Abstract: Disclosed is a method and system for unobtrusively measuring physical properties in electrochemical processes occurring in a predefined volume, such as the state of charge in an electrochemical battery. The invention provides for a coil (22) or (42) positioned relative to the predefined volume to minimize the reluctance path between the coil and the electrochemical process, with the winding axis of the coil generally transverse to a surface bounding the predefined volume. In this position, an alternating current is applied to the coil to generate an oscillatory magnetic field. Preferably, the coil includes a core (24) or a backing plate (46) for concentrating the magnetic field in a direction towards the process in the predefined volume. The physical properties are determined based upon a measurement of the electrical complex impedance of the coil, and data correlating the physical properties of the process with the electrical complex impedance of the coil.

Abstract: A variable reluctance saturable core proximity sensor assembly comprising a target and a sensor. The target consists of a magnet having a high field strength, a base plate having a high relative permeability, and a nonmagnetic metal housing surrounding the magnet and base plate. The sensor consists of a core made from a material having a high relative permeability, a coil surrounding the core and a housing made from a nonmagnetic material surrounding the core and coil. At its distal end of the core is a flux director that intercepts the magnetic field produced by the target. The flux director comprises a plurality of radially extending arms having the same permeability as the core. The flux director has a cross-sectional area selected so that the flux director and core saturate at substantially the same time. The sensor assembly may be used in either a slide-by or head-on mode.

Abstract: Disclosed is an inductive divider sensor that comprises a variable inductor (12) connected in series with a fixed inductor (16) between a source of AC voltage and ground. A target element (18) is moved by an object whose position is to be sensed along an axis that extends through the variable inductor thereby changing its impedance. The impedance of the variable inductor is designed to vary such that the voltage taken at a node where the variable inductor and fixed inductor are connected varies according to a predetermined linear output signal.

Abstract: A variable reluctance saturable core proximity sensor assembly comprising a target and a sensor. The target consists of a magnet having a high field strength, a base plate having a high relative permeability, and a non-magnetic metal housing surrounding the magnet and base plate. The sensor consists of a core made from a material having a high relative permeability, a coil surrounding the core and a housing made from a non-magnetic material surrounding the core and coil. The sensor assembly may be used in either a slide-by or head-on mode. Depending upon the configuration of the sensor, the assembly may be used as either a proximity sensor or as a distance sensor.

Abstract: A method and apparatus for sensing the proximity of a target object includes a sensor inductor (L.sub.S, 38) connected in series with an identical reference inductor (L.sub.R, 36) between an input and ground to form an inductive divider network. The sensor inductor is positioned so that its inductance can be varied in response to the proximity of a target object (14, 40) while the inductance of the reference inductor remains constant. Voltage pulses are periodically applied to the divider network from a source (32, 34) and divide across the reference and sensor in accordance with the ratio of the inductances, as varied or not by the presence of the target object. A detector (30) monitors the output of the divider network and provides a target status signal indicative of the proximity of the target object. For low-power operation, the detector circuit and conductive divider network are periodically and momentarily energized in synchronism.