Algorithm Execution Time and Accuracy of NTC Thermistor-Based Temperature Measurements in Time-Critical Applications

Abstract

This paper addresses the challenges of selecting a suitable method for negative temperature coefficient (NTC) thermistor-based temperature measurement in electronic devices. Although measurement accuracy is of great importance, the temperature calculation time represents an even greater challenge since it is inherently constrained by the control algorithm executed in the microcontroller (MCU). Firstly, a simple signal conditioning circuit with the NTC thermistor is introduced, resulting in a temperature-dependent voltage UT being connected to the MCU’s analog input. Next, a simulation-based approximation of the actual temperature vs. voltage curve is derived, resulting in four temperature notations: for a look-up table principle, polynomial approximation, B equation and Steinhart–Hart equation. Within the simulation results, the expected temperature error of individual methods is calculated, whereas in the experimental part, performed on a DC/DC converter prototype, required prework and available MCU resources are evaluated. In terms of expected accuracy, the look-up table and the Steinhart–Hart equation offer superior results over the polynomial approximation and B equation, especially in the nominal temperature range of the NTC thermistor. However, in terms of required prework, the look-up table is inferior compared to the Steinhart–Hart equation, despite the latter having far more complex mathematical functions, affecting the overall MCU algorithm execution time significantly.

Analog Circuits

“…• Chaos and analog computation [1][2][3][4][5][6][7][8][9]; • Algebraic approaches to the analysis of electrical networks [10]; • AI tools for the design of analog devices [11][12][13][14]; • Industrial applications [15,16].…”

“…The area of analog electronics covers all the conditioning circuits for sensing devices. In [16], Petkovšek et al present in their contribution an analog circuit for thermistorsbased measurements of temperature, which are used, when coupled to microcontroller devices, for conditioning the sensor. The paper is an example of how digital equipment, analog computations and sensors can be integrated together to give accurate low-cost measurement systems.…”