Hydraulic control system able to adjust pressure and flow rate to reflect the requirements of one or more consumers at any given time. LS systems can be created using a constant pump as well as a variable pump .
The highest pressure occurring in the system in the pipes to the actuators pLS is fed back to the inlet pressure compensator or the LS controller for the pump and compared with the system pressure p1. The system pressure p1 is controlled via adjustments reflecting the load-sensing pressure difference ΔpLS (control variable) by means of the spring preload (reference variable) at the inlet pressure compensator or pump controller.
The individual pressure compensator, in combination with the proportional directional valve (measuring throttle), forms a continuously adjustable 2-way flow control valve, which means that load-independent flow rate control also applies to consumers whose pressures resulting from the load are lower than for the consumer subjected to the highest load. Since the pressure difference is kept constant at all proportional valves in the LS system, the flow rate to each consumer is proportional to the respective opening cross section for the proportional directional valve.
The circuit with the constant pump is associated with higher energy losses since the flow rate which is not required flows away via the pressure compensator to the tank at the system pressure p1, whereas this element in the circuit with the variable pump is not even made available at this stage as a result of an adjustment to the flow rate for pump Q1.
The individual pressure compensator may be located upstream or downstream of the metering orifice. If the pressure compensator is located downstream, the flow rates to the consumers will always bear some relation to the opening cross section of the metering orifices; if the pressure compensator is located upstream, the consumer subjected to the highest load can remain, providing the total for the flow rates required is greater than the max. delivery flow for the pump.
The LS system with variable pump is a closed centre system: if no flow rate is requested by the system (all proportional directional valves in the centre position), the load pressure signal line to the tank will be relieved and the pump will provide a standby pressure.
A load sensing system with a variable pump will often be subordinate to some form of power limiter with pressure limitation .
Structure of load sensing systems 
Variation in the LS circuit 
Synonym for upstream pressure compensator: load pressure signal system
Synonym for downstream pressure compensator: flow sharing, social flow distribution
