Wireless vibration sensors save tens of thousand in equipment operation and maintenance costs

At the heart of wireless sensor networks lie some tiny processors, called dust, motes or sensor nodes. How can you use these tiny processors in your plant?

By Rich Merritt, Senior Technical Editor

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Five or 10 years from now, every piece of rotating machinery, pump, motor, machine tool, and HVAC equipment will arrive in your plant with vibration and machinery health sensors already installed. By then, nanotechnology will have brought the cost of vibration sensors down to about $5 to $10 each, so they will be as pervasive as RS232 and Ethernet ports are today. Every machine will have condition sensors, or you won’t buy them.



When the new machine arrives at your plant, you’ll push a button that will put internal programs in motion to introduce the new machine to your asset-management and CMMS software. From then on, you will be able to monitor the health of the new machine, spot problems before they get serious, and save thousands of dollars in operating and repair expenses.

You won’t have to run a single wire. That’s because the sensors on those machines will automatically become part of a wireless condition-monitoring network.

Farfetched? Hardly. In fact, you can do it yourself today. The wireless vibration sensors cost a lot more than $5 now, but the economics are the same: Wireless sensor networks let you spend hundreds of dollars to save tens of thousands of dollars in equipment and machinery operation and maintenance costs.

Engineers like you are busy installing wireless sensor networks on machinery and equipment already. For example, at Intel’s Ronler Acres semiconductor fabrication plant in Hillsboro, Ore., vibration engineer Mick Flanigan is working with wireless vibration sensors. It’s all still in development, Flanigan says, but the results are promising. “We are monitoring pumps, compressors, and other plant facilities equipment with vibration sensors,” he reports. “Each machine [Figure 1] has from one to 12 vibration sensors, and each sensor reports via wireless to a central Stargate wireless processor, which converts the data from up to 12 sensors and transmits it to a PC that runs Rockwell Automation’s ENSHARE asset management software.”

Motes monitor pumps

Figure 1. At Intel’s semiconductor fab plant in Hillsborough, Ore., each of these high-speed Durco process water pumps has six vibration sensors. The sensors connect via the red wires to a mote, which transmits data via a wireless sensor network. The mote is battery powered, and supplies power to the sensors. Installed cost is about $1,000, compared to about $8,000 for a conventional system.


Engineers like Flanigan will lead the way into the wireless sensor world. Instrumentation and control applications, which stand to gain similar benefits from wireless networks, are less able to adopt such radical technology. Condition-monitoring applications can better accept the risk of an interrupted signal and stand to gain the most from the lower costs, so these sensors are getting their first industrial tryouts in maintenance and system-monitoring applications.


Into the mote

At the heart of wireless sensor networks lie some tiny processors, called dust, motes or sensor nodes. A mote is a tiny $50 processor made by Intel. It’s about the size of your fingernail (Figure 2), is battery operated, communicates via wireless Ethernet, and has a small operating system (TinyOS) and enough memory and hardware capability to perform control and monitoring tasks. Mote technology can put a Web-enabled processor at every sensor and actuator.

Motes think small

Figure 2. The first-generation Mote is a tiny (3x3 cm), battery-operated computer that communicates via wireless. It has a small operating system (TinyOS), and enough memory and hardware capability to perform control and monitoring tasks. The next generation Mote will be half this size.


As long as another mote is within 100 ft. or so, it requires no hardwired network. Hundreds of motes in a plant form a spider web-like mesh or sensor network that provides a virtually unlimited number of pathways to pass information back and forth. Such a network has multiple levels of redundancy because if any mote fails, dozens of others stand ready to move network traffic.

Similar devices are available. Mote is the term used for sensor nodes created by the University of California-Berkeley and its partners, including Crossbow and Intel. TinyNode is another example; it is a sensor/actuator node produced by Embedded Research Solutions, Annapolis, Md. According to Dr. David B. Stewart, EVP/CTO at ERS, instead of TinyOS, TinyNodes use a real-time sensor networking infrastructure called Miniature Software Technology.

Dust is an even smaller mote (Figure 3). Solar-powered versions are being used today to monitor temperature, humidity and other parameters in farm fields, bird nesting grounds, wineries and similar outdoor applications.

The National Institute of Standards and Technology (NIST) calls all this technology “pervasive computing.”

Down and dusty

Figure 3. This solar-powered mote, developed at the University of California-Berkeley in 2001, fits in a cubic millimeter. Called “smart dust,” it has wireless communications and a programmable microprocessor. In one application, researchers fit temperature, humidity, barometric pressure, light intensity, tilt, vibration and magnetic field sensors — plus the mote and a battery — in a 1-cu.-in.-package.

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