Dynamic Cone Penetrometer. The dynamic cone penetrometer (DCP) is commonly used to determine the stiffness of the base and/or subgrade. As shown in Fig. 3.46, the DCP consists of a 13/16-in (21-mm) diameter, 60° cone mounted on a 5/8-in (16-mm) rod. A 17.6-lb (8-kg) weight is attached to the top of the DCP in such a manner that it can be raised 22.6 in (574 mm) and released while the cone is resting on the base or subgrade.