Optimized Excitation Signal Source for Efficient Measurement of E/M Impedance

This paper presented an improved algorithm using digitally synthesized excitation signal sources for efficient and accurate measurement of the E/M impedance for structural health monitoring with PWAS (piezoelectric wafer active sensor) transducers. Instead of using a sinusoidal excitation to measure the structural E/M impedance at a single frequency at a time, the digitally synthesized signal sources get the entire structural E/M impedance spectrum immediately at one step through permanently attached PWAS. Digitally synthesized signal source is a time efficient way for E/M impedance spectrum measurement. Firstly, introduction of E/M impedance measurement and the concept of using transfer function to achieve admittance and impedance of PWAS were provided. Secondly, two ways of synthesizing signal sources were discussed. Thirdly, the characteristics and performance of the two signal sources for E/M impedance measurement were compared in simulation and examined by laboratory experiment of measuring a free PWAS impedance spectrum over a wide frequency range (100k~1MHz). Finally, the hardware implementation and measurement precision of the new impedance methods were discussed and concluded.