GE Brivo OEC 865 - Page 118

Brivo OEC 715/785/865/865 Mobile C-Arm X-Ray Product Service Manual
2-64
Mother Board
Collimator
MCB
CCB
SPI
Command
Position
Drive
Position
Ref voltage
There is an independent control loop working for each motion. The negative feedback control loop is used.
E.g. for iris control, the following steps will be operated:
a) Firmware in MCB sends a command to CCB by SPI bus to tell the required position of iris.
b) CCB receives the command and compares it with the feedback position signal coming from the
Collimator. A PI operation is performed and works out the control signal. The signal is converted to drive
voltage by a power amplifier and sends to collimator.
c) The drive voltage drives iris motor moving and the position feedback will be closer to command. So the
difference between command and feedback will reduce. The drive voltage returns almost zero while the
feedback is very close to the command. The control loop is finished.
Collimator control subsystem works in following situations.
a) Move the iris and shutter to default position for each Mag mode. The default position is sent to
Collimator Control Board in one command.
b) Move the iris and shutter to default position for film mode and return to last position while recovering
from the film mode. The default or last positions is sent to CCB in one command.
c) Follow the operation of collimator from control panel. And the initial collimator position in each Mag is
the calculated result in collimator calibration recorded by system.
Image Intensifier
Key parameters of Image Intensifier for Brivo715/785:
For PN 5075001:
Parameters
Operating Mode
Unit
Normal(9”)
Magn.1(6”)
Magn.2(4.5”)
Useful entrance field size 215 160 120 mm
Output image diameter 20.2 mm
Center Limiting resolution 44 50 54 lp/cm
DQE at 59.5 keV- absolute (IEC) 58 / / %
For PN 5085917: