A dual sensor combining dielectric and mechanic principles wasdeveloped. The geometric structure of this sensor has been designedaccording to the ASAE-standard for penetrometer cones, and the sensorcan provide a pair of output signals when inserted into soil. By analyzingboth signals, one can determine the correlation among cone index, soilbulk density, and moisture content. Some preliminary experiments wereperformed in a laboratory environment, and the sensor will be ready foruse in the field in the near future.