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Description The LI-190SA is used by plant scientists, meteorolgists, horticulturists, ecological survey groups and other environmental scientists to measure PPFD in the atmosphere, growth chambers and greenhouses. Accurate measurements are obtained under natural and artificial light conditions because of the computer-tailored spectral response of the LI-190SA. |
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Principle of Measurement and Specifications During photosynthesis, plants use energy in the region of the electromagnetic spectrum from 400-700 nm (1,2). The radiation in this range, referred to as Photosynthetically Active Radiation (PAR), can be measured in energy units (watts m-2) or as photosynthetic Photon Flux Density (PPFD), which has units of quanta (photons) per unit time per unit surface area. The units most commonly used are micro-moles of quanta per second per square meter (umol s-1 m-2). Accurate measurements are obtained under all natural and artificial lighting conditions because of the computer tailored spectral response of the LI-190SA. Coloured glass filters are used to tailor the silicon photodiode response to the desired quantum response. An interface filter provides a sharp cutoff at 700 nm, which is critical for measurements under vegetation where the ratio of infrared to visible light may be high. A small response in the infrared region can cause an appreciable measurement error. Absolute Calibration:
± 5% traceable to the U.S. NIST
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