Microcontroller-Based Interfaces for Quasi-Digital Sensors

Author: F. Reverter, Technical University of Catalonia (UPC Barcelona)

Advisor: Dr. Ramon Pallàs-Areny 

Defense: 10/12/2004

Abstract:

This thesis focuses on direct sensor-to-microcontroller interfaces intended for both IC quasi-digital sensors and classical modulating sensors. The features and limitation  of these interface circuits and design rules and guidelines to improve their performance are described in this work.

This research work contributes theoretical models that explain the effect of power supply interference on the sensor output signal. Commercial quasi-digital sensors have been experimentally analysed and the results agree with the theoretical prediction

The main results are: (i) the measurement of resistor in the range of Pt1000-type temperature sensors yielded a 0.01 % maximal relative error and a 0.10 Ohm resolution, and (ii) the measurement of capacitance from 100 pF to 150 pF (a typical range for capacitive humidity sensors) yelded a 1 % maximal relative error and 50 fF resolution. These valuse are remarkable for the simplicity of the interface circuit. Besides, the experimental results were similar for the different microcontrollers tested. Hence, those results can probably be achieved by other microcontroller, provided the system design follows the guidelines established in this work.

Identifiers: microcontroller-based interfaces, quasi-digital sensors, time-interval measurements, software related effects, direct sensor-to-microcontroller interfaces, power supply interference effect