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.
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