Why ultrasound?
…for transmission measurement (e.g., double sheet detection and web edge control).
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Ultrasound vs. optical sensors
Optical sensors work with light beams that are either reflected or interrupted to detect the position or presence of a material. Typical applications include web edge control for paper, film, or textile webs, as well as double sheet detection in printing machines. Optical systems use measuring principles such as light barriers, laser triangulation, or cameras with image processing.
SECO thinks:
Compared to optical sensors, ultrasound is…
Regardless of material and surface
Ultrasound works reliably with shiny, matte, transparent, or highly reflective materials where optical sensors can have problems.
Resistant to dust and dirt
Optical sensors can be disrupted by dust, oil mist, or paper fibers. Ultrasound works reliably even in harsh industrial environments.
Independent of ambient light
Ultrasound works with sound waves and is independent of lighting conditions. Infrared sensors can provide inaccurate results in the presence of shadows or glare.
Versatile for different types of material
Ultrasound reliably detects double sheets in metal, paper, plastic, or textiles. Optical sensors are usually limited to certain surfaces and transparencies.
Ultrasonic vs. inductive sensors
Inductive sensors operate using electromagnetic fields that are influenced by metallic objects. They detect changes in the field when a metal part approaches or moves away. Typical applications include web edge control for metal webs or position control in sheet metal processing. Inductive sensors are based on measuring principles such as eddy current or coil induction.
SECO thinks:
Compared to inductive sensors, ultrasound is…
Material-independent
Inductive sensors only work with conductive, metallic materials. Ultrasound also detects non-metallic materials (paper, textiles, plastic).
With a wider reach
Ultrasound can bridge large distances. Inductive sensors must be positioned close to the material, which makes integration into wide webs difficult.
Maintenance-free
Ultrasonic sensors operate without contact, have no moving parts, and are maintenance-free. Inductive sensors are susceptible to mechanical influences at small distances.
Independent of surface
Ultrasound works reliably regardless of paintwork, coating, and surface roughness. Inductive sensors can be affected by these factors.
Ultrasonic vs. capacitive sensors
Capacitive sensors operate based on changes in electrical capacity between the sensor and the material surface. This change occurs when the material thickness or distance changes. Typical applications include double sheet detection for paper and cardboard, as well as the detection of films or non-metallic materials. Capacitive systems use measuring principles such as plate capacitors or field changes.
SECO thinks:
Compared to capacitive sensors, ultrasound is…
Resistant to environmental influences
Ultrasound is largely insensitive to humidity, dust or dirt. This can lead to incorrect measurements with capacitive sensors.
Regardless of material type
Ultrasound measures a wide variety of materials. Capacitive sensors are sensitive to material properties and often require readjustment.
Contactless and wear-free
Ultrasonic sensors operate without contact and without moving parts, and are therefore maintenance-free. Capacitive sensors can wear out more quickly due to mechanical proximity.
With a wider reach
Ultrasonic sensors cover greater ranges and are easy to integrate into wide material webs. Capacitive sensors require very short distances.
Ultrasonic vs. mechanical sensors
Mechanical sensors work by making direct physical contact with the material web to determine its position or presence. Typical applications include web edge control in slow processes or with robust materials such as cardboard or sheet metal. Mechanical systems use measuring principles such as levers, rollers, or pressure pins.
SECO thinks:
Compared to mechanical sensors, ultrasound is…
Faster in process speed
Ultrasound is also suitable for fast material webs. Mechanical sensors are imprecise or cannot be used at all at high speeds.
Contactless and maintenance-free
Ultrasound operates without contact and without moving parts, and is therefore maintenance-free. Mechanical sensors require physical contact, which leads to wear and tear.
Gentle on sensitive materials
Mechanical sensors can damage sensitive surfaces. Ultrasound does not affect the material and avoids scratches and deformations.
Regardless of the material
Ultrasound detects a wide variety of materials equally well. Infrared sensors are less reliable with highly absorbent or reflective materials.
Ultrasonic vs. infrared sensors
Infrared sensors work by detecting heat radiation or reflection in the infrared range to detect material surfaces or edges. Typical applications include web edge control for transparent or shiny films and presence detection in packaging processes. Infrared systems use measuring principles such as thermopile detectors or IR light sources with reflection analysis.
SECO thinks:
Compared to infrared sensors, ultrasound is…
Regardless of the material surface
Ultrasound works reliably with shiny and transparent materials, while infrared can be disrupted by reflections or transparency.
Not affected by ambient light
Infrared sensors can deliver faulty signals in the presence of extraneous light or strong illumination. Ultrasound is insensitive to changing light conditions.
Resistant to dust and dirt
Ultrasound works reliably even in dusty, dirty environments. Infrared sensors quickly lose their function when their optics become dirty.
More cost-effective
Ultrasound solutions are significantly more cost-effective. Laser Doppler systems are complex, expensive, and usually only economical for laboratory or special applications.
Sensor comparison: Why ultrasonic sensors are the best choice for transmission measurement
Sensors for double sheet detection and web edge control are crucial for quality assurance and process reliability in film and textile processing and the paper industry. They detect overlaps or control the exact position of material webs, thus preventing production errors and machine damage. The most important technologies include optical, inductive, capacitive, mechanical, infrared-based, and ultrasonic sensors.
Optical sensors work with light reflection or transmitted light. They are fast and precise, but sensitive to contamination, dust, and varying surface colors. They are only suitable to a limited extent for transparent or highly reflective materials.
Inductive sensors react to metallic objects by changing an electromagnetic field. They are robust and insensitive to dust, but are only suitable for conductive materials and cannot be used for paper or plastic.
Capacitive sensors measure changes in the electric field caused by different material thicknesses or properties. They are versatile and can also detect non-metallic materials, but they are sensitive to moisture and require precise calibration.
Mechanical sensors use direct contact, for example via levers or rollers. They are simple and inexpensive, but prone to wear and tear and unsuitable for sensitive or very fast processes.
Infrared sensors detect temperature differences or reflections in the IR range. They are contactless and fast, but can be influenced by ambient temperature and material properties.
Ultrasonic sensors emit sound waves and measure the transmission or reflection. They are non-contact, operate independently of material color and surface texture, and are suitable for double sheet detection as well as web edge control. Their robustness and versatility make ultrasonic sensors the preferred solution in many industrial applications.