Advantages
The LI-7500A is a high speed, high precision, non-dispersive infrared gas analyzer that accurately measures densities of carbon dioxide and water vapor in-situ. With the eddy covariance technique, these data are used in conjunction with sonic anemometer wind speed to determine the fluxes of CO2 and H2O into and out of ecosystems.
The LI-7500A accepts analog data from a sonic anemometer and logs complete data sets to a removable USB storage device.
- Low power consumption: 12 W during normal operation
- High Speed: up to 20Hz bandwidth
- High Precision: 0.11 ppm CO2, 0.0047ppt H2O*
- Excellent stability
- Absence of tubing eliminates delays and sorption effects
- No Signal Attenuation for CO2/H2O
- Suitable for harsh environments
Key Features
The LI-7550 (included) is a weatherproof enclosure houses the control unit's high speed Digital Signal Processing (DSP) electronics. Ethernet and Serial data are output at selectable speeds of up to 20 Hz, and linearized user-configurable Digital-to-Analog Converters (DACs) output analog signals at up to 20 Hz bandwidth. The LI-7550 also offers SDM communication for use with Campbell Scientific data loggers.
* at 10 Hz, at 370 ppm CO2 and 10 mmol/mol H2O
Based on the Proven LI-7500 Platform
- Precision and accuracy specifications identical to the LI-7500.
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- Uses proven theory and configuration
- Full backwards compatibility with applications
made for the LI-7500. Learn more: - USB data logging of synchronized data sets, including sonic anemometer wind speed, CO2/H2O data, and auxiliary data at 20Hz.
- Ethernet communication enables two-way global transfer of data and configuration files
- Includes the new LI-7550 Analyzer Interface Unit
- High speed analog inputs for auxiliary sensors including a sonic anemometer
- Flexible outputs, including Ethernet, SDM, RS-232, high speed Digital-to-Analog converters
- Extended cables – 5 or 10 meter
- Low chopper motor housing temperature setting for cold climates
- Saves energy in cold environments
New Features
Eddy Covariance
The LI-7500A is designed for the eddy covariance technique. With the eddy covariance method, the flux, Fc of gas c (e.g. CO2, H2O) is given by 
where c' is the density fluctuations of the gas (mmol/m3), and w' is the vertical wind velocity fluctuations (m/s). The LI-7500A has the high speed and high precision required for this method. The flux of CO2 and H2O is obtained from the vertical wind speed (measured with a sonic anemometer) and the concentration of the gas (measured with the LI-7500A).
Advantages of the LI-7500A for Eddy Covariance Measurements
- LI-7500A integrates easily with any fast sonic anemometer (ATI, CSI, Gill, Kaijo, Metek, RM Young).
- Includes the LI-7550 Analyzer Interface Unit for datalogging.
- Basic station (LI-7500A, sonic anemometer) requires 20 W or less. Can be powered by solar panel and batteries, or a household generator.
- Portability: the light weight analyzer can be deployed nearly anywhere.
The analyzer and control unit have a total combined weight of 12 lbs.
Applications
The LI-7500A is an excellent choice for scientists who wish to measure CO2 and H2O flux and density over many environments, including natural and agricultural ecosystems, urban areas, and water bodies. Ecosystems commonly measured include grasslands, deciduous forests, tropical environments, scrublands, deserts, wetlands, and others.
Wetlands: In wetland ecosystems, where access to mains power is often limited, the low power and low maintenance features of the LI-7500A make it an obvious choice for CO2/H2O density measurements.
Urban Flux: Urban environments occupy a significant and growing portion of Earth’s surface. CO2/H2O flux from urban ecosystems cannot be ignored. The LI-7500A is ideally suited for these applications with its excellent stability and undampened measurements. Learn More...
Aircraft Eddy Covariance: Scientists have mounted the LI-7500 to fixed wing and rotary-wing aircraft and successfully measured CO2 and H2O flux. Be sure to check FAA guidelines before attempting this kind of measurement.
Learn More... 
Agro-ecosystem Flux: Agricultural ecosystem flux varies with crop type, management regime, season, region, and many other variables. The long term stability and low power requirements make the LI-7500A an ideal instrument for these applications.
CO2 and H2O Flux over Water Bodies: Lakes, tidal zones, seas, and oceans are very relevant to the global carbon cycle. The LI-7500 is used on stationary platforms, buoys, and boats to measure CO2 and H2O flux in these environments. The low power demands and relative insensitivity to vibration make the LI-7500A an ideal instrument for these applications.
Carbon Capture and Sequestration: The eddy covariance method is an effective way to monitor large areas where CO2 may escape from the subsurface. Before attempting to detect a leak from an underground storage location, the baseline CO2 flux must be established. The LI-7500A is an excellent instrument for all stages of CCS monitoring – including pre-injection, injection, and post-injection phases. Learn More...
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Software
The LI-7500A has two software components: the embedded instrument firmware and the Windows® interface software. The internal firmware controls the instrument, while the Windows interface software is used to configure the LI-7500A.
The intuitive Windows software interface provides versatile, yet simple instrument configuration. With a few mouse clicks, you can easily configure the six fully-linearized DACs, SDM output, bandwidth, and time delay settings. In addition, you can set up USB data logging, view the live data stream, and examine complete diagnostic information. There is no need to learn a complex programming language to configure datalogging.
Click here for latest software updates.
View LI-7500A Software Screenshots:
LI-7500A Software Main Screen
Data Logging
Outputs
World-wide Standard
The 7500 family (including the LI-7500 and LI-7500A) is the most widely used group of open path CO2/H2O analyzers in the world. Since its introduction in 1999, scientists have come to know that the LI-7500 provides high precision, accuracy, and stability. The LI-7500A continues to provide the high performance that scientists expect.
The LI-7500 family has been directly cited in over 1500 scientific publications. Data collected with the LI-7500 have been cited in UNFAO (United Nations Food and Agriculture Organization) publications, IPCC Reports, and the journals Science and Nature.
References from Google Scholar™
Common Internet searches can be performed with Google, and many articles can be found with Google Scholar:
The LI-7500/7500A is used by major flux networks around the world including...
| FLUXNET | AMERIFLUX | ASIAFLUX | FLUXNET-CANADA |
| CARBOEUROPE | EUSTACH-LBA | KOFLUX | OZFLUX |
| CHINAFLUX | GREENGRASS | CARBOMONT | Other Links: ILTER |
LI-7500A images courtesy of National University of Singapore, Princeton University, National Institute for Agro-Sciences
Ordering Information
LI-7500A Open Path CO2/H2O Analyzer
High precision and high-speed analyzer for eddy covariance measurements. Includes calibration shroud, analyzer cable (5 meters), data cables (5 meter), Windows® software, and instruction manual.
- LI-7500ADP Open Path CO2/H2O Analyzer DP Package Includes:
- LI-7500A Open Path CO2/H2O Analyzer
- LI-610 Portable Dew Point Generator
- Greenhouse Gas Package 1:
- LI-7500A Open Path CO2/H2O Analyzer
- LI-7700 Open Path CH4 Analyzer
- Analyzer Extension Cable (5 meters)
- LI-7500 Upgrade Kit:
- Upgrades existing LI-7500s to include features of the LI-7500A
| LI-7500A Part No. | Description |
|---|---|
| 184-05637 | U-Bolt for 6575-033 Bracket |
| 222-01824 | Bev-a-line Tubing |
| 392-10093 | SDM Interface Cable |
| 9975-030 | Power Cable |
| 392-10268 | RS-232 Cable (to connect to external port on control box) |
| 392-10109 | Analog Input Cable |
| 392-10109 | DAC Output Cable |
| 439-04214 | 5 Amp Fast Fuse 125 V |
| 6575-033 | Control Unit Mounting Bracket |
| 7500-950 | Internal Chemical Bottles Kit (2 small bottles) |
| 392-09806 | Sensor Head Cable |
| LI-7550 | Analyzer Interface Unit |
| 7500-028 | Standard Spares Kit |
| LI-7540 | Open Path CO2/H2O Analyzer (Sensor Head) |
| 9975-024 | Calibration Tube Assembly (Shroud) |
| 9975-014 | Shroud Gasket Kit |
| 9975-026 | Ambient Temperature Sensor |
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