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Ultrasonic Sensors Knowledge (Part 1): Technology and Functionality in a Nutshell


Where are ultrasonic sensors being used?

Ultrasonic sensors detect a wide variety of materials and are not affected by problematic surfaces
Ultrasonic sensors detect a wide variety of materials and are not affected by problematic surfaces

Ultrasonic sensors can be found in many types of industrial automation applications. Whether the fill level of a silo is approaching a critical level, or an aerial work platform on a construction site needs to be safely moved, ultrasonic sensors are versatile sensors that flexibly adapt to a wide range of industrial uses.

The following excerpt from our comprehensive and free downloadable “Technology Guide Ultrasonic Sensors” explains the basic function principles of these handy sensing generalists.

How do ultrasonic sensors gather information?

Highly-developed ultrasonic technology builds the foundation for sensing versatility. The underlying principle is the non-contact detection of objects and the measurement of their distance from the ultrasonic sensor. Depending on the type of sensor, these distances can range from a few centimeters up to 10 meters. The sensor emits ultrasonic pulses which are then reflected by an object.

The generated echo is received by the ultrasonic sensor and converted into an electric signal via the piezoelectric transducer. This is known as the propagation time of sound. The sensor measures the time lag between the emitted ultrasonic pulse and the received echo and calculates the distance to the object using the speed of sound. At room temperature, the speed of sound in air is about 344 m/s.

The ultrasonic sensor measures the time difference between the emitted pulse and received echo

Which materials are detected by ultrasonic sensors?

Pepperl+Fuchs' ultrasonic sensors detect objects made from materials such as wood, metal, or plastic regardless of their shape or color. These objects can be solid, liquid, or in powdered form. The only requirement is that they are able to reflect sound waves back to the sensor. Some objects, however, could reduce the operating range. These include objects with a large, smooth, and slanted surface, or porous targets such as felt, wool, or foam rubber.

Which factors determine the measuring range of ultrasonic sensors?

The sensing range of an ultrasonic sensor depends on the surface properties and angle of the object. The longest sensing ranges are achieved with objects that have a flat surface (standard reflector) positioned at an exact right angle to the sensor axis. Very small objects or objects that partially deflect the sound will reduce the sensing range. Objects with smooth surfaces must be positioned as close as possible to an angle of 90°. Rough surfaces are able to tolerate much larger angular deviations.

Environmental effects must also be considered. The biggest influence on the accuracy of an ultrasonic sensor is the air temperature. Pepperl+Fuchs ultrasonic sensors are equipped with compensation circuitry to eliminate temperature effects on the sensor output. Relative humidity and barometric pressure must also be considered.

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