The Phantom PHOTOBIO Advanced PAR Meter provides accurate and cost-effective measurement for any light source used in horticultural applications. The Advanced Quantum PAR meter is designed to measure PAR (Photosynthetically Active Radiation) flux in wavelengths ranging 400 to 700nm. There is a positive proportional relationship between the number of photons absorbed in the 400 to 700nm band and the rate of photosynthesis, important for maximizing crop yield.