Hydraulic system

A method of operating a hydraulic system including providing

• a hydraulic pump having a pump outlet,
• a main orifice having a main orifice inlet in fluid communication with the pump outlet and a main orifice outlet for supplying pressurized fluid to a service,
• a flow orifice having a flow orifice inlet for sensing a pressure representative of a pressure at the pump outlet and a flow orifice outlet,
• an amplification orifice having an amplification orifice inlet in fluid communication with the flow orifice outlet and an amplification orifice outlet for sensing a pressure representative of a pressure at a service,
• means for generating an output signal representative of a fluid pressure between the flow orifice outlet and the amplification orifice inlet,
• and a pump controller for controlling the hydraulic pump in response to the output signal,
• the flow orifice defining a flow orifice cross section area and
• the amplification orifice defining an amplification orifice cross section area,
• the flow orifice cross section area and the amplification orifice cross section area defining a ratio,
• in which the main orifice is variable and the ratio is variable,
• the method further comprising the steps of operating the system in a first mode so as to define a first mode ratio regime and operating the system in a second mode so as to define a second mode ratio regime,
• so that the first mode ratio regime is different to the second mode ratio regime.