Geometrical instruments – Indicator of direction of force traversing natural media – Level or plumb – terrestrial gravitation responsive
Patent
1989-02-10
1991-02-12
Will, Thomas B.
Geometrical instruments
Indicator of direction of force traversing natural media
Level or plumb, terrestrial gravitation responsive
33 1PT, 336135, 34087031, 32420715, 32420725, G01C 906
Patent
active
049913018
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to sensors that use variable inductance to provide analogue electrical output data relating to displacement. The displacement may be linear or rotary and may relate to variation in orientation, shaft angle, or linear motion.
Electrical data corresponding to degrees of angular rotation or displacement, together with associated or derived information regarding speed, direction and total turns traversed, are required increasingly for measurement and control purposes in many fields of application to machinery and robotics above and below ground. Such data may also be needed in nominally static applications in order to establish or measure a degree of tilt, or warn operators of moving machinery against hazards arising from excessive tilt. While there are many ways of deriving the information electrically, from simple potentiometers when sliding contacts are acceptable through to precision capacitance-based bi-axial tilt sensors, most analogue devices are limited in the angular range which can be encompassed by a single channel of measurement. All, however, give absolute information, i.e. the data is available at switch-on and under standstill as well as dynamic conditions. Embodiments of the present invention employ a new approach to the problem of designing the most cost-effective methods of deriving angular data. The same principle can be extended to cover linear motion and displacement sensing.
It would be advantageous to provide means for electrical sensing of shaft rotation for 360.degree. or continuous rotation which does not involve electrical connections to both stator and rotor and the conversion of sinusoidal into linear data. For linear displacement using a wound stator (which is a relatively expensive item), it would be advantageous to be able to measure displacement of a relatively movable element over at least the full length of the stator. For linear or rotary displacement, a linear output would be convenient.
According to the present invention there is provided apparatus for use in providing analogue electrical output data relating to displacement comprising first and second members having ferromagnetic cores separated by a constant spacing, said cores defining a magnetic circuit and extending in parallel along a path which intersects the flow path of said magnetic circuit; said first member comprising a wound portion having a winding comprising a plurality of coil portions disposed along said path and connected in series; said plurality of coil portions having a first terminal at one end of the series, a second terminal at the other end of the series, and a central tapping connection; means being provided for supplying a.c. across said terminals to provide magnetic flux around said magnetic circuit; said second member being constructed and arranged so that it has regions of different effective permeability to alternating magnetic flux along its length which affect the inductances of adjacent coil portions of said winding; and wherein at least a portion of the second member is displaceable relative to the first member along said path to effect displacement of the regions of different effective permeability relative to the coil portions; the arrangement being such that, for any relative position, the coil portions of one half of the length of the wound portion have higher inductances than the coil portions of the other half; whereby when a.c. is applied across the terminals and said relative displacement is effected, the voltage at the central tapping connection varies with a substantially linear analogue characteristic for a displacement corresponding to one half of the length of the wound portion, and continued displacement in the same sense for a further half length restores the voltage to its original value in a symmetrical manner.
The winding may have a pair of intermediate tapping connections provided respectively midway between the first terminal and the central tapping, and midway between the central tapping and the second terminal. These can be used to provi
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Radiodetection Limited
Will Thomas B.
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