Statistical Stability (Stat) Test
If gauge readings are suspect, perform a stat test as follows. (See
the example on the next page.)
1. Turn the gauge on and allow it to warm up for fifteen to
twenty minutes.
2. Place the gauge on the reference block in the standard count
or SAFE position.
3. Recording all counts, take twenty one-minute readings.
4. Compute the standard deviation (s) and the average (x) of
the moisture and density readings using the following
formulas:
5. Divide the standard deviation of the moisture readings by
the square root of the average moisture reading. If this ratio
is not within the range of 0.17 to 0.33, check or replace the
moisture model and/or high voltage module. If the gauge is
still unstable, replace the He
3
tube. If the gauge is unstable
after replacing the moisture module, high voltage module,
and
3
He tube, contact your Troxler service department.
6. Divide the standard deviation of the density readings by the
average density reading. If this ratio is not within the range
of 0.17 to 0.33, check or replace the density module and/or
high voltage module. If the gauge is still unstable, replace the
G-M tubes. If the gauge is unstable after replacing the
density module, high voltage module, and G-M tube, contact
your Troxler service department.
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