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ultrasonc waves
Posted Date: 27 Apr 2008 Resource Type: Articles/Knowledge Sharing Category: Education
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Posted By: C.Agnes Member Level: Silver
Rating:  Points: 5
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ULTRASONIC WAVES:
INTRODUCTION:
Ultra means “beyond” and sonic means “sound”. Ultrasonic refers to sound waves that have higher frequency than the human audible range. The sound waves whose frequency lies above the audible frequency of 20 kHz are called Ultrasonic waves.
Ultrasonic sensors can detect small objects at considerable distances. They are able to disregard disturbing backgrounds and functions in fog, dust, dirt or extreme lighting is possible. They can detect any soft and hard materials. No correction factors have to be applied and color does not matter. In our project we are using two ultrasonic sensors. One is ultrasonic transmitter and the other is ultrasonic receiver. They transmit and receive the signal with 40 KHz frequency.
Figure 3: Detection of a car using ultrasonic waves
Figure 4: Detection of a person using ultrasonic waves
ULTRASONIC RANGE FINDING:
An ultrasonic pulse is generated and transmitted in a particular direction. The transmitted pulse is known as Ping. If there is an object in the path of this pulse, part or all of the pulse will be reflected back. The reflected signal is known as Pong. It can be detected through the receiver path. By measuring the time between sending the pulse and detecting the echo, the distance to the object can be determined. I.e. sound travels at a speed of 343 meters per second through air at room temperature. By multiplying the time between pulse and echo (in seconds) with 343 meters per second, we can get twice the distance to the object in meters. Since the sound traveled the distance twice to get to the object and bounces back.
D = 0.5*C*T
D = Distance between the two objects.
C = Velocity of sound.
T = (Tr-Tt)
Tr = Time taken to transmit the signal.
Tt = Time taken to receive the signal.
APPLICATION OF ULTRASONIC WAVES:
? Sensing objects
? Security systems
? Marine applications
? Medical diagnostics
? Nondestructive test.
? Jewelry cleaning
? Plastic welding
? Soldering
? Drilling and cutting
ADVANTAGES OF ULTRASONIC TESTING:
? Low cost and high speed inspection
? Operation is simple and elegant
? Location, nature and size of a defect can be accurately determined.
? Deep seated in metals can be detected.
? Minute flaws can be detected
? Large size specimens can be inspected in a very short duration.
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