Design, Analysis, and Hardware Verification of a Linearized Thermistor-Based Temperature Measurement System

This article brings forward a thermistor-based system for linear estimation of temperature. The proposed system uses a relaxation oscillator-based digitizer and a versatile linearization approach as the core elements in its architecture. This linearizing digitizer for thermistors, aided with ratiometric operations, provides many salient features, including: 1) simplicity of system architecture; 2) direct-digital linear transfer characteristics; 3) compensation against connecting lead resistances; 4) low calibration requirements; and 5) wide range of operation, with better performance with respect to the prior art. The design philosophy of the proposed system is mathematically derived and presented in this article, and the aforementioned features are theoretically established. Furthermore, detailed error analysis, as well as experimental evaluation of the hardware system prototype, is carried out. The developed digitizer is shown to exhibit excellent performance (nonlinearity < 0.09%, relative error < 0.4%, and lead resistance influence < 0.1%) during emulation studies, over a range of 0 °C – 120 °C. Multiple exper- iments with synthesized thermistor characteristics and actual sensor interfacing tests reveal that the maximum output nonlinearity of the developed system is around 0.45%. This article also discusses precision-wise performance and allied use cases of the system, followed by a summary of its comparison study with similar literature.