Patented Design
Gas analyzer and sonic anemometer in one sensor
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Overview

Campbell Scientific’s IRGASON fully integrates the open-path analyzer and sonic anemometer. Designed specifically for eddy-covariance flux measurements, the patented design is easier to install and use than separate sensors and provides increased measurement accuracy. The IRGASON simultaneously measures absolute carbon dioxide and water vapor, air temperature, barometric pressure, three-dimensional wind speed, and sonic air temperature. U.S. patent D680455

For more information about the benefits of having a co-located measurement, refer to the poster "Improved eddy flux measurements by open-path gas analyzer and sonic anemometer co-location."

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Benefits and Features

  • Combined support structure causes less flow distortion than two separate sensors
  • Truly colocated gas analyzer and sonic anemometer measurements avoids flux loss due to sensor separation
  • Synchronized gas analyzer and sonic anemometer measurements avoid the need to correct for time lag
  • Low power consumption; suitable for solar power applications
  • Measurements are temperature compensated without active heat control
  • Low noise
  • Maximum output rate of 60 Hz with 20 Hz bandwidth
  • Angled windows shed water and are tolerant to window contamination
  • Field rugged
  • Field serviceable
  • Factory calibrated over wide range of CO2, H2O, pressure and temperature in all combinations encountered in practice
  • Extensive set of diagnostic parameters
  • Fully compatible with Campbell Scientific dataloggers; field setup, configuration, and field zero and span can be accomplished directly from the datalogger
  • Sonic Temperature: determined from three acoustic paths; corrected for crosswind effects
  • Rain: innovative signal processing and transducer wicks considerably improve performance of the anemometer during precipitation events

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Detailed Description

The IRGASON has the following outputs:

  • Ux (m/s)
  • Uy (m/s)
  • Uz (m/s)
  • Sonic Temperature (°C)
  • Sonic Diagnostic
  • CO2 Density (mg/m3)
  • H2O Density (g/m3)
  • Gas Analyzer Diagnostic
  • Ambient Temperature (°C)
  • Atmospheric Pressure (kPa)
  • CO2 Signal Strength
  • H2O Signal Strength
  • Source Temperature (°C)

Specifications

General

Patent U.S. Patent No. D680455
Operating Temperature Range -30° to +50°C
Calibrated Pressure Range 70 to 106 kPa
Input Voltage Range 10 to 16 Vdc
Power 5 W (steady state and power up) at 25°C
Measurement Rate 60 Hz
Output Bandwidth 5, 10, 12.5, or 20 Hz (user-programmable)
Output Options SDM, RS-485, USB, analog (CO2 and H2O only)
Auxiliary Inputs Air temperature and pressure
Warranty 3 years or 17,500 hours of operation (whichever comes first)
Cable Length 3 m (10 ft) from IRGASON to EC100
Weight
  • 3.2 kg (7.1 lb) for EC100 electronics
  • 2.8 kg (6.1 lb) for IRGASON head and cables

Gas Analyzer

Path Length 15.37 cm (6.05 in.)
A temperature of 20°C and pressure of 101.325 kPa was used to convert mass density to concentration.

Gas Analyzer - CO2 Performance

-NOTE- A temperature of 20°C and pressure of 101.325 kPa was used to convert mass density to concentration.
Accuracy
  • Assumes the following: the gas analyzer was properly zero and spanned using the appropriate standards; CO2 span concentration was 400 ppm; H2O span dewpoint was at 12°C (16.7 ppt); zero/span temperature was 25°C; zero/span pressure was 84 kPa; subsequent measurements made at or near the span concentration; temperature is not more than ±6°C from the zero/span temperature; and ambient temperature is within the gas analyzer operating temperature range.
  • 1% (standard deviation of calibration residuals)
Precision RMS (maximum) 0.2 mg/m3 (0.15 μmol/mol)

Nominal conditions for precision verification test: 25°C, 86 kPa, 400 μmol/mol CO2, 12°C dewpoint, and 20 Hz bandwidth.
Calibrated Range 0 to 1,000 μmol/mol (0 to 3,000 μmol/mol available upon request.)
Zero Drift with Temperature (maximum) ±0.55 mg/m3/°C (±0.3 μmol/mol/°C)
Gain Drift with Temperature (maximum) ±0.1% of reading/°C
Cross Sensitivity (maximum) ±1.1 x 10-4 mol CO2/mol H2O

Gas Analyzer - H2O Performance

-NOTE- A temperature of 20°C and pressure of 101.325 kPa was used to convert mass density to concentration.
Accuracy
  • Assumes the following: the gas analyzer was properly zero and spanned using the appropriate standards; CO2 span concentration was 400 ppm; H2O span dewpoint was at 12°C (16.7 ppt); zero/span temperature was 25°C; zero/span pressure was 84 kPa; subsequent measurements made at or near the span concentration; temperature is not more than ±6°C from the zero/span temperature; and ambient temperature is within the gas analyzer operating temperature range.
  • 2% (standard deviation of calibration residuals)
Precision RMS (maximum) 0.004 g/m3 (0.006 mmol/mol)

Nominal conditions for precision verification test: 25°C, 86 kPa, 400 μmol/mol CO2, 12°C dewpoint, and 20 Hz bandwidth.
Calibrated Range 0 to 72 mmol/mol (38°C dewpoint)
Zero Drift with Temperature (maximum) ±0.037 g/m3/°C (±0.05 mmol/mol/°C)
Gain Drift with Temperature (maximum) ±0.3% of reading/°C
Cross Sensitivity (maximum) ±0.1 mol H2O/mol CO2

Sonic Anemometer - Accuracy

-NOTE- The accuracy specification for the sonic anemometer is for wind speeds < 30 m s-1 and wind angles between ±170°.
Offset Error
  • < ±8.0 cm s-1 (for ux, uy)
  • < ±4.0 cm s-1 (for uz)
  • ±0.7° while horizontal wind at 1 m s-1 (for wind direction)
Gain Error
  • < ±2% of reading (for wind vector within ±5° of horizontal)
  • < ±3% of reading (for wind vector within ±10° of horizontal)
  • < ±6% of reading (for wind vector within ±20° of horizontal)
Measurement Precision RMS
  • 1 mm s-1 (for ux, uy)
  • 0.5 mm s-1 (for uz)
  • 0.025°C (for sonic temperature)
  • 0.6°C (for wind direction)
Speed of Sound Determined from 3 acoustic paths (corrected for crosswind effects)
Rain Innovative signal processing and transducer wicks considerably improve performance of the anemometer during precipitation events.

Basic Barometer (option -BB)

Total Accuracy
  • ±3.7 kPa at -30°C, falling linearly to ±1.5 kPa at 0°C (-30° to 0°C)
  • ±1.5 kPa (0° to 50°C)
Measurement Rate 10 Hz

Enhanced Barometer (option -EB)

Manufacturer Vaisala PTB110
Total Accuracy ±0.15 kPa (-30° to +50°C)
Measurement Rate 1 Hz

Ambient Temperature

Manufacturer BetaTherm 100K6A1IA
Total Accuracy ±0.15°C (-30° to +50°C)

Compatibility

Datalogger Considerations

Compatible Dataloggers

CR200(X) Series CR800/CR850 CR1000 CR3000 CR6 CR9000X CR5000 CR300

Downloads

EC100 OS v.5.0 (557 KB) 04-30-2015

EC100 Operating System.

View Update History

ECMon v.1.6 (10.7 MB) 03-29-2016

EC100-Series Support Software.


Device Configuration Utility v.2.12 (43.9 MB) 03-11-2016

A software utility used to download operating systems and set up Campbell Scientific hardware. Also will update PakBus Graph and the Network Planner if they have been installed previously by another Campbell Scientific software package.

Known Windows XP Issue:

This software release includes Campbell Scientific USB drivers that will not install on Windows XP. To keep current with up and coming security requirements, the drivers have been signed with a SHA-256 encryption which is not supported by Windows XP. Windows XP users who have a need to install USB drivers for Campbell Scientific products can contact Campbell Scientific for an alternate solution.

View Update History

Frequently Asked Questions

Number of FAQs related to IRGASON: 17

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  1. The barometer and temperature sensor are needed because the IRGASON and EC150 have been calibrated at the factory over a range of temperatures (-30° to +50°C) and barometric pressures (70 to 106 kPa). 

  2. Selecting which barometer to use is the choice of the user. There is a direct correlation between the accuracy level of the barometer and its cost.

    • The basic barometer has an accuracy of ±1.5 kPa between 0° and 50°C.  Below 0°, the error increases linearly to ±3.7 kPa at -30°C.
    • The enhanced barometer offers an accuracy of ±0.15 kPa (-30° to +50°C).

    When choosing a barometer, consider the effect of pressure accuracy on flux calculations. For sensible heat flux, the barometric pressure is used to calculate the density of air, which directly scales the sensible heat flux. Therefore, if the barometric pressure measurement is off by 1%, then the sensible heat flux will be off by 1%.

    For CO2 flux, the EC150 and IRGASON report CO2 as density. Thus, the barometric pressure is not used to directly calculate the flux. However, error in pressure measurements could cause an error in CO2 flux resulting from a CO2 span. During the span procedure, the user enters the “true CO2 value” as a CO2 concentration, which is later converted to density using the barometric pressure. Consequently, the error in CO2 measurements is directly proportional to the error in the barometric pressure measurement.

  3. The factory calibration accounts for CO2 and H2O signal strengths down to 0.7. Therefore, to ensure quality data, windows should be cleaned before signal strengths drop below 0.7. 

  4. The power requirement for the IRGASON or EC150 with CSAT3A is 5 W at room temperature regardless of whether it is powering up or under steady-state operation.  At extreme cold or hot temperatures, the power requirement reaches 6 W.

  5. Yes. A fine-wire thermocouple, such as a FW05, can be used.

  6. The EC150 and IRGASON can report a negative water concentration if enough liquid water accumulates on the optical windows. This is because the absorption spectrum of liquid water differs from that of water vapor. Typically, large rain droplets do not cause this phenomenon. Rather, misty or condensing conditions, which create a water film across the entire optical window, can cause this phenomenon. After the water film evaporates, the former measurement accuracy will be restored.  

    The IRGASON and EC150 may also experience some amount of drift over time. If conditions are relatively dry and it has been a long time since a zero and span has been performed on the analyzer, it is possible to report a negative water vapor concentration. In this situation, perform a zero and span of the analyzer.  

  7. The EC150 and IRGASON gas analyzer windows are polished, slanted at an angle, and coated with a hydrophobic material to prevent water from collecting on their surfaces. Wicks may also be used on the windows to promote capillary action and move water away from the window edges. Also, heaters in the snouts may be turned on to help minimize data loss because of precipitation and condensation events.

  8. Campbell Scientific recommends replacing the scrubber bottles yearly. However, if the zero and span coefficients for the CO2 and H2O have drifted excessively, they may need to be replaced more often. 

  9. To zero the analyzer of an EC150 or an IRGASON, any gas that is free of CO2 or H2O, such as nitrogen gas, will work. To span CO2, use mixtures of CO2 in air.  It is important that air, not pure nitrogen, be used as the balance gas, so that the pressure-broadening characteristics match that of ambient air. Ideally, use a CO2 span gas concentration that is close to the expected concentration that will be measured at the site.

  10. EdiRe (University of Edinburgh) and MATLAB (MathWorks) are two of the products eddy-covariance customers have used to post-process their data. Others are also available. (For more information, review the EdiRe technical paper titled “EdiRe Software for Micrometeorological Applications.)

    Campbell Scientific’s default data output format is TOB1 binary, which is compatible with most post-processing software packages.  If another data format is needed, Campbell Scientific’s LoggerNet software may be used to convert TOB1 to another format.