Ultraflux Uf 841, User Manual

Page: 54 / 105

54
NT UF 841 CP GB (d) / June 2015
2) Filter
The flow measurement can be filtered so as to make the measurement results more legible.
This feature must be used when the flow is extremely chaotic and an average for the flow needs to be
produced in order to view its evolution.
The diagram below illustrates the effect of the filtering in the event of a very versatile and turbulent
measurement:
The filter time constant, given in seconds, defines the "force" of the filtering: following a flow rate step
(quick opening of the isolation dam), the value measured reaches the final value at 1% after the time
constant.
To adjust this time constant, a simple rule involves taking as the time constant a value equal to two or three
times the foreseeable duration of any interference: for example, if you wish to avoid seeing flow variations
quicker than every 20 seconds, give the time constant a value of 40 or 60 s.
However, you must ensure that the time constant is not too large, since this would risk masking significant
events.
Flow
Time
Measurement with filter
Measurement without filter