Delphin ProfiMessage - 7.4 Shielding

ProfiMessage

Prevent earth
loops.
Sensor—measurement device earth loop
Galvanicisolationoftheinputstothecentraldevice,meansearthloopsviathe
sensorcircuitasshownintheexample,cannotoccurwithinthedevice.Earth
loopscanhoweveroccurbetweenthesensorsofdifferentchannelsofamodule.
Toavoidsuchloops,werecommendtheuseofearth-freesensorsorsignal
sources.
SeealsoPotentialdifferences.
Measuring device—computer earth loop
Mostofthedevice'sinterfacesaregalvanicallyisolatedtowardseachotherand
towardsthecentraldevice.Theearthloopthroughthecommunicationcircuitas
shownintheexampledoesnotoccurwiththisdevice.
UsetheseinterfacestoconnectthedevicetoPCs,PLCsortoothermanufacturers’
equipment.
SeealsoGalvanicisolation.
7.4 Shielding
Measurementsignalscanbedisruptedbytheoccurrenceofmagneticandelectric
fieldsinthemeasuringcircuits,forexamplegeneratedbyneighbouringcurrent-
carryingcircuits.Shieldedcablesshouldthereforealwaysbeusedforsensorcir-
cuitryandkeptatleast50cmawayfromothercurrent-carryingcircuits.
Thesmallerthesensorsignaland/orthehigherthesensorimpedance,themore
importantgoodshieldingbecomesforalownoise,accuratereading.
215
Delphin Technology AG
Dezember 2015
ProfiMessage Manual