Wheatstone Bridge

The circuit below shows a Wheatstone bridge that converts a change in resistance to a change in differential voltage. The MCP6xxx Op Amp amplifies the voltage difference.

wheatstone-bridge.png

Advantages:

  • Good rejection of common mode noise
  • Ratiometric output (with Analog-to-Digital Converter using VDD as its reference voltage)
  • Simplicity
  • Detection of open sensor due to failure

Disadvantages:

  • Gain is a function of RSEN
  • Need controller and firmware to correct errors
  • Voltage is non-linear with resistance

Sensor Examples:

  • Strain gauge
  • Pressure sensor
  • Magneto-resistive compass

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