Ultrasonic Sensors

Sound

As shown in the animation at left, ultrasonic sensors emit sound waves. A sound pattern emerges that is fairly accurately shown in the animation. The sound pattern very quickly gets bigger and bigger as it develops. A good, square target is ideal, but at closer ranges ultrasonics can work with small targets. Note that ultrasonic sensors usually employ a "dead space" of anywhere from a fraction of an inch to a few inches in front of the lens, where the pattern develops.

Switching Output

Ultrasonic sensors are available with a switching output, analog output, or both. With a switching output, ultrasonic sensors are a good answer to long range diffuse photoelectric applications. Rarely do diffuse mode photo eyes have long range capabilities. Ultrasonics are readily available with ranges to 20ft, and specialty ultrasonic sensors are made with even longer ranges. So, ultrasonic sensors are an idea to consider when you've gone through the photoelectric sensing modes without success. In particular, they are good for long-range diffuse mode sensing. There are even opposed mode pairs available with NEMA 6P ratings, making them good for applications such as bottle detection on a conveyor line where washdown is an issue. One of the advantages to ultrasonic sensing is that color is not an issue. Sound waves can bounce off a clear target as easily as they can bounce off any target.

Linear Output

Lasers are excellent devices for short-range sensing of measurement, distance, etc. where extremely precise resolution is required over a short distance. Ultrasonic sensors are another type of analog sensor commonly applied in plants. Lasers generally have very short sensing ranges, whereas ultrasonics are available with sensing ranges from a few inches to a few feet. Plenty of off the shelf ultrasonic sensors offer ranges of 20 ft, and specialty ultrasonic sensors can be obtained with ranges approaching 100 ft. Common applications for analog ultrasonic sensors are level detection and wind/unwind applications.