PIEZOELECTRIC SENSORS

摘要

A traffic sensor includes piezoelectric sensors having different polarities in different lanes of the roadway so that traffic data for different lanes of a roadway can be detected from the polarity of the received signal(s). The piezoelectric sensors may be formed by splicing oppositely polarized piezoelectric cables or films, by changing the applied electric field during manufacture so that adjacent portions of a piezoelectric cable or film have different polarities, or by applying an electric field of a reversed polarity to respective longitudinal sections of a piezoelectric film. Traffic data from up to eight different lanes of traffic can be detected using only two piezoelectric sensors by providing unique combinations of output polarities for deflections of the piezoelectric sensors in the different lanes. In order to simplify installation, such piezoelectric sensors may be disposed in parallel within the same housing or concentrically within the same cable.