Industrial Bus Health Test using Fluke 225C Color ScopeMeter

1. Industrial Bus Health Test using Fluke 225C Color ScopeMeter Application

2. Application: Bus Health Test using Fluke 225C ProfiBus Test at the Wavin Plastics factory • Wavinmanufactureslarge volumes of plastic partsforinfrastructuralpurposeslike tap- and rainwatersystems, surfaceheating and cooling and last-miletelecom. • Wavin is best knownforits plastic pipes, of various types and diameters

3. Application: ProfiBus Test at Wavin Plastics factory Situation: • Factory Automation was originally based on centralized hardware and direct control, using ‘traditional’ control with e.g. 4-20 mA current loops and with all PLCs installed in the control room • Recently, conversion to Profibus control was rolled out in another section of the factory The conversion to Profibus allows for better control over production equipment and offers a data link to the office’s Ethernet environment. Hundreds of devices are now connected to the control-room over a single Profibus network cable.

4. Network installed • After installation and start-up, the new system was handed over to the factory maintenance crew • The maintenance engineers set up a full verification of the network • As an ‘acceptance test’ of the complete network • To collect reference data for future maintenance • To collect ‘day one’ data for a preventive maintenance schedule

5. Network verification • A full scan of the network was carried out using a Fluke 225C Color ScopeMeter with Bus Health Test capability. • At each individual network node, all signal parameters were verified against the Profibus signal standards…. • ….. and at each node, the eye-pattern was recorded. • All test results were positive….. except one.

6. All is fine, or…? At one particular bus node, ScopeMeter indicated an excessive overshoot in the signal, exceeding the signal requirements as defined in the ProfiBus standards The eyepattern confirmed that a large overshoot was present on the pulses, leading to severe distortion of the bus signal

7. Overshoots? On the Profibusmaincable (‘the trunk’), overshootsmaybecausedby: • Incorrect cabletermination • i.c. too few ortoomanyterminatorsswitchedon Note: terminatorsneed to beinstalledonly at bothphysicalends of the Profibustrunk • Cable split (“T-split”) in the trunk • Poor (bad) contact in the trunk • Incorrect cablelengthsbetweendevices • Makingthattoomanydevices are connected at almost the same spot on to the trunk • Givesexcessiveloading of the network ProfibusStandardsdictates a minimum distancebetweendeviceconnections of 1 meter (= 3.3 ft).

8. The root cause A further research through the network revealed a cabinet in which4 devices had been connected with very short wiring in between. A clear violation of the basic Profibus assembly rules !

9. ….in detail The same sections seen in more detail. Main signal cable entering the cabinet Interconnections within this cabinet

10. Remedy • The 3 cable segments were replaced by segments of 1 m each • The extra lengths of cable were routed through the cable support rail New test results (measured from the location at which originally the error was seen):

11. Conclusions • Errors on an industrial network can be identified easily using the ‘Bus Health Test’ function of the Fluke 225C or 215C Color ScopeMeter. • These ScopeMeters also allow you to find network errors before the errors bring the network to a full stop. • Even if a network appears to be working flawlessly, errors may be in there, which are going to hurt you – sooner or later. Better find those sooner than later! Fluke – Keeping your world up and running!