Del Medical EPEX Omniflex IV, Service Manual

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EPEX/Omniflex IV System Service Manual
4-44 Adjustments and Calibration
Precalibration Notes
This topic contains information that must be understood and confirmed
prior to and/or during AEC calibration.
The procedures in these topics require X-ray exposures. Take all safety precautions
to protect personnel from X-radiation.
Should an improper technique be selected, or an AEC fault occur causing
no AEC feedback signal to the Generator, the exposure will terminate if the
ramp voltage fails to reach 4% of the expected ramp voltage when the
exposure time reaches 20% of the selected Back Up Time (BUT).
• During calibration, all AEC exposures should be done using mA values
that result in exposures in the 50 to 150 ms range
unless stated
otherwise .
• During AEC calibration, always ensure that the central ray is centered
relative to the image receptor.
• Ensure that the Collimator is opened sufficiently to cover all fields on
the AEC pickup device.
• Ensure that the absorber is positioned to fully cover the X-ray field.
The absorber must extend a minimum of 3/8 in. (10 mm) beyond the
X-ray field.
• All components/assemblies used during AEC calibration must be those
which will be used during procedures, and must be positioned as they
will be in actual use of the X-ray room.
• The Generator must be calibrated before proceeding.
• During AEC calibration, if the exposure times do not change when the
mA is varied, it may be that the input signal level to the AEC board is
too high. If this happens, check the ramp voltage at the first gain stage
output (the first operational amplifier output) on the AEC board for the
specific AEC channel. This voltage must never exceed 10 V. If this
voltage
does exceed 10 V, reduce the input signal level as required.
CAUTION