Euchner EKS FSA with Profibus-DP Interface Instrukcja Użytkownika Pobierz pdf (Strona 15)

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)

Loop impedance

≤ 110 Ω/km

Core diameter > 0.64 mm

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

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