Vega VEGAMET 861 - Page 44

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11 Applications and functions
VEGAMET 861 • 4 … 20 mA/HART
58866-EN-200401
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 have expired.
With a pump control, there is also the possibility of switching on pump
monitoring. For this purpose, a feedback signal is required on the re-
spective digital input. The digital inputs are assigned 1:1 to the relays.
Digital input 1 acts on relay 1, etc.
If the pump monitoring for a relay was switched on, a timer is started
when the relay is switched on (time allowance with parameter
"Report time"). If the checkback signal comes from the pump on the
respectivedigitalinputwithinthedenedreporttime,thepumprelay
remainsenergized,otherwisetherelayisimmediatelyswitchedo
andafaultsignaloutputted.Afaultsignalandaswitchingoofthe
relay is carried out even if the relay is already switched on and the
pump checkback signal changes during the running time of the pump.
Inaddition,aswitched-orelayofthepumpcontrolislookedforand
switched on instead of the faulted relay. A Low signal on the digital
input is evaluated as a pump error signal.
The fault message is cancelled when the signal on the digital input
changes to "Good" or when it is reset via the "OK" key and selection
of the menu item "Acknowledge failure". If the fault message is reset
via the menu and the pump still signals failure, a fault message is
triggered after the enquiry period. The enquiry period is started as
described above when the relay is switched on.
Switch-on behaviour of pump control 2
Whenthecontrollerisswitchedon,therelaysareatrstina
switched-ostatus.Dependingontheactual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 switched-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
Application example pump control 3/4
Pump control 3/4 is used to control several pumps with the same
functionalternatelyandinaxedsequence.Incaseofincreased
pumping requirement, all pumps can also run at the same time, in
dependence on the entered switching points. This measure achieves
an even utilization of the pumps and increases operational reliability.
All relays with activated pump control are not assigned to a certain
switchingpointbutareswitchedonandoalternately.Whenaswitch-
on point is reached, the controller selects the relay that is next in the
sequence.Whenaswitch-opointisreached,therelaysareswitched
ointhesequencetheywereswitchedon.
Pump monitoring
Functional principle