Patented Design
Gas analyzer and sonic anemometer in one sensor
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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."

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


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)



  • 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 at 25°C: 5 W (steady state and power up) 
  • 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
  • Cable Length: 3 m (10 ft) from IRGASON to EC100
  • Warranty: 3 years or 17,500 hours of operation, whichever comes first
  • Weight
    • IRGASON Head and Cables:
      2.8 kg (6.1 lb)
    • EC100 Electronics: 3.2 kg (7.1 lb)

Gas Analyzerb,c

  • Path Length: 15.37 cm (6.05 in.)
  • CO2 Performance
    • Accuracyd: 1%e
    • Precision RMS (maximum)f: 0.2 mg/m3 (0.15 μmol/mol)
    • Calibrated Range: 0 to 1,000 μmol/molg
    • 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
  • H2O Performance
    • Accuracyd: 2%e
    • Precision RMS (maximum)f: 0.004 g/m3 (0.006 mmol/mol)
    • 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 Accuracyb, h

  • Offset Error
    • ux, uy: < ±8.0 cm s-1
    • uz: < ±4.0 cm s-1
    • Wind Direction: ±0.7° while horizontal wind at 1 m s-1
  • Gain Error
    • Wind vector within ±5° of horizontal:
      < ±2% of reading
    • Wind vector within ±10° of horizontal:
      < ±3% of reading
    • Wind vector within ±20° of horizontal:
      < ±6% of reading
  • Measurement Precision RMS
    • ux, uy: 1 mm s-1
    • uz: 0.5 mm s-1
    • Sonic Temperature: 0.025°C
    • Wind Direction: 0.6°C
  • Speed of Sound: Determined from 3 acoustic paths; corrected for crosswind effects
  • Rain: Innovative signal processing and transducer wicks considerably improves performance of the anemometer during precipitation events

Basic Barometer (option -BB)b

  • 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)b

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

Ambient Temperatureb

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

Specifications are subject to change without notice.

cA temperature of 20°C and pressure of 101.325 kPa was used to convert mass density to concentration.

dAssumes the gas analzyer 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.

eStandard deviation of calibration residuals.

fNominal conditions for precision verification test: 25°C, 86 kPa, 400 μmol/mol CO2, 12°C dewpoint, and 20 Hz bandwidth.

g0 to 3,000 μmol/mol available upon request.

hThe accuracy specification for the sonic anemometer is for wind speeds
< 30 m s-1 and wind angles between ±170°.


Datalogger Considerations

Compatible Contemporary Dataloggers

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

Compatible Retired Dataloggers

The CR5000 is the only retired datalogger that is compatible with the IRGASON.


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

EC100 Operating System.

View Update History

ECMon v.1.5 (8.65 MB) 04-22-2014

EC100-Series Support Software.

Device Configuration Utility v.2.11 (40.0 MB) 01-25-2016

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.

View Update History

Frequently Asked Questions

Number of FAQs related to IRGASON: 17

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  1. 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.

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

  3. 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). 

  4. 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. 

  5. 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.  

  6. 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.

  7. For greatest accuracy, Campbell Scientific recommends that a zero and a span be done on the EC150 or IRGASON. However, if a span gas is difficult to obtain, at the minimum, perform a zero on the analyzer.  Performing a zero will correct the majority of drift experienced by the analyzer. Follow the zero procedure in the analyzer’s manual for details.

  8. 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.

  9. 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. 

  10. Factory recalibration is done on an as-needed basis. When diagnostic flags begin to appear and persist even after cleaning the analyzer and verifying its settings, a recalibration is needed. Additionally, if the performance of the analyzer has degraded, a recalibration is recommended.  

    One performance test is to check the absolute signal strength drift over the course of 1 year. Drift of a few percent per year is normal. If the annual signal strength drift is excessive, or if the signal strength is below 0.7 when the windows are clean, a factory recalibration is needed. Furthermore, if the ratio of the CO2 to H2O signal strength is not close to one, it may also be time for a factory recalibration.