spreadsheets and database
  • Please refer to the User Manual for more information.

Download FIReCom 1.1.4

Released March 25, 2014

FIReCom 1.1, is a major release with new features and fixes for known defects. New features includes an auto-detecting firmware upgrade procedure, addition of fitted profile and time stamp to the profile sequence graph, pressure sensor calibration, addition of sequence file to the summary report, ability to replay post-processed data files, improvements to the graph zooming/panning controls, improved data processing fitting algorithms and support for Windows 8.

FIReCom 1.1 requires that firmware FIReOS 2.0.8 or later be installed on your In Situ FIRe. Please contact customer support for firmware upgrade assistance.

FIReCom-1.1.4-b273-x86.exe for Microsoft Windows
Product Data Sheet

In Situ FIRe Datasheet

Tuesday, November 18, 2014
Product Manual

In Situ FIRe 1.1.4 Manual

Tuesday, March 25, 2014

What do I do if the STF induction curve does not reach a plateau?

If the fluorescence yield does not reach its maximum value (i.e., plateau) by the end of the single turnover flash (STF), increase the STF duration. For example, if you are currently using an STF duration of 80-100 micro-seconds, try increasing it to 120 or 150 micro-seconds.

What is the difference between parameters calculated from the STF and MTF functions?

The in situ FIRe system uses both STF and MTF protocols. STF protocols measure changes in chlorophyll fluorescence that occur during a short (100 - 400 us) but intense (>40,000 umol photons m-2s-1) flash of light whereas the MTF approach measures the fluorescence induced by a weaker modulated pulsed source with an intensity of ~ 3,000 to 10,000 umol photons m-2s-1 to modify fluorescence yields.

The STF approach also fundamentally differs from the MTF approach in that the STF fully reduces the primary electron acceptor, QA, allowing a simultaneous single closure event of all photosystem II (PSII) reaction centers whereas the MTF technique generates multiple photochemical charge separations that fully reduces QA, the secondary acceptor, QB, and plastoquinone (PQ).

So, the STF and MTF Fv/Fm data are different and will show different values, because the techniques used to measure them are different. Most scientists now accept that the STF Fv/Fm values are the most appropriate for use in productivity models. Further more, given that the STF protocol is much shorter than the MTF protocol it is more appropriate for moving waters, which is important in the context of an in-situ system where the water is constantly being flushed through the sample volume.

How does the FIRe System differ from Pulse Amplitude Modulated (PAM) fluorometer?

The FIRe System measures changes in chlorophyll fluorescence that occur during a short (100 - 400 μs) but intense (> 20,000 μmol photons m-2 s-1) flash of light whereas the PAM approach measures the fluorescence induced by a weak modulated light source while using ‘saturating’ pulses of ~3000 - 10,000 μmol photons m-2 s-1 to modify fluorescence yields.

The FIRe System also fundamentally differs from a PAM in that the FIRe fully reduces the primary electron acceptor, QA, allowing a simultaneous single closure (STF) event of all photosystem II (PSII) reaction centers whereas the PAM technique generates multiple photochemical charge separations (MTF) that fully reduces QA, the secondary acceptor, QB, and plastoquinone (PQ). By lengthening the measuring protocol the FIRe can also yield MTF data.

For a complete discussion on the mechanistic and practical differences between the two techniques see: Suggett, D.J., K. Oxborough, N.R. Baker, H.L. MacIntyre, T.M. Kana, & R.J. Geider. 2003. Fast repetition rate and pulse amplitude modulation chlorophyll a fluorescence measurements for assessment of photosynthesis electron transport in marine phytoplankton. European Journal of Phycology. 38: 371-84.

Flow Cell/Dark Adaptation Chamber

The removable flow cell accessory can be pressed into the optical head in order to seal and isolate the sample volume from the surrounding environment. With the flow cell in place, water samples can be pumped through the the resulting sample chamber at controlled rates.







PAR Sensor (Optional)

In Situ FIRe has bulkhead electrical connections for a Satlantic Photosynthetically Available Radiation (PAR) Sensor. FIRe is pre-configured to accept an analog input from a logarithmic PAR sensor.




Profiling Hardware (Deck Unit and Cabling) (Optional)

The MDU-300 deck unit serves as both a nominal 48 Volt DC power source for the in-situ FIRe system and as an RS-422 to RS-232 level converter. The MDU-300 provides three connectors for data and power.