Digitally synthesized alternative current sinusoidal waveform for resistive sensor measurements

Abstract

This paper presents a circuit that has the ability to provide a sinusoidal current waveform. The produced waveform is alternative, so it takes positive and negative values. This circuit comprises a microcontroller, a DAC with current output and a fast electronic switch. The sine wave samples are stored in the microcontroller's data memory and are applied to the DAC's digital 8-bit input. The complementary output currents are connected alternatively through the electronic switch to the ground. At pre-calculated timing the microcontroller changes the polarity of the switch, allowing the DAC's output, as alternative current, to flow through the resistive sensor (load), ending through the switch to the ground. Another microcontroller acting as data acquisition chip, at the positive peaks is sampling the voltage across the load. These measurements are transferred through the serial port to a PC, where the resistance is calculated and presented on screen. © 2011 Kavala Institute of Technology.