If you’re working in a facility without a great deal of—or any—wireless sensors in place, you might be suspicious about the viability of wireless sensor networks. To help illustrate how ubiquitous wireless sensors have become across industry, following are a few examples of wireless sensor deployments that have become so common that they could be considered textbook application examples.
- Wireless limit switch networks are commonly used to prevent the overflow of liquid storage tanks. Their operation is simple: As the tank fills up, the fluid level forces a change in the position of the limit switch. The wireless limit switch then sends a signal to the pump controller to start pumping out the tank to lower the level. When the fluid level drops to a safe level, the switch then sends a signal to the controller to turn off the pump.
- The safety and security of oil pipelines is largely handled by wireless sensor networks, according to Steve Toteda, vice president and general manager of the wireless business unit at Cooper Industries and chairman of the Wireless Industrial Networking Alliance (WINA). “We're doing a lot of work in Mexico now to monitor and maintain oil pipelines,” he says. “In these applications, there is a hierarchy of networking tools with sensor networks being used with instrumentation on the pipeline itself to capture data and transmit it back to the control system via high-speed backhaul. This combination of technologies—wired, wireless and cellular—has really brought wireless to the forefront because you’re mixing multiple technologies to monitor pipelines in 20-30 km segments. As you do this with several segments, you’re effectively able to monitor hundreds of kilometers of pipelines.
- A major pharmaceutical manufacturer recently decided to instrument all of its R&D equipment, such as incubators and cryofreezers, and connect them to the company’s control systems for 24/7/365 monitoring. Because much of this equipment has casters, it was difficult to wire them, as they need to be moved around. This project is still ongoing, but there are currently nearly 2,000 pieces of equipment equipped with wireless sensors on the company’s R&D campus, which covers an area of about 1.5 km.
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