Operating instructions

47
8 Application examples
VEGAMET 625 • Double channel HART
28970-EN-150129
8.6 Flow measurement
Forowmeasurementinopenumes,acontractionorstandardised
umemustbeused.Dependingontheowvolume,thiscontraction
generatesacertainbackwater.Theowcanbedeterminedfromthe
heightofthisbackwater.Theowvolumeisoutputtedbyanappropri-
ate number of pulseson the relay or current output.
Dependingonthetypeandversion,eachumegeneratesadierent
backwater.Thedataofthefollowingumesareavailableintheinstru-
ment:
•
Palmer-Bowlus-Flume
•
Venturiume,trapezoidalweir,rectangularweir
•
Rectangular weir, V-Notch
Setup
ThecongurationoftheowmeasurementlooprequiresPACTware
withthesuitableDTMs.Theexamplereferstoaowmeasurement
with a radar sensor. The following setup steps must be carried out:
•
Selectionoftheparameter"Flow"
•
Carrying out adjustment
•
Selectume(linearization)
•
Set scaling
•
Parameter adjustment of pulse outputs
SelectintheDTMwindow"Parameter"theoption"Flow"withthe
requested unit of measurement.
Min. adjustment:
Enter the suitable value for 0 %, i.e. the distance
fromthesensortothemediumaslongasthereisnoow.Theseare
in the following example 1.40 m.
Max. adjustment: Enter the suitable value for 100 %, i.e. the distance
fromthesensortothemedium,withthemax.owvolume.Thisis
0.80 m in the following example.
100% 0,80m (d)
=
400m
3
/h
=
0% 1,40m (d)
=
0m
3
/h
=
Fig. 16: Adjustment of ow measurement with V-notch
SelectintheDTMwindow"Linearization"theoption"Flow"andthen
theusedume(intheaboveexampleV-notch).
Functional principle
Flume
Parameter - Flow
Adjustment
Linearisation curve