IRadimed MRidium 3860, Service Manual

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system, checking the proper function of the motor
controller(s). Should the eZ80 find encoder ticks ( indicating
motor movement ) arriving at the wrong time or rate, the
motor controllers will be issued a stop command and the
motor kill line asserted, along with a critical error message
and alarm.
4.3.3.3 Motor Control Processor(s)
The motor controllers are Silicon Labs C8051F320 8 bit single
chip processors with internal clock oscillator and power on
reset circuits. These processors run entirely independent
from the master processor. Once the internal power good and
reset criteria are met, these processors initialize and prepare
to receive commands from the master processor.
The 8051’s receive time data indicative of the rate and
volume programmed by the user, as described above.
Internal program code issues motor run pulses to the US
motor driver circuit on the IVPAB001. Encoder pulses for
each .36 degrees of motor/pump rotation are accumulated
and timed. The algorithm keeps account of small deviations
between desired tick time and actual, extending or retarding
motor run pulses to overcome short term speed/flow errors.
However, should the encoder pulses accumulated indicate the
motor speed errors beyond preset limit thresholds, the pump
will stop and master processor issued a critical error code.
4.3.3.4 Audio Subsystem
The audio for alarm tones is generated by wave shape
filtering and power amplifying clocking signals from either the
eZ80 (U3) or U6. These tone clock signals are summed at
R37. U10 is a digital pot controlled by U6. This 50K digital
pot has 32 taps settable by front panel controls within the
MENU option. Its output is filtered by the poles of U11. U12
is a dual channel audio power amp in bridge tied load ( BTL )
configuration. Operating on the 10 volt supply and tied as
BTL, this amp can output 20 V P-P to drive two peizo speakers
for proper ( loud ) operation in high magnetic fields.
4.4 Air-In-Line Detector
The air-in-line detection system includes two piezo-electric crystals and a
signal processing circuit. The PE crystals and acoustic lenses are bonded into
recesses in the detector housing. The signal processing circuit is part of the
bubble detector printed circuit board mounted directly behind the detector
housing in a well cast into the chassis. Ultrasonic sensing is used for air-in-
line detection. Ultrasonic signal transmission (acoustic impedance) through
IV compatible solutions falls within a very discrete range which is easily
discernable from passage through air.
The air-in-line detector is located below the pumping mechanism and checks
the integrity of the fluid column entering the patient side (distal portion) of
the tubing set. The acoustic lenses and installed tubing set provide a coupling
path for the continuous wave ultrasonic transmission to travel from the
transmitting to the receiving crystal. When the tubing contains an IV solution,
the acoustic impedance is low and maximum energy is coupled to the