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Pairs well with
You can spend good money on a quality LED fixture and still get mediocre results if you're guessing at how much light is actually hitting your canopy. A dimmer percentage is not a PPFD reading — and PPFD is what plants respond to. The Treegers Quantum PAR Meter measures Photosynthetic Photon Flux Density across the 400–700nm range at every point you position the remote sensor, stores up to 99 readings, calculates Daily Light Integral, and gives you the actual numbers your lights are delivering. It's the missing piece between a good setup and a dialled-in one.
Tech Specs
What's in the Box
- Take readings at canopy height — not at the light, not halfway down. The PPFD at leaf surface is what matters for plant response.
- Map a grid across your canopy: at minimum take readings at the four corners and the centre. More points gives a more accurate uniformity picture.
- Use the AVG function to calculate your average PPFD across the canopy — this is the number to compare against target PPFD ranges for your crop stage.
- Use the DLI function to verify your daily light dose. For most flowering crops, target DLI is 35–50 mol/m2/day. Veg crops typically target 20–35 mol/m2/day.
- If you're using the Growcast's PPFD dimming feature, your canopy map data is the input — without a PAR meter, that feature has nothing to work from.
- The optional Extension Wand mounts to the sensor's 1/4" thread and is useful for reaching the centre of larger canopies without stepping over plants.
How to Use the Quantum PAR Meter
Pairs Well With
The Growcast's PPFD dimming feature needs canopy map data to work. The PAR Meter provides those numbers — they're made for each other.
Treegers GL420W LED FixtureUse the PAR Meter to verify that your GL420W is delivering the PPFD your canopy needs at the height you've set — stop guessing, start measuring.
Treegers GL650W+ LED FixtureAt higher wattages, canopy uniformity mapping becomes more important. The PAR Meter tells you exactly where the hot spots and shadows are.
Treegers PAR Meter Extension WandThe optional extension wand attaches to the sensor's 1/4" thread for reaching across larger canopies without stepping over plants or disturbing the room.
LED Grow LightsThe PAR Meter works with any grow light in the 400–700nm range — LED, HPS, CMH, or MH. Brand and fixture don't matter; photons are photons.
Environment ControllersPrecise light data pairs with environmental monitoring to give you a complete picture of what's happening at canopy level.
Frequently Asked Questions
What does a PAR meter actually measure?
A PAR meter measures Photosynthetic Photon Flux Density (PPFD) — the number of photosynthetically active photons (in the 400–700nm wavelength range) hitting a surface per second, expressed in μmol/m2/sec. PPFD is the standard metric for describing how much usable light is available to your plants at any given point in the canopy. It is different from lux, which measures brightness as perceived by the human eye, not by a plant.
What is DLI and why does it matter?
DLI (Daily Light Integral) is the total number of photons delivered to a square metre of canopy over a full day, expressed in mol/m2/day. It's the cumulative light dose your plants receive — not just the intensity at any single moment. DLI accounts for both how bright your lights are and how long they run, making it a more complete metric for managing plant growth than PPFD alone. Most flowering crops target 35–50 mol/m2/day; leafy greens and veg stages typically target 20–35 mol/m2/day.
Will this PAR meter work with my non-Treegers LED lights?
Yes — the Quantum PAR Meter measures PPFD from any light source within the 400–700nm PAR range. It works with LED, HPS, CMH, MH, and fluorescent grow lights regardless of brand. The sensor does not care what produced the photons — it counts them.
How accurate is the Treegers PAR Meter compared to more expensive models?
The Treegers meter has a repeatability of +/-1 μmol/m2/sec and a measurement range of 0–3999 μmol/m2/sec — specifications that are more than sufficient for the needs of most hobby, semi-commercial, and commercial indoor growers. Research-grade meters like the Apogee SQ-520 or LI-COR LI-190R offer higher absolute accuracy, but at five to ten times the price. For dialling in fixture height, verifying canopy uniformity, and using Growcast PPFD targeting, the Treegers meter delivers what you need.
What is the PAR Meter Extension Wand and do I need it?
The optional Treegers Extension Wand attaches to the sensor's standard 1/4" screw mount and extends your reach for canopy measurements without crouching or stepping over plants. It is particularly useful for mapping larger rooms (1.5m x 1.5m and beyond) where reaching the centre of the canopy without disturbing the room is otherwise awkward. For most single-tent grows up to 1.2m, the included cables provide enough flexibility and the wand is an optional upgrade rather than an essential.
Can I use a PAR meter to set my dimmer correctly?
Yes — this is one of the most practical uses of a PAR meter. Fixture dimmer percentages do not always correspond linearly to output — 50% on a dimmer knob does not mean 50% of maximum PPFD. Measuring actual PPFD at each dimmer setting for your specific fixture at your specific hang height gives you a real-world intensity map. If you're using the Treegers Growcast's PPFD targeting feature, measured canopy data is what drives it — without a PAR meter, that feature cannot be used to its full potential.
Stop Guessing. Start Measuring.
The Treegers Quantum PAR Meter gives you the actual PPFD numbers your canopy is working with. Pair it with any grow light, any tent, any setup. Questions about what readings you should be targeting for your crop? The Grow Guys team knows the numbers.