LI-7700 Open Path Methane Analyzer CDv1.0

LI-7700
Open Path CH4 Analyzer
Instruction Manual
LI-7700 Open Path CH4 Analyzer
Instruction Manual
Publication No. 984-10751
LI-COR, Inc.
4647 Superior Street
P.O. Box 4425
Lincoln, NE 68504-0425
USA
Telephone: (402) 467-3576
FAX: 402-467-2819
Toll Free: 1-800-447-3576 (U.S. & Canada)
Email: envsales@licor.com
envsupport@licor.com
www.licor.com
®
LI-COR, inc.
Environmental
4647 Superior Street
P.O. Box 4000
Lincoln, Nebraska 68504 USA
Phone: 402-467-3576
FAX: 402-467-2819
Information: 1-800-447-3576 (Toll-free U.S. & Canada)
E-mail: envsales@env.licor.com
Declaration of Conformity
Manufacturer’s Name: LI-COR, Inc.
Manufacturer’s Address: 4647 Superior Street
Lincoln, Nebraska USA 68504
declares that the product
Product Name: Open Path CH4 Gas Analyzer
Model Number(s): LI-7700
Product Options: None
conforms to the following Product Specifications:
EMC:
EN 55011 : 2002 Radiated Emissions, Class A
IEC 61000-4-2 : 2000 ESD, 4KV/8KV Contact/Air
IEC 61000-4-3 : 2002 Radiated RF Immunity, 10V/m
IEC 61000-4-4 : 2004 EFT/Burst
IEC 61000-4-5 : 2000 Surge Immunity, 1KV
IEC 61000-4-6 : 2003 Conducted RF Immunity, 3V
Supplementary Information:
The product herewith complies with the requirements of the EMC Directive 2004/108/EC.
Document #53-11453
February 9, 2010
ii
John Rada
Director of Engineering
NOTICE
The information contained in this document is subject to change without
notice.
LI-COR MAKES NO WARRANTY OF ANY KIND WITH REGARD TO THIS
MATERIAL, INCLUDING, BUT NOT LIMITED TO THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
LI-COR shall not be liable for errors contained herein or for incidental or
consequential damages in connection with the furnishing, performance, or use
of this material.
This document contains proprietary information, which is protected by
copyright. All rights are reserved. No part of this document may be
photocopied, reproduced, or translated to another language without prior
written consent of LI-COR, Inc.
© Copyright 2009, LI-COR, Inc.
Publication No. 984-10751
Printing History
New editions of this manual will incorporate all material since the previous
editions. Update packages may be used between editions that contain
replacement and additional pages to be merged into the manual by the user.
The manual printing date indicates its current edition. The printing date
changes when a new edition is printed. (Minor corrections and updates that
are incorporated at reprint do not cause the date to change).
The LI-7700 is covered by U.S. and international patents pending.
Microsoft® and Windows® are registered trademarks of Microsoft Corporation.
Eurofast® is a registered trademark of Turck Inc.
LI-COR, Inc. 4647 Superior Street Lincoln, Nebraska 68504
Phone: 402-467-3576 FAX: 402-467-2819
Toll-free: 1-800-447-3576 (U.S. & Canada)
envsales@licor.com www.licor.com
1st Printing – February 2010 rev1
iii
Welcome… ..................................................................................................... ix
1 General Information
1-1
Overview of the LI-7700........................................................................................... 1-1
What’s What ............................................................................................................ 1-2
The LI-7700 Open Path CH4 Analyzer ...................................................................... 1-2
Spares Kit and Cables ............................................................................................... 1-3
7550-101 Auxiliary Sensor Interface (optional) ......................................................... 1-5
LI-7550 Analyzer Interface Unit (optional) ................................................................ 1-6
LI-7700 Components and Connections ..................................................................... 1-7
Basic Setup ............................................................................................................... 1-9
Install the LI-7700 Computer Software ...................................................................... 1-9
Connect the Power Supply...................................................................................... 1-10
Connect the Data Cable.......................................................................................... 1-10
Launch the Software and Connect to an LI-7700..................................................... 1-11
Cleaning the Mirrors ............................................................................................... 1-12
2 Operation
2-1
Introduction to the LI-7700 Interface Software .......................................................... 2-1
Main View................................................................................................................ 2-1
About the LI-7700 Dialog Boxes ............................................................................... 2-4
Charting.................................................................................................................... 2-4
About charting ................................................................................................................................... 2-5
Configuring PC/Network Data Logging ..................................................................... 2-6
About Splitting Files......................................................................................................................... 2-7
About Logging Status Columns..................................................................................................... 2-7
Instrument Settings/Setup .......................................................................................... 2-8
Operating Temperature Range .................................................................................. 2-8
Manual Controls ....................................................................................................... 2-9
Configuring the Spin Motor Control ........................................................................ 2-10
Configuring Mirror Heater Control.......................................................................... 2-12
About LI-7700 Time Keeping .................................................................................. 2-13
Setting the Time...................................................................................................... 2-14
Creating an Instrument Configuration File............................................................... 2-15
Implementing a Configuration File.......................................................................... 2-15
LI-7700 Analog Inputs ............................................................................................ 2-16
v
Auxiliary Sensor Interface Terminals (Option 1) ...................................................... 2-17
Connecting Sensors to the Auxiliary Sensor Interface .............................................. 2-19
Thermocouple Inputs..................................................................................................................... 2-20
Configuring Auxiliary Sensors (LI-7700) .................................................................. 2-21
Deploying the LI-7700 ........................................................................................... 2-23
Mounting the LI-7700 ............................................................................................. 2-23
Positioning the LI-7700 ........................................................................................... 2-24
Grounding .............................................................................................................. 2-25
Mounting the Auxiliary Sensor Interface.................................................................. 2-25
Attaching the Mirror Cleaner/Washer Assembly ...................................................... 2-26
Mounting the Washer Reservoir .............................................................................. 2-27
3 Operation with the LI-7550 Analyzer Interface Unit
3-1
Power On................................................................................................................. 3-2
Connecting an LI-7700 to an LI-7550 ....................................................................... 3-2
Connecting with the RS-232 (Serial) Port .................................................................. 3-4
Cable Connections and Cables ................................................................................. 3-4
Power Cable ............................................................................................................. 3-5
SDM Interface Cable ................................................................................................. 3-5
Analog Input/Output Cable ....................................................................................... 3-5
Serial RS-232 Cable .................................................................................................. 3-7
Ethernet Cables ......................................................................................................... 3-8
LI-7550 Analog Inputs/Outputs................................................................................. 3-9
Auxiliary Sensor Interface Terminals (Options 2 & 3) ................................................ 3-9
Electrical Connections............................................................................................. 3-12
Configuring the LI-7550 ......................................................................................... 3-14
Configuring Analog Inputs (LI-7550)........................................................................ 3-14
Analog Input Time Delays ............................................................................................................ 3-14
USB Data Logging................................................................................................... 3-15
Configuring LI-7550 Outputs................................................................................... 3-17
RS-232 Output ................................................................................................................................ 3-17
Analog Outputs ............................................................................................................................... 3-18
SDM ................................................................................................................................................... 3-19
LI-7550 Clock ......................................................................................................... 3-20
Mounting the LI-7550 Analyzer Interface Unit........................................................ 3-22
vi
4 Data Files
4-1
File Header............................................................................................................... 4-1
Data ......................................................................................................................... 4-2
Diagnostics Header .................................................................................................. 4-4
Status Columns ......................................................................................................... 4-6
5 Theory and Equation Summary
5-1
Temperature Dependence of Absorption Line Strength ............................................. 5-1
Line Broadening Mechanisms ................................................................................... 5-2
Wavelength Modulation Spectroscopy ..................................................................... 5-4
6 Application Information
6-1
Computing Eddy Covariance Fluxes ......................................................................... 6-1
Concept of Spectroscopic Effects Overlaying Ideal Gas Law Effects .......................... 6-1
Formulation for the Propagation of Spectroscopic Effects into Flux Computation ...... 6-2
Values of Multipliers to Account for Spectroscopic Effects ........................................ 6-3
Flux Computation Algorithm..................................................................................... 6-5
Example of Flux Computation Using Real Field Data ................................................ 6-6
Bandwidth ................................................................................................................ 6-8
Determining Mirror Cleaner Settings......................................................................... 6-9
Determining Mirror Heater Settings ........................................................................ 6-10
Power Requirements............................................................................................... 6-11
Using a Secondary Washer Fluid Reservoir............................................................. 6-11
7 Advanced Operation
7-1
Diagnostics............................................................................................................... 7-1
Laser Temperature Control........................................................................................ 7-1
Opening the Laser Temperature Control Dialog ...................................................................... 7-2
Manual Line Lock Example ............................................................................................................ 7-3
Re-enabling Automatic Line Lock................................................................................................. 7-5
Maintenance ............................................................................................................ 7-6
Calibration................................................................................................................ 7-6
Changing the Internal Desiccant Bottle ..................................................................... 7-7
vii
Changing the Thermocouple ..................................................................................... 7-9
Changing the Fuse................................................................................................... 7-10
Networking ............................................................................................................ 7-10
Enabling IPv6 on Windows XP ................................................................................ 7-10
Finding your LI-7700’s IPv4 Address ....................................................................... 7-10
The LI-7700 Finder Application .............................................................................. 7-11
Communications Grammar .................................................................................... 7-17
Introduction ............................................................................................................ 7-17
LI-7700 Communications........................................................................................ 7-17
Element Descriptions .............................................................................................. 7-18
Grammar ................................................................................................................ 7-18
Configuration File Grammar.................................................................................... 7-24
Sending Commands ................................................................................................ 7-27
8 Appendices
8-1
Appendix A. Specifications....................................................................................... 8-1
LI-7700 Open Path CH4 Analyzer ............................................................................. 8-1
LI-7550 Analyzer Interface Unit ................................................................................ 8-1
Appendix B. Heating in the Optical Path .................................................................. 8-3
Appendix C. Troubleshooting ................................................................................... 8-7
Appendix D. Suppliers ............................................................................................. 8-9
Chemical Sources ..................................................................................................... 8-9
Calibration Gases.................................................................................................... 8-10
Turck® Cables ........................................................................................................ 8-11
Industrial Rated USB Flash Drives ........................................................................... 8-12
Mounting Hardware................................................................................................ 8-12
Warranty
viii
Welcome…
…and thank you for your purchase of the LI-7700 Open Path CH4 Analyzer. At LI-COR
it is our passion to provide robust, precise, and easy-to-use instruments for environmental
research and monitoring, and it is our sincere wish that the LI-7700 fills that role in your
application.
We welcome your comments, questions, and suggestions. Feel free to contact us at any
time.
LI-COR, Inc.
4647 Superior Street
P.O. Box 4425
Lincoln, Nebraska 68504-0425
Phone: 402-467-3576 FAX: 402-467-2819
Toll-free: 1-800-447-3576 (U.S. & Canada)
envsales@licor.com
www.licor.com
viii
Laser Safety Information
The Center for Devices and Radiological Health (CDRH) was established in October,
1982, by the U.S. Food and Drug Administration (FDA) to protect the public health in
the fields of medical devices and radiological health.
Manufacturers of products subject to performance standards under the Radiation Control
for Health and Safety Act of 1968 are required to furnish various reports to the CDRH.
The LI-7700 Open Path CH4 Analyzer is certified as a Class I laser product. This means
that hazardous laser radiation is not emitted from the instrument. All laser radiation
emitted is below the Class 1 Laser limits during any phase of
user operation. One laser emits near 1.6 microns and has a peak
power rating of 3 milliwatts.
The CDRH implemented regulations for laser products on
August 1, 1976 (CDRH radiation performance standard 21,
Code of Federal Regulations Chapter 1, Subchapter J). Compliance for products marketed in the United States is mandatory. The label that must be attached to laser products marketed
in the United States is located on the side of the lower housing
of the LI-7700 Open Path CH4 Analyzer (Figure 2), indicating
compliance with CDRH regulations.
WARNING: Use of controls
or adjustments or performance
of procedures other than those
specified herein may result in
hazardous radiation exposure.
Although the LI-7700 is a
Class 1 device and no hazardous radiation is emitted, refrain
from placing highly reflective
objects in the optical path and
never attempt to place one’s
head or eyes inside/near the laser path.
MODEL LI-7700
SR. NO. TG1-
LI-COR® inc
4647 SUPERIOR ST.
LINCOLN, NE 68504 U.S.A.
Made in U.S.A.
PATENTS PENDING
THIS DEVICE COMPLIES WITH PART 15 OF
THE FCC RULES. OPERATION IS SUBJECT
TO THE FOLLOWING TWO CONDITIONS:
(1) THIS DEVICE MAY NOT CAUSE HARMFUL
INTERFERENCE, AND (2) THIS DEVICE MUST
ACCEPT ANY INTERFERENCE RECEIVED,
INCLUDING INTERFERENCE THAT MAY
CAUSE UNDESIRED OPERATION.
CLASS 1 LASER PRODUCT
THIS PRODUCT COMPLIES WITH CDRH
RADIATION PERFORMANCE STANDARD
21 CFR CHAPTER 1 SUB-CHAPTER J.
Figure 1. CDRH regulation
compliance label.
MODEL LI-7700
SR. NO. TG1-
Laser
Safety
Label
LI-COR® inc
4647 SUPERIOR ST.
LINCOLN, NE 68504 U.S.A.
Made in U.S.A.
PATENTS PENDING
THIS DEVICE COMPLIES WITH PART 15 OF
THE FCC RULES. OPERATION IS SUBJECT
TO THE FOLLOWING TWO CONDITIONS:
(1) THIS DEVICE MAY NOT CAUSE HARMFUL
INTERFERENCE, AND (2) THIS DEVICE MUST
ACCEPT ANY INTERFERENCE RECEIVED,
INCLUDING INTERFERENCE THAT MAY
CAUSE UNDESIRED OPERATION.
CLASS 1 LASER PRODUCT
THIS PRODUCT COMPLIES WITH CDRH
RADIATION PERFORMANCE STANDARD
21 CFR CHAPTER 1 SUB-CHAPTER J.
Figure 2. Location of the
CDRH compliance label
on the LI-7700 Open
Path CH4 Analyzer.
ix
1
General Information
Overview of the LI-7700
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 to measure methane concentration at ambient pressure and
temperature. The LI-7700 is designed for deployment in extreme environments. 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 normal environmental extremes, including freezing weather (to -25 °C)
and rain without damage or calibration shifts.
Analog input channels to integrate sonic anemometer wind speed (U, V, W) and
sonic temperature (Ts) data with CH4 data.
•
•
Windows® software for setup and calibration.
Contact LI-COR if you have questions about the suitability of the LI-7700 in your application.
Figure 1-1 shows a schematic representation of the LI-7700 sensor head and the Herriott
cell. Except for the desiccant bottle and thermocouple, which are accessible externally,
there are no user-serviceable parts in the upper dome.
1-1
General Information
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 Analyzer
•
LI-7700 Open Path CH4 Analyzer – This is the sensor. It includes the laser, detector, sampling path, mirrors, heaters, and laser control electronics. The radiation shield
is attached to the upper housing prior to shipment.
Upper Housing
Reference
Sensor
CH4
Reference
Cell
Sample
Sensor
Folding Mirror
Prism
Beam Splitter
Herriot Cell Sample Path
Entrance/Exit
Aperature
Laser
Upper
Mirror
Lower
Mirror
Herriott Cell Sample Path
Mirror
Spin
Motor
Pressure
Transducer
Digital Signal
Processing
Electronics
Lower Housing
Figure 1-1. Representations of the LI-7700 upper housing (top left), the Herriott cell (center), and the
lower housing (lower right).
1-2
General Information
Spares Kit and Cables
•
Standard Spares Kit – This (p/n 9977-019) includes the cables, mounting hardware, extra parts that could easily be lost, and other essential components. Several
components listed below are attached to the instrument prior to shipping.
LI-7700 Spares Kit
Description
Ethernet Cable, Eurofast (0.3 M)
8-pin female to RJ45
Ethernet Cable, Eurofast (5 M)
8-pin male to 8-pin male
Power Cable, Eurofast (5 M), 5-pin female
5 Amp Fuse
Calibration Shroud
Solar Shield Assembly
Thermocouple Module Assembly
Mounting Post
Mounting Post Screws (1/4”-20, 5/8” long)
Washer Reservoir Assembly
Washer Power Cable
Spray Nozzle Assembly
Qty.
LI-COR Part No.
1
392-10107
1
1
1
1
1
1
1
2
1
1
1
392-10108
9975-030
438-09800
9977-033
9977-029
9977-038
9977-018
140-04320
7700-101
392-10211
9977-032
•
Ethernet Cables – There are two Ethernet cables provided: p/n 392-10108 is a 5 m
cable terminated on both ends with a male Turck connector; one end attaches to the
LI-7700 Ethernet output, while the end attaches to either the second 0.3 m Ethernet
adapter cable (p/n 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 – 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 terminal, blue and black are tied to a red lead, which connects to the
positive terminal.
1-3
General Information
1-4
•
Washer Assembly – The washer assembly includes a reservoir/pump unit, hose, and
the washer nozzle. The washer should be filled with windshield washer fluid with a
temperature rating suitable for the environment. For highly sensitive environments,
select an environmentally friendly solution.
•
Mounting Hardware – This is the hardware required to mount the LI-7700 on typical platforms. It includes the mounting post and two hex screws that fix the post to
the base of the LI-7700 analyzer.
•
Calibration Shroud – The calibration shroud is used to isolate the LI-7700 optical
path during calibration verification.
•
Computer Software – The CD includes the LI-7700 configuration/data logging
software. The software is compatible with Windows® XP/Vista/7 operating systems.
It is used to setup the LI-7700 and configure data logging.
•
Calibration Certificate – This documents the performance of your particular instrument when it left the factory. Keep this sheet for future reference.
General Information
7550-101 Auxiliary Sensor Interface (optional)
The 7550-101 is a convenient weatherproof junction for analog inputs on the LI-7700.
Detailed instructions for using the 7550-101 are provided beginning on page 2-16.
7550-101 Auxiliary Sensor Interface Spares Kit (optional) p/n 9977-019
Description
U-Bolt, 1/4 by 20
Hex Nuts
Quick Connect Plug
Strain Relief
Qty.
2
4
10
1
LI-COR Part No.
184-09842
163-00138
300-07393
198-01788
1-5
General Information
LI-7550 Analyzer Interface Unit (optional)
The LI-7550 enhances the functionality of the LI-7700 by providing onboard data logging
of eddy covariance data sets (CH4, U, V, W, Ts, and other variables), and enabling versatile
data output options. Detailed instructions for the LI-7550 are provided, beginning on
page 3-1. Contents of the LI-7550 standard spares kit are listed below:
LI-7550 Analyzer Interface Unit Spares Kit (optional)
Description
Control Unit Mounting Kit
RS-232 Cable
Power Cable
Analog Input/Output Cable
Ethernet Cable, Eurofast (5 M)
8-pin male to 8-pin male
Ethernet Cable, Eurofast (0.3 M)
8-pin female to RJ45
SDM Interface Cable
5 Amp Fuse
4GB USB Flash Drive
1-6
Qty.
LI-COR Part No.
1
1
1
1
9972-029
392-10268
9975-030
392-10109
1
392-10108
1
1
2
1
392-10107
392-10093
439-04214
7550-210
General Information
LI-7700 Components and Connections
1.
Radiation Shield – this is in place when the instrument is shipped, and
it should be left in place during normal operation, especially in highhumidity environments.
2.
Upper Housing – encloses the laser source, sensor, and laser control
electronics (see Figure 1-1).
3.
Fine-wire Thermocouple – this measures the ambient temperature
near the optical path. There may be a protective sleeve over the thermocouple, which will need to be removed prior to use.
4.
Upper Mirror – this is the upper mirror in the optical path. It can be
configured to maintain ambient temperatures in condensing conditions.
5.
Desiccant Cap – this seals the desiccant bottle. Only remove the desiccant cap to replace the internal chemical bottle (yearly, except in extremely humid environments).
6.
Sample Volume – the optical path is 0.5 m in length. The laser makes
60 passes in a Herriott cell pattern for a total path length of 30 m. The
laser beam is about 1.5 mm in diameter.
7.
Lower Mirror – the lower mirror features automated cleaning to reduce the need for maintenance and temperature controls to reduce
condensation on the mirror surface.
8.
Pressure Transducer – high-speed ambient pressure measurements.
The transducer is below the lower mirror.
9.
Lower Housing – houses the digital signal processing electronics and
spin motor.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Figure 1-2. The LI-7700
Open Path CH4 Analyzer.
10. Connection Panel – has indicator LEDs and weather-proof cable
connections.
1-7
General Information
The connection panel on the bottom of the analyzer includes the following components:
1.
Power In – provide a +10.5 to +30 VDC
3A power supply. The LI-7700 powers on
when a suitable power supply is connected. It always starts up with the most
recent configuration/settings.
2.
Fuse Housing – use only a 250V type F
5.0 Amp fuse. An extra fuse is included in
the spares kit (p/n438-09800).
1.
2.
3. 4.
Status LED – stays solid green when the
LI-7700 has finished startup.
6.
250V
F
5.0A
STATUS
WASHER
POWER
POWER
10-30V
3.
5.
5.0A
ANALOG
INPUT
ETHERNET
NETWORK
RESET
4.
Power LED – stays solid green when a
suitable power supply is connected.
5.
Analog Input – connector for the analog
input cable or the 7550-101 auxiliary interface unit (both optional) or a user-sup7.
8. 9.
10.
plied interface. It provides 4 analog input
channels (±5V) for U, V, W, and Ts data
Figure 1-3. The connection panel on the LI-7700.
from a sonic anemometer or any other
analog sensor, and three type E thermocouples. This data is output with the LI-7700 data stream.
6.
Washer Power – supplies power to the external washer unit accessory.
7.
Ethernet Connection – port for Ethernet communication.
8.
Ethernet LED – blinks at about 4 Hz when the Ethernet connection is active.
9.
Network Reset – depress this button to reset the network connection.
10. Mounting Points – the mounting post attaches to these threaded connections with the two ¼”-20
screws (5/8”), which are included.
1-8
General Information
Basic Setup
This section describes basic setup and operation of the LI-7700. Many of these steps are
described in more detail later in the manual.
1.
Attach the Mounting Post
If needed, attach the mounting post to the bottom of
the LI-7700 using two hex head bolts, as shown in
Figure 1-4. Tighten the bolts securely.
Figure 1-4. Attach the
mounting post as shown.
2.
Install the LI-7700 Computer Software
The LI-7700 software is compatible with Microsoft® Windows XP/Vista/ and 7
operating systems. Place the included software CD in your computer’s CD drive.
If the software does not start automatically, navigate to the CD directory on your
computer and double click on the Setup.exe file on the CD. Follow the onscreen installation instructions.
1-9
General Information
3.
Connect the Power Supply
Attach the yellow Turck cable (p/n 9975-030) to the Power connection on the LI-7700
connection panel. Align the notch in the cable with the notch in the power-in bulkhead
connector and push straight in. Tighten the knurled nut. Attach the red lead to the positive (+) terminal and the black lead to the negative (-) terminal of a power supply. This
could be a 10.5 to 30 VDC 3 Amp power adapter plugged into a 110 VAC wall outlet or
an automotive battery, for example. The LI-7700 powers on immediately after power is
supplied. It may take 30 seconds or more to boot up, and LEDs on the bottom of the
LI-7700 will begin flashing after the instrument completes start-up. Note: connecting the
power wires with improper polarity will blow the fuse.
Figure 1-5. Attach the power cable leads to a suitable power supply to turn on the LI-7700.
4.
Connect the Data Cable
Connect the 5 m Ethernet cable (p/n 392-10108) with Turck connectors to the Ethernet
connection on the LI-7700, then attach it to the 0.3 m Ethernet cable (p/n 392-10107).
Plug the RJ45 end of the cable into an Ethernet connection on your network, or plug it
directly into your computer’s Ethernet port.
Figure 1-6. Attach the 5 m Ethernet data cable as shown. Then attach 0.3 m cable and connect the RJ45
connector to a computer or network.
1-10
General Information
5.
Launch the Software and Connect to an LI-7700
Start the LI-7700 application: either double click the LI-7700 software icon on
your computer’s desktop or launch the software from your computer’s Start
menu. Click on the Connect button and a “Connect” dialog box will appear.
Select the “Ethernet” radio button, and locate your LI-7700 on the “Select
Instrument” drop-down menu. Click Connect.
Depending on the settings, methane concentration and other data should begin
streaming to main view.
If the instrument does not appear in the list, there are three possible solutions:
• First, be sure the instrument has finished starting up (30-60 seconds typically). It will not be visible on the network until it has finished start-up.
• Second, enable IPv6 on computers running Microsoft® Windows XP (page
7-10).
• Third, you can type in the IPv4 address directly into the “Select Instrument”
field. The IP address is listed on a piece of paper in your box.
1-11
General Information
Cleaning the Mirrors
There may be the appearance of “spots” on the mirror. These are normal, and are the result
of the manufacturing process. The “spots” are in the visible spectrum, but do not affect the
reflectance near 1.6 microns, which is where the LI-7700 operates. Therefore, the spots
should be of no concern.
The mirrors are extremely scratch resistant, however, the mirror surfaces should be treated
the same way you would treat the surface of an expensive lens. In general, refrain from applying a lot of pressure when cleaning a dry mirror. If the mirror is dusty, just wipe it with a
soft, clean moistened cloth. If a sticky substance, such as pollen, has built up on the mirror,
a mild soap or a commercial glass cleaner such as Windex® can be used.
Hint: Products such as Rain-X® can be applied to the lower mirror to help the glass shed water.
The washer reservoir uses standard over-the-counter windshield washer fluid (water is fine
if fouling of the mirror is minor). Cleaners that contain methyl alcohol (methanol) and
isopropyl alcohol are suitable. Refrain from using cleaners that contain powerful solvents
such as acetone. As a general rule, if the cleaner is safe for automotive finishes, it is probably safe to use in the LI-7700 washer reservoir.
1-12
2
Operation
Introduction to the LI-7700 Interface Software
Main View
After connecting to an LI-7700, the software window should look similar to the image
below. The graphs are set to auto-scale by default, so do not be alarmed by the appearance
of a “noisy” signal.
Tool Bar
Settings Bar
Charting Pages
2-1
Operation
The following items are displayed in the main view:
Tool Bar – the toolbar buttons activate the following options:
The file buttons are used to Create, Open, or Save a configuration file.
...or...
...or...
Click the Connect button (left) to establish communication
with an LI-7700. A Disconnect button (Ethernet on top, serial on bottom) will be visible when an instrument is connected. Click it to disconnect.
Inputs are configured with the Inputs button (left). A total of
eight inputs are available in this menu. Outputs (right) are
available when an LI-7550 Analyzer Interface Unit is used (see
Chapter 3).
Manual Controls are the basic configuration options for the
LI-7700, including settings for mirror heaters, mirror cleaning,
instrument name and address, instrument time settings, and
data output rate.
Waveforms can be turned on or off. The waveform is viewable
in the charting pages.
The Help button opens a menu with “About” and the built in
“Help” file. This provides access to a factory setup application
as well.
2-2
Operation
Settings Bar – four groups of settings and operation parameters are displayed in this portion of the main window:
Click on Configure… to change the charting settings.
Select the number of charts displayed on each tab (1 to
4) using the drop-down menu.
Click PC… to configure logging on a network or computer. Click USB… to configure logging to a removable
USB storage device (LI-7550 Analyzer Interface Unit
required).
Indicates status of the signal path, laser temperature
control, operating temperature setting, mirror heaters,
lower mirror spin motor, and operating temperature
range setting.
This provides the interface buttons for calibrating the instrument zero and span.
Note: Never implement new zero and span settings without following the calibration procedure described on page 7-6. Clicking the Factory Reset button will reset the instrument to the
factory original zero and span settings.
Charting Pages – Three pages (tabs) display the live data stream, and other data. Configure the data pages with the Configure button in the Charting frame described below. The
Diagnostics page displays the instrument waveform, which is turned on or off with the
“Waveform” button described above.
2-3
Operation
About the LI-7700 Dialog Boxes
The Manual Controls, Charting, Auxiliary Inputs, Outputs, PC Logging, and USB Logging dialogs include OK, Cancel, and Apply buttons. In these dialogs, click OK to implement changes and close the dialog, Cancel to close the dialog without implementing
changes, or Apply to implement changes and keep the dialog open.
Charting
Two charting pages are visible, and each of these pages can display up to four charts. The
charting pages are the two tabs called “Data Page 1” and “Data Page 2” in the main view.
To configure the charts, click the Configure button in the Charting frame of the main
view.
2-4
Operation
The Configure Graphs dialog box presents options for selecting which variables are displayed, automatic/manual graph scaling, label precision, scroll settings, and X-axis configuration. Click Apply to implement any changes.
About charting
In the Configure Graphs dialog you can turn automatic scaling “on” or “off” with the
Auto-scale check box. When automatic scaling is on, the software retains a record of the
maximum and minimum values encountered and scales the graph accordingly. If you click
the Clear Charts button in the main window the chart scaling will reset.
Automatic scaling can be turned on or off simply by double clicking on a graph in the
main view. When automatic scaling is on, the graph will have a frame. When automatic
scaling is off, the frame will be open, as shown below.
Automatic scaling is “Off”, indicated by the open frame.
Automatic scaling is “On”, indicated by the closed frame.
2-5
Operation
Configuring PC/Network Data Logging
2-6
1.
Click on the PC… button in the Logging frame of the main view.
2.
Select the variables that you’d like to log (see section 4 for more details) and choose a
directory that the files will be written to. Click Apply.
3.
Choose whether to log the “Status” record, and whether it will be part of the data file
or a separate log file. Choose how often to split the log files (from 15 minutes to 24
hours). Click Apply.
4.
Click the button under “Output Rate” to open the manual controls window. Here
you can change the output bandwidth. Click Apply.
Operation
5.
The Start button will be available (no longer greyed out). You can click Start in this
window to begin logging immediately or you can activate logging from the main view.
Click OK to return to the main view. Here, the Start button (in the Logging>PC…
frame) will be active. You can start and stop logging from the Main View.
When actively logging, the control settings will be grayed out, a green indicator will appear
in the main view, and the Stop button will become active.
About Splitting Files
To help limit the size of individual files, log files can be split on a periodic basis. The
method of splitting is based on the instrument clock, rather than on elapsed time. As such,
the file will split when the instrument time crosses a user-specified interval. For example, if
the application is set to split the log file every 15 minutes and the logging session starts at
11:25, the first split will occur at 11:30. The second split will occur at 11:45, and so on.
About Logging Status Columns
Status data (described on page 4-6) can be logged to the data file, logged to a separate file,
or not logged. To log status data, check the “Log Status Columns To:” check box, then select “Separate File” or “Log File”. Status data are logged at 2 Hz. If you select “Log File”,
the status data will be interspersed with the data record.
2-7
Operation
Instrument Settings/Setup
The following sections describe the operating temperature range setting, mirror cleaner
settings and mirror heater settings. More information about determining these settings is
provided on pages 6-5 (spin motor and cleaner settings) and 6-6 (heater settings).
Operating Temperature Range
Two operating temperature ranges are available: -25 °C to 25 °C (cool) and 0 °C to 50 °C
(warm). Select the temperature range setting that reflects the expected temperatures in the
environment where you plan to deploy the LI-7700. If the wrong temperature setting is
selected, the instrument may be unable to maintain the required temperature in the internal controls, and thus lose line lock.
The current setting is indicated by either a blue (cool) or yellow (warm) “light” indicator
in the main window.
Blue indicates
the “Cool”
temperature
setting
Yellow indicates
the “Warm”
temperature
setting
To change the setting, click on the yellow or blue indicator “light”. This will open the dialog shown below, in which you can change the setting.
After changing the temperature range setting, it may take up to 5 or 10 minutes for the
block temperature to adjust before the instrument returns to normal operation. Look at
the Diagnostics Page 1 tab and observe the Block Temperature setting. The “Actual” and
“Set” temperatures should be within about 0.5 °C after the temperature adjusts.
If the instrument is unable to achieve line lock once the new operating temperature range
is established, click the “Initiate Automatic Line lock” button. This will command the instrument to re-try the automatic line lock routine.
After changing the operating temperature range re-zero and span the analyzer using
high-quality calibration gases.
2-8
Operation
Manual Controls
When settings in the Manual Controls dialog are changed, they are implemented to
whichever LI-7700 is connected to the interface. After changing the configuration, you
could unplug the instrument and deploy it in the field. When it is connected to a power
supply it will operate with the previously defined settings. Configurations can be saved and
implemented from a file too (see page 2-15).
To change the settings:
1.
Click on the Manual Controls button (the “gears”) to open the Manual Controls
dialog box.
2.
The dialog box displays controls for the following settings: mirror temperature controls (page 2-12), mirror cleaner settings (page 2-10), instrument time and date (page
2-14), time zone, IP address, and output rate (Hz).
3.
Any changes will be implemented immediately to the connected LI-7700 (after clicking Apply or OK). These settings will be saved in the LI-7700.
Mirror
heater
controls
Instrument
name and
IP address
Lower
mirror
cleaner
settings
Instrument
time
settings
Data
output
rate
settings
Detailed descriptions of these settings are provided in the following pages.
2-9
Operation
Configuring the Spin Motor Control
The mirror washer unit settings are designed to provide a great deal of flexibility. As a result, some settings are unsuitable for certain environments. The use of improper settings
may result in missing data or excessive power consumption, so choose carefully.
There are two components involved
with the self-cleaning mirror – the
1.
mirror spin motor, which is in the
2.
lower housing (see page 1-7), and the
washer assembly (see page 1-5).
3.
During the cleaning cycle, the pump
and spin motor run simultaneously
4.
for the first part of the duration, and
the spin motor alone runs for the last 5.
10 seconds of the duration. This provides two benefits: any drops that fall
from the nozzle will be cleared by the
spinning mirror, and it allows the mirror to spin without using washer fluid. Spin Motor
Controls are in the Manual Controls Window. They are described below:
1.
The Control Setting can be On, Off, or Automatic. Change the setting to Automatic to
enable the remaining controls.
2.
Signal Strength Threshold refers to a threshold (Recieved Signal Strength Indicator, or
RSSI). If the laser signal strength falls below this threshold, the mirror spin motor and
washer pump will activate according to the other settings.
3.
Start Time and Stop Time specify the period of the day in which the mirror cleaner can
activate. Set both to 00:00 to allow mirror cleaning for 24 hours a day.
4.
Repeat Check Every: sets the repeat interval at which the instrument re-checks the RSSI
value. If the RSSI value is below the Signal Strength Threshold (#2), then it will repeat the
cleaning cycle according to the remaining parameters.
5.
Spray Duration: can be set from 0 to 110 seconds. A setting of “0” will result in no spray,
but the mirror will still spin for 10 seconds if the RSSI is below the signal strength threshold.
With the settings shown above, if the signal strength were to fall below 20%, the LI-7700
would initiate a 20 second cleaning cycle starting at 4:00 am (04:00). If the first cleaning
2-10
Operation
cycle failed to raise the signal strength to above 20%, it would repeat every hour until 8:00
pm (20:00) or until the signal strength goes above 20%.
Note: The use of a low signal strength threshold (e.g. ~10%) may result in “noisier” data as
the signal strength gets lower. Check your data to observe this, and choose a setting that is
within the noise tolerance that you prefer.
This figure depicts the Spin Motor Control settings shown below:
01:00 02:00 03:00 04:00 05:00 06:00 07:00 08:00 09:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 24:00
Time Window (Start at 04:00, Stop at 20:00)
Start Time: 04:00 (Beginning of Time Window)
Stop Time: 20:00 (End of Time Window)
Repeat Check Every: 01:00 (Vertical lines on each
hour marker, at which point the LI-7700
rechecks the RSSI value)
Spray Duration: 10 seconds
Spin Motor runs for 20 seconds
The Pump runs for 10 seconds
If the RSSI value is below the “Signal Strength Threshold”, a cleaning cycle will be initiated at the “Repeat
Check Every” setting.
The pump always runs for 10 seconds less than the spin motor. Set the “Spray Duration” to 0 seconds to spin
the mirror for 10 seconds without spraying any fluid.
2-11
Operation
Configuring Mirror Heater Control
Mirror heaters serve to keep the mirrors free of condensation and frost. They are configured in the Manual Controls Window in the heater control frame. See page 6-6 for
information on selecting settings, page 6-7 to learn about power requirements for the heaters, and page 8-3 for a discussion on the effects of heating in the optical path.
1.
Heater Control Settings can be On, Off, or Automatic. Setting to On enables
power and ambient offsets for the upper mirror and power settings for the lower
mirror. The Automatic setting enables all possible controls.
2.
Power Setting defines how much
power is delivered to the mirrors.
In environments with light condensation, power settings of 10%
or less should be adequate. Settings
near 100% should be reserved for
circumstances in which severe ice
buildup is expected.
3.
Ambient Offset defines how far
above the ambient temperature (as
measured by the optical path
thermocouple) the mirror is heated
to. This setting applies only to the
upper mirror.
1.
2.
3.
5.
1.
2.
4.
5.
4.
The Signal Strength Threshold (RSSI) for the lower mirror heater. It is enabled
when the Control Setting is set to Automatic.
5.
Start and Stop Times specify when the mirror heaters are on. These are available only
when the Control Settings are Automatic.
With the settings shown above, the LI-7700 will deliver 7% of the maximum possible
heater power, as needed to keep the mirror 2 °C above ambient temperatures between 6:00
pm (18:00) and 6:00 am (06:00) to the upper mirror. The lower mirror will be heated
with 7% of maximum possible power, only if the signal strength is below 30%, between
6:00 pm (18:00) and 6:00 am (06:00).
To save power, set the mirror heaters to operate when condensation is likely. Set them to
heat as little as is needed to keep the mirrors free of condensation. Higher heater settings
require more power.
2-12
Operation
About LI-7700 Time Keeping
Three aspects to time keeping in the LI-7700 are described here – the basis for the actual
time (Unix, aka POSIX), the protocol for determining the actual time (Precision Time
Protocol), and user-settable time zone and time.
Since the LI-7700 is a network-based instrument, it is possible for multiple users to log
data from a single instrument over multiple TCP/IP connections. Consequently, the instrument uses Coordinated Universal Time (UTC) for its onboard timekeeping tasks. As
such, the default time stamp will be UTC based, but local time can be set as well.
The LI-7700 internal clock uses Unix time as a standard. Simply put, this is seconds
elapsed since the Unix Epoch of 00:00 Coordinated Universal Time (UTC) Jan. 1, 1970
(or 1970-01-01T00:00:00Z ISO 8601). For example, the time stamp 1262884605 translates to 01/07/2010 at 05:16:45 UTC. The date and time are converted into a conventional display format (YYYY-MM-DD; HH:MM:SS), and adjusted based on the time
zone settings that you select.
The LI-7700 uses the Precision Time Protocol (PTP) time keeping system. PTP is a high
precision time synchronization protocol for networked measurement and control systems.
Devices controlled with PTP can maintain accuracy in the sub-microsecond range with a
sufficiently accurate master clock. PTP is defined in the IEEE 1588-2002 and 1588-2008
standards, officially entitled “Standards for Precision Clock Synchronization Protocol for
Networked Measurement and Control Systems”. A detailed summary of IEEE-1588 is
available at www.ieee1588.com. Full documentation is available for purchase from the
Institute of Electrical and Electronics Engineers (IEEE) at www.ieee.org.
The basic principle behind the PTP is that the best time keeping can be accomplished with
multiple networked devices by synchronizing all the device clocks to the most precise clock
on the network. Each clock on the network has a rating that indicates its relative accuracy.
The IEEE 1588 protocol specifies the use of a Best Master Clock algorithm to determine
which clock on the network is the most accurate. On a network, the most accurate clock
becomes the master clock and all other clocks sync to the master clock.
The software implementation of PTP in the LI-7700, which uses the instrument clock
provides accuracy in the 10 microsecond range. Implementation of PTP is most important
when the LI-7700 is used in combination with the LI-7550 Analyzer Interface Unit or
other network-based sensors. Three time-keeping settings are available in the “Manual
Controls” dialog. They are described below:
2-13
Operation
Automatic: The LI-7700 searches the network and syncs to the most accurate clock using
the Best Master Clock algorithm. The LI-7700 should use this setting in most circumstances.
Preferred: The LI-7700 uses its own internal clock unless it finds a better clock on the
network.
Slave: The LI-7700 syncs to another clock. It will search the network and synchronize to
the best clock. The LI-7550 should use this setting in most circumstances.
Setting the Time
The LI-7700 is shipped with
the time set at the factory. To
set your local time:
1.
Connect to the LI-7700.
2.
Open the Manual
Controls dialog box
(click the “gears”).
3.
Set the PTP: field to
“automatic”.
4.
Select the desired time zone.
5.
Click Apply or OK.
You may also adjust the time if desired, but these adjustments apply to the Unix time
stamp as well. Therefore, be sure that the instrument time and date match your local time
and date and that you have set the correct time zone.
The time stamp in each file header shows the instrument time and time zone. The time
stamp associated with each data record will always include Unix time, but you can choose
to output the instrument time and date as well. Unix time is in two fields: seconds and
nanoseconds. Conventional time includes the date and time resolved to seconds. The
nanoseconds field can be used to resolve sub-second time stamps.
2-14
Operation
Creating an Instrument Configuration File
The following procedure describes how to create a new instrument configuration file. See
page 7-24 for more information on configuration files.
1.
Launch the LI-7700 software.
2.
Be sure the LI-7700 software is not connected to an LI-7700. If needed, click the
Disconnect button.
3.
Click on the Manual Controls button. Set the controls as desired. Click OK or
Apply then OK to set the new configuration. Repeat this for the Auxiliary Inputs and
LI-7550 Outputs if desired.
4.
Click the Save button. A Save As dialog box will open. You can select a directory
anywhere on your computer or network. The file will have a “.l77” extension.
Implementing a Configuration File
The following procedure describes how to implement a configuration file.
1.
Be sure the LI-7700 is powered “on” and connected to your computer or network
with the Ethernet connection.
2.
Launch the LI-7700 software and connect with the LI-7700.
3.
Click on the Open button. The “Open” dialog box will appear. Navigate to the directory that has the “.l77” configuration file.
4.
Select the file and click Open.
5.
A warning dialog will appear. Click Yes to implement the configuration file. The
LI-7700 can now be disconnected from your computer and the power supply. It will
use this configuration when it is started the next time.
Note: when you connect to an LI-7700, at the top of the “Connect” dialog box, there is a “Use
Instrument Configuration” check box. Be sure that this is checked in order to prevent overwriting the current LI-7700 configuration.
2-15
Operation
LI-7700 Analog Inputs
The LI-7700 and the LI-7550 each provide 4 analog input channels. These can by used
with either the 7550-101 Auxiliary Sensor Interface (see below) or the Analog
Input/Output Cable (p/n 392-10109). The 7550-101 is a weatherproof terminal strip
that provides sealed electrical connections. The Analog Input/Output Cable terminates
with bare leads on one end and a Turck connection on the other. It is included with the
LI-7550 Analyzer Interface Unit, or available as an accessory.
The 7550-101 Auxiliary Sensor Interface and the Analog Input/Output Cable can be used
in any of the three configurations shown in Figure 2-1, but the 3 type E thermocouple
connections (Option 1) are only available through the 7550-101 unless a user-supplied thermistor is used to measure the temperature of the thermocouple reference junction. Input configurations are described on page 2-21.
The 7550-101 Auxiliary Sensor Interface the Analog Input/Output Cable can be used to
connect analog data sources to the LI-7700 (Option 1) or the LI-7550 Analyzer Interface
Unit (Option 2). It can also be configured to distribute the 6 analog outputs of the
LI-7550 (Option 3).
Option 1
Option 2
For use with:
Analyzer
CO 2/H 2O
• LI-7200
CO 2/H 2O
er
• LI-7500A
CH 4 Analyz
• LI-7700
LI-7700:
4 analog inputs
• single ended
• ±5 V
• 16 bit
3 type E thermocouple inputs
• (7550-101 req’d)
5V source
LI-7550:
4 analog inputs
• differential
• ±5 V
• 16 bit
5V source
Option 3
For use with:
Analyzer
CO 2/H 2O
• LI-7200
CO 2/H 2O
er
• LI-7500A
CH 4 Analyz
• LI-7700
LI-7550:
6 analog outputs
• user-scalable
• single ended
• ±5 V
• 16 bit
Figure 2-1. The 7550-101 can function as a weather-proof terminal strip for the LI-7700 Auxiliary inputs, the LI-7550 Auxiliary inputs, or the LI-7550 Digital-to-Analog converter outputs.
2-16
Operation
Here we describe how to use the 7550-101 or the Analog Input/Output Cable as shown
in Option 1 above. Options 2 and 3 are described beginning on page 3-9. Note that
Options 1, 2, and 3 can be used together in any combination.
Auxiliary Sensor Interface Terminals (Option 1)
Loosen the four Philips head screws in each corner of the Auxiliary Interface Box module
and remove the top cover. The interior of the interface is shown in Figure 2-2 below.
360-09333 Rev 2
Made in USA
www.licor.com
LI-7700
LK1
LI-7550
P2
NC
GND
+5V
GND
GND
RESERVED
+5V
AUX4RESERVED
PLUGS
GND
GND
NC
AUX4+
T3
T_REF
GND
READY
AUX3T2
GND
DAC6
AUX3+
T1
GND
DAC5
GND
GND
DAC4
AUX2AUX4
DAC3
AUX2+
AUX3
GND
GND
GND
DAC2
AUX1AUX2
DAC1
A OUT
AUX1+
AUX1
LI-7550
A IN
LI-7700
ANALOG IN
P1
There is a small jumper located at position LK1; when using the 7550-101 with the
LI-7700 (Option 1), position the jumper over the 2 pins nearest the LI-7700 label (the
lower two pins in Figure 2-2 below). Position it over the 2 pins nearest the LI-7550 label
any time the 7550-101 is connected directly to an LI-7550 Analyzer Interface Unit.
PLUGS
Figure 2-2. Schematic diagram of interior of Auxiliary Sensor Interface.
There are two terminal strips, with connections as follow:
GND
+5V
RESERVED
RESERVED
T_REF
T3
T2
T1
GND
AUX4
AUX3
GND
AUX2
AUX1
When Used for Analog Inputs (LI-7700)
Figure 2-3. Terminal connections for analog inputs (Option 1).
2-17
Operation
The terminal positions are numbered and configured as follows, reading from left to right:
Table 2-1. Terminal assignments for the 7550-101 and wire colors for the Analog Input/Output cable
when using the LI-7700 analog inputs (Option 1).
Option 1
7550-101 Auxiliary
Analog In/Out Cable
Sensor Interface
(p/n 392-10109)
Description
Terminal Input
Wire Color
Pin
1
AUX1
Auxiliary Input 1 Signal
White
Pin 1
2
AUX2
Auxiliary Input 2 Signal
Brown
Pin 2
3
GND
Ground
Tan
Pin 10
4
AUX3
Auxiliary Input 3 Signal
Green
Pin 3
5
AUX4
Auxiliary Input 4 Signal
Yellow
Pin 4
6
GND
Ground
Tan
Pin 10
7
T1
Thermocouple 1 Signal1
Gray
Pin 5
1
8
T2
Thermocouple 2 Signal
Pink
Pin 6
9
T3
Thermocouple 3 Signal1
Blue
Pin 7
1
10
T_REF
Thermocouple Reference
Black
Pin 11
11
Reserved
Thermistor Input
Red
Pin 8
12
Reserved
Thermistor Reference
Violet
Pin12
13
+5V
+5V Supply
Orange
Pin 9
14
GND
Ground
Tan
Pin 10
1
Using the thermocouple channels (T1 to T3) requires measurement of the reference junction temperature. This is accomplished with an internal thermistor in the
7550-101. If you are using the Analog Input/Output Cable with the LI-7700 and
you wish to use channels T1 to T3, a user-supplied thermistor is required for measuring the reference junction temperature of the thermocouples.
2-18
Operation
Connecting Sensors to the Auxiliary Sensor Interface
There are 5 strain relief “gland” type plugs on the Auxiliary Sensor Interface top cover,
through which the sensor wires pass, after which the wires are connected to the appropriate screw terminals. To attach your sensor(s) to the Auxiliary Sensor Interface, follow
these steps:
1.
Remove the #1 Philips head screws from each of the four corners of the Auxiliary Sensor Interface and remove the top cover.
2.
Remove the cap from any of the 5 gland plugs by turning the cap counterclockwise.
3.
Pass the wires through the top of the plug cap first, and then through the gland plug.
Attach the plug cap slightly, but don’t tighten it yet.
4.
Use a small flathead screwdriver to loosen the appropriate screw terminal and insert
the wire lead into the terminal. Tighten the screw terminal to secure the wire. Make a
note of which plug the wires are passing through and to which terminal channels the
wires are connected. This will be needed later when you configure the sensor coefficients in the software.
2-19
Operation
5.
Pull gently on the wires to remove slack from inside the interface. Attach additional
sensor wires to the appropriate terminals.
6.
When you have finished installing all of your sensors, re-attach the interface top cover
and tighten the gland plug caps.
7.
Attach the Auxiliary Sensor Interface cable connector to the Analog Input connector
on the LI-7700 connection panel.
Note: There are 5 EPDM type plugs in the interface box. These can be inserted into unused
gland plugs on the Auxiliary Sensor Interface. The plugs prevent foreign materials (e.g. water,
insects, dirt) from entering the interface box. Remove the top cover and insert the narrow end
of the plug through the back of the gland plug(s) and tighten the plug cap(s) (as shown in plug
A above). The plugs should always be used in any gland plug that does not have a wire.
There is also a length of Santoprene® tubing in the Auxiliary Sensor Interface spares kit. This
tubing can be cut to length and placed around small gauge wires that may not be able to be
tightened sufficiently with the gland plugs. It can also be used for oddly shaped wires that can
be difficult to seal with the gland plug caps.
Thermocouple Inputs
The thermocouple inputs are designed to work with Type E thermocouples (chromel vs.
constantan). The positive (+) thermocouple wire (chromel, purple insulation) should be
connected to T1, T2, or T3. The negative (-) thermocouple wire (constantan, red insulation) should be connected to the T_REF. All three channels share a common connection
T_REF. The range of thermocouple temperature measurements is ±20 °C from the reference temperature inside the Auxiliary Sensor Interface.
Thermocouple readings can be influenced by rapid changes to the temperature or by heat
loads to the auxiliary sensor interface. To avoid risk of these issues, shield the auxiliary sen-
2-20
Operation
sor interface from direct sun and/or thermally insulate the apparatus. A simple solution is
to wrap the Auxiliary Sensor Interface with aluminum foil.
Configuring Auxiliary Sensors (LI-7700)
Analog inputs are configured from
the “Configure Auxiliary Inputs”
dialog box. Auxiliary inputs 1
through 4 are used with LI-7700 inputs (see Option 1, page 2-17). They
are configured with the top four tabs
in the Configure Auxiliary Inputs
dialog box. One of two mathematical
conversions can be applied to the input voltages: 1) a third order polynomial or 2) a Steinhart equation
(for computing temperature in °C
from a thermistor).
The polynomial can be used to scale
inputs from a variety of sensors, such
as thermistors or sonic anemometers.
Below are several examples demonstrating ways that the polynomial can
be used:
y=a0 + a1*x + a2*x2 + a3*x3
Example 1: The figure below shows
how to wire and configure a thermistor for auxiliary inputs 1 to 4 (and 5
through 8).
+5 Vref
Vaux
Gnd
Rbias
Rtherm
a0=Rbias
a1 = A
a2 = B
a3 = C
}
Steinhart
Coefficients
Example 2: These settings convert analog output voltage from a CSAT3 sonic anemometer (Campbell ® Scientific, Inc.) to wind speed (m/s). In this example we demonstrate the
“high range” (horizontal wind speeds up to ±65.563 m/s, vertical wind speeds up to
±8.192 m/s) scaled to ±5V. The median of the high (+65.563) and low (-65.563) values of
the measurement range is the offset (0), and is entered in the a0 field. The slope is found
2-21
Operation
by dividing the wind speed measurement range by the total voltage range: 131.072 m s-1/
10V = 13.1072 m s-1 v-1. If the leads for ux, and uy are connected to Aux1 and Aux2 inputs,
set the Aux1 and Aux2 polynomial values for a1 to 13.1072. a0, a2, and a3 = 0.
Mutlipliers for uz are found similarly. With a measurement range of ±8.192 m s-1, 16.384
m s-1 /10V = 1.6384 m s-1 v-1. Using Aux3 to log uz, a1=1.6384; a0, a2, and a3 = 0.
Using Aux4 to log the speed of sound, the terms a1=340 (offset), a2=6.5536 (slope) are
given in the CSAT3 Instruction Manual. This is shown below. Refer to the CSAT3
Instruction Manual for more information.
LI-7700 Aux Channel
Polynomial Values a0
(set in LI-7700
a1
software)
a2
a3
Variable Logged
Units
Aux1 Aux2 Aux3
0
0
0
13.1072 13.1072 1.6384
0
0
0
0
0
0
Ux
Uy
Uz
Windspeed (m/s)
Aux4
340
6.5536
0
0
Speed of Sound
(m/s)
Example 3: This example describes how to convert analog signals from a Gill WindMaster
or WindMaster Pro sonic anemometer in the ±50 m s-1 wind speed range (speed of sound
range of 300-370 m s-1), with analog outputs scaled to ±5V.
The median of the low (-50) and high (+50) values of the measurement range is the offset
(0), and is entered in the a0 field. The voltage output range between -5 to +5V is 10V. To
find the slope, divide the measurement range by the voltage range (100/10=10). This value
is the slope and is entered in the a1 fields for Aux 1, 2, and 3.
For speed of sound, the median of the low (300) and high (370) values of the measurement range is the offset (335), and is entered in the a0 field for Aux4. To find the slope,
divide the measurement range by the voltage range (70/10=7). This is entered in the a1
field for Aux4.
LI-7700 Aux Channel
Polynomial Values a0
(set in LI-7700
a1
software)
a2
a3
Variable Logged
Units
Aux1 Aux2 Aux3
0
0
0
10
10
10
0
0
0
0
0
0
U
V
W
Windspeed (m/s)
Aux4
335
7.0
0
0
Speed of Sound
(m/s)
Alternatively, you could compute °C rather than SOS with the following: Ts range= -40
°C to 70 °C. The median (15) is entered in a0 for Aux4. The measurement range (|-40 70|=110) divided by the voltage range (110 m s-1/10V=11m s-1 v-1) is the slope and is entered in a1 for Aux4. Refer to the WindMaster/Pro User Manual for more information.
2-22
Operation
Deploying the LI-7700
Mounting the LI-7700
For field deployments, the LI-7700 must be firmly attached to a stable, secure instrument
platform. For eddy covariance applications, be sure that the instrument is deployed in accordance to the guidelines set forth by the scientific community for eddy covariance data
collection. For example, mounting the LI-7700 too close to the canopy may result in sampling in the roughness sub-layer, which is not representative of the study site. A vertical
mounting orientation provides 360° acceptance for wind direction, and this is the recommended orientation. However it is oriented, the LI-7700 should be placed as close to the
sonic anemometer as practical without blocking the airflow through the anemometer.
The LI-7700 mounting post is designed to fit securely into a 1” NU-Rail tee or cross fitting, similar to those used in many micrometeorological stations.
To mount the LI-7700 on a weather station using a NU-Rail adapter:
1.
Position the NU-Rail adapter on the spar in the approximate position. It should
mount so the LI-7700 is correctly positioned in relation to the sonic anemometer and
other instruments. Securely tighten the hex-screws
on the NU-Rail adapter.
2.
If the LI-7700 mounting post is not in place, attach
it to the bottom of the LI-7700 using the two include hex screws.
3.
Position the LI-7700 in the NU-Rail adapter and
tighten the hex-screws. Reposition the NU-Rail
adapter as needed. Be sure to securely tighten the
adapter screws. Attach the power and data cables.
Route the cables and hoses so that they are not
hanging from the LI-7700. Preferably, secure them
to the tower with wire ties.
4.
Connect the Ethernet cable from the LI-7700 to a data storage device.
5.
Connect the power cable to a suitable power supply.
2-23
Operation
Positioning the LI-7700
The LI-7700 is designed to fit easily into existing or new eddy covariance flux stations. As
such, there are numerous factors to take into account when deploying the LI-7700. Addressing these concerns appropriately is critical to minimizing required frequency response
corrections. Here we address two of these: instrument height above the canopy and
proximity to the sonic anemometer.
High above the plant canopy:
For most applications, the LI-7700 and other
sensors should never be within the canopy
roughness sub-layer, as that may violate the assumptions of the eddy covariance flux method.
The minimum recommended height above the
canopy is 1.0 to 1.5 m or more, but this will
vary depending on surface roughness and other
factors.
As with all instrumentation in an eddy covariance flux system, the closer to the canopy, the
closer the instruments must be to each other to
minimize frequency response corrections for
sensor separation. For deployments high above
the canopy, the LI-7700 should still be as close
as practical to the sonic anemometer, but larger
vertical separations are now more acceptable.
For example, at heights of 40 meters above the
canopy, the anemometer sample path can be
above the LI-7700 entirely. Note: never put
scalar measurements (e.g., the LI-7700) above
the sonic anemometer, as it may lead to errors
and require difficult-to-predict corrections.
For near surface deployments, the LI-7700
should be 10-30 cm horizontally from the anemometer, and they should have a minimal vertical separation.
2-24
Horizontal separation
of 0 cm is possible
Vertical
separation
is more
tolerable
Close to the plant canopy:
Horizontal separation
10-30 cm
Vertical
separation
0 cm
Operation
Grounding
The power supply, Ethernet, and analog inputs are all electrically isolated from each other
and from the internal circuitry. There also are protection clamps in the form of spark gaps
on the isolated circuits to the instrument chassis. For lightning protection, make sure the
mounting structure for the instrument is electrically grounded, or run an independent
bonding wire from the instrument mount to the earth.
Mounting the Auxiliary Sensor Interface
The Auxiliary Sensor Interface has an attached mounting plate that can be used to attach
the interface to a 1” to 1½” diameter post. Two U-bolts and four nuts are included in the
7550-101 spares kit. These can be used to attach the Auxiliary Sensor Interface as shown
below in Figure 2-4. It can be mounted vertically or horizontally. If you do not want to use
the attached mounting plate, remove the top cover of the box and remove the two screws
(in opposite corners) that secure the box to the bracket. You can then secure the interface
using wire, cable ties, or other methods of your choosing.
7550-101 Auxiliary Sensor Interface
Top View
Side View
Auxiliary
Sensor
Interface
Nut
Mounting Bracket
Post
U-bolt
Figure 2-4. Mounting the 7550-101 Auxiliary Sensor Interface.
2-25
Operation
Attaching the Mirror Cleaner/Washer Assembly
Follow the steps below to attach the mirror cleaner.
1.
Attach the spray nozzle assembly (p/n 9977-032) to a spar on the LI-7700, as shown
below. It snaps into place.
2.
Attach the “Quick Connect” hose fitting on the nozzle/hose assembly to the fitting
on the washer assembly (p/n 7700-101).
3.
Connect the washer motor power cable (p/n 392-10211) to the washer power
connection on the LI-7700 connection panel. Now the washer will run based on the
settings in the Manual Controls dialog box.
4.
Fill the washer with regular automotive windshield washer fluid or an environmentally friendly alternative. If there is risk of freezing temperatures, select a washer fluid
that will not freeze.
5.
To verify spin motor operation, set the
Control Setting to “On” and click
“Apply” in the Manual Controls window. After observing operation of the
spin motor (the pump will not run, see
below), set the Control Setting to
“Off” and click “Apply”.
Note: While you may use the “On” setting to
manually spin the mirror, the fluid pump
will not power up. It is controlled exclusively
by the time scheduling algorithm. If you wish
to test the connections and ensure that the
pump will power up, set the Spin Motor
Control to “Automatic” with a time window
that will allow the instrument to power up
the pump.
Spray Nozzle
Assembly
(p/n 9977-032)
Washer Motor
Power Cable
(p/n 392-10211)
To Washer
Reservoir
Assembly
(p/n 7700-101)
Figure 2-5. Washer Nozzle assembly and washer
power cable connections.
2-26
Operation
Mounting the Washer Reservoir
Two brackets (included) can be used to mount the 7700-101 Washer Reservoir to a tripod
or other post using bolts or U-bolts. The hardware required for this is included. Alternatively, the four holes in the corners of the box can be used to attach the box directly to a
flat surface. Mounting the 7700-101 is identical to the LI-7550 (see page 3-22).
The mounting brackets are designed to accommodate a square or circular mounting post
of up to 1.25" in width (diameter). Use a 3/16" hex key to attach the mounting brackets to
the Analyzer Interface Unit using the 4 socket head screws (p/n 140-02654). The U-bolts
can then be inserted through the holes in the mounting bracket, and tightened around the
post.
Additional Considerations:
1.
The cables and hose are 5 meters long. The washer reservoir must be within 5 meters
of the LI-7700. The pump is powerful enough to lift the washer fluid 5 meters, but attempts to lengthen the washer hose will result in reduced fluid pressure, which will affect the performance of the pump and mirror cleaner.
2.
An additional reservoir can be used with the 7700. This might be necessary in circumstances in which the washer fluid may be used quickly. See page 6-7 for more information.
The following schematic shows a basic LI-7700 configuration with the washer reservoir,
analog input cable, and a sonic anemometer. In this configuration, power is supplied to the
sonic anemometer and the LI-7700. Data are output through Ethernet to a suitable data
storage device.
2-27
Operation
Washer
Nozzle
Analog Input Cable
or
7550-101
Washer
Hose
Washer
Power Cable
Washer
Reservoir
Ethernet output
Power In:
(includes CH4, U, V,
W, Ts, ancillary, and
diagnostic data)
Sonic Anemometer
LI-7700: 10.5 to 30 VDC, 3 amps
Figure 2-6. A typical field deployment of the LI-7700 and accessories in an eddy covariance
application.
2-28
3 Operation with the LI-7550 Analyzer
Interface Unit
The LI-7550 is available as an accessory for the LI-7700 Open Path CH 4 Analyzer. It is a
weather resistant case that houses Digital Signal Processing electronics. When used with
the LI-7700 it provides:
•
•
•
•
•
Logging of eddy covariance data sets to a removable USB storage device
6 high-speed, scalable Digital-to-Analog converters (16 bit, ±5V)
RS-232 serial output
Ethernet communication/data transfer
4 additional analog inputs (16 bit, differential, ±5V)
In the future it will include SDM data output for Campbell ® Scientific, Inc. dataloggers.
Check www.licor.com for the latest software updates.
Figure 3-1. Inside the LI-7550.
3-1
Operation with the LI-7550 Analyzer Interface Unit
Inside the LI-7550 there are three Ethernet ports and one port for a USB data storage device. Two of the Ethernet ports are connected to the Ethernet ports on the front panel. It
does not matter to which ports these internal cables are connected (they are connected to
ports 2 and 3 in the photo below). The third port is not connected to the panel, but can be
used in the field to connect an Ethernet device, such as a laptop computer.
LI-COR includes a 4 GB industrial rated USB drive from Delkin Devices, Inc. (Poway,
CA) for use with the LI-7550. The LI-7550 supports FAT and Linux ext3 file systems.
We recommend that you only use an industrial rated USB flash drive. Non-industrial
rated flash drives can fail, causing you to lose data.
Power On
The LI-7550 has no power switch – it turns on when power is supplied through the power
cable. The LI-7550 requires a constant power source of 10.5-30 VDC (2 amps). When
power is supplied the “Power” LED on the indicator panel will illuminate, and it will stay
lit as long as power is supplied, The “Ready” LED will turn on when the instrument embedded software has loaded and the LI-7550 is ready to communicate with a computer.
Connecting an LI-7700 to an LI-7550
The LI-7700 connects to the LI-7550 using the Ethernet cable (p/n 392-10108), which
terminates with Turck® connections on both ends. Attach one terminal to the Ethernet
connection on the LI-7700 and the other to either the Ethernet 1 or 2 terminals on the
LI-7550. You can now connect the LI-7550 to a computer or network with the vacant
Ethernet port on the LI-7550 connection panel, either of the two vacant Ethernet ports
inside the box, or with the RS-232 cable (p/n 392-10268).
Prior to using the LI-7700 with an LI-7550, the two devices must be configured to communicate with each other. This is described below:
3-2
1.
Connect power to both instruments. Connect the LI-7700 and LI-7550 with the
Ethernet cable, as described above. Connect the LI-7550 to your computer or network with the Ethernet or RS-232 cable. Be sure to use a computer that has the
LI-7700 Windows Application Software.
2.
Launch the Windows Application Software, but don’t connect to an instrument.
3.
Click the Help icon and click About.
Operation with the LI-7550 Analyzer Interface Unit
4.
In the “About” dialog box click Factory Setup… > Proceed. In the “Factory Setup”
dialog box you should see both the LI-7700 and the LI-7550, similar to the figure
below.
5.
Click on the LI-7550, then click the Config LI-7550 button.
6.
In the resulting dialog box, confirm that the text in the field called “Head:” matches
the text on the Factory Setup display for the name of the LI-7700 Analyzer (it is not
case sensitive), or edit the field so they match. In this case, the name is “ch4-11”.
7.
If you changed the name, click the Apply button to confirm the name change, then
restart both devices.
8.
Confirm that the two devices are communicating by connecting to the LI-7700 with
the Windows Application Software. Insert a USB storage device into the LI-7550
3-3
Operation with the LI-7550 Analyzer Interface Unit
USB port. If the USB device appears in the “USB Logging” window (see page 3-15),
both are configured correctly.
Connecting with the RS-232 (Serial) Port
The LI-7550 enables RS-232 communications with the LI-7700. To use this feature, connect the LI-7550 to your computer’s RS-232 connection with the RS-232 adapter cable
(p/n 392-10268). An RS-232 to USB adapter may be required. In the LI-7700 software,
click “Connect”, check the “RS-232” button, and choose the COM port (between 1 and
32) that the instrument is connected to. Click the “Connect” button.
Cable Connections and Cables
Cable connections are found on the bottom panel of the LI-7550. Each connection
includes a dust/moisture cover that should be kept in place any time the connection is not
in use.
POWER
SDM
ETHERNET 1
ETHERNET 2
RS-232
DAC
OUTPUT
IRGA
AUXILIARY
INPUT
SENSOR
ACCESSORY
PRESSURE
Figure 3-2. LI-7550 connection panel.
The LI-7550 includes a variety of cables for connecting power, sensors, and external data
storage devices. All cables are 5 meters in length and are manufactured by Turck, Inc.
Minneapolis, MN, see page 8-10). If you need longer cables, several custom-length cables
can be purchased from Turck, Inc. Table 3-1 below lists both LI-COR part numbers and
the corresponding Turck part numbers for each cable. You can also construct your own
extension cables. Table 3-2 lists pin assignments and wire colors for the power, SDM, and
Analog Input and Output cables. This table is reproduced on the inside front cover of the
LI-7550 Analyzer Interface Unit.
3-4
Operation with the LI-7550 Analyzer Interface Unit
Table 3-1. Turck Eurofast® cables used to connect to the LI-7550. An asterisk (*) refers to cable length.
LI-COR p/n
9975-030
392-10093
392-10268
Cable
Power
SDM Interface
Serial
392-10109
392-10108
392-10107
Analog In/Out
Ethernet
Ethernet Adapter
Connection
4-pin female
4-pin male
6-pin female to DB9 female
12-pin male
8-pin male-male
8-pin female to RJ45
Turck p/n
RK4.41T-*/S529
RSS 4.4T-*
RKC 6T-*DB9F/CS12317
RSS 12T-*
RSS RSS841-*M
RKC RJ45 840-*M
Power Cable
The power cable (p/n 9975-030) is a 4-pin female connector plug that attaches to the
connector labeled POWER on the LI-7550 Analyzer Interface Unit front panel. The
power cable is terminated with black (-) and red (+) leads for connection to a user supplied
10.5-30 VDC power supply.
SDM Interface Cable
SDM is not implemented in early realease instruments. Check www.licor.com for software
updates that enable this functionality. The SDM interface cable (p/n 392-10093) is for
connection to Campbell ® Scientific, Inc (Logan, Utah) dataloggers using the Synchronous
Devices for Measurement (SDM) data communication protocol. SDM communications
are enabled in the Campbell Scientific datalogger. The SDM interface cable plugs into the
connector labeled SDM on the LI-7550 Analyzer Interface Unit front panel.
Analog Input/Output Cable
The Analog Input/Output Cable (p/n 392-10109) is for connecting user-supplied sensors
(i.e., pressure, temperature, sonic anemometer) and/or to a data logger. The pin
assignments and wire colors are shown below in Table 3-2. There are four analog input
channels available. When used with external input devices, this cable plugs into the
connector labeled AUXILIARY INPUT on the LI-7550 Analyzer Interface Unit front
panel.
This cable can also be used for data output to logging devices using the digital-to-analog
converters (DACs). Six DAC channels are available; the pin assignments and wire colors
are shown below in Table 3-2. The cable plugs into the connector labeled DAC
OUTPUT on the LI-7550 Analyzer Interface Unit front panel.
3-5
Operation with the LI-7550 Analyzer Interface Unit
This cable can also be used to connect directly to sensors or output devices; the optional
weatherproof Auxiliary Interface Unit (p/n 7550-101) can be used in place of this cable.
Use of the 7550-101 with the LI-7700 is described earlier in this section, and with the
LI-7550 is described later in this section. Note that only one Analog Input/Output cable
is included with the LI-7550. If you intend to use both the Auxiliary Input and DAC
Output ports on the LI-7550 you will need to acquire an additional 392-10109 cable or
the 7550-101 Auxiliary Sensor Interface.
Table 3-2. LI-7550 Pin Assignments.
LI-7550 Pin Assignments
SDM
AUXILIARY INPUT
DAC OUTPUT
PIN 1
BROWN
SDM_EN
PIN 1
WHITE
AUX1+
PIN 1
WHITE
DAC1
PIN 2
WHITE
SDM_CLK
PIN 2
BROWN
AUX1-
PIN 2
BROWN
DAC2
PIN 3
BLUE
SDM_DATA
PIN 3
GREEN
AUX2+
PIN 3
GREEN
DAC3
PIN 4
BLACK
GND
PIN 4
YELLOW
AUX2-
PIN 4
YELLOW
DAC4
COUPLING
BARE
EARTH GND
PIN 5
GREY
AUX3+
PIN 5
GREY
DAC5
POWER
PIN 6
PINK
AUX3-
PIN 6
PINK
DAC6
BROWN
VIN-
PIN 7
BLUE
AUX4+
PIN 7
BLUE
READY
VIN-
PIN 8
RED
AUX4-
PIN 8
RED
NC
VIN+
PIN 9
ORANGE
+5V
PIN 9
ORANGE
NC
VIN+
PIN 10
TAN
GND
PIN 10
TAN
GND
INPUT: 10.5 - 30VDC
PIN 11
BLACK
GND
PIN 11
BLACK
GND
FUSE: 5A F 125/250V
PIN 12
VIOLET
GND
PIN 12
VIOLET
GND
PIN 1
BLACK
PIN 2
WHITE
PIN 3
BLUE
PIN 4
BLACK
RED
3-6
Operation with the LI-7550 Analyzer Interface Unit
Serial RS-232 Cable
The RS-232 cable (p/n 392-10268) is a 5m null modem cable with a 6-pin female circular
connector that attaches to the connector labeled RS-232 on the LI-7550 Analyzer
Interface Unit front panel. The other end has a standard DB-9 female connector for direct
connection to a computer. Alternatively, the RS-232 cable can be connected to an RS-232to-USB adapter to use the RS-232 connection with a USB port.
LI-7550
External
RS-232 Connector
RS-232 Cable
p/n 392-05620
9-Pin Female
Connector
3-7
Operation with the LI-7550 Analyzer Interface Unit
Ethernet Cables
Two Ethernet Cables (p/n 392-10107 and 392-10108) are included for connecting to a
Local Area Network (LAN) via an Ethernet port. Part # 392-10108 is a 5m cable
terminated on both ends with a male Turck connector. One end attaches to the LI-7550
Analyzer Interface Unit, and the other end attaches to the short (0.3m) Ethernet adapter
cable (p/n 392-10107) The short cable is terminated with an RJ45 Ethernet connector. It
plugs into an Ethernet wall socket or a computer’s Ethernet port.
LI-7550
External
Ethernet Connector
Ethernet Cable
p/n 392-10108
Ethernet Cable
p/n 392-10107
3-8
or
Operation with the LI-7550 Analyzer Interface Unit
LI-7550 Analog Inputs/Outputs
As mentioned previously, the 7550-101 can serve as a terminal strip for analog inputs or
outputs for the LI-7550. Alternatively, the Analog Input/Output Cable (p/n 392-10109)
can be used. To use Options 2 or 3 (Figure 2-1) with the 7550-101, be sure the LK1
jumper is positioned over the two pins nearest the LI-7550 label. Refer to page 2-17 if
information on the LI-7700 analog inputs (Option 1). Below we describe how to configure the 7550-101 and the corresponding wires/pins in the Analog Input/Output Cable
for LI-7550 analog inputs.
Auxiliary Sensor Interface Terminals (Options 2 & 3)
360-09333 Rev 2
Made in USA
www.licor.com
LI-7700
LK1
LI-7550
P2
NC
GND
+5V
GND
+5V
GND
RESERVED
GND
AUX4RESERVED
NC
GND
PLUGS
GND
READY
AUX4+
T3
T_REF
GND
DAC6
AUX3T2
DAC5
AUX3+
T1
GND
GND
GND
DAC4
AUX2AUX4
DAC3
AUX2+
AUX3
GND
GND
GND
DAC2
AUX1AUX2
DAC1
A OUT
AUX1+
AUX1
LI-7550
A IN
LI-7700
ANALOG IN
P1
To gain access to the inside of the 7550-101, loosen the four #1 Philips head screws on
each corner of the top cover. Remove the cover. The interior of the interface box appears
below.
PLUGS
Figure 3-3. Schematic of the Auxiliary Interface Unit interior.
3-9
Operation with the LI-7550 Analyzer Interface Unit
The terminal strips connections are shown below:
GND
+5V
GND
AUX4-
GND
AUX4+
AUX3-
AUX3+
GND
AUX2-
AUX2+
GND
AUX1-
AUX1+
When Used for Analog Inputs (LI-7550)
Figure 3-4. Terminal connections for analog inputs (Option 2).
The terminal positions are numbered and configured as follows. Corresponding analog input wire colors are shown on the right.
Option 2a
7550-101 Auxiliary
Sensor Interface
Terminal Inputs
1
AUX1+
2
AUX13
GND
4
AUX2+
5
AUX26
GND
7
AUX3+
8
AUX39
AUX4+
10
GND
11
AUX412
GND
13
+5V
14
GND
a
Analog Inputs ±5V
3-10
Description
Auxiliary Input 1 positive
Auxiliary Input 1 negative
Ground
Auxiliary Input 2 positive
Auxiliary Input 2 negative
Ground
Auxiliary Input 3 positive
Auxiliary Input 3 negative
Auxiliary Input 4 positive
Ground
Auxiliary Input 4 negative
Ground
+5V supply
Ground
Analog In/Out Cable
(p/n 392-10109)
Wire Color
Pin
White
Pin 1
Brown
Pin 2
Tan
Pin 10
Green
Pin 3
Yellow
Pin 4
Tan
Pin 10
Grey
Pin 5
Pink
Pin 6
Blue
Pin 7
Black
Pin 11
Red
Pin 8
Violet
Pin 12
Orange
Pin 9
Tan
Pin 10
Operation with the LI-7550 Analyzer Interface Unit
GND
NC
GND
NC
GND
READY
DAC6
DAC5
GND
DAC4
DAC3
GND
DAC2
DAC1
When Used for Analog Outputs
Figure 3-5. Terminal connections for analog outputs (Option 3).
The terminal positions are numbered and configured as follows. Corresponding analog
output wire colors are shown on the right.
Option 3b
7550-101 Auxiliary
Sensor Interface
Terminal Outputs
1
DAC1
2
DAC2
3
GND
4
DAC3
5
DAC4
6
GND
7
DAC5
8
DAC6
9
READY
10
GND
11
NC
12
GND
13
NC
14
GND
b
Analog Outputs 0-5V
Description
DAC channel 1 positive
DAC channel 2 positive
Ground
DAC channel 3 positive
DAC channel 4 positive
Ground
DAC channel 5 positive
DAC channel 6 positive
Analyzer Ready
Ground
No connection
Ground
No connection
Ground
Analog In/Out Cable
(p/n 392-10109)
Wire Color
Pin
White
Pin 1
Brown
Pin 2
Tan
Pin 10
Green
Pin 3
Yellow
Pin 4
Tan
Pin 10
Grey
Pin 5
Pink
Pin 6
Blue
Pin 7
Black
Pin 11
Red
Pin 8
Violet
Pin 12
Orange
Pin 9
Tan
Pin 10
3-11
Operation with the LI-7550 Analyzer Interface Unit
Electrical Connections
All analog devices connected to the 7550-101 Auxiliary Sensor Interface must be referenced to the ground (GND) connection to use Option 2. Some examples are shown
below.
Analog Device
7550-101 Analog Inputs
Analog Out +
Aux +
Analog Out -
Aux -
Ground or
Common
Aux Ground
Analog Out +
Aux +
Ground or
Common
Aux Aux Ground
Analog Out +
Aux +
Common
Aux -
Ground
Aux Ground
Analog Out +
Aux +
Common
Aux -
Ground
NC
Aux Ground
Connection Notes:
1. All LI-7550 auxiliary analog input ground connections are internally connected together.
2. All LI-7550 auxiliary analog output ground connections are internally connected together.
3. Analog devices with both ground and common outputs can share these outputs with
their power supply ground.
4. LI-7550 analog inputs are electrically isolated from the LI-7550 power input.
5. LI-7550 analog outputs are electrically isolated from the LI-7550 power input and
isolated from the analog inputs.
3-12
Operation with the LI-7550 Analyzer Interface Unit
For additional 7550-101 & Analog Input/Output usage instructions, refer to the following pages:
LI-7700 Inputs (Option 1) instructions: page 2-17
Wiring instructions: page 2-19
Mounting instructions: page 2-25
Configuring LI-7550 Analog Inputs: page 3-14
Configuring LI-7550 Analog Outputs: page 3-18
3-13
Operation with the LI-7550 Analyzer Interface Unit
Configuring the LI-7550
The LI-7550 is configured through the LI-7700 software. When settings are configured in
the LI-7700 software, this information is stored in the LI-7700. Then the LI-7550 pulls
this information from the LI-7700 when the two components are connected and powered
up.
Note: It is possible to connect an LI-7700 to an LI-7550 that is configured for use with an
LI-7200 or LI-7500A CO2/H2O Analyzer. In this configuration, you will be able to log
LI-7700 data to the LI-7550 USB device in a separate file from the one generated by the
CO2/H2O analyzer. If the LI-7550 is configured to support an LI-7200 or LI-7500A, it will
not be possible to configure the corresponding auxiliary inputs, SDM, RS-232, or DAC
outputs from the LI-7700 application software. Instead, use the LI-7200/LI-7500A
Windows Application software to configure those channels. The software will prohibit you
from opening the “Configure LI-7550 Outputs” dialog from the LI-7700 application.
Conversely, if the LI-7550 is formatted to operate with an LI-7700, you will have access to all
functions in the software. Contact LI-COR Biosciences for more information.
Configuring Analog Inputs (LI-7550)
Analog inputs (Option 2) are configured
from the “Configure Auxiliary Inputs” dialog box. These are labeled Aux5 through
Aux8 in the lower block of inputs. Two
mathematical conversions of analog input
voltages can be configured in the dialog box:
1) a third order polynomial or 2) a Steinhart
equation (for computing temperature in K
from a thermistor).
These are described in detail on page 2-21,
Configuring Auxiliary Inputs (LI-7700). After configuring the inputs, click Apply or
OK to implement the settings.
Analog Input Time Delays
Auxiliary Inputs 5-8 (available only on the
LI-7550) have a fixed time delay of 1 second
in an LI-7550 configured for the LI-7700.
3-14
Operation with the LI-7550 Analyzer Interface Unit
USB Data Logging
Data logging options for storing data on a USB storage device (with the LI-7550) are accessible in the Logging frame. These settings are configured through the LI-7700 software
and implemented automatically when the LI-7700 is connected with an LI-7550 and both
instruments are powered up.
To log data to a LI-7550:
1.
Click the USB… button in the Logging frame.
2.
In the “Configure USB Log Data” dialog box, select the variables that you would like
to log and click Apply. Auxiliary Inputs 1-4 and Thermocouple Inputs 1-3 are described on page 2-17 (Option 1), and Auxiliary Inputs 5-8 are described on page 3-9
(Option 2).
3-15
Operation with the LI-7550 Analyzer Interface Unit
3.
In the “Log File” frame, choose to Log Status Columns to a separate file or to the data
file. Then choose whether to split the file, and how often (from 15 minutes to 24
hours). Click Apply.
4.
Click the Start button to begin logging data. The Start button will become active (a
Start button is visible in both the “Configure USB Log Data” view and the Main
View).
5.
If a USB storage device is present, data logging will begin after the LI-7700 is connected to the LI-7550 and both instruments have completed their start-up cycles.
6.
To remove the USB Storage device, press the “Eject” button in the LI-7550. The
LI-7550 will stop writing data to the storage device until another USB device is
inserted, after which it will immediately begin logging data.
The LI-7550 supports FAT and Linux ext3 file systems.
Note: the LI-7550 must have a suitable USB storage device installed. Data logging will stop
when the storage device has reached capacity, but will automatically resume when a USB storage device is reattached, assuming it has storage space available. Data logging also automatically starts when the instrument starts up (if so configured), following a power interruption for
example.
3-16
Operation with the LI-7550 Analyzer Interface Unit
Configuring LI-7550 Outputs
RS-232 Output
The RS-232 page is used to set the LI-7700 RS-232 port configuration for unattended
data collection. After configuration, click Apply; the LI-7700 will begin to send data out
the RS-232 port according to these parameters. Since this controls a serial data stream,
there is no concept of files or splitting files. The baud rate is set to 57,600. When sending
data through the serial connection, note that the baud rate may limit the number of samples that can be output. Therefore, you may wish not to log the Diagnostics or Status data.
3-17
Operation with the LI-7550 Analyzer Interface Unit
Analog Outputs
The LI-7550 has the capacity to output up to six variables on DAC channels 1-6. The
DACs page allows you to configure the DAC output channels by specifying the source
that drives the analog signal (CH4 mmol mol-3, CH4 μmol mol-1, temperature, pressure,
signal strength, and set point), the source channel value that corresponds to 0V, and the
source channel value that corresponds to 5V.
For example, DAC1 could be configured to output a voltage signal for CH 4 with 0 mmol
m-1 proportional to 0V, and 5 mmol m-1 equal to 5V by setting the dropdown menu to
read CH4 (mmol m-1) and entering 0 and 5 in the “Low Output” and “High Output”
fields respectively.
The “Set Point” field will be available when the “set point” option is selected in the Source
drop down menu. Set point is a DC output value for testing DACs and data storage devices. The output voltage is converted via:
Output Voltage (V) = 5 V * (Set Point Value – 0 V Value)/(5 V Value – 0 V Value)
The analog outputs on the LI-7550 interface box are delayed by 1 second to account for
network latencies. The total delay at a particular output rate is increased by the averaging
filter according to the expression:
3-18
Operation with the LI-7550 Analyzer Interface Unit
Signal Delay =1s +
( 40Hz Output Rate 1)
2 40Hz
The table below summarizes the delays:
Output
Rate
Frequency
Response (-3db)
Analog Output
Signal Delay
40 Hz
20 Hz
10 Hz
5 Hz
2 Hz
1 Hz
20 Hz
10 Hz
5 Hz
2.5 Hz
1 Hz
0.5 Hz
1.0 S
1.0125 s
1.0375 s
1.0875 s
1.2375 s
1.4875 s
SDM
In early release instruments, SDM is not implemented. Check the LI-COR website for
software updates and instructions for enabling SDM.
3-19
Operation with the LI-7550 Analyzer Interface Unit
LI-7550 Clock
The LI-7550 clock is separate from the LI-7700 clock, but it also uses Unix (POSIX) time
and the Precision Time Protocol (see page 2-13). When the two components are used together, the LI-7550 clock is “slave” to the LI-7700 clock, meaning the time stamp comes
from the LI-7700. The LI-7550 clock has the same setting options as the LI-7700 clock.
To view/set the time in the LI-7550:
3-20
1.
Connect the LI-7550 to your computer using the Ethernet, or to your network or
computer using the Ethernet cable (RS-232 does not support this).
2.
Launch the LI-7700 software, click the Help question mark, and select About.
3.
Click Factory Setup… (see below) and select Proceed after reading the warning.
4.
Select the “Base Box” and click on Config LI-7550.
5.
Click on the Clock… button.
Operation with the LI-7550 Analyzer Interface Unit
6.
Configure the clock settings as desired. In the “Precision Time Protocol” frame,
choose “Automatic”, “Slave Only”, or “Preferred Clock”. “Slave Only” is the recommended setting.
7.
Apply the settings and close the dialog.
3-21
Operation with the LI-7550 Analyzer Interface Unit
Mounting the LI-7550 Analyzer Interface Unit
Two brackets (p/n 6575-033) are included with the LI-7550 that can be used to mount it
to a tripod or other post, using bolts or U-bolts. There are holes in the four corners of the
box, as well, that can be used to attach the box directly to a flat surface.
The mounting brackets are designed to accommodate a square or circular mounting post
of up to 1.25" in width (diameter). Use a 3/16" hex key to attach the mounting brackets to
the Analyzer Interface Unit using 4 socket head screws (p/n 140-02654). The U-bolts can
then be inserted through the holes in the mounting bracket, and tightened around the
post, as shown below.
LI-7550 Analyzer Interface Unit Top View
Nut
Mounting Bracket
U-bolt
Bolts
(p/n 140-02654)
Post
LI-7550
Analyzer
Interface
Unit
Side View
Figure 3-6. Attach the brackets to the Analyzer Interface Unit and secure it to the mounting post.
There are some additional considerations that should be taken into account when locating
the Analyzer Interface Unit, including:
1.
3-22
The cable that connects to the sensor head is 5 meters in length; determine the height
at which the sensor head will be mounted, and plan to mount the Analyzer Interface
Unit accordingly. This cable could be up to several hundred feet long if needed.
Operation with the LI-7550 Analyzer Interface Unit
2.
The thermal properties of the Analyzer Interface Unit are such that it is OK to place
the box in direct sun.
3.
The power cord provided is 5 meters in length. Longer cables can be purchased
through distributors of Turck, Inc. (see List of Suppliers, page 8-11).
4.
For lightning protection run an independent bonding wire from the instrument
ground (see Figure 3-2) to the earth.
The Washer Assembly mounts similarly. The washer hose is 5 m long. It should not be extended because the washer spray motor is not designed to pump the fluid higher than that.
The following schematic shows one potential configuration.
Washer
Nozzle
Washer
Hose
Analog Input Cable
or
7550-101
Washer
Power Cable
For use with:
• LI-7200 CO2/H2O Analyzer
• LI-7500A CO2/H2O
• LI-7700 CH4 Analyzer
Data Logging on LI-7550
(CH4, U, V, W, Ts, ancillary,
and diagnostic data)
LI-7550 Outputs:
Ethernet, RS-232,
SDM, and DACs
®
Power In:
Sonic Anemometer
LI-7700: 10.5 to 30 VDC, 2 amp
LI-7550: 10.5 to 30 VDC, 3 amp
Washer
Reservoir
Figure 3-7. A typical field deployment of the LI-7700 and accessories in an eddy covariance
application.
3-23
4
Data Files
When logging data to a computer or USB storage device (with the LI-7550), the LI-7700
outputs data as tab delimited text files, which can be opened in any common spreadsheet
application. Each file consists of a file header, diagnostics header, data header, and data. An
example data file and descriptions of the file components are shown below.
Model:
File Type:
Instrument:
Serial Number:
Soware Version:
Timestamp:
Timezone:
LI-7700 Open Path CH4 Analyzer
2
LI-7700-1
7700-104
1.0.0
2/18/2010 14:54
US/Central
File Header
DATADIAGH
BOXCONNECTED
BADAUXTC3
BADAUXTC2 BADAUXTC1 MOTORFAILURE CALIBRATING …
DATAH
SECONDS
NANOSECONDS DIAG
CH4
CH4D
TEMP
…
DATA
DATA
DATA
DATA
DATA
DATA
DATA
…
1266526458
1266526459
1266526459
1266526460
1266526460
1266526461
1266526461
…
500000000
0
500000000
0
500000000
0
500000000
…
2.53497
2.5242
2.52214
2.50837
2.52209
2.52735
2.519
…
0.103356
0.102793
0.102688
0.102151
0.102707
0.102912
0.102442
…
24.692
24.9592
25.0056
24.9534
24.9605
24.9788
25.2609
…
…
…
…
…
…
…
…
…
Diagnostics Header
Data Header
Data
57358
57358
57358
57358
57358
57358
57358
…
File Header
The header is part of every data file produced by the LI-7700. It includes the following
fields:
Table 4-1. Data file header.
Header Label
Model:
File Type:
Instrument:
Serial Number:
Software Version:
Timestamp:
Timezone:
Description
Analyzer
#
Instrument name
Instrument serial number
Instrument firmware version
Date and time the file was created
Time zone setting in the instrument
4-1
Data Files
Data
The data is in columns below the DATAH row. The row above the data header includes a
list of diagnostic codes that are output with each data file. This information is summarized
by the value in the data field called DIAG. These values are described in the section called
“Diagnostic Codes” below.
Data Header
The data header will include all the variables that are selected in the PC or USB logging
window. A UTC time stamp (seconds and nanoseconds) is always output with each record
in a file. Therefore, it is not necessary to output date and time unless you wish to have the
local time stored with the file.
The following list of items may be visible in the data header row, depending on which values are logged:
Table 4-2. Data header.
Column Heading
SECONDS
NANOSECONDS
DIAG
CH4
CH4D
TEMP
PRESSURE
RSSI
DROPRATE
AUX1
AUX2
AUX3
AUX4
AUX5
AUX6
AUX7
AUX8
4-2
Description
Seconds in UNIX time, or the time the instrument is set to
Nanoseconds
Diagnostic value, an integer
Methane mole fraction (μmol/mol)
Methane number density (mmol/m3)
Temperature measured with the LI-7700 thermocouple (°C)
Pressure measured near the optical path (kPa)
Signal strength (Residual Signal Strength Indicator, 0-100%)
Percentage of 1000Hz scans that were dropped at an output rate
of 40 Hz (0-100%).
Auxiliary input 1
Auxiliary input 2
Auxiliary input 3
Auxiliary input 4
Auxiliary input 5
Auxiliary input 6
Auxiliary input 7
Auxiliary input 8
Data Files
AUXC1
AUXC2
AUXC3
DATE
TIME
CHK
Auxiliary thermocouple input 1 (°C)
Auxiliary thermocouple input 2 (°C)
Auxiliary thermocouple input 3 (°C)
Instrument date, reflects time zone setting (MM/DD/YYYY)
Instrument time, reflects time zone setting (HH:MM:SS)
A check sum feature to check integrity of data
4-3
Data Files
Diagnostics Header
If the “Diagnostics” check box was checked in the PC, USB, or RS-232 outputs, a diagnostic header and column is included in each data file. The Diagnostics Header is a list of potential diagnostics that are output with each file. The DIAG column contains diagnostic
values affiliated with each record in the file, and these values encode one or more pieces of
diagnostic information. Each value is an integer between 0 and 65535, which can indicate
up to 16 diagnostics. The following guide and example can help interpret this diagnostic
information:
Table 4-3. Diagnostic codes output with the LI-7700 data record.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Diagnostics Header
BOXCONNECTED
BADAUXTC3
BADAUXTC2
BADAUXTC1
MOTORFAILURE
CALIBRATING
BOTTOMHEATERON
TOPHEATERON
PUMPON
MOTORSPINNING
BLOCKTEMPUNREGULATED
LASERTEMPUNREGULATED
BADTEMP
REFUNLOCKED
NOSIGNAL
NOTREADY
Integer
1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
Meaning
LI-7550 Attached
Bad thermocouple values
Bad thermocouple values
Bad thermocouple values
Mirror cleaner motor failure
Calibration in process
Lower mirror heater on
Upper mirror heater on
Pump motor running
Mirror spin motor on
Block temperature unregulated
Laser cooler unregulated
Optical path thermocouple failure
Reference methane signal not locked
No laser signal detected
Instrument is not ready
Typically, the diagnostic field will have value of 14. This indicates that readings from the
thermocouples are bad, and it will occur anytime a functioning thermocouple is not attached. The “14” is the sum of values in the “Integer” column from rows 2, 3, and 4 in the
table above (2+4+8). If you are using an LI-7550, this value would be “15”.
To interpret a diagnostic code:
1.
4-4
Identify the integer in the DIAG column of the data file.
Data Files
2.
Find the largest value in the Integer column of Table 4-3 that is the value from the
DIAG column. The diagnosis associated with that value occurred.
3.
Subtract the DIAG value from the Integer. If the difference is 0, there are no other
codes. Otherwise, repeat step 2 using the difference rather than the DIAG code.
4.
Repeat steps 2 and 3 until the difference equals 0.
The following example also shows how to interpret the code:
1.
Say, for example, that you encounter the code 17231 associated with a series of logged
values in the DIAG column.
2.
Refer to Table 4-3 and locate the largest value that is 17231. This is 16384, which
indicates that no laser signal was detected. Find the difference: 17231-16384=847.
3.
In Table 4-3, find the largest value that is the 847. It is 512, which indicates that the
lower mirror was spinning. Find the difference: 847-512=335.
4.
Find the largest value that is 335. It is 256, which indicates that the pump was running. Find the difference: 335-256=79.
5.
Find the largest value that is 79. It is 64, which indicates that the lower mirror
heater was on. Find the difference: 79-64=15.
6.
Repeating the steps above, it is determined that three thermocouples were not attached or were dysfunctional, and the LI-7700 is connected to an LI-7550.
Hint: Any time an odd number occurs in the DIAG field, it indicates that an LI-7550 was in
use. Even numbers indicate that there was no LI-7550 attached.
4-5
Data Files
Status Columns
When logging to a USB storage device or a host PC, you can choose to log status columns
to the log file, to a separate file, or not at all. Status data can also be sent through the RS232 output. Status data are always logged at 2 Hz. When the status file is logged to a separate file, it will include a header that is identical to the data file header. Note: If you choose
to log status columns to the data file, status records will be interspersed with the data records by
time. The first column contains a header to distinguish the status and data records.
Status Header
The following header is output with the status file.
Table 4-4. Status file header.
Column Heading
SECONDS
NANOSECONDS
DIAG
RSSI
REFRSSI
LCTSETPT
LCTACTUAL
BCTSETPT
BCTACTUAL
CHASSISTEMP
OPTICSTEMP
OPTICSRH
AUXREFTEMP
MOTORSETPT
MOTORACTUAL
USB
USBCAPACITY
USBFREESPACE
REF
GND
OPTICSDELTA
CHK
4-6
Description
Seconds in UNIX time, or the time the instrument is set to
Nanoseconds
Diagnostic value, an integer
Signal strength (Residual Signal Strength Indicator, 0-100%)
Reference Signal Strength (0-100%)
Laser cooler temperature set point (°C)
Laser cooler temperature measured (°C)
Block cooler temperature set point (°C)
Block cooler temperature measured (°C)
Temperature in lower housing (disabled)
Reference junction temperature for top thermocouple (°C)
Relative humidity in the upper dome (%)
Temperature of Auxiliary Sensor Interface, 7550-101 (°C)
Spin motor set point (preferred alignment)
Spin motor position (actual alignment)
Device present
USB device capacity
USB device free space
A diagnostic value used in technical support
Temperature difference between air and upper mirror
A checksum feature to check the integrity of data
5
Theory and Equation Summary
The Beer-Lambert Law describes the absorption of radiation by a gas sample:
( S (T ) g (v v ) Nl )
I = I 0 e = e
0
5-1
where I and I0 are received and incident optical power, is an absorbance, S(T) is absorption line strength, g(ν-ν0) is a normalized lineshape function for the line at ν0, N is gas
number density and l is the path length.
When fractional absorbance I/I0, is small (<0.01), I I0 and linear approximation can be
used.
e 1 and I I 0 (1 ) , so
I 0 I I
=
I0
I0
5-2
Using Wavelength Modulation Spectroscopy (WMS), the LI-7700 laser scans across a single feature in 2ν3 absorption band of methane near 1.6 microns with high resolution and at
a high repetition rate. The wavelength is modulated at sub-MHz frequency, virtually
eliminating 1/f flicker noise of the laser source and allowing detection of fractional absorption less than 10-5, which is not attainable with conventional direct absorption. The
LI-7700 demodulates the resulting signal at twice the modulation frequency, and then
compares the result to a reference signal shape, which is stored in the software, to
determine the CH4 concentration (these are visible on Diagnostic Page1). Pressure and
temperature induced changes in lineshape and population distribution, as well as changes
in laser power and mirror reflectivity are compensated using computational fitting
algorithms so that measurements are accurate over a wide range of pressure, temperature,
and environmental conditions.
Temperature Dependence of Absorption Line Strength
Line strength of a particular transition is a fundamental spectroscopic property and it is
proportional to the population of the lower state in the transition and absorption cross-
5-1
Application Information
section for that transition. The population of the individual rotational state can be calculated from Boltzmann’s distribution:
hc
( )
S T Erot
e kT
N ''
=
N
Q T
5-3
( )
where h is Planck’s constant, k is Boltzmann’s constant, N is total number density, N’’ is
the number density of the probed state, Erot is rotational energy of the probed state, Q(T) is
the partition function. The absorption cross-section and rotational energy for a particular
transition can be obtained from the HITRAN database. The partition function Q is also
available as a function of temperature in tabulated form from HITRAN.
Line Broadening Mechanisms
In the near infrared region, under ambient atmospheric conditions, the main sources of
line broadening for CH4 are Doppler broadening and pressure (collisional) broadening.
For a single rotational line, the intensity profile of Doppler broadening as a function of
wavelength is described by the Gaussian:
(
)
g D v;v D =
where
ln 2
v D
e
v v0 ln 2 v D 2
5-4
v D is the Doppler half width at half maximum (HWHM) of a Gaussian profile
and is:
( )
v D T = ln 2
v0
c
2kT
m
5-5
where k is the Boltzmann constant, m is molecular mass, c is the speed of light, and T is
temperature in K.
Pressure broadening is described by the Lorentzian lineshape:
(
)
g L v;v L =
5-2
v L
1
v v 2 + v
0
L
(
) ( )
2
5-6
Application Information
where
v L is Lorentzian half width and can be calculated using empirically determined
parameters from HITRAN database:
P T v L P,T = T0 , P0 0 P0 T (
)
(
)
r
5-7
where T is temperature in K, P is pressure in Pa, (T0,P0) (pressure broadening at T0 and
P0)and r (temperature dependence of pressure broadening) are parameters from the
HITRAN database for the individual line, T0=296 K, P0=101325 Pa.
The Voigt lineshape is a convolution of the Lorentzian and Gaussian:
(
+
) g ( v '; v ) g ( v v '; v ) dv '
g v v; v D ; v L =
D
D
L
5-8
L
It can be rewritten in the form:
()
gv v =
+
ln 2 v L 1
et
ln 2 dt
v D v D y2 + x t
2
(
5-9
)
2
where x ln 2 v v0 and y ln 2 v L .
v D
v D
The Voigt integral has no analytic solution but can be approximated by numerical methods to a high degree of accuracy.
In summary, population of the lower state is a function of temperature and two different
mechanisms responsible for lineshape changes: Doppler broadening (a function of temperature), and pressure broadening (a function of both temperature and pressure). To calculate number density from measured absorption, knowledge of both temperature and
pressure to a high degree of accuracy is absolutely essential.
5-3
Application Information
Wavelength Modulation Spectroscopy
Injection Current
With WMS, the wavelength of light emitted by the laser is modulated by injection current
at sub-MHz frequency f while scanning across the absorption feature.
Wavelength Sweep
Modulation Dither (sub-MHz)
Time
Wavelength modulation over the lineshape results in modulation at f and its higher
harmonics (2f, 3f, etc), which are proportional to the absorption and resemble a derivative
of the corresponding order. Because very strong amplitude modulation is also present at
carrier frequency f, higher order harmonics are preferable for detecting a small absorption
feature. The LI-7700 uses phase-sensitive demodulation by a digital lock-in amplifier at 2f
to obtain a background-free signal with excellent noise rejection.
Lineshape
Modulation dither
2f demodulation
Absoprtion Feature
The magnitude of the waveform is linear with number density CH4 (=N from the previous discussion) and proportional to incident power I0. The recorded waveform is compared by least squares fitting with the reference waveform (with P0, T0, CH40 calculated
using the HITRAN database and numerical computation methods for a WMS transfer
function).
The sample waveform is computed from:
r i i = I0
5-4
5-10
Application Information
where i is the measured lineshape, I0 is the received laser power, and r[i] is the detector
output, which is also an array of S spectral samples. Number density (not corrected for
temperature and pressure) is computed from:
S
CH 4 = K s i i ref i K z i=1
5-11
where CH4 is methane number density, i is waveband 1 through S, Ks is the span value, Kz
i is the measured lineshape, and i is the reference lineshape.
is the zero value, ref Number density, as shown in equation 5-11, is not corrected for fast temperature and pressure fluctuations. It is a standard value, which requires subsequent processing when computing fluxes with the eddy covariance method.
Effects of pressure and temperature induced changes in lineshape and population distribution, and resulting changes in WMS waveforms are pre-calculated and tabulated. These are
stored in the instrument. If precise temperature and pressure measurements were acquired,
they could be implemented with:
CH 4Comp = CH 4 i(T , P)
5-12
where (T,P) is the broadening compensation function, T is temperature (K), and P is
atmospheric pressure (kPa). However, because the LI-7700 temperature measurements are
slow, and because of additional complications of laser spectroscopy (described below), the
broadening compensation function is not applied in the number density CH4 data (mmol
m-3). The impact of broadening on flux calculations is accounted for in the WPL-H sensible heat term (see page 6-1), with temperature measured with a sonic anemometer.
Atmospheric pressure and temperature are measured by the LI-7700 and are output with
the data stream. They are used to compute methane mole fraction (μmol/mol, XCH4):
X CH =
4
CH RT
4
P
(
i T , P
)
5-13
where R is the gas constant (8.314 J K-1 mol-1). XCH4 is suitable for calibration, diagnostics,
and atmospheric monitoring, when small and slow changes in temperature are expected.
5-5
6
Application Information
Computing Eddy Covariance Fluxes
Concept of Spectroscopic Effects Overlaying Ideal Gas Law
Effects
An open-path gas analyzer measures the number density of a trace gas (mol m-3), not the
mole fraction. Therefore, changes in gas density between up-draft and down-draft air
parcels due to sensible heat flux and latent heat flux must be accounted for in the eddycovariance flux measurement. This can be done using the well-known Webb-PearmanLeuning (WPL, see Webb et al., 1980) equation. As shown in the previous chapter, the
laser-based LI-7700 uses a single absorption line and WMS technology for making the
measurements. As a result, the measured CH 4 density is not only affected by sensible heat
and latent heat fluxes, but also by spectroscopic effects (e.g., line broadening, etc.) from
changes in temperature, pressure, and water vapor (see Chapter 5 and Rothman et al.,
2009). These effects in LI-7700 follow the Ideal Gas Law in a predictable and consistent
manner. They can be incorporated into the WPL correction via multipliers to WPL terms
because the difference in the slopes between Ideal Gas Law effects and spectroscopic effects
is known from HITRAN and is stable for a given technology (e.g., WMS) and a given
absorption line. Here we present an equation to account for the spectroscopic effects by
adding the additional multipliers in the WPL equations.
In the following sections, only the final equations, with multipliers for each WPL term, are
presented. The detailed derivation of this equation (Patent Pending) will be provided as an
update at a later time.
Important: The mean CH4 mole fraction (μmol mol-1) reported by LI-7700 is
compensated for spectroscopic effects from temperature and pressure and for Ideal Gas
Law effects using “slow” temperature measurements, but not compensated for water vapor.
This number can be used for calibration and diagnostic purposes but should never be used
for eddy-covariance flux calculations. The instantaneous CH 4 number density (mmol m-3)
reported by LI-7700 is not compensated for any of the effects, because fast temperature
and humidity integrated over the optical path are not available. Only this number, the fast
CH4 number density (mmol m-3), should be used for eddy covariance flux computations,
with subsequent WPL corrections and multipliers as shown below.
6-1
Application Information
Formulation for the Propagation of Spectroscopic Effects into
Flux Computation
The spectroscopic effects of pressure and of water vapor broadening can be represented
with a single quantity called equivalent pressure, Pe, defined as Pe = pd + avpv, where pd is
partial pressure of dry air , av is the foreign gas broadening coefficient for water vapor
relative to dry air, and pv is water vapor partial pressure. Total air pressure P can be written
as P = pd + pv. Subtracting P from Pe and rearranging gives Pe = P(1+ vxv), where
v = av – 1, and xv = pv /P is water vapor mole fraction. For the LI-7700, a v is found
experimentally to have a value of 1.46. Thus, the effects of water vapor can be presented as
a perturbation on the total pressure.
To account for spectroscopic effects of temperature (T), pressure and water vapor (Pe) in
the WPL terms (Equation 24 in Webb et al., 1980) for the case of LI-7700 technology, a
modified WPL equation can be written as follows:
qcm
χ
⎡
⎪⎧
Fc = χ ⎨w ' q 'cm + μ
w ' qv ' ⎢1 + 1 − x v αv P Pe
χ
qd
⎪⎩
⎣
(
)
qcm
χT ⎤ ⎪⎫
⎡
⎤
⎥ + (1 + μσ ) w 'T ' ⎢1 + 1 − x v T χ ⎥ ⎬
T
⎣
⎦
⎦ ⎪⎭
(
)
6-1
where gray rectangles show multipliers on WPL terms and non-gray portions are the
traditional WPL equation (Equation 24, Webb et al., 1980). Fc is the final methane flux
corrected for WPL and spectroscopic effects (g m-2s-1); qi is measured mass density (g m-3)
of methane, dry air, or water vapor (subscripts cm, d, or v) respectively; μ = md/mv is the
ratio of molecular weight of dry air to water vapor; = qv/qd; is a dimensionless
correction factor resulting from the effects of temperature, pressure, and water vapor, and
not from temperature-related gas expansion and water-related gas dilution effects,
= (T , P, ) = (T , P ) ,
v
with T =
e
, Pe =
, and = T , P e .
T
Pe
(
)
χ Pe ⎤
⎡
⎢1+ 1 − x v αv P χ ⎥
⎣
⎦
(
)
Equation 6-2 is the latent heat term multiplier.
6-2
6-2
Application Information
χT ⎤
⎡
⎢1 + 1 − x v T χ ⎥
⎣
⎦
(
)
6-3
Equation 6-3 is the sensible heat term multiplier.
Over-bars indicate the mean quantities. The deviation of the instantaneous quantity from
the mean is indicated by a prime.
For typical conditions at or near sea level and for a wide range of air temperatures and
humidities, the first multiplier, , ranges from 0.93 to 1.02, the latent heat term multiplier
(equation 6-2) ranges from 1.40 to 1.45, and the sensible heat multiplier (equation 6-3)
ranges from 1.10 to 1.45. The section below shows the ranges of those values for a wide
range of measurement conditions.
Values of Multipliers to Account for Spectroscopic Effects
The multipliers for equation 6-1 come from a number of spectroscopic effects: changes in
the Boltzmann population distribution of the rotational levels, Doppler and pressure
broadening of individual lines. All of these effects have been calculated below for the
following conditions: 50 to 110 kPa and from -40 to 50 °C.
These calculations are based on absorption profiles run through the modulation/
demodulation algorithm and the predicted responses were collected into a table. The
following tables (Table 6-1 to Table 6-3) give examples of the multiplier values for 80 to
110 kPa and -25 to 50 °C range. Full derivations and high-resolution look-up tables for
these multipliers will be provided as an update at a later time.
Table 6-1. Value for .
Pressure
(kPa)
80
85
90
95
100
105
110
o
-25
0.766
0.809
0.854
0.901
0.950
1.002
1.056
-20
0.770
0.813
0.857
0.904
0.952
1.003
1.057
-10
0.779
0.821
0.865
0.910
0.958
1.008
1.061
Temperature ( C)
0
10
20
0.789
0.800
0.812
0.830
0.841
0.852
0.873
0.883
0.894
0.918
0.928
0.938
0.965
0.974
0.984
1.015
1.022
1.032
1.066
1.073
1.082
30
0.825
0.865
0.906
0.950
0.995
1.042
1.092
40
0.838
0.878
0.919
0.962
1.007
1.054
1.103
50
0.852
0.892
0.933
0.976
1.020
1.067
1.115
6-3
Application Information
Table 6-2. Values for α v P
Pressure
(kPa)
80
85
90
95
100
105
110
χ Pe
.
χ
o
-25
0.402
0.424
0.447
0.469
0.491
0.513
0.534
-20
0.396
0.419
0.441
0.463
0.485
0.506
0.528
-10
0.386
0.408
0.430
0.451
0.472
0.493
0.514
Temperature ( C)
0
10
20
0.376
0.367
0.358
0.398
0.388
0.379
0.419
0.409
0.399
0.440
0.429
0.420
0.461
0.450
0.440
0.482
0.470
0.460
0.502
0.490
0.479
30
0.350
0.370
0.390
0.410
0.430
0.449
0.469
40
0.342
0.362
0.382
0.401
0.421
0.440
0.459
50
0.335
0.354
0.374
0.393
0.412
0.431
0.449
Notice that to get the full water vapor correction, you must multiply this value by (1-xv) and add unity.
Table 6-3. Values for T
Pressure
(kPa)
80
85
90
95
100
105
110
χT
.
χ
-25
0.252
0.216
0.180
0.144
0.109
0.075
0.041
-20
0.275
0.239
0.204
0.169
0.134
0.100
0.066
-10
0.319
0.284
0.249
0.215
0.181
0.148
0.115
Temperature (
0
10
0.362
0.404
0.328
0.370
0.294
0.337
0.260
0.304
0.227
0.272
0.195
0.239
0.162
0.208
o
C)
20
0.444
0.411
0.378
0.346
0.314
0.283
0.252
30
0.483
0.450
0.419
0.387
0.356
0.325
0.294
40
0.520
0.489
0.457
0.426
0.396
0.366
0.336
50
0.558
0.527
0.496
0.466
0.436
0.406
0.377
Notice that to get the full sensible heat term multiplier, one must multiply this value by (1- xv) and add unity.
6-4
Application Information
Flux Computation Algorithm
As a result of the Ideal Gas Law and spectroscopic effects, computing the flux from LI7700 measurements requires the following seven steps, using a 60-minute time interval as
an example:
1.
Compute CH4' covariance with w' using instantaneous CH4 density as reported by
LI-7700 over the 60-minute period,
2.
Measure mean quantities and compute water vapor and sensible heat flux covariances
as required by the WPL correction (Equation 24 in Webb et al., 1980),
3.
Determine mean water vapor mole fraction, xv,
4.
Determine the multiplier from Table 6-1 using the information of mean air
temperature and pressure,
5.
Determine the α v P
6.
Determine the T
7.
Use equation 6-1 to compute the final flux.
χ Pe
multiplier from Table 6-2,
χ
χT
χ
multiplier from Table 6-3,
It may be useful to program this process into the standard flux processing code once, then
to verify the coding by hand calculations for one or two cases, and then just use the same
code for computing final fluxes. This way the above process becomes a mere adjustment of
WPL correction in the flux processing code, and no additional efforts or time investment
is required.
6-5
Application Information
Example of Flux Computation Using Real Field Data
Let's compute the final CH4 flux value for one actual hour of flux measurements conducted
in a Summer 2009 over a maize field at Mead, Nebraska. This experimental site had a
multi-year history of chamber measurements of very small CH4 fluxes (-0.1 to 0.1 mg m -2
h-1 year round). The following conditions were observed over the 11:30 AM hour on
6/29/2009, following Equation 1 member-by-member:
qcm
χ
⎡
⎪⎧
Fc = χ ⎨w ' q 'cm + μ
w ' qv ' ⎢1 + 1 − x v αv P Pe
χ
q
d
⎪⎩
⎣
(
)
qcm
χT ⎤ ⎪⎫
⎡
⎤
⎥ + (1 + μσ ) w 'T ' ⎢1 + 1 − x v T χ ⎥ ⎬
T
⎣
⎦
⎦ ⎪⎭
(
)
6-4, same as equation 6-1
w’q’cm
≈0.97
=-0.468 mg CH4 m -2 h-1
μ
qcm
qd w’qv’
≈1.6077
=1.227 mg CH4 m -3
≈1154 g m -3
=91.04 g m -2 h-1
xv
=0.02
from Table 6-1
as measured in the field with the LI-7700 and sonic
anemometer
as assumed for this example
as measured in the field with the LI-7700
as follows from given T and P
as measured in the field with an LI-7500 and sonic
anemometer
as assumed for this example
≈0.43
=97.7 kPa
≈0.013
=22.25 °C = 295.38 K
=47.63 K m s-1
from Table 6-2
as measured in the field with the LI-7700
as calculated based on xv = 0.02
as measured in the field with the LI-7700
as measured in the field with a sonic anemometer
≈0.34
from Table 6-3
αv P
P
T
w’T’
T
χT
χ
χ Pe
χ
Using the multipliers from Tables 1, 2, and 3, equation 6-4 becomes:
q
q
Fc 0.97 w ' q 'cm cm w ' qv '1 1 0.02 0.43 1 cm w 'T '1 1 0.02 0.34 qd
T
6-5
and then a fairly simple form of the WPL equation, with the multipliers in bold:
6-6
Application Information
q
q
Fc = 0.97 w'q'cm + μ cm w'qv '1.42 + (1+ μ ) cm w'T '1.33 qd
T
6-6
Equation 6-6 is the standard WPL equation (Equation 24 in Webb et al., 1980) with
three multipliers in bold to account for spectroscopic effects.
Finally, after plugging actual numbers into equation 6-6, the following fluxes are computed:
raw uncorrected flux = -0.47 mg CH4 m -2 h-1; traditional WPL-1980 corrected flux = -0.13
mg CH4 m -2 h-1; and WPL-1980 fluxes corrected using the multipliers = 0.02 mg CH4 m -2
h-1.
6-7
Application Information
Bandwidth
The output rate setting determines the signal averaging done by the digital filter. To avoid
aliasing (only a concern for co-spectra, not for fluxes), the LI-7700 output rate should be set
at a frequency greater than or equal to 2 times the desired bandwidth, also referred to as the
Nyquist frequency (e.g., for a bandwidth of 20 Hz, set the output rate to 40 Hz). This is
set in the Manual Controls window.
Bandwidth is the frequency at which the indicated amplitude is 0.707 of the real amplitude.
Actual concentration
Concentration
Measured concentration
.707
Time
Bandwidth is useful for characterizing real-world behavior in which there are fluctuating
gas concentrations. Given a sinusoidal oscillation of concentration, the instrument’s ability
to measure the full oscillation amplitude diminishes as the oscillation frequency increases.
6-8
Application Information
Determining Mirror Cleaner Settings
The mirror cleaner and heater settings are designed to provide the flexibility to accommodate a wide range of conditions. As such, inappropriate settings could result in excessive
energy consumption, rapid use of washer fluid, and lost data. Therefore, it is essential that
you select settings that are optimal for your environment. Below, we discuss some relevant
considerations and recommend some starting points for determining which settings are
best for your application/environment. It is best to experiment a little to find out what is
best for your environment/application.
Here are some general guidelines that are intended to serve as a starting place:
Scenario 1: If you expect fouling of the mirrors to result from slow dust accumulation (as
opposed to bird droppings, rain, snow, water droplets, or blowing sand) use the following
settings:
Signal Strength Setting:
Start Time:
Stop Time:
Repeat Check Every:
Spray Duration:
10%
00:00
00:00
01:00
20 Sec
The LI-7700 will check the signal strength (RSSI) every hour. If the RSSI is below 10%, the
analyzer will initiate a 30 second cleaning cycle, which is 20 seconds of spray + spin then
10 seconds of spin only. Disadvantages: If the mirror becomes very dirty and cannot be
cleaned, the washer fluid reservoir will become empty after 45 cleaning cycles. If the RSSI is
low because of rain, the cleaning cycle will activate. Therefore, these settings are not
recommended in environments where frequent rain is expected.
Scenario 2: If you expect fouling to result from frequent ephemeral interruptions, such as
snowflakes, bugs, or water droplets (not rain), but you do not expect much dust accumulation or rain showers, start with the following settings:
Signal Strength Setting:
Start Time:
Stop Time:
Repeat Check Every:
Spray Duration:
10%
00:00
00:00
00:01
0 Sec
The LI-7700 will check the signal strength (RSSI) every minute. If snowflakes or bugs drive
the RSSI down, the LI-7700 will spin the mirror for 10 seconds. No washer fluid will be
pumped. Disadvantages: if bird droppings foul the mirror, merely spinning the mirror
probably will not clear it, and the mirror will spin for 10 seconds every minute until the
6-9
Application Information
debris is removed. Falling rain could also cause the mirror to spin for 10 seconds every
minute. Therefore, refrain from using these settings in regions that experience frequent
rain.
Scenario 3: If you expect fouling to result from bird droppings or rapid periodic dust accumulation, use the following settings:
Signal Strength Setting:
Start Time:
Stop Time:
Repeat Check Every:
Spray Duration:
10%
01:00
01:30
00:05
30 Sec
The LI-7700 will check the signal strength (RSSI) every 5 minutes between 1:00 and 1:30
a.m. If it is below 10%, the cleaning cycle will be 30 seconds of spray + spin, then 10 seconds of spin only. It will carry out this process 6 times between 01:00 and 01:30. Disadvantages: When the mirror becomes fouled (enough to drive the RSSI below 10%), data
could be lost until the mirror is cleaned, which will begin at 1:00 am.
Determining Mirror Heater Settings
The mirror heaters serve to remove/prevent the buildup of condensation on the mirrors.
Determining what mirror settings are best for your application/environment is best done
with some experimentation. The following guidelines are intended to serve as a starting
point:
1.
Make an estimate of when condensing conditions begin and end, and set the mirror
heater start and stop times accordingly. Refer to a weather forecast or recent meteorological records. It is easier to prevent condensation than it is to remove condensation, so set the heaters to preempt the formation of dew.
2.
Estimate how far below the dew point temperature the actual temperature will fall.
Use this to determine power settings and upper mirror ambient offset. If the predicted temperature is only a little below the dew point, a power settings of <10% with
an ambient offset (upper mirror) of 1 °C may work fine. Power settings close to 100%
should be reserved for extreme conditions where ice buildup is expected.
3.
Check your data. If you find data loss or reduced RSSI readings during condensing
conditions, it will be worthwhile to boost the power settings or lengthen the time
window during those periods.
Mirror heater power consumption is linear with the setting. Thus, a setting of 100% require about 8W, whereas a setting of 10% requires about 0.8W.
6-10
Application Information
Power Requirements
The LI-7700 uses about 8 watts during normal operation, but when accessories and mirror
heaters are used, power requirements could be up to or greater than 41 watts. The following table can be used to determine how much power is required in a variety of configurations:
CH4
Washer Mirror Heaters LI-7550
Analyzer Assembly Upper Lower
Normal
Operation
8
During
Cleaning
Cycle*
8
8
8
8
Mirror
Heaters
On†
Power
Consumption (W)
8
8
10
18
16
10
26
8
0 to 7.5
8
0 to 7.5
0 to 7.5
8
0 to 7.5
0 to 7.5
10
18 to 33
0 to 7.5
0 to 7.5
10
26 to 41
8
8
8 to 15.5
8 to 23
* Cleaning cycle duration from 10 to 120 seconds. Cleaning frequency and duration are user-settable.
†
Power used for mirror heaters is from 0 to 7.5 W each, linear with power setting.
Using a Secondary Washer Fluid Reservoir
The 7700-101 is equipped with an inlet connection that can be used to attach a secondary
washer reservoir. In environments where the washer fluid is used quickly, a secondary
washer reservoir can be used to refill the 7700-101 reservoir. This will require a pump or
siphon to transfer fluid from the secondary reservoir to the 7700-101 reservoir.
References:
Gharavi, M., and Buckley, S. G. 2005. Diode laser absorption spectroscopy measurement
of linestregths and pressure broadening coefficients of the methane 2v3 band at elevated
temperatures. Journal of Molecular Spectroscopy, 229: 78-88.
Rothman L.S., Gordon I.E., Barbe A., Benner D.C., Bernath P.F., et al. 2009. The
HITRAN 2008 molecular spectroscopic database. Journal of Quantitative Spectroscopy
& Radiative Transfer, 110: 533-572.
Webb, E. K., Pearman G., and Leuning R. 1980. Correction of flux measurements for
density effects due to heat and water vapor transfer, Q. J. Roy. Meteorol. Soc., 106: 85-100.
6-11
7
Advanced Operation
This section describes a variety of diagnostic and maintenance procedures, including how
to set the instrument zero and span. It also provides some specific information about how
to determine what instrument settings are appropriate for different environments.
Diagnostics
Laser Temperature Control
During normal operation, the instrument uses an automatic control loop to maintain the
laser temperature, which in turn keeps the laser wavelength tuned to the absorptance
feature of interest. In the LI-7700, the laser scans a sealed vessel of methane along with the
open path cavity. The results are displayed on the Diagnostics Page of the Main View:
The above display indicates normal operation by the following features:
•
A standard bell shaped curve is seen for both the sample and reference paths
7-1
Application Information
•
•
Both are overlayed nicely, with the peak at or very near the zero point on the
horizontal axis
The waveform has sufficient depth (e.g., not too shallow vertically)
The two status indicators located in the status panel above the chart display should further
support this state. Both the Laser Temperature and Reference Lock indicators should
show green. If either or both are red, then the instrument is not functioning normally and
it may be necessary to manually adjust the laser temperature parameters.
Opening the Laser Temperature Control Dialog
1.
Place the mouse pointer over the red light indicator on the status panel and click the
left mouse button (the indicator must be red to complete this action).
-or2.
Press the Ctrl, Alt and L keys simultaneously. This can be done at any time when you
are connected to an instrument.
The Laser Temperature Control dialog will open:
It is only possible to open this dialog when the application is connected to an instrument.
As the dialog indicates, there are two temperature parameters that may be manipulated.
Laser Cooler temperature is the primary one and should be altered first. In order to change
the value the Line Lock setting must be changed from “Automatic” to “Manual”, as shown
below.
7-2
Application Information
This will allow you to set the temperature manually. The normal scenario for performing
this operation is to watch the diagnostics page and see how the waveform changes as the
parameter is increased or decreased.
Manual Line Lock Example
In this example, the automatic line lock was disabled and the laser temperature was manually driven from a value of 10.0 to 16.0. This resulted in the following waveform display:
At this point, the desired positions could be either to the right or to the left. Since the line
lock temperature value was known to be higher, the values were incremented in single digits (e.g., 11, 12, …, 16), and the following series of images were taken:
7-3
Application Information
7-4
Application Information
Re-enabling Automatic Line Lock
As the previous images show, the waveform is gradually shifting from right to left as the
temperature parameter is increased from 10.0 to 16.0 °C. At this point, since the top of the
bell shape is relatively close to the zero point on the horizontal axis, you can attempt to
have the instrument re-lock automatically by setting the Line Lock parameter back to
“automatic”. This should cause the wave to slide further to the right or left until the peak is
at or very near the zero point. If this does in fact occur, the relocking was successful and the
dialog may be closed. If not, repeat the process, or simply restart the instrument.
7-5
Application Information
Maintenance
Calibration
The overall accuracy of the LI-7700 depends upon its calibration. Always use quality zero
and span gases with CH4 accuracy greater than 1% and 0 ppm Volatile Organic Compounds (VOC free). See the list of suppliers (page 8-10) for more information. Check the
readings every 6 months.
Performing a Zero Calibration
To zero the LI-7700:
1.
Connect the LI-7700 to a power supply and a computer running the LI-7700 software. Launch the LI-7700 software and connect with the instrument.
2.
Remove the radiation shield (if installed) and install the calibration shroud. Ensure
that it seals around the top and bottom openings.
3.
Connect the “zero gas” to the shroud fittings.
4.
Flow the desired gas through the shroud. Allow from 10 to 30 minutes for equilibration, depending on flow rate.
5.
Click the Zero CH4 button in the calibration frame. When the instrument begins
the zero operation, the panel will update to reflect the activity. The Zero CH4 will
change to “Abort”. Clicking Abort terminates the zero procedure. It usually takes
about 10 seconds to zero. If it takes significantly longer, check for leaks and verify the
calibration tank pressure.
6.
When the instrument completes the zero operation, a dialog box will open. You must
choose either to apply the new calibration value or revert to the previous calibration
value. If the application is closed or if the LI-7700 is powered off before a confirmation command is received the new calibration will not be applied.
Performing a Span Calibration
Performing a span is essentially the same as a zero, except that you must flow the span gas
through the optical path and enter the span gas concentration in parts per million (ppm).
Once that is done and the span gas concentration is stable, click the Span CH4 button.
The instrument response will be similar to that for setting the zero.
7-6
Application Information
Factory Reset
The Factory Reset button in the main view will restore the original factory zero and span
settings. Use this only if you attempt to set the zero and span, but are unable to complete
the procedure for some reason or another, or if you complete an attempted calibration, but
prefer to use the factory zero and span settings.
Changing the Internal Desiccant Bottle
There is one internal desiccant bottle in the LI-7700. The desiccant cap is above the circular plug located on the bottom of the top dome of the analyzer between two spars (see
below). The desiccant bottle should be changed annually when the LI-7700 is used in humid environments. Desiccant bottles and recharge kits are available from LI-COR, see
page 8-9.
In the Calibration frame in the Main View of the LI-7700 software, there is a field that
reads “Optics RH:”. Normally this should be near zero. If the indicator turns from green
to red (indicating the optics RH: >30%), then it is time to change the desiccant. To
change the desiccant:
1.
Remove the setscrew that secures the desiccant plug. Insert the knurled screw from
the spares kit into the desiccant cover. Using your fingers or a pair of pliers, remove
the desiccant cover.
2.
Remove the seal from the top of the replacement desiccant bottle. Insert the bottle cap first and replace the cover. Press firmly to secure the desiccant cover and replace the setscrew. Hint: a droplet of saliva or dish soap applied to the o-rings can ease
insertion of the desiccant cover.
7-7
Application Information
Over time, the “Optics RH:” should approach zero. This may take several minutes to several hours, depending on the humidity level. There should be no need to perform any
other maintenance procedures (e.g., zero or span) after this.
7-8
Application Information
Changing the Thermocouple
The fine wire thermocouple should be replaced if the wire is broken or if it reads incorrectly. One spare thermocouple is included in the spares kit, and others can be purchased
from LI-COR Biosciences (p/n 9977-038). To replace the thermocouple:
1.
Fully loosen the two screws (#1 Philips) that secure the thermocouple assembly to the
bottom of the upper housing. The screws will remain in the thermocouple base.
2.
Grasp the thermocouple housing and pull it straight out. It should slide out fairly
easily.
3.
Insert the new thermocouple. Do not force it in, and be sure the bend is directed toward the optical path. Handle the thermocouple carefully to protect the fine wires.
4.
Replace the two screws. Connect with the LI-7700 and verify that the temperature
readings are correct.
7-9
Application Information
Changing the Fuse
The LI-7700 fuse is enclosed within the knurled fuse cover on the connection panel. One
extra 250V type F 5.0 Amp fuse (p/n 438-09800) is included in the spares kit. To replace
the fuse, remove the fuse cover (located on the connection panel, see below) and pull out
the old fuse. Insert the replacement fuse and reattach the fuse cover.
Networking
The LI-7700 supports IPv4 and IPv6. IPv4 is the first Internet protocol to be widely used.
It is nearly 20 years old and will be superseded by IPv6. IPv6 provides many advantages,
one of which is that is allows for substantially more IP address. This will help accommodate the growing number of devices that are connected to the Internet.
Enabling IPv6 on Windows XP
Microsoft® Windows XP includes IPv6, however it is not enabled by default. Note:
Windows Vista and 7 have IPv6 enabled by default. The following steps will install IPv6 on
Windows XP (administrative privileges may be required):
1.
Click the Start menu, and then click All Programs. Click Accessories, and then
click Command Prompt.
2.
At the command prompt, type: ipv6 install and press the Enter key.
Finding your LI-7700’s IPv4 Address
The LI-7700 IPv4 Address may need to be entered manually in rare cases. It is printed on a
sheet of paper that is included with the LI-7700 shipping materials.
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Application Information
The LI-7700 Finder Application
The LI-7700 Finder provides access to internal LI-7700 settings. It also is used to set the
LI-7550 clock. While it provides access to advanced settings, many of these settings should
only be changed in consultation with LI-COR Biosciences technical support personnel.
Upon launching the application, you will see a list of all LI-7700s and LI-7550s on your
local network.
When you select an LI-7700, you can select Watch LI-7700, or when you select an
LI-7550, you can choose Config LI-7550.
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Application Information
Selecting Watch LI-7700 opens a variables window:
This displays numerous parameters used by the LI-7700. Along the bottom of the window
are nine buttons, which are described below:
Click the Wave button:
The window above shows the waveform. It is identical to the waveform displayed in the
Diagnostic Page 1 tab on the Main View.
7-12
Application Information
Click the DC button:
This window shows the un-inverted measurement of the sample and reference.
Click the Wide Scan button:
This window can be used to gather diagnostic information. After performing a wide scan
you either must select “Rollback” in the Factory Settings dialog or restart the instrument
to restore normal operation.
Click the Laser Temp… button:
The laser temperature control dialog is similar to the Laser Temperature control described
above in the Manual Line Lock example (page 7-3).
7-13
Application Information
Click the Cal… button:
This advanced calibration tab provides access to many of the same calibration functions
available in the Main View.
Click the Factory… button:
The window above is used to perform diagnostic checks. Do not change any settings in this
window unless in consultation with LI-COR Biosciences technical support.
7-14
Application Information
Click the Heaters… button:
Provides access to mirror heater controls.
Click the Clock… button:
Advanced clock setting. This is where you set the LI-7550 clock.
7-15
Application Information
Click the Network… button:
This window allows you to change the instrument name and network settings.
7-16
Application Information
Communications Grammar
Introduction
This section describes the protocol used by the LI-7700 to communicate via RS-232 and
Ethernet for both configuration and data output purposes. Commands sent to the
LI-7700 have a certain structure that must be followed, and data sent by the LI-7700
comes packaged in a particular way.
When you communicate with the LI-7700 with a Transmission Control Protocol (TCP)
connection, the LI-7700 address should be in the form:
XXX.XXX.XXX.XXX:YYYY
where XXX represents an integer number from 0-255 and YYYY represents the port
number. All LI-7700s use the port number 7700 by default.
LI-7700 Communications
The configuration grammar used to communicate with the LI-7700 is based upon the
eXtensible Markup Language (XML). XML relies on the use of tags to “markup”, or give
structural rules to a set of data.
A tag is a descriptive identifier, enclosed between a less than (<) and greater than (>) symbol, used in part to describe a piece of data. For example, <NAME> is a tag that describes
someone’s name. Each tag must have a corresponding end tag, denoted by ‘/’. Extending
the example above, the end tag of <NAME> is </NAME>.
Elements are the basic unit of XML content. An element consists of a start tag and an end
tag, and everything in between. For example, consider the following element:
<NAME>Jane</NAME>.
In this example, <NAME> (start tag) and </NAME> (end tag) comprise the markup,
and “Jane” comprises the data.
Elements can also contain other elements other than data.
<NAME>
<FIRST>Jane</FIRST>
<LAST>Smith</LAST>
</NAME>
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Application Information
In this example, the outermost element <NAME> encompasses two other elements that
contain data. All elements combined make up the XML document.
Element Descriptions
The following types of data are used in XML grammar:
{val | val | val | …}
{bool}
{float}
{int}
{string}
The value will be a member of the specified set. The “|” means
“or”.
Boolean values, TRUE | FALSE.
Floating point values in decimal or exponential notation.
Integer
String
Grammar
A full LI-7700 XML file will resemble the following:
<licor>
<li7700>
<ver>{string}</ver>
<name>{string}</name>
<serialnumber>{string}</serialnumber>
<ipaddress>{string}</ipaddress>
<output>
<rate>{0|1|2|5|10|20|40}</rate>
<waveforms>{true|false}</waveforms>
<status>{true|false}</status>
<dataclock>{true|false}</dataclock>
</output>
<box>
<output>
<data>
<msec>{true|false}</msec>
<seconds>{true|false}</seconds>
<nanoseconds>{true|false}</nanoseconds>
<diag>{true|false}</diag>
<ch4>{true|false}</ch4>
<ch4d>{true|false}</ch4d>
<temp>{true|false}</temp>
<pressure>{true|false}</pressure>
<rssi>{true|false}</rssi>
<droprate>{true|false}</droprate>
<aux1>{true|false}</aux1>
<aux2>{true|false}</aux2>
<aux3>{true|false}</aux3>
<aux4>{true|false}</aux4>
<aux5>{true|false}</aux5>
7-18
Application Information
<aux6>{true|false}</aux6>
<aux7>{true|false}</aux7>
<aux8>{true|false}</aux8>
<auxtc1>{true|false}</auxtc1>
<auxtc2>{true|false}</auxtc2>
<auxtc3>{true|false}</auxtc3>
<chk>{true|false}</chk>
</data>
<waveforms>{true|false}</waveforms>
<status>{true|false}</status>
<dataclock>{true|false}</dataclock>
</output>
<usb>
<data>
<msec>{true|false}</msec>
<seconds>{true|false}</seconds>
<nanoseconds>{true|false}</nanoseconds>
<diag>{true|false}</diag>
<ch4>{true|false}</ch4>
<ch4d>{true|false}</ch4d>
<temp>{true|false}</temp>
<pressure>{true|false}</pressure>
<rssi>{true|false}</rssi>
<droprate>{true|false}</droprate>
<aux1>{true|false}</aux1>
<aux2>{true|false}</aux2>
<aux3>{true|false}</aux3>
<aux4>{true|false}</aux4>
<aux5>{true|false}</aux5>
<aux6>{true|false}</aux6>
<aux7>{true|false}</aux7>
<aux8>{true|false}</aux8>
<auxtc1>{true|false}</auxtc1>
<auxtc2>{true|false}</auxtc2>
<auxtc3>{true|false}</auxtc3>
<chk>{true|false}</chk>
<date>{true|false}</date>
<time>{true|false}</time>
</data>
<status>{same_file|separate_file|off}</status>
<split>{0|15|30|60|90|120|180|240|1440}</split>
</usb>
</box>
<cfg>
<temprange>{low|high}</temprange>
<clock>
<time>{string:00:00:00}</time>
<date>{string:1970-01-01}</date>
<zone>{enter your time zone}</zone>
<ptp>{auto|slaveonly|preferred}</ptp>
</clock>
<network>
<name>{string:ch4-xxxx}</name>
<configuration>{auto|manual}</configuration>
<ipaddress>{int.int.int.int}</ipaddress>
<netmask>{int.int.int.int}</netmask>
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Application Information
<gateway>{int.int.int.int}</gateway>
</network>
<aux1>
<type>{poly|steinhart|linear-rt}</type>
<a0>{float:0}</a0>
<a1>{float:1}</a1>
<a2>{float:0}</a2>
<a3>{float:0}</a3>
</aux1>
<aux2>
<type>{poly|steinhart|linear-rt}</type>
<a0>{float:0}</a0>
<a1>{float:1}</a1>
<a2>{float:0}</a2>
<a3>{float:0}</a3>
</aux2>
<aux3>
<type>{poly|steinhart|linear-rt}</type>
<a0>{float:0}</a0>
<a1>{float:1}</a1>
<a2>{float:0}</a2>
<a3>{float:0}</a3>
</aux3>
<aux4>
<type>{poly|steinhart|linear-rt}</type>
<a0>{float:0}</a0>
<a1>{float:1}</a1>
<a2>{float:0}</a2>
<a3>{float:0}</a3>
</aux4>
<aux5>
<type>{poly|steinhart|linear-rt}</type>
<a0>{float:0}</a0>
<a1>{float:1}</a1>
<a2>{float:0}</a2>
<a3>{float:0}</a3>
</aux5>
<aux6>
<type>{poly|steinhart|linear-rt}</type>
<a0>{float:0}</a0>
<a1>{float:1}</a1>
<a2>{float:0}</a2>
<a3>{float:0}</a3>
</aux6>
<aux7>
<type>{poly|steinhart|linear-rt}</type>
<a0>{float:0}</a0>
<a1>{float:1}</a1>
<a2>{float:0}</a2>
<a3>{float:0}</a3>
</aux7>
<aux8>
<type>{poly|steinhart|linear-rt}</type>
<a0>{float:0}</a0>
<a1>{float:1}</a1>
<a2>{float:0}</a2>
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Application Information
<a3>{float:0}</a3>
</aux8>
<dac1>
<set>{float:0;-5...5}</set>
<src>{set|ch4d|ch4|temp|pressure|rssi|droprate|aux1|aux2|aux3|aux4|aux5|aux6|aux7|aux8
|auxtc1|auxtc2|auxtc3}</src>
<low>{float:0}</low>
<high>{float:0}</high>
</dac1>
<dac2>
<set>{float:0;-5...5}</set>
<src>{set|ch4d|ch4|temp|pressure|rssi|droprate|aux1|aux2|aux3|aux4|aux5|aux6|aux7|aux8
|auxtc1|auxtc2|auxtc3}</src>
<low>{float:0}</low>
<high>{float:0}</high>
</dac2>
<dac3>
<set>{float:0;-5...5}</set>
<src>{set|ch4d|ch4|temp|pressure|rssi|droprate|aux1|aux2|aux3|aux4|aux5|aux6|aux7|aux8
|auxtc1|auxtc2|auxtc3}</src>
<low>{float:0}</low>
<high>{float:0}</high>
</dac3>
<dac4>
<set>{float:0;-5...5}</set>
<src>{set|ch4d|ch4|temp|pressure|rssi|droprate|aux1|aux2|aux3|aux4|aux5|aux6|aux7|aux8
|auxtc1|auxtc2|auxtc3}</src>
<low>{float:0}</low>
<high>{float:0}</high>
</dac4>
<dac5>
<set>{float:0;-5...5}</set>
<src>{set|ch4d|ch4|temp|pressure|rssi|droprate|aux1|aux2|aux3|aux4|aux5|aux6|aux7|aux8
|auxtc1|auxtc2|auxtc3}</src>
<low>{float:0}</low>
<high>{float:0}</high>
</dac5>
<dac6>
<set>{float:0;-5...5}</set>
<src>{set|ch4d|ch4|temp|pressure|rssi|droprate|aux1|aux2|aux3|aux4|aux5|aux6|aux7|aux8
|auxtc1|auxtc2|auxtc3}</src>
<low>{float:0}</low>
<high>{float:0}</high>
</dac6>
<heater>
<top>
<heaterpower>{integer:100;0...100}</heaterpower>
<control>{auto|on|off}</control>
<ontime>{HH:MM}</ontime>
<offtime>{HH:MM}</offtime>
<deltat>{float:0;-5...5}</deltat>
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Application Information
</top>
<bottom>
<heaterpower>{integer:100;0...100}</heaterpower>
<control>{auto|on|off}</control>
<ontime>{HH:MM}</ontime>
<offtime>{HH:MM}</offtime>
<signalstrengthlevel>{integer:40;0...100}</signalstrengthlevel>
</bottom>
</heater>
<linelock>
<lasercooler>
<control>{auto|manual|daccount}</control>
<temp>{float:25;0...50}</temp>
<daccount>{integer:0;0...65535}</daccount>
</lasercooler>
<laserblock>
<control>{off|on|daccount}</control>
<temp>{float:22;0...50}</temp>
<daccount>{integer:0;0...65535}</daccount>
</laserblock>
</linelock>
<spinmirror>
<control>{auto|on|off}</control>
<ontime>{HH:MM}</ontime>
<offtime>{HH:MM}</offtime>
<duration>{integer:30;0...300}</duration>
<repeatinterval>{HH:MM}</repeatinterval>
<signalstrengthlevel>{integer:40;0...100}</signalstrengthlevel>
</spinmirror>
<sdmaddress>{integer:0;0...15}</sdmaddress>
</cfg>
<cal>
<ch4zero>{float:0}</ch4zero>
<ch4span>{float:1}</ch4span>
<ch4spanconc>{float:2}</ch4spanconc>
<ch4lastzero>{YYYY-MM-DD HH:MM:SS.SS}</ch4lastzero>
<ch4lastspan>{YYYY-MM-DD HH:MM:SS.SS}</ch4lastspan>
<history>
<record>
<time>{YYYY-MM-DD HH:MM:SS.SS}</time>
<type>{string}</type>
<ch4zero>{float:0}</ch4zero>
<ch4span>{float:1}</ch4span>
</record>
<record>
<time>{YYYY-MM-DD HH:MM:SS.SS}</time>
<type>{string}</type>
<ch4zero>{float:0}</ch4zero>
<ch4span>{float:1}</ch4span>
</record>
<record>
<time>{YYYY-MM-DD HH:MM:SS.SS}</time>
<type>{string}</type>
<ch4zero>{float:0}</ch4zero>
<ch4span>{float:1}</ch4span>
</record>
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Application Information
<record>
<time>{YYYY-MM-DD HH:MM:SS.SS}</time>
<type>{string}</type>
<ch4zero>{float:0}</ch4zero>
<ch4span>{float:1}</ch4span>
</record>
<record>
<time>{YYYY-MM-DD HH:MM:SS.SS}</time>
<type>{string}</type>
<ch4zero>{float:0}</ch4zero>
<ch4span>{float:1}</ch4span>
</record>
<record>
<time>{YYYY-MM-DD HH:MM:SS.SS}</time>
<type>{string}</type>
<ch4zero>{float:0}</ch4zero>
<ch4span>{float:1}</ch4span>
</record>
<record>
<time>{YYYY-MM-DD HH:MM:SS.SS}</time>
<type>{string}</type>
<ch4zero>{float:0}</ch4zero>
<ch4span>{float:1}</ch4span>
</record>
</history>
</cal>
<cmd>
<poll>{true|false}</poll>
<ch4zero>{true|false}</ch4zero>
<ch4span>{true|false}</ch4span>
<calcommit>{true|false}</calcommit>
<calrollback>{true|false}</calrollback>
<calabort>{true|false}</calabort>
<logusbstart>{true|false}</logusbstart>
<logusbstop>{true|false}</logusbstop>
<reboot>{true|false}</reboot>
<polltest>{true|false}</polltest>
<linelock>{true|false}</linelock>
</cmd>
<cpld>
<ver>{string}</ver>
<motor>
<control>{integer:0}</control>
<desired_pos>{integer:0}</desired_pos>
<actual_pos>{integer:0}</actual_pos>
</motor>
</cpld>
<factory>
<serialnumber>{string:ch4-XXXX}</serialnumber>
<lasermoddepth>{integer:7000}</lasermoddepth>
<laserstarttemp>{float:22;0...50}</laserstarttemp>
<blockstarttemp>{float:30;0...50}</blockstarttemp>
<blockstarttemplowrange>{float:5;0...50}</blockstarttemplowrange>
<rssidropthresh>{float:1;0...100}</rssidropthresh>
<pzero>{float:0}</pzero>
<pspan>{float:1}</pspan>
7-23
Application Information
<samplegain>{integer:0;0...2147483647}</samplegain>
<refgain>{integer:0;0...2147483647}</refgain>
<mirrorpos>{integer:0;0...1023}</mirrorpos>
<offset1>{integer:0;0...65535}</offset1>
<delta1>{integer:0;0...65535}</delta1>
<offset2>{integer:0;0...65535}</offset2>
<delta2>{integer:0;0...65535}</delta2>
<dither>{integer:0;0...65535}</dither>
<sampledcoffset>{integer:0;0...65535}</sampledcoffset>
<sampleacoffset>{integer:0;-32768...32767}</sampleacoffset>
<sampleopticaloffset>{integer:0;-32768...32767}</sampleopticaloffset>
<cmd>
<commit>{true|false}</commit>
<rollback>{true|false}</rollback>
</cmd>
</factory>
</li7700>
</licor>
Configuration File Grammar
Configuration files are constructed when you save an instrument configuration (see page
2-15). You can view or edit the configuration grammar by opening the configuration file
in an HTML editor or text editor. Below is an example of a typical configuration file with
hypothetical values for elements:
<licor>
<li7700>
<box></box>
<cfg>
<sdmaddress>0</sdmaddress>
<aux1>
<type>poly</type>
<a0>0</a0>
<a1>1</a1>
<a2>0</a2>
<a3>0</a3>
</aux1>
<aux2>
<type>poly</type>
<a0>0</a0>
<a1>1</a1>
<a2>0</a2>
<a3>0</a3>
</aux2>
<aux3>
<type>poly</type>
<a0>0</a0>
<a1>1</a1>
<a2>0</a2>
<a3>0</a3>
</aux3>
<aux4>
<type>poly</type>
7-24
Application Information
<a0>0</a0>
<a1>1</a1>
<a2>0</a2>
<a3>0</a3>
</aux4>
<aux5>
<type>poly</type>
<a0>0</a0>
<a1>1</a1>
<a2>0</a2>
<a3>0</a3>
</aux5>
<aux6>
<type>poly</type>
<a0>0</a0>
<a1>1</a1>
<a2>0</a2>
<a3>0</a3>
</aux6>
<aux7>
<type>poly</type>
<a0>0</a0>
<a1>1</a1>
<a2>0</a2>
<a3>0</a3>
</aux7>
<aux8>
<type>poly</type>
<a0>0</a0>
<a1>1</a1>
<a2>0</a2>
<a3>0</a3>
</aux8>
<heater>
<top>
<heaterpower>25</heaterpower>
<control>off</control>
<deltat>5</deltat>
<ontime>03:00</ontime>
<offtime>22:00</offtime>
</top>
<bottom>
<heaterpower>25</heaterpower>
<control>off</control>
<signalstrengthlevel>35</signalstrengthlevel>
<ontime>01:00</ontime>
<offtime>22:00</offtime>
</bottom>
</heater>
<linelock>
<lasercooler>
<control>auto</control>
<temp>16.3</temp>
</lasercooler>
<laserblock>
7-25
Application Information
<control>on</control>
<temp>30</temp>
</laserblock>
</linelock>
<spinmirror>
<control>off</control>
<ontime>00:00</ontime>
<offtime>00:00</offtime>
<duration>70</duration>
<repeatinterval>00:03</repeatinterval>
<signalstrengthlevel>100</signalstrengthlevel>
</spinmirror>
<dac1>
<set>0</set>
<src>ch4</src>
<low>0</low>
<high>5</high>
</dac1>
<dac2>
<set>0</set>
<src>temp</src>
<low>0</low>
<high>0</high>
</dac2>
<dac3>
<set>0</set>
<src>pressure</src>
<low>0</low>
<high>0</high>
</dac3>
<dac4>
<set>0</set>
<src>rssi</src>
<low>0</low>
<high>0</high>
</dac4>
<dac5>
<set>0</set>
<src>rssi</src>
<low>0</low>
<high>0</high>
</dac5>
<dac6>
<set>0</set>
<src>rssi</src>
<low>0</low>
<high>0</high>
</dac6>
</cfg>
</li7700>
</licor>
7-26
Application Information
Sending Commands
Example commands are presented below.
To request a data record:
<licor><li7700><cmd><poll>true</poll></cmd></li7700></licor>
This will retrieve a complete data record.
To change the mirror heater settings:
<licor><li7700><cfg>
<heater>
<top>
<control> on | off | auto </control>
<deltat> {float (-5.0 – 5.0)} </deltat>
<heaterpower>{Int}</heaterpower>
<ontime>{HH:MM}</ontime>
<offtime>{HH:MM}</offtime>
</top>
<bottom>
<heaterpower>{Int}</heaterpower>
<control>{auto | on | off}</control>
<signalstrenghlevel>{Int}</signalstrengthlevel>
<ontime>{HH:MM}</ontime>
<offtime>{HH:MM}</offtime>
</bottom>
</heater>
</cfg></li7700></licor>
This would change the mirror heater settings to whichever values you specify.
To set the temperature range to the 0C...50C range:
<licor><li7700><cfg><temprange>high</temprange></cfg></li7700></licor>
To set the temperature range to the -25C...25C range:
<licor><li7700><cfg><temprange>low</temprange></cfg></li7700></licor>
To force the instrument to re-linelock:
<licor><li7700><cmd><linelock>true</linelock></cmd></li7700></licor>
7-27
8
Appendices
Appendix A. Specifications
LI-7700 Open Path CH4 Analyzer
Calibration Range:
0-40 ppm @ 25 °C
0-25 ppm @ -25 °C
Bandwidth:
0, 1, 2, 5, 10, or 20 Hz
Linearity:
Within 1% of reading across full calibration range
Resolution:
5 ppb (RMS @ 10 Hz, typical ambient levels)
Operating Temperature Range:
Operating Pressure Range:
-25 °C to 50 °C
50 to 110 kPa
Detection Method:
Wavelength Modulation Spectroscopy, 2f
Detection
Ethernet
Data Communication:
Inputs:
Ethernet, 4 Analog Inputs (single ended, ±5V, 16
bit), 3 type E thermocouple
Power Requirements:
10.5 to 30 VDC
Power Consumption:
8 Watts
Weight:
5.2 kg (11.5 lbs.)
LI-7550 Analyzer Interface Unit
Data Storage:
Removable USB Storage. 4 GB provided, (>1 TB
max; expandable with user-supplied industrial grade
USB Flash Drive)
Data Communication:
Ethernet
Synchronous Devices for Measurement (33.3 Hz)
RS-232 (57,600 baud, 20 records per second)
6 Digital-to-Analog Converters (0-5V, 300 Hz)
Inputs:
Ethernet, 4 Analog Inputs (differential, ±5V, 16
bit)
8-1
Appendices
8-2
Operating Temperature Range:
Power Requirements:
-25 °C to 50 °C
10.5 to 30 VDC
Power Consumption:
10W nominally
Dimensions:
35 30 15 cm (13.8 12 6 in.) external
dimensions
Weight:
4.4 kg (10 lbs)
Appendices
Appendix B. Heating in the Optical Path
High-speed air temperature fluctuations inside the LI-7700 sampling path and resulting
sensible heat fluxes were examined during field experiments in February and March 2008
near Mead, Nebraska. The experimental site has a long history of chamber measurements
of very small CH4 fluxes (-0.1 to 0.1 mg m-2 h-1 year round), and provided a good opportunity to check near-zero fluxes using the eddy covariance flux approach with a normal and
an artificially heated LI-7700. Cold weather and near-zero methane fluxes constituted a
worst-case scenario for testing instrument heating affects on measured fluxes.
An array of 5 fine-wire thermocouples (0.002", Campbell Scientific, Logan Utah) was installed inside the LI-7700 path, 5 mm, 14 cm and 24.5 cm above the bottom mirror, and
14 cm and 5 mm below the top mirror. Ambient heat flux was computed using a similar
thermocouple installed upwind from the LI7700. All data were collected at a 10-Hz rate.
Figure 8-1 (a) and (b) below show that sensible heat flux integrated over the path of
LI-7700 was within 2% of ambient sensible heat flux both during periods with no artificial
mirror heating and when 5 W of artificial heating was applied to the bottom mirror (resulting in equivalent of over 1000 W m-2 artificial heat flux to the mirror, heating the mirrors to 10 – 18 °C above ambient).
The LI-7700 displayed very little or no effect of instrument surface heating on the sensible
heat flux measured inside the path (Figure 8-1 c). This is different from the LI-7500,
which had 14-20% larger sensible heat flux inside the instrument path as compared to ambient air outside the path in extremely cold conditions (Grelle and Burba, 2007; Burba et
al, 2008; Clement et al, 2009).
The small-to-negligible effect of surface heating in LI-7700 is related to instrument design
of LI-7700, which is different from LI-7500. LI-7700 has much larger spacing between
mirrors, smaller mirror-to-path ratio, and the spars are positioned further away from the
cell. Virtually no warm air is moving through the spars of the LI-7700. The LI-7700 has
only three widely spaced spars and bottom mirror is separated from the underlying electronics. As a result, the LI-7700 has a more open sampling cell compared with the LI-7500
cell, which is closely surrounded by variably heated and cooled elements.
Due to small-to-negligible heating effect, methane fluxes computed with artificially heated
bottom mirror (>1000 W m-2) and those without artificial heating were not significantly
different from zero. These magnitudes were expected over the frozen fallow field with
near-zero CH4 flux as measured by chamber techniques.
8-3
Appendices
It is also important to note that, unlike CO 2 exchange, methane exchange does not usually
have a chronological sequence of emissions and uptakes of similar magnitudes. Therefore,
the %-error incurred during methane flux measurements is similar to %-error in long-term
methane budget. With CO2 flux, long-term budget is often close to zero, and %-error in
hourly fluxes may translate into a much larger error in long-term budget.
The LI-7700 will also have temperature measured inside the instrument sampling path
and three additional high-speed thermocouple channels to accommodate measurements of
the sensible heat fluxes inside the path if one wishes to use them. In normal operation they
are not needed.
8-4
Appendices
Sensible Heat Flux, W m-2
150
Ambient
Inside path of LI-7700
100
50
0
50
100
2/10
2/11
2/12
150
Inside path of LI-7700
100
2/13
With artificial 5 W heater (b)
(mirror temperature 10
to 18 °C above ambient)
Ambient
Sensible Heat Flux, W m-2
(a)
No artificial heating
50
0
50
Sensible heat flux inside the path, W m-2
100
2/29
3/1
200
3/2
3/3
(c)
y = 0.98x
R² = 0.99
150
100
50
0
50
100
100
50
0
50
100
150
200
250
Ambient Sensible heat flux, W m-2
Figure 8-1. Sensible heat fluxes inside and outside the sampling path of LI-7700: (A) Example of three
days of ambient sensible heat fluxes plotted alongside the sensible heat flux integrated over LI-7700 path;
(B) Example of three days in cold conditions with artificial heating provided to bottom mirror; (C) oneto-one comparison for the entire experiment duration in February and March 2008. Open symbols are
with no artificial heating, and closed symbols are with 5 W heater, providing an equivalent of over 1000
W m-2.
8-5
Appendices
References:
Burba, G. D. McDermitt, A. Grelle, D. Anderson, and L. Xu. 2008. Addressing the
influence of instrument surface heat exchange on the measurements of CO2 flux from
open-path gas analyzers. Global Change Biology, 14(8): 1854-1876.
Clement, R., G. Burba, A. Grelle, D. Anderson, and J. Moncrieff, 2009. Improved trace gas
flux estimation through IRGA sampling optimization. Agricultural and Forest
Meteorology, 149 (3-4): 623-638
Grelle, A., and G. Burba, 2007. Fine-wire thermometer to correct CO2 fluxes by openpath analyzers for artificial density fluctuations. Agricultural and Forest Meteorology, 147
(1-2): 48–57
8-6
Appendices
Appendix C. Troubleshooting
LI-7700 will not power up:
Power supply inadequate – be sure the power supply is 10.5 to 30 VDC, 3 Amps.
Power supply connected improperly – this will blow the fuse. Connect the power supply
correctly and replace the fuse.
Blown fuse – replace the fuse.
Lower mirror spin motor runs loudly at startup:
Power supply inadequate – be sure the power supply is 10.5 to 30 VCD, 3 Amps.
Temperature readings are unreasonable:
Thermocouple damaged – replace the optical path thermocouple.
LI-7700 not visible on the network:
If running Windows® XP, try enabling IPv6 (see page 7-10).
Enter your instrument’s IPv4 address manually. The IPv4 address is printed with documentation that accompanied your LI-7700. Contact LI-COR Biosciences if you need
more information.
Pressure measurements noisy:
The mirror washer causes perturbations in the pressure measurement due to the proximity
of the pressure sensor to the lower mirror. One way to reduce this effect is to set the
cleaner to operate less frequently.
Optics RH warning in the software or diagnostic data:
Desiccant needs to be replaced. The RH warning turns on if the relative humidity in the
head is over 30%.
Data loss during night/morning hours:
Mirrors may be covered in condensation. Check the signal strength record during those
periods. If the signal strength drops in condensing conditions, turn on the mirror heaters
or boost the power delivered to the mirror heaters during those time periods.
Washer fluid used up too quickly:
Check the washer mirror settings. Try lowering the signal strength threshold, setting the
stop time close to the start time, or reducing the duration of the cleaning cycle.
Attach an auxiliary reservoir to the washer assembly.
8-7
Appendices
No Methane data stream:
If your computer goes to “sleep”, the methane graph will not update upon “waking up”.
Click the “Clear Charts” button.
Be sure the “Pause/Resume” button has not been pressed.
Methane density data near zero, negative, or otherwise unbelievable:
Check the Diagnostics Page1 tab. If the graph does not make a nice bell curve shape, check
the “Laser control:” in the Status frame. If the indicator is red, the reference signal is “unlocked”. Click the red indicator or press Ctrl +Alt +L to open the Laser Temperature
Control window. Follow the steps described on page 7-1 to re-enable the line locking.
Check the zero and span using the procedure described on page 7-6.
If these do not work, contact LI-COR Biosciences.
Instrument does not keep time when disconnected from power supply:
The internal battery needs to be replaced. Contact LI-COR for details.
8-8
Appendices
Appendix D. Suppliers
The company names and contact information given below are the most current we have at
the time of this printing. In some cases, the information may change without notice.
Chemical Sources
Desiccant
Scrub Bottle Kit (1 pre-charged
scrub bottle)
Magnesium Perchlorate, 2 kg
LI-COR Part Number
7700-950
9960-078
Additional Suppliers:
Fisher Scientific
www.fishersci.com
800-766-7000
770-871-4500
Thomas Scientific
www.thomassci.com
800-345-2100
856-467-2000
P.W. Perkins Co., Inc.
www.pwperkins.com
856-769-3525
VWR Scientific Products
www.vwrsp.com
800-932-5000
908-757-4045
GFS Chemicals, Inc.
www.gfschemicals.com
800-394-5501
740-881-5501
LI-COR Biosciences
4421 Superior Street
Lincoln, NE 68504 USA
800-447-3576
402-467-3576
www.licor.com
8-9
Appendices
Calibration Gases
U.S. & International
Scott Specialty Gases
6141 Easton Road
Plumsteadville, PA 18949
Phone: 215-766-8860
FAX: 215-766-0320
www.scottgas.com
Check for local distributors
U.S.
Air Liquide America Specialty Gases LLC
6141 Easton Road, Box 310
Plumsteadville, PA 18949
Phone: 800-217-2688
FAX: 215-766-2476
solutions.center@airliquide.com
www.alspecialtygases.com or www.scottgas.com
Check for local distributors
Canada
Air Liquide Canada Inc.
1250 Rene-Levesque Boulevard West
Suite 1700
Montreal, PQ H38 5E6
Phone: 800-217-2688
FAX: 514-846-7700
Email: info.alc@airliquide.com
www.specialtygas.ca
8-10
Appendices
Turck® Cables
Turck, Inc.
3000 Campus Drive
Minneapolis, MN 55441
Phone: 612-553-7300
FAX: 612-553-0708
www.turck.com
Turck Cables used with the LI-7700.
LI-COR p/n
392-10108
392-10107
Cable
Ethernet
Ethernet Adapter
392-10109
392-10268
Analog In/Out
Serial
392-10093
392-10094†
392-10211
Connector
8-pin male-male
8-pin female to
RJ45
12-pin male
6-pin female to DB9 female
4-pin male
4-pin female
4-pin male-male
Turck p/n
RSS RSS841-*M
RKC RJ45 840-*M
RSS 12T-*
RKC 6T-*DB9F/CS12317
RSS 4.4T-*
RK4.41T-*/S529
PKGV-4M-*PKGV4M/S90
SDM Interface
Power
Washer Assembly
Power Cable
* refers to cable length
† when ordering a power cable from LI-COR, request p/n 9975-030. Power cables provided by Turck may have bare leads; the brown and white leads connect to the negative
terminal, and the blue and black connect to the positive terminal.
8-11
Appendices
Industrial Rated USB Flash Drives
Delkin Devices, Inc.
13350 Kirkham Way
Poway, CA 92064-7117
Phone: 800-637-8087
www.delkin.com
IronKey, Inc.
5150 El Camino Real, C31
Los Altos, CA 94022-1542 USA
Phone: 650-492-4055
Fax: 650-967-4650
www.inronkey.com
STEC Inc.
3001 Daimler Street
Santa Ana, CA 92705
Phone: 949-476-1180
www.stec-inc.com
Mounting Hardware
Nu-Rail
Metropolitan Pipe & Supply Co.
303 Binney St.
Cambridge, MA 02142 USA
Phone: 1-800-638-7473
Fax: 617-354-3869
www.nurail.com
8-12
Warranty
For the most up to date warranty information, see the Standard Terms and Conditions of Sale at
http://www.licor.com/corp/terms.jsp
Each LI-COR, Inc. instrument is warranted by LI-COR, Inc. to be free from defects in material and workmanship; however, LI-COR, Inc.'s sole obligation under this warranty shall be to repair or replace any part
of the instrument, which LI-COR, Inc.'s examination discloses to have been defective in material or workmanship without charge and only under the following conditions, which are:
1. The defects are called to the attention of LI-COR, Inc. in Lincoln, Nebraska, in writing within one year
after the shipping date of the instrument.
2. The instrument has not been maintained, repaired, or altered by anyone who was not approved by
LI-COR, Inc.
3. The instrument was used in the normal, proper, and ordinary manner and has not been abused, altered,
misused, neglected, involved in an accident or damaged by act of God or other casualty.
4. The purchaser, whether it is a DISTRIBUTOR or direct customer of LI-COR or a DISTRIBUTOR'S customer, packs and ships or delivers the instrument to LI-COR, Inc. at LI-COR Inc.'s factory in Lincoln,
Nebraska, U.S.A. within 30 days after LI-COR, Inc. has received written notice of the defect. Unless other
arrangements have been made in writing, transportation to LI-COR, Inc. (by air unless otherwise
authorized by LI-COR, Inc.) is at customer expense.
5. No-charge repair parts may be sent at LI-COR, Inc.'s sole discretion to the purchaser for installation by
purchaser.
6. LI-COR, Inc.'s liability is limited to repair or replace any part of the instrument without charge if
LI-COR, Inc.'s examination disclosed that part to have been defective in material or workmanship.
There are no warranties, express or implied, including but not limited to any implied warranty of merchantability or fitness for a particular purpose on underwater cables or on expendables such as batteries,
lamps, thermocouples and calibrations.
Other than the obligation of LI-COR, Inc. expressly set forth herein, LI-COR, Inc. disclaims all warranties
of merchantability or fitness for a particular purpose. The foregoing constitutes LI-COR, Inc.'s sole obligation and liability with respect to damages resulting from the use or performance of the instrument and
in no event shall LI-COR, Inc. or its representatives be liable for damages beyond the price paid for the
instrument, or for direct, incidental or consequential damages.
The laws of some locations may not allow the exclusion or limitation on implied warranties or on incidental or consequential damages, so the limitations herein may not apply directly. This warranty gives you
specific legal rights, and you may already have other rights, which vary from location to location. All warranties that apply, whether included by this contract or by law, are limited to the time period of this warranty which is a twelve-month period commencing from the date the instrument is shipped to a user who
is a customer or eighteen months from the date of shipment to LI-COR, Inc.'s authorized distributor,
whichever is earlier. This warranty supersedes all warranties for products purchased prior to June 1, 1984,
unless this warranty is later superseded.
DISTRIBUTOR or the DISTRIBUTOR'S customers may ship the instruments directly to LI-COR if they are
unable to repair the instrument themselves even though the DISTRIBUTOR has been approved for making
such repairs and has agreed with the customer to make such repairs as covered by this limited warranty.
Further information concerning this warranty may be obtained by writing or calling the Warranty manager
at LI-COR, Inc.
IMPORTANT: Please return the User Registration Card enclosed with your shipment so that we have an
accurate record of your address. Thank you.
Measuring Change in a Changing World ®
LI-COR, Inc. • Environmental
4647 Superior Street • P.O. Box 4425 • Lincoln, Nebraska 68504 USA
Phone: 402-467-3576 • FAX: 402-467-2819
Toll-free 1-800-447-3576 (U.S. & Canada)
envsales@licor.com
www.licor.com
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