Analog-digital conditioning circuit for RTD temperature measurement

A mixed analog-digital signal analysis of temperature measurement circuits are proposed in this paper. With the combination of both self-balanced Wheatstone bridge (WSB) and direct digital converter (DDC), improved operating range and accuracy is achieved in the measurement of temperature. Three circuits for temperature measurement namely circuit1, circuit2 and circuit3 are proposed here. The three circuits are analyzed to get the best temperature measurement considering improved operating range and accuracy. Simulation results obtained shows that proposed circuit1 and circuit3 have high accuracy (around -0.2% uncertainty), whereas operating range is very less for circuit3. Even though circuit2 has very high operating range, operating range for circuit1 can be improved by proper selection of user-defined Vref value. Based on the analysis, the circuit1 will have higher accuracy and higher operating range with good resolution for slowly varying temperature measurement system.