Line Quantum Sensor
The LI-191R Line Quantum Sensor measures PAR integrated over its 1-meter length. It is used to measure sunlight under a plant canopy, where the light field is non-uniform. The LI-191R makes it easy to measure under-canopy light in many plots quickly and consistently. It measures light in units of Photosynthetic Photon Flux Density (PPFD), which is expressed as μmol s-1 m-2.
Why choose the LI-191R?
Integrated measurements using a single detector prevents variance found in sensors that use multiple detectors
Selected by the National Ecological Observatory Network (NEON®) for integrated PAR measurements
How does it work?
The LI-191R uses a 1-meter long quartz rod under a diffuser to direct light to a single filtered silicon photodiode. The entire LI-191R diffuser is sensitive to light over its 1-meter length. Since the diffuser is one continuous piece, the LI-191R essentially integrates an infinite number of points over its surface into a single value that represents light from the entire 1-meter length. Optical filters block radiation with wavelengths beyond 700 nm, which is critical for under-canopy measurements, where the ratio of infrared to visible light may be high. The unique design of the LI-191R provides an excellent quantum response that is close to the ideal quantum response.
Sensitivity: Typically 7 μA per 1,000 μmol s-1 m-2
Linearity: Maximum deviation of 1% up to 10,000 μmol s-1 m-2
Response Time: 10 μs
Size: 121.3 L × 2.54 W × 2.54 cm D (47.7” × 1.0” × 1.0”)
Weight: 1.4 kg (3.0 lbs.)
Cable Length: 3.1 m (10.0 ft.)