Quantum ODYSSEY HF Series, Service Manual

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Chapter 3 Calibration
HF Series X-ray Generators - Service Manual Revision W
Quantum Medical Imaging, LLC
3-51
AEC MAS Balance Verification
The generator AEC mAs balance was pre-calibrated at the factory. How-
ever, verification of AEC mAs balance assures AEC calibration accuracy.
When balanced, the mAs at the specified exposures will be approximately
the same (±6%). This procedure only needs to be performed once prior
to AEC calibration of the film/screen combination(s) used with the sys-
tem. Proceed as follows:
1. If not already done so, connect a kVp bleeder tank in series between
tube and High-Voltage (H.V.) Transformer A17. If using a mAs meter,
connect the mAs meter between pins A17P1-9 and A17P1-10 on H.V.
Transformer A17. This connection is made by removing the two
green/yellow wires connecting A17P1-9 and A17P1-10 to the ground
stud on top of the H.V. Transformer (see Figure 3-32) and connecting
the removed wires to the mAs meter. (Note: These wires must be re-
connected when finished calibration.)
2. Place 20 cm of acrylic in the X-ray beam. (Where practical, adjust
acrylic thickness to obtain approximately 100 millisecond exposures.)
3. If calibrating a" level" type ion chamber, ensure all three ion chamber
detectors are selected.
4. Press the AEC mode key on the operator control panel.
5. Set the operator control panel for 110 kVp (100 kVp if calibrating a
"level" type (Siemens) ion chamber - requires AY40-027S AEC
board), 75S mA and take an exposure.
6. On the Dynalyzer Digital Display or mAs meter, note the measured
mAs value.
7. Set the operator control panel for 110 kVp (100 kVp if calibrating a
"level" type (Siemens) ion chamber - requires AY40-027S AEC
board) and the highest available mA station. Take an exposure.
8. On the Dynalyzer Digital Display or mAs meter, note the measured
mAs value.
9. The mAs values noted must be within ±5%. If not, adjustment of
the dV/dt potentiometer on AEC Board A11 is necessary:
• If the generator is equipped with "standard" type AEC (i.e., AEC
Board A11 is part number AY40-031S), adjust potentiometer
A11R12 to increase or decrease the mAs value.
NOTE
To avoid
reciprocity
compensation,
the exposures
for mAs
balance
verification
ideally should
not exceed
100 ms.