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User Constructed Sonar Equipment. Presented to PSUBS Convention 2004. Sonar Principles. Basic Concepts Transducers Ping generation Ping reception Post-ping processing Construction and testing. Sonar Principles. Basic Concepts Transducers Ping generation Ping reception

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User constructed sonar equipment l.jpg

User Constructed Sonar Equipment

Presented to

PSUBS Convention 2004


Sonar principles l.jpg
Sonar Principles

  • Basic Concepts

  • Transducers

  • Ping generation

  • Ping reception

  • Post-ping processing

  • Construction and testing


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Sonar Principles

  • Basic Concepts

  • Transducers

  • Ping generation

  • Ping reception

  • Post-ping processing

  • Construction and testing


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Basic Sonar Concepts

  • Generate a signal at some frequency f0

  • Drive an transducer at f0 for a short duration of time generating a “ping”

  • Allow the sound waves generated to propagate outward at the speed of the medium Vm

  • Receive the return echo signal measuring the time of flight from transmission to reception Tf

  • Calculate the distance to target, D = ( Tf · Vm ) / 2


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Speeds of Sound vm0 Degrees Celsius [1]

  • Air 332 m/s 1,090 f/s

  • Fresh water 1,404 m/s 4,610 f/s

  • Sea water 1,440 m/s 4,730 f/s

  • Copper 3,560 m/s 11,680 f/s

  • Iron 5,130 m/s 16,830 f/s


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Sonar Considerations

  • Attenuation of signal by water

  • Spherical radiators

  • Sonar patterns

  • Choice of frequency

  • Sensitivity of receiver

  • Types of transducers


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Attenuation of Sound Through Water [2]

  • Absorption

    Roughly Related to frequency squared

  • Scattering

    Signal scatters use to foreign materials in the water


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Sonar Considerations

  • Attenuation of signal by water

  • Spherical radiators

  • Sonar patterns

  • Choice of frequency

  • Sensitivity of receiver

  • Types of transducers


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Spherical Sound Radiation

  • Sound intensity: I = Power / Area (W/m2)

  • Where area of a sphere = 4pr2

  • Same power through any radius (r) we can imagine, with the source in the center

  • Let PT = Total power through any radius (r)

  • Therefore: I1 = PT / 4pr12 and I2 = PT / 4pr22

  • Combining we have: I1 / r12 = I2 / r22

  • We have: I2 = (r12 / r22) I1 or I2 = (r1/ r2) 2 I1

  • Conclusion: Intensity of sound drops off with the square of the distance (r) from the source


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Sonar Considerations

  • Attenuation of signal by water

  • Spherical radiators

  • Sonar patterns

  • Choice of frequency

  • Sensitivity of receiver

  • Types of transducers


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Sonar Considerations

  • Attenuation of signal by water

  • Spherical radiators

  • Sonar patterns

  • Choice of frequency

  • Sensitivity of receiver

  • Types of transducers


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Sonar Considerations

  • Attenuation of signal by water

  • Spherical radiators

  • Sonar patterns

  • Choice of frequency

  • Sensitivity of receiver

  • Types of transducers


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Sonar Considerations

  • Attenuation of signal by water

  • Spherical radiators

  • Sonar patterns

  • Choice of frequency

  • Sensitivity of receiver

  • Types of transducers


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Sonar Principles

  • Basic Concepts

  • Transducers

  • Ping generation

  • Ping reception

  • Post-ping processing

  • Construction and testing


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Transducers

  • Sonar transducer facts

  • Beam Angle

  • Piezoelectric principles

  • Piezoelectric ceramics

  • Ring and disk transducers elements

  • Piezoelectric modes

  • Typical piezoelectric ceramics

  • Fish finder transducers

  • Available specialty transducers


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Sonar Transducer Facts

  • Transducers convert electrical signals to sound.

  • Transducers convert sound into electrical signals.

  • Most transducers send and receive best at one characteristic frequency f0.

  • Most small sonar transducers are of a piezoelectric form.

  • Most piezoelectric materials for sonar application are ceramics.



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Piezoelectric Principles [3]

Voltage Creates DW

DW Generates Voltage

DW = Change in Thickness


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Piezoelectric CeramicsManufactured in a Variety of Shapes [4]


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Ring and Disk Transducer Elements

Rings

Helps Eliminate Lateral Resonance Modes

Thin Discs

Showing Conductive Coating






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Typical Piezoelectric Ceramics [6]

Channel Industries, Inc.


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Relatively Inexpensive

Encapsulated

Wiring Attached

Wide or Narrow Cone

Locally Available

Little Choice of Resonate Frequencies

Unknown Piezoelectric Material Used

Unknown Electrical Properties of Material

Fish Finder Transducers

Advantages

Disadvantages


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Fish Finder Transducers(Eagle [7])

Transom Mount

Cylinder Thru Hull


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Available Specialty Transducers [7]

Thru Hull Bronze

Thru Hull Plastic

Trolling Motor Mount


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Sonar Principles

  • Basic Concepts

  • Transducers

  • Ping generation

  • Ping reception

  • Post-ping processing

  • Construction and testing






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Ping Driver Circuit

  • Amplifies 192-KHz Signal from Generator and Drives Transducer

  • Generates Drive Only when Ping Enable is Active

  • Multiplexes Sonar Transducers if System Requires




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Sonar Principles

  • Basic Concepts

  • Transducers

  • Ping generation

  • Ping reception

  • Post-ping processing

  • Construction and testing




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Sonar Principles

  • Basic Concepts

  • Transducers

  • Ping generation

  • Ping reception

  • Post-ping processing

  • Construction and testing


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Post-ping Processing Options

  • Sample return analog for feed to computer or microcontroller.

  • Use analog means of measuring time between ping and the breaking of a return threshold level.

  • Be creative with your own methods of monitoring returned amplitude vs time!


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Sonar Principles

  • Basic Concepts

  • Transducers

  • Ping generation

  • Ping reception

  • Post-ping processing

  • Constructionand testing


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Construction and Testing

  • Pressure Housing

  • Electronic assembly

  • Modules

  • Transducer array

  • Testing



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Electronics Assembly

Microcontroller Board


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Modules

Stepper Motor Driver Board


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Modules

Ping Generator


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Modules

192-KHz Receiver


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Transducer Array

Gray Cylinder Contains Stepping Motor Drive System


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Testing

Louisiana State University – Shreveport Pool


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Testing

Yes it is a desktop!


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Bibliography

[1] Sidney Borowitz and Arthur Beiser, “Essentials of Physics”, Addison Wesley Publishing, 1971.

[2] http://www.fas.org/man/dod-101/navy/docs/fun/part08.htm

[3] http://www.Azom.com

[4] Keramos Advanced Piezoelectrics

http://www.piezotechnologies.com/keramos.htm

[5] “Piezoelectric Ceramics”, EDO Corporation.

[6] “Piezoelectric Ceramics”, Channel Industries, Inc.

[7] Lowrance Electronics, Inc.


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