Industrial Data Xchange (IDX) is a South African based ICT industrial company with a global focus specialising in the provision of data communication solutions. On this blog, IDX experts comment on industrial communication protocols, trends, and tips as well as what is on the go in the labs at IDX.
PROFIBUS wiring error / B-line short
PROFIBUS wiring error / B-line short
IDX attended a PROFIBUS call out for a gold mine situated in Welkom.
The client reported issues as
“loss of communication and network trips”.
Using the PROCENTEC Mercury Pro
Kit (A complete diagnostics tool for troubleshooting PROFIBUS and Industrial
Ethernet Networks) we were able to identify the underlying issue as a short
between the B-core (red wire) and the PROFIBUS cable shield.
The short in the PROFIBUS cable
meant that the differential signal was significantly lower in amplitude and
therefore more susceptible to earthing faults and EMI injections on the bus.
PROFIBUS makes use of a balanced
signal. This means that the signal transmitted on the A and B channels have
similar voltage levels, however, they have opposite polarities. The
differential signal is calculated as B – ( – A).
When a short occurs on the
PROFIBUS cable between either of these cores and the PROFIBUS cable shield, the
shorted core will produce a flat line and the resultant differential signal
will effectively be halved.
This balanced communication
method, also helps to combat any noise that may be picked up on the network.
The assumption is that any interference injected on the bus will be picked up
on both the A and B channel which, when combined, will result in a clean
was still running on a single core, the interference injected onto the network
when certain machines or drives were started, was enough to cause communication
issues and intermittent network trips.
An oscilloscope that is able to
display the individual signals of each of the cores is necessary to effectively
identify a “short to shield”. Both the Osiris software (Mercury Pro Kit) and
the ProfiTrace software (PROFIBUS Troubleshooting Tool Kit) have this
functionality built in.
By enabling the terminating
resistors at certain points on the segment, we could pinpoint the exact
location of the fault and replace the faulty cable.
After limited down-time for the
repair work to take place, we had the network up and running. Oscilloscope
measurements taken after the fault had been rectified confirmed a healthy
PROFIBUS signal on both A & B channels and in turn, a much more robust
No network trips have since been
Maintaining your existing
connections, in this case maintaining a healthy PROFIBUS network, is the
responsibility of the on-site technical team.
As with anything, the necessary
knowledge and the right tools for the job are required to ensure that your
production is not affected.
Simply IDX it! If you’re looking
for certified industrial communications protocol training, if you want to
become a certified PROFIBUS installer and work your way up to a certified PROFIBUS engineer, if you’re looking for troubleshooting kits or permanent
monitoring for your network, contact us and we’ll provide a solution. Feel free to contact the IDX team if you would like to find out more detail on any of the topics mentioned above: firstname.lastname@example.org +27 11 548 9960
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