Vega VEGABAR 67 Foundation Fieldbus - climate compensat Bedienungsanleitung PDF herunterladen (Seite 20)

5 Connecting to power supply

VEGABAR 67 • Foundation Fieldbus - climate compensated

39446-EN-130321

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accordingtoFoundationFieldbusspecication

Tip:

We recommend VEGA overvoltage arrester B63-32.

Inhazardousareasyoumusttakenoteoftherespectiveregulations,

conformityandtypeapprovalcerticatesofthesensorsandpower

supply units.

The instrument requires a operating voltage of 9 … 32 V DC. Operat-

ing voltage and the digital bus signal are carried on the same two-wire

connection cable. Power is supplied via the H1 power 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.

On the instrument with cable entry ½ NPT and plastic housing there is

ametallic½"threadedinsertmouldedintotheplastichousing.

Caution:

No grease should be used when screwing the NPT cable gland or

steel tube into the threaded insert. Standard grease can contain

additives that corrode the connection between threaded insert and

housing.Thiswouldinuencethestabilityoftheconnectionandthe

tightness of the housing.

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, 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 ceramic capacitor (e.g. 1 nF, 1500 V). The

Safety instructions

Voltage supply

Connection cable

Cablegland½NPT

Cable screening and

grounding

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