Section 3 - Installation
3-19
VAC.
If the voltage is out of this range, recheck the voltage at the wall outlet, and the
strapping of the isolation transformer as shown Figure 3-16.
CHECK TUBE KV PEAK POTENTIAL
Proper operation of the QDR 4500 requires that the X-ray tube generate X-ray pulses of 80kVp,
100kVp 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, a 10,000 to 1 voltage divider circuit is
utilized 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 barrier strip on top of the X-ray source.
WARNING:
Even though the test voltage is low, there are elevated voltages near and around the
test points.
1.
Remove the tank cover (2 Phillips screws). For QDR 4500A and QDR 4500SL systems,
raise the table to its upper limit for better access to the tank.
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 and 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.
From the m
ain menu, press <Alt> <F1> to exit to DOS and type
SUSQ
<Enter> to run
the survey program.
5.
Change the X-ray Mode to 4 and Aperture to 3.
6.
Press <F1> to turn on the X-rays.
7.
Observe the oscilloscope. You should see a trace similar to Figure 3-17, approximately
4ms pulses with a peak amplitude of 8V (ignore the overshoot, measure after it settles
out). This corresponds to 80kVp inside the tank.
8.
Press <F2> to turn off X-rays.
9.
Change the X-ray Mode to 3.
To Next Page
Loading...
