CAPACITIVE POSITION SENSOR AND SENSING METHODOLOGY
First Claim
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1. A capacitive position sensor comprising:
- a fixed electrode support structure comprising a fixed electrode connected to a signal conductor and an additional conductor, said fixed electrode being electrically isolated from said additional conductor; and
a movable electrode, said movable electrode positioned to move in direct proportion to the movement of a reciprocating member;
wherein said additional conductor is driven at a potential which is the same as that of said fixed electrode; and
wherein said fixed electrode and said movable electrode are cylindrical in shape; and
wherein the position sensor is embodied in a free piston Stirling machine including a linear motor that drives the free piston Stirling machine as a Stirling cooler.
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Abstract
A simple and robust variable coaxial capacitive sensor and detection method for monitoring the position of a rapidly reciprocating member such as a piston or displacer in a free piston Stirling engine. The coaxial capacitor of the present invention in a preferred embodiment thereof is configured to modulate capacitive electrode area rather than inter-electrode spacing and as a result a highly linear transfer function can be achieved. Also disclosed are detection methods which derive and process signals in connection with applications which have small sensor capacitance variations while suppressing stray capacitance error.
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Citations
17 Claims
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1. A capacitive position sensor comprising:
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a fixed electrode support structure comprising a fixed electrode connected to a signal conductor and an additional conductor, said fixed electrode being electrically isolated from said additional conductor; and
a movable electrode, said movable electrode positioned to move in direct proportion to the movement of a reciprocating member;
wherein said additional conductor is driven at a potential which is the same as that of said fixed electrode; and
wherein said fixed electrode and said movable electrode are cylindrical in shape; and
wherein the position sensor is embodied in a free piston Stirling machine including a linear motor that drives the free piston Stirling machine as a Stirling cooler. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification