As society's product needs change, sensors have had to evolve with them, explains Tina Lockhart, director of engineering for Moore Industries (www.miinet.com). "Today's sensors, integrated with high-integrity transmitter electronics, deliver accuracy, flexibility and performance that was previously not possible," she says.
Sensing technologies each tend to have their own niche applications, explains John Matlack, global business development manager, Macro Sensors (www.macrosensors.com). "LVDTs compete with other position sensing technologies but are selected when ruggedness, resolution, life expectancy and cost are at a premium," he says. "Sensors are used to optimize efficiencies and feedback information to a control system. A production facility needs to measure the products it makes in order to know a good part from a bad one."
Two applications that need non-contact infrared measurement are hot metal detection on an automated rolling mill for any type of metal and boiler temperature within thermal reactors used for sulfur recovery, explains William "Bud" Foran, director of sales at Williamson (www.williamsonir.com). "Without hot metal detection, the drives that move the metal on a rolling mill could not be sequenced properly and, without a continuous measurement and control of a high temperature thermal reactor, process efficiency and the reactor could fail," he says.
"For machine or operational sequences, it is necessary to know that the part is in position and in the correct orientation for the next step of the process," says Gary Frigyes, product marketing manager for photoelectric sensors at Pepperl+Fuchs (www.pepperl-fuchs.us). "Sensors will detect and verify these process steps are followed and accurately completed without guesswork using timers and software." Sensors are a must for error-proofing applications and in applications where machine damage can occur due to part jamming, he explains. "An example would be using a photoelectric sensor to ensure part ejection from the die in a stamping application," says Frigyes.
"In most automated machines, it is critical to know whether a part is in place before the next operation occurs," says Tonty Udelhoven, sensors division director, Turck (www.turck.com). "This is critical to building an error-free subassembly."
A sensor must be matched well for its application, explains Don Martin, president of Lion Precision (www.lionprecision.com). "For measuring displacement there are the sensing requirements of resolution, bandwidth and linearity," he says. "For all sensors there are other environmental requirements of survivability and signal immunity to environmental effects such as EMI and immunity to drift cause by temperature, for example."
Certain requirements exist for communicating the output of the sensor to the controlling or monitoring device, says Martin. "In general, the two options are analog voltage or using a digital protocol," he explains. "To be a true sweet spot, in addition to making a good measurement a sensor must easily integrate into the larger system. If, for example, one is using an industry standard such as cRIO from National Instruments, the system design is simplified and installed cost is reduced if the sensor electronics can be plugged directly into the cRIO chassis. Through the use of transducer electronic data sheets, a smart sensor will be able to communicate additional information such as its sensitivity, measuring range and serial number. The most sophisticated sensors, sometimes referred to as intelligent sensors, will also provide diagnostic information about the sensor, cables or other aspects of the sensor's current state."
For the simplest and most common functions, sensors are extremely abundant in the packaging and conveying industry, where sensing of presence or distance is required, says Lenny Filipkowski, product manager, industrial components, at AutomationDirect (www.automationdirect.com). "As more and more manufacturing processes become automated, sensors are a must in several areas of the machine building industry," he says. "Sensors are needed to detect everything from positioning the end product in the proper place in the machine to detecting the exact location of the tooling, and even detecting humans' presence for critical safety."
Food and beverage customers use powerful disinfectants to keep their manufacturing areas sanitized, says Craig Brockman, marketing manager, presence sensing, at Rockwell Automation (www.rockwellautomation.com). "Their stringent washdown practices neutralize germs and bacteria, but they also can corrode essential equipment like proximity sensors, which safeguard against errors in the process," he says.
The sensor's sweet spot, in terms of applications, is to provide closed-loop feedback from the measurement to help the system deliver optimum performance, says Karmjit Sidhu, vice president of business development for American Sensor Technologies (www.astsensors.com). "Sensors are a must in safety and control in applications such as nuclear power plants, aerospace and transportation," says Sidhu. "In each of the applications, sensors are widely used to shut a process down to avoid costly conflicts."
Ultrasonic sensors are ideal for applications where the combination of a long sensing range and high degree of immunity to ambient factors such as dust, dirt or background light is required, explains Roger Altendorf, product specialist at Balluff (www.balluff.com). "A very typical application where they can be found is in bin-level control for granular substances," he says.