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.