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PAR & DLI Light Measurement

Measure the plant-usable light reaching your crop with the SpotOn® Quantum PAR Light Meter. Take instant readings under sunlight or artificial light (including LEDs!) compare light across a growing area, or use DLI mode to see accumulated daily light on the meter. Add the SpotOn® Extension Wand to reach further into the canopy.
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Measure PAR Under Different Light Sources

Check PAR in full sun, shade, or under artificial lighting, including LED, high-pressure sodium, metal halide, fluorescent, and halogen.
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Compare Light Across a Growing Area

Use Scan mode to quickly average PAR over an area and compare readings across benches, shelves, or canopy positions.
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See Daily Light Integral on the Meter

DLI mode displays accumulated daily light on the LCD. The meter calculates it continuously from light readings taken every three minutes, no computer required.
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Reach Further Into Plant Canopies

Pair the meter with the 36-inch Extension Wand to take readings deeper in the canopy or at different plant heights.
View the Quantum PAR Light Meter

SMARTER LIGHT MEASUREMENTS. MORE INFORMED GROWING DECISIONS.

Light can vary across a greenhouse, between growing shelves, and at different heights in a plant canopy. Measuring where plants receive light gives growers a clearer view of those differences and helps them assess natural and supplemental lighting conditions.
PAR & DLI light measurement with the SpotOn Quantum PAR Light Meter under LED lights.

Check Light at the Growing Level

A reading at plant level can help you compare light exposure across benches, shelves, and canopy positions. Use instant spot readings to check specific locations, or use Scan mode to average PAR over an area when you want a broader comparison.

Understand Daily Light Exposure

A PAR reading shows light intensity at a moment in time. Daily Light Integral (DLI) describes the total photosynthetic light received over a day. The Quantum PAR Light Meter calculates DLI continuously from readings taken every three minutes and displays the result on its LCD.

Position the sensor where you want to understand light exposure, then use the displayed DLI as a reference alongside crop-specific growing guidance.

For more details, check out Virginia Tech Extension’s guide to calculating and using DLI.

dli light measurement spoton quantum par light meter
par dli light measurement reading bonsai tree growing

Take Readings Deeper in the Canopy

For measurements that are harder to reach by hand, add the SpotOn® Extension Wand. The rugged, three-piece steel wand extends 36 inches and disassembles for storage and travel. Threaded connections help keep the meter from twisting when extended, while the rubber handle grip helps provide a secure hold—even with wet hands.

The Extension Wand is sold separately.

DESIGNED FOR GREENHOUSES, INDOOR GROWING & PLANT RESEARCH

The SpotOn Quantum PAR Light Meter is a handheld tool for growers and researchers who need to check plant-level light under natural sunlight or artificial sources. Its compact design, Spot and Scan measurement modes, and on-screen DLI display support light checks in greenhouses, indoor farms, propagation areas, and research settings. The meter is rated IP65 for use in rain, irrigation, and condensing environments. It is water resistant, but should not be submerged.
SpotOn®

Quantum PAR Light Meter

$299.00 US List Price

The SpotOn Quantum PAR Light Meter: Frequently Asked Questions

Yes. The SpotOn Quantum PAR Light Meter is designed to provide PAR readings under any light source, including LED, high-pressure sodium, metal halide, fluorescent, and halogen lighting.

Daily Light Integral (DLI) is the total photosynthetic light received over a day. It is expressed in moles per square meter per day (mol m⁻² day⁻¹).

PAR stands for photosynthetically active radiation: light in the 400–700 nm range used in photosynthesis. A PAR meter measures the light reaching a surface, with readings shown in µmol m⁻² s⁻¹.

Yes. Scan mode quickly averages PAR over an area, making it useful for comparing light across growing positions.

Yes. DLI mode displays the calculated daily total on the meter’s LCD. The meter calculates it continuously from light readings taken every three minutes.

The SpotOn Extension Wand is a separate accessory. It is a 36-inch, three-piece steel wand designed to help position the meter deeper in plant canopies.

The meter can measure light from full sun to full shade indoors or outdoors. It is IP65 rated for rain, irrigation, and condensing environments, but should not be submerged.

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