AEROCET 532 Manual Rev B
Page 18
5.3.3. K-Factors
The K-Factor for each PM mass fraction can be set in the
K-Factor
screen. A K-
Factor is a multiplier that is related to the specific gravity of the air being measured. It
improves the accuracy of the mass measurement when derived from a reference or
gravimetric device, because not all air is created equal. The accuracy of the mass
output can be affected by variations in size, color, shape, and index of refraction of the
sampled particles.
The individual user k-factors for each mass channel can be set from 0.1 to 20.0.
Figure 15 -
K-Factor
Screen
The AEROCET 532 calibration is performed using ideal polystyrene latex (PSL)
spheres, which provide a powerful tool for assessing the sensitivity, accuracy,
resolution, and false count level. The particle detector is compared to a reference mono-
dispersed (single size) suspension of PSL spheres in clean filtered air for both
calibration and certification of performance specifications. This calibration technique
provides a standard traceable reference and a measure of how well the unit maintains
its reproducibility.
Calculate the K-Factor for each particulate size fraction as the reference concentration
divided by the AEROCET 532 light scatter concentration over the same time period. For
example, if the reference total concentration was 51 μg/m
3
and the AEROCET total
concentration was 38 μg/m
3
, then the K-Factor would be 51 divided by 38 or 1.34.
The K-Factor is only valid at the same site and for the same particulate type. If the local
particulate source changes, the K-Factor may no longer be valid.
