PROFIBUS Cable Length Measurement with ProfiTrace

ProfiTrace kit provides an easy way to measure the length of PROFIBUS cables. The layout and size of operational network segments, if running at 500 kbps or 1.5 Mbps, can be mapped using the Procentec Topology Scan program. Alternatively, individual cables lengths can also be measured in isolation using the integrated ProfiCaptain waveform generator and Scopeware programs, without a special ProfiCaptain licence.

The ProfiTrace/ProfiCore Self Test Procedure explains how to run ProfiCaptain in this manner, generating a pulsing waveform from the ProfiCore Ultra. If you then connect a PROFIBUS cable to the ProfiCore, you will see associated changes in the Scopeware waveform, caused by cable loading and reflections. The Scopeware cursors may then be used to measure the cable length from the resulting waveform.

The normal ProfiCaptain Stop waveform is shown below, with the modified waveform caused by connection of a 33 metre PROFIBUS cable shown after this.

The width of the waveform distortion and corresponding cable length are measured by aligning the cursors either side of the step, as in following detail from the Scopeware display.