592
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
Ultrasonic Sensors,
Sensors for Separate Evaluation
3
.3
Ultrasonic Sensors,
Double Sheet Sensors
3
.4
Ultraschallsensoren,
Ultrasonic Sensor Accessories
3
.5
Germany: +49 621 776-4411
Consider the General Notes on the Information in the Pepperl+Fuchs Product Catalogs
Pepperl+Fuchs Group
fa-info@de.pepperl-fuchs.com
USA: +1 330 486 0001
fa-info@us.pepperl-fuchs.com
Singapore: +65 6779 9091
fa-info@sg.pepperl-fuchs.com
Copyright Pepperl+Fuchs
Fundamentals of Ultrasonic Detection
Physics and technology of ultrasonic sensors
Sound with a frequency higher than approx. 16 kHz cannot be detected
by the human ear–this is referred to as ultrasound. Like sound in the au-
dible frequency range, it propagates at a speed of around 344m/s in the
air.The distance of an object can thus be accurately determined by evalu-
ating the known speed of sound and the measured sound travel time.
Ultrasonic sensors are ideal for consistent object detection, even in harsh
and problematic conditions. Objects made from different materials and
with different shapes, colors, or consistencies are reliably detected.
Pepperl+Fuchs ultrasonic sensors incorporate a piezoelectric converter
as the sonic emitter and receiver. A patented decoupling layer made from
a special plastic is used to couple the ultrasonic waves in the surround-
ing air.
Ultrasonic sensors are available with switching and/or analog outputs.
Depending on the model, different output functions are available.
Transducer
Decoupling
layer
Integral skin foam
Piezoceramic
Blind zone
The ultrasonic converter transmits a burst of sound and converts the
pulse echo into electric voltage.The integrated microcontroller calculates
the distance of the object based upon the echo travel time and speed of
sound. The transmission period and delay period of the ultrasonic con-
verter result in a blind zone in which the ultrasonic sensor is not able to
detect any objects.
Attenuation
time
Echo propagation time 2
τ
Emitter pulse
Echo
U
t
0
t
1
∆
t
t
Detection range
The active area of the ultrasonic sensor is known as the detection range
and is limited by the shortest and longest operating distance.The longest
operating distance is included in the model number.
The ultrasonic sensor detects objects within its detection range, regard-
less of whether they approach axially or move sideways in the sound
beam.
actual
switching distance
switching distance 2
or
upper limit
switching distance 1
or
lower limit
minimum
switching
distance
object
unusable
area
sensing range s d
switching interval
or
measuring interval
maximum
switching
distance
aperture angle
S
Response curves
The following figure illustrates the response areas for two typical objects.
The specified object is detected within this area.
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 upper part of the diagram illustrates the response characteristic on
a level panel measuring 100 mm x 100 mm, the lower part using a rod
with a diameter of 25 mm as the object. Many sensors include a feature
for setting the sound beam width. Both sound beam shapes are shown
in the diagram.
The information in the type designation relates to a normal level panel
measuring 100 mm x 100 mm. This panel must be perpendicular to the
propagation direction of the ultrasonic signal.The sound is reflected away
from upright objects and the echo does not reach the sensor.
Ultrasonic Sensors
