Fluke Biomedical 35080M - Manual (Page 16)

Operation
Filtration Effect Corrections
2
2-5
2.6 Filtration Effect Corrections
Corrections for filtration are made with the correction curves in Figure 2-4. Factory calibration of the
Model 35080M kVp Divider is performed with 2.5 mm Al total filtration, so any other amount of filtration in
the beam which is greater than or less than 2.5 mm Al will require some correction of the apparent
reading.
Example: Suppose the kVp Divider reads 90 kV, using the Wide Range Filter Pack (37617). The X-ray
machine has 5.0 mm Al total filtration. The filtration effect curve for this filter pack indicates a filtration
effect of 0.5 kV per mm Al at 90 kVp. To determine the actual reading, the filtration in the X-ray machine
is subtracted from the standard calibration filtration (2.5 mm Al) and the resulting number is multiplied by
the filtration effect: (2.5-5.0) x 0.5 = -1.25 kV. The resulting number, -1.25 kV, is the correction which is
added to the apparent reading. Therefore, the actual reading is 90 kV + (-1.25 kV) = 88.75 kV.
Figure 2-4. The Wide Range Filter Pack (37617) Filtration Effect Correction Curve
Filtration
Effect
kVp Per mm
Model 35080M Reading