Operating instructions

45
8 Application examples
VEGAMET 625 • Double channel HART
28970-EN-150129
Switch on reaction of the pump control 2
When the signal conditioning instrument is switched on, the relays are
atrstinaswitched-ostatus.Dependingontheinputsignalandthe
switched-on period of the individual relays, the following relay switch-
ing conditions can occur after the start procedure:
•
Input signal is higher than the upper switching point -> Relay with
the shortest switch on period is switched on
•
Input signal is between lower and upper switching point -> Relay
remainsswitchedo
•
Input signal is smaller than the lower switching point -> Relay
remainsswitchedo
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oand
onagain,willthetimerstart.Iftheswitch-o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.
8.5 Tendency recognition
Thefunctionofthetendencyrecognitionistorecognizeadened
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conguredfor
rising and falling tendency. The actual measured value is determined
and summed with a sample rate of asecond. 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dierence
exceedsthedenedpercentagevalue,thetendencyrecognition
responds and the relay deenergises.
Note:
ActivationandcongurationoftendencyrecognitionrequiresPACT-
ware with the suitable DTM. The respective parameters cannot be set
via the integrated display and adjustment unit.
Option forced changeo-
ver
Functional principle
Principle of operation