Vega VEGABAR 81 Profibus PA - Operating Instructions Bedienungsanleitung PDF herunterladen (Seite 20)

5 Connecting to power supply

VEGABAR 81 • Probus PA

45020-EN-131107

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

The voltage supply is provided by a Probus DP /PA segment coupler.

The voltage supply range can dier depending on the instrument

version. You can nd the data for voltage supply in chapter "Technical

data".

Connection is made with screened cable according to the Probus

specication. Power supply and digital bus signal are carried over the

same two-wire connection cable.

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.

Please make sure that your installation is carried out according to the

Probus specication. In particular, make sure that the termination of

the bus is done with appropriate terminating resistors.

You can nd detailed information of the cable specication, installa-

tion and topology in the "Probus PA - User and Installation Guide-

line" on www.probus.com.

With plastic housing, the NPT cable gland or the Conduit steel tube

must be screwed without grease into the threaded insert.

Max. torque for all housings see chapter "Technical data".

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.

With 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

T-distributor, the screen of the short stub to the sensor must not be

connected to ground potential or to another cable screen. The cable

screens to the power supply unit and to the next distributor must be

connected to each other and also connected to ground potential via a

Safety instructions

Voltage supply

Connection cable

Cable gland ½ NPT

Cable screening and

grounding

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