1. ULTRASONIC SENSORS Semih Öztürk Mechatronics
Instructor: Associate Prof. İsmail Lazoğlu
26/05/2011

2. OUTLINE Ultrasonic Sensors Characteristics Control Sample Schematic
Applications
Conclusion

3. Ultrasonic Sensors
Ultrasonic Sensors generate high frequency sound waves.
Elavulate the echo
Time interval between sending the signal and
reciving is calculated
to determine the
distance to an object.

4. WORKING PRINCIPLE
Transducer: device that converts energy into ultrasound.
Dog wistle: mechanical energy -> ultrasonic sound waves in the form of air pressure.
Used in the training of dogs and cats
16 – 22 kHz

5. Piezoelectric Transducers
Electrical energy  Sound
Piezoelectric crystals: change size with voltage
Oscillation with applied AC (above 20kHz)

6. Scheme

7. Paralax Ping)))

8. Paralax Ping)))

9. Characteristics of Ultrasound
Inaudible to humans
Sound pressure over 100dB = jet engine
High directivity
Due high frequency  low energy level (kindey stone)
Compressional vibration of matter
Can be used to examine the characteristic of the matter (organ in a body)
Low propagation speed
340m/s in the air.
Low speed signal processing.

10. Directivity Size and shape of the vibrating surface
Frequency at which the trancducer vibrates.
Narrower directivity
Higher frequency
Large size
In electromagnetics, directivity is a figure of merit for an antenna. It measures the power density the antenna radiates in the direction of its strongest emission, versus the power density radiated by an ideal isotropic radiator (which emits uniformly in all directions) radiating the same total power.
Directivity

11. Difference in detection distance with varying frequency
Directivity
Difference in detection distance with varying frequency

12. Prevent False Readings
Temperature
T ̴
0.6 m/sec change for 1 degree Celsius
Reflection
Echo
Liquids or
solids with
large and
hard particles
Angle of reflection = Angle of incidence

13. Echo is more than 3 meters away
that has its reflective surface at a shallow angle so that sound will not be reflected back towards the sensor
is too small to reflect enough sound back to the sensor.

14. Prevent False Readings
Propagation
Dispersion loss of intensity
Intensity of sound decreases with
Absorption
Fluff and loose dirt
In substance in which it travels ( 1-3 dB decrease for 1 m of dry and dust free air)

15. Applications Distance Measurement Ultrasonic Testing
 Sensors with an on or off digital output are available for detecting the presence of objects
Sensors with an analog output which varies proportionally to the sensor to target separation distance
Ultrasonic Testing
Finding flaws in materials (nondestructive testing

16. Applications
Ultrasound (In Medicine)

17. References
  ectDetection/tabid/176/CategoryID/51/List/0 /SortField/0/Level/a/ProductID/92/Default.as px
Munenori Hikita.  Murata's European products
Ultrasonic sensor. In Wikipedia, The Free Encyclopedia. from   e=Ultrasonic_sensor&oldid=