Tecfluid XT5 - Manual (Page 14)

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Only the flow rate indication of the display and the analog output are affected by the filter.
The pulse output and the totalizer act according to the instant flow rate. By selecting a
filter with a longer or shorter integration time will provide more or less stable readings and
will also affect the response time to small variations of flow rate.
The integration time is selected in seconds, with a minimum value of 0.1 and a maximum
value of 20.0 seconds. For example, with an integration time of 15 seconds, the display
will indicate the flow rate reading of the average flow rate over the last 15 seconds from the
last update of the display. This does not mean that the display is refreshing its data every
15 seconds. The display shows a new value several times per second, indicating an
average of the flow rate values of the last 15 seconds.
When there is a sudden variation of the flow rate then the filter should react as fast as
possible to give a correct reading of the new value. For this, the filter controls for each
reading the deviation of the instant flow rate with respect to a reference. If this deviation
exceeds the established limits, the filter will stop acting, indicating the instant value, and
will start again the filtering process.
In the following figure we can see the allowed deviation for the filter to continue giving
average values.
For example, consider a DN25 flow meter whose average flow rate is 4000 l/h.
4000 l/h corresponds to a liquid velocity of 2,27 m/s, situated in the second zone of the
graphic. This means that the filter will continue giving average readings whilst the instant
flow rate does not deviate more that 25% (1000l/h) from the average flow rate.
Since the average flow rate is 4000 l/h, the filter acts whilst the instant flow rate is within
3000 l/h and 5000 l/h.
If the average flow rate is for example 2000 l/h, it corresponds to a liquid velocity of 1,14
m/s, in this case we are in the first zone of the figure. This means that the filter will
continue acting whilst the instant flow rate does not deviate from the average flow rate
more that 10% from the nominal flow rate, that is 880 l/h (flow rate at 0,5 m/s in a DN25 =
880 l/h).
Since the average flow rate is 2000 l/h, the filter continues to act whilst the instant flow
rate is within 1120 l/h and 2880 l/h.
3.2.6 Flow rate direction
In this screen the flow direction for which the flow rate indication will show a positive value
can be programmed.
Average flow rate
25% of instant flow rate
10% of nominal flow rate