Design and implementation of novel impedance measurement using digital sine-wave oscillator with optimum phase and amplitude

This paper proposed the AC bridge circuit, which can be used to measure unidentified impedance of the system. The AC bridge circuit takes the advance of both a digital sine-wave oscillator, which can promptly adjust the phase of generated signals, and a successive approximation technique, which can profoundly search for the unknown impedance. Therefore, the optimum phase and the suitable amplitude can be immediately determined for the AC bridge circuit. In this study, the unknown impedance were calculated by the AC bridge circuit at these following frequencies 50Hz, 100Hz, 300Hz, 500Hz, 750Hz and 1kHz. When compared with the LCR meter (Agilent 4284A), the result of the measured impedance from the AC bridge circuit has revealed the impedance with estimate 1% average error, which suggested that AC bridge circuit is a perfectly innovation method for identifying the unknown impedance.