Fluke Biomedical 10100AT - Manual (Page 30)

10100AT
Operators Manual
2-12
Internal Calibration Check
To use the cal check feature of the Model 35080/80A/80B kVp Divider, set the Model 35050AT Dosimeter
for exposure rate units (A, R/s, etc.). Set the function selector of the Model 35080/80A/80B kVp Divider
to the CAL position. After the Model 35050AT Dosimeter's RESET/MEASURE button is pressed the filter
pack cal level will be displayed in kVp. The Linear Mammo Filter Pack cannot show the calibration check
kVp, since it falls outside the specified kVp range.
Because the Model 35050AT Dosimeter automatically performs filter pack linearization corrections when
the Wide Range, CT, or Mobile Filter Pack is selected, the kVp level displayed by the Model 35050AT
Dosimeter will differ from the calibration kV level printed on the face of the filter pack. Table 2-2 gives the
Printed Calibration kV Level for each filter pack as well as the Corrected kVp Reading that should be
displayed by the Model 35050AT Dosimeter.
Table 2-2. Corrected kVp Readings for kV Filter Packs with Automatic Linearization Corrections
Filter Pack Type 37617C Wide Range 3351C CT 37946C Mobile
Printed Calibration kV Level 80 kV 124.4 kV 100.0 kV
Corrected kVp Reading 79.4 kVp 123.6 kVp 98.8 kVp
Nominal Calibration Voltage 0.400 V 0.644 V 0.600 V
The Nominal Calibration Voltage levels listed in Table 2-2 are also printed on the faces of the filter packs,
and may be read directly and without the effect of the Model 35050AT Dosimeter's automatic linearization
correction scheme by selecting the Test Pack from the Model 35050AT Dosimter's Detector Select
screen.
Dosimeter Range Reduction in kVp Modes
Because of the higher exposure rates associated with kVp determinations, the dosimeter is automatically
desensitized when in either kVp mode. This changes the minimum detectable quantities as follows
below.
An important implication of the 5-picoampere threshold in the case of kVp/Exposure Rate is that there are
minimum radiological quantities that can be read, depending on the ion chamber being used. Once
above the threshold, though, there will be good value resolution.
Table 2-3. Reduced Range, Minimum Roentgen Readings
Ion Chamber Measurement Units Minimum Reading
15 cc R/s 1.2 m
R/min 72 m
R/hr 4.3
R/frame* 20
μ
150 cc R/s 120
μ
R/min 7.2 m
R/hr .43
R/frame* 2
μ
* at 60 frames/second