Campbell Scientific EC150 User Manual

INSTRUCTION MANUAL

EC150 CO2/H2O Open-Path

Copyright © 2010- 2014

Campbell Scientific, Inc.

Gas Analyzer

Revision: 6/14

Limited Warranty

“Products manufactured by CSI are warranted by CSI to be free from defects in
materials and workmanship under normal use and service for twelve months
from the date of shipment unless otherwise specified in the corresponding
product manual. (Product manuals are available for review online at

www.campbellsci.com.) Products not manufactured by CSI, but that are resold

by CSI, are warranted only to the limits extended by the original manufacturer.
Batteries, fine-wire thermocouples, desiccant, and other consumables have no
warranty. CSI’s obligation under this warranty is limited to repairing or
replacing (at CSI’s option) defective Products, which shall be the sole and
exclusive remedy under this warranty. The Customer assumes all costs of
removing, reinstalling, and shipping defective Products to CSI. CSI will return
such Products by surface carrier prepaid within the continental United States of
America. To all other locations, CSI will return such Products best way CIP
(port of entry) per Incoterms ® 2010. This warranty shall not apply to any
Products which have been subjected to modification, misuse, neglect, improper
service, accidents of nature, or shipping damage. This warranty is in lieu of all
other warranties, expressed or implied. The warranty for installation services
performed by CSI such as programming to customer specifications, electrical
connections to Products manufactured by CSI, and Product specific training, is
part of CSI's product warranty. CSI EXPRESSLY DISCLAIMS AND

EXCLUDES ANY IMPLIED WARRANTIES OF MERCHANTABILITY
OR FITNESS FOR A PARTICULAR PURPOSE. CSI hereby disclaims,
to the fullest extent allowed by applicable law, any and all warranties and
conditions with respect to the Products, whether express, implied or
statutory, other than those expressly provided herein.”

Assistance

Products may not be returned without prior authorization. The following
contact information is for US and international customers residing in countries
served by Campbell Scientific, Inc. directly. Affiliate companies handle
repairs for customers within their territories. Please visit

www.campbellsci.com to determine which Campbell Scientific company serves

your country.

To obtain a Returned Materials Authorization (RMA), contact CAMPBELL
SCIENTIFIC, INC., phone [phone]. After an application engineer
determines the nature of the problem, an RMA number will be issued. Please
write this number clearly on the outside of the shipping container. Campbell
Scientific’s shipping address is:

CAMPBELL SCIENTIFIC, INC.
RMA#_____
815 West 1800 North
Logan, Utah 84321-1784

For all returns, the customer must fill out a “Statement of Product Cleanliness
and Decontamination” form and comply with the requirements specified in it.
The form is available from our web site at www.campbellsci.com/repair. A
completed form must be either emailed to [e-mail] or faxed to
[phone]. Campbell Scientific is unable to process any returns until we
receive this form. If the form is not received within three days of product
receipt or is incomplete, the product will be returned to the customer at the
customer’s expense. Campbell Scientific reserves the right to refuse service on
products that were exposed to contaminants that may cause health or safety
concerns for our employees.

Precautions

DANGER — MANY HAZARDS ARE ASSOCIATED WITH INSTALLING, USING, MAINTAINING, AND WORKING ON OR AROUND

TRIPODS, TOWERS, AND ANY ATTACHMENTS TO TRIPODS AND TOWERS SUCH AS SENSORS, CROSSARMS, ENCLOSURES,
ANTENNAS, ETC. FAILURE TO PROPERLY AND COMPLETELY ASSEMBLE, INSTALL, OPERATE, USE, AND MAINTAIN TRIPODS,

TOWERS, AND ATTACHMENTS, AND FAILURE TO HEED WARNINGS, INCREASES THE RISK OF DEATH, ACCIDENT, SERIOUS
INJURY, PROPERTY DAMAGE, AND PRODUCT FAILURE. TAKE ALL REASONABLE PRECAUTIONS TO AVOID THESE HAZARDS.
CHECK WITH YOUR ORGANIZATION'S SAFETY COORDINATOR (OR POLICY) FOR PROCEDURES AND REQUIRED PROTECTIVE
EQUIPMENT PRIOR TO PERFORMING ANY WORK.

Use tripods, towers, and attachments to tripods and towers only for purposes for which they are designed. Do not exceed design
limits. Be familiar and comply with all instructions provided in product manuals. Manuals are available at www.campbellsci.com or
by telephoning 435-227-9000 (USA). You are responsible for conformance with governing codes and regulations, including safety
regulations, and the integrity and location of structures or land to which towers, tripods, and any attachments are attached. Installation
sites should be evaluated and approved by a qualified engineer. If questions or concerns arise regarding installation, use, or
maintenance of tripods, towers, attachments, or electrical connections, consult with a licensed and qualified engineer or electrician.

General

• Prior to performing site or installation work, obtain required approvals and permits. Comply

with all governing structure-height regulations, such as those of the FAA in the USA.

• Use only qualified personnel for installation, use, and maintenance of tripods and towers, and

any attachments to tripods and towers. The use of licensed and qualified contractors is highly
recommended.

• Read all applicable instructions carefully and understand procedures thoroughly before

beginning work.

• Wear a hardhat and eye protection, and take other appropriate safety precautions while

working on or around tripods and towers.

• Do not climb tripods or towers at any time, and prohibit climbing by other persons. Take

reasonable precautions to secure tripod and tower sites from trespassers.

• Use only manufacturer recommended parts, materials, and tools.

Utility and Electrical

• You can be killed or sustain serious bodily injury if the tripod, tower, or attachments you are

installing, constructing, using, or maintaining, or a tool, stake, or anchor, come in contact with
overhead or underground utility lines.

• Maintain a distance of at least one-and-one-half times structure height, or 20 feet, or the

distance required by applicable law, whichever is greater, between overhead utility lines and
the structure (tripod, tower, attachments, or tools).

• Prior to performing site or installation work, inform all utility companies and have all

underground utilities marked.

• Comply with all electrical codes. Electrical equipment and related grounding devices should

be installed by a licensed and qualified electrician.

Elevated Work and Weather

• Exercise extreme caution when performing elevated work.

• Use appropriate equipment and safety practices.

• During installation and maintenance, keep tower and tripod sites clear of un-trained or non-

essential personnel. Take precautions to prevent elevated tools and objects from dropping.

• Do not perform any work in inclement weather, including wind, rain, snow, lightning, etc.

Maintenance

• Periodically (at least yearly) check for wear and damage, including corrosion, stress cracks,

frayed cables, loose cable clamps, cable tightness, etc. and take necessary corrective actions.

• Periodically (at least yearly) check electrical ground connections.

WHILE EVERY ATTEMPT IS MADE TO EMBODY THE HIGHEST DEGREE OF SAFETY IN ALL CAMPBELL SCIENTIFIC PRODUCTS,
THE CUSTOMER ASSUMES ALL RISK FROM ANY INJURY RESULTING FROM IMPROPER INSTALLATION, USE, OR
MAINTENANCE OF TRIPODS, TOWERS, OR ATTACHMENTS TO TRIPODS AND TOWERS SUCH AS SENSORS, CROSSARMS,
ENCLOSURES, ANTENNAS, ETC.

Table of Contents

PDF viewers: These page numbers refer to the printed version of this document. Use the
PDF reader bookmarks tab for links to specific sections.

1. Introduction ................................................................. 1

2. Cautionary Statements ............................................... 1

3. Initial Inspection ......................................................... 2

4. Overview ...................................................................... 2

4.1 General ................................................................................................. 2

4.2 Features ................................................................................................ 2

4.3 Gas Head Memory ............................................................................... 3

4.4 Self-diagnostics and Data Integrity ...................................................... 3

4.5 Field Zero/Span Capabilities ................................................................ 3

4.6 EC100 Electronics Module .................................................................. 4

4.6.1 EC100 Communications and Control ........................................... 4

4.6.2 EC100 Outputs .............................................................................. 4

4.6.2.1 SDM Output ....................................................................... 5

4.7 Automatic Heater Control .................................................................... 5

4.8 Theory of Operation ............................................................................. 6

5. Specifications ............................................................. 7

5.1 Measurements ...................................................................................... 7

5.2 Output Signals ...................................................................................... 9

5.3 Physical Description ............................................................................ 9

5.4 Power Requirements .......................................................................... 10

6. Installation ................................................................. 11

6.1 Orientation ......................................................................................... 11

6.2 Mounting Analyzer to Support Hardware .......................................... 11

6.2.1 Preparing the mounting structure ................................................ 14

6.2.2 Mounting EC150 with optional CSAT3A ................................... 14

6.2.3 Mounting EC150 without CSAT3A ........................................... 16

6.2.4 Attaching EC100 Electronics Enclosure to Mounting

Structure .................................................................................. 17

6.2.5 Install the EC150 Temperature Probe ......................................... 18

6.3 Wiring and Connections ..................................................................... 19

6.3.1 Connecting the EC150 Gas Analyzer Head ................................ 20

6.3.2 Connect the CSAT3A Sonic Head .............................................. 20

6.3.3 Connect the EC150 Temperature Probe ...................................... 21

6.3.4 Ground the EC100 Electronics ................................................... 21

6.3.5 Connect SDM Communications to the EC100 ........................... 21

6.3.6 Wire Power and Ground the EC100 ........................................... 22

7. Zero and Span ........................................................... 22

7.1 Introduction ........................................................................................ 22

i

Table of Contents

7.2 Zero and Span Procedure .................................................................. 23

8. Maintenance and Troubleshooting .......................... 28

8.1 Routine Site Maintenance ................................................................. 28

8.2 Gas Analyzer Wicks .......................................................................... 28

8.3 Cleaning Analyzer Windows ............................................................. 29

8.4 Zero and Span.................................................................................... 29

8.5 Replacing CO2 Scrubber Bottles ....................................................... 30

8.6 Factory Recalibration ........................................................................ 31

8.7 Troubleshooting ................................................................................ 32

8.7.1 Data Loss During Precipitation Events ...................................... 32

8.7.2 EC100 Diagnostics for Gas Analyzer Troubleshooting ............. 32

8.7.3 LED Status Lights ...................................................................... 32

8.7.4 Diagnostic Flags ......................................................................... 33

Appendices

EC150 Settings ........................................................ A-1

A.

A.1 Factory Defaults .............................................................................. A-1

A.2 Details ............................................................................................. A-1

A.2.1 SDM Address ........................................................................... A-2

A.2.2 Bandwidth ................................................................................ A-2

A.2.3 Unprompted Output ................................................................. A-2

A.2.4 Unprompted Output Rate ......................................................... A-2

A.2.5 RS-485 Baud Rate .................................................................... A-3

A.2.6 Analog Output .......................................................................... A-3

A.2.7 ECMon Update Rate ................................................................ A-3

A.2.8 Temperature Sensor ................................................................. A-3

A.2.9 Fixed Temperature Value ......................................................... A-3

A.2.10 Pressure Sensor ........................................................................ A-4

A.2.10.1 Pressure Gain ................................................................. A-6

A.2.10.2 Pressure Offset ............................................................... A-6

A.2.10.3 Fixed Pressure Value ..................................................... A-6

A.2.11 Pressure Differential Enable ..................................................... A-6

A.2.12 Heater Control .......................................................................... A-7

A.2.13 Head Power Off........................................................................ A-7

A.3 ECMon ............................................................................................ A-7

A.4 Device Configuration Utility ........................................................... A-9

A.5 EC100Configure() Instruction ......................................................... A-9

A.5.1 ConfigCmd 11 Zero-and-Span Control .................................. A-11

A.6 Example CRBasic Program ........................................................... A-12

B. Filter Bandwidth and Time Delay ........................... B-1

C. Alternate EC100 Outputs ........................................ C-1

C.1 USB or RS-485 Output.................................................................... C-1

C.1.1 Specifications ........................................................................... C-1

C.1.2 Detailed Information ................................................................ C-1

C.2 Analog Output ................................................................................. C-3

C.2.1 Specifications ........................................................................... C-3

C.2.2 Detailed Information ................................................................ C-3

ii

Table of Contents

D. Useful Equations .................................................... D-1

E. Material Safety Data Sheets (MSDS) ..................... E-1

E.1 Magnesium Perchlorate MSDS ........................................................ E-1

E.2 Decarbite MSDS .............................................................................. E-8

F. Packing Information ............................................... F-1

F.1 EC150-GH Packing Information ...................................................... F-1

F.2 EC150-SH Packing Information ...................................................... F-2

Figures

4-1. EC100 electronics module ................................................................... 4

5-1. Optical path and envelope dimensions of EC150 analyzer head........ 10

6-1. Mounting bracket options for EC150 head only (pn 26785) or

EC150 head with CSAT3A (pn 26786) .......................................... 11

6-2. Changes in flux attenuation ratio relative to sensor height at the

most fore and aft positions .............................................................. 12

6-3. Mounting position of CSAT3A and EC155 with a 4.9 cm sensor

separation. ....................................................................................... 13

6-4. Mounting position of CSAT3A and EC155 with a 9.7 cm sensor

separation. ....................................................................................... 13

6-5. Exploded view of mounting CSAT3A and EC150 ............................ 15

6-6. Exploded view of mounting the EC150 without the CSAT3A .......... 16

6-7. EC100 enclosure mounting bracket mounted on a vertical mast

(left) and a tripod leg (right) ........................................................... 17

6-8. Exploded view of mounting the EC100 enclosure ............................. 18

6-9. EC150 temperature probe .................................................................. 19

6-10. Solar radiation shield with EC150 temperature probe ....................... 19

6-11. EC100 electronics front panel showing EC100 as shipped (left)

and after completed wiring and connections (right) ....................... 19

6-12. Bottom of EC100 enclosure ............................................................... 20

7-1. Zero-and-span shroud mounted on the zero-and-span stand .............. 24

7-2. ECMon zero-and-span window .......................................................... 26

8-1. Proper location of the gas analyzer top wick (left) and bottom

wick (right) ..................................................................................... 29

8-2. Replacing the desiccant/CO2 scrubber bottles .................................... 31

8-3. LED status during normal operation .................................................. 32

A-1. Location of EC100 basic barometer ................................................ A-4

A-2. Location of EC100 enhanced barometer ......................................... A-5

A-3. Comparison of error in basic versus enhanced barometer over

operational temperatures .............................................................. A-5

A-4. Main screen of ECMon ................................................................... A-8

A-5. Setup screen in ECMon ................................................................... A-8

B-1. Amplitude response of EC100 filter at various bandwidths ............. B-1

B-2. Frequency response comparison of EC100 10-Hz bandwidth

and a 50-msec moving average ..................................................... B-2

C-1. USB data output in terminal mode ................................................... C-2

Tables

6-1. EC100 SDM output to a Campbell Scientific CR1000, CR3000,

or CR5000 Datalogger .................................................................... 22

8-1. Rain Wick Replacement Parts ............................................................ 28

iii

Table of Contents

8-2. Diagnostic Flags of Sonic Status LED .............................................. 33

8-3. Diagnostic Flags and Suggested Actions........................................... 34

A-1. Factory Default Settings .................................................................. A-1

A-2. ConfigCmd Values for Setting and Retrieving Settings ................ A-10

B-1. Filter Time Delays for Various Bandwidths .................................... B-3

C-1. USB and RS-485 Output Elements ................................................. C-1

C-2. Multipliers and Offsets for Analog Outputs .................................... C-4

D-1. Variables and Constants .................................................................. D-1

iv

EC150 CO2/H2O Open-Path Gas
Analyzer

1. Introduction

The EC150 is an in situ, open-path, mid-infrared absorption gas analyzer that
measures the absolute densities of carbon dioxide and water vapor. The EC150
was designed for open-path eddy covariance flux measurements as part of an
open-path eddy covariance measurement system. It is most often used in
conjunction with the CSAT3A sonic anemometer and thermometer, which
measures orthogonal wind components along with sonically determined air
temperature.

Before attempting to assemble, install or use the EC150, please study:

• Section 2, Cautionary Statements

• Section 3, Initial Inspection

• Section 6, Installation

Greater detail is available in the remaining sections.

Other manuals that may be helpful include:

• CR3000 Micrologger Operator’s Manual

• CFM100 CompactFlash Module Instruction Manual

• NL115 Ethernet and CompactFlash Module Instruction Manual

• Application Note 3SM-F, PC/CF Card Information

• LoggerNet Instruction Manual, Version 4.1

• CSAT3 Three Dimensional Sonic Anemometer Manual

• ENC10/12, ENC12/14, ENC14/16, ENC16/18 Instruction Manual

• CM106 Tripod Instruction Manual

• Tripod Installation Manual Models CM110, CM115, CM120

2. Cautionary Statements

• DANGER:

o The scrubber bottles in the EC150 contain sodium hydroxide

(NaOH) and anhydrous magnesium perchlorate (Mg(ClO
not attempt to access or remove these chemical bottles before
reviewing Section 8.5, Replacing CO

 Avoid direct contact with the chemicals.
 Ensure your work area is well ventilated and free of

 Store used chemical bottles in a sealed container until

 Dispose of chemicals and bottles properly.

• WARNING:

o Do not carry the EC150 by the arms or the strut between the

arms. Always hold it by the mounting base where the upper and
lower arms connect.

Scrubber Bottles.

2

reactive compounds and combustible materials.

disposal.

4)2

). Do

1

EC150 CO2/H2O Open-Path Gas Analyzer

o Handle the EC150 carefully. The optical source may be damaged

o Overtightening bolts will damage or deform the mounting

• CAUTION:

o Grounding the EC100 measurement electronics is critical. Proper

o Do not connect or disconnect the gas analyzer or sonic

o Resting the analyzer on its side during the zero-and-span

3. Initial Inspection

Upon receipt of your equipment, inspect the packaging and contents for
damage. File damage claims with the shipping company.

Model numbers are found on each component. On cables, the model number is
located both on the sensor head and on the connection end of the cable. Check
this information against the enclosed shipping document to verify the expected
products and that the correct accessories are included.

by rough handling, especially while the analyzer is powered.

hardware.

grounding to Earth will ensure maximum electrostatic discharge
(ESD) and lightning protection and improve measurement
accuracy.

anemometer connectors while the EC100 is powered.

procedure may result in measurement inaccuracy.

4. Overview

4.1 General

4.2 Features

The EC150 measures absolute densities of carbon dioxide and water vapor.
The EC150 analyzer was designed specifically for open-path, eddy covariance
flux measurement systems. The EC150 gas analyzer head connects directly to
Campbell Scientific’s EC100 electronics. The EC150 is commonly used with a
CSAT3A sonic anemometer head. When the CSAT3A is used in conjunction
with the EC150, the EC100 can make gas and wind measurements
simultaneously. Similarly, the EC100 can simultaneously record
measurements from temperature sensors and a pressure transducer.

The EC150 analyzer has a rugged, aerodynamic design with low power
requirements, making it suitable for field applications including those with
remote access.

The EC150 has been designed specifically to address issues of aerodynamics,
power consumption, spatial displacement, temporal synchronicity, and to
minimize sensitivity to environmental factors.

The analyzer windows are scratch resistant and treated with a durable
hydrophobic coating that facilitates shedding of raindrops from critical
surfaces. The coating also impedes the accumulation of dust and deposits, and
keeps the surfaces cleaner over longer periods of time. To minimize data loss
due to humid environments, the EC150 is provided with window wicks that
draw moisture away from the measurement path and are easily replaceable
during routine maintenance.

2

EC150 CO2/H2O Open-Path Gas Analyzer

• Unique design contains little obstruction surrounding the sample

volume

• 5W total power consumption

• Synchronously samples data from the EC150 and CSAT3A

• Automatically configured via a Campbell Scientific datalogger

• Minimal spatial displacement between sample volume and CSAT3A

• Slim housings located away from the measurement volume to

minimize body heating effects due to solar radiation

• Symmetrical design for improved flux measurements without a bias

for updrafts and downdrafts

• Slanted windows to prevent water from pooling and blocking the

optical path

• Scratch-resistant windows for easy cleaning

• Hydrophobic coating on windows to repel water, dust and pollen and

to prolong time between window cleaning

• Equipped with internal window heaters to keep the windows surfaces

free from condensation and frost – especially beneficial in humid
environments or conditions with frequent frost formation

• Optical layout that is not affected by solar interference

• Mercury cadmium telluride (MCT) detector for low-noise

measurements and long-term stability of factory calibration

• Chopper housing without thermal control results in significantly

reduced power consumption

4.3 Gas Head Memory

The EC100 electronics (see Section 4.6, EC100 Electronics Module) are
universal for the entire Campbell Scientific family of gas analyzer heads. In
addition to the EC150 gas analyzer head, the IRGASON or EC155 gas
analyzer head can be connected to the EC100 electronics (one gas analyzer
head per EC100). All sensor heads have dedicated, non-volatile memory,
which stores all calibration, configuration, and setting information. The EC100
electronics can be mated with any of these gas analyzers or an optional
CSAT3A sonic anemometer head.

4.4 Self-diagnostics and Data Integrity

EC100 electronics provide an extensive set of diagnostic tools which include
warning flags, status LEDs, and signal strength outputs to identify instrument
malfunctions and warn the user of compromised data. These flags are further
described in Section 8.7.4, Diagnostic Flags. The flags also prompt the user
when the instrument needs servicing and can facilitate troubleshooting in the
field. The EC150 outputs the optical strength of signals, which can be used to
filter data when the path of the instrument is obstructed due to precipitation or
dirty windows.

4.5 Field Zero/Span Capabilities

A zero/span for CO2 and H2O can be accomplished in the field with an
optional shroud. The shroud allows the flow of a gas with known composition
in the measurement path of the analyzer to account for instrument drift and
changing environmental conditions.

3

EC150 CO2/H2O Open-Path Gas Analyzer

4.6 EC100 Electronics Module

The EC100 electronics module (shown in FIGURE 4-1) controls the EC150
and optional CSAT3A sonic anemometer head. The EC100 synchronizes
measurements and processes data from the EC150 and the CSAT3A.

FIGURE 4-1. EC100 electronics module

4.6.1 EC100 Communications and Control

The EC100 supports several serial communication interfaces, including USB,
RS-485, and Synchronous Device for Measurement (SDM). SDM is a
Campbell Scientific communication protocol that allows synchronized
measurement and rapid communication between a Campbell Scientific
datalogger and multiple devices including the EC150. Although nearly all
Campbell Scientific dataloggers support SDM, only the CR1000, CR3000, and
CR5000 dataloggers support communications with the EC100 electronics with
the EC100() instruction.

The SDM protocol allows the user to configure and control the analyzer
through CRBasic instructions in the datalogger. For example, in solar-powered
applications with limited daylight, battery power can be conserved by
programming the datalogger to turn off the EC150 at night or when conditions
are not suitable for eddy-covariance measurements. The datalogger can also be
used to change settings such as bandwidth, and perform the zero/span
procedure in the field.

4.6.2 EC100 Outputs

The EC100 outputs data in one of four types: SDM, USB, RS-485, or analog.
In general, Campbell Scientific recommends that SDM be used if a Campbell
Scientific datalogger is collecting data. However, RS-485 output is
recommended over SDM if cable lengths exceed 100 meters. If a PC is being
used as the data collection platform, USB and RS-485 are suitable outputs.

4

Information for SDM, the preferred output, is detailed below. See Appendix C,
Alternate EC100 Outputs, for USB, RS-485, and analog outputs.

4.6.2.1 SDM Output

EC150 CO2/H2O Open-Path Gas Analyzer

To use SDM data output, connect an SDM communications cable from the
EC100 (see Section 6.3, Wiring and Connections) to a CR1000, CR3000, or
CR5000 datalogger. On CR1000 dataloggers, the SDM protocol uses ports C1,
C2, and C3. These are multipurpose control ports that are SDM-activated
when an SDM instruction is used in the datalogger’s program. On CR3000 and
CR5000 dataloggers, the SDM protocol uses SDM-dedicated ports SDM-C1,
SDM-C2, and SDM-C3.

Each SDM device on the SDM bus must have a unique address. The EC150
has a factory default SDM address of 1, but may be changed to any integer
value between 0 and 14 (see Appendix A.2.1, SDM Address).

The sample rate for SDM output is determined by the datalogger program.
Data are output from the EC100 when a request is received from the datalogger
(for example, a prompted output mode). The number of data values sent from
the EC100 to the datalogger is also set by the user in the datalogger program.
CRBasic, the programming language used by Campbell Scientific dataloggers,
uses the EC100() instruction to get data from an EC150. This instruction is
explained in greater detail under Appendix A, EC150 Settings, and in
Appendix A.5, EC100 Configure() Instruction.

4.7 Automatic Heater Control

An advantage of the EC150’s low power consumption (5W) is that the
instrument remains at a temperature very close to ambient air temperature,
which is an important feature for eddy-covariance measurements. Under some
environmental conditions, however, the analyzer can become colder than
ambient air temperature which may increase the likelihood of frost or
condensation building on the optical windows. This will affect signal strength.
The EC150 design includes internal heaters located at the optical windows,
which aid in minimizing data loss during these specific environmental
conditions.

An automatic heater control algorithm can be activated from either Device
Configuration or ECMon by putting in a value of −2, or deactivated by putting
in a value of −1.
temperature that is a couple of degrees above the ambient dewpoint (or frost
point) to prevent condensation and icing from forming on the surface of the
optical windows.

The heater control will be disabled under any of the following conditions:

• Temperature of the detector housing is outside the −35°C to +55°C

• Temperature of the source housing exceeds 40°C

• Ambient temperature is outside the −35°C to +55°C range

• The supply voltage is below 10 V

range

i

The algorithm uses the internal heaters to maintain a

i

Automatic heater control is available in EC100 OS version 4.07 or greater and is turned on by

default starting with the OPEC program version 3.2.

5

EC150 CO2/H2O Open-Path Gas Analyzer

cl

o

ePP

ε

−

=

The algorithm uses the following environmental parameters to control the
heater:

• Analyzer body temperature, measured inside the source housing

(heater control does not allow the body temperature to drop below
ambient air temperature)

• Ambient relative humidity (in humidity greater than 80% heaters will

try to maintain internal temperature 2 degrees warmer than ambient)

• CO

cause the heater to turn on maximum power until the signals recover)

• Average slope of the CO

• Standard deviation of the CO

4.8 Theory of Operation

The EC150 is a non-dispersive mid-infrared absorption analyzer. Infrared
radiation is generated in the upper arm of the analyzer head before propagating
along a 15.0 cm (5.9 in) optical path as shown in FIGURE 5-1. Chemical
species located within the optical beam will absorb radiation at characteristic
frequencies. A mercury cadmium telluride (MCT) detector in the lower arm of
the gas analyzer measures the decrease in radiation intensity due to absorption,
which can then be related to analyte concentration using the Beer-Lambert
Law:

signal level (1 min average CO2 signal level; below 0.7 will

2

signal level over 1 min

2

signal over 1 min

2

where:

P is irradiance after passing through the optical path

is initial irradiance, ε is molar absorptivity, c is analyte

P

o

concentration, and

l is path length.

In the EC150, radiation is generated by applying constant power to a tungsten
lamp which acts as a 2200 K broadband radiation source. Specific
wavelengths are then selected using interference filters located on a spinning
chopper wheel. For CO

measurements, light with a wavelength of 4.3 µm is

2

selected as that corresponds to the asymmetric stretching vibrational band of
the CO

molecule. For H2O, the symmetric stretching vibration band is 2.7

2

µm.

The EC150 is a dual wavelength, single-beam analyzer. This design eliminates
the need for a separate reference cell and detector. Instead, the initial intensity
of the radiation is calculated by measuring the intensity of nearby, non­absorbing wavelengths (4.0 µm for CO

and 2.3 µm for H2O). These

2

measurements mitigate measurement inaccuracy that may arise from source or
detector aging, as well as for low-level window contamination. For window
contamination that reduces the signal strength below 0.8, windows should be
cleaned as described in Section 8.3, Cleaning Analyzer Windows.

The chopper wheel spins at a rate of 50 revolutions per second and the detector
is measured 1024 times per revolution, resulting in a detector sampling rate of

51.2 kHz. The detector is maintained at −40°C using a three-stage
thermoelectric cooler and is coupled to a low noise pre-amp module.

6

The EC100 electronics module digitizes and process the detector data (along
with ancillary data such as ambient air temperature and barometric pressure) to
give the CO
high measurement rate is beneficial when there is a need to synchronize the gas
measurements with additional sensors measured by the datalogger. To prevent
aliasing, measurements are filtered to a bandwidth that is specified by the user.

5. Specifications

5.1 Measurements

To compute carbon dioxide and water vapor fluxes using the eddy-covariance
method, the EC150 and a sonic anemometer measure:

These measurements are required to compute carbon dioxide and water vapor
fluxes using the:

EC150 CO2/H2O Open-Path Gas Analyzer

and H2O density for each chopper wheel revolution (50 Hz). This

2

• Absolute carbon dioxide density (mg·m

–3

• Water vapor density (g·m

)

• Three-dimensional wind speed (m·s

–3

)

–1

; requires the CSAT3A)

• Sonic air temperature (°C; requires the CSAT3A)

• Air temperature (°C; requires an auxiliary temperature probe)

• Barometric pressure (kPa; requires an auxiliary barometer)

• Standard outputs:

o CO

density, H2O density

2

o Gas analyzer diagnostic flags
o Air temperature
o Air pressure
o CO
o H

signal strength

2

O signal strength

2

• Additional outputs from auxiliary instruments:

o u

, uy, and uz orthogonal wind components (requires the

x

CSAT3A)

o Sonic temperature (requires the CSAT3A, and is based on the

measurement of c, the speed of sound)

o Sonic diagnostic flags (from the CSAT3A)

Datalogger Compatibility: CR1000
CR3000
CR5000

Measurement

Rate: 100 Hz

ii

Output bandwidth
Output rate

ii

: 5, 10, 12.5, 20, or 25 Hz

: 10, 25 or 50 Hz

Operating temperature: −30° to 50°C

ii

user selectable

7

EC150 CO2/H2O Open-Path Gas Analyzer

Gas analyzer

iii

Measurement precision

density: 0.2 mg·m

CO

2

O density: 0.004 g·m

H

2

–3

Factory calibrated range

: 0 to 1000 µmol·mol–1

CO

2

H

O: 0 to 72 mmol/mol (37°C dewpoint)

2

Temperature: −30° to 50°C
Barometric pressure: 70 to 106 kPa

CO

performance

2

Zero max drift

iv

: ±0.55 mg·m–3·°C–1 (± 0.3

μmol·mol·°C

Gain drift: ±0.1% of reading·°C
Sensitivity to H

H

O performance

2

Zero max drift

O: ±1.1 x 10–4 µmol CO2·mol–1 H2O (max)

2

iv

: ±0.04 g·m–3·°C–1
(± 0.05 mmol·mol
Gain drift: ±0.3% of reading·°C
Sensitivity to CO

CSAT3A sonic measurement precision

: 1.0 mm·s–1

u

x

: 1.0 mm·s–1

u

y

: 0.5 mm·s–1

u

z

: ±0.1 mol H2O·mol–1 CO2 (maximum)

2

v

Sonic temperature: 0.025°C

(0.15 µmol·mol–1)

–3

(0.006 mmol·mol–1)

–1

)

–1

(maximum)

–1

·°C–1)

–1

(maximum)

CSAT3A sonic accuracy

vi

Offset error

, uy: < ±8 cm·s–1

u

x

: < ±4 cm·s–1

u

z

Gain error

Wind vector ±5° horizontal: < ±2% of reading
Wind vector ±10° horizontal: < ±3% of reading
Wind vector ±20° horizontal: < ±6% of reading

iii

noise rms, assumes:

o 25°C
o 85 kPa
o 14 g·m-3 H2O
o 597 mg·m
o 25 Hz bandwidth

iv

−30° to 50°C

v

noise rms

vi

assumes:

o −30° to +50°C
o wind speed <30 m·s
o azimuth angles between ±170°

-3

CO2

-1

8

EC150 CO2/H2O Open-Path Gas Analyzer

CSAT3 sonic reporting range

Full scale wind: ±65.6 m/s
Sonic temperature: −50° to 60°C

Auxiliary sensors

Barometer

EC150 temperature sensor

5.2 Output Signals

The EC100 electronics can output data from the EC150 by several means.

• Campbell Scientific SDM

• RS-485

• USB

• Analog out

vii

Internal basic barometer

Accuracy

−30° to 0°C: ±3.7 kPa at −30°C, falling linearly to
±1.5 kPa at 0°C

0° to 50°C: ±1.5 kPa

Measurement rate: 10.0 Hz

Optional enhanced barometer

Manufacturer: Vaisala
Model: PTB110
Accuracy: ±0.15 kPa (−30°C to 50°C)
Measurement rate: 1.0 Hz

Manufacturer: BetaTherm
Model: 100K6A1A Thermistor
Accuracy: ±0.15°C (−30

o

to 50°C)

Synchronous Device for Measurement communications protocol, or SDM, is a
proprietary serial interface developed by Campbell Scientific for
communication between a datalogger and a peripheral or sensor. In almost all
cases, SDM is the preferred communications protocol with the exception of
measurement heights requiring cable lengths greater than 100 meters. In this
case, RS-485 output is recommended. See Section 4.6.2.1, SDM Output, for
details on SDM output, see Appendix C, Alternate EC100 Outputs, for greater
detail on RS-485, USB, or analog outputs.

SDM communications are output as the FLOAT data type.

5.3 Physical Description

Optical measurement path length: 15.37 cm (6.05 in)

Spatial separation from
CSAT3A sampling volume: 5.0 cm (2.0 in)

vii

refer to manufacturer’s product brochure or manual for details

9

EC150 CO2/H2O Open-Path Gas Analyzer

Dimensions

Head housing diameter: 3.2 cm (1.3 in)
Head length: 29.7 cm (11.7 in)
EC100 enclosure: 24.1 cm x 35.6 cm x 14 cm (9.5 in x

14.0 in x 5.5 in)

Weight

Analyzer and cable: 2 kg (4.4 lbs)
EC100 electronics and
EC100 enclosure: 3.2 kg (7.0 lbs)

FIGURE 5-1. Optical path and envelope dimensions of EC150 analyzer

head

5.4 Power Requirements

Voltage supply: 10 to 16 Vdc
Power at 25°C excluding CSAT3A: 4.1 W
Power at 25°C including CSAT3A: 5.0 W
Power at 25°C in power-down mode

(CSAT3A fully powered and EC150 off): 3.0 W

10

6. Installation

NOTE

6.1 Orientation

6.2 Mounting Analyzer to Support Hardware

EC150 CO2/H2O Open-Path Gas Analyzer

During operation, the EC150 should be positioned vertically (±15°) so that the
product label reads right side up and the upper arm (source) is directly above
the lower arm (detector). If the sensor is being used with a sonic anemometer,
the anemometer should be leveled and pointed into the prevailing wind to
minimize flow distortion from the analyzer’s arms and other supporting
structures.

The EC150 is supplied with mounting hardware to attach it to the end of a
horizontal pipe of 3.33 cm (1.31 in) outer diameter, such as the CM202 (pn

17903), CM204 (pn 17904), or CM206 crossarm (pn 17905).

There are two different mounting brackets for the EC150. A head only
mounting bracket (pn 26785), and the EC150/CSAT3A mounting bracket (pn

26786). The two mounting brackets are shown in FIGURE 6-1.

The CSAT3A sonic anemometer head is an option when ordering the EC150
and the appropriate mounting bracket is included with the EC150 depending on
if the CSAT3A is ordered. If the user is already in possession of a CSAT3A
and intends to use it with the EC150, the proper mounting bracket should be
specified at time of order.

The screws and bolts for either mounting bracket are easily lost in
the field. Replacements are available through Campbell Scientific
or can be sourced elsewhere. For mounting bracket 26785, use pn
15807 (screw #8-32 x 0.250 socket head) and pn 26712 (screw
3/8-16 x 0.625 hex cap). For mounting bracket 26786, use pn
26711 (screw #8-32 x 0.250 shoulder cap) and pn 26712 (screw
3/8-16 x 0.625 hex cap).

FIGURE 6-1. Mounting bracket options for EC150 head only (pn

26785) or EC150 head with CSAT3A (pn 26786)

11

EC150 CO2/H2O Open-Path Gas Analyzer

The mounting bracket for the EC50 with CSAT3A, pn 26786, allows the intake
source of the CSAT3A and EC150 to be positioned at varying degrees up to
approximately a 5.0 cm (2.0 in) offset. The positioning and offset is illustrated
in FIGURES 6-3 and 6-4. The change in positioning allows a small but
significant difference in the flux attenuation ratio. Campbell Scientific
generally recommends that the EC150 is positioned in the most forward
position to minimize errors caused by sensor separation. The tradeoff,
however, is greater flow distortion. The effect of spatial separation on flux
attenuation is greatest at lower measurement heights as shown in FIGURE 6-2.
A Campbell Scientific application engineer can help determine the best
positioning of the EC150 relative to the CSAT3A in scenarios where the
measurement height is below 10 meters.

FIGURE 6-2. Changes in flux attenuation ratio relative to sensor height

at the most fore and aft positions

12

EC150 CO2/H2O Open-Path Gas Analyzer

FIGURE 6-3. Mounting position of CSAT3A and EC155 with a 4.9 cm

sensor separation.

FIGURE 6-4. Mounting position of CSAT3A and EC155 with a 9.7 cm

sensor separation.

The following steps describe the normal mounting procedure. Refer to
FIGURE 6-5 and 6-6 throughout this section.

13

EC150 CO2/H2O Open-Path Gas Analyzer

WARNING

6.2.1 Preparing the mounting structure

1. Secure a CM20X crossarm to a tripod or other vertical structure using a

CM210 crossarm-to-pole bracket (pn 17767).

2. Point the horizontal arm into the direction of the prevailing wind.

3. Tighten all fitting set screws.

Do not carry the EC150 by the arms or the strut between the
arms. Always hold the sensor by the block where the upper
and lower arms connect.

6.2.2 Mounting EC150 with optional CSAT3A

The guideline below gives general instructions for mounting an EC150 and
optional CSAT3A to a mounting structure. The order of assembly will
somewhat be determined by the user’s application; primarily the height of the
tower. Steps 6, 7, and 8 should be performed in sequential order.

Please refer to all steps and the referenced figure of this section before deciding
on an assembly strategy. In general, Campbell Scientific suggests that if the
equipment is to be mounted at heights above what can be reached while
standing, to preassemble as much as possible and then hoist that assembly into
a position to be mounted on the appropriate crossarm.

1. Bolt the EC150/CSAT3A mounting bracket (pn 26786; see FIGURE

6-1) to the CM250 leveling mount (pn 26559).

2. Install the CSAT3A sonic head to the EC150/CSAT3A mounting

bracket by aligning the threaded hole on the CSAT3A sonic head with
the hole on the bracket.

3. Insert and finger-tighten the bolt, making sure the bolt is not cross-

threaded. Finish tightening with a wrench.

4. Install the assembly to the end of the crossarm by fitting the leveling

mount over the end of the crossarm.

5. Tighten the set screws on the leveling mount.

6. Install the EC150 gas analyzer head to the EC150/CSAT3A mounting

bracket by tightening the mounting screw and loosely thread the
mounting bolt into the analyzer head.

7. Align the analyzer parallel with the vertical plate of the mounting

bracket and insert the mounting screw and bolt into the slot of the
mounting bracket.

8. Carefully slide the analyzer forward to the desired position. For a

more detailed discussion of positioning the EC150 relative to the
CSAT3A, see Section 6.2, Mounting Analyzer to Support Hardware.

14

EC150 CO2/H2O Open-Path Gas Analyzer

CAUTION

Avoid crashing the arms of the sensors together. The arms
of the analyzer should slide in between the claws of the
CSAT3A; the sonic head may need to be loosened and
repositioned to do this.

10. Tighten bolts and check that the analyzer is oriented vertically such

that the label is right-side-up and the upper arm (source) is directly
above the lower arm (detector).

11. If the assembly is not level, slightly loosen the bolt that holds the

mounting bracket on the leveling mount and adjust the assembly until
the leveling bubble on the top of the CSAT3A head is within the
bullseye. Retighten the bolt.

FIGURE 6-5. Exploded view of mounting CSAT3A and EC150

15

EC150 CO2/H2O Open-Path Gas Analyzer

CAUTION

EC150 Gas
Analyzer Head

EC150 Head-Only

Mounting Bracket

CM250 Leveling Mount

FIGURE 6-6. Exploded view of mounting the EC150 without the

CSAT3A

Over-tightening bolts will damage or deform mounting
hardware.

6.2.3 Mounting EC150 without CSAT3A

The instructions for mounting the EC150 without the CSAT3A should
generally follow those in Section 6.2.2, Mounting EC150 with optional
CSAT3A, but requires the use of a different mounting bracket as described
below and in Section 6.2, Mounting Analyzer to Support Hardware.

1. Bolt the EC150 head-only mounting bracket (pn 26785; see FIGURE

6-1) to the CM250 leveling mount (pn 26559).

2. Mount the EC150 gas analyzer head to the EC150 head-only

mounting bracket and follow the steps outlined in Section 6.2.2,
Mounting EC150 with Optional CSAT3A, for preassembly.

3. Mount this assembly to the end of the crossarm by fitting the leveling

mount over the end of the crossarm.

4. Tighten the set screws on the leveling mount.

5. If the assembly is not level, slightly loosen the bolt that holds the

mounting bracket on the leveling mount and adjust the assembly.
Retighten the bolt.

16