Campbell IRGASON User manual

Revision: 08/2021
Copyright © 2010 – 2021
Campbell Scientific, Inc.
Product Manual

Table of contents
1. Introduction 1
2. Precautions 1
3. Initial inspection 2
4. Overview 2
5. Specifications 3
5.1 Measurements 3
5.2 Output signals 6
5.3 Physical description 8
5.4 Power requirements during power up and operation 11
6. Installation 11
6.1 Orientation 11
6.2 Mounting 12
6.3 Wiring and connections 15
7. Settings 19
7.1 Factory defaults 20
7.2 Bandwidth 20
7.3 SDM address 21
7.4 Unprompted output 21
7.5 Unprompted output rate 21
7.6 RS-485 baud rate 21
7.7 Analog output 21
7.8 ECMon update rate 21
7.9 Temperature sensor 22
7.10 Fixed temperature value 22
7.11 Pressure sensor 22
7.11.1 Pressure gain 22
7.11.2 Pressure offset 22
7.11.3 Fixed pressure value 23
7.12 Pressure differential enable 23
7.13 Heater control 23
Table of Contents - i

7.14 ECMon 24
7.15 Device Configuration Utility 26
8. EC100 outputs 27
8.1 SDM output 27
8.2 USB or RS-485 output 28
8.3 Analog outputs 30
9. Maintenance 31
9.1 Routine maintenance 31
9.2 Wick maintenance 32
9.2.1 Sonic wicks 32
9.2.2 Gas analyzer wicks 33
9.3 Gas analyzer window cleaning 34
9.4 Zero and span 34
9.5 Replacing desiccant and scrubber bottles 40
9.6 Factory recalibration 41
10. Data collection and data processing 42
10.1 Data collection and processing with EasyFluxDL 43
10.2 Data logger programming with CRBasic 45
10.2.1 EC100() instruction 46
10.3 EC100Configure() instruction 49
10.3.1 ConfigCmd 11 zero-and-span control 51
10.3.2 ConfigCmd 18 heater voltage 52
10.4 Example CRBasic program 53
11. Theory of operation 54
11.1 IRGASON sonic anemometer 54
11.1.1 Wind speed 54
11.1.2 Temperature 55
11.2 IRGASON gas analyzer 56
12. References 57
Appendix A. Filter bandwidth and time delay 58
Appendix B. Sonic anemometer orientation 61
B.1 Determining true north and sensor orientation 61
B.2 Online magnetic declination calculator 62
Table of Contents - ii

Appendix C. Equations 64
Appendix D. Safety data sheets (SDS) 67
D.1 Molecular sieve, Type 13X 68
D.2 Magnesium perchlorate 72
D.3 Decarbite 79
Appendix E. IRGASON packing information 83
Table of Contents - iii

1. Introduction
The IRGASON, U.S. Des. Patent No. D680455, is an in situ, open-path, mid-infrared absorption
gas analyzer integrated with a three-dimensional sonic anemometer. The gas analyzer provides
measurements of absolute densities of carbon dioxide and water vapor, while the sonic
anemometer measures orthogonal wind components.
Before using the IRGASON please study:
lPrecautions (p. 1)
lInitial inspection (p. 2)
lInstallation (p. 11)
More details are available in the remaining sections.
2. Precautions
lDANGER:
oThe scrubber bottles of all IRGASON instruments shipped prior to July 2017 contain
the strong oxidizing agents sodium hydroxide (caustic soda, NaOH) and anhydrous
magnesium perchlorate (Mg(ClO4)2). If you are handling or exchanging the scrubber
bottles (see Replacing desiccant and scrubber bottles (p. 40)), use the following
precautions. IRGASON instrument shipped after July 2017, contain a 13X molecular
sieve instead.
nAvoid direct contact with the chemicals.
nEnsure your work area is well ventilated and free of reactive compounds,
including liquid water.
nStore used chemical bottles in a sealed container until disposal.
nDispose of chemicals and bottles properly.
nSafety Data Sheets (SDS) are provided in Safety data sheets (SDS) (p. 67). SDS
are updated periodically by chemical manufacturers. Obtain current SDS at
www.campbellsci.com .
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 1

lWARNING:
oDo not carry the IRGASON by the arms or the strut between the arms. Always hold it
by the block, where the upper and lower arms connect.
oHandle the IRGASON carefully. The optical source may be damaged by rough
handling, especially while the analyzer is powered.
oOvertightening bolts will damage or deform the mounting hardware.
lCAUTION:
oGrounding the EC100 measurement electronics is critical. Proper grounding to earth
(chassis) will ensure maximum ESD (electrostatic discharge) protection and improve
measurement accuracy.
oDo not connect or disconnect the gas analyzer or sonic connectors while the EC100 is
powered.
oThe SDM, USB, and RS-485 output options include IRGASON diagnostic data. Be
aware that the absence of diagnostic data in the analog output option could make
troubleshooting difficult and may lead to the user not being aware of potential
problems with the instrumentation (see EC100 outputs (p. 27)).
oResting the analyzer on its side during the zero-and-span procedure may result in
measurement inaccuracy.
oWhen cleaning the gas-analyzer window, make sure the alcohol and any residual
water completely evaporate before proceeding with the zero-and-span procedure
(see Gas analyzer window cleaning (p. 34)).
3. Initial inspection
Upon receipt of the IRGASON, inspect the packaging and contents for damage. File damage
claims with the shipping company.
4. Overview
The IRGASON is an in situ, open-path, mid-infrared absorption analyzer integrated with a three-
dimensional sonic anemometer. The gas analyzer provides measurements of absolute densities
of carbon dioxide and water vapor, while the sonic anemometer measures orthogonal wind
components.
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 2

The IRGASON is measured and controlled by the EC100 electronics, which synchronizes gas and
wind data, essential for valid flux calculations using the eddy-covariance method. The EC100
electronics also uses inputs from an included temperature thermistor probe and a barometer.
“IRGASON” and “EC100” are often used interchangeably in this manual.
The IRGASON has been optimized for remote eddy-covariance flux applications, addressing
issues of aerodynamics, power consumption, spatial displacement, and temporal synchronicity.
Specifically, its unique design contains no obstructions surrounding the sample volume; it
operates with only 5W of power at room temperature; it has no spatial displacement between
the sample volumes of the gas analyzer and the sonic anemometer; and the EC100
synchronously samples data from the gas analyzer and sonic anemometer.
5. Specifications
5.1 Measurements
Features
lTo compute carbon dioxide and water vapor fluxes using the eddy-covariance method, the
IRGASON measures:
oabsolute carbon dioxide
owater vapor densities
othree-dimensional wind speed
osonic air temperature
oair temperature
obarometric pressure
These measurements are required to compute carbon dioxide and water vapor fluxes using the:
lStandard outputs:
oux, uy, and uzorthogonal wind components
osonic temperature (based on the measurement of c, the speed of sound)
osonic diagnostic flags
oCO2density, H2O density
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 3

ogas analyzer diagnostic flags
oair temperature, air pressure
oCO2signal strength, H2O signal strength
oAir temperature and air pressure are auxiliary sensor inputs
Data logger compatibility: CR6
CR1000
CR3000
CR5000
Measurement
Rate: 60 Hz
Output bandwidth1/:5, 10, 12.5, or 20 Hz
Data logger-prompted output rate: 1 to 60 Hz
Output rate1/:10, 25 or 50 Hz
Operating temperature: –30 to 50 °C
Gas analyzer
Measurement precision2/
CO2density: 0.2 mgCO2·m–3 (0.15 µmolCO2·mol–1)
H2O density: 0.00350 gH2O·m–3 (0.006 mmolH2O·mol–1)
Factory calibrated range
CO2:0 to 1000 µmolCO2·mol–1
H2O: 0 mmolH2O·mol–1 to 37 °C dewpoint
Analyzer temp: –30 to 50 °C
Baro pressure: 70 to 106 kPa
CO2performance
Zero max drift3/:±0.55 mgCO2·m–3·°C–1 (±0.3 μmolCO2·mol·°C–1)
Gain Drift: ±0.1% of reading·µmolCO2·mol–1 °C–1 (maximum)
Sensitivity to H2O: ±1.1 x 10–4 µmolCO2·mol–1 mmolH2O (max)
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 4

H2O performance
Zero max drift3/:±0.037 gH2O·m–3·°C–1 (±0.05 mmolH2O·mol–1·°C–1)
Gain Drift: ±0.3% of reading·mmolH2O mol–1 °C–1 (maximum)
Sensitivity to CO2:±0.1 mmolH2O·mol–1 µmolCO2–1 (maximum)
Sonic measurement precision4/
ux:1 mm·s–1
uy:1 mm·s–1
uz:0.5 mm·s–1
Sonic temperature: 0.025 °C
Sonic accuracy5/
Offset error
ux, uy:< ±8 cm·s–1
uz:< 4 cm·s–1
Gain error
Wind vector ±5° horizontal: < ±2% of reading
Wind vector ±10° horizontal: < ±3% of reading
Wind vector ±20° horizontal: < ±6% of reading
Sonic reporting range
Full scale wind: ±65.553 m/s
Sonic temperature: –50 to 60 °C
Auxiliary sensors6/
Barometer
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 Hz
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 5

Optional enhanced barometer
Manufacturer: Vaisala
Model: PTB110
Accuracy
–30 to 0 °C: ±0.15 kPa
Measurement rate: 1 Hz
IRGASON temperature sensor
Manufacturer: BetaTherm
Model: 100K6A1A Thermistor
Accuracy: ±0.15 °C (–30 to 50 °C)
1/ user selectable
2/ noise rms, assumes:
l25 °C
l85 kPa
l14 g·m–3 H2O
l597 mg·m–3 CO2
l20 Hz bandwidth
3/ – 30 to 50 °C
4/ noise rms
5/ assumes:
l–30 to 50 °C
lwind speed <30 m·s–1
lazimuth angles between ±170°
6/ refer to manufacturer’s product brochure or manual for details
5.2 Output signals
Features
lEC100 electronics outputs data using:
oCS SDM
oRS-4857/
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 6

oUSB7/
oAnalog out7/
Digital
SDM (Synchronous Device for
Measurement)8/
Data type: FLOAT
RS-485
Data type: ASCII
Output rate: 10, 20 or 60 Hz7/
Baud rate: 1200 to 230400 bps7/
USB
Data type: ASCII
Output rate: 10, 20, or 60 Hz7/
Analog (two outputs for CO2and
H2O densities)
Voltage range: 0 mV to 5000 mV
Resolution: 76 µV (16 bit)
Update rate: 60 Hz
Accuracy (at 25 °C): ±3 mV
CO2density equation: mg·m–3 = 0.38632· (mVout) – 102.59
Full scale range: – 103 to 1829 mg·m–3
H2O density equation: g·m–3 = 0.00865· (mVout) – 2.26
Full scale range: – 2 to 41 g·m–3
7/ user selectable
8/ Synchronous Device for Measurement. A Campbell Scientific, Inc. proprietary serial interface for data logger to
peripheral and sensor communication. See SDM output (p. 27) for details.
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 7

5.3 Physical description
Optical path length: 15.37 cm (6.05 in)
Sonic path length: 10.0 cm (3.9 in)
Sonic path angle from vertical: 30°
Spatial separation between gas
analyzer and sonic volumes: 0 cm
Dimensions
IRGASON
Length: 51.5 cm (20.3 in)
Height: 31.1 cm (12.2 in)
Cable Length: 3 m (9.8 ft)
EC100 Enclosure: 24.1 x 35.6 x 14 cm (9.5 x 14.0 x 5.5 in)
Weight
IRGASON with cable: 2.8 kg (6.1 lbs)
EC100 with enclosure: 3.2 kg (7.1 lbs)
Designed EC100 ingress protection
rating:
IP65
Designed IRGASON ingress
protection rating:
IP67
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 8

FIGURE 5-1. IRGASON dimensions, side view
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 9

FIGURE 5-2. IRGASON dimensions, front view
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 10

5.4 Power requirements during power up
and operation
Power requirement
Source: 10 to 16 VDC
Load
at 25 °C: 420 mA
at 25 °C in power-down mode9/:250 mA
9/ sonic anemometer fully powered and gas analyzer in standby
6. Installation
6.1 Orientation
During operation, the IRGASON should be leveled and pointed into the prevailing wind to
minimize flow distortions from the instrument arms and other supporting structures. Leveling
can be done using the leveling bubble on top of the instrument block. In the proper orientation,
the product label will read right-side-up, with the upper arm (source) of the gas analyzer directly
above the lower arm (detector).
If the IRGASON is to be used in a marine environment, or in an environment where it is exposed
to corrosive chemicals (for example, the sulfur-containing compounds in viticulture), attempt to
mount the IRGASON in a way that reduces the exposure of the sonic transducers to saltwater or
corrosive chemicals. In marine or viticulture environments, the sonic transducers are expected to
age more quickly and require replacement sooner than a unit deployed in an inland, chemical-
free environment.
NOTE:
The ingress protection rating of the EC100 is not optimal for marine environments or other
environments in which the enclosure may come in contact with corrosive chemicals
(viticulture or agriculture, for example), as components within the enclosure are at higher risk
to exposure to these substances. However, instruments with EC100 enclosures are being used
in these environments with additional precautions. If the instrumentation is intended for such
an environment, contact Campbell Scientific for guidance before deploying the instrument.
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 11

6.2 Mounting
The IRGASON is supplied with mounting hardware to attach it to the end of a horizontal pipe
with a diameter of 1.3 in., such as the Campbell Scientific CM202, CM204, or CM206 crossarm.
The following steps describe the normal mounting procedure. Refer to FIGURE 6-1 (p. 13).
1. Secure the chosen crossarm to a tripod or other vertical structure using a CM210 Crossarm-
to-Pole mounting kit.
2. Point the horizontal arm into the direction of the prevailing wind and tighten the nuts and
bolts.
WARNING:
Do not carry the IRGASON by the arms or the strut between the arms. Always hold it by
the block, where the upper and lower arms connect.
3. Bolt the IRGASON mounting bracket to the CM250 leveling mount (see FIGURE 6-1 (p. 13)).
4. Install the IRGASON to the mounting bracket by inserting the mounting bolt and pin into
the corresponding holes. Tighten the bolt. Make sure the analyzer is vertically oriented so
the label is right-side-up and the upper arm (source) is directly above the lower arm
(detector). The sonic anemometer must be oriented in a way that it faces the prevailing
wind to prevent ‘shadowing’ from the sensor body. See Data collection and processing with
EasyFluxDL (p. 43) for additional information about the wind information reported by the
sonic coordinate system.
5. Mount the IRGASON assembly by fitting the boom adapter over the end of the crossarm.
Tighten the set screws on the boom adapter with a 3/16-inch hex socket head wrench.
WARNING:
Handle the IRGASON carefully. The optical source may be damaged by rough handling,
especially while the analyzer is powered.
6. If the assembly is not level, slightly loosen the bolt that holds the mounting bracket on the
boom adapter and adjust the assembly until the leveling bubble on top of the IRGASON
block is within the bullseye. Retighten the bolt.
7. Attach the EC100 enclosure to the mast, tripod leg, or other part of the mounting structure.
To do this, attach the EC100-enclosure mounting bracket to the pipe by loosely tightening
the u-bolts around the pipe. The u-bolts are found in the mesh pocket inside the EC100
enclosure. If the pipe does not run vertically (for example, if the enclosure is being attached
to a leg of a tripod), rotate the bracket to the side of the pipe. The enclosure must hang
upright. Make angle adjustments as needed by loosening the four nuts and rotating the
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 12

bracket plates relative to one another. If the necessary angle cannot be achieved in the
given orientation, the four nuts may be removed and the top plate indexed by 90° to allow
the bracket to travel in the other direction (see FIGURE 6-2 (p. 14)). Once adjusted, tighten
all the nuts. Finally, attach the EC100 enclosure to the bracket by loosening the bolts on the
back of the enclosure, hanging the enclosure on the mounting bracket (it should slide into
place and be able to securely hang from the bracket), and tightening the bolts (see FIGURE
6-3 (p. 14)).
FIGURE 6-1. Exploded view of mounting the IRGASON
WARNING:
Overtightening bolts will damage or deform the mounting hardware.
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 13

FIGURE 6-2. EC100-enclosure mounting bracket mounted on a vertical mast (left)
and a tripod leg (right)
FIGURE 6-3. Exploded view of mounting the EC100 enclosure
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 14

8. Mount the IRGASON temperature probe so that it measures temperature at the same
height as the sample volume of the IRGASON. To do this, first attach the 6-plate solar
radiation shield to the mast with the included u-bolt. Next, insert the end of the probe into
the hole on the bottom of the shield. Tighten the screws to hold the probe in place, as
shown in 6.2 (p. 12). For more detailed information about the temperature probe
installation and specifications, refer to the Model 107 Temperature Probe manual, which is
available at www.campbellsci.com .
9. Remove the EC100- enclosure desiccant from the plastic bag and place it in the mesh
pocket of the enclosure. Attach the humidity indicator card to the inside of the enclosure.
FIGURE 6-4. Mounting the IRGASON temperature probe
6.3 Wiring and connections
FIGURE 6-5 (p. 16), FIGURE 6-6 (p. 17), FIGURE 6-7 (p. 17) show the EC100 electronics panel, the
bottom of the EC100 enclosure, and sensor connections to the EC100, respectively. Refer to these
figures during wiring and connecting.
1. Find the thicker black cable coming from the block of the IRGASON. This is the IRGASON
gas-analyzer cable. Connect this cable to the EC100 electronics by removing the EC100
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 15

black-rubber cable entry plug on the bottom right of the EC100 enclosure. Store the plug in
the mesh pocket of the enclosure.
2. Insert the cable entry plug that is attached to the cable into the vacant slot. Push the
connector at the end of the cable onto its mating connector (labeled Gas Analyzer) and
tighten the thumbscrews (see FIGURE 6-5 (p. 16)). The gas analyzer cable is approximately 3
m (9.8 ft) in length.
3. Connect the IRGASON sonic cable. Similar to (a), begin by removing the black rubber cable
entry plug found on the bottom left of the EC100 enclosure. Insert the cable entry plug on
the cable into the slot and connect the male end to the female connector labeled Sonic
Anemometer on the EC100 electronics (see FIGURE 6-5 (p. 16)). The sonic cable is
approximately 3 m (9.8 ft) in length.
FIGURE 6-5. EC100 electronics front panel with enhanced barometer. At left, as
received from Campbell Scientific. At right, all wiring and connections complete.
IRGASON® Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 16