Chapter 3 Software features
Page 3-12 MAN 0386
Note
Application Notes available at www.Malvern.com describe the process
of method development for dry powder dispersion, including selection of
obscuration limits.
Autostart
Autostart is used to ensure that no measurements are started until the dispersion is
stable. Dry measurements always exhibit a range of fluctuation so the Autostart
feature is not generally used for these.
Obscuration filtering
This facility is particularly useful when the sample concentration is liable to some
degree of fluctuation as is often the case with dry powder measurements. Selecting
the Only include snaps with values within obscuration limits check box
effectively turns on the obscuration limits set in
above.
For dry powder measurements practical limits are 0.5% and 6% but exact settings
can only be found by experimentation.
In the event that a totally inappropriate feed rate is set so that the obscuration sel-
dom (if ever) falls within the desired limits, a time-out allows the user to exit the
measurement. Do not set this so long as to give the measurement routine the
appearance of having hung up, but it should be sufficiently long to allow a fair
chance of sample of the required concentration passing through the measurement
zone.
The user is strongly advised to adjust the feed rate so that the obscuration falls
between the preset limits for the duration of the measurement.
If a measurement times out the number of measurement snaps is recorded e.g. it
will be reported that “1760 of 2000snaps” were captured.
Red Only Measurement
The options on this tab are not available as the blue light source is not used for dry
powder measurements.
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MAN0386-1.0 Scirocco 2000.book Page 12 Friday, March 16, 2007 4:15 PM
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