KROHNE OPTIMASS Series Handbook page 82

Pressure Suppression Fct. 3.1.8 and 3.1.9
The Pressure Suppression feature eliminates any influences on the measurement result of sudden
termination of flow, such as 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. In some cases however the amplitude of the ringing is above the Low Flow Threshold
and could contribute 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 Fct. 3.1.8) the pressure suppression threshold (set in Fct 3.1.9) is added to the
standard Low Flow Threshold (set in Fct. 3.1.1).
Settings of these parameters depend on actual process conditions and characteristics of the pipework and
so can only be determined by experimentation in-situ.
Installation and Operating Instructions OPTIMASS 81