General information
The LI-7700 is a high-speed, high-precision open path methane analyzer designed for use in eddy covariance flux and atmospheric monitoring applications. It uses Wavelength Modulation Spectroscopy (WMS) to make high-speed, precise measurements of methane concentrations at ambient pressure and temperature. It is designed to withstand environmental extremes expected during outdoor deployments. Some features of the LI-7700 include fast response (data are output at up to 20 Hz bandwidth), low power requirements (8 W during normal operation), withstands outdoor environmental extremes, including freezing weather and high temperatures (-25 to 50 °C) and rain without damage or calibration shifts.
When used in conjunction with an LI-7500A/RS/DS or LI-7200/RS CO2/H2O gas analyzer and the SmartFlux System, measurements from the gas analyzers and sonic anemometer are logged in self-contained data files and flux results computed in real-time by EddyPro on the SmartFlux 2 or 3 System.
Contact LI-COR if you have questions about the suitability of the LI-7700 in your application.
Suggested Reference: When referring to this instruction manual in scientific literature or other publications, we recommend the following citation:
LI-COR, Inc. 2020. LI-7700 Open Path CH4 Analyzer Instruction Manual. LI-COR, Inc. Lincoln, NE.
What’s what
If you have just taken delivery of your LI-7700, check the packaging list to verify that you received everything that was ordered. The standard LI-7700 will include:
The LI-7700 Open Path CH4 Gas Analyzer
LI-7700 Analyzer - Includes the laser, detector, sampling path, mirrors, heaters, and laser control electronics. The radiation shield (not shown) is attached to the upper housing prior to shipment.
LI-7700 components
Cable connections
The connection panel on the bottom of the analyzer includes the following components:
- Power In: Provide a +10.5 to 30 VDC 3 Amp power supply.
- The LI-7700 powers on when a suitable power supply is connected. It always starts up with the most recent settings.
- Fuse Housing: Use only a 8A FAST 250V TR5 UL fuse.
- An extra fuse is included in the spares kit (part number 438-15034). Early models used a 5 amp fuse. Contact LI-COR if you have questions about the fuse.
- Status LED: Stays solid green when the LI-7700 has finished starting up.
- Power LED: Stays solid green when a suitable power supply is connected.
- Analog Inputs: Connector for the analog input cable or 7550-101.
- Washer Power: Supplies power to the external washer unit accessory.
- Ethernet Connection: Port for Ethernet communication.
- Ethernet LED: Blinks at about 4 Hz when the Ethernet connection is active.
- Network Reset: Depress this button to reset the network connection.
- Mounting Post: The mounting post is attached with two ¼”-20 bolts (5/8”).
Spares kit and cables
Part Number: 9977-019
The items in Table 1‑1 are included in the LI-7700 spares kit. Some may be shipped in separate boxes.
- Ethernet Data Cables – Two Ethernet cables are included: part number 392-10108 is a 5 m cable terminated on both ends with male Turck connectors; one end attaches to the LI-7700 Ethernet output, while the end attaches to either the 0.3 m Ethernet adapter cable (part number 392-10107), or to an LI-7550 Analyzer Interface Unit. When both cables are used, the LI-7700 can be connected to an Ethernet wall socket, Ethernet hub, or the Ethernet port on your computer.
- Power Cable – (part number 9975-030) Used to connect the LI-7700 to a 10.5 to 30 VDC power supply. The power cable has 4 wires: brown and white are tied to a black lead, which connects to the negative (-) power supply terminal; blue and black are tied to a red lead, which connects to the positive power supply terminal (+).
- Washer Assembly – The washer assembly includes a reservoir, pump, hose, washer nozzle, and mounting hardware.
- Calibration Shroud – The calibration shroud is used to isolate the LI-7700 optical path during calibration verification.
- Calibration Certificate – This documents the performance characteristics of your particular instrument when it left the factory. Keep this sheet for future reference.
Optional accessories
Several accessories are available for the LI-7700.
Data cables
Optional data cables with 8-pin Eurofast-to-RJ45 connectors are available in 5-, 25-, and 50-meter lengths. These cables connect the external Ethernet terminal on the LI-7550, LI-7500DS, or LI-7700 to a network switch.
Description | Part Number |
---|---|
5 meter data cable (optional) | 392-13977 |
25 meter data cable (optional) | 392-16699 |
50 meter data cable (optional) | 392-13767 |
Mounting hardware
The LI-7700 can be mounted directly to a tripod cross arm with one 1" × ¾" crossover fitting (part number 7900-342).
For a range of height adjustment options, use the mounting kit (7900-340).
7550-101 Auxiliary Sensor Interface
The 7550-101 is an optional weatherproof junction for analog inputs on the LI-7700 and for the analog outputs from the LI-7550. Detailed instructions for using the 7550-101 are provided later (see Analog inputs (LI-7700), Analog inputs (LI-7550), or Analog outputs (LI-7550)).
Description | Qty. | LI-COR Part No. |
---|---|---|
U-Bolt, ¼" by 20 | 2 | 184-09842 |
Hex Nuts | 4 | 798-01788 |
Quick Connect Plug | 10 | 300-07393 |
Santoprene Tubing | 2 ft (60 cm) | 222-08325 |
LI-7550 Analyzer Interface Unit
The optional LI-7550 enhances the functionality of the LI-7700 by providing compatibility with other data logging and communication systems. Detailed instructions for using the LI-7550 with the LI-7700 are provided later (see Operation with the LI-7550).