P/N 9-500-0255 4-29
Service Manual
Chapter 4: Calibrations and Performance Checks
Automatic Exposure Control System Calibration
17. Insert a loaded cassette into the Bucky, then make a 25 kV Auto-Time exposure. Record
the mAs value (as point “A”) on the semi log worksheet (Table 4-12).
18. Release compression and place the amount of BR-12 or PMMA acrylic that was used in
the final 25 kV, high attenuation exposure from Table 4-6 on the Bucky. Reapply com-
pression, then make a second exposure. Record this mAs value (as point “B”) on the
semi log worksheet.
19. Draw a line between points “A” and “B” on the semi log. Follow the left side of the graph
and locate the 80 mAs point. Draw a straight line and intercept the line between the 2
points.
20. Draw a vertical line from that point to the bottom of the graph and note the compression
thickness value indicated. This is the compression thickness threshold value.
21. On Calibration Screen 3, highlight HTC C-THK and change the displayed value to the
value calculated on the graph.
To Next Page
Loading...