The LI-190R measures Photosynthetically Active Radiation (PAR, in µmol of photons m-2 s-1). It provides accurate measurements—in the open, in greenhouses, under plant canopies, or in growth chambers—for most broad-spectrum light sources, including natural sunlight, artificial, or mixed sources.
Plants use light in the wavelength range from about 400 to 700 nm to drive photosynthesis. The efficiency with which plants use light varies somewhat across this range, but McCree1 showed that measuring PAR provided a consistent way to predict plant photosynthetic response regardless of the spectrum of the light source.2Request a Quote
Expand your light measurement capabilities with data logging, long-term measurements, and automated calculation of daily light integral.Get a Quote
The LI‑190R uses a high-quality silicon photodiode and glass optical filter to create uniform sensitivity to light between 400 nm to 700 nm, which closely corresponds to light used by most plants. A newly designed optical filter tailors the spectral response to an unprecedented performance standard. Furthermore, the new filter is unaffected by environmental factors such as heat or humidity. The filter blocks light with wavelengths beyond 700 nm, which is critical for measurements under vegetation where the ratio of infrared to visible light may be high.
The sensor features excellent cosine response, which ensures accurate measurements under diffuse light and when sunlight originates from a low solar angle. This, in combination with high resolution at low light levels, makes the LI-190R useful for determining the light compensation point in plants.
Learn more about the science and engineering behind the new design
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