Light Meters & PAR Meters

A PAR meter shows how much usable light reaches your canopy. Set fixture height, dimming and daily light integral by measurement, not guesswork. Pick a handheld quantum meter for spot checks, or a TrolMaster or Iluminar sensor to log light around the clock.

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Light Meters & PAR Meters

PAR Meter and PPFD Sensors for Grow Lights

A PAR meter reads the light plants use for photosynthesis, so you can set fixture height and dimming by numbers instead of by eye. This collection holds two handheld quantum meters, the Apogee MQ-500 and the PHOTOBIO Advanced Quantum. Controller sensors from TrolMaster and Iluminar log light alongside temperature, humidity and CO2....

PAR meter infographic: handheld quantum meters, controller and wireless light sensors, PPFD units and how to calculate DLI

Use the readings to dial in our LED grow lights, or pair a sensor with the controllers in timers and controllers. Both sit in the wider grow lights range.

Types of Light Meters and Sensors

Handheld Quantum Meters

The full-spectrum Apogee MQ-500 reads 0 to 4,000 µmol/m²/s within ±5%, with drift under 2% per year. It logs readings and daily light integral for a full day. The PHOTOBIO Advanced Quantum puts its sensor on a 12 ft coiled cable and stores 99 readings. Pick a handheld to map a tent or test a new fixture.

Controller Light Sensors

The TrolMaster MBS-PAR reads 389 to 692 nm and lets Hydro-X dim lights to a set PPFD. The MBS-TH adds light to temperature and humidity for Hydro-X on a 16 ft cable. The MBS-Pro and MBS-GH add CO2 for Hydro-X Pro and Green-X. Choose these when lights already run on a TrolMaster.

Wireless Environment Sensors

The Iluminar HASH module reads PAR, temperature, humidity, CO2 and VPD, and sends them to its controller over RF. Up to 6 modules link to one controller, so larger rooms get readings from several spots.

How Growers Use Light Meters

Take PPFD readings at canopy height across the whole footprint, not just under the center. Raise, lower or dim the fixture until the edges and middle match your target. To get daily light integral, multiply PPFD by hours of light, then by 0.0036.

Frequently Asked Questions

What is a PAR meter?

It is a quantum sensor that counts photons from 400 to 700 nm, the range plants use for photosynthesis. The reading is PPFD, shown in µmol/m²/s. The Apogee MQ-500 and PHOTOBIO Advanced Quantum both read PPFD, and the MQ-500 also logs daily light integral.

PAR meter vs lux meter: which do I need?

For grow lights, measure PPFD. A lux meter weights light to the human eye, which peaks in green. PHOTOBIO notes that lux readings undercount the deep red and blue many LED fixtures put out. Lux works for room lighting, but PPFD tells you what reaches the canopy.

How do I measure PPFD?

Hold the sensor level at the top of the canopy with the lights at full run, then take readings in a grid. The PHOTOBIO meter stores 99 readings to compare later. A fixed sensor like the TrolMaster MBS-PAR reads one spot all day and dims lights to hold a target.