Displacement sensor

A cylinder comprising:

• a cylinder body forming a cylindrical hollow chamber for receiving a fluidic medium, the body comprising at least a resistive layer of a substantially uniform thickness, the resistive layer having a first and a second electrical terminal for receiving an alternating voltage;
• a piston fitted to the inside the hollow chamber of the cylinder body and capacitively coupled to the resistive layer, the piston configured to be moved along at least a portion of the longitudinal axis of the cylinder body at a substantially fixed distance from the resistive layer and without contact between the resistive layer and the piston;
• and
• a conducting element electrically connected to the piston for carrying a signal obtained from the piston, the signal having an amplitude proportional to a position of the piston with respect to the first and second electrical terminals of the resistive layer.

A system comprising:

• a signal pickup capacitively coupled to a resistive rod, the signal pickup moveable along an axial length of the resistive rod, the axial length defined by a first electrical terminal and a second electrical terminal of the resistive rod;
• a conductive element electrically coupled to the signal pickup for carrying a voltage signal sensed from the signal pickup to a signal output, the signal having an amplitude proportional to an axial position of the signal pickup with respect to the first and second electrical terminals;
• and
• a conductive shield forming a layer around, and insulated from, the conductive element, the conductive shield extending along a length of the conductive element, the length defined by a first position near the signal pickup and a second position near the signal output.

A system comprising:

• a tubular body forming a tubular hollow chamber for receiving a fluidic medium, the tubular body comprising at least a resistive layer of a substantially uniform thickness, the resistive layer having a first and a second electrical terminal for receiving an alternating voltage;
• means for capacitively coupling to the resistive layer, the means for capacitively coupling fitted to the inside the hollow chamber of the tubular body, the means for capacitively coupling configured to be moved along at least a portion of the longitudinal axis of the tubular body at a substantially fixed distance from the resistive layer and without contact between the resistive layer and the means for capacitively coupling;
• and
• means for carrying a signal obtained from the means for capacitively coupling, the means for carrying the signal electrically connected to the means for capacitively coupling, the signal having an amplitude proportional to a position of the piston with respect to the first and second electrical terminals of the resistive layer.