Malvern Mastersizer 2000, User Manual

Page: 49 / 154

Making measurements - a tutorial Chapter 4
Mastersizer 2000 Page 4-13
A background measurement is automatically performed when a manual
measurement is started.
„
Add Sample – this tab shows how much sample has been added to the
tank for measurement. The system measures how much sample is added
by monitoring the “obscuration”of the beam caused by the sample being
added to the dispersant. The obscuration is simply the fraction of light
“lost” from the analyser beam when the sample is introduced. For example
an obscuration of 30% means that 30% of the analyser beam has been lost
by either scattering or absorption.
The “obscuration bar”

gives a visual indication of how much sample is
added. If the bar is in the green zone then the concentration is in the cor-
rect range. If it is in the red then the concentration is out of range. The
exact obscuration is given at the bottom left of the dialogue. The instru-
ment has a wide range of concentrations that are acceptable and thus con-
centrations do not have to be precise.
The target obscuration values can be set by the user; see Chapter 9 .
„
Measure Sample – this tab displays the scattering information during the
actual measurement.
„
Result – this tab is displayed when the software is calculating the size dis-
tribution.

The measurement control buttons allow the measurement process to be con-
trolled and allow the user to document the measurement, control the disper-
sion unit and set up all the measurement parameters. The buttons are outlined
below.
„
Options – this button gives access to the measurement options. For exam-
ple, the user can specify what sample and dispersant to measure, how the
size distribution is to be calculated, and where to save the results.
„
Document – pressing this button displays a dialogue where the user can
document the measurement i.e. make notes on the pre-dispersion tech-
niques, sample quantity, etc. This allows the measurement to be repeated
at a later date.
„
Start – starts a measurement process. For example, after adding the sample
and once satisfied with the quantity, the user can start the measurement
process by pressing
Start .
„
Stop – this button stops the current measurement process.
„
Next – pressing Next automatically moves to the next logical stage of the
measurement. For example, if the user has just completed a background
measurement (and the
Pause between stages check box is enabled),
pressing Next takes them to the Add Sample tab.
MAN0384-1.0 Mastersizer 2000.book Page 13 Tuesday, March 20, 2007 8:56 AM