Connecting LR560 Profibus PA

Hi

Iam using LR560 Profibus PA model 7ML54401GA001BA2-Z

1. When I see the terminal diagram of it I see only two terminal, as shown in section 5.2 of this manual How will I connect two such LR560 then? I was expecting 2 terminals from incoming and two for outgoing
2. Also LR560 will get power from Profibus PA bus, is it right?
3. Is there limitation to length of profibus PA cable from PLC to field?
4. My profibus network is working 1.5Mbps, will this matter to connect profibus PA device via DP/PA coupler? 

Hello Manmeet;

On Profibus-PA instruments there are only 2 connectors for the fieldbus, that is correct. Connectivity packages come in 2 different designs that I know of, using the same standard Profibus-PA cable. All intruments on Profibus-PA are powered by the PA couplers.

Siemens proposes a "Split-Connect" system where the trunk cable (from the Profibus-PA master) allows for a spurline (stub line, drop-cable) to the instrument. If you read the specifications for Profibus-PA you will see that it specifies the maximum length of spurlines in a network, depending on the number of instruments connected. Page 3-8 f the manual proposed by Levelmans earlier shows the total length of the PA network and the length of allowed spurlines 

You will find information on the Split-connect system in chapter 6 of the Profibus networks manual:

https://support.industry.siemens.com/cs/af/en/view/1971286

Weidmuller offers similar (in concept) T-Connectors for Profibus-PA, more robust that the Split-Connect system:

https://files.clrwtr.com/userfiles/ct/documents/weidmuller/weidmuller-profibus-pa-distributor.pdf

Another connection technique consists of using specially designed hubs, from MTL  for example. We used the MTL Megablocks on many projects. They were designed originally for Foundation Fieldbus connectivity, but since Profibus-PA and FF follow the same physical standards they work well on PA instruments.

http://www.vsp-co.org/assets/f300-megablocks-rev7.pdf

The Megablock hubs connect 4, 8 or 12 instruments to a continuous trunk cable. Again the total length of spurlines must be taken into account when designing the network, and terminating resistors must be purchased (and installed on the last hub of the trunk) seperately. One added advantage of these hubs is that they offer surge protection on every PA line, and also come with Zone 2 Div 2 area protection.

Hope this helps,

Daniel Chartier