Quantum PAR meter for measuring plant light

Regular price 26,400.00 RSD
Regular price Sale price 26,400.00 RSD
8,800.00 RSD × 3 with no fees

This PAR quantum meter counts the photons your plants actually use for photosynthesis, between 400 and 700 nm, and displays the flux density in µmol/m²/s. Its remote sensor is placed at foliage height under an LED lamp, a hydroponic tower light bar or the roof of a greenhouse, and the unit stores 99 readings.

Ref. TK-PAR-PHOTOBIO·Mesure de la lumière
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The summary

  • In the case: a reading unit, a remote sensor, two cables and two AAA batteries.
  • What it measures: photon flux density between 400 and 700 nm, from 0 to 3,999 µmol/m²/s.
  • Why not a lux meter: lux follows the sensitivity of the human eye, not that of the leaf.
  • The benchmarks: a target intensity for each stage, then the daily light dose to calculate.
  • The memory: 99 readings stored to map a shelf or a greenhouse.
  • What is sent to you: a 0.5 kg parcel, the instrument in its case.

Measures photosynthetic radiation under a horticultural lamp or in a greenhouse

The PhotoBio PAR quantum meter measures PPFD, the photons useful to plants between 400 and 700 nm, from 0 to 3,999 µmol/m²/s, with a remote sensor and 99 readings in memory. It is used to set lamp height indoors or to judge the light in an aquaponic greenhouse, with the unit kept away from splashes from the tank.

A horticultural lamp is chosen on its electrical power, but the plant does not read watts. It captures photons, and only those with a wavelength between 400 and 700 nm drive photosynthesis: this is what is known as photosynthetically active radiation, or PAR. This quantum meter counts precisely those photons and gives you their flux density, the PPFD, in micromoles per square metre per second. You can therefore see how much light each plant on your shelf, in your tower or in your greenhouse really receives.

🔬 A remote quantum sensor

The device consists of two parts joined by a cable with an RJ11 plug: a reading unit with an LCD screen and a remote sensor to be placed under the light source. Two cables are supplied, a coiled cord of about 1.5 m for close-range measurements and a straight cable of 3.65 m that lets you read the screen outside the lit area, without casting your shadow on the sensor. The measurement range runs from 0 to 3,999 µmol/m²/s, which covers a seedling rack and full summer sun alike, and the resolution reaches 0.1 µmol/m²/s up to 999.

The device runs on 2 AAA batteries, supplied, and needs no initial setup. CALI mode resets the zero: cover the photosensitive part of the sensor completely, then hold the ENTER key for 3 seconds. RCFS mode restores the factory settings but also erases all saved readings, so note them down beforehand. Keep the sensor clean and dry, store the whole kit in its case after use, and use the device between 0 and 50 °C, without condensation.

A lux meter, unlike a quantum sensor, weights light according to the sensitivity of the human eye, which peaks in the green. Under an LED lamp rich in blue and red, it therefore underestimates the useful light, while it flatters a very green white source. The quantum meter counts photons without favouring any colour, which makes two lamps with different spectra comparable. It is also the quantity that appears on horticultural lighting data sheets, so you can check it on your own installation, at the height where you have hung the lamp.

📐 Mapping the lighting on a shelf

A lamp never lights evenly: the PPFD is highest under its centre and drops towards the edges, sometimes by half on a single shelf. Place the sensor at foliage height, with its flat face turned towards the lamp, and take readings at several points on a regular grid, for example every 20 cm. The LOG button records each measurement, up to 99 readings that you can then scroll through on the screen. These figures tell you whether you need to lower the lamp, add another one at the sides, or keep the edges for the least demanding plants, such as lettuces and herbs. On a hydroponic grow tower, the same method is applied level by level, because the bottom of the column often receives far less than the top.

Seedlings and cuttings

Young plants are happy with moderate intensity, and a lamp that is too close will scorch them faster than it makes them grow.

Salad leaves and herbs

These leaves grow well under medium intensity, and the sensor shows the lamp height that is sufficient.

Tomatoes and peppers

Fruiting vegetables need considerably more light, which the measurement helps you reach without wasting electricity.

Greenhouse in winter

A midday reading under the glazing shows the difference from summer and decides whether supplementary lighting is needed.

Measure before buying a second lamp

Before adding an LED bar to your setup, measure the PPFD at the four corners and in the centre of the growing area. If only the edges lack light, a simple adjustable hanging system that moves the lamp closer or re-centres it often corrects the gap. You then pay for the electricity of a second lamp only where the measurement genuinely calls for it.

Protect your eyes under a powerful lamp

A horticultural lamp may emit ultraviolet, intense blue and infrared radiation that is harmful to the eyes and skin. While taking readings, wear suitable glasses, avoid staring at the light source and do not stay for long under a high-powered lamp. The 3.65 m cable is there precisely so that you can read the display from a distance.

🌱 Light in aquaponics

In an indoor aquaponic system, lighting is often the biggest item of electricity consumption, ahead of the pump and the aeration. Measuring PPFD lets you set the duration and height of the lamps as precisely as possible, then multiply the intensity by the lighting time to obtain the daily dose of light, the DLI. In a greenhouse, measurement makes the most sense from November to February: natural light drops sharply, and the plants of a coupled system then slow their uptake of nitrates. A reading at midday under the glazing tells you whether supplementary lighting is worthwhile, and the guide to getting started with indoor hydroponics covers the choice of lamps in detail.

🔆 PAR, PPFD and DLI

Three acronyms keep appearing on lighting data sheets, and they do not mean the same thing. PAR names the band of useful light, from 400 to 700 nm. PPFD counts, at a given instant, the photons in this band striking one square metre each second: it is the figure shown on the display, in µmol/m²/s, and it changes as soon as you raise or lower the lamp. DLI, finally, accumulates these photons over the whole day and is expressed in moles per square metre per day. To convert from one to the other, multiply the average PPFD by the lighting duration in hours, then by 0.0036: 250 µmol/m²/s for 14 hours therefore gives around 12.6 mol/m²/day.

Technical specifications

The measurement

Measured quantity
PPFD, in µmol/m²/sPhotosynthetic photon flux density
Spectral band
400 to 700 nmLimits to within 10 nm
Range
0 to 3,999 µmol/m²/sFrom seedling under LEDs to full summer sun
Resolution
0.1 up to 999, then 1
Repeatability
1 µmol/m²/s
Memory
99 readingsLOG button, readings viewable on screen

The device

Sensor
Remote, RJ11 socket
Cables
Coiled 1.5 m and straight 3.65 mThe long cable lets you read the screen out of the light
Feeding
2 AAA batteries includedMore than 150 hours of operation
Casing dimensions
11.5 x 6 x 2.4 cm
Conditions of use
0 to 50 °C, non-condensingHumidity from 0 to 95%
Barcode
UPC 638104027069

4 further specifications are available in the detailed view.

In the box

  • 1 reader unit with LCD screen
  • 1 remote quantum sensor
  • 1 coiled cable and 1 straight 3.65 m cable
  • 2 AAA batteries
  • 1 carry case
  • 1 instruction leaflet

Manufacturer's values (instructions and technical data sheet for the LGBQM2 model). The benchmarks per crop are common horticultural values.

Manufacturer and product safety

Manufacturer
Hydrofarm (PhotoBio by Phantom)

Information provided under Regulation (EU) 2023/988 on general product safety.

Estimate your
delivery time

The quantum meter is shipped in its carry case, as a small 0.5 kg parcel, from a distributor's warehouse in France. The exact shipping cost is shown in your basket.

Frequently asked questions

12 questions

6 key questions, 12 in the detailed view

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