How to Linearize RTD Output

Hi friends, today we will see how to linearize output of RTD. We know that Resistance Temprature Detector (RTD) is widely used temperature sensor. Sometimes we need a linearly changing sensor output for building any digital control system. For example if we have to control a fuel supply to the burner using the temperature reading of the RTD. We can not apply its output (i.e. non linear resistance) to a digital system for controlling the physical parameter. So the question arises how to linearize RTD output.

We know that the output of normally used platinum (Pt100) RTD is non linear. The non linear change in resistance of RTD with respect to temperature is given by the quadratic equation which includes a non linear term. Following circuit gives the output in the linear form. In the circuit, we have used RTD resistance as a feedback resistance of op amp.

Linearization of RTD
Linearization of RTD

In this way we can easily convert nonlinear output of RTD in the linear form. Above circuit is best suited for the temperature range of 0 to 500 degree Celsius.

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