AS THE PUSH to develop faster, more sophisticated and more accurate sensors for industrial applications continues, the contemporary landscape shows that wire-based sensors still are the most popular (and sensible) choice for industrial machine builders, with bus networks used most commonly. This is the state of affairs according to widely varying market reports that nonetheless show industrial sensor technologies and markets slowly moving toward wireless.
Venture Development Corp., which will publish a new sensor market study this year, forecasts annual growth of 5.8% for both wired and wireless sensor types through 2007, with markets for photoelectric sensors comprising 41% of this total.
While competition between wired and wireless gradually has reduced costs, spurred ongoing technical developments, and made the overall market stronger, research shows the basic need remains for dependable devices that inspect with better throughput, higher sampling rates and longer stand-off distances without sacrificing accuracy.
Industry analysts note, however, it’s not likely wireless sensing will be widely adopted simply because it is the latest technology, but will be implemented when it proves to be a reliable, cost-effective tool that solves real problems in industrial applications.
Robert Hoskins, editor/publisher of Broadband Wireless Exchange (Dec. ’05), states, “Most industrial segments have been slow to embrace installation of wireless sensors for three reasons: no visible cost savings; non-use of existing infrastructure; and security concerns.” Hoskins points to manufacturing operations that use fiber-optic wiring that enables them to install wired sensors without much additional cost.
“Because wiring in process control is very detailed, wireless sensors add to the cost, irrespective of the embedded level of intelligence in the system or the sensor itself,” Hoskins says.
The study, Wireless Sensor Networks: Growing Markets, Accelerating Demand, by ON World shows wireless is slowly winning wider acceptance in industrial automation, with the number of wireless sensor networks in use worldwide expected to shoot up from just 246,000 deployed in 2005 to 4.1 million by 2010.
“Until recently, wireless sensor technology was a patchwork of incompatible systems from a variety of vendors,” says Amit Jain, technologies analyst at Frost & Sullivan. “With the evolution of industry standards and the deployment of lightweight wireless networking hardware, wireless technology has come of age.”
Researchers do agree that more industry standards are needed so software vendors have common ways of pulling sensor data from networks containing sensors of varying intelligence made by different vendors.
For now, recent advances made in sensor technology have been limited mostly to enhancements of existing products, as most of this round-up demonstrates. Sensor enclosures for specialty applications, and better protection measures against vibration and high temperatures, continue to evolve. In addition, new developments abound in laser-based measuring systems and smart sensors that incorporate onboard intelligence with new advances in semiconductors, sensor bus technology and miniaturization.
A Break in the Action
SIA inductive-ring sensors activate when a break or inconsistency is detected. Rings are available in diameters 5-100 mm, with LED indication, and NPN or PNP output. An on/off switch enhances performance with small, fast-moving objects by creating a fixed timing impulse. The sensors have an IP65 rating, a plastic housing, and have adjustable sensitivity. ASI; 877/650-5160; www.asi-ez.com
Sensing the Distance
UHZ ultrasonic sensors have a maximum sensing distance of 300 mm with an 18-30 VDC input supply range and PNP or NPN transistor output. FARS sensors are 18-mm, non-metal, tubular, diffuse sensors featuring background suppression. MQ AC diffuse photoelectric sensors fit in a standard 18-mm mounting bracket or mounting hole. All are IP67-rated, and feature electrical protection from short circuit, overvoltage and reverse polarity. AutomationDirect; 800/633-0405; www.automationdirect.com
Setting a World Standard
QS18LD laser-diffuse and QS18LLP laser, retro-reflective sensors use visible Class 1 lasers, tightly collimated sensing beams and extended sensing ranges. Both use standard housings for mounting and application flexibility. Diffuse senses targets up to 300 mm, and retro-reflective delivers sensing to 10 m. It has status LEDs visible from 360° and six connector options. Banner Engineering; 888/373-6767; www.bannerengineering.com
Time to Unwind
Uprox+ sensors have a multi-coil system that replaces wound-coil systems found in conventional ferrite-core, inductive sensors. The sensors have an integrated pre-damping protection function to reduce the metal-free mounting area, allowing traditionally flush-mounted sensors to be recessed by half a turn for increased mechanical protection. All sensors adhere to EN50082-2. Turck; 800/544-PROX; www.turck.com
Protection Where You Need It
MgO thermocouples are constructed with the element compacted in high-temperature magnesium oxide, and protected by an integral metal sheath. Stainless steel and nickel alloy are available as sheath materials for specific application requirements. Diameters range 0.02-.500 in. Termination options range from standard male plugs to screw-cover terminal housings. Durex Industries; 847/639-5600; www.durexindustries.com