the connection are ready to run, or highlight which one has failed.
 
“One of the things Ethernet brings is point-to-point technology. It’s evolved to a switched infrastructure so everything is connected point-to-point,” VanGompel says. “With point-to-point, simple LEDs (light emitting diodes) on a device can make it easier to troubleshoot.”

Compromised cables?

Product developers have invested a lot of time and research effort into one of the more vexing problems on the plant floor—broken or disconnected cables. Pinpointing the point where wires are broken can be a very time-consuming task. The switches that commonly connect Ethernet network segments are critical elements for this capability. Unlike conventional unswitched field buses, switched Ethernet networks can monitor what’s going on with cables. Data and system monitoring software is typically designed into this hardware.

“One nice things about managed switches is that you have diagnostics in the infrastructure,” says Henning. “The switches keep a lot of statistics, so you know if you’re having a lot of retries or where something on the cable went if it’s disappeared.”

Managed switches provide far more diagnostics than unmanaged switches. Unmanaged switches only provide some LED alerts on the front panel, providing far less information, Henning notes.

Some industrial versions of Ethernet have more capability to recover from cable breaks than others.  Joey Stubbs, North American Representative for the EtherCat Technology Group, in Volente, Texas, notes that EtherCat handles telegrams differently than other real-time versions of the standard, providing more support. A link detection notes faults and closes problem ports. Telegrams are then sent back to the controllers.“Each slave device has its own support structure, so frames are returned even if you have a sheared cable,” Stubbs says. “We can get localized diagnostics even when a slave loses power or its onboard processor dies.”

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