DustMon RD 100
– Measurement using the internal control unit
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sample. This avoids “small clouds or poofs of dust” sent up when the new
sample hits the old sample thus getting a combination of the two.
•
Samples should be stored in a desiccator to prevent humidity effects. Humidity
and other agglomeration effects can affect the dust amount.
•
Making a Pre-Measurement
o
Assure sample bin is empty and clean (check to be sure no sample and dust
free)
o
Assure lab valve assembly (sample beaker, valve, drop-tube) is clean using
long handle brush.
o
Weigh 30 grams of material into a plastic weighing boat that has a pouring tip.
This will provide the best means to transfer sample to the lab valve beaker.
o
Sample preparation is not performed for these measurements.
o
Transfer sample into the lab valve beaker.
o
Press R (Run). A delay occurs for background measurement. Then a “click” is
heard as the valve opens and sample drops down the delivery pipe into the
sample chamber. Dust rises and falls again. Light obscuration measurements
are taken and data displayed as the information accumulates.
•
Decisions to make based upon pre-measurement
o
Initially there is a sharp peak. Then the peak declines as shown during the
measurement.
o
The graph will become more horizontal as measurement ensues and dust
settles.
o
When measurement is completed, note Dust Index. If greater than 50, reduce
the amount. If value is higher repeatability can suffer since dust may get
trapped in the mass falling into the bin. Best values are 4
– 12 but may be as
high as 20
– 30.
o
If dust index stays high (20
– 30 or more) and does not seem to be decreasing,
then longer measurement time is needed.
o
If dust index and the graph drops somewhat quickly, then 30 seconds may be
adequate.
o
If dust index decreases more gradually, then observe data for large differences.
o
The object is to use the shortest measuring time while showing the largest
differences in data from various samples.
o
Long measurement times are useful as an indicator of how long the dust can
remain in the air when there are no air currents or other factors that can remove
the dust.
