The amplifier circuit function is to increase the sensitivity of the measurement. It is an additional circuit. Without it, the sensor still function.
Function of amplifier circuit:
To increase the Vsensor. This improve the sensitivity of the measurement.
To limits the voltage enter the ADC. The IC 741 does not allow voltage more than the isolated board mount converter. For +-11V, the Vamp(max) is around 10V.
Ra is recommended to be set at 10 kΩ.
Rb is based on the Vsensor and Vadc: Rb = Ra (Vamp(max) / Vsensor(max) – 1)
