Digital alternative sinusoidal current waveform for virtual resistance measurements

This paper presents a circuit that has the ability to provide a sinusoidal current waveform. This 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 is stored in the microcontroller´s data memory and is applied to the DAC´s digital 8-bit input. The complementary output currents are connected 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 to the load, ending through the switch to the ground. Another microcontroller acting as a 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 as a virtual instrument