Fluke Biomedical 35080B - Manual (Page 52)

35080B
Operators Manual
10-4
Each 1% deviation of this value will result in
no more than a 0.75% of reading error.
This measurement must be made with a ±
0.1% DVM.
EXTERNAL CALIBRATION CHECK
1. Place the Model 35080B kVp Divider in the “RUN” mode. Insert the Test Pack (32863).
2. Place the kVp divider in the x-ray beam aligned as described in Section 4.5, Geometry of Setup.
Make the focal spot to kVp divider distance 22 inches.
3. With a 100 kV, 200 mA exposure, the output should be 3 volts ± 1%.
Most oscilloscopes are not accurate enough (0.1%)
to make this measurement. Each 1% of miss-
adjustment will cause a maximum of 0.75% of
reading error.
CALIBRATION ADJUSTMENT
Only facilities with precision calibration equipment
should adjust the calibration of the Model 35080B
kVp Divider.
1. Insert the Test Pack (32863). Place the Model 35080B kVp Divider on the x-ray table, such that the
distance from the focal spot to the kVp divider is 22 inches, and the instrument is normal to the
beam--with the long axis of the kVp divider perpendicular to the axis of the x-ray tube; this
configuration will avoid “heel effect.” Settings on the generator for kVp should be 100 kV and 200
mA.
2. With the kVp divider in the “OFF” mode, zero the oscilloscope.
3. Turn the mode switch on the kVp divider to the “RUN” position.
4. Make an x-ray exposure (greater than 1 mS duration for three-phase generating equipment--greater
than 1 line cycle duration for single-phase generating equipment).
5. Accurately measure the peak voltage (± 0.1%). Record this value as “A”.
6. If “A” falls outside of the range 2.970 to 3.030 volts, adjust the kVp divider, as follows.
7. Remove the kVp divider instrument case to access the adjustment potentiometers. Place the kVp
divider in the “CAL” mode and measure the output voltage (± 0.1% accuracy). Record this value as
“B”.
8. With the kVp divider still in the “CAL” mode, adjust RP102 until the output is
V = 3.000 x B/A volts.
9. With the instrument still in “CAL”, adjust RP101 until the output = 0.750 volts.
10. Place the kVp divider back in its instrument case and turn the function switch to the “RUN” mode.
Repeat Step 5. The value should be 3.00 volts ± 1%. If not, repeat the sequence.
NOTE
NOTE
NOTE