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6 profibus-dp, Specification for bus cables, 1 bus connection – EUCHNER EKS FSA with Profibus-DP Interface User Manual

Page 15: 2 permissible cable lengths, 1 bus, Connection, 2 permissible, Cable lengths, Manual eks electronic-key adapter profibus-dp

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Manual EKS Electronic-Key Adapter Profibus-DP

4.6 Profibus-DP

Specification for bus cables

A cable specified as cable type A according to EN 50170 must be used for the bus connection:

Parameter

Cable type A

Unit

Cable structure

Two core twisted, screened

Effective capacitance

pF/m

≤ 30

Characteristic impedance

135 ... 165 (at a frequency of 3 ... 20 MHz)

Ω

Loop impedance

≤ 110

Ω/km

Core diameter

> 0.64

mm

2

Core cross-section

> 0.34

mm

4.6.1 Bus connection

On Profibus-DP every bus segment must be terminated at the start and end with a resistor.

Information!

The Electronic-Key adapter does not contain an internal switchable bus termination resistor!
If the Electronic-Key adapter is the last device on the cable, a bus plug with switchable bus termination
resistor must be used.

Information!

To enable subscribers to be coupled and uncoupled to and from the Profibus as required while it is in
operation, active RS485 termination elements are available. With the active RS485 termination
element, the termination resistor is permanently supplied with power separately from the other
peripheral subscribers. As it is operated independently of the bus subscribers, it can be coupled and
uncoupled without interaction.

4.6.2 Permissible cable lengths

The permissible cable length in a bus segment is dependent on the cable type, the data transfer rate, the
number of bus subscribers and external interference.

The table gives the maximum cable length for a bus segment as a function of the data transfer rate with the
maximum number of subscribers of 32:

Parameter

Value

Unit

Data transfer

rate

3000/

93.75 187.5 500 1500

kbps

6000/12000

Cable type A

1200

1000

400

200

100

m

092009-03-10/07

Subject to technical modifications

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