Hydraulic valve which creates the difference between the setpoint and actual value and also releases a flow rate proportional to the difference. To this end, the control unit for the valve is connected to the unit specifying the setpoint (e.g. a stepper motor), while the valve housing is connected to the hydraulic output element (cylinder, hydraulic motor). If the setpoint changes, the positions of both valve elements will change with respect to each other until the difference to the actual value is zero again (Figure N 1).
Figure N 1: Following control valve