Fluke Biomedical 8000 Victoreen - Manual (Page 55)

Operation
Modes of Operation
2
2-43
2.5.8 Cal Mode
CAL CT n.nn E
±nn Rcm/nC
HVL SCATTER n.nn E
±nn Gy/nC
EXP MAMMO n.nn E
±nn
R/nC
CT EXP FLUORO n.nn E
±nn
R/nC
AMSE R/F n.nn E
±nn
R/nC
FLUORO INTERN n.nn
E
±nn CF
MODE CHAMBER VALUE EXPONENT R/Gy
The Cal mode is used to enter and store calibration factors for ion chambers used with the NERO mAx.
Calibration factors are available for the NERO mAx’s internal chamber and external chambers, including
the Victoreen CT chamber. These calibration factors are used in all exposure and rate measurements
made with the NERO mAx. Below is a list of external ion chambers that are supported by the NERO
mAx.
Ion Chamber Part Number Nominal Volume
CT 6000-100 3.2 cc
CT 6000-200 10 cc
Scatter 6000-532B 400 cc
Mammo 6000-529 3.3 cc
Fluoro 6000-530B 105 cc
R/F 6000-528 30 cc
Calibration factors for all external chambers (except the CT chamber) may be entered in units of R/nC or
Gy/nC. The calibration factor for the CT chamber must be entered as Rcm/nC. The calibration factor for
the NERO mAx detector’s internal ion chamber is a multiplier. All ion chamber calibration factors are
stored in nonvolatile memory.
To change an ion chamber calibration factor
Using the mode key, select CAL mode. Then, using the CHAMBER softkey, select the ion chamber
calibration factor to be changed (R/F, mammo, fluoro, etc.). A highlight (reverse video) will extend across
the remaining 3 fields for the selected chamber. Depress the button beneath the segment of the
calibration factor that is to be changed (value, exponent, R/Gy) and use the up and down arrow keys to
increment and decrement the selected number. Holding down the up or down arrow keys continuously
increments or decrements the selected number. The values of the calibration factors (mantissas) are
limited to numbers between 1.00 and 9.99. The exponents for all ion chambers calibration factors, except
for the internal chamber, are limited to ± 10. The exponent for the NERO mAx detector’s internal ion
chamber’s correction factor is limited to ± 1. The R/Gy key toggles the calibration factor units between
R/nC and Gy/nC for external ion chambers only.
The NERO mAx’s internal ion chamber is factory calibrated to provide accurate exposure and rate
measurements over the entire kVp range of the NERO mAx. These exposure and rate measurements
are adjusted by applying energy dependent correction factors that are determined by comparison to
applicable N.I.S.T. techniques. A calibration factor for the internal ion chamber is provided which allows
the user to make adjustments in this chamber’s calibration. The calibration factor for the NERO mAx’s
internal ion chamber is a unitless correction factor or multiplier. This calibration factor is used whenever
exposure or rate measurements are made with the NERO mAx’s internal ion chamber. This calibration
factor does not alter the ion chamber’s factory calibration but is used in conjunction with the factory
calibration (along with air density correction) to calculate exposure and rate. The default for this
calibration factor is 1.00 E+00. For more information about entry of air density information (temperature
and pressure), see SETUP mode.