PROFIBUS cabling

A PROFIBUS cable (or a cable segment when using repeaters) can be checked with a few simple resistance measurements. The cable should meanwhile be removed from all stations:

1. Resistance between A and B at the start of the lead: approx. 110 Ohm

2. Resistance between A and B at the end of the lead: approx. 110 Ohm

3. Resistance between A at the start and A at the end of the lead: approx. 0 Ohm

4. Resistance between B at the start and B at the end of the lead: approx. 0 Ohm

5. Resistance between screen at the start and screen at the end of the lead: approx. 0 Ohm

If these measurements are okay, the cable is in working order. If bus errors still occur, however, these will generally be due to EMC interference, in which case refer to the PROFIBUS user organisation installation instructions (www.profibus.com).