General Information

This manual provides basic operating instructions for the LI-190R Quantum Sensor (right) and the LI-191R Line Quantum Sensor and their accessories. LI-COR quantum sensors measure photosynthetically active radiation (PAR) with an enhanced silicon photodiode mounted under a cosine-corrected acrylic diffuser. A custom spectral filter helps achieve the desired spectral response.

The sensor output is a current (μA) signal that is directly proportional to hemispherical PAR. A multiplier is used to convert the current signal into units of radiation (µmol s-1 m-2).

Typical applications for the LI-190R include agriculture, greenhouses, growth chambers, controlled laboratory conditions, and environmental research.

The LI-191R Line Quantum Sensor is designed to measure PAR in applications where the radiation to be measured is spatially non-uniform, such as within plant canopies. The LI-191R spatially averages incident radiation over the 1-meter length of the diffuser, minimizing errors introduced by shadows and sunflecks. The incident radiation passes through the diffuser and is directed uniformly to a single silicon photodiode.

Comparing LI-COR Radiation Sensors

Each LI-COR radiation sensor is optimized for a particular application and measurement type (Table 1‑1). LI-192SA and LI-193SA sensors are submersible, but they can also be used in the atmosphere. The LI-191R Line Quantum Sensor is often used within plant canopies. LI-190R, LI-200R, and LI-210R sensors consist of a sensor head attached to a removable base and cable assembly.

Table 1‑1. LI-COR radiation sensors.
Sensor Measurement Units Waveband
LI-190R Quantum Sensor Photosynthetically active radiation (PAR) μmol s‑1 m‑2 400 to 700 nm
LI-191R Line Quantum Sensor
LI-192SA Underwater Quantum Sensor
LI-193SA Underwater Spherical Quantum Sensor
LI-200R Pyranometer Global solar radiation W m‑2 400 to 1100 nm
LI-210R Photometric Sensor Light as perceived by the human eye Lux or klux 450 to 650 nm
Figure 1‑1. LI-COR radiation sensors.

Cable Options for the LI-190R

The detachable base and cable assembly provides benefits including:

  • Reduced cost of cable repairs
  • The ability to replace or recalibrate a light sensor without removing the cable from the mounting structure
  • Cable interchangeability with any LI-190R, LI-200R, or LI-210R sensor head
Figure 1‑2. Sensor base and cable assembly detached from the sensor head.

The shielded cable leading from the sensor base terminates with either bare wire leads or a weather-resistant, nickel-plated brass BNC connector (Figure 1‑3). For sensors with a BNC connector, the body of the connector carries a positive signal and is connected to the shield of the cable, while the center conductor is negative. This arrangement reduces electronic interference.

Figure 1‑3. Sensor terminals are either a BNC connector and bare leads.

BNC or bare leads (BL) terminal types are available with cable lengths of 2, 5, 15, or 50 meters.

Calibrated LI-190R, LI-200R, or LI-210R sensor heads (without cables) are available for purchase. Sensor heads can replace damaged heads, or be used as spares. Any cable assembly can be used interchangeably with any LI-190R, LI-200R, or LI-210R sensor head.

Cable Options for the LI-191R

The cable for an LI-191R Line Quantum Sensor terminates with a BNC connector on each end. One end connects to the sensor and the other end connects to the logger, meter, or millivolt adapter. The cable for the LI-191R is available in 2-meter or 5-meter lengths.


Accessories for use with the LI-190R and LI-191R:

Additional accessories for use with the LI-190R:

  • 2003S Mounting and Leveling Fixture. Anodized aluminum with stainless steel leveling screws and a weatherproof spirit level
  • 2001S Sensor Base Cover. Anodized aluminum


LI-COR Quantum Sensors connect directly to devices that read a current (µA) sensor signal (Table 1‑2). Table 1‑3 lists configurations for producing a voltage signal.

Table 1‑2. Configurations for a current (µA) signal. Ultimate termination is BNC or bare leads.
Sensor Termination Type... ...connects to...
LI-190R-BNC or LI-191R-BNC
  • LI-1500 Light Sensor Logger
  • LI‑1400 Datalogger
  • LI-250A Light Meter
LI-190R-BL (bare leads)
  • Terminal block of the LI‑1400 Datalogger
  • Non-LI-COR devices that read a current (μA) signal
Table 1‑3. Configurations for a voltage signal. Ultimate termination is bare leads.
Sensor Termination... ...coupled with... ...connects to...
LI-190R-BNC or LI-191R-BNC 2290 mV Adapter
(0 to 10 mV output)
Devices that read a voltage signal with good resolution (in the µV range)
LI-190R-SMV or LI-191R-SMV Include a standard output mV adapter (part number 2319) with 10 mV output at full scale
LI-190R-BL Precision resistor
LI-190R-BNC or LI-191R-BNC 2420-BNC Amplifier
(-2.5 to 5.0 V output)
Devices that read a voltage signal
LI-190R-BL 2420-BL Amplifier
(-2.5 to 5.0 V output)