DCS ADR24 Instructions d'exploitation télécharger pdf (Page 35)

VEGASON 51P … 53P 35

Electrical connection

5 Electrical connection

5.1 Connection – Connection cable

– Screening

Safety information – Qualified person-

nel

Instruments which are not operated with

protective low voltage or DC voltage must

only be connected by qualified personnel.

This is also valid for the configuration of

measuring systems planned for Ex environ-

ment.

As a rule, do all connecting work in the com-

plete absence of line voltage. Always switch

off the power supply before you carry out

connecting work on the radar sensors. Pro-

tect yourself and the instruments.

Connection cables and bus configura-

tion

Note the Profibus specification. The connec-

tion cables must be specified for the ex-

pected operating temperatures in the plant

and must have an outer diameter of

6 … 12 mm, to ensure the seal effect of the

cable entry on the sensor.

For power supply and bus communication, a

two-wire cable acc. to the Profibus specifica-

tion (up to max. 2.5 mm

2

conductor cross-

section) can be used. The electrical

connection on the sensor is made by means

of spring-loaded terminals.

In a laboratory setup, a Profibus system will

also work with standard, unshielded two-wire

cable. In practice however, an automation

network and bus system can only be pro-

tected reliably against electromagnetic inter-

ference with screened cable. Acc. to the

Profibus specification (IEC 1158-2) screened

and twisted cables are prescribed.

All participants are connected in line (seri-

ally). At the beginning and end of the bus

segment, the bus is terminated by an active

bus termination. On the DP bus level, most

participants already have a bus termination

implemented. With more than 32 participants

on the DP level, a so-called repeater must be

used to open and combine another DP level

with a max. of 32 participants. On the PA bus

branch of the segment coupler, the PA ultra-

sonic sensors work also with max. 32 partici-

pants (Ex max. 10 participants).

A PA sensor can work only in conjunction with

a Profibus DP system, to which a Profibus PA

subsystem is connected. A PA Profibus par-

ticipant must consume min. 10 mA supply

current.

Connection cable and cable length

Connection cables must correspond to the

Profibus specification and the FISCO model.

The sensor cable must be in conformity with

the values of the reference cable acc. to

IEC 1158-2:

0.8 mm

2

; R

DCmax.

= 44 W/km;

Z

31.25kHz

= 80 … 120 W; damping = 3 dB/km;

C

asymmetric

= 2 nF/km.

The max. cable length first of all depends on

the transmission speed:

up to 94 kbit/s: 1200 m Profibus DP

up to 188 kbit/s: 1000 m Profibus DP

up to 500 kbit/s: 500 m Profibus DP

up to 1500 kbit/s: 200 m Profibus DP

up to 12000 kbit/s: 100 m Profibus DP

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