An axial piston pump having several pistons has a magnetic encoder (5), which is arranged on a swash plate, and a magnetic field sensor, which is arranged in such a way that it faces towards the magnetic encoder (5). The magnetic encoder (5) has at least two permanent magnets (2, 3) and a plate (4) which consists of a ferromagnetic material. The permanent magnets (2, 3) are arranged on the plate (4) in such a way that they each faces a magnetic pole towards the plate (4), and this pole is at least partially covered by the plate (4) in each case.

A variable positive displacement pump actuator system for a variable positive displacement pump can include a supply line configured to provide a supply pressure, a main pump line configured to provide a pump pressure greater than the supply pressure from the variable positive displacement pump, and at least one electro-hydraulic servo valve (EHSV) in fluid communication with the supply line and the main pump line to receive the supply pressure and the pump pressure. The at least one electro-hydraulic servo valve can be configured to output a first regulated pressure and a second regulated pressure. The system can include a first control line in fluid communication with at least one of the at least one EHSV to receive the first controlled pressure, a second control line in fluid communication with at least one of the at least one EHSV to receive the second controlled pressure, a first hydraulic actuator configured to connect to and/or otherwise actuate a lever arm of the variable positive displacement pump, the first hydraulic actuator in fluid communication with the first control line and the supply line to receive the first control pressure and the supply pressure to control a position of the first hydraulic actuator, and a second hydraulic actuator configured to connect to and/or otherwise actuate the lever arm of the variable positive displacement pump, the second hydraulic actuator in fluid communication with the second control line and the supply line to receive the second control pressure and the supply pressure to control a position of the second hydraulic actuator.

An axial piston pump having several pistons has a magnetic encoder (5), which is arranged on a swash plate, and a magnetic field sensor, which is arranged in such a way that it faces towards the magnetic encoder (5). The magnetic encoder (5) has at least two permanent magnets (2, 3) and a plate (4) which consists of a ferromagnetic material. The permanent magnets (2, 3) are arranged on the plate (4) in such a way that they each faces a magnetic pole towards the plate (4), and this pole is at least partially covered by the plate (4) in each case.

A variable displacement hydraulic pump or motor includes: a swash plate; a lever supported by a housing and configured to rotate in conjunction of tilting of the swash plate; and a sensor configured to detect a displacement amount of the lever.

A method for surveillance of an air operated diaphragm pump is provided whereby initially an accelerometer with at least 3 orthogonal accelerometer measuring directions is attached to an air operated diaphragm pump or to a structure directly connected with an air operated diaphragm pump; agitation level of the accelerometer at a frequency rate above a predefined pulse rate of the air operated diaphragm pump is registered, and a base line noise level of the accelerometer agitation level during a period of no pump action is measured and stored, and a pulse rate of the air operated diaphragm pump is determined as the most significant frequency of pulses out of an entire power spectrum calculated from the accelerometer readings, and lastly the most significant frequency of pulses and the duration of registered pulse signals is determined and stored.

An axial piston pump having several pistons has a magnetic encoder (5), which is arranged on a swash plate, and a magnetic field sensor, which is arranged in such a way that it faces towards the magnetic encoder (5). The magnetic encoder (5) has at least two permanent magnets (2, 3) and a plate (4) which consists of a ferromagnetic material. The permanent magnets (2, 3) are arranged on the plate (4) in such a way that they each faces a magnetic pole towards the plate (4), and this pole is at least partially covered by the plate (4) in each case.

A variable displacement hydraulic pump or motor (10) includes: a swash plate (13); a lever (22) supported by a housing (21) and configured to rotate in conjunction of tilting of the swash plate (13); and a sensor (23) configured to detect a displacement amount of the lever (22).

An axial piston pump having several pistons has a magnetic encoder (5), which is arranged on a swash plate, and a magnetic field sensor, which is arranged in such a way that it faces towards the magnetic encoder (5). The magnetic encoder (5) has at least two permanent magnets (2, 3) and a plate (4) which consists of a ferromagnetic material. The permanent magnets (2, 3) are arranged on the plate (4) in such a way that they each faces a magnetic pole towards the plate (4), and this pole is at least partially covered by the plate (4) in each case.