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Pepperl+Fuchs Blog

Sending Ultrasonic Sensors to the Scrapyard

Posted by Marcel Ulrich on Tue, Mar 19, 2013

Scrapyards place unique demands on industrial sensors

Scrapyards can be demanding environments. Plumes of dust and dirt, often outdoors, and with materials encompassing every possible shape, size and color—finding industrial sensors capable of surviving the environment, let alone consistently performing in it, is a challenging task.

Scrapyards use ultrasonic sensors

But scrap materials need to be sensed! Controllers need to know when conveyor belts are empty, when scrap bales are present,  or when the level of a scrap bin is filled to the optimum level. And the scrap isn’t the only material requiring sensing. Overhead cranes maneuvering above the scrap piles and containers require noncontact X-Y positional feedback to perform their job.

Here, you can forget optical sensors (i.e., infrared and lasers). Even if they could cope with the wide spectrum of colors and material reflectivity, the ambient dust effectively blinds them. And other sensing technologies such as inductive or magnetic simply don’t possess the proper range or sensing field.

So that leaves us with…ultrasonic sensors.

Using the propagation time of sound to determine an object’s position, ultrasonic sensors are unaffected by varying target colors. And while light beams struggle to pass through airborne contaminates, a well-designed ultrasonic sensor’s evaluation pulse penetrates dust with ease.

An additional inherent benefit of ultrasonics is their large beam angle. By scanning over a wide area, there is rarely a concern with widely deviating measurements due to irregular surface contours.

Sensing distances required in the scrapyard are also conducive to ultrasonic technology, where standard models offer ranges anywhere from a few inches, to 30+ feet.  

Does that mean ultrasonic products are drop-in “miracle workers” for any application? Often times, yes. But scrap processes are notoriously noisy, so acoustic interference and extreme ambient noise can be problematic. And the nature of scrap is that it can be absolutely any material and form, so when “the planets align,” the right confluence of material or shape can potentially deflect or absorb evaluation pulses. Rather than insurmountable deal-breakers, such issues are usually nuisances that can be overcome once identified.

In many cases, such as monitoring scrap on a conveyor, a simple angling or raising/lowering of the sensor (as opposed to direct overhead mounting) is all that is required to smooth-out an unstable situation.

If simple orientation tweaks don’t do the trick, many of today’s ultrasonics feature filtering algorithms and alternate detection modes to customize sensors to a specific application or environment. Sensing beams can be widened or narrowed depending upon a container's dimension. And when multiple units are mounted within close proximity, they can be synchronized to eliminate the possibility of cross-talk. All this advanced functionality is provided as “standard” with many of today’s microprocessor-controlled models and most suppliers provide free configuration software on their websites.

If you are looking to monitor scrap processes, whether the requirements are simple high/low, present/absent situations or continuous analog level and position feedback, there’s a good chance a standard ultrasonic sensor can do the job. Searching the web for suppliers and contacting an ultrasonic applications engineer with questions will ensure the best product for the job, and a fast, reliable installation.

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Topics: Applications, Ultrasonic Sensors

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