Press STD and LOCK simultaneously on the keyboard
and the tester will now clear all four memories, and will
count a 4 minute count into all four memories. The 4
minute count will be normalized to a 1/4 minute common
Record the final average of either method on the daily
field work sheet. The 4 minute automatic standard count
will be retained in memory until erased by the next STD
or by the taking of a TEST count.
Periodically, the tester should be checked for good
statistical operation. This is the ONLY way the operator
Place the source rod in SAFE position and be
can verify that his tester is operating correctly. Using this
sure the tester is at least five feet from nearby
technique, it is possible to predict a future failure before it
is severe enough to cause field errors or complete
This periodic evaluation should be
Stand the shipping case on end and place the reference
performed at least once a month or whenever the tester
standard across the protective strips on the case Three
has not been used for several months.
buttons on the
accommodating depressions in the bottom of the tester.
All nuclear method testers will vary in count rate from
See Fig. 1-2.
one undisturbed count to another due to the random
nature of the radioactive source decay.
At this point two counting methods may be used:
This is a very reliable random rate in that it faithfully
Manual, with successive counts.
obeys the laws of statistics relative to random sources of
"population'...where population = count rate for nuclear
Automatic, with four minute averaging.
The Manual method is used for periodic tester evaluation
Any series of numbers taken among a varying
population of events will exhibit a form of
The Automatic method is used for routine daily standard
count accumulation into the tester Standard Count
A series of nuclear tester counts, taken with
the tester in an undisturbed position between
all counts, will also exhibit a standard deviation
around the average of the counts or mean.
Successively accumulate 10 1/4 minute counts.
It is true that if the source of a series of events
is truly random, then the standard deviation of
Do NOT use other time periods for purposes of