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The LI-7500RS combines the ruggedness of a field ready instrument with the speed and precision needed for eddy covariance measurements. Designed for long-term deployment, the LI-7500RS improves upon a proven platform.


Temperature-controlled source and detector provide stable measurements—even in wide temperature fluctuations.


Precision optical components reduce sensitivity to contamination in dusty environments.


Scratch-resistant sapphire lenses for simple cleaning in the field.


High-performance brushless chopper motor provides dependable long-term operation.

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How It Works

The LI-7500RS uses non-dispersive infrared spectroscopy to measure CO2 and water vapor densities in air. It transmits infrared radiation through temperature-controlled optical filters, then through the open sample path to a thermally regulated lead selenide detector. Some of the infrared radiation is absorbed by CO2 and water vapor in the sample path. Gas densities are computed from the ratio of absorbed radiation to a reference.

LI-7550 Analyzer Interface Unit

Included with each LI-7500RS, it houses the gas analyzer electronics, a 16 GB USB drive for data logging, and the SMARTFlux System. The LI-7550 has connections for a 3-dimensional sonic anemometer and provides Ethernet communication, making it easy to connect the LI-7500RS with FluxSuite Software.


The LI-7500RS software simplifies eddy covariance system setup, while enabling easy access to calibration and diagnostic information for the gas analyzer.

Eddy Covariance System Capabilities

Sonic Anemometer Compatibility

The LI-7500RS can be used with any high-speed 3-dimensional sonic anemometer that provides analog outputs—so you can choose the ideal anemometer for your site conditions and measurement objectives. The analyzer can be installed under or beside the sonic anemometer to minimize flow distortion and related flux errors.

LI-COR provides a variety of compatible sonic anemometers and data cables to simplify this connection.

Tripod and Tower Installations

Sensor head cables are available in five- and ten-meter options. You can install the sensor head up to ten meters from the LI-7550. The Ethernet cable can extend up to several hundred meters from the LI-7550.

Expansion Capabilities

The LI-7500RS supports standard network communication protocols so you can easily add networked devices, including an LI-7700 Open Path CH4 Analyzer, a LI-COR Biomet System, and a cellular or satellite radio.


Access the instrument over the Internet with a direct connection, cellular modem, or satellite communication system—and connect with FluxSuite for online access to your site and networking between sites and research groups.

LI-7500RS Specifications

CO2 Measurements

  • Calibration range: 0 to 3000 µmol mol-1
  • Accuracy: Within 1% of reading
  • Zero drift (per °C):
    • ±0.1 ppm typical
    • ±0.3 ppm maximum
  • RMS noise (typical @ 370 ppm CO2 and 10 mmol mol-1 H2O):
    • @5 Hz: 0.08 ppm
    • @10 Hz: 0.11 ppm
    • @20 Hz: 0.16 ppm
  • Gain drift (% of reading per °C @ 370 ppm):
    • ±0.02% typical
    • ±0.1% maximum
  • Direct sensitivity to H2O (mol CO2/mol H2O):
    • ±2.00E-05 typical
    • ±4.00E-05 maximum

H2O Measurements

  • Calibration range: 0 to 60 mmol mol-1
  • Accuracy: Within 2% of reading
  • Zero drift (per °C):
    • ±0.03 mmol mol-1 typical
    • ±0.05 mmol mol-1 maximum
  • RMS noise (typical @ 370 ppm CO2 and 10 mmol mol-1 H2O):
    • @5 Hz: 0.0034 mmol mol-1
    • @10 Hz: 0.0047 mmol mol-1
    • @20 Hz: 0.0067 mmol mol-1
  • Gain drift (% of reading per °C @ 20 mmol mol-1):
    • ±0.15% typical
    • ±0.30% maximum
  • Direct sensitivity to CO2 (mol H2O/mol CO2):
    • ±0.02 typical
    • ±0.05 maximum


  • Analysis Type: Absolute, non-dispersive infrared spectroscopy
  • Data Storage: 16 GB removable industrial grade USB storage device included
  • Data Communication: Ethernet, Synchronous Devices for Measurement (SDM; >50 Hz), RS-232 (115,200 baud; 20 records per second max), 6 DACs (0-5 V; 300 Hz)
  • Inputs: Four analog input channels (differential; bi-polar; ±5 V; 300 Hz)
  • Operating Temperature Range: -25 to 50 °C (-40 to 50 °C verification test available on request)
  • Power Requirements: 10.5 to 30 VDC
  • Power Consumption: 12 W nominal (up to 30 W during startup)
  • Detector: Thermoelectrically cooled lead selenide
  • Bandwidth: 5, 10, or 20 Hz, user-selectable
  • User Interface: Windows® based
  • Cable length: 5 meters (all cables); 5-meter head cable extension available

Analyzer Head

  • Size: 6.5 cm (2.6” diameter), 30 cm (12”) length
  • Weight: 0.75 kg (1.65 lbs.)

LI-7550 Analyzer Interface Unit

  • Size: 35 cm × 30 cm × 15 cm (13.8” × 12” × 6”)
  • Weight: 4.4 kg (10 lbs)

7550-101 Auxiliary Sensor Interface

  • Size: 11.5 cm × 6.5 cm × 4.2 cm (4.5” × 2.6” × 1.7”)
  • Weight: 0.39 kg (0.85 lbs) including mounting bracket

Specifications subject to change without notice.

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