Hologic QDR 4500 - Check Tube Current

Section 3 - Installation
3-21
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.
WARNING:
Even though the test voltage is low, there are elevated voltages near and around the
test points.
1. If the tank cover is not off, remove it (2 Phillips screws). For QDR 4500A and QDR
4500SL systems, raise the table to its upper limit for better access to the tank.
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 and 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. From the main menu, press <Alt> <F1> to exit to DOS and type
SUSQ
<Enter> to run
the survey program.
6. Change the X-ray Mode to 1 and Aperture to 3.
7. Press <F1> to turn on the X-rays.
8. Observe the oscilloscope. You should see a trace similar to Figure 3-19, approximately
4ms pulses with a peak amplitude of 3v (ignore the overshoot and measure current on
the back, after it settles out). This corresponds to 3ma
±
35% tube current.
9. Press <F2> to turn off X-rays.
Note:
Enter this information into
The Radiation Measurement Report
(see page 3-28).
10. Change the X-ray Mode to 3.