Prepare wireless protocol.
by Penny Chen, Yokogawa Corporation of America
June 3, 2014

Most engineers would say that the International Society of Automation (ISA) 100 standard covers wireless instrumentation in process plants. This is correct, but it overlooks the comprehensive nature of changing wireless standards and best practices that encompass more than just process plants.

The availability of wireless components for process and discrete manufacturing applications is growing, and with broadening adoption of the Internet of Things (IoT), the number of devices and opportunities for building connections in a plant using Internet protocol (IP) networking is increasing. Choosing a wireless protocol that is “future proof” is important and was a chief concern throughout the ISA100 development cycle.

Sensors & Instrumentation

While many elements make up the larger ISA100 standard (see “The Scope of ISA100” on page 31), one of the first parts completed was ISA100.11a, which covers wireless sensor networks. It was ratified in 2009 and again in 2011 with refinements. In 2011, it was approved by the American National Standards Institute and as IEC62734, it passed as a committee draft for vote in 2013. It will become an International Electrotechnical Commission (IEC) standard.

ISA100.11a is an open-consensus standard. The larger ISA100 committee with 400 members from 250 companies, which represents end users and suppliers in every area of process manufacturing, has been involved at various stages to establish this standard. Creating a standard with a large committee in a deliberative manner ensured the greatest level of participation with the highest possibility of fulfilling the widest range of user cases.

End User Needs

With the development of ISA100.11a, the committee could start with a clean slate to create a wireless networking approach that was not limited by older wired networking protocols. Instead, the committee leveraged more advanced and widely deployed technologies to build a standard that is future-proof. The platform would have to deliver the following:

Reliability—Because the end users cannot see and may not always trust a wireless connection to operate as designed, reliable communications is one of the primary concerns. Process plants often run 24/7 for many years, so high data integrity with low latency and few errors is paramount. ISA100.11a offers robust networking with redundancy where needed. With cyber security becoming more critical, its encryption mechanism maintains safe data and communication channels and protects from outside penetration with sophisticated technologies. Power management techniques that offer highly predictable battery life to minimize maintenance requirements are also considered by providing different field networking topologies that can be mixed and matched as needed. Users can design a flexible network based on application needs, business needs and the character of its sensing devices, among others.

Multi-functionality—While it may begin with instrumentation, ISA100.11a can handle devices with sophisticated data transmission requirements beyond simple sensors. Devices with more complex requirements—such as waveforms or images from analyzers or multi-variable instruments—have no trouble sending larger amounts of data. Where such devices have specialized communication protocols, ISA100.11a can carry that information using tunneling methods to deliver it as intended. Therefore, simultaneously incorporating multiple non-Ethernet network protocols (HART, Foundation fieldbus, Modbus, Profibus, etc.) is not an issue. Whether the facility is brownfield or greenfield, ISA100.11a provides a single wireless communication infrastructure to support all application requirements, currently and in the future.

Multiple Ethernet-based network protocols can also be incorporated. Many different types of devices can access the Internet and many types of applications can run on the Internet. The design principle of ISA100.11a follows the same communication methodology, the International Organization for Standardization/Open Systems Interconnection model (ISO/OSI), as the Internet.

Scalability—Users do not want to launch a networking strategy only to find that they are bumping against deployment limits. A full-scale process plant can have tens of thousands of devices spread throughout square miles. The number of allowable devices, the ability to cover the necessary distance and the amount of data throughout all must be flexible to satisfy the variety of applications from condition monitoring to control in the field.

Easy deployment—A wireless networking system that causes implementation or operational headaches will not last. It must be easy to plan, design and implement—and include many options for functions that are not in existence. Network management using drag-and-drop techniques are standard. Like cellular networks with mobile phones, over-the-air (OTA) programming is a state-of-the-art method for installation, provisioning and device management or updates. ISA100.11a has defined OTA capabilities to ensure easy deployment and provisioning, lifetime management and maintenance.