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18 Circuit Protection for High-Speed Serial Interfaces I ndustrial communication requires a high-reliability operation, which means protecting industrial communication equipment is extremely important. This article will take some time to discuss aspects of RS-485 and Ethernet connections. It will then provide some application examples. After that, we will look at some considerations depending on what kind of environment you might find yourself operating in. Finally, we will examine some potential electrical threats, and then finish with some solution examples. An amazingly high number of industrial nodes are currently in industrial applications. At present, estimates are more than 350 million of them in place. If one looks at the specific RS-485 versus Ethernet, Ethernet is growing faster. In the past year or two, Ethernet nodes have surpassed RS-485 nodes. The other thing to note about them is that Ethernet runs faster, up to 1GB/s, while RS-485 is limited to 10MB/s. Ethernet has another key feature when compared to RS-485. Ethernet can power over Ethernet, which is to power the field device. In contrast, RS-485 can transmit longer distances, up to approximately 1500m, while industrial Ethernet is limited to about 100m. This then begs the question: Where would design engineers favor the employment of RS-485 versus Ethernet? In general, designers would want to use Ethernet when one has a lot of data transmission. So, take security cameras or machine vision systems as examples. When you want to use RS-485, it would be in long transmission links such as remote I/O or other things you need to get out in the field, such as energy metering. This implies that it intensely matters where and how one will employ their industrial communication node. Location is critical to port protection. If you're going to have a line outside, one certainly needs to be aware of lightning, both where the outdoor port connection is and where it runs in and connects internally to a building. In long-distance runs, one needs to be concerned about CRAIG MORROW | Littelfuse, Inc. INDUSTRIAL COMMUNICATION PROTECTION for RS-485 and ETHERNET