Medrad ProVis Mark V, Service Manual

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Mark V ProVis Injection System
7 - 2
PIO3 include: Flow Control signals, the Safe Relay Enable, and the
System Override signal.
System Monitor
Flip-Flop The flip-flop (U17) sends alarm signals to disarm the injector, if any of
the following input conditions occur: WATCHDOG 2, OPLIM (over-
pressure signal), or AUX MONITOR (power drive failure).
Command, Position,
and Signal DACs When enabled and timed by the DAC decoder U14, one of the DACs
(U21-U24) will read a byte of data bus information. The DAC then
converts the byte to an analog voltage between zero and 10 VDC.
DAC resolution is 40mV per count.
Pressure Limit Command DAC
The output of this DAC is the Pressure Limit Command signal
(PSILIM SELECTED). This signal is sent to the Multiplexer, the Pri-
mary Pressure Limit circuit, and the Overpressure Limit circuit.
Flow Rate Command DAC
The output of this DAC is the Flow Rate Command signal (FLOW
RATE SELECTED). This signal is sent to the Multiplexer, Flow Scale
Circuit and Power Drive Card (PDCI).
Mechanical Stop Position DAC
The output of this DAC is the Mechanical Stop Position signal
(MSPOSCMD). This signal is sent to the Multiplexer, and through
Unity Gain Buffer U26C, to the Mechanical Stop Drive Card.
Velocity Signal DAC
The output of this DAC is a digitized velocity signal, sent to the Imag-
ing System Interface Card. This signal is buffered, becoming the Flow
Profile Signal available through J106.
Multiplexer (MUX) The multiplexer circuit is comprised of multiplexer U19, Quad latch
U20, and Unity-Gain buffer U26A. This circuit receives eight inputs,
and under timing control connects each input to the circuit output,
which is sent to the A/D converter.
TTL/CMOS Converter U25 converts TTL logic (0/5V) to CMOS logic (0/15V).
10V Reference Chip U28 de10 VDC as a reference voltage for the Plunger
and Mechanical Stop position feedback pots in the head. This voltage
is also applied to the multiplexer to be monitored by the CPU.
Pot Processor This circuit, comprised of U27C and associated components, buffers
and filters the pot wiper signal. The pot signal is an input to the multi-
plexer and the error amplifier.
Primary Pressure
Limit Circuit The Primary pressure limit circuit (U26B), compares the pressure limit
command to the actual pressure developed during an injection. The
output of this circuit is sent to three Pressure Limiting circuits to per-
form the following functions: