The light visible to the human eye in the spectral range from 380-780 nm is also actively used by plants. This part of the electromagnetic radiation, which powers photosynthesis called PAR (Photosynthetic Active Radiation) is usually found in wavelengths from 400 to 700nm. German Industry Standard DIN Norm 5031- 10:2000 describes the curve which is a mathematical formula that defines the average plant “sensitivity” to certain wavelengths. This forumla is leveraged in our spectral PAR instrument firmware and software which automatically outputs PAR values using radiometric values from our spectroradiometer systems as a basis for our calculation.
There are many different PAR meters OHSP350P and other radiometers available on market but the majority of them were designed and preconfigured for continuum day light spectra. For horticulture LED lighting, only properly calibrated and high quality instruments can provide dependable data for professional users.
Who are spectral PAR meters For?
What Can You Measure?Photosynthetic Active Radiation (PAR) and Photosynthetic Photon Flux Density (PPFD)
For plant growers, biologists and scientists the most important data in the light requirements for plants is PPFD measurement (photosynthetic photon flux density). PPFD is a measure of the amount of light that actually reaches a plant. It can be described as the number of photosynthetically active photons that fall on a given surface each second. The measurement of light which stimulates plant growth includes the PAR spectra and is expressed in PPFD values in μmol/m2/s and PPF in μmol/s. Similar to human vision metrics where we are evaluating lux and CRI which is the amount of light and the quality of light for visibility, for plants we are using PAR and PPFD to evaluate the amount and quality of active radiation.
Photosynthetic Photon Flux PPF (PPF)For manufacturers of growing lights, PPF measurement is also an important metric. This evaluates the total amount of energy that is produced by a light source per second. It is similar to radiant power measurement and it can be made with an integrating sphere connected to spectroradiometer when the system is properly calibrated and the photosynthetic photon flux calculation is supported by the software. OHSP350 offers a complete range of different sizes of integrating spheres from 48mm 500mm, 1m up to 2m integrating spheres which are ready for PPF measurement.
For laboratory applications, we recommend the Spectis 5.0 Touch PAR/PPFD meter which offers higher resolution detector and extended spectral range. All our spectrometers can also operate with a waterproof accessory OHSP350 illuminance, which can work under water and measure the euphotic zone. The right equipment for the PPF measurements is Sphere – available in diameter from 48 mm up to 2 m. To be able to analyze, compare and report all the data it is highly recommended to use Spectrosoft – laboratory grade software compatible with the OHSP spectrometer.