PSI offers a wide range of handheld, battery-powered devices suitable for laboratory and field investigations as well as for teaching.

These pocket-sized devices are designed for measurement of different parameters by various modes:

  • Fluorescence:

The FluorPen series measures the chlorophyll fluorescence parameters of FT, QY (FV/FM), chlorophyll fluorescence fast-transient analysis (OJIP), NPQ (Non-Photochemical Quenching) and Light Curve.

The PAR-FluorPen provides all the parameters that the FluorPen provides, with the addition of the Photosynthetically Active Radiation (PAR).

FluorPen FP 100


The Monitoring Pen is a robust and weatherproof device, designed for long-term, unattended monitoring of chlorophyll fluorescence parameters (FT, QY, OJIP, NPQ, and Light Curve) under rough environmental conditions.

MP 100 in Antarctic Research

The AquaPens allow rapid measurements of fluorescence in suspensions and natural waters and excel in a high sensitivity of up to 0.5 µg Chl/l, with excitation at 455 nm (Blue) and
620 nm (red-orange). The emitted light is optically filtered and precisely focused to deliver light intensities of up to 3,000 µmol(photon)/m2/s. The AquaPen-C is equipped with a blue and red LED emitter and, to measure
fluorescence in suspensions in a cuvette, while the AquaPen-P is equipped with a single blue LED  emitter (optionally red or white), carrying out measurements by a  submersible optical probe.

AquaPen-C AP-C 100       AquaPen



The Algal Online Monitor is a portable and robust device for online detection and continuous flow-through monitoring of photosynthetic microorganisms, at ultra-high sensitivity, with a detection limit 30 ng Chl/l, with variable excitation colors.

The Handy FluorCam series consists of portable devices for chlorophyll and GFP fluorescence imaging.


  • Reflectance:

The PolyPen features a complete system for measurement of spectral reflectance of an internal light source (Xenon incandescent lamp 380 – 1050 nm) from leaves, as well as measurements of transmittance and absorbance of any external light source. In addition, PolyPen incorporates formulas of commonly used reflectance indices (e.g. NDVI, NDGI, PRI, Greenness Index, etc.) into its software. Measured data are instantly displayed in graphs or data sheets on the device screen display. They are also stored in the device memory for later re-collection or transfer onto a PC.

PolyPen RP 400

The N-Pen characterizes nitrogen amount by means of reflectance and by the concept of a close link between chlorophyll content and nitrogen content in plants. Rugged and compact N-Pen can be favorably used in the field, in the plant biology lab or for education. The use of the N-Pen is non-destructive and permits effective, quick, repeated measurements throughout the growing season.


The PlantPen PRI measures Photochemical Reflectance Index in two narrow wavelength bands centered close to 531 nm and 570 nm. PRI is sensitive to changes in carotenoid pigments that are indicative of photosynthetic light use efficiency, the rate of carbon dioxide uptake, or as a reliable water-stress index. As such, it is used in studies of vegetation productivity and stress. NDVI300 measures Normalized Difference Vegetation Index, which is an important indicator of chlorophyll content in plants. The device compares reflected light at two distinct wavelengths, 660 and 740 nm. The pigment in plant leaves – chlorophyll – strongly absorbs visible light (from 0.4 to 0.7 μm) for use in photosynthesis. The cell structure of leaves, on the other hand, strongly reflects near-infrared light (from 0.7 to 1.1 μm). The differences in plant reflectance in the visible and near-infrared wavelengths are used to calculate NDVI index. NDVI is directly related to the photosynthetic capacity and hence energy absorption of plant canopies.

PlantPen PRI 200 & NDVI 300

 The LaiPen measures Leaf Area Index (LAI) and Photosynthetically Active Radiation (PAR). It provides fast and easily repeatable measurements for the study of Canopy Productivity, Forest Dynamism, Remote Sensing and more.

LaiPen LP 100

  • Spectrophotometry:

The SpectraPen series measures spectral characteristics and calculates key parameters like Lux, Lumen, PAR and Watt values, allowing the rapid measurement of light intensity and spectral light quality in the lab, greenhouse or field.

SpectraPen LM 500