Vega VEGADIF 65 4 … 20 mA Bedienungsanleitung PDF herunterladen (Seite 34)

5Connectingtopowersupply

VEGADIF 65 • 4 … 20 mA

36236-EN-130417

If screened cable is necessary, connect the cable screen on both

ends to ground potential. In the sensor, the screen must be connected

directly to the internal ground terminal. The ground terminal on the

outsideofthehousingmustbeconnectedtothepotentialequalisa-

tion(lowimpedance).

Ifpotentialequalisationcurrentsareexpected,theconnectiononthe

processing side must be made via a ceramic capacitor (e. g. 1 nF,

1500V).Thelow-frequencypotentialequalisationcurrentsarethus

suppressed,buttheprotectiveeectagainsthighfrequencyinterfer-

ence signals remains.

Warning:

Considerablepotentialdierencesexistinsidegalvanicplantsaswell

asvesselswithcathodiccorrosionprotection.Verylargeequalisa-

tioncurrentscanowthroughthecablescreenwhenthescreen

is grounded on both ends. To avoid this, the cable screen must be

connectedtogroundpotentialonlyononeend(insidetheswitch-

ing cabinet) in such applications. The cable screen must not be

connected to the internal ground terminal in the sensor and the outer

ground terminal on the housing nottopotentialequalisation!

Information:

The metallic parts of the instrument (antenna, transmitter, concen-

trictube,etc.)areconductivelyconnectedwiththeinnerandouter

ground terminal on the housing. This connection exists either as a

direct metallic contact or via the shielding of the special connection

cableoninstrumentswithexternalelectronics.Youcanndspecica-

tionsonthepotentialconnectionswithintheinstrumentinchapter

"Technical data".

Take note of the corresponding installation regulations for Ex applica-

tions.Inparticular,makesurethatnopotentialequalisationcurrents

owoverthecablescreen.Incaseofgroundingonbothsidesthis

can be achieved by the use of a capacitor or a separate potential

equalisation.

5.2 Connection procedure

Proceedasfollows:

1. Unscrewthehousingcover

2. If a display and adjustment module is installed, remove it by turn-

ing it to the left.

3. Loosen compression nut of the cable entry

4. Removeapprox.10cmofthecablemantle,stripapprox.1cm

insulationfromtheindividualwires

5. Insert the cable into the sensor through the cable entry

6. Lifttheopeningleversoftheterminalswithascrewdriver(see

followingillustration)

7. Insertthewireendsintotheopenterminalsaccordingtothewir-

ing plan

8. Pressdowntheopeningleversoftheterminals,youwillhearthe

terminal spring closing

Cable screening and

grounding

Connection cable

for Ex applications

Single/Double chamber

housing

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