For example, in the case of an orifice flow meter, the differential pressure across the orifice plate is the primary flow element. A turbine meter is equipped with a magnetic pickup that senses the proximity of the turbine blades as the fluid motion causes the turbine to spin; this pickup is the primary flow element for a turbine meter. Diaphragm meters and other positive displacement meters are equipped with a crank shaft, the rotation of which acts as the primary flow element.