Beckman Coulter Multisizer 4, User Manual

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PN A51387A
B
4-20
Selecting Analysis Settings: SOM and SOP
Using a Standard Operating Method (SOM)
3. Select Show Details to see detailed blockage detection settings. The window expands.
The expanded Blockage Detection Settings window displays the Flow Rate, Count Rate, Aperture
Resistance, and Concentration settings that will alert the Multisizer 4 to an aperture blockage and
trigger the unblock procedure.
• Flow Rate. This field is available only in volumetric mode. A low flow rate or a significant change
in flow rate can indicate aperture blockage. A high flow rate can result from air passing through
the aperture, indicating that the sample fluid level is too low.
• Count Rate. In general, the count rate will decrease if the aperture is blocked. With some small
aperture and particle combinations, however, the count rate can increase.
• Aperture Resistance. Unusually high electrical resistance can indicate blockage (when particles
trapped in the aperture act as an electrical insulator) or air in the aperture (when sample fluid
level is too low).
• Concentration. A brief spike in particle concentration indicates aperture blockage. If the
concentration returns to normal, it is possible that the blockage has cleared. You can set the
number of seconds for a momentary blockage If other parameters (flow, aperture resistance,
and/or count) indicate a blockage, however, you can assume that the aperture remains blocked.
In the expanded Blockage Detection Settings window:
1. If you are using 20-µm and 30-µm aperture tubes, click
(
Defaults
)
to set the defaults
automatically for the aperture size you are using. The default settings are:
• Automatic (from start of run)
• Cancel Unblock and Restart, Up to 4 times
• Use change from start of run, Flow rate: 35%
• Use change from start of run, Count rate: 40%