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EC150 CO2/H2O Open-Path Gas Analyzer
Innovative Design
Use as part of open-path eddy-covariance systems or as a stand-alone IRGA
weather applications water applications energy applications gas flux & turbulence applications infrastructure applications soil applications

Overview

Campbell Scientific’s EC150 is an open-path analyzer specifically designed for eddy-covariance flux measurements. As a stand-alone analyzer, it simultaneously measures absolute carbon-dioxide and water-vapor densities, air temperature, and barometric pressure. With the optional CSAT3A sonic anemometer head, the EC150 also measures three-dimensional wind speed and sonic air temperature.

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Benefits and Features

  • Unique optical configuration gives a slim aerodynamic shape with minimal wind distortion
  • Analyzer and sonic anemometer measurements are synchronized by a common set of electronics
  • Maximum output rate of 60 Hz with 20 Hz bandwidth
  • Low power consumption; suitable for solar power applications
  • Low noise
  • Measurements are temperature compensated without active heat control
  • Angled windows to 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
  • Speed of Sound: 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

Images

EC150 gas analyzer head with updated CSAT3A (serial numbers 2000 or greater)
EC150 gas analyzer head with updated CSAT3A (serial numbers 2000 or greater)
EC150 gas analyzer head with updated CSAT3A (serial numbers 2000 or greater)
EC150 gas analyzer head with original CSAT3A (serial numbers less than 2000)
EC150 gas analyzer head
CM250 Boom Adapter
Example open-path eddy-covariance system based on an EC150; large enclosure holds a datalogger and power supply
EC150 gas analyzer head, CSAT3A (serial numbers less than 2000), and EC100 electronics mounted to a mast
Cable ports on bottom of EC100 enclosure
EC150 with CSAT3A (original design, serial numbers less than 2000) and mounting bracket
EC100 enclosure mounting, exploded view
EC150 gas analyzer head and IRGASON & EC150 Zero & Span Shroud mounted on IRGASON & EC150 Lab Stand
EC100 electronics panel
Angled, hydrophobic windows on the EC150 improved performance in rain

Detailed Description

The CSAT3A has the following outputs:

  • Ux (m/s)*
  • Uy (m/s)*
  • Uz (m/s)*
  • Sonic Temperature (°C)*
  • Sonic Diagnostic*

The EC150 has the following outputs:

  • 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)

*The first five outputs require the CSAT3A Sonic Anemometer Head.

Specifications

Operating Temperature Range -30° to +50°C
Calibrated Pressure Range 70 to 106 kPa
Input Voltage 10 to 16 Vdc
Power 5 W (steady state and power up) at 25⁰C
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
Gas Analyzer/Sonic Volume Separation 5.0 cm (2.0 in.)
Warranty 3 years or 17,500 hours of operation (whichever comes first)
Cable Length 3 m (10 ft) from EC150 and CSAT3A to EC100
Weight
  • 2.0 kg (4.4 lb) for EC150 head and cables
  • 1.7 kg (3.7 lb) for CSAT3A head and cables
  • 3.2 kg (7.1 lb) for EC100 electronics

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/mole 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 mmol/mol (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

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° (for wind direction)
Speed of Sound Determined from 3 acoustic paths (corrected for crosswind effects)
Rain Innovative ultrasonic signal processing and user-installable wicks considerably improve the performance of the anemometer under all rain events.

Ambient Temperature

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

Compatibility

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 EC150.

Downloads

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

EC100-Series Support Software.


Device Configuration Utility v.2.14 (44.9 MB) 12-23-2016

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.

Supported Operating Systems:

Windows 10, 8, 7, Vista, and XP (Both 32 and 64 bit)

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 EC150: 17

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

  2. 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. 

  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. 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.

  5. 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.

  6. The frequency at which a zero/span should be done is highly dependent on site conditions; however, a monthly zero/span is a good starting point.  As a general guideline, monitor the optical drift of the instrument over time to determine how often a zero/span procedure needs to be performed. 

  7. 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.

  8. The IRGASON is an integrated open-path gas analyzer and sonic anemometer, whereas the EC150 is a separate open-path gas analyzer that may be paired with a CSAT3A sonic anemometer. Both instruments provide measurements that are synchronous or simultaneous, made possible by having one set of electronics, the EC100, controlling the execution of both gas and wind measurements. With its integrated design, the IRGASON is able to make measurements exactly colocated, which means that a spatial correction does not need to be applied to fluxes. Unlike the IRGASON, the EC150 has measurement volumes that have a small separation, which means a spatial correction must be applied.  

    For more detailed information, see the white paper “EC150, IRGASON, or EC155: Which CO2 and H2O Eddy-Covariance System Is Best for My Application?”   

  9. 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. 

  10. The minimum height for the IRGASON or EC150 should be approximately 2 m. Sensor placement below that height may result in a significant loss in frequency response. The maximum height depends on the available upwind fetch or footprint area.  As a general guideline for unstable boundary layer conditions, the height of the sensor should be less than the distance from the sensor to the outermost edge of the footprint area divided by one hundred. For example, if there is 500 m of available upwind fetch, the IRGASON or EC150 should not exceed a height of 5 m.  Note that for neutral and stable conditions, the footprint area will grow.

Case Studies

Alaska: Eddy Covariance
Scientists and land-use managers have long recognized the importance of forest lands for their role......read more