Portable device for Profibus diagnosis

Is there such a thing out there?

Could anyone recommend something?

Not quite sure what you're after. Siemens used to do something called a BT200 (Bus Tester?, or how about a Bust Tester ?) which would give info on cable continuity and availability of slaves. Not sure if it's relevant for your needs.

I have a profibus network. Sometimes certain valves on that network fail to communicate. I need to diagnose what the problem is and that will include cable integrity checks.

We use these:

http://www.procentec.com/profitrace2/

Not cheap, but everything you need in one box.

The BT200 is very good for testing cable faults (90%+ of Profibus faults are cable faults) you can also examine individule nodes and test the recieve/transmit circuits.

You can also get Profibus analysers that are a combination of network adaptor and software that reads all packets going past on the bus and will give statistics for each node such as "Number of Resends" etc. From memory, you can also set it up to monitor/capture certain packets for example to/from a particular node. I've worked with profibus since its' introduction and only used an analyser twice - the first time it revealed a data consistency error on an S5 system and the second time it only confirmed that the network was fine.

Nick

OK, change of tack. I misinterpreted the idea of a portable tester as one that would be used on multiple different networks. You know, have one in your bag, carry it with you wherever you go and test networks anywhere.

You've actually got a single fixed network? And sometimes the slaves "fail to communicate". I'd get the whole network tested once. Thoroughly.
A well-installed Profibus network shouldn't be working "sometimes". Does the network ever recover from a fault without having to swap out a slave? If a slave has genuinely failed, that's one thing. But if there's a group of them communicating intermittently, and you can get them to recover comms (what do you presently do when comms has failed?) then I'd be very suspicious about the original installation.

Check all the usual things: segment lengths, terminating resistors, good earthing to a single point throughout the system, etc etc. Is there a pattern to the failures? Either by location or by time of day / day of week etc. Can you draw any conclusions from the failures? (You have logged all the occurences, right ? ) What about other equipment? Is it affecting when/how the errors happen?

Need more data ...

Softing has good products around this toppic. Data analyzer and physical tester.
www.softing.com