CELL-DYN
®
3200 System Operator’s Manual
3-3
9140181H—October 2001
Section 3
Principles of Operation
Sample Analysis Cycle Overview
NOTE:
Sample and reagent volumes given in this section are stated as the
nominal values. Slight differences between instruments may cause these
volumes to vary. These differences are compensated for by factory-set
internal dilution factors.
Sample Aspiration
A sample is aspirated either in Open Mode or Closed Mode and transferred to the
Shear Valve. The sample volume in Open Mode is 150 µL. The sample volume in
Closed Mode is 240 µL.
Sample Segments
The Shear Valve rotates in order to separate three volumes of the aspirated whole
blood sample. The three volumes are:
20 µL for the WBC dilution
1.67 µL for the RBC/PLT dilution
12 µL for the HGB dilution
RBC/PLT Analysis
1. The Diluent/Sheath Syringe dispenses 2.79 mL of diluent through the Shear
Valve where the 1.67 µL RBC/PLT volume is transferred to the RBC Mixing
Chamber.
2. The segment and diluent are then routed to the RBC/PLT Mixing Chamber
where the dilution is swirl mixed. The final dilution is 1:1675.
3. The Sample Transfer Pump transfers the RBC/PLT dilution from the RBC/
PLT Mixing Chamber to the Optical Flow Cell Sample Feed Nozzle.
4. Diluent/Sheath reagent, under constant pressure in the Sheath Reservoir, is
directed into the Optical Flow Cell.
5. Sequentially, the Sample Metering Syringe injects 24 µL of the RBC/PLT
dilution into the flow cell at a pressure (and speed) lower than that of the
diluent/sheath reagent.
6. The higher speed of the sheath, which surrounds the RBC/PLT dilution, and
the special geometry of the flow cell combine to focus the RBC/PLT dilution
stream so that individual cells can be counted.
7. A laser beam is focused on the flow cell. As the sample stream intersects the
laser beam, the light scattered is measured at 0°, 10°, and 90° for red blood
cells, and at 0°and 10° for platelets.
