A sensor for measuring the position of an object relative to a reference, comprising: a reference component and a displacement component, the displacement component being moveable linearly, or linearly and rotatably, relative to the reference component; and an input port for receiving a pressurized fluid, wherein: the reference and displacement components (6,8) are configured such that a fluidic flow resistance through a predetermined flow path varies in a predetermined way as a function of a linear position, or a linear position and an angular position, of the reference component relative to the displacement component; the reference and displacement components (6,8) are configured such that the object can engage with the sensor in such a way that a linear displacement, or a linear displacement and an angular displacement, of the object relative to the reference causes a corresponding linear displacement, or a linear displacement and an angular displacement, between the reference and displacement components (6,8); the sensor further comprises a detector adapted to obtain a measure of the flow resistance or of a change in the flow resistance and thereby measure a linear position, or a linear position and an angular position, of the object relative to the reference; and the reference and displacement components (6,8) are configured to allow detection of at least three different flow resistances associated respectively with at least three different linear positions, or a combination of at least three different linear and angular positions, of the object relative to the reference, characterized in that: the reference component comprises a cylinder and the displacement component comprises a piston configured to move linearly along an axis of the cylinder, or move linearly along the axis of the cylinder and rotate about the axis of the cylinder, within the cylinder. a reference component and a displacement component, the displacement component being moveable linearly, or linearly and rotatably, relative to the reference component; and an input port for receiving a pressurized fluid, wherein: the reference and displacement components (6,8) are configured such that a fluidic flow resistance through a predetermined flow path varies in a predetermined way as a function of a linear position, or a linear position and an angular position, of the reference component relative to the displacement component; the reference and displacement components (6,8) are configured such that the object can engage with the sensor in such a way that a linear displacement, or a linear displacement and an angular displacement, of the object relative to the reference causes a corresponding linear displacement, or a linear displacement and an angular displacement, between the reference and displacement components (6,8); the sensor further comprises a detector adapted to obtain a measure of the flow resistance or of a change in the flow resistance and thereby measure a linear position, or a linear position and an angular position, of the object relative to the reference; and the reference and displacement components (6,8) are configured to allow detection of at least three different flow resistances associated respectively with at least three different linear positions, or a combination of at least three different linear and angular positions, of the object relative to the reference, the reference and displacement components (6,8) are configured such that a fluidic flow resistance through a predetermined flow path varies in a predetermined way as a function of a linear position, or a linear position and an angular position, of the reference component relative to the displacement component; the reference and displacement components (6,8) are configured such that the object can engage with the sensor in such a way that a linear displacement, or a linear displacement and an angular displacement, of the object relative to the reference causes a corresponding linear displacement, or a linear displacement and an angular displacement, between the reference and displacement components (6,8); the sensor further comprises a detector adapted to obtain a measure of the flow resistance or of a change in the flow resistance and thereby measure a linear position, or a linear position and an angular position, of the object relative to the reference; and the reference and displacement components (6,8) are configured to allow detection of at least three different flow resistances associated respectively with at least three different linear positions, or a combination of at least three different linear and angular positions, of the object relative to the reference,