Distributed control systems are now approximately 50 years old. During that time they have continued to evolve with not only increased control capabilities as a result of new algorithms and processing capacity' but also new forms of I/O including wireless' which is an enabler to improving how we operate and control our facilities. Wireless technology means it is now possible to gather data from more places and in higher concentrations than we have ever been able to do before.
Having more data available doesn't always translate into more information since' as mentioned in the October column' in order to know if the data can or should be used for closed-loop control' we need to know if it is valid. However' intelligent devices often contain hundreds of parameters' so the challenge is now becoming how to select which parameters are valid' when' and more importantly' which ones should be used under what conditions.
Fortunately many control systems are adopting the NAMUR NE107 recommendations that' in addition to indicating if the diagnostic functions are working' also filter the messages themselves into three useful categories (Figure 1). Any of the symbols can be used to represent the states' with the colors in the first column being used with the HMI status near a tag' the center column for black-and-white displays or printed reports' and the final column as the full representation whenever possible.
Additional work is being done by the ISA108 committee Intelligent Device Management to "define standard templates of best practices and work processes for implementation and use of diagnostic and other information provided by intelligent field devices in the process industries." The work of ISA108 and other standards such as ISA18 Alarm Management and ISA101 HMI are providing the impetus and evolution of best practices to the control systems of the future. As we continue to implement these systems and then incorporate the lessons learned while doing so' control systems will evolve to support safer and more reliable manufacturing' as well as production facilities.