The Standard in

Plant Stress Measurement


FV/FM Meter

The most affordable modulated fluorometer for use with dark clips!


FV/FM meter allows reliable measurements of FV/FM, FO, and FM

FV/FM is considered the gold standard of chlorophyll fluorescence measurement because it allows sample comparison at the same known common dark adaption state and measurements generally correlate to photosynthesis measurement. While healthy values vary by species between 0.79 to 0.84, lower FV/FM values indicate plant stress is affecting Photosystem II.

For specific results on different types of plant stress measurement, ask for a copy of our Plant Stress Guide.


  • Inexpensive dark adaption clips to allow rapid measurement of more statistically significant plant populations.
  • Dark clips allow the equivalent of "predawn dark adaption measurement" at more reasonable hours of the day. They also allow dark adaption for shorter periods during the day.
  • It comes standard with 10 dark clips (optional packages of 50 dark clips are available).
  • Graphically displays FV/FM trace.
  • 2 GB of memory allow storage of tens of thousands of measurements.
  • USB transfer of comma delineated files to Excel or other analysis tools.
  • Using an optical probe instead of fiber optics allows Opti-Sciences to significantly reduce the cost of the instrument without sacrificing quality.
  • The FV/FM meter is most affordable modulated fluorometer for use with dark clips. FV/FM is the most used chlorophyll fluorescence measuring protocol in the world because it allows comparison of samples in the same known dark-adapted state. This allows comparison of samples where the light is changing. Samples can be compared under canopy or in situations where steady state photosynthesis is hard to measure. The FV/FM meter has an optical probe that permits measurement with dark adaptation clips, allowing fast measurement of large plant populations.

  • Fast measurements:

    FV/FM , FV/FO, FO, & FM.

    Light source:

    Array of red LEDs at 660 nm.

    Lighting conditions:

    Dark adapted conditions only.

    Light sources:

    Red LED Saturation flash array up to 6,000 μmoles.

    Red modulated light source (660nm with a 690nm cut off filter).


    Pin Photodiode with a 700nm to 750nm band pass filter.

    Dark adaptation clips:

    10 dark adaption clips are included.


    Lithium-ion USB battery pack with 8 hour life. Designed to be carried in a pocket. The unit may be used with any USB compatible battery. The instrument will also run on most mains current USB chargers.


    8.5" x 1.125" x 1.625" (22 x 3 x 4 cm)

    USB cable 32" long,  (81 cm)

    Battery 4.5" x 1" x 1" (12 x 2.54 x 2.54 cm)

    Weight with battery 0.8 lbs (0.36 kg)


    2 Gigabytes


    Standard USB storage device. Comma delineated files. Files may be opened in Excel or other programs with spread sheet formats.

    Graphic screen display:

    132 X by 30 pixel LCD.

  • FL-DC

    Dark adaptation clip


    Adjustable locking desktop arm


    Pouch of 50 clips

  • PDF document.

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Opti-Sciences, Inc.     8 Winn Avenue      Hudson NH 03051       USA      (603)883-4400

Opti-Sciences, Inc.

8 Winn Ave

Hudson, NH 03051, USA

Phone: (603) 883-4400

Fax: (603) 883-4410