Abstract: Signal generating apparatus comprises a linear series of Hall-effect switches (44) arranged as a plurality of linear arrays in discrete probes (46a, 46b . . . 46n) which are butted end to end. Each switch is closed when in proximity of an actuating magnet (40) movable along the series of switches. In each array a resistance chain (66) is linked at intervals to the switches. Movement of the magnet along an array thereby gives a progressively changing voltage on an output line (5) from the resistance chain as a cumulative signal indicating the position of the magnet. When the magnet moves from one array to the succeeding array after generating a maximum cumulative signal from said one array, that signal is maintained by a latch connection (56) between the two arrays. A cumulative signal representing the magnet position relative to the complete series of switches can thus be generated.

Abstract: A proximity sensing apparatus comprising a capacitor and means for detecting the change in capacitance of the capacitor. The capacitor comprises two capacitive elements that are insulated from each other and are relatively movable. With at least one of the capacitive elements formed from an electrically conducting liquid. The capacitance detecting means operate as a switch in response to the change in capacitance producing a binary output. This output being combined with a series of other outputs from a series of such proximity sensors to form an apparatus to determine position of an object, particularly a liquid level.

Abstract: The effective operating range of an actuator magnet on a position detecting array of solid state hall effect devices improved by the use of flux concentrating elements which direct the flux along the array of sensing devices. The flux concentrating elements comprise a series of rods each avowing a magnetic permeability substantially greater than that of free space, such as soft ferrite, which are placed alignment with and between each sensing device in the array.

Abstract: Signal generating apparatus comprises a linear series of Hall-effect switches (44) arranged as a plurality of linear arrays in discrete probes (46a, 46b . . . 46n) which are butted end to end. Each switch is closed when in proximity of an actuating magnet (40) moveable along the series of switches. In each array a resistance chain (66) is linked at intervals to the switches. Movement of the magnet along an array thereby gives a progressively changing voltage on an output line (50) from the resistance chain as a cumulative signal indicating the position of the magnet. When the magnet moves from one array to the succeeding array after generating a maximum cumulative signal from said one array, that signal is maintained by a latch connection (56) between the two arrays. A cumulative signal representing the magnet position relative to the complete series of switches can thus be generated.