The HART protocol was first released to the control and instrumentation community back in the late 1980s, when a common digital communications protocol for so called “smart” instruments was envisioned to unify the proprietary efforts of the major instrumentation and control system suppliers.
So began HART’s push to establish and preserve the interoperability among various suppliers’ products that end users had come to expect from their strictly analog instruments—a central mission for the digital age that continues in the work of FieldComm Group. Throughout HART’s various incarnations that were yet to come, the HART protocol maintains what has become the industry’s best example of ecosystem interoperability among different suppliers’ devices and systems.
The original HART protocol still communicates via a digital signal superimposed on the 4-20mA analog instrumentation current loops first standardized in the 1950s. Today, tens of millions of 4-20mA HART instruments constitute the vast majority of instruments installed around the world. Even today, it dominates shipments of new instruments to the global process industries.
So, when the need to connect wireless sensors arose in the 2000s, industry called on HART once again, this time implemented over a wireless mesh network as WirelessHART. But once gathered at a WirelessHART access point, there was a need to transmit move that data onto the plant’s Ethernet-based control and information infrastructure. So was born HART-IP, which was simply the long-trusted HART “application layer” protocol, this time deployed over the Internet Protocol (IP) network-layer on Ethernet.
Enabling digital transformation
The leap to Ethernet has positioned HART to continue to lead the process industry’s ongoing digital transformation in two very important ways.
First, with Ethernet-APL now providing intrinsically safe, two-wire, 10-Mbps field communications at the device level (see companion article on p16), HART-IP is positioned to enable the high-speed, high-power field communications revolution that Ethernet-APL promises, while also preserving the familiar tools and established work processes of instrumentation techs and control engineers worldwide.
