Vega VEGAMET 861 - Page 45

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11 Applications and functions
VEGAMET 861 • 4 … 20 mA/HART
58866-EN-200401
Via the digital inputs, possible fault signals of the pumps can also be
evaluated.Youcanndthedescriptionofthisintheapplicationexam-
ple "Pump control 1/2" under "Pump monitoring".
Thispumpcontrolsystemoerstwodierentoptions:
•
Pump control 3: The upper switching point determines the switch-
opointfortherelay,whereasthelowerswitchingpointdeter-
mines the switch-on point
•
Pump control 4: The upper switching point determines the switch-
on point for the relay, whereas the lower switching point deter-
minestheswitch-opoint
The sequence cannot be changed, the relay with the lowest index is
switchedonrst,thentherelaywiththenexthigherindex.Afterthe
relay with the highest index, the relay with the lowest index follows, for
example Rel. 1 -> Rel. 2 -> Rel. 3 -> Rel. 4 -> Rel. 1 -> Rel. 2 …
The sequence applies only to those relays assigned to the pump
control.
In a waste water disposal system, a sump should be pumped empty
when a certain level is reached. Three pumps are available for this. At
60 % level, pump 1 should run until the level has fallen below 10 %.
If the 60 % point is exceeded again, the same task is transferred to
pump 2. In the third cycle, pump 3 is activated; after that, pump 1
again. If the level continues to rise despite operation of a pump, an
additional pump switched on when the level exceeds the 75 % switch-
ingpoint.Andifthelevelstillrisesfurtherduetoextremeinowand
exceeds the 90 % limit, pump 3 is also switched on.
For relay 1 … 3, the mode of operation "Pump control 4" is adjusted
with the option "Sequenced operation". The relay switching points are
conguredasfollows:
Select in the DTM navigation section the menu items "Meas. loop -
Outputs - Relay".
•
Relay 1 upper switching point = 60.0 %
•
Relay 1 lower switching point = 10.0 %
•
Relay 2 upper switching point = 75.0 %
•
Relay 2 lower switching point = 10.0 %
•
Relay 3 upper switching point = 90.0 %
•
Relay 3 lower switching point = 10.0 %
The function of pump control 4 is shown in detail in the following dia-
gram. The previously described example is used as a basis.
Example