Chapter 14 - Wireless Field Instruments and Long-range Wireless Data Links

Chapter 14 - Wireless Field Instruments and Long-range Wireless Data Links

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One of the most significant technological innovations in industrial instrumentation of late has been the introduction of radio-based or wireless field instrumentation. Although this technology is simply too immature at the time of this writing (2011) to displace many wired analog and digital systems, the day is undoubtedly coming when wireless instruments will be one of the major technologies of choice for industrial applications.

Wireless field instruments are naturally digital devices, and as such possess all the innate advantages of digital instrumentation: self-diagnostics, multivariable reporting, duplex communication, etc. Furthermore, wireless instruments (at least in theory) lack some of the major limitations of wired digital instruments: slow data rates, low node counts, and energy limitations for classified areas. The single most significant weakness of current wireless field instrument technology appears to be power. With chemical batteries being the only power source, data update times must be limited to a snail’s pace in order to conserve battery life. With the ongoing development of “energy harvesting” devices to locally power wireless field instruments, we may very well see this technology leap ahead of fieldbus and wired-HART instruments.

This chapter focuses on two strands of wireless technology: wireless field instruments (e.g. transmitters, control valves), and long-range wireless data links such as those used in SCADA systems. At the present time, WirelessHART (IEC standard 62591) is the dominant standard for radio-based field instruments, with multiple manufacturers already offering interoperable products. Exciting times, these are!