Abstract: A linear position sensor using time domain reflectometry (TDR) includes a rigid linear guide having a first end and a second end. The linear guide is made of a conductive material. A follower is provided having a central aperture. The follower is positioned with the linear guide passing through the central aperture. The follower is of a material that is influenced by a magnet. A TDR instrument is positioned at one end of the linear guide. The TDR instrument is adapted to send a TDR signal parallel to the linear guide which is directed at the follower. The TDR instrument receives a return signal reflected from the follower which indicates the linear positioning of the follower. At least one magnet is provided which is adapted for mounting on an object. The follower is magnetically attracted to or repulsed by the magnet to such an extent that the follower follows the movement of the magnet, thereby indicating the positioning of the object.

Abstract: A probe for sensing the level of a material or the interface between materials contained in a vessel using Time Domain Reflectometry measurement techniques. The probe comprises a primary conductive rod and at least two secondary conductive rods in spaced relationship with the primary conductive rod for reducing loss of TDR signals propagating through the probe.

Abstract: A probe structure for sensing the level of a liquid or the interface between liquids contained in a vessel using Time Domain Reflectometry measurement technique. The probe comprises a conductive hollow rod and a conductive inner rod in a coaxially spaced relationship inside the hollow rod and extending along the length of the hollow rod. The hollow rod includes perforations along its length to maintain the same liquid level within the probe as that inside the vessel holding the liquid.