Contribuições à modelagem de sensores termo-resistivos e à medição de radiação solar.

Abstract

This work is a contribution to the characterization of thermo-resistive sensors, and the use of such devices for the measurement of electromagnetic radiation in both, the short and long wavelength region. Their physical and electrical function is determined by the selection of the material, the mechanical lay-out and construction, the interaction and thermo-physical coupling to the environment. The temporal, thermal and electrical response characteristics of theses sensors has been investigated and analyzed by means of a novel methodology, where incremental electrical signals at varying sensor operation levels are applied. Using this approach, it is possible to derive general laws that take into account, among other quantities, the influence of the thermal coupling parameter G, the associated equivalent environmental temperature, the electrical biasing and operation mode. Both, theoretical and experimental considerations revealed the relevance of device nonlinearity, the range and conditions to establish stable sensor operation. W i t h this approach and refined sensor model, that incorporates the solution of the equivalent environmental temperature problem, a new and fast operation mode based on active, controlled feedback is proposed. Apart from a drastically reduced thermal response time, sensor self-calibration is obtained in real time. Experimental results and simulations illustrate the viability of this implementation concept in an embedded systems, based on digital signal processing.