The LI-720 and Carbon Node
Welcome, and thank you for your purchase of the LI-720 Carbon Flux Sensor. The LI-720 reports the total transport of carbon dioxide gas and evapotranspiration over an area, along with other biological and meteorological parameters. The LI-720, when paired with an IoE Module, is a Carbon Node on LI-COR Cloud.
Warning: The LI-720 has internal voltages that may exceed 100 volts. Handle the device carefully if the external cover is removed. Avoid touching circuit boards or exposed conductors.
Warning: The gas analyzer housings include small packets of Ascarite II and Magnesium Perchlorate. Use caution if handling these components.
If you have just received your LI-720, check the packing list to be sure you have everything that you ordered. The LI-720 may include some or all of the components listed below.
Caution: Keep the box and foam packaging materials so you can ship and store the instrument safely.
LI-720 Carbon Flux Sensor
Part number 99512-012
The sensor (Figure 1‑1) features one cable connector for power and data and a mounting post for installation onto an IoE Module, a tripod, or other platform using a 1" (2.54 cm) cross-over fitting.
USB data and power cable
Part number 99512-062
The USB data and power cable is to operate the device from a computer for configuration and calibration procedures. The LI-720 cannot be operated in a field situation with the USB cable because the USB power supply is not adequate.
Data and power cable
Part number 392-19605
Each sensor includes a 5-meter long combined data and power cable. The cable features a connector and bare leads for connecting to a datalogger that supports SDI-12 and serial (RS-232) communication.
Spares kit
Part number 99512-056
Each LI-720 is shipped with a spares kit, which includes a variety of spare parts (see Table 1‑1).
CarbonWare application
An application for Windows OS computers, CarbonWare is used to adjust the user-calibrations, apply firmware updates, enter site information relevant to flux calculations (if not using LI-COR Cloud), and other tasks.
Download CarbonWare here.
Optional accessories
The accessories below are available from LI-COR.
Calibration shroud
Part number 99512-055
The calibration shroud is required for setting the zero and span. You can use a single shroud to calibrate multiple LI-720 instruments, and therefore do not include one with each sensor. The shroud includes three meters of Bev-a-Line tubing to connect to a tank.
Caution: Do not attempt to calibrate with a homemade shroud. The calibration shroud is designed to prevent reflections and optimize flow. Attempts to calibrate with a homemade shroud tube will lead to unexpected performance.
Extension cable
Part number 392-20529
25-meter extension cable with weather-resistant connectors on each end. Extends the data/power cable for a total length of 30 meters.
IoE Module overview
The IoE Module may include some or all of the following components and services:
- Cellular service plan and access to LI-COR Cloud (1 year).
- Backup data logging to a removable Micro SD card (all configurations).
- Built-in charge controller for the solar power supply (all configurations).
- Solar and battery power supply (optional).
- Mounting structure and enclosure for sensors and equipment (optional).
The IoE Module powers sensors for continuous long-term operation, while simultaneously posting data to the LI-COR Cloud via a cellular network. It allows operators to view data and assess results from sensors without visiting the sites.
IoE configurations are given in Table 1‑2 and described in the following sections.
| Part # | LI-COR Cloud | IoE Module | Frame and Mast | Solar Power |
|---|---|---|---|---|
| 99512-014 | - | Yes | - | - |
| 9000-01 | Yes | - | - | - |
| 9000-02 | Yes | Yes | Yes | Yes |
| 9000-031 | Yes | Yes | - | - |
| 9000-04 | Yes | Yes | Yes | - |
IoE module only
Part number 9000-03
The stand-alone IoE module includes the enclosure, electronics, power and data cable for the LI-710 (392-20750), one year of cellular service, and one year of LI-COR Cloud data service. We recommend the optional hardware mounting kit (9000-05) with this configuration.
IoE module, mast, and frame assembly
Part number 9000-04
This configuration includes everything listed previously, plus the frame with mast, assembly hardware, instrument and guy wire adapter, earth anchor kit, grounding kit, and tool kit. The mast allows height adjustment resolution of 20 cm at heights from 2 to 5 meters.
Assembly hardware kit
The hardware kit includes parts and accessories to assemble the system.
| Description | Part # |
|---|---|
| Braces; 1.25×0.5" U-channel; 39" long | 98512-052 |
| M6×1 6-mm stainless lock nuts (4) | 157-20957 |
| M6×1 12-mm cap screws (4) | 151-20958 |
| Instrument and guy wire adapter (1) | 98512-081 |
| Instrument and guy wire adapter (discontinued) | 98512-013 |
| M8×1.25 set pins (2) | 155-16763 |
Earth anchor kit
The anchoring kit includes hardware to stabilize the mast when it is extended.
| Description | Part # |
|---|---|
| 14-inch earth anchors with eye-bolts (3) | 609-20822 |
| Guy wires with clip (3) | 609-20846 |
| Gripple cable locks (3) | - |
| Gripple release key (1) | 611-21003 |
Grounding kit
The grounding kit includes hardware for an earth-ground.
| Description | Part # |
|---|---|
| Ground rod (1); 1.5 meter | 609-20976 |
| Ground wire (1); 2 meters; 8-gauge | 374-12937 |
| Ground rod clasp (1) | 354-20819 |
Tools
Several assembly tools are included.
| Description | Part # |
|---|---|
| 10 mm and 1/2" wrench (1) | 98512-066 |
| Multipurpose screwdriver (1) | 611-07902 |
| 4 mm hex key (1) | 611-21236 |
IoE module, mast, frame, battery, and solar panel
Part number 9000-02
The turnkey IoE Module includes everything listed previously, plus a solar panel, battery, and hardware for the solar power and battery. The panel rails provide angle adjustments to allow the solar panel to face the sun in different latitudes and seasons.
Battery kit
Part number 99512-031
The battery kit includes a 100-Ah 12-volt absorbed glass mat (AGM) battery, cables, and a bracket to secure the battery.
| Description | Part # |
|---|---|
| 100-Ah 12-volt AGM lead-acid battery | 442-20708 |
| Battery cable assembly | 99512-022 |
| Battery hold-down bracket | 98512-065 |
Solar panel kit
The solar power kit includes a solar panel and hardware for the power supply.
| Description | Part # |
|---|---|
| 100-watt 12-volt solar panel | 590-20735 |
| Solar panel extension cables | 392-20841 |
| Solar panel bracket assemblies (2) | |
| Angle bracket (installed) | 98512-050 |
| U-channel bracket (installed) | 98512-051 |
| 16-mm serrated flange bolts (installed) | 150-20955 |
| M6×1 6-mm nylon lock nuts (installed) | 157-20957 |
| 1/4" clevis pin with 1/16" cotter pin | 186-20847 |
| M6×1 12-mm cap screws (4) | 151-20958 |
| Panel clamps (4) | 98512-010 |
Sensor cable
Part number 392-20750
Each IoE Module includes a sensor cable to connect the LI-710 or LI-720 to the SENSOR connector on the IoE Module. It is a 5-meter long 5-pin cable with connectors on each end.
Optional mounting hardware
Part number 9000-05
Stand-alone IoE modules (9000-03) can be mounted with the mounting hardware kit, which is compatible with a vertical mast, horizontal cross arm, or pipe at nearly any angle. The kit includes two brackets, two band clamps, and additional hardware.
Warning: Do not use the optional mounting hardware with the battery kit (99512-031) or any other heavy battery. The mounting hardware (9000-05) is not strong enough to safely hold the battery, and may present a risk of injury if a battery is installed.
Optional auxiliary power cables
Power cables are used to power the IoE Module from external power (9 to 33 VDC, 3.0 A). Power cables are available in three lengths:
| Description | Part # |
|---|---|
| 3-meter power cable | 8150-706 |
| 5-meter power cable | 9975-030 |
| 25-meter power cable | 9975-056 |
Enclosure and electronics
The enclosure houses the electronics, antennas, and other components.
Warning: Read and understand the operating instructions and safety information before using this equipment. Failure to understand the safety information may result in bodily injury, damage to equipment, or unsatisfactory results.
Components
Components of the enclosure are labeled and described below.
- Display: Monochrome display that presents status and configuration information. See The IoE module interface for a tour.
- Buttons: Buttons include power (
), navigation (
, 
, 
, 
), select (
), and mount/unmount card. - Battery Shelf: To support the optional battery. Always use the hold-down bracket when a battery is installed.
- Serial Number Label: The serial number label gives the product serial number, which may be useful if you need technical support.
- Micro USB Port: To connect to a computer for manual firmware updates. Accepts a Micro-B connector.
- Micro SD Card Slot: The slot is for the included Micro SD card to store a backup of data. An 8 GB card is included (part number 616-21301). The 8 GB card can store many years of data, typically. Most micro SD cards (FAT12, FAT16, FAT32, and ExFAT format) will work as long there is free space for files.
- Battery Cable Connector: The cable from the optional 12-volt lead-acid battery attaches to this connector.
- Auxiliary Power Out: One auxiliary power supply is provided inside the enclosure. Contact LI-COR technical support if you want to use the power out.
External connectors
The external connectors are for sensors, auxiliary power, and solar panels.
Warning: Read and understand the operating instructions and safety information before using this equipment. Failure to understand the safety information may result in bodily injury, damage to equipment, or unsatisfactory results.
- SDI-12 Connectors: Two connectors for SDI-12 devices. Power, configuration, and data transfer are supported. The device must have a 5-pin sealed connector. The Stevens Soil Probe available from LI-COR (part number 900-19016) has the connector. The SDI-12 power supply provides 12 VDC with a maximum of 2.5 amps total, including the Sensor Connector.
- Sensor Connector: Accepts the LI-710 or LI-720 cable (392-20750). It features a 5-pin sealed connector for a combined SDI-12/RS-232 port. The SDI-12 power supply provides 12 VDC with a maximum of 2.5 amps total, including the two SDI-12 connectors.
- Auxiliary Power Input: For operation from an external power supply (other than the solar panel or battery). Supports 9 to 33 VDC, 3.0 A maximum current.
- Solar Panel Inputs: To attach the solar panel extension cables. The maximum input is 9.15 A (circuitry is current limited to prevent damage). Compatible panels should output 17 to 21 V, with a maximum open circuit voltage of 32 V.
Extension cable (optional)
Part number 392-20529
25-meter extension cable with weather-resistant connectors on each end. Extends the IoE Module data/power cable for a total length of 30 meters.
Warning: Do not connect solar panels with voltage rating that is higher than specified. Doing so can damage equipment or cause injury.
Summary of theory of operation
The output from the LI-720 is computed CO2 flux, evapotranspiration, and energy flux for the previous time period (30 minutes by default but configurable from 5 to 30 minutes). Biomet outputs include photosynthetic photon flux density (PPFD), air temperature, relative humidity, wind speed, and wind direction averaged over the period. It uses the SDI-12 protocol to transfer computed results. It supports RS-232 serial communication to transfer raw (10 Hz) data to an IoE Module or external data recorder. It is directly compatible with LI-COR Cloud data management service. When connected to LI-COR Cloud, the LI-720 is a Carbon Node.
The LI-720 uses eddy covariance calculations that are optimized for the hardware and sensor configuration. It combines ultrasonic vertical wind speed measurements with high-precision gas measurements in the open air (non-dispersive infrared) to compute CO2 flux and evapotranspiration from the area surrounding the sensor. When the prevailing wind directions around the LI-720 are random or uniform, measurements represent the surrounding area and vegetation (known as the “fetch footprint”). When wind is from a prevailing direction, measurements represent the land area and vegetation under the prevailing winds. The fetch footprint represents an area around the LI-720 that is 50 to 100 times the height of the sensor above the canopy (e.g., a 2-meter height above the canopy has a fetch footprint of 100 to 200 meters).
The LI-720 also measures horizontal wind, and therefore, the fetch footprint of the measurement can be assessed on LI-COR Cloud. In a proper deployment, the footprint will represent a uniform land area surrounding the sensor or an area upwind of the prevailing wind direction (see Installing the LI-720 for more information).
