Function And Safety Checks; Aec Functional Check - Canon OMNERA 500A Operator's Manual

7 Function And Safety Checks

7.1 AEC Functional Check

The following procedure may be used to verify that the AEC circuits are functioning on
generators equipped with AEC (automatic exposure control).
1. Switch the generator ON, and select an appropriate radiographic image
receptor.
2. Align the X-ray tube and the selected image receptor such that the central ray is directly
over the center field of the AEC pickup device. Set the focal spot to film plane distance to
40 in. (1 m).
3. Select AEC mode of operation. Select center field, large focus.
MINIMUM EXPOSURE TIME:
4. With no object in the radiation field, adjust the collimator or beam limiting device to
project a 10 in. X 10 in. (24 cm X 24 cm) field at the image receptor.
5. Select 80 kVp, 100 mA, and a backup mAs of 50 if it is operator selectable. If this is not
operator selectable, the default AEC backup settings must be used. Refer to the note at
the end of this page to determine the AEC backup mode that has been programmed.
6. Make an exposure and verify that the POST mAs reading is 2 mAs.
MAXIMUM EXPOSURE TIME:
7. Close the collimator or beam limiting device completely. Place a folded lead apron over
the image receptor.
8. Select 60 kVp, 100 mA, and a backup mAs of 50 if it is operator selectable. If this is not
operator selectable, the default backup settings must be used. Refer to the note at the
end of this page to determine the AEC backup mode that has been programmed.
9. Make an exposure and verify that the AEC backup timer has terminated the exposure.
Note!
The AEC backup mode is installer programmable. Three modes are available, FIXED, MAS,
and MS. Only the MAS mode allows the operator to set the backup mAs for an AEC
exposure.
FIXED: The generator will determine the maximum AEC backup time, not to exceed pre-set
AEC backup mAs/ms values or system limits. The characters AEC will be displayed in the
time window of the LED display during AEC operation.
MAS: Allows the operator to adjust the AEC backup mAs, not to exceed preset AEC backup
mAs/ms values or system limits. The mAs value will be displayed in the time window of the
LED display during AEC operation.
MS: Allows the operator to adjust the AEC backup ms, not to exceed preset AEC backup
mAs/ms values or system limits. The ms value will be displayed in the time window of the
LED display during AEC operation.
Operator´s Manual
Function And Safety Checks
1000-095-071-EN Rev. 2.1
Page 139
AEC Functional Check
OMNERA 500A