The following test data was supplied by Lars Kalnajs from the Laboratory of Atmospheric and Space Physics -
University of Colorado at Boulder, CO, USA. The findings relate to comparative testing of an Aeroqual Series 500 ozone monitor
with a Thermo Electron TEI49C UV photometer conducted in Antarctica at sub-zero temperatures ~ -35° Celsius.
The Aeroqual Series 500 (S500) instrument was housed in a weather proof case (pelican case) with a secondary fan
drawing air through a FEP Teflon inlet and over the S500 sensor head. This kept the instrument out of the weather and at a
reasonably constant temperature of around -30°C. A larger battery bank and solar module was added for providing
auxiliary power. The initial calibration of the S500 before shipping to Antarctica was within <5 ppb of the Thermo Electron
TEI49C photometer at 25°C in the university laboratory. However, out on the ice (at temperatures
~ -35°C) a correction factor of 1/2.08 was applied to the raw data from the S500. This yielded very good
agreement with the TEI49C and, very impressively, did not drift over 3 months of near continuous measurements. A plot of quick
look data is shown below and compares the performance of the S500 (in red) with the TEI49C (in white(.
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Data comparison of ozone monitors at O3 mixing ratios at ~ -35ºC
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S500 (red) and TEI49C (white) plotted against time
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Aeroqual does not claim the same accuracy for its ozone sensors as UV photometers at operating temperatures below
-5°C. However, with an appropriate enclosure and correction factor determined against a reference instrument (if
required), Aeroqual instruments perform well at sub zero temperatures, exhibiting low drift and tracking similar trends to
scientific instruments with readings well within the specified accuracy level (± 8 ppb from 0 to 0.1 ppm and ±
10% from 0.1 to 0.5 ppm).
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