9600 Service Manual - gmecorp-usa.com

2 Generator Calibration
During the Duty Cycle the mA servo circuitry on the X-Ray Regulator PCB is
disabled by installing the E2 jumper. This insures that the hardware servo will have
no affect on tube mA. The kV servo circuitry remains enabled because the kV
characteristics of the X-ray tube are well documented and easy to reproduce.
When Duty Cycle starts the X-ray tube is in the 0.3 mm focal spot and is driven by a
narrow filament waveform at a constant 40 kV for the first exposure. The “Duty
Cycle” for this first shot is designated as 400. For the next exposure the filament
waveform is slightly wider while the kV remains at 40, which results in increased
tube mA. The “Duty Cycle” for this second shot is 425. For consecutive shots the
filament waveform width is increased slightly and the “Duty Cycle” designator
increased by 25. The kV is kept at a constant 40 kV until the tube mA is 45 mA or
greater. At this point the Duty Cycle switches to the 60 kV portion of the program.
If the Duty Cycle reaches 1225 before 45 mA is reached, the Duty Cycle will default
to the 60 kV portion of the program.
The tube is again driven by a narrow filament waveform, but kV is increased to 60
kV. The “Duty Cycle” for this first shot is again designated as 400. The filament
waveform width is increased for subsequent shots as described in the preceding
paragraph until the tube mA is 50 mA or greater. The Duty Cycle program then
switches to the 80 kV station where shots are taken in the same manner described
above.
This Duty Cycle process continues at 100 kV and 120 kV in the 0.3 mm focal spot
and then switches to the .6 mm large focal spot. Table 1 illustrates how the entire
Duty Cycle program functions from start to finish. Note that at each kV station the
“Duty Cycle Designator” starts at 400 and exposures are taken until an ending mA
value is reached. When the ending mA value is reached for a particular kV station
the program changes to the next kV station.
At the completion of the entire Duty Cycle program the system software processes
the data and calculates the H1, H2, and H3 coefficients. These coefficients are
used to compile mA/Duty Cycle curves for each focal spot of the X-ray tube. This
data will be used in the next step of the calibration process to produce exposures of
a specific kV and mA.
4. kV/mA Calibration - Calibration software automatically makes approximately 40
exposures at various techniques to determine the characteristics of the generator
electronics. This data is written to a file (CARM.CAL) for calculations after the
exposures have been completed. Calculations are made and correction vectors are
written to the EEPROM on the Technique Processor PCB.
During this step the mA servo circuitry is enabled by removing the E2 jumper on the
X-Ray Regulator PCB. Specific kV and mA exposures are taken during this step of
the calibration. The system software knows what duty cycle will produce the
approximate desired mA from the mA/Duty Cycle curves obtained earlier.