Until recently Ethernet wasn’t allowed into intrinsically safe (IS) areas, where even its comparatively low power might combine with ambient conditions to spark a fire or explosion. Thankfully, the organizers and members of the Ethernet-Advanced Physical Layer (APL) organization have been developing its specification, which includes stepping down its power with help from the IEC TS 60079-47 standard, enabling its use in IS applications. This and its 10Base-T1L speed of 10 Mbps over 1,000-meter trunks and 200-meter spurs will no doubt accelerate Ethernet-APL's performance gains.
However, some of Ethernet-APL’s ardent supporters didn’t or couldn’t stop there. During several interviews for this issue’s “What can Ethernet-APL do for you?” cover story, several sources implied that Ethernet-APL also provides interoperability, which it doesn’t. This is because, even if Ethernet-APL can cross into and serve in IS areas, it’s still just a two-wire physical layer with the usual Ethernet communication protocols running on top. As usual, even though they can occupy the same network, they still can’t communicate across protocols without lots of translation/conversion assistance, and devices using one Ethernet protocol still can’t plug-and-play or control devices using another protocol.
When I asked how Ethernet-APL could deliver interoperability, most sources backed off or deftly rationalized that it could help improve conditions for eventual interoperability. I wouldn’t have pressed them if I hadn’t remembered reporting Control’s “Alive and growing,” Feb.’16 cover article. Without that knowledge, I’d just as likely have taken their word about Ethernet and Ethernet-APL's alledged interoperability.
Not only that, when I went to compile and write this month’s In Process news section, it seemed like every other item was talking about interoperability. For example, ABB and a who’s who of suppliers launched their Margo initiative Apr. 23 to provide “interoperability for IIoT ecosystems." On the same day, FieldComm Group reported that it’s acquiring FDT Group to “develop a protocol-agnostic, device-integration approach to foster alliances with other field-protocol organizations” and “enhance interoperability.” Finally, the OPC Foundation launched an initiative on Apr. 22 to “boost interoperability across IT and cloud platforms using OPC UA.”
Why is everyone talking about interoperability? Well, it could be because Hannover Messe was just held in Germany, where many springtime announcements in automation and control are made. However, I think there’s so much buzz about interoperability because the user-driven Open Process Automation Standard (O-PAS) is moving from multiplying field trials to manufacturing sites. It standardizes interactions between distributed control nodes (DCN) on a common O-PAS connectivity framework (OCF) that relies on OPC UA. It’s expected to deliver much of the plug-and-play interoperability that's been kept from many users since at least 1999, when “helpful” suppliers shackled them with the eight-headed IEC 61158 fieldbus non-standard.
Times have changed, of course, and many suppliers are more conscious about what their customers require. However, the undercurrent to make sales and protect market share is also as strong as ever, and continues to spur some suppliers to perhaps overpromise on the capabilities of Ethernet-APL and other technologies, especially if they’re unquestioned and unchallenged.
As always, users must get educated about Ethernet-APL and other potential solutions, be willing to ask probing and annoying questions about applying them, and most importantly, test and evaluate devices before installation to make sure they’ll succeed.
