Simplified Digitizing Interface-Architectures for Three-Wire Connected Resistive Sensors: Design and Comprehensive Evaluation

This article describes the design, analysis, and performance verification of simple digitizing interfaces for different types of three-wire resistive sensors. The proposed interface uses an efficient resistance-to-time conversion technique that charges an internal capacitor, between two reference levels, through selected resistive-sensor paths. A simple analog circuit controlled using a digital timing unit realizes the aforementioned technique. This approach is adaptable for various resistive sensor configurations and does not depend on the effect of connecting wire resistances and various other non-ideal parameters (e.g., threshold voltage and pin resistance of microcontroller, offset voltage of comparator, etc.). In addition, the proposed schemes utilize its digital unit (e.g., microcontroller) only for control and timing operations, thus saving on power. The detailed working principle of the proposed interfaces and their error analysis are discussed in the article. Later, performance verification is carried out using simulation as well as emulation studies. These studies clearly show that the presented digitizing interfaces provide linear digital transfer characteristics with maximum nonlinearity of 0.17% and wire resistance compensation. Further, tests are conducted with various remotely located commercial sensors. The outcomes of these studies are reported and compared with the state-of-the-art works.