Sensor-actuator wireless industrial network technologies
When deciding among wireless industrial networking technologies, remember that there are different kinds of wireless. For industrial applications, there are at least four, and two are compared in the graphic shown. (The other two are computer standards like Wi-Fi or Bluetooth and long-distance radio as used with RTUs.)
For actuator/sensor level wireless as compared in the graph, there are two unique application spaces: factory automation and process automation.
Compared to factory automation, wireless networks in process environments are characterized by slower update times and higher power requirements (though used intermittently). Wireless process devices are often powered by batteries or scavenged power (power generated by vibration, for example). Process wireless technologies are transitioning from proprietary to WirelessHART and ISA100.
Wireless factory automation sensors and actuators are often called upon to cycle with millisecond update times. These devices can be powered by the radio waves. Factory automation wireless uses proprietary technology today, but PI (Profibus and Profinet International) is developing a standard that uses the IO-Link protocol wirelessly.
Often wireless process and wireless factory devices are installed where Wi-Fi and Bluetooth are in use. Because the wireless spectrum is a limited resource, attention must be paid to avoid interference. A wireless site survey is a good starting point.
– Carl Henning is deputy director, PI North America, Profibus and Profinet, in North America (formerly PTO); Edited by Mark T. Hoske, content manager CFE Media, Control Engineering, Plant Engineering, and Consulting-Specifying Engineer. He can be reached at firstname.lastname@example.org.