WirelessHART Field Devices Ivan Muller, Joao Cesar Netto, and Carlos Eduardo Pereira T oday, the use of wireless industrial ield devices (FDs) is gradually increasing because they are easy to install in dificult places, they ease the design of modular machines, they support mobility, they are less expensive to in- stall and have greater lexibility than wired devices, and they reduce modiication time. In addition, there is no downtime due to maintenance of network cables or connectors. Stud- ies that have been conducted highlight these advantages [1]. Among all of these advantages, the easy installation when compared with wired devices seems to be the most attractive to factory and plant managers. In this paper, the Wireless Highway Addressable Remote Transducer (WirelessHART, WH) Protocol which has evolved from the HART Protocol is presented. It is one of the most prominent industrial wireless mesh network communications protocols for process automation applications. We describe how the protocol copes with RF link dificulties. A case study of the network behavior is given using a previously developed FD with commercial tools and analysis software developed by the authors for use in industry to obtain network data. Introduction Cable and wire links are the simplest and most reliable in- dustrial communication media. Despite the advantage of simplicity, these links are prone to failure due to corrosion, shorts and open circuits, and electromagnetic interference. Also, cable and wire installation demand careful planning and should include localization of ducts, pipes, inspection boxes, and terminals which will be needed for future modiications and maintenance. Fiber optics provides large bandwidth and electromagnetic interference immunity but at a high cost per meter considering the iber and the installation. Repairs are another cost of iber cabling. High cabling cost is a great incen- tive to consider wireless monitoring and control systems, since they can save 20% to 80% of the overall installation cost [2]. Current wireless technology permits battery operated FDs that can easily be installed when an additional process vari- able must be monitored or controlled. On the other hand, robustness and real-time communication requirements are of- ten cited as potential obstacles to the employment of wireless systems in industry. An even bigger impediment is the con- servative mindset that often characterizes the attitude taken towards the adoption of new technologies by industrial au- tomation customers. The tangible connections made of wires and cables lead to conidence for those who work with them. The same cannot be said of the invisible RF connections. Ef- forts are being made to develop reliable wireless network systems for industrial environments [3]. Comparison of Field Devices Communication among radio FDs and controllers usually oc- curs at slow rates, which permit the use of low-rate wireless personal area networks (LR-WPAN). One of the greatest bene- its of RF systems in a factory is easy installation and mobility, which eases the process of repositioning or installing FDs. Cost and time are reduced if no cable installation is needed. Some wireless FDs are even battery operated, so the installation and service requirements are minimal and are limited to the sim- ple infrastructure. Wi-Fi, Bluetooth, ZigBee, ISA and HART are organizations that are making efforts to promote the use of their technol- ogy in industrial applications. However, only FDs that were speciically developed for industry are truly reliable. Wire- less technologies that work ine in home and ofice settings are not necessarily usable in hazardous industrial environments. For instance, ZigBee and Wi-Fi networks use only one chosen channel and, therefore, do not cope effectively with jamming (messages colliding). Other constraints are noticed, especially those related to power consumption. The use of beacons to synchronize the This work has been partly supported by the Brazilian research agencies CNPq, CAPES, and FINEP. The authors also acknowledge the support of Petrobras, the major Brazilian oil company. 20 IEEE Instrumentation & Measurement Magazine December 2011 1094-6969/11/$25.00©2011IEEE