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Enabling better global research outcomes in soil, plant & environmental monitoring.


The PAM-2500 chlorophyll fluorometers are successors of the well-known PAM-2000/2100 instruments which were introduced in the 1990s as the first portable PAM fluorometers. Since then they have been successfully applied worldwide by numerous scientists.

In the development of the PAM-2500, particular care was taken to maintain all properties appreciated by PAM-2000/2100 users and, at the same time, integrate state-of-the-art technology. Essentially, the hardware and optical system are thoroughly modernised. Also, while carrying through basic elements of the graphical user interface, instrument operation is based on the newly-developed PamWin-3 software, designed for operation on Windows PCs and Tablets.

Major Updates in the PAM-2500

  • Saturation pulse as well as polyphasic rise analysis with time resolution down to 10 µs
  • Latest generation light-emitting diodes for all internal light sources
  • High sensitivity enabling high quality measurements with dilute suspensions of algae and cyanobacteria

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.

Measuring Principle & Quenching Analysis

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).

Fluorometer / General Design

Signal detection: PIN-photodiode protected by long-pass filter (T(50%)=715 nm). Selective window amplifier
Sockets: Connector for Special Fibre-optics 2010-F. USB socket. Sockets for Leaf Clip Holder 2030-B or Micro Quantum/Temperature-Sensor 2060-M, Battery Charger MINI-PAM/L or external 12 V battery via MINIPAM/AK cable, and external lamp/trigger output
Communication: USB, Bluetooth Version 2.0 + EDR Class 2
User interface: Windows computer with PamWin-3 software
Power consumption: Basic operation 1.6 W. 8 W with all internal light sources operated at maximum output (measuring light, red and blue actinic light, and far red light).
Saturation pulse at maximum intensity: 30 W
Power supply: Rechargeable sealed lead-acid battery 12 V/2 Ah; Battery Charger MINI-PAM/L (100 to 240 V AC)
Recharging time: 6 hours (with the PAM-2500 turned off) via Battery Charger MINI-PAM/L
Operating temperature: -5 to +40°C
Operating humidity range: 20 to 95% RH to avoid condensation
Dimensions: 23 cm x 10.5 cm x 10.5 cm (L x W x H) aluminium housing
Weight: 2.5 kg (including battery)

Fluorometer / Light Output

Measuring light: Red LEDs, maximum emission at 630 nm, FWHM (full width at half maximum), 20 nm. 1 μs pulses at modulation frequencies 10 to 5000 Hz for Fo determinations (200 Hz default), and 1 to 100 kHz during actinic illumination, fast kinetics with 100 or 200 kHz, 20 intensity levels, frequency dependent effective PAR ranging from 0.001 to 100 μmol m-2 s-1
Blue actinic light: LEDs, maximum emission at 455 nm, FWHM 20 nm, PAR up to 800 μmol m-2 s-1, 20 intensity levels
Red actinic light: LEDs, maximum emission at 630 nm, FWHM 15 nm, PAR up to 4000 μmol m-2 s-1, 20 intensity levels
Saturation pulses: Red LEDs (see red actinic light), PAR up to 25000 μmol m-2 s-1, adjustable between 0.1 and 0.8 s, 20 intensity levels
Multiple turn-over flashes: Red LEDs (see red actinic light), PAR up to 25000 μmol m-2 s-1, adjustable between 1 and 800 ms, 20 intensity levels
Single turn-over flashes: Red LEDs (see red actinic light), PAR up to 125000 μmol m-2 s-1, adjustable between 5 and 50 μs
Far-red light: LED, maximum emission at 750 nm, FWHM 25 nm, 20 intensity levels

Special Fibre-optics 2010-F

Design: Flexible, steel-spiral, plastic-covered bundle with three-pin optical connector
Joint end (measuring site): Active diameter 6 mm, outer diameter 8 mm
Length: 100 cm
Weight: 300 g

Distance Clip 60° 2010-A

Design: Metal clip with fibre holder and 11 mm sample hole: 5.5 cm x 1.4 cm (L x W)
Fiber holder: 1.2 cm length, mounted 0.7 cm above base, with lateral screw to fix fibre optics. Angle between fibre optics axis and sample plane: 60°. Two spacer rings to vary the distance between fibre end and leaf surface

Battery Charger MINI-PAM/L

Input: 90 to 264 V AC, 47 to 63 Hz
Output: 19 V DC, 3.7 A
Operating temperature: 0 to 40°C
Dimensions: 15 cm x 6 cm x 3 cm (L x W x H)
Weight: 300 g

External Voltage Supply Cable MINI-PAM/AK

Design: 90 cm cable with fuse for over-current protection. The cable bypasses the internal battery of the PAM-2500 fluorometer and supplies voltage from an external 12 V battery directly to the electronics.

Carrier Bag

Carrier: Robust field carrier bag with shoulder and hip belt

Transport Box 2040-T

Design: Aluminium box with custom foam packing for PAM-2500 and accessories
Dimensions: 60 cm x 40 cm x 25 cm (L x W x H)
Weight: 5 kg

System Control and Data Acquisition

Software: PamWin-3 System Control and Data Acquisition Program

Fluorescence parameters:

Measured: Ft, Fo, Fm, F, Fo’ (also calculated), Fm’. Fast polyphasic rise and decay kinetics (time resolution up to 10 µs). PAR and °C, using the “Leaf-Clip Holder 2030-B” or the “Micro Quantum/Temp.-Sensor 2060-M”)
Calculated: Fo’ (also measured), Fv/Fm and Y(II) (maximum and effective photochemical yield of PS II, respectively), qL, qP, qN, NPQ, Y(NPQ), Y(NO) and ETR (electron transport rate), C/Fo (constant fraction of Fo that is assumed to originate from PS I)
Computer Requirements Processor: 0.8 GHz. RAM: 512 MB. Hard disc space: 50 MB. Screen resolution: 1024 x 600 pixels. USB 1.1, 2.0 or 3.0. Optional interface: Bluetooth Version 2.0 + EDR, Widcomm Stack. Operating system: Microsoft Windows XP/Vista/7/8/10