Operation
21
5. Start sampling aerosol with both instruments at the same time.
Note
Greater accuracy will be obtained with longer samples. The time
you permit for sampling often depends on the reference
instrument and characteristics of the measured aerosol. It may
take some time to collect sufficient aerosol onto a filter cassette
for accurate gravimetric analysis. Refer to instructions of your
reference instrument for sampling times.
6. Stop sampling with both instruments at the same time.
7. Record the D
USTTRAK™ monitor average concentration. This can be
done by viewing the sample average in the Data screen. (Data Screen is
reviewed later in this chapter)
8. Determine the mass concentration in mg/m
3
from your reference
instrument. For gravimetric sampling this means having the gravimetric
sample weighed.
Note
If you used the internal gravimetric filter in the DUSTTRAK™
Model 8530 or 8531, the flow rate used to compute the
concentration should be 2 L/min, not 3 L/min since only 2 L/min
of aerosol flow reaches the filter.
9. Compute the new calibration constant, NewCal, using the following
formula:
CurrentCal
ionConcentratDustTrak
ionConcentrat Reference
NewCal ⋅
=
10. Select Photometric from the User Cal drop down selection and enter
the NewCal factor using the onscreen controls.
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