The human finger tip is the most useful tactile sensor part for distinguishing textures. It is possible for fingers to recognize not only surface textures of objects but also the information inside object. "Palpation" in the medical field is an example of techniques utilizing the ability. This study aims to develop a palpation sensor that can obtain both surface and inside information of objects. The palpation sensor that several bimorphic piezoelectric elements are used as sensory receptors is proposed. The output from each element with the position and the velocity information is acquired. Using the position information, it is possible to remove the noise by adjusting time phase of the signals from each bimorphic piezoelectric element. Furthermore, we aim to obtain the information of the sample surface and inside objects by applying additional signal processing to sensor outputs. In this paper, the fundamental characteristics of the prototype sensor system were investigated. First, the signal processing to convert the time history information from the sensor into the positional information was investigated in order to eliminate the influence of mobile speed. Next, the contact condition between sample surface and tip of bimorph piezoelectric element was tested. Finally, electrical cross-talk among bimorphic piezoelectric elements was examined.