The effect of polarization gradient on the frequency response of PVDF polymer transducers

The performance of spot-poled polyvinylidene fluoride (PVDF) membrane hydrophones is examined. It is found that the sensitivity of the hydrophone is markedly dependent on the spatial polarization distribution. Experimental data show there can be a significant difference between the voltage sensitivities measured in the same hydrophone probe depending on which electrode is actually facing the acoustic source. The measurements carried out in the frequency range of 1-20 MHz indicate that this difference, while negligible below 2 MHz, may exceed 1.6 dB at higher frequencies. The theoretical model allowing characteristics of the membrane hydrophone probe to be predicted is developed and experimentally verified. The results indicate that, in critical applications such as the quantitative field measurements or ultrasonic dosimetry, the electrode exposed to the ultrasound source should be carefully identified