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US 4,631,519 AGranted
Position measuring apparatus
AssigneeRosemount Engineering Company Limited
InventorJames S. Johnston
Life of this patent
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AssigneeRosemount Engineering Company Limited
InventorJames S. Johnston
Estimating the term…
The relative position of two elements is measured by reading a coded strip 11 fixed to one of the elements. The strip 11 carries code elements in a pseudo-random binary sequence (PRBS) which can be read by a photo-detector array 15. The array 15 and suitable optics if necessary enable enough successive code elements of the PRBS to be read simultaneously to identify the position along the PRBS. The array 15 has several detecting elements for each code element or bit of the PRBS, so that the fine position of transitions or markings of the PRBS can be measured within one PRBS bit length. A comparator 17 compares the output of the array 15 with a portion of the PRBS from a PRBS generator 21. The generated PRBS is serially shifted through a register 18 and a counter 22 stores the number of shifts needed until a match is found. Applications are described in micrometers, pressure sensors, shaft encoders and others.
Position measuring apparatus for determining the relative position of two relatively movable members comprising markings forming regularly spaced code elements on one member extending in the direction of relative movement and defining a pseudo-random binary sequence (PRBS), and detecting means on the other member for sensing said markings, said detecting means being arranged to sense markings in a sufficient number of successive code elements, which number is less than the full length of the PRBS, to define a unique position along the PRBS and thereby give a coarse unambiguous position determination, and said detecting means further being arranged to sense the positions of transitions or edges of markings in a plurality of successive code elements to define a fine position within the length of a code element.
Dependencies are inferred from the claim text.