| Résumé | Many aerosol instruments require calibration to make accurate measurements. A centrifugal particle mass analyzer (CPMA) and aerosol electrometer can be used to calibrate aerosol instruments that measure mass concentration. To understand the sources of uncertainty in the calibration method, two CPMA-electrometer systems were tested to measure the repeatability and intermediate precision of the system, where the repeatability is the standard deviation of several measurements using the same system over a short period of time, and the intermediate precision is the standard deviation of several measurements using different instruments with different calibrations over a long period of time. It was found that the repeatability of the CPMA and the aerosol electrometer were both 0.8%, while the intermediate precision was 1.3% and 2.2%, respectively. The intermediate precision of the aerosol electrometers determined here compares well with a broader study by national metrology institutes which determined an intermediate precision of ∼1.7%. By propagation of uncertainty, it is expected that a CPMA-electrometer system would have repeatability of 1.1% and an intermediate precision of ∼2.1%. This compares favorably to thermal-optical analysis methods which aim to measure black carbon mass concentrations for instrument calibration, which have a repeatability in the range of 8.5–20% and reproducibility in the range of 20–26% for elemental carbon. Thus, the CPMA-electrometer method may be a good alternative to existing instrument calibration procedures. |
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