The normal functions of the dose calibrator are dis-
abled as the background is compensated for. This proce-
dure will take anywhere from several seconds to 100 sec-
onds, depending upon the level of activity of previous meas-
urements. You may abort the background measurement at
any point by simply pressing the BKGND key a second time.
After the above background correction has been completed,
remove your Cs-137 calibration Check Source from its
shield, place it in the Sample Holder and lower it into the
Chamber Well. Press the Cs-137 Isotope Selection key on
the front panel and observe that the LED on the key comes
on. The Activity Display will now indicate the activity of your
Cs-137 Check Source. Compare it to the decayed calibrat-
ed activity (see Appendix C for Decayed Activity Chart,
Chapter 5 for an explanation). For a properly calibrated
source above 200 µCi, the displayed value should be within
a few percent of the decayed calibrated value. If you do not
have a Cs-137 source, use a calibrated vial Co-57 source
and repeat the above by pressing the Co-57 key.
These calibration check sources provide a vital quality
assurance test which should be done daily to assure proper
performance of the calibrator.
AVERAGING PERIOD
The Atomlab 100 automatically selects the proper averaging
period or time constant for the proper display of low activity
sources. When you first lower the source into the well, the
activity value quickly jumps to the final value. For a few sec-
onds the value may fluctuate, but then the value settles
down to a small variation in the right digit. The Atomlab
Dose Calibrator will average the activity data while the
source is in the Chamber Well, which over several seconds
will result in a stable reading. As soon as the source is
removed from the Chamber Well, the Activity Display will
drop down to the near zero value.
ATOMLAB Dose Calibrator Operation Manual Chapter 3
Biodex Medical Systems 3-4 Release 2.0
Cs-137 Check
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