How it all started

Some years ago, some members of NeSSI (New Sampling/Sensor Initiative) requested an intrinsically safe CAN physical layer in order to connect dedicated sensors in explosive environments. The initiative is sponsored by the Center for Process Analytical Technology (CPAC) at the University of Washington in Seattle (WA). The initiative’s objectives include simplification of tasks and reduction of overall costs associated with engineering, installing and maintaining chemical process analytical systems. The specific objectives are to increase process analytical system reliability through the use of increased automation, shrink the physical size (and energy use) by means of miniaturization, promote the creation and use of industry standards for process analytical systems, and help create the infrastructure needed to support the use of the emerging class of robust and selective microanalytical sensors. Process analytical systems are commonly used by the chemical, oil refining and petrochemical industries to measure and control both chemical composition as well as certain intrinsic physical properties (such as viscosity). To date, NeSSI has served as a forum for the adoption and improvement of an industrial standard, which specifies the use of miniature and modular Lego-like flow components. Circor Tech, Parker-Hannifin, and Swagelok develop and produce such components.
To control those flow components electronically requires a communication system. One of the candidates was CAN. In the beginning, NIST (National Institute of Standards and Technology) located in Washington (DC) organized some meetings and started the specification under the umbrella of IEEE. CiA submitted its CANopen profile for measuring devices and closed-loop controllers (CiA 404). However, the IEEE 1451‑6 standard never comes out of its shoes. After about three years, CiA was requested to take over the development of an intrinsically safe CAN physical layer. Experts from ABB Lewisburg, Circor Tech, Parker, Pepperl + Fuchs, Siemens, Swagelok, Texas Instruments, and Turck participated in the CiA Task Force (“Intrinsically safe CAN”) meetings. The result is the CiA 103 draft standard proposal, which is more a framework than a specification or standard.
This framework provides some basic rules to design CAN physical layer interfaces suitable for intrinsic safe CAN communication. The basic idea is to use 3,3‑V powered CAN transceiver (ISO 11898-2) and CAN micro-controllers. In addition, some circuitry may be necessary to make the interface intrinsic safe (IS) – in particular to implement an isolation barrier between safe and hazardous area. The specification is downloadable from CiA’s members’ website. CiA 103 recommends an 8-pin pico-style connector with a standardized pin-assignment.
IS-CANopen based on CiA 103 has become the NeSSI bus solution envisioned nearly six years ago. The NeSSI consortium has shown that a low-cost transducer bus can be intrinsically safe. CiA device profiles and CANopen conformance testing furnish the infrastructure by which transducer vendors can offer certified plug-and-play multi-channel devices for cost-effective sensor and actuator solutions. CiA also provides a forum for SIGs (special interest groups), such as NeSSI, to adjust the CANopen profiles to meet their specific industry requirements.

First CiA 103 applications

The market for sample-handling systems or process gas chromatographs is a worldwide business. In former times, they were not electronically controlled. The permanent increasing demand to improve sample-handling system leads to highly complex user interfaces. In order to simplify the operating interface, classic text-oriented displays are substituted by graphic user-terminals. The PGC 5000 series by ABB links up to four analyzer ovens to the master control unit, which also provides the graphical user interface. Circor Tech supplies some of the CANopen flow components, which have been exclusively developed for ABB.
In addition Circor Tech provides the DMT series of multi-variable flowmeters, which are able to measure simultaneously upstream and downstream pressure, fluid temperature, and flow rate for liquids or gases. Unlike conventional low-flow meters, such as thermal mass flow devices, the DMT flowmeters provide multi-variable measurement data and control through the CANopen interface. They also offer IP65 and NEMA4x protection. They are the first components of its kind to provide full multi-variable measurement and closed-loop control in a Class 1, Division 1 hazardous area, without requiring explosion-proof conduits and enclosures. Circor Tech use IS-CAN (CiA 103) also for its DVM valve manifold and its CIM76 module, which bridges the link between an IS‑CAN network and a non-IS industrial Ethernet network. The CAN and CANopen interfaces have been developed with the support of ESAcademy, HMS, Ixxat, Peak Systems, Pepperl + Fuchs, Siemens, and Turck as well as others. Several national authorities have already certified the products.
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