Ultrasonic spots gaps between thin sheets

If two sheets have stuck together then the gap between the sheets (however small) is sufficient to attenuate the ultrasonic pulse signal to below a threshold level.

Pepperl+Fuchs has designed an ultrasonic sensor to detect the air gap between two sheets of material.

Feeding two sheets into a machine designed for only one can be a costly, resulting in material wastage, machine jams, or even machine damage.

The UDC double sheet detector use a through-beam arrangement and transmits an ultrasonic pulse to one side of the material.

The signal strength on the other side of the material is then evaluated by the receiver.

A uniform material provides a strong signal at the receiver, but if two sheets have stuck together then the gap between the sheets (however small) is sufficient to attenuate the ultrasonic pulse signal to below a threshold level.

The receiver constantly evaluates the signal strength and an alarm signal can be triggered and the machine can be stopped before the double sheet is fed in.

There are two versions of the sensor.

One version will detect paper, card and thin plastics with a material weight of between 10g/m2 and 2000g/m2.

It is suitable for applications in the printing and binding industry.

The other version has a more powerful transducer and will detect sheet metal, glass, plastics and wood.

The sensors do not require adjustment and will work straight from the box, giving an immediate indication of "no sheet", "one sheet" and "double sheet" states.

Back to top