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An Autonomous Inexpensive Robust CO 2 Analyzer (AIRCOA)

An Autonomous Inexpensive Robust CO 2 Analyzer (AIRCOA). Britton Stephens, Andrew Watt, and Gordon Maclean National Center for Atmospheric Research, Boulder, Colorado, USA. NCAR CO 2 and O 2 /N 2 Calibration Facility. CO 2 signal averaged over 2.5 min. measurement cycle.

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An Autonomous Inexpensive Robust CO 2 Analyzer (AIRCOA)

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  1. An Autonomous Inexpensive Robust CO2 Analyzer (AIRCOA) Britton Stephens, Andrew Watt, and Gordon Maclean National Center for Atmospheric Research, Boulder, Colorado, USA

  2. NCAR CO2 and O2/N2 Calibration Facility

  3. CO2 signal averaged over 2.5 min. measurement cycle

  4. Calibration sequence

  5. Empirical pressure correction

  6. Empirical temperature correction SPL 9/4-9/18 NWR 9/18

  7. Drying system monitoring A change of 0.5% RH is approximately 300 ppm H2O, which would cause a dilution error of 0.1 ppm in CO2

  8. Nafion absorption effect Flow pulled through Nafion went from 300 to 50 sccm at t = 30 sec

  9. Empirical flushing correction

  10. Automated (4- or 8-hourly) leak checks A positive trend of 0.3 kPa/min would be a leak rate of 0.1 sccm which if 100 ppm different would cause a 0.1 ppm bias

  11. 13C bias test

  12. Regulator oven tests Three cylinders were in the oven and one (green dots) was not

  13. Regulator flushing tests

  14. Laboratory intercomparisons Laboratory offsets less than 0.06 ppm (1-sigma = 0.12 ppm) Field surveillance tanks Field differences from assigned values less than 0.15 ppm (1-sigma = 0.15 ppm)

  15. Automated web-based output http://www.eol.ucar.edu/~stephens/RACCOON

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