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Pepperl+Fuchs Blog

Ultrasonic Thru-Beam Sensors: Cutting through the Haze

Posted by Patricia Stafford on Thu, Oct 30, 2014

What are ultrasonic thru-beam sensors?

Ultrasonic thru-beam sensors always come in pairs consisting of a dedicated emitter and a dedicated receiver. The evaluation and switching output electronics are located in the receiver. Using Teach-in or a potentiometer, you can adjust the receiver sensitivity for different distances between the emitter and receiver, or for different object sizes.

Ultrasonic Thru-Beam Sensors

Ultrasonic thru-beam sensors offer an extremely powerful acoustic beam, a large detection range, and compact housing dimensions.  Unlike diffuse and retroreflective models, they do not continuously switch between transmission and reception modes or wait for echo signals. Because their response time is considerably faster, these sensors have very high switching frequencies.

Ultrasonic thru beam sensors emitter and receiver

How do I mount a thru-beam sensor?

Install the emitter and receiver facing one another.

Ultasonic thru-beam sensor operationWhat is the principle behind ultrasonic thru-beam sensors?  How do they work?

Ultrasonic thru-beam sensors work by breaking a beam. When the ultrasound path is interrupted by an object, the switch output activates.

When should I use a thru-beam sensor instead of a photoelectric sensor?

Thru-beam sensors can detect objects of any color or transparency with identical accuracy. Also, because ultrasonic thru-beam sensors can stand up to super dusty and dirty environments, you can use them in places where photoelectric sensors don’t work.

Why should I use thru-beam instead of diffuse mode ultrasonic sensors?

Thru-beam sensors have longer detection ranges and shorter response times than other ultrasonic types. There is minimal to no dead band, so you have the widest possible range. And because they have both a dedicated emitter and a dedicated receiver, you get a lot more power. This “two-is-better-than-one” approach makes thru-beam sensors more able to pierce through dust-filled air than a single diffuse mode sensor.  

For example, say you want to measure the fill level of brake dust in a hopper. It can be a challenging task for a single diffuse mode sensor placed directly over the container, because the sound wave travels through empty air into a small circular area of brake dust. The consistency of this dust is so soft that it may absorb the sound without providing a reliable echo pulse.  

In contrast, if you mount two thru-beam sensors at the same height, one on each side of the container, it’s easier to detect when the brake dust reaches that height. The two sensors teamed up and working together quickly detect the brake dust along the horizontal straight-line path in between. 

What can you do with ultrasonic thru-beam sensors? What kinds of applications are they used in?

Ultrasonic thru beam sensor applications
Bottle counting
Ultrasonic thru-beam sensors can detect even the most transparent materials such as glass or plastic at high speeds.

Double-sheet detection
Ultrasonic thru-beam sensors work using a differential to measure amplitude changes that vary from no sheet to a single sheet to a double sheet.

Splice detection
Ultrasonic thru-beam sensors can detect roll splice tapes with a 600 microsecond response time.

Cement bag filling
Ultrasonic thru-beam sensors thrive in dusty areas.

Corrugated cardboard production
Ultrasonic thru-beam sensors can detect when the outer cardboard surface peels away from the corrugated material inside.

Ultrasonic Sensor Questions?  Get the Quick Select Product Guide

Topics: Ultrasonic Sensors

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