Platinum RTD Signal Conditioner with Curvature Correction

The left stage forms a stable precision current source by establishing the reference voltage across a precision resistor, and about half of this current passes through the sensor. The right opamp provides an amplification of the resistance difference between the sensor and a fixed precision resistor to generate a temperature output. A small amount of positive feedback from the output back to the sensor produces a specific parabolic characteristic to compensate for the standard platinum non-linearity.