Abstract
Abstract. In contrast to the legacy manual method used to prepare, condition, and calibrate the electrochemical concentration cell (ECC) ozonesonde, an automated digital calibration bench similar to one developed by MeteoSwiss at Payerne, Switzerland, was established at NASA's Wallops Flight Facility and provides reference measurements of the same ozone partial pressure as measured by the ECC. The purpose of an automated system is to condition and calibrate ECCs before launching on a balloon. Operation of the digital calibration bench is simple and real-time graphs and summaries are available to the operator; all information is archived. The parameters of interest include ozone partial pressure, airflow, temperature, background current, response, and time (real and elapsed). ECCs, prepared with 1.0 % solution of potassium iodide (KI) and full buffer, show increasing partial pressure values when compared to the reference as partial pressures increase. Differences of approximately 5–6 % are noted at 20.0 mPa. Additional tests with different concentrations revealed the Science Pump Corp. (SPC) 6A ECC with 0.5 % KI solution and one-half buffer agreed closer to the reference than the 1.0 % cells. The information gained from the automated system allows a compilation of ECC characteristics, as well as calibrations. The digital calibration bench is recommended for ECC studies as it conserves resources.
Highlights
Measurement disagreement between similar or identical instruments seems to be a historical problem
The computer-controlled preparation and calibration bench fabricated at NASA Wallops Flight Facility borrows from the design of a bench developed by MeteoSwiss scientists Bruno A
The concept of an automated method with which to preflight condition and calibrate electrochemical concentration cell (ECC) ozonesondes was originally considered by MeteoSwiss scientists over 20 years ago
Summary
Measurement disagreement between similar or identical instruments seems to be a historical problem. Intercomparisons are generally conducted when new instruments are introduced and when operational changes or improved procedures become available Such comparisons should be made under the same environmental conditions and include a reference instrument as an aid for checking the accuracy and reliability of the instruments. The automated system can condition the ECC prior to flight and, if desired, provide calibration over a wide range of ozone partial pressures This system, designated the digital calibration bench, enables consistent conditioning and calibration of the ECC along with measurements of a reference value. Uncertainties arise from poor compensation for the loss of pump efficiency, erroneous background current, variable motor speed, solution loss from turbulent cathode cell bubbling, airflow temperature error and whether measured at the proper location, and the use of the appropriate potassium iodide (KI) concentration Understanding the influence these parameters have on the ozonesonde measurement capability is important. The digital calibration bench is able to measure these parameters in a consistent way over a range of partial pressures
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