Low-cost linear and liquid position transducers

Abstract

Cost-effective methods and apparatus are disclosed for measuring both absolute position and fluctuations using a moving dielectric medium between fixed electrodes. A position sensor according to the invention includes a pair of spaced-apart electrodes, an elongated dielectric that moves between the electrodes, and electrical circuitry interconnected to the electrodes to determine the position of the dielectric relative to the electrodes. To realize a linear position sensor, the electrodes are electrically conductive rods or wires, and the dielectric is also an electrically non-conductive rod or wire. The dielectric may be flexible or stiff, in which case the dielectric and the electrodes are preferably substantially parallel to one another. Alternatively, the spaced-apart electrodes may be concentric tubes, with the dielectric being an electrically non-conductive tube slideably disposed between the electrodes. In different embodiments, the dielectric is a liquid-receiving tube. The tube may be straight, forming part of a level sensor or curved, forming part of a rotation sensor or manometer.