Discovery QDR Series Technical Manual
3-28
6.
Move the C-arm until it is parallel to the tank using the digital level to measure
the angles.
3.4 Calibrate and Test the System
3.4.1 Check Tube kV Peak Potential
Proper operation of the Discovery requires that the X-ray tube generate X-ray pulses of
80kVp, 100kVp, 120kVp, and 140kVp, all ± 10%. The peak potential check must be
performed at installation time and whenever the X-ray source or X-ray controller is
repaired or replaced. Because it would be very dangerous to directly monitor the kVp
potentials, there is a 10,000 to 1 voltage divider circuit inside the High Voltage Power
Supply/Source (HVPS/S). By monitoring this divided voltage, one can determine the peak
potentials being impressed on the X-ray Tube. The monitoring can be done on the terminal
strip on top of the X-ray Source.
1. Remove the tank cover (2 Phillips screws).
Set up the scope as follows:
Channel 1:2V/div (0.2V/div if using x10 probes)
Channel 2:2V/div (0.2V/div if using x10 probes)
Time base:5.0ms/div
Trigger on line (positive slope)
Set Vertical Mode to Add
Invert Channel 2.
Connect Channel 1 to TB1-PIN 12 (on the tank)
Connect Channel 2 to TB1-PIN 11 (on the tank)
2. Ground both channels and move the trace to the bottom of the screen. Remove
the grounds and go to DC coupling.
3. Instrument power, computer power, and the X-ray enable key should all be on.
4. Start the X-Ray Survey Utility by selecting Utilities|Service Utilities|X-Ray
Survey (see “X-Ray Survey” on page 9-1 for information on the utility).
5. Change X-Ray Mode to 4 and Aperture to 7. (Note: On Ci and Wi systems, the
Aperture parameter is set to a default value of -1 by the system software. Do not
change this value on Ci and Wi systems.)
6. Click X-Rays (F2) to turn X-Rays on.
7. Observe the oscilloscope. You should see a trace similar to Figure 3-17, approxi-
mately 4ms pulses with a peak amplitude of 8V (ignore the overshoot, measure
after it settles out). This corresponds to 80kVp inside the tank.
WARNING:
X-rays are generated during this procedure. Keep hands, head and other body parts out
of beam.
WARNING:
Although the test voltage is low, there are elevated voltages near and around the test
points.
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