Introduction: Biased Sensor Bridge
This article explains a biased sensor bridge.
This is a well known biased sensor bridge circuit that you can see in many sensor or instrumentational amplifier specifications/datasheets.
There is another article about a cheaper sensor bridge that does not allow reversing of biasing polarity:
https://hackaday.io/page/9398-biased-sensor-bridge
Non-biased sensor bridge is shown in this link:
Supplies
Parts: 1 kohm/10 kohm or 100 kohm variable resistors/ potentiometers, 330 ohm resistors - 2, 470 uF capacitor.
Tools: Multi-meter.
Optional tools: USB Oscilloscope.
Step 1: Design the Circuit
The two outputs (Vi1 and Vi2) can be connected to inputs of instrumentation amplifier.
Using four variable resistors is the only way you can create a biased sensor bridge to minimise the common mode voltage:
Vcm = (Vi1 + Vi2) / 2
The affect of common mode voltage on output is equal to:
Vcmo = Vcm*Ac
(Where: Ac = Amplifier common mode gain, Vcmo = Common mode voltage output)
The output of the differential amplifier is equal to:
Vo = Vd * Ad + Vcm * Ac
Where:
(Vd = Vi1 - Vi2, Ad = Differential amplifier voltage gain)
The minimum the common mode voltage output:
R1b = R2a
R1a = R2b
Step 2: Simulations
PSpice simulations show biased voltages (200 mV and 450 mV).