How
Do You Judge the Accuracy of a Leak Detector?
According to Six
Sigma* guidelines, there are four different parameters that determine
the quality of measurement equipment:
- Repeatability
- Reproducibility
- Linearity
- Stability
When applied to
leak detection, what do these four characteristics mean?
Repeatability
Repeatability indicates the degrees of variation
when measuring the same leak over and over again (by the same operator).
You can determine this by simply measuring the same calibrated test
leak several times under the same conditions. Repeatability is determined
by the maximum and minimum detected leak rates: the smaller the difference
between the two values, the better the repeatability.
Reproducibility
Similar to repeatability, reproducibility
considers the test results from different operators. To determine
the reproducibility of a leak detector, different operators measure
the same calibrated test leak several times. Again, the variation
of the different leak rate measurements gives you reproducibility;
the smaller the variations, the better the reproducibility of the
leak detector.
Linearity
Linearity in a leak detector shows the span
of measurement error over a large measurement range. This is especially
important when calibrating a leak detector with a leak rate value
different from the trigger value used. This is determined by calibrating
the leak detector with a small test leak and then testing this against
larger test leaks (factor 100 to 1000), or vice versa.
Stability
Stability indicates the reliability of test
results over time. To determine the stability of a leak detector,
set the leak detector with a calibrated leak. Now let the leak detector
run for many days, checking the leak rate reading in regular intervals;
the smaller the deviation after time, the better your leak detector.
INFICON rigorously
tests its leak detectors according to these four characteristics. We
will share the results of these tests with you in our next issue.
* Six Sigma
is a management strategy used to identify and remove the causes of
defects and errors in manufacturing and business processes.
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