Operating instructions

40
8 Application examples
VEGAMET 625 • Double channel HART
28970-EN-150129
adjustedto 5 %, this corresponds to 181 litres. The volume should be
displayed in litres.
Carry out the adjustment in the signal conditioning instrument as
describedinchapter"Setup steps".Noadditionaladjustmentmust
hencebecarriedoutonthesensors.Forthemax.adjustment,llthe
vessel up to the requested max. level and accept the actually meas-
ured value. If this is not possible, the respective current value can be
entered alternatively. For the min. adjustment, empty the vessel up to
the min. level or enter the respective current value.
Todisplaythepercentagelevelcorrectly,selectunder"Measurement
loop - Linearization curve"theentry"Cylindrical tank".
Todisplaythevolumeinlitres,youhavetoenter"Volume"asunitin
litresunder"Measurement loop - Scaling".Theallocationisthencar-
ried out, in this example 100 % ≙ 10000 litres and 0 % ≙ 0 litres.
Percent is selected as reference value for the relays. The mode of re-
lay1issettooverllprotection,relay2getsmodedryrunprotection.
Toensurethatthepumpswitchesoincaseoffailure,thereaction
in case of failure should be adjusted to switching status OFF. The
switching points are adjusted as follows:
•
Relay1:Switch-opoint90%,switch-onpoint85%
•
Relay2:Switch-opoint5%,switch-onpoint10%
Information:
Theswitchonandopointoftherelaysmustnotbeadjustedtothe
same switching point because this would cause a permanent switchin
onandowhenthisthresholdisreached.Toavoidthiseectalso
withuctuatingproductsurface,adierence(hysteresis)of5%is
useful between the switching points.
8.2 Weir control of a water power station
Awaterpowerturbinemustbeprotectedagainstimpuritiesinowing
water. These impurities get stuck on the weir like on a screen. The
mustberemovedcyclacyllysothatthemax.owisensured.Ifthe
degree of impurity is too high, the water level in front of the system
raisesbecausethetotalwatervolumecannolongerowthrough.
Thedierencebetweenlevelinfrontofandaftertheweirishencea
measure of the degree of impurity and can be used to control the weir
cleaner.
The water level in front of the weir (upstream water) and after the weir
(downstream water) is measured each with a VEGAWELL 72 HART.
VEGAMET625generatesthedierence(h3)outofthesetwolevels
(measurementloop3).Ifthisdierenceistoohigh,asignalwillbe
outputted by one of the integrated relays triggering the weir cleaning.
Exemplary we assume a max. level of 2 m, the weir cleaning should
bestartedatadierenceof20cm.
Adjustment
Linearization
Scaling
Relay
Functional principle
Example