Home > Extremely versatile – distance measurement with ultrasonic technology

Extremely versatile – distance measurement with ultrasonic technology

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article image Thanks to its small design, narrow sonic beam, and the colour-independent operating principle, the UC4 miniature sensor even enables the operator to examine test tubes.

Ultrasonic sensors are an ideal solution for distance measurement and object detection in industrial sites. SICK’s portfolio includes universal problem solvers, high-performance space savers and sensors, and application-specific sensors for double layer detection. They also include cubic and cylindrical designs sensing ranges from a few millimetres to several metres, to efficient interfaces for current automation systems. The IO-Link data interface offers additional sensor intelligence and connectivity to the cloud, providing the foundation for successful integration into Industry 4.0 environments.

The user can flexibly and individually adapt the ultrasonic sensors to their respective detection and task. The sensitivity of the sensors – and thus the detection range of their sonic beams – can be adapted infinitely, making it possible to specifically include or exclude objects in the environment. In addition, the sensors can easily display different switching functions and output logics by selecting the “Distance to object”, “Switching window”, or “Object between sensor and background” modes. Even complex tasks are solved consistently thanks to the customisable filter settings. The configuration of the sensor functionality on the computer also provides a clear and simple way of adjusting the sensors individually. Continuous temperature measurement applied to the active sensor surface combined with internal temperature compensation, ensures precise measurement results and the highest level of process quality in all applications.

The versatile application areas of the ultrasonic sensors can be grouped into the following application clusters: level monitoring for liquids and bulk materials, presence and contents inspection, process and quality monitoring, diameter and dimension detection, collision protection, positioning, as well as double layer and adhesive area inspection.

Level monitoring for liquids and bulk materials

Level monitoring is one of the most common distance measuring tasks in the industrial environment. The wide detection range and the large sensing range of the UM30-2 provide the best conditions, for reliably detecting small metal parts with glossy surfaces in vibration conveyors. If the sensor is installed in a depalletising robot, it will also safely detect stacked press parts for vehicle construction. The UM30-2 can be set up quickly and flexibly with the help of its display and the teach-in two buttons. When measuring the level in an oil tray near a machine, the resistant UC12 has the great advantage of being able to detect the level independently of the colour. In this specific application, it is therefore able to replace 1:1 a photoelectric proximity sensor, which is identical in design and connectivity. Due to this compatibility, the user can quickly and effortlessly switch to the ideal operating principle. The UC30, which is compact despite its large sensing range, offers numerous applications in the field of agriculture. The various sensors of the product family have proven to be high-performance detection solutions – despite changing light conditions, different surface properties, and dust formation – in storage silos as well as in the collecting tanks on harvesting vehicles. Prior to further processing of fruit and crops, analogue distance measurement values of the UM18-2 sensors enable the speed of conveyor belts to be controlled according to their load. If food is packaged in blister trays, the space-saving cylindrical sensors of the UM12 product family detect and check the level in the tray before the next packaging step. Thanks to its small design, its narrow sonic beam, and the colour-independent operating principle, the UC4 miniature sensor even enables the operator to examine test tubes.

Detecting the presence of objects and inspecting the contents of totes

The range of applications for presence and contents inspection is particularly wide. The UC4 benefits from its space-saving design and reliable measurement on high-gloss surfaces when detecting silicon blocks in the context of wafer production as well as recognising assembled printed circuit boards in transfer modules. In warehouse and picking technology, the cylindrical UM12 and UM18-2 provide reliable information about the presence and contents of small part totes with speed and accuracy. In addition, the sensors are capable of reliably detecting flat glass plates of different thicknesses and colours, or completely transparent objects such as transparent films, petri dishes, or deep draw trays for packaging food. The UM30-2 product family’s field of application is just as large as its sensing range: its extreme resistance to dirt and demanding ambient conditions is an advantage when detecting the presence of mining trolleys. The UC30 is just as resistant – mounted on a spraying vehicle, it can detect trees in a grove in order to control and optimise the discharge of agricultural pesticides.

Diameter and dimension detection – even in 3D

In most cases, the UM18-2 product family is used in its short variant for diameter control and dimension measurement. The UM18-2 delivers its full potential by combining a small design with a sensing range of more than a metre. When unrolling continuous material such as paper, plastic, textiles, or metals from a coil, it measures the increasing distance between the roller surface and the sensor. The sensors emit a signal in good time, before the material is completely unrolled so that the roll can be changed, thereby minimising the plant downtime. Further tasks for ultrasonic sensors in the processing of web-shaped continuous materials include detecting web breaks and loop control. The ultrasonic sensors are operated in the multiplexing mode for two-dimensional and three-dimensional object measurement. This prevents mutual interference between the sensors and ensures precise and reliable measurement results.

Collision protection from AGVS to aircraft access bridge

A typical task for ultrasonic sensors in mobile applications is the detection of obstacles over a large area. The sensor detects objects and persons so that the vehicle stops or drives around the obstacle. At the same time, the distance measurement continuously monitors the approach of vehicles or forklifts toward transfer points in the stationary conveyor equipment or an automated gangway to the aircraft at the gate. Several UM30, UM18-2, or UC30 sensors can generally be joined to provide the necessary width of the monitoring field. If several ultrasonic sensors from SICK are mounted next to each other, synchronising the sensors prevents their mutual interference and provides reliable measurement results.

Positioning of vehicles and robots

Ultrasonic sensors do not need a reflector and are able to detect, regardless of optical surface properties and ambient conditions. For these reasons, they are the ideal positioning solution in many applications. The sensors of the UM12 and UM18-2 product families are used in mobile automation, for example, on vehicles collecting recyclable material. They are integrated into the automated mechanics of the gripper arms and can move these with millimetre accuracy into the gripping position and the locating points of the recyclable material containers. The sensor’s cylindrical metal housing provides the required high enclosure durability and stability – features which are also important in agricultural applications, where the UM30 is mostly used on the spray and harvesting booms of agricultural vehicles. Ultrasonic sensors also enable fully automated position detection in industrial environments. The non-contact distance measurement ensures reliable positioning processes, for example, in stacking systems, depalletisers, or in the gripper elements of robots.

Process reliability through double layer and adhesive area inspection

When processing metal sheets, print sheets, corrugated boards, carton blanks, self-adhesive films, or chip cards, it is important for the material to be fed in only one layer for reasons of process reliability, quality, and machine availability. However, adhesions, the formation of a vacuum, or adhesive forces can cause layers to be lifted and pulled in. It is the task of the UD18 two-part ultrasonic sensor to carry out reliable double layer detection. It evaluates the material-dependent attenuation of the ultrasonic pulses between the sender and the receiver. For this purpose, the specific attenuation of a material layer is taught in and compared with the actual damping behaviour during the process. In this way, the system detects whether one, two, or no layers are fed in for the process. Selectable attenuation levels facilitate plug-and-play commissioning and provide added flexibility as they can be changed while the plant is operating. The UD18 sensors reliably perform even the most demanding tasks thanks to the optional individual teach-in of materials. The adhesive area inspection uses the same principle for measurement and evaluation. The overlapping area where the end of the web and the starting material of the new roll are glued together dampens the ultrasonic pulses and the adhesive area can be deliberately skipped when the next process step is reached. Whether for double layer detection or adhesive area inspection – the two M18 housings of the sender-receiver system can be mounted and commissioned at variable distances as well as in confined spaces. The area monitoring of the double layer detection is carried out in addition to the output signals with LEDs that are clearly visible on the sensors.

The numerous ultrasonic product families and sensor variants cover a wide range of application fields and industries. In addition, the sensors provide the standard mechanical and electrical connection options and designs available on the market, thus ensuring their interchangeability with sensors with other operating principles, and their compatibility with a wide variety of applications. For the ultrasonic sensors which are equipped with IO-Link, the possibility of communication for configuration and diagnostic purposes opens the door to Industry 4.0 and the Smart Factory.

Ultrasonic sensors – ideal even with coloured, high-gloss, or transparent surfaces

Ultrasound is a sound frequency band beyond the human hearing range – starting at approximately 16 kHz. Sensors based on the ultrasonic operating principle produce short, high-frequency acoustic pulses in this range. These pulses disperse in the air at the speed of sound and can hit objects. Depending on the surface of the object, the pulses can either pass through them, be absorbed, or be reflected by them. Reflection by a surface is the effect that is used for distance measurement in industrial automation. The ultrasonic sensor calculates the distance from the object from the time span between the emission of the acoustic pulses and the reception of the echo signal. Objects and distances are precisely detected – even in the case of coloured, glossy, or transparent surfaces and adverse environmental influences such as dust, dirt, or fog. The integrated temperature compensation and intelligent measured value filters in the ultrasonic sensors from SICK ensure additional process stability. Sensor functions such as synchronisation and multiplexing enable the simultaneous operation of several sensors without mutual interference.

Written by Moritz Gerig, Product Manager for Ultrasonic Sensors at the Identification & Measuring Division of SICK AG, Reute / Germany

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