For load sensing control the valve in "closed centre valve with load sensing"can be used where the pilot signal is supplied to a valve that operates the pump displacement mechanism. Pressure limiting is usually incorporated so as to limit the maximum pump pressure. In applications where it is required to limit the input torque and power to the pump in order to prevent stalling of the prime mover, the servo system will, for a con­stant pump speed, provide a constant output power.

The circuit shown in Figure 1 controls the displacement to maintain the difference between the pump and the load sense pilot pressures. If the force from the pressure difference on valve B is higher than that set by the spring the pump displacement is reduced by the actuator until it has fallen to the correct value. Valve A is the pressure compensator that senses pump pressure, which, if it is too high, causes the pump displacement to be reduced in order to reduce the pressure.