User guide

20
5Connectingtopowersupply
MINITRAC 31 • Foundation Fieldbus
41782-EN-131119
5 Connecting to power supply
5.1 Preparing the connection
Alwayskeepinmindthefollowingsafetyinstructions:
•
Connect only in the complete absence of line voltage
•
If overvoltage surges are expected, overvoltage arresters should
be installed
Powersupplyanddigitalbuscableviaseparatetwo-wireconnection
cables.PowerissuppliedviatheH1voltagesupply.
ConnectioniscarriedoutwithscreenedcableaccordingtoFieldbus
specication.
Usecablewithroundcross-section.Acableouterdiameterof
5…9mm(0.2…0.35in)ensuresthesealeectofthecablegland.
Ifyouareusingcablewithadierentdiameterorcross-section,
exchange the seal or use a suitable cable gland.
Make sure that the entire installation is carried out according to the
Fieldbusspecication.Inparticular,makesurethatthebusistermi-
natedwithsuitableterminatingresistors.
Generallyprovideallunusedcableentrieswithsuitableblindplugs.
Thethinfoamrubberwashersinthecableglandsonlyserveasa
dust cover during transport.
Inthecaseofinstrumenthousingswithself-sealingNPTthreads,it
isgenerallynotpossibletohavethecableglandsscrewedinatthe
factory.Theopeningsforthecableglandsarethereforecoveredwith
red protective caps as transport protection.
Beforesetupyouhavetoreplacetheseprotectivecapswithapproved
cableglandsorclosetheopeningswithsuitableblindplugs.Unused
cableglandsdonotprovidesucientprotectionagainstmoistureand
mustbereplacedwithblindplugs.
Thesuitablecableglandsandblindplugscomewiththeinstrument.
Make sure that the cable screening and ground is executed accord-
ingtotheFielbusspecication.Ifelectromagneticinterferenceis
expectedwhichisabovethetestvaluesofEN61326-1forindustrial
areas,werecommendtoconnectthecablescreenonbothendsto
ground potential.
Insystemswithpotentialequalisation,connectthecablescreen
directlytogroundpotentialatthepowersupplyunit,intheconnection
box and at the sensor. The screen in the sensor must be connected
directly to the internal ground terminal. The ground terminal outside
onthehousingmustbeconnectedtothepotentialequalisation(low
impedance).
Insystemswithoutpotentialequalisationwithcablescreeningon
both sides, connect the cable screen directly to ground potential at
thepowersupplyunitandatthesensor.Intheconnectionboxor
Safety instructions
Voltage supply
Connection cable
Cable entry
Cable gland ½ NPT
Cable screening and
grounding