Model 11-R
GRIMM AEROSOL TECHNIK GmbH & Co.KG Seite 42 von 83
During calibration, the number in each individual channel starting with the largest is compared simulta-
neously between the reference unit and the spectrometer candidates. The calibration software can
compare 31 size channels at the same time. The statistical comparison is based on a mean value
formed from two cycles of two minutes and ten minutes. Depending on the measured particle concen-
tration, the calibration software can electronically adjust the threshold of the candidate.
Lower threshold = more particles in the channel
Higher threshold = fewer particles in the channel
The table in the illustration shows a section of the calibration with results of the calibration process,
when there are at least 3 matches between the accumulated count values of the devices and the refer-
ence unit in the respective channel size. The count values of the candidate compared to the reference
unit have to be within the allowable range with an accuracy of ± 2%. Since the particle diameter influ-
ences the particle size to the power of three, the certified accuracy for mass measuring mode is ± 5%.
The calibration software checks all relevant parameters and the quantity of calibration dust to ensure
that the concentrations lie above a certain minimum. All results are stored electronically and saved in
the database for quality assurance purposes.
Figure 3-3: Screenshot of the GRIMM calibration software during with a
reference unit and candidate (here: GRIMM Environmental Dust Monitor with 31 channels
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