PERFORMANCE, APPLICATIONS AND FIELD EXPERIENCES OF A COMPACT

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    PERFORMANCE, APPLICATIONS AND FIELD                                                                                                                                                                                                                                                                   Matti Hohtola
                                                                                                                                                                                                                                                                                                         Marko Jalonen
    EXPERIENCES OF A COMPACT CARBON DIOXIDE                                                                                                                                                                                                                                                               Mikko Laakso
                                                                                                                                                                                                                                                                                                            Ulla Mattila
    MEASUREMENT PROBE FOR OUTDOOR USE                                                                                                                                                                                                                                                              Sebastian Schimmack
                                                                                                                                                                                                                                                                                                         Maria Uusimaa
                                                                                                                                                                                                                                                                                                             Vaisala Oyj


    Vaisala CARBOCAP® technology                                                         Calibration of the GMP343                                                                                                              Direct in-soil measurement with buried GMP343 probe


    ■ Vaisala CARBOCAP® technology is based on the single-beam                           ■ The Vaisala GMP343 probe is calibrated according to NMI
      dual-wavelength NDIR principle                                                       (National Metrology Institute) and ISO9001 standards
    ■ An infrared (IR) light source emits a beam through the gas to                      ■ Each probe is calibrated at four different temperatures (-30,                                                                                                                                                   Sealed joints
      be measured, which is absorbed by any existent CO2 and the                           0, +25 and +50°C) and seven CO2 concentrations (0, 200, 370,
      IR light passes through to the IR detector.                                          600, 1000, and 4000 ppmCO2, 2% CO2)
    ■ Unique in the Vaisala CARBOCAP® is the use of a siliconed                          ■ NMI traceable calibration gases are used
      micro-machined Fabry-Perot Interferometer (FPI) to shift to
      a wavelength where no absorption occurs.
    ■ Comparing the reference signal to the absorbed signal
      indicates the concentration level of CO2 in the measured
      gas.
                                               Temperature     Heated gold plated and
                                                                                                                                                                                                                                  Open-ended caps                Horizontal diffusion slot: facing
                                                 sensor        thin film coated mirror                                                                                                                                          An illustration of in-soil CO2 measurement using the GMP343

                                                                                                                                                                                                                                                                   CO2 concentration in soil at different dephts
                          Miniature filament                   Light absorbed                                                                                                                                                                                     GMP343 (-2cm)   GMP343 (-7cm)    GMP343 (-15cm)     GMP343 (-22cm)
                          lamp (electrically                       by gas
                                                                                                                                                                                                                                                           5000
                               pulsed)
                                                                                                                                                                                                                                                           4500

                                                                                                                                                                                                                                                           4000


                                    FPI                                                                                                                                                                                                                    3500
        IP67 (Nema 6) sealed      detector                                                                                                                                                                                         ppmCO2                  3000
        housing
                                                                                                                                                                                                                                                           2500

                                                                                         Calibration station for the simultaneous calibration of 10 probes                                                                                                 2000

                                                                                                                                                                                                                                                           1500

                                                Heated sapphire                                                                                                                                                                                            1000

                                                    window                                                                                      Temperature dependency of Vaisala GMP343 CO2 probe at 4                                                    500

                                                                                                                                                   calibration points (200, 370, 600 and 1000 ppmCO2)
    Structure of a Vaisala GMP343 CO2 probe                                                                                                                                                                                                                  0




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                                                                                             Temperature dependency (% of Reading)




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                                                                                                                                       2                                                                                                                                                          Date
                                                                                                                                     1.5                                                                             GMP343_1
                                                                                                                                                                                                                     GMP343_2
    Hermetically sealed cap
                                                                                                                                       1
                                                                                                                                                                                                                     GMP343_3   Three-year term of CO2 measurement in soil at different depths
                                                                                                                                                                                                    accuracy range




                                                                                                                                     0.5                                                                             GMP343_4
                                                                                                                                       0                                                                             GMP343_5


           tunable FPI filter
                                                                                                                                     -0.5                                                                            GMP343_6
                                                                                                                                                                                                                     GMP343_7
                                                                                                                                                                                                                                Long term atmospheric measurement with Vaisala
                                                  Structure of the FPI detector                                                       -1
                                                                                                                                                                                                                     GMP343_8   GMP343 CO2 probe at Kenttärova station
                                                                                                                                     -1.5
                  IR detector                                                                                                                                                                                        GMP343_9
                                                                                                                                      -2                                                                                        Kenttärova station is studying the carbon dioxide and energy
                                                                                                                                     -2.5
                                                                                                                                            0       200      400         600          800   1000   1200
                                                                                                                                                                                                                                fluxes in the atmosphere at a Norwegian spruce forest. Gas samples
                                                                                                                                                              Gas concentration (ppm CO2)                                       were taken at different heights on a 20m high measurement
                                                                                                                                                                                                                                tower, and conveyed to a LiCor-7000 gas analyser inside a
                                                                                         The temperature dependency of nine GMP343 CO2 probes at four                                                                           climate controlled building.
                                                                                         different calibration points. Measurements were taken at temperatures                                                                   To achieve most accurate measurements the LiCor-7000 was
                                                                                         of -30, 0, +25 and 50°C. The temperature accuracy of the GMP343 (in the                                                                calibrated against accredited calibration gases every 3 hours.
                                                                                         0...1000ppm range) is specified as being ± 2 % of readings.                                                                             Simultaneously measurements with the GMP343 diffusion
        Transmission                                                                                                                                                                                                            aspirated CO2 probe was installed outside at the tower. During
                                      CO2 absorption                                                                                                                                                                            the six-month term test the GMP343 readings correlated well with
          100
            90                                                                           Examples of GMP343 applications                                                                                                        those of the LiCor-7000 reference.
            80
                                                                                                                                                                                                                                                                  CO2 efflux measurements at Kenttarova station
            70                                                                           Long term equilibrium sampling in soil, snow and                                                                                                                                              GMP-343 diff      LiCor-7000

            60                                                                           aquatic ecosystem                                                                                                                                      450

            50
            40                                                                           Direct measurement of dissolved CO2 in water                                                                                                           400



            30                                                                           ■ Determine transfer of CO2 between water and atmosphere
                                                                                                                                                                                                                                                350
                                                                                                                                                                                                                                 ppm CO2




            20                                                                           ■ Calculation of metabolic rates of aquatic communities
            10                                                                           Direct measurement of CO2 efflux in soil                                                                                                                 300



             0                                                                           ■ Determine amount of CO2 produced in different soil layers                                                                                             250

                 3.5                  4                  4.5                    5
                                                                                         ■ Investigate the transport of CO2 between the different layers
                                 Wavelength (micrometers)                                   up to the atmosphere
                                                                                                                                                                                                                                                200
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                                                                                                                                                                                                                                                 38 .91


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                                                                                         Direct measurement of CO2 in snow
                                                                                                                                                                                                                                           72
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                                                                                                                                                                                                                                                                                               Date
                                                                                         ■ Determine the CO2 diffusion rate at different depth of the
    Measurement at CO2 absorption wavelength and at a reference                             continuous snow layer                                                                                                               Readings of a GMP343 and a LiCor-7000 reference during a six-month
    wavelength
                                                                                                                                                                                                                                term test

                                                                                                                                                                                                                                Conclusions
    Vaisala CARBOCAP® Carbon Dioxide Probe                                                                                                                                                                                      The Vaisala CARBOCAP® Carbon Dioxide Probe GMP343 is
    GMP343 for outdoor CO2 measurement                                                                                                                                                                                          a compact, lightweight and cost efficient CO 2 measurement
                                                                                                                                                                                                                                instrument for ecological research.
                                                                                                                                                                                                                                Results from long term tests prove the usability of the probe in
    ■ Small and rugged probe for ecological measurement                                                                                                                                                                         applications like CO2 efflux measurement and medium accuracy
    ■ Diffusion-aspirated probe to avoid bulky and power-                                                                                                                                                                       atmospheric measurement.
      consuming sampling systems
    ■ IP67/66 classified body – suitable for harsh environments
                                                                                                                                                                                                                                Acknowledgements
                                                                                                                                                                                                                                ■ Prof. Pertti Hari and Dr. Jukka Pumpanen, Department of
                                                                                                                                                                                                                                  Forest Ecology, University of Helsinki
                                                                                                                                                                                                                                ■ Dr. Anne Ojala, M. Sc. Liisa Kulmala and M Sc. Jussi Huotari,
                                                                                         Schematic diagram of equilibrium sampling setup                                                                                          Department of Ecological and Environmental Sciences,
                                                                                                                                                                                                                                  University of Helsinki
                                                                                                                                                                                                                                ■ M Sc. Juha Hatakka, Finnish Meteorological Institute - Climate
                                                                                                                                                                                                                                  and Global Change




    The Vaisala CARBOCAP® Carbon Dioxide Probe GMP343 Diffusion and
    Flow through probes                                                                  Equilibrium sampling system for soil installation