Xylem Expert 800-900 - Manual (Page 34)

Manual
GB Manual Expert Log 800-900.doc
34
Overstort-calculation (storm flow, Overflow calculation)
In some countries (e.g. Holland, Belgium) water consumption is measured with the help of an overstort
wall. The volume of water consumed is calculated from the measured water level minus the Trigger-in-
value (Val1) configured with the WriterWL. This Trigger-in-value corresponds to the distance of the
sensor from the overstort wall. Trigger-out (Val2) should be set to the value Trigger-in – 3cm, in order
to attain a turn-off hysteresis.
Poleni's formula is used for flow calculations: Q = 1.7 x m x b x h 3/2
Q = flow
1.7 = fixed correction factor
m = construction factor
b = width of the overstort wall
h = water level above the overstort wall (Recorded value – Trigger-in-value)
The total overstort-volume is calculated using all calculated and intermediary flows and the
corresponding duration of the overstort.
The module creates a detailed record, which can be printed as a report under "File – Print...”.