Malvern Instruments Spraytec, User Manual

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N o t e
. Using the Generate facility ensures that the size bands are distributed
as evenly as possible.
.
When the size bands shown in the table are suitable, click OK .
Curve fit
By default the Spraytec uses a model-independent analysis where the distribution
shape is allowed to vary according to the nature of the collected scattering data.
However, for comparability with results obtained using older laser diffraction
systems, the Spraytec can be set up to produce size distributions using a simple
two parameter distribution model. This is set up using the second
Analysis SOP
dialogue.
Two models are available, the Rosin-Rammler distribution and the Log-Normal
distribution. Users can select from the following options:
.
No Fit - uses the standard Spraytec analysis. This is the default setting.
.
Rosin-Rammler - uses the Rosin-Rammler two parameter distribution
model. The analysis reports the central size point ( Drr ) and distribution
width ( Nrr ) for this distribution (Chapter 10 defines these).
.
Log-Normal
- uses the Log-Normal two parameter distribution model.
The analysis reports the Geometric Mean ( Drr ) and Geometric Deviation
( Nrr ) for this distribution (Chapter 10 defines these).
For each two parameter model, specify the range over which the data fit is to be
carried out. This is specified in terms of these distribution percentiles:
.
Lower Limit – the lower percentile limit for the two parameter model fit.
By default this is set to the Dv(0).
.
Upper Limit – the upper percentile limit for the two parameter model fit.
By default this is set to the Dv(100).
These limits allow for the fact that the actual size distribution of the spray seldom
agrees with the selected model distribution, with the largest error being observed
at the tails of the distribution.
C H A P T E R 6
S p r a y t e c
P a g e 6 . 1 5