KROHNE OPTIMASS with MFC 300 EN - Manual (Page 126)

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Pressure Suppression
The Pressure Suppression feature eliminates any influences on the measurement result of
sudden termination of flow, for example when a valve is shut. When this occurs the propagation
of pressure waves along the pipe work and through the meter may produce an “Over-shoot” or
“ringing” effect, where the flow rate will oscillate backwards and forwards until it settles to a
stable zero flow condition, as is indicated in the diagram below. Typically this will only be
noticeable on high pressure applications.
In most cases the amplitude of the ringing will be below the “Low Flow Threshold” and will
therefore not influence the result. However, in some cases the amplitude of the ringing is
above the Low Flow Threshold and could cause an error in the totaliser values.
The pressure suppression function eliminates this effect, by increasing the Low Flow Cutoff for
a short period of time, triggered when the flow first drops below the Low Flow Threshold.
For a set time period (set in menu C1.3.2) the pressure suppression threshold (set in menu
C1.3.3) is added to the standard Low Flow Threshold.
1 Flow Switch off
2
Sinudoidal Ringing
3
Stable Zero Flow
1
2
3
1
2
1 2
Low Flow Threshold