CEL-712 Microdust Pro Real-time Dust Monitor
34 Casella Measurement
Gravimetric calibration procedure
During the calibration, you must use the instrument’s logging feature to record
the particulate concentration measured by the instrument.
1. Follow the instructions on pages 28 to 48 to set the instrument’s zero
and span.
During the ‘Span’ setting procedure the instrument is set to the factory
default dust type. All user-defined ‘dust type’ calibrations are relative
to this setting. Following Span adjustment the instrument will revert
back to the selected dust type.
2. Fit the gravimetric or respirable adapter onto the instrument’s probe
and load a pre-weighted filter into the cassette holder.
See section 7.1 Sampling Adapters beginning on page 46 for a
description of the optional gravimetric adapters.
3. Adjust the sampling pump to provide the appropriate flow rate.
For isokinetic sampling, the flow rate is calculated from the
sample velocity and cross-sectional area of the gravimetric inlet
tube (= 200 mm²).
It may be necessary to use a smaller isokinetic inlet diameter to
avoid large flow rates.
For general Total Suspended Particulate (TSP) measurement,
the actual flow rate is not critical, but will affect the mass of the
collected sample. Typically flow rates of 1 to 2 L/min may be
used.
4. Start the gravimetric sampling (noting the start time or clear the pump
Run counter) and start the instrument’s internal data logger (refer to
section 4.2 - Starting a measurement Run for instructions to use the
instrument’s data logging feature).
The instrument calculates and records the average dust concentration
for the sampling period.
5. Continue sampling for a period that is long enough to collect sufficient
sample mass for accurate measurement on laboratory scales. At low
concentrations this may be several hours.
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