Analogue & Digital signals

• Analogue signal


  A signal with strength proportional to the quantity it is representing
• Analogue signals


  • Electrical signals produced by a microphone
  • Position of the pointer on a pressure dial gauge
  • Wave on a CRO
  • Liquid-in-glass thermometers
  • Simple optical fibres
• Digital signal


  Conveys in binary code a number that represents the size of the measured quantity
• Digital signal


  • Digital fibre broadband
• Six Steps of conversion

  1. Selecting a transducer

  2. Connecting the input and reducing interference

  3. Sampling the data

  4. Selecting a sample rate

  5. Choosing the right sensitivity

  6. Outputting the digital information
• Transducer


  Converts physical things into an electrical signal
• Transducer


  • Microphone converts pressure differences in the air from sound waves to electrical signals
• Connecting the input and reducing interference

  • Connect the transducer to an analogue to digital converter
  • Use a screened cable wrapped in a metal mesh, earthed to remove any excess electromagnetic interference
• Sampling the data


  Conversion of the signal to fixed parts (known as a discrete-time signal)
• Sample rate


  Picking the interval on the time axis, too low and the wave will be distorted, typically a higher sampling rate is better
• Analogue vs Digital
• Advantages of Analogue


  • Most signals naturally created are analogue
• Disadvantages of Analogue


  • Analogue signals can reduce in intensity when travelling long distances
  • Analogue signals are easily interfered with
• Advantages of Digital


  • Digital signals travel much faster
  • Digital signals are not easily interfered with or hacked
• Disadvantages of Digital


  • Conversion required for digital signals