• Topic ID: id_11038867
  • Version: 3.0
  • Date: Apr 9, 2020 8:42:55 PM

HHS Scans

Prerequisites

The objective of this procedure is to validate HHS scans fit within specifications:

  • Attach oscilloscope to Inverter

  • Set up oscilloscope

  • Take each scan and record measurements

Procedure

  1. Remove gantry right side cover.
  2. Turn OFF all 3 switches (AXIAL DRIVE ENABLE, HVDC ENABLE, 120 VAC) on the Service Switch Panel.
  3. Remove and set aside the top and front gantry covers.
  4. Rotate the gantry such that HP inverter assembly is in the 2 o'clock position.
  5. Lock the gantry in position, using the rotational lock. Ensure that gantry rotation is locked by attempting to rotate the gantry by hand.
  6. Remove the large Inverter covers.
  7. Attach a protective ESD wrist strap and use while making connections to the HP inverter test points in the next step.
  8. Setup the oscilloscope for your first scan
    1. To minimize noise and obtain a common ground, you should plug the oscilloscope into either the gantry or the console. If you do not, this test won't work.
    2. Connect channel one probe to KV_N (TP6) and ground to KV_GND (TP8).
    3. Connect channel two probe to MA_N (TP5) and ground to MA_GND (TP7).
    4. Set horizontal scale = 20 ms, vertical scale = 1V/div
    5. Trigger channel one, negative slope, DC couple, trigger mode normal.
  9. Launch the KV MA TOOL.
  10. Begin scans sequence. For all scans gantry rotation should be disabled. See the HHS data sheet for the list of scans you will need to take.
    1. Using cursors, record the mean value for mA between 4 and 6 seconds. Multiply this value by Record this value in the mA @ 5mS column on the HHS scans data sheet.
    2. Using cursors, record the mean value for kV between 10-20 seconds. Record this value in the kV column on the HHS data sheet.
    3. Record the time and the mA value listed in the corresponding column on the HHS scans data sheet for each scan.
    4. Record the actual kV value at the bleeder.
    5. Continue for all scans. You will need to adjust the vertical scale accordingly on the scope as the scan kV increases.
    6. Record all results on the HHS Scans Data Sheet. You will need to print these sheets.

Finalization

  1. Ensure all measurements are within the specified limits. If any one scan is out of specification limits, take the appropriate service action.