Accuracy of NTC Thermistor Measurements Using the Sensor to Microcontroller Direct Interface

Portable and wearable sensor systems are usually based on microcontrollers or field programmable gate arrays (FPGAs), where the sensors are measured using an analog-to-digital converter (ADC).An alternative solution, with benefits in terms of cost reduction and lower power consumption, is the sensor-to-microcontroller direct interface (SMDI), a technique where the sensor is measured using the general purpose input output (GPIO) interface present on any microcontroller or FPGA.In this paper, the measurement accuracy of a non-linear temperature sensor (NTC 3950) using SMDI was evaluated by means of LTSpice simulations in the temperature range from -10 C to 80 C. The temperature was estimated using two different models and the results have shown that the most accurate model (Steinhart-Hart model) achieves an average temperature error of 0.078 C.