Accelerometers

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Accelerometers

• EE 587
• By David Jackson

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Accelerometers

• Types of Accelerometers
• How Surface Micromachined Capacitive
  Accelerometers Work
• Tilt Sensing with Accelerometers
• ADXL202AE

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Types of Accelerometers

• Peizo-film used in AC applications to sense
  motion, sound, temp. and pressure
• Surface Micromachined Capacitive used in DC
  applications to measure tilt, vibration, and
  inertial

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Types of Accelerometers

• Bulk Micromachined Capacitive used in DC
  applications to measure tilt, vibration, and
  inertial
• Electromechanical Servo DC applications to
  measure tilt and inertial
• Piezo-electric AC applications to measure
  vibration and shock

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How It Works Surface Micromachined Capacitive

• Suspended Beam held in place by tethers
• Acceleration in either direction caused movement
  in the beam
• With movement of beam, capacitance between plates
  changes
• The difference is measured and the direction and
  force are determined

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Tilt Sensing

• Accelerometer measures the static gravity field
• Acceleration of 9.8m/s 1g
• Changing the tilt (along the sensitive axis)
  changes acceleration vector

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ADXL202AE

• Operating Temperature -40 to 85C
• Voltage 3.0 to 5.25V
• Current Typical 0.6mA Max 1.0mA
• Output Digital Duty Cycle Modulated or Analog
• Weight less than 1 gram

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References

• http//www.analog.com