LI-190 Quantum Sensor
During photosynthesis, plants use energy in the region of the electromagnetic spectrum from 400-700 nm. 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 micromoles of quanta per second per square meter (mmol s-1 m-2). Plant scientists, horticulturists, ecologists, and other environmental scientists use the LI-190 Quantum Sensor to accurately measure this variable.
Measure Photosynthetically Active Radiation
Accurate measurements are obtained under all natural and artificial lighting conditions because of the computer-tailored spectral response of the LI-190. Colored glass filters are used to tailor the silicon photodiode response to the desired quantum response. An interference 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. This sensor, developed from earlier work (1), was pioneered by LI-COR and has become the standard for PPFD measurement in most photosynthesis-related studies.
The LI-190 is also used in oceanography, limnology, and marine science as a reference sensor for comparison to underwater PAR measured by the LI-192 Underwater Quantum Sensor and LI-193 Spherical Underwater Quantum Sensor.
There are three different terminations available for the LI-190 Quantum Sensor:
The LI-190SA Quantum Sensor has a cable that terminates with a BNC connector. This allows for easy and direct connection to the LI-250A Light Meter or LI-1400 DataLogger.
The LI-190SZ Quantum Sensor terminates with bare leads (no connector). It can be connected to a data acquisition device or datalogger that measures millivolts when a 604 Ohm shunt resistor is used. As an alternative, the 2290 Millivolt Adapter can be purchased with the LI-190SA. The 2290 Millivolt Adapter uses a 604 Ohm precision resistor to convert the LI-190 output from microamps to millivolts.
The LI-190SL is an LI-190SA and a standardized output millivolt adapter. The LI-190SL produces a standardized 10 mv/2000 µmol s-1 m-2 output that eliminates the need to change calibration constants or multipliers when type SL sensors are exchanged in the field.
The LI-190 Quantum Sensor comes with a standard 10 feet (approximately 3 m) of cable. You may also order the LI-190 with 50 feet (approximately 15 m) of cable using the LI-190SA-50, LI-190SZ-50 or LI-190SL-50 part numbers. 50-foot and 100-foot extension cables are also available.
The 2003S Mounting and Leveling Fixture is recommended for each sensor unless other provisions for mounting are made.
Ordering Information
LI-190SA Quantum Sensor (with BNC connector)
LI-190SZ Quantum Sensor (with bare leads)
LI-190SL Quantum Sensor (LI-190SA and standardized millivolt adapter)
LI-190SA-50 Quantum Sensor (with BNC connector)
LI-190SZ-50 Quantum Sensor (with bare leads)
LI-190SL-50 Quantum Sensor (LI-190SA-50 and standardized millivolt adapter)
2290 Millivolt Adapter (used with the LI-190SA)
2003S Mounting and Leveling Fixture
2222SB-50 Extension Cable (50 ft) for the LI-190SA or LI-190SL
2222SB-100 Extension Cable (100 ft) for the LI-190SA or LI-190SL
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