Fluidic System
1 2
Front
bath
Aerial dust
filter
Negative Pressure
chamber
Metering
tube
Back
bath
Aperture
Figure2-4 Counting module
The counting module is implements the most important function of the analyzer -
counting. The electrodes installed on the bath detect the pulses caused by blood
cells passing the aperture. The detected pulses are then sent to the analog
board to be amplified, rectified, recognized, adjusted and counted.
When the sample is mixed in the bath, valve 2 is open and the negative pressure
chamber introduces the atmospheric air to pass through the filter and valve 2 and
then to flush the metering tube. Valve 1 is open when the vacuum has been
established and the sample (blood cells) in the bath is drawn through the
aperture by the negative pressure to generate the counting pulses. The sample
keeps moving to push the rinse between the back bath and metering tube to
move through the tube. When the rinse passes the upper optical sensor mounted
on the metering tube, a start signal is generated and sent to the analog board,
which starts the counting right away, and when the rinse passes the lower optical
sensor, a stop signal is generated and sent to the analog board, which stops the
counting right away.
Volumetric metering：the volumetric metering ensures a relatively objective and
stable analysis cycle.
Monitoring of the counting time：the volumetric metering enables the monitoring
of the counting time. By monitoring the counting time, the system can easily
know whether the aperture is clean or blocked and feed this information to the
service personnel in terms of the aperture voltage so that they can service the
2-6 BC-2800 Auto Hematology Analyzer (V1.0)
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