Arena Service Manual
11.2.4 Motor Pump Assembly
This assembly consists of a DC stepper motor (connected to PF23
in the Blood Pump Power Board), a gear to drive the heparin pump
slide assembly gear rack, and one optical sensor for the heparin
pump overpressure alarm. This assembly is located behind the
Peripheral Interface Board. See Figures 11-2 and 11-3.
Figure 11-2. Heparin Pump Assembly
11.2.5 Syringe Overpressure Alarm
The heparin pump uses an end-of-stroke (overpressure) infrared
optical sensor that monitors the engagement of the rack and pinion
which is utilized for the overpressure alarm state. A pin located on
the motor mount is positioned between the LED and detector of the
optical sensor. This pin will normally occlude the light from the
LED into the detector when the gear rack and the motor gears are
properly engaged, or when no slide assembly is installed in the
Instrument. If this pin is displaced from the optical sensor, it
means the gear rack and motor gears have disengaged, pushing the
motor mount outward. This is an indication of an overpressure
condition and an overpressure alarm will occur within 15 minutes.
See Figure 11-3.
Figure 11-3. Heparin Pump Optical Sensors
11-6 157-1278-918 Rev A
April 2004
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