The new theory of measurement technique of space charge distribution in solid dielectrics by electro-acoustic method

The principle of the pulse electroacoustic method used in the measurement of space charge distribution in thick solid dielectrics is reviewed. The overall system can be turned into a linear time-invariant (LTI) system by using the theory of signals and systems. The characteristics of a LTI system are completely determined by its unit impulse response. By considering the role of the reflected waves, the concept of a space-charge-wave function, which is the input of the equivalent LTI system, is proposed. The space-charge-wave function substantially reflects the space charge distribution and the way the stress waves propagate in the sample. The exciting electrical strength and the piezoelectric transducer used together act as the impulse response of the equivalent LTI system, so the waveform of the exciting electrical strength can be generalized to a general waveform. The impulse response of the equivalent LTI system can be obtained easily. By using the fast Fourier transform algorithm to process the signal data obtained, the space charge-wave function can be calculated