h. Set the proper kVp.
Seventy kVp on a three-phase machine.
Eighty kVp on a single-phase machine.
i. Use a lead number to mark the unleaded section of the cassette with the
appropriate mA and time.
j. Make the exposure.
k. Rearrange the lead blocker.
Cover the exposed area.
Uncover another fourth of the cassette.
l. Repeat steps h through k until four exposures have been made.
Each exposure will have a different mA and time, but will produce the same
4-10. EVALUATION AND INTERPRETATION
a. Place the processed film on the illuminator.
b. Use the timer protractor to measure the angle of darkened area of the moving
An extra impulse of a low brightness level is permitted at the beginning arc.
This is caused by a step-start effect of premagnetizing.
c. Compare the four different step wedges.
Use the same kVp and mAs on all four exposures.
The density should be the same on all four step wedges.
d. Use the densitometer to check the densities of the step wedges.
If the timer proves to be accurate, and the four exposures have different
amounts of density, consider the milliamperage (mA) inaccurate.