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Atrato_Instruction_Manual_0322
®
4.5.2. Median Filter
This filter removes short term anomalies in the
recorded flow, e.g. caused by an air
bubble passing through the meter. It should be used with caution as it is theoretically
possible that overuse of this feature could lead to incorrect results in certain
circumstances. Under normal operating conditions the meter returns around 25
results per second and a regular occurrence at this frequency could be completely
ignored, thus causing problematic readings
.
The filter is a moving window
taking the middle number
from an odd number of results
selectable between 1 and 21.
It is not a mean and it is
designed to totally ignore one
or more results as shown:
The seventh flow in the table above is zero. This could have been a small bubble passing
through the 710 flowmeter, which has a 1mm bore, which would completely absorb the
ultrasound. The median filter completely ignores this reading and for the zero reading
returns the value of 3 from the results either side. This filter is particularly useful at low flows
where a small dip in value could drop a result below the internal cut off levels.
