Delphin ProfiMessage - 7.3 Earth loops

ProfiMessage
ConnectthePEterminalwitha≥2.5mm2cabletothe

protectiveearthofyour
powersupply.
ReferalsotoShielding,Galvanicisolation.
7.3 Earth loops
Bylinkingsensor,measurementdevice,andcomputer,connectionsthenexist
betweendifferentgroundpoints.Unlesstheindividualdevicesareconnectedto
protectiveearth,thiselectroconductiveconnectioncreatesanelectricalcircuit
betweenthedevices.Theresultiswhatisknownasanearthorgroundloop
(shownredintheexample).
This can have the following effects:
l InpracticetheearthingpointsU1toU3showninthegraphdonotneces-
sarilypossessequalpotential.Constantorchangingpotentialdifferences
canoccurbetweentheearthingpointsduetotheearthingplanandwiring.
Compensatingcurrentsthenoccurinthesensorandcommunicationcir-
cuits.
l Interferenceinthesensororcommunicationcircuits,forexamplethrough
electromagneticfields,enableparasiticcurrentstooccurwithinthecircuit.
Compensationandparasiticcurrentsleadtointerferenceornoisevoltageatthe
inputofthemeasuringinstrumentandthusconstantorshiftingerrorsinmeas-
urement.
214
Delphin Technology AG
Dezember 2015
ProfiMessage Manual