VEGA VEGAMET 624 - Manual (Page 39)

39
8 Application examples
VEGAMET 624 • 4 … 20 mA/HART
28969-EN-130701
When the level was not changed for a longer period, always the same
pump would have been switched on. Via the parameter "Changeover
time", a time can be preset after which a forced changeover of the
pump is carried out. Which pump will be switched on depends ont he
selected pump mode. If all pumps are already switched on, then the
pump still remains switched on. These function can be only adjusted
via PC and DTM.
Note:
If the pump is already switched on when activating the forced
changeover, the timer will not be started. Only after switching off and
on again, will the timer start. If the switch-off delay is set, it will not
be taken into account, i.e. the changeover is carried out exactly after
the preset time for the forced changeover expires. A preset switch-on
delay, however, is taken into account, i.e. the forced changeover to
another pump is carried out after the preset time expires. Before the
newly selected pump switches on, the preset switch-on delay for this
pump must be expired.
8.3 Tendency recognition
The function of the tendency recognition is to recognize a defined
change within a certain time period and to transfer this information to
a relay output.
The information for tendency recognition is generated out of the
measured value change per time unit. The output variable is always
the measured value in percent. The function can be configured for
rising and falling tendency. The actual measured value is determined
and summed with a sample rate of a second. After the max. reac-
tion time, the average value is generated out of this sum. The real
measured value change results then of the newly calculated average
value less the previously calculated average value. If this difference
exceeds the defined percentage value, the tendency recognition
responds and the relay deenergises.
Note:
Activation and configuration of tendency recognition requires PACT-
ware with the suitable DTM. The respective parameters cannot be set
via the integrated display and adjustment unit.
•
Measured value change higher: Measured value change per
time unit, at which the tendency recognition should respond
•
Max. reaction time: Time after which a new measured value
generation is carried out and the measured value change is
recalculated
•
Hysteresis: is automatically always 10 % of the value of "Meas-
ured value change larger than"
•
Reaction in case of failure: In case of a failure, the relay goes
into the defined condition
Option forced changeo-
ver
Functional principle
Principle of operation
Parameter