Fluke Biomedical 6000-528 User Manual
Page 14
Victoreen 6000-528
Operators Manual
4-2
NOTE
7.
Compute the correction factor according to the following formula:
cf = TRUE/MEASURED
This correction factor should be recorded and used when making the Model 6000-528 External Ion
Chamber dose measurements. To use, simply enter into the NERO as the mR correction factor by
pressing "F mR". The display will then read directly in mR. Remember to return the correction factor back
to 1.000 when not using the Model 6000-528 External Ion Chamber.
4.2.2 Calibration with a 4000M+
1.
Calibration will be performed on a standard radiographic x-ray machine. Set the machine to 100
kVp, 300 mA, 0.5 sec. Place the Model 6000-528 External Ion Chamber on the table and use a
distance of 40 inches, Collimate so as to uniformly irradiate the entire ion chamber.
2.
Attach the Model 6000-528 External Ion Chamber to the Model 4000M+ detector by connecting the
BNC connector to the appropriate jack on the back, then plug the banana plug into its mating jack.
Position the Model 4000M+ such that no radiation will fall upon it.
The Model 4000M+ must be located out of the
radiation beam. The Model 6000-528 External Ion
Chamber is wired in parallel with the internal ion
chamber; therefore, any radiation falling on the
internal ion chamber will affect the reading. Shield if
necessary.
3.
To set up for an exposure, set the Radio/Fluoro switch to "Radio" and ALL/EXP to "EXP". The
Model 4000M+ will beep and display "0.0 mR", Make an exposure, and record the results. Press
"ROLL/RST" to clear the display and repeat. Make a total of five exposures in this manner. All five
should be within ± 3%. Compute an average and label it "Measured".
4.
Remove and disconnect the Model 6000-528 External Ion Chamber, and place the Model 4000M+
detector in the center of the beam. Raise the tube 2.25 inches to compensate for the height of the
detector box.
5.
Make five exposures using the Model 4000M+ detector in a similar manner as you did in step 3.
Again all give readings should be within 3%. Compute an average and label it "True".
6.
Compute the correction factor according to the following formula: cf = TRUE/MEASURED
This correction factor should be recorded and used when making the Model 6000-528 External Ion
Chamber dose measurements. To use, simply multiply the exposure or exposure rate readings by cf, or if
you are using DXS, cf may be entered as the exposure correction factor.
4.2.3 Determining Calibration Factor (cf) for Factory Calibrated Chambers
The following can be performed to determine the calibration factor:
1.
Obtain the calibration results of your Model 6000-528 ion chamber, reported as R/nC. (Fluke
Biomedical can supply this if needed).
2.
Locate "Charge Calibration" on the 6000 or 4000 series calibration sheet reported as nc/R.
3.
Multiply the two numbers together to obtain cf.
4.2.4 Calibration with a Model 6000-530 Preamplifier