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SpotOn Quantum Photosynthetic Active Radiation (35650) Light Meter

Model #: 35650

Condition: New

Regular Price: $349.95 $335.00

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SpotOn Quantum Photosynthetic Active Radiation (35650) Light Meter by Innoquest

This meter is designed for measuring PAR light indoors and outdoors regardless of light source type. It works well for greenhouse, field, and R&D applications requiring reliable plant growth light readings. The chemical reaction of photosynthesis requires light.


Unlike energy based light measurements, the quantum (quantity) of photons is measured since it can be directly tied to the number of these chemical reactions that can take place. The measure of all available light between the wavelength (color) range of 400 to 700 nanometers(nm) has been accepted as the best measure of light available for photosynthesis. This is defined as quantum Photosynthetic Active Radiation (PAR) in units of µmol m-2 s-1. This is referred to as PAR light, PPFD, PPF, and Quantum light interchangeably and is the total quantity of photons in µmoles over the light spectrum from 400 to 700 nm hitting a one-meter square area every second. One micromole is equal to 602,214,085,700,000,000 photons of light! This is not the same as foot candle or lux measurements


Affordable, compact and easy-to-use, this meter provides scientifically accurate Photosynthetic Active Radiation (PAR) light readings under any light source including LED! Three modes of operation include Instant Spot Measurement mode for PAR light readings; Scan mode for quickly averaging PAR over an area; and DLI mode that shows Daily Light Integral on the LCD (no computer needed). Water- and impact-resistant. Integral mounting plate allows the meter to stand, stake or hang with a lanyard.

  • Provides accurate PAR light readings from ANY light source:
    - Full sun to full shade indoors or outdoors.
    - Artificial light sources (LED, High Pressure Sodium, Metal Halide, Florescent, Halogen etc).
  • Three modes of operation:
    - Instant Spot Measurement mode for PAR light readings.
    - Scan mode for quickly averaging PAR over an area.
    - DLI mode shows Daily Light Integral on the LCD (no computer needed).
  • Compact and easy to use.
  • Integral mounting plate for: stand, stake, lanyard & hanger hole, and magnet mounts.
  • Small size allows light readings in tight spaces without needing an external sensor.
  • ¼-20 threaded hole for mounting on camera tripods & stands.
  • Water and impact resistant.


0.0 to 6,500 μmol m-2 s-1

DLI (Daily Light Integral):
0.0 to 560.0 moles m-2 day-1

Display Resolution: PAR Light:
0.1 μmol m-2 s-1 from 0.0 to 99.9
1 μmol m-2 s-1 from 100 to 6,500

0.1 moles m-2 day-1

Accuracy: +/- 5% (each meter is calibrated to a NIST traceable light sensor on a broad-spectrum light source)
Azimuth Error: +/- 1% over 360°
Daily Light Integral (DLI): Calculated continuously from light readings every 3 minutes
Water Resistant: IP-65 rated for use in rain, irrigation, and condensing environments (do not submerge)
Operating Environment: 32-130°F(0-55°C) with 0-100% RH condensing ok
Battery: CR2032 3v coin cell lithium included (2-year battery life)
Size & Weight: 1.75" (4.5cm)W  x 5.75" (14.6cm)L x .85" (1.8cm)D.
2.8 ounces (77grams).

Supplied with:

  • Sensor cover.
  • Soft carrying case.

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