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Smart Sensors Make Material Handling More Reliable and Efficient |
Sophisticated new material handling systems require sensors with onboard intelligence.
Advancing semiconductor technology has allowed microcomputers to become an integral
part of photoelectric and ultrasonic sensors. Overall, these devices significantly
increase the efficiency of palletizers, conveyors, packaging machines, and other
material handlers.
The most realized benefits of smart sensors with onboard intelligence include more
reliable sensing of difficult to detect objects or materials, elimination of background
interference, the ability to adjust the sensing field to the range of the target
object, and the ability to precisely gauge the distance of the target from the sensor.
New sensor technology includes patented "teachable" sensors that can "learn" to
detect objects that were previously impossible to sense. These single pushbutton
sensors utilize an advanced microprocessor that differentiates between 2 received
light levels for the most precise sensitivity adjustment. Point-and-push teaching
is accomplished by pushing the button once with the sensor pointed at the target,
and once with it pointed at the background. The sensor's microprocessor recognizes
low-contrast conditions and expands the sensitivity range before computing the optimal
setting for differentiating between the received light signals.
These sensors can reliably handle
such tough applications as colormark detection
on a continuous web, and sensing clear bottles or wafer cassettes on a moving conveyor
line. For maximum efficiency and convenience, they can be programmed from an external
switch or PLC. Sensing modes include regular and wide-angle diffuse (proximity),
polarized retro reflective, convergent beam, plus glass and plastic fiber optic
models. Smart diagnostics include a green LED indicator that provides an accurate
display of sensing contrast, so the operator knows application stability at a glance.
New fixed-field photoelectric sensors solve the problem of background interference
behind the conveyor by using optical triangulation to sense a target, rather than
relying on reflective surface brightness for a signal return path. These powerful
and precise fixed-field devices, with ranges to 79 in., can sense flat black objects
at exact distances while ignoring highly reflective backgrounds only inches beyond
the cutoff point. Fixed-field technology offers extremely high gain for maintenance-free
operation and the capability to detect both dark and light objects. High-gain circuitry
allows even black plastic or recycled wooden pallets to be detected. These sensors
are vastly more reliable than similar units that require a mechanical range adjustment
that can be thrown off by machine vibration. New ultrasonic sensor technology allows
extremely accurate gauging of distances to resolve object presence within hundredths
of a millimeter. Pushbutton programming enables users to set their own custom sensing
"windows," as compared with inflexible competitive fixed-range units. |
Source:http://www.ien.com/article/smart-sensors-make/528 |
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