Extremely versatile – distance measurement with ultrasonic technology

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

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

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

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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