Medrad ProVis Mark V, Руководство по обслуживанию

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Injector Head
13 - 5
Turret Sensing
Circuit The Turret Sensing circuit detects if the turret is in position for an
injection or loading without the use of mechanical limit switches.
Turret Detection:
When the turret is in position, +26 volts follows a series path from the
Injector Head to the PDCI and SCC. When the turret is in position,
+26 volts is switched through transistor Q7. Q7 is enabled by either
U8E/D8 or U4C/D9, depending upon turret position. Next, the voltage
is sent through the normally open contacts of the Mechanical Stop
Limit switch; then, to energize Safe Relay K1 (PDCI) and U16 (PIO 3
on the SCC), alerting the system that the injector head is ready for
injection. To determine if the turret is in position, an optical sensing cir-
cuit is used. Two optical sensors, mounted on a PC Card in the Injec-
tor Head, are set-up as “active high”, meaning that the transistor
portion of the sensor is ON (or active), when infrared light passes from
the LED to the base of the transistor. The slotted drum, mounted on
the turret shaft, rotates with the turret, and permits activation of the
sensor that corresponds to turret position.
Mechanical Stop
Position / Arm Light
Enable Circuit This circuit provides a visual indication that the Mechanical Stop is in
position, and that the injector is armed. When the injector is armed,
the software sends a position command to the Mechanical Stop DAC,
producing an analog command voltage for the MSD Card, which
drives the Mechanical Stop motor. Mechanical Stop position is tracked
by the Mechanical Stop Position Feedback Potentiometer. When the
position feedback voltage indicates that the Mechanical Stop is cor-
rectly positioned (through software comparison with the Mechanical
Stop Position Command), the system sends an ARMED indication
through the I/O and MSD cards, which lights the Mechanical Stop Set
LED, and makes the Arm Light Bar flash.
Mechanical Stop in Position:
In standby, the non-inverting input of U1A is +5 volts (charging of C8
through R14), and inverting input is +3.4 volts (voltage divider R21/
R26), making the output of U1A positive saturation. When the injector
is armed, and the system has determined that the Mechanical Stop is
correctly positioned, ARMLTDR alternates low then high, momentarily
discharging C8 through D1, dropping the non-inverting input to zero.
Positive 3.4 volts on the inverting input causes the output to go to
zero, which makes Q1 conduct, supplying ground to light Mechanical
Stop Set LED DS1. The narrow width of the ARMLTDR pulses, cou-
pled with the large value of R14, prevents C8 from charging, keeping
output of U1A at zero, and the LED lit continuously until the injector is
disarmed.