.
The right side of the screen  gives the option of selecting or generating a
custom presentation. The list gives a choice of four of the custom presenta-
tions available. Selecting the Request button will allow you to select an-
other custom presentation from those currently available.
There is also an option for you to enter the refractive indices of a new sample and
dispersant. When these details have been entered the software will give you the
option to:
.
Use a presentation that is the closest match from the existing presentations.
.
Calculate a new presentation based on the values within the Malvern pres-
entation grid.
.
Calculate a new presentation based on the exact values entered.
When is the presentation important?
This is a difficult question to answer and usually depends on your own
requirements. Creating a more accurate presentation can be very time consuming
and the extra amount of accuracy may be minimal. If you are unsure of the
benefit of using a different presentation it is best to try using two presentations
close to the one required and see if the difference is acceptable. For example if you
required a presentation that has not been generated, the software will tell you the
closest presentation available. If you make an analysis using this presentation and
then made a second analysis using the next available presentation (effectively
making an analysis using a presentation from both sides of the actual presentation
required) you can then examine the difference in the result. If the difference is
minimal then you should use the closest presentation available.
Remember that you can select an existing presentation and analyse the
measurement data in a few seconds - it may take over an hour to calculate a new
presentation for each lens! It is always best to check if neighboring available
presentations are acceptable before generating a new one.
There are two instances when the presentation becomes important.
Firstly, when the size of the particles within your sample are under 10 microns.
As the particles get smaller then the choice of presentation becomes more
important. In general, if the particles are over 10 microns, then one of the system
presentations will be adequate.
Secondly the presentation becomes more important as the value of the refractive
index of the sample and the dispersant become closer. In general if the refractive
index of the sample divided by the refractive index of the dispersant is greater
than 1.2 then the choice of presentation is not important - the system presentation
should be adequate.
CHAPTER 5
Getting Started
Page 5.6
MAN 0101
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