Time Domain Reflectometry

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Time Domain Reflectometry

• ECE 345 Senior Design Lab

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Time Domain Reflectometry

• Applications
• Theory
• Equipment Setup
• Data Analysis
• Limitations

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Applications

• Transmission Line Length
• Fault Analysis
• Wave Speed
• Physical Properties

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Transmission Line Length

• Good for when you need to know the length of
  inaccessible lines

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Fault Analysis

• Good for deciding where to look for problems

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Wave Speed

• Good for determining performance of lines
  connecting computers and communication equipment

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Physical Properties

• Relative Permittivity of Dielectric (?r)
  ?r (3x108/wave speed)(1/2)
  
• Line Capacitance (C)
  C ?r(1/2)/(Zo
  x 3x108)
• Line Inductance (L)
  L (wave speed2) x C-1

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Theory
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Theory

• V Vo(Zo/(Rg Zo))
• V- (V)(Rload - Zo)/(Rload Zo)
• ? (V)/(V-) (Rload - Zo)/(Rload Zo)
• ? -1 for Rload 0
• ? 1 for Rload ?
• ? 0 for Rload Zo

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Theory

• Bounce Diagram

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Equipment Setup
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Limitations

• Oscilloscope Bandwidth
• Oscilloscope Sampling Rate
• Data Interpretation
• Availability of Literature(cable data)
• Price

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Limitations