IRadimed MRidium 3860, Service Manual

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4-6
rate. During each pump cycle ( one rotation ), encoder pulses are
accumulated and timed. Timing is not held steady for each given flow
rate, but rather ‘modulated’ through a series of various speeds which
linearize the inherent non-linearity of peristaltic pumping mechanisms
and produce a uniform rate of fluid flow throughout each pumping
cycle. The start position and duration of each of these linearizing
speeds is held in flash memory of motor controller U6. This position is
found during factory calibration with the pump connected to a high
accuracy calibrated scale while the delivery profile at 1 ml/Hr is studied
by internal calibration software. Anytime the mechanical alignment of
the encoder wheel relative to the pumping finger position is changed or
suspect ( pump block or motor replaced ), this calibration process must
be performed.
The sequential extension and retraction of the pumping fingers from
top to bottom results in a downward moving compression zone within
the administration set's pumping segment (see Figure 4-3) creates
positive pressure on the outlet side (distal end) of the tubing set.
Resilience of the silicone pumping segment tube causes it to return to
its cylindrical shape as each of the pumping fingers recede from the
extended position. This reshaping creates a vacuum in the proximal
tubing and draws fluid from the IV solution container to refill the tubing.
This peristaltic-like action along with the modulation of speed each
results in a smooth, controlled flow of IV solution from the fluid source
to the patient.
4.3 Electronic Operation
Electronic functionality and inter-relationships are discussed below. Utilize the
block diagram of Figure 4-1 along with the schematics for the various PCB’s
discussed for a complete view of the electronic operation.
4.3.1 Electronics Functional Description
The MRidium 3860+ MR IV pump’s electronics are micro processor
based. There are two processors working together to accomplish this
control and to check one another. providing a high degree of system
safety and control.
The master processor is a Zilog eZ80 type (U3) with on board 8KB
RAM, 128KB Flash, two serial UART’s, SPI, and I2C communications
along with Real time clock and general purpose I/O. In addition to these
on board resources there is an external 128KB of battery backed RAM
and 512KB of flash for extended program storage as well as 12 bit A/D
for gathering analog signal data. The RAM is used to store over 5000
operations history records for serial download from within the service
mode. Operating at 22MHz, the eZ80 communicates with the motor
control processor and rear panel Data Flash memory socket via the SPI
and with the smart battery gas gauge vi the I2C port. The UART
communications are routed to the rear panel RS232 I/O port and the
internal 2.4GHz remote control radio sub-system (optional equipment).
The second processor is considered the ‘motor control’ processor and is
an 8051 type operating at 12MHz, shown as U6 on the IVPAB002
schematic. Communication with the master is via the SPI serial buss. It
outputs a motor run command to the custom analog IC, AB001-U2, to
cause the motor to turn. Each processor receives and counts encoder