"The elephant in the room" – with this metaphorical idiom, James Powell, Senior Product Specialist Industrial Communications at Siemens, describes in his blog post 'Is Profibus or 4-20mA More Accurate?' in detail the issues with 4 mA ... 20 mA signal quality that everyone is aware of, but nobody wants to talk about.
...and, the goose!
As I was reading John Rezabek's recent article "Can Improved Physical Layer Diagnostics Save Christmas Dinner?", a few thoughts came to mind.
John pointed out that keeping the installation — junction boxes, instrument housings — sealed from moisture ingress is one of the big challenges for both fieldbus and 4 mA … 20 mA installations.
Recently, ControlGlobal.com featured an article by John Rezabek: Why Industrial Couplers Aren't Commodities?