Discovery QDR Series Technical Manual
3-30
3.4.2 Check Tube Current
Follow the procedure below to check X-ray tube current. Monitoring tube current is done
on the barrier strip on top of the X-ray source.
1. If the tank cover is not off, remove it (2 Phillips screws).
2. 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 10 (on the tank)
Connect Channel 2 to TB1-PIN 7 (on the tank)
3. Ground both channels and move the trace to the bottom of the screen. Remove
the grounds and go to DC Coupling.
4. Instrument power, computer power, and the X-ray enable key should all be on.
5. 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).
6. Change X-ray Mode to1 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.)
7. Click X-Rays (F2) to turn X-Rays on.
8. Observe the oscilloscope. You should see a trace similar to Figure 3-19, approxi-
mately 4ms pulses with a peak amplitude of 3V (ignore the overshoot and mea-
sure current on the back, after it settles out). This corresponds to 3ma ± 35% tube
current.
9. Click X-Rays (F2) to turn X-Rays off..
Note: Enter this information into the Radiation Measurement Report (see
example on page 3-70).
10. Change X-ray Mode to 3.
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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