P/N 9-500-0255 4-13
Service Manual
Chapter 4: Calibrations and Performance Checks
Exposure System Calibration
13. Repeat steps 11 and 12 for each kV station using the Large focal spot and Mo filter, then
perform this procedure for each kV station using the Small focal spot, Mo filter and 12
mAs. Record the values for each kV station on Table 4-3.
Note… Three exposures are required to properly calibrate the mA at each kV
station.
14. Go to the Run Mode Screen and switch to the Rhodium filter then repeat steps 11 and 12
for kV stations 28 kV through 39 kV for both the Large (40 mAs) and the Small (12 mAs)
focal spots. After each exposure, check the waveform on the oscilloscope for under- or
overshoot (Figure 4-4). Verify that the waveform appears stable, and is at the correct
amplitude for the set kV as shown in Table 4-3.
15. Record the values for each kV station on Table 4-3.
16. For systems with HTC Buckys, perform reduced mA calibration below. Proceed to Step
17 if the system is not equipped with HTC Buckys.
a. Go to the Run Mode Screen and switch to the Mo filter.
b. Access the Calibration Screen #1, Auto Cal data field should read ON.
c. Highlight and change the appropriate data fields to set the unit for a MAN-
UAL mode exposure at 20 kV, 12 mAs, Large focus.
d. Highlight the Filament data field and then press Reset + Compression Up
together. (This will place you in reduced mA calibration mode.)
e. Install an HTC Bucky on the IRSD.
f. Step behind the radiation shield and make an exposure. (The system will
automatically adjust the starting filament values.) Wait 40 seconds, take a
second exposure. Wait 40 seconds, take a third exposure. After each expo-
sure, check the waveform on the oscilloscope for under- or overshoot (Fig-
ure 4-4). Verify that the waveform appears stable and is at the correct
amplitude for the set kV as shown in Table 4-3. Record the reduced mA for
each station on Table 4-4.
17. Highlight the Auto Cal data field and set to OFF.
18. For initial setup and calibration, skip this step and proceed directly to Section 4.4, Step
5. If all service procedures have been completed, remove the oscilloscope probe from
the test points. Set the unit back to the user mode (S2 switch 1 = OFF), then replace pre-
viously removed covers and panels.
To Next Page
Loading...