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A Procentec 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 ProfiTrace 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 by measuring the width of the resulting reflection 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. Note that remote end of cable is here fitted with normal 9-pin PROFIBUS connector, with terminator switch set ON (but without connection to Slave or Active Terminator for power). Alternatively connect an approximately 220 ohm resistor between red and green cable cores at far end.






















Turn on the Scopeware cursors by clicking on the 'Cursors active' box, then measure the width of the waveform distortion by aligning the two vertical cursors either side of the reflection step, reading corresponding cable length value from left side of screen, as in following illustration.























Note also that, once you have ProfiCore Ultra running in Stop Mode, you will also be able to run the Topology Scan program, which willl automatically measure and display the cable lengths up to and between any detected slaves - see following Commissioning link for further details.


ProfiTrace for Commissioning New PROFIBUS Networks