LI-COR LI-7700 User manual

LI-7700
Open Path CH4 Analyzer
Instruction Manual

LI-7700
Open Path CH4Analyzer
Instruction Manual
LI-COR, Inc.
4647 Superior Street
P.O. Box 4425
Lincoln, NE 68504-0425
Telephone: [phone]
FAX: [phone]
Toll Free: 1-800-447-3576 (U.S. & Canada)
Email: [email protected]
[email protected]
www.licor.com
®

ii
LI-COR, inc.
Environmental
4647 Superior Street
P.O. Box 4000
Lincoln, Nebraska 68504 USA
Phone: [phone]
FAX: [phone]
Information: 1-800-447-3576 (Toll-free U.S. & Canada)
E-mail: [e-mail]
Manufacturer’s Name: LI-COR, Inc.
Manufacturer’s Address: 4647 Superior Street
Lincoln, Nebraska USA 68504
declares that the product
Product Name: Open Path CH
4
Gas Analyzer
Model Number(s): LI-7700
Product Options: None
conforms to the following Product Specifications:
Supplementary Information:
The product herewith complies with the requirements of the EMC Directive 2004/108/EC.
John Rada
Director of Engineering
Declaration of Conformity
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 61000-4-6 : 2003 Conducted RF Immunity, 3V
IEC 61000-4-5 : 2000 Surge Immunity, 1KV
Document #53-11453
February 9, 2010
®

iii
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.
The LI-7700 is covered by U.S. patents, patents pending, foreign equivalents, and Austrailian patent
AU2009292601.
LI-COR has licensed certain aspects of the LI-7700 that were developed with expertise from Southwest
Sciences, Inc. (Santa Fe, NM). This project was funded in part by the US Department of Energy through a
Small Business Innovation Research grant (DE-FG02-05ER84283).
Microsoft® and Windows® are registered trademarks of Microsoft Corporation. Eurofast® is a registered
trademark of Turck, Inc. All other trademarks are property of their respective owners.
LI-COR, Inc. ●4647 Superior Street ●P.O. Box 4425 ●Lincoln, Nebraska 68504
Phone: [phone] ●FAX: [phone]
Toll-free: 1-800-447-3576 (U.S. & Canada)
[email protected] ●www.licor.com
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).
© Copyright 2011, LI-COR, Inc.
Publication No. 984-10751
1st Printing – February 2010
2nd Printing – October 2010; Revised March, 2011

iv
Notes on Safety
This LI-COR product was designed to be safe when operated in the manner described in this manual. The
safety of the product cannot be guaranteed if the product is used in any other way than is specified in this
manual.
Equipment markings:
The LI-7550 is marked with this symbol for a chassis ground connection.
Manual markings:
Warning: Warnings are to warn about the possibility of minor injury to yourself or others.
Caution: Cautions must be observed in order to prevent damage to your equipment.
Important: Important indicates information that will help prevent procedural mistakes in the
operation of the equipment or related software. Failure to comply may result in poor
experimental outcomes but will not cause bodily injury or equipment damage.
Note: Notes contain important information and useful tips on the operation of your
equipment.

v
Table of Contents
Welcome… ................................................................................................................. x
1General Information 1-1
Overview of the LI-7700........................................................................................... 1-1
What’s What ............................................................................................................ 1-2
The LI-7700 Open Path CH4Analyzer ...................................................................... 1-2
Spares Kit and Cables ............................................................................................... 1-3
7550-101 Auxiliary Sensor Interface (optional) ......................................................... 1-5
Sonic Anemometer Interface Cables (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
Power On ................................................................................................................. 1-9
Connect the Ethernet Data Cable ............................................................................ 1-10
Launch the Software and Connect to an LI-7700..................................................... 1-11
Mirrors - Cleaning and Care ................................................................................... 1-12
2

Operation 2-1

Introduction to the LI-7700 Interface Software .......................................................... 2-1

Main View................................................................................................................ 2-1

Tool Bar .................................................................................................................... 2-2

Settings Bar ............................................................................................................... 2-3

Charting Pages .......................................................................................................... 2-3

Charting.................................................................................................................... 2-4

Configuring the LI-7700............................................................................................ 2-6


vi
PC/Network Data Logging (Ethernet Output) .............................................................2-6
Logging Status Columns ............................................................................................ 2-7
Splitting Files............................................................................................................. 2-7
Operating Temperature Range .................................................................................. 2-8
Manual Controls .......................................................................................................2-9
Configuring Mirror Heater Controls......................................................................... 2-10
Configuring the Spin Motor Control ........................................................................ 2-12
Instrument Name and Address ................................................................................ 2-15
Setting the Time ...................................................................................................... 2-16
Output Rate ............................................................................................................ 2-18
Configuration Files .................................................................................................. 2-19
Creating an Instrument Configuration File ............................................................... 2-19
Implementing a Configuration File .......................................................................... 2-19
LI-7700 Analog Inputs ............................................................................................ 2-20
Auxiliary Sensor Interface Terminals (Option 1) ......................................................2-21
Connecting Sensors to the Auxiliary Sensor Interface ..............................................2-23
Thermocouple Inputs .............................................................................................. 2-24
Configuring Auxiliary Inputs (LI-7700)..................................................................... 2-25
Deploying the LI-7700 and Accessories.................................................................. 2-27
Mounting the LI-7700 ............................................................................................. 2-27
Vibrations ............................................................................................................... 2-27
Positioning the LI-7700 ........................................................................................... 2-28
Grounding .............................................................................................................. 2-29
Mounting the 7550-101 Auxiliary Sensor Interface..................................................2-29
Attaching the Mirror Cleaner/Washer Assembly ...................................................... 2-30
Mounting the Washer Reservoir ..............................................................................2-31
3Operation with the LI-7550 Analyzer Interface Unit 3-1
Introduction to the LI-7550....................................................................................... 3-1
What’s What ............................................................................................................ 3-2

Spares Kit and Cables................................................................................................ 3-2

Cable Connections.................................................................................................... 3-4

Basic Setup............................................................................................................... 3-6

Power On .................................................................................................................3-6

Connecting to the LI-7700 and LI-7550 (Ethernet) .....................................................3-6

Getting an LI-7700 to talk to an LI-7550....................................................................3-7

Using an LI-7700 with an LI-7500A or LI-7200 CO2/H2O Analyzer...........................3-9

Connecting to the LI-7700 and LI-7550 (RS-232 Serial) ........................................... 3-11


vii
Using the LI-7550................................................................................................... 3-12
USB Data Logging .................................................................................................. 3-12
About USB Devices................................................................................................. 3-14
USB Storage Capacity ............................................................................................. 3-14
Analog Inputs (LI-7550) .......................................................................................... 3-15
Auxiliary Sensor Interface Terminals (Option 2) ...................................................... 3-16
Electrical Connections............................................................................................. 3-18
Analog Input Time Delays....................................................................................... 3-19
LI-7550 Clock......................................................................................................... 3-20
LI-7550 Outputs ..................................................................................................... 3-21
Ethernet .................................................................................................................. 3-21
SDM ....................................................................................................................... 3-21
RS-232.................................................................................................................... 3-25
Analog.................................................................................................................... 3-26
Analog Output Time Delays.................................................................................... 3-27
Analog Output Hardware Configuration (Option 3)................................................. 3-27
Mounting the LI-7550 Analyzer Interface Unit........................................................ 3-29
4Data Files 4-1
File Header............................................................................................................... 4-1
Data ......................................................................................................................... 4-2
Diagnostics Header .................................................................................................. 4-4
Status Columns......................................................................................................... 4-6
5Making Flux Measurements with the LI-7700 5-1
Computing Fluxes..................................................................................................... 5-2
Example Calculation................................................................................................. 5-5
Full Computation ...................................................................................................... 5-5

Simplified Computation ............................................................................................ 5-7

Finding Multipliers.................................................................................................... 5-8

Low Resolution Look-up Tables ................................................................................ 5-8

Parametric Equations............................................................................................... 5-11

High Resolution Digital Tables................................................................................ 5-14

Zero Flux Validation............................................................................................... 5-19

References.............................................................................................................. 5-20


viii
6Theory and Equation Summary 6-1
Absorption of Infrared Radiation by a Gas ................................................................ 6-1
Temperature Dependence of Absorption Line Strength.............................................. 6-2
Line Broadening Mechanisms ...................................................................................6-2
Wavelength Modulation Spectroscopy ..................................................................... 6-4
Compensating for Temperature and Pressure Changes .............................................. 6-5
Compensating for Water Vapor: Equivalent Pressure, Pe............................................ 6-7
Derivation of Multipliers for Flux Measurements ...................................................... 6-9
References.............................................................................................................. 6-14
7Advanced Operation 7-1
Calibration ............................................................................................................... 7-1
Diagnostics .............................................................................................................. 7-3
Laser Temperature Control ........................................................................................ 7-3
Opening the Laser Temperature Control Dialog ........................................................ 7-4
Manual Line Lock Example ....................................................................................... 7-5
Re-enabling Automatic Line Lock.............................................................................. 7-7
Networking .............................................................................................................. 7-7
Enabling IPv6 on Windows XP .................................................................................. 7-7
The LI-7700 Finder Application................................................................................ 7-8
Communications Grammar .................................................................................... 7-14
Introduction ............................................................................................................7-14
LI-7700 Communications........................................................................................ 7-14
Element Descriptions ..............................................................................................7-15
Grammar ................................................................................................................7-15
Configuration File Grammar.................................................................................... 7-21
Sending Commands ................................................................................................ 7-24
8

Appendices 8-1

Appendix A. Specifications....................................................................................... 8-1

LI-7700 Open Path CH4Analyzer ............................................................................. 8-1

7700-101 Washer Assembly .....................................................................................8-2

LI-7550 Analyzer Interface Unit (optional) ................................................................8-2

7550-101 Auxiliary Sensor Interface (optional)..........................................................8-2

Power Requirements Summary..................................................................................8-3


ix
Appendix B. Maintenance ........................................................................................ 8-4
Changing the Internal Desiccant Bottle ..................................................................... 8-4
Changing the Thermocouple..................................................................................... 8-6
Changing the LI-7700 Fuse ....................................................................................... 8-7
Changing the LI-7550 Fuse ....................................................................................... 8-7
Appendix C. Troubleshooting ................................................................................... 8-8
Appendix D. Suppliers............................................................................................ 8-11
Chemical Sources ................................................................................................... 8-11
Calibration Gases ................................................................................................... 8-12
Turck® Cables........................................................................................................ 8-13
Industrial Rated USB Flash Drives........................................................................... 8-14
Mounting Hardware ............................................................................................... 8-14
Warranty
Index

x
Welcome…
…and thank you for your purchase of the LI-7700 Open Path CH4Analyzer. 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: [phone] ●FAX: [phone]
Toll-free: 1-800-447-3576 (U.S. & Canada)
[email protected]
www.licor.com
About this Manual:
This manual should serve as a guide to understanding the proper operation of the
instrument.
Chapter 1 introduces general information, components, and basic operation.
Chapters 2 and 3 describe setup and configuration information for the instrument and
the LI-7550 Analyzer Interface Unit.
Chapter 4 describes the data files that the LI-7700 generates.
Chapter 5 provides special instructions for computing fluxes with data from the
LI-7700.
Chapter 6 describes the theory and physical operation of Wavelength Modulation
Spectroscopy and provides the complete derivation of the flux computation algorithm
used with the LI-7700.
Chapter 7 provides advanced operation instructions, calibration information, and
communications grammar.
Chapter 8 includes the appendices, including specifications, maintenance, and
troubleshooting instructions, as well as a list of suppliers of equipment that may be
useful.

xi
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 CH4Analyzer 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). Com-
pliance for products marketed in the United States is manda-
tory. 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 CH4Analyzer
(Figure 2), indicating compliance with CDRH regulations.
Although the LI-7700 is a
Class 1 device and no hazard-
ous 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.
Figure 1. CDRH
regulation compliance
label.
Figure 2. Location of the
CDRH compliance label on
the LI-7700 Open Path CH4
Analyzer.
LI-COR
®
inc
MODEL LI-7700
SR.NO. TG1-
THISDEVICE COMPLIES WITH PART15 OF
THEFCC RULES. OPERATIONIS SUBJECT
TOTHEFOLLOWING TWO CONDITIONS:
(1) THIS DEVICE MAYNOT CAUSE HARMFUL
INTERFERENCE,AND(2) THIS DEVICE MUST
ACCEPTANYINTERFERENCE RECEIVED,
INCLUDINGINTERFERENCE THATMAY
CAUSEUNDESIRED OPERATION.
CLASS1 LASER PRODUCT
THISPRODUCT COMPLIES WITH CDRH
RADIATIONPERFORMANCESTANDARD
21CFR CHAPTER 1 SUB-CHAPTER J.
4647SUPERIOR ST.
LINCOLN,NE 68504 U.S.A.
Madein U.S.A.
PATENTSPENDING
Laser
Safety
Label
WARNING: Use of controls
or adjustments or
performance of procedures
other than those specified
herein may result in
hazardous
radiation ex
p
osure.
LI-COR
®
inc
MODEL LI-7700
SR. NO. TG1-
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.
4647 SUPERIOR ST.
LINCOLN, NE 68504 U.S.A.
Made in U.S.A.
PATENTS PENDING
!

Instruction Manual Version 2 1-1
1General 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 (WMS) to make high-speed, precise
measurements of methane concentrations at ambient pressure and temperature. It is
designed to withstand environmental extremes expected during outdoor deployments.
Some features of the LI-7700 include:
•Fast response: data are output at up to 20 Hz bandwidth.
•Low power requirements: 8 W during normal operation.
•Withstands outdoor environmental extremes, including freezing weather and high
temperatures (-25 to 50 °C) and rain without damage or calibration shifts.
•Analog input channels to integrate sonic anemometer wind speed (U, V, W) and
sonic temperature (Ts) data with CH4data.
•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 of the LI-7700 sensor and the Herriott cell. Except for
the desiccant bottle, thermocouple, and fuse, which are accessible externally, there are
no user-serviceable parts in the sensor. To ensure that components are not damaged,
never attempt to dismantle the sensor.
Suggested Reference: When referring to this instruction manual in scientific literature or other
publications, we recommend the following citation:
LI-COR, Inc. 2010. LI-7700 Open Path CH4Analyzer Instruction Manual. LI-COR,
Inc. Lincoln, NE.

1General Information
1-2 LI-7700 Open Path CH4Analyzer
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 CH4Analyzer
•
LI-7700 Open Path CH4Analyzer – 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.
Figure 1-1. Representations of the LI-7700 upper housing (top left), Herriott cell (center), and lower
housing (lower right).
Mirror
Spin
Motor
Digital Signal
Processing
Electronics
Herriott Cell Sample Path
Lower
Mirror
Pressure
Transducer
Lower Housing
Sample
Sensor Folding Mirror
Herriot Cell Sample Path
Upper
Mirror
Entrance/Exit
Aperature
Upper Housing
Reference
Sensor
Laser
CH
4
Reference
Cell
Beam Splitter
Prism

What’s What 1
Instruction Manual Version 2 1-3
Spares Kit and Cables
•
Standard Spares Kit – This (p/n 9977-019) includes the cables, mounting hard-
ware, and other essential components. Several components listed below are
attached to the instrument prior to shipping.
•
Ethernet Data Cables – There are two Ethernet cables provided: p/n 392-10108
is a 5 m cable terminated on both ends with male Turck connectors; one end
attaches to the LI-7700 Ethernet output, while the end attaches to either the 0.3 m
Ethernet adapter cable (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 (p/n 9975-030) – Used to connect the LI-7700 to a 10.5 to 30 VDC
power supply. The power cable has 4 wires: brown and white are tied to a black
lead, which connects to the negative (-) power supply terminal; blue and black are
tied to a red lead, which connects to the positive power supply terminal (+).
Blue
Black
Brown
White
Red (+)
Black (-)
(Insulation removed
to show wires)
(I
(I
n
l
su
l
ti
a
ti
on rem
ove
d
d
to show wires
)
Description Qty. LI-COR Part No.
Ethernet Cable, Eurofast (0.3 M) 8-pin female to RJ45 1 392-10107
Ethernet Cable, Eurofast (5 M) 8-pin male to 8-pin male 1 392-10108
Power Cable, Eurofast (5 M), 4-pin female 1 9975-030
5 Amp Fuse 1 438-09800
Desiccant Cap Removal Screw (attached to analyzer) 1 125-09760
Calibration Shroud 1 9977-033
Solar Shield Assembly (attached to analyzer) 1 9977-029
Thermocouple Assembly (attached to analyzer) 1 9977-038
Mounting Post (attached to analyer) 1 9977-018
Mounting Post Screws (1/4”-20, 5/8” long, attached) 2 140-04320
Washer Reservoir Assembly 1 7700-101
Washer Power Cable 1 392-10211
Spray Nozzle Assembly 1 9977-032
LI-7700 Spares Kit and Cables

1General Information
1-4 LI-7700 Open Path CH4Analyzer
•
Washer Assembly – The washer assembly includes a reservoir/pump unit, hose,
washer nozzle, and mounting hardware.
Figure 1-2. Washer reservoir for the LI-7700 washer assembly.
•
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 secure the
post to the base of the LI-7700 analyzer. The post and screws are affixed to the
analyzer prior to shipping.
•
Calibration Shroud – The calibration shroud is used to isolate the LI-7700 optical
path during calibration verification.
Figure 1-3. LI-7700 calibration shroud.
•
Computer Software – The CD includes the LI-7700 configuration/data logging
software. The software is compatible with Windows® XP/Vista/7 operating
systems.
•
Calibration Certificate – This documents the performance of your particular
instrument when it left the factory. Keep this sheet for future reference.

What’s What 1
Instruction Manual Version 2 1-5
7550-101 Auxiliary Sensor Interface (optional)
The 7550-101 is a weatherproof junction for analog inputs on the LI-7700, LI-7550,
and for the analog outputs from the LI-7550. Detailed instructions for using the 7550-
101 are provided beginning on page 2-20.
Figure 1-4. 7550-101 Auxiliary Sensor Interface.
Sonic Anemometer Interface Cables (optional)
As an alternative to the 7550-101, LI-COR can provide cables to carry the analog
output from a Gill WindMasterTM/Pro or a Campbell® Scientific, Inc. CSAT3 directly
to the analog input on the LI-7700 and/or LI-7550. These cables terminate with a Gill
or Campbell® bulkhead connector on one end and Turck bulkhead connector(s) on the
other (for connecting to the LI-7700 and/or LI-7550).
Description LI-COR
Part No.
Gill WindMaster/Pro to LI-7700 9977-062
Campbell Scientific CSAT3 to LI-7700 9977-063
Gill WindMaster/Pro to LI-7700 and LI-7550 (GHG systems) 9975-034
Campbell Scientific CSAT3 to LI-7700 and LI-7550 (GHG systems) 9975-036
Description Qty. LI-COR Part No.
U-Bolt, 1/4 by 20 2 184-09842
Hex Nuts 4 163-00138
Quick Connect Plug 10 300-07393
Strain Relief 1 198-01788
Santoprene Tubing 2 ft. (60 cm) 222-08325
7550-101 Auxiliary Sensor Interface Spares Kit (optional) p/n 9977-019

1General Information
1-6 LI-7700 Open Path CH4Analyzer
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) to a
removable USB data storage device and enabling versatile data output options. Detailed
instructions for the LI-7550 are provided in Chapter 3.
Figure 1-5. LI-7550 Analyzer Interface Unit.
See page 3-2 for a list of components included in the LI-7550 Spares Kit.

LI-7700 Components and Connections 1
Instruction Manual Version 2 1-7
LI-7700 Components and Connections
1. Radiation Shield – reduces condensation on the upper mirror. It is
in place when the instrument is shipped and it should be kept in
place during normal operation, especially in high-humidity
environments.
2. Upper Housing – encloses the laser source, sensor, and laser
control electronics (see Figure 1-1).
3. Fine-wire Thermocouple – measures the ambient temperature near
the optical path. There is 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 remain slightly above ambient temperatures in
condensing conditions.
5. Desiccant Cap – this seals the desiccant bottle. Only remove the
desiccant cap to replace the internal chemical bottle. The desiccant
cap removal screw is in place and can be left in place during normal
operation.
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 and
temperature controls to prevent 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 (see Figure 1-1).
10. Connection Panel – has indicator LEDs, weather-proof cable
connections, and an external network reset button (see Figure 1-7).
Figure 1-6. The LI-7700 Open
Path CH4Analyzer.
1.
2.
3.
4.
5.
6.
8.
7.
10.
9.