Page 654 - Sensors and Systems - North American Catalog
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Ultrasonic Sensors
3
Ultrasonic Sensors,
Thru-Beam Sensors,
cylindrical
3
.2
Ultrasonic Sensors,
Diffuse Mode Sensors,
cylindrical
3
.1
Ultrasonic Sensors,
Thru-Beam Sensors,
rectangular types
3
.2
Ultrasonic Sensors,
Diffuse Mode Sensors,
rectangular types
3
.1
3
.3
3
.3
Ultraschallsensoren,
Ultrasonic Sensor Accessories
3
.4
Ultrasonic Sensors,
Speciality Models,
cylindrical
Ultrasonic Sensors,
Speciality Models,
rectangular types
652
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Ultrasonic Sensors
Introduction
Synchronization ports connected
The sensors are activated on a cycle over a short period. It should be noted
that with this operation mode, the multiplex time T is extended by a factor
of N, where N indicates the number of sensors operated in multiplex mode.
T multiplex = N x T sensor and f sync = 1/T multiplex
If different types of sensors are used, the total cycle time is equal to the sum
of the cycle times for the individual sensors.
Tmultiplex = T 1 + T 2 +T 3 ... + T N
When using self-synchronization, the sensors operate in multiplex mode.
Synchronized mode
Synchronization ports conneted
external clock
In this operating mode, the synchronization inputs for all sensors are linked
and controlled collectively by an external clock-pulse source. In contrast
to multiplex mode, this does not increase the cycle time. In addition to
monitoring larger areas, synchronization mode is useful in confined spaces
because little space is required between the sensors.
The distances specified below must be taken into account when mounting
sensors opposite one another.
X'
m
X'
m
X'
Detection range
mm
Detection range
mm
to 500
to 2000
to 4000
to 6000
> 2.0
> 8.0
> 16.0
> 25.0
Measuring plates/objects
Ultrasonic sensors can detect solid, liquid, and granulated objects. The
surface properties of the object are important for the evaluation of the echo.
All level and smooth surfaces that are positioned at a right angle to the
beam angle provide an ideal reflection. The measuring plate can have a
maximum angle deviation of +/- 3° to guarantee reliable detection.
3˚
3˚
Material properties such as transparency, color, or surface treatment (shiny
or matte) do not affect detection reliability. Rough surfaces result in diffuse
reflection of a portion of the sound energy, which decreases the detection
range.
However, greater degrees of surface roughness permit greater angle
deviations from the ideal position. The reason for this is the predominately
diffuse reflection of the ultrasonic signal. As a result, filling levels or pouring
cones of coarse-grained materials can be detected at an angular deviation
of up to 45° (at a reduced sensing range)
.
The following objects are suitable for detection:
•
All smooth and solid objects that are aligned at a right angle to the beam
angle
•
All solid objects that are randomly aligned and have a rough surface that
causes a diffuse reflection
•
Liquid surfaces that are angled < 3° from the axis of the beam angle
The following materials are not suitable:
•
Materials that absorb ultrasonic signals such as felt, cotton, wool,
coarse textiles, or foam
•
Materials with temperatures exceeding 100 °C (212 °F)
In these cases, it may be necessary to use to thru-beam operation for such
materials.
Sensors with an adjustable beam angle width
Some series offer an adjustable beam angle that enables the sensors to
operate in confined spaces where objects can spread out laterally into
the beam angle. Such conditions would result in inaccurate switching
characteristics or incorrect readings on sensors without this function.
Adjusting the shape of the beam angle does not affect the maximum
detection range.
0
200
400
600
900
1000
400
300
200
100
0
-100
-200
-300
-400
X
Y
Characteristic response curve
Distance X [mm]
DistanceY [mm]
flat surface 100 mm x 100 mm
round bar, Ø 25 mm
wide sound lobe
narrow sound lobe
The figure above illustrates the characteristic response curve of sensor
UB500-F42 for two different objects:
•
Rod with 25 mm diameter (lower part) and
•
Flat surface measuring 100 mm x 100 mm (upper part).
From this we see that the narrow beam width selection reduces the radial
sensing range. This allows the sensor to be mounted in tight spaces.
