Magnetic compass having remote digital readout

Claim 2

A digital compass comprising: an optically sensible disk having a plurality of concentric tracks each with a different number of alternately light transmissive and opaque segments thereon defining a plurality of multiple bit Gray coded values around the periphery thereof representative of compass headings; means for mounting said disk rotation about an axis orthogonal to the plane of said disk; one or more magnets provided for rotation with said disk and operative to align said disk with respect to the earth''s magnetic field; a light source for transmitting light through said plurality of tracks; a plurality of photosensors each operative to receive light from a respective track of said disk to produce a corresponding multiple bit digital signal representing a selected code sequence of Gray coded values which provide unambiguous transitions throughout the compass circle; logic circuitry operative in response to the plurality of digital signals provided by said photosensors to provide an output indication of compass position, said circuitry including: means for inverting the most significant bit of said digital signals corresponding to the most significant bit of said Gray code; Gray-to-binary converter means for converting said digital signals having said inverted most significant bit into output signals representing a binary code which is the complement of the binary equivalent of the Gray code sensed from said disk; a unidirectional binary counter receiving the binary output signals from said converter; a decoder coupled to the output of said counter and operative to provide an output signal in response to a predetermined count therefrom; clock means for providing serial clock pulses to increment said counter from the binary number entered therein from said Grayto-binary converter means to a predetermined higher count at which said decoder is respoNsive; said decoder output signal being operative to interrupt the supply of clock pulses by said clock means; and the serial clock pulses provided by said clock means being of a number representative of the compass position sensed from said disk; and output means operative in response to said serial clock pulses for providing an output indication of compass position.

Claim 3

The invention according to claim 1 wherein said clock means includes: a fast clock operative at a predetermined rate for providing said clock pulses to said counter means and to said output means; and a slow clock operative at a predetermined lower rate than the rate of said fast clock and operative to control the sampling rate at which said digital signals are processed.

Claim 4

The invention according to claim 1 wherein said output means includes: output counter means for receiving said clock pulses from said clock means and operative to increment to a corresponding count in response thereto; and display means operative in response to the count of said output counter means to provide a numerical indication of compass heading.

Claim 5

The invention according to claim 3 wherein said output means is remote from said logic circuitry and connected thereto by only a single signal channel operative to transmit said serial clock pulses.

Claim 6

The invention according to claim 1 wherein said digital signals represent a sequence of Gray coded values corresponding to decimal numbers from 76 to 435, the Gray coded equivalent of decimal 76 representing a compass heading of 0*, the Gray coded equivalent of decimal 435 representing a compass heading of 359*.

Claim 7

The invention according to claim 3 wherein: said output counter means is operative to be reset by the first one of said clock pulses from said clock means; and wherein said decoder is operative to provide an output signal to said clock means such that said clock pulses are of a number one more than the number directly representing compass position.

Claim 8

A digital compass comprising: a compass rotor having a sensible code thereon defining a plurality of multiple bit Gray coded values representative of compass headings; means for mounting said rotor for rotation about its axis; one or more magnets provided for rotation with said rotor and operative to align said rotor with respect to the earth''s magnetic field; means for sensing the code on said compass rotor and for providing a plurality of multiple bit digital signals representative of compass heading, said digital signals representing a Gray code version of compass heading; logic circuitry operative in response to said plurality of multiple bit digital signals to provide an output indication of compass position; said circuitry including: means for inverting the most significnt bit of said digital signals corresponding to the most significant bit of said Gray code; converter means for converting said Gray coded digital signals having said inverted most significant bit into binary coded output signals; a unidirectional binary counter receiving the binary coded output signals; decoder means coupled to the output of said unidirectional counter means and operative to provide an output signal in response to a predetermined count therefrom; and clock means for providing serial clock pulses to increment said unidirectional counter means from the binary number entered therein from said converter means to a predetermined higher count at which said decoder is responsive; said decoder output signal being operative to interrupt the supply of clock pulses by said clock means; the serial clock pulses provided by said clock means being of a number representative of the compass position sensed from said compass rotor.

Claim 9

A digital compass comprising: a compass rotor having a sensible code thereon defining a plurality of multiple bit Gray coded values representative of compass headings; means for mounting said rotor for rotation about its axis; one or more magnets provided for rotation with said rotor and operative to align said rotor with respect to the earth''s magnetic field; means for sensing the code on said compass rotor and for providing a plurality of multiple bit digital signals representative of compass heading, said digital signals representing a Gray code version of compass heading; logic circuitry operative in response to said plurality of multiple bit digital signals to provide an output indication of compass position; said circuitry including: means for inverting the most significnt bit of said digital signals corresponding to the most significant bit of said Gray code; converter means for converting said Gray coded digital signals having said inverted most significant bit into binary coded output signals; a unidirectional binary counter receiving the binary coded output signals; decoder means coupled to the output of said unidirectional counter means and operative to provide an output signal in response to a predetermined count therefrom; and clock means for providing serial clock pulses to increment said unidirectional counter means from the binary number entered therein from said converter means to a predetermined higher count at which said decoder is responsive; said decoder output signal being operative to interrupt the supply of clock pulses by said clock means; the serial clock pulses provided by said clock means being of a number representative of the compass position sensed from said compass rotor.

Claim 10

A digital compass comprising: an optically sensible code disk having a plurality of concentric tracks each with a different number of alternately light transmissive and opaque segments thereon defining a plurality of multiple bit Gray coded values around the periphery thereof representative of compass headings; means for mounting said disk for rotation about an axis orthogonal to the plane of said disk; one or more magnets provided for rotation with said disk and operative to align said disk with respect to the earth''s magnetic field; a light source for transmitting light through said plurality of tracks; a plurality of photosensors each operative to receive light from a respective track of said disk to produce a corresponding digital signal representing a selected code sequence of Gray coded values which provide unambiguous transitions throughout the compass circle; logic circuitry operative in response to the plurality of digital signals provided by said photosensors to provide an output indication of compass position, said circuitry including: Gray-to-binary converter means for converting said digital signals into output signals representing a binary code which is the complement of the binary equivalent of the Gray code sensed from said disk; a unidirectional binary counter receiving the binary output signals from said converter; a decoder coupled to the output of said counter and operative to provide an output signal in response to a predetermined count therefrom; clock means for providing serial clock pulses to increment said counter from the binary number entered therein from said Gray-to-binary converter means to a predetermined higher count at which said decoder is responsive; said decoder output signal being operative to interrupt the supply of clock pulses by said clock means; the serial clock pulses provided by said clock means being of a number representative of the compass position sensed from said disk; and output means including at least one output terminal operative in response to said clock pulses for providing an output indication of compass position, said at least one output terminal being disposed at a location remote from said logic circuitry and connected thereto by only a single signal channel operative to transmit said serial clock pulses.

Claim 11

A digital compass comprising: an optically sensible code disk having a plurality of concentric tracks each with a different number of alternately light transmissive and opaque segments thereon defining a plurality of multiple bit Gray coded values around the periphery thereof representative of compass headings; means for mounting said disk for rotation about an axis orthogonal to the plane of said disk; one or more magnets provided for rotation with said disk and operative to align said disk with respect to the earth''s magnetic field; a light source for transmitting light through said plurality of tracks; a plurality of photosensors each operative to receive light from a respective track of said disk to produce a corresponding digital signal representing a selected code sequence of Gray coded values which provide unambiguous transitions throughout the compass circle; logic circuitry operative in response to the plurality of digital signals provided by said photosensors to provide an output indication of compass position, said circuitry including: Gray-to-binary converter means for converting said digital signals into output signals representing a binary code which is the complement of the binary equivalent of the Gray code sensed from said disk; a unidirectional binary counter receiving the binary output signals from said converter; a decoder coupled to the output of said counter and operative to provide an output signal in response to a predetermined count therefrom; clock means for providing serial clock pulses to increment said counter from the binary number entered therein from said Gray-to-binary converter means to a predetermined higher count at which said decoder is responsive; said decoder output signal being operative to interrupt the supply of clock pulses by said clock means; the serial clock pulses provided by said clock means being of a number representative of the compass position sensed from said disk; and output means including at least one output terminal operative in response to said clock pulses for providing an output indication of compass position, said at least one output terminal being disposed at a location remote from said logic circuitry and connected thereto by only a single signal channel operative to transmit said serial clock pulses.

Claim 12

The invention according to claim 8 wherein said converter means includes: a Gray-to-binary converter; and means for inverting the digital signal representing the most significant bit of said Gray code prior to application of said bit to said Gray-to-binary converter.

Claim 13

The invention according to claim 8 wherein said clock means includes: a fast clock operative at a predetermined rate for providing said clock pulses to said counter means and to said output means; and a slow clock operative at a predetermined lower rate than the rate of said fast clock and operative to control the sampling rate at which said digital signals are processed.

Claim 14

The invention according to claim 8 wherein said output means includes: output counter means for receiving said clock pulses from said clock means and operative to increment to a corresponding count in response thereto; and display means operative in response to the count of said output counter means to provide a numerical indication of compass heading.

Claim 15

The invention according to claim 8 wherein said code disk has said Gray codes arranged in a counter-clockwise sequence around said disk and representing a complement of corresponding compass headings.