Vega POINTRAC 31 Foundation Fieldbus Bedienungsanleitung PDF herunterladen (Seite 16)

5 Connecting to power supply

POINTRAC 31 • Foundation Fieldbus

41779-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

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