Malvern Instruments Mastersizer X, Manual

Page: 46 / 102

The Dispersion Unit comprises an electric motor
À
that drives a stirrer
Â
and
impeller
Ã
in the dispersion tank to provide a simultaneous stirring and pumping
action. The sample is manually added to the tank using a pipette. The stirrer
Â
is
provided to agitate the sample and stop it from separating or settling. The pump
impeller
Ã
forces the sample from the sample out port
Æ
to the cell located in
the Mastersizer, via the sample tubing.
When the cell is full of sample, the pressure exerted by the pump forces the
sample through the outlet port located at the top of the cell. The sample then
passes back to the Dispersion Unit, via the sample tubing and the sample return
port
Å
.
In this way the sample is continuously agitated and kept circulating through the
cell. Note that the sample is always pumped to the cell in an upwardly direction.
This is to allow any trapped air to percolate up through the system.
On completion of a measurement the drain
Ä
is used to empty the tank, tubes
and cell under gravity.
How to make a measurement using the Accessory
As described earlier, the purpose of the Accessory is to prepare the sample and
then deliver it to the Mastersizer so that it can be measured. The measurement
stages carried out by the Mastersizer under the control of the Malvern software
include the following:
Dispersion
Unit Controller I N
S T R U
M E
N T S
Dispersion
Unit Controller I N
S T R U
M E
N T S
RPM
Stirrer Speed
1
Small
Volume
Sampl
e Dispersion
Unit
I
N
S
T
R
U
M
E
N
T
S
Small
Volume
Sampl
e Dispersion
Unit
I
N
S
T R
U
M
E
N
T
S
4
7
6
2
5
3
IL
L
3047
C H A P T E R 5
Q S S m a l l V o l u m e S a m p l e D i s p e r s i o n U n i t
P a g e 5 . 2
M A N 0 1 6 1