Casella CEL Software for the Microdust dust monitor User Manual
Page 24
averages over the exposure period, one from the filter and the other provided
by the averaging function of the instrument. If differences are found between
the instruments reading and the gravimetric value, a user defined correction
factor can be loaded into the instrument for the dust type. This correction can
be applied automatically to any measured values to give optimum accuracy.
During the calibration run, it is necessary to determine the average real time
dust concentration which has been measured by the instrument. The internal
logger makes the recording and analysis of this data a simple task.
Use the following procedure to calibrate for a specific dust type.
1.
Perform the Set Zero operation and confirm that the Span is set to
the factory calibration point (Section 2.3.1).
This returns the instrument to the default calibration set by the
factory so that all user defined calibrations are relative to this setting.
This is an absolute calibration that is not affected by changes to the
correction factor.
2.
Fit the Gravimetric or Respirable adapter on to the probe and load a
pre-weighed filter into the cassette holder.
3.
Adjust the sampling pump to provide the appropriate flow rate.
The respirable adapter requires a flow rate of 2.2 l/min.
For isokinetic sampling, pump flow rate is calculated from the sample
velocity and cross sectional area of the gravimetric inlet tube (2 cm
).
For general TSP measurements, actual flow rate is not critical but will
affect the mass of the collected sample.
4.
Start gravimetric sampling and the internal logger (Section 2.5.3).
This resets the Average (T.W.A) value.
5.
Continue sampling for a period long enough to allow the collection of
sufficient sample mass.
6.
At the end of this sampling period, stop the data logger and sampling
pump.
The average real time reading is available from the display and will be
stored in the data file for the run.
7.
Note the Average (T.W.A) value.
8.
The filter should be conditioned and re-weighed to establish the
collected mass.
9.
The gravimetric density during the sampling period can be established
by dividing the mass increase by the total volume sampled.
Page 24 of 60
Operation
MICRODUST pro Aerosol Monitoring System &
WINDUST pro Application Software - Handbook