Electrical compass

Claim 2

An electrical compass for a vehicle including sensing means (13) for sensing a magnetic field and providing output signals representative thereof, circuit means coupled to the sensing means for providing display output signals, and display means (35) coupled to the circuit means and responsive to the display output signals for displaying the sensed magnetic field; and compensation means for correcting the sensed and displayed magnetic field for local field interference or other constant factors, the compensation means comprising means for establishing a given display output signal when said sensor (13) is positioned in given alignment with a known magnetic field, and means for providing a correction signal applied to the circuit means to correct the display output signal until the given display output signal occurs.

Claim 3

A compass according to Claim 1 characterised in that said means for establishing the given display output signal comprises a controlled voltage source.

Claim 4

A compass as claimed in any preceding claim in which said sensor (13) is a flux-gate sensor and said controlled voltage source is coupled to said sensor for applying a direct-current correction signal to a winding (11) of said sensor.

Claim 5

A compass as claimed in Claim 3 in which the controlled voltage source includes a variable duty cycle signal generator and integration circuit means - (126, 128, 130) for providing a direct-current voltage having a level proportional to the duty cycle output of said generator.

Claim 6

A compass as claimed in Claim 4 in which said generator is included in a micro-processor circuit (75).

Claim 7

A compass as claimed in Claim 5 and which includes means for selectively storing a display output correction signal when the sensor (13) is aligned in a predetermined true direction heading and for combining the display output signal and said correction signal to provide a true heading display signal.

Claim 8

A compass as claimed in Claim 6 in which said storing means includes switch means coupled to said micro-processor (75) for providing a control signal when actuated by the vehicle operator for storing said correction signal when the vehicle and sensor mounted thereto is aligned in a known true direction.

Claim 9

A compass as claimed in Claim 7 in which said flux-gate sensor (13) has a pair of sensing coils (14, 15) and said circuit means includes a direct current feedback circuit coupled between said micro- processor (75) and said sensing coils to change the output signals of said sensor and thus the display output signals to provide a first reference direction display when said sensor is aligned in a first magnetic reference direction and a second reference display when said sensor is aligned in a second magnetic reference direction.

Claim 10

A compass as claimed in Claim 8 in which said first and second reference directions are orthogonal with respect to each other.

Claim 11

A compass as claimed in any preceding claim in which said display means (35) includes an alpla display (36) for displaying octant compass headings.

Claim 12

A compass as claimed in any of Claims 5 to 10 and which also includes a temperature sensor (90) and means coupling said temperature sensor to said micro- processor (75) for supplying temperature representative signals to said microprocessor which compares said temperature representative signals with stored temperature display signals for providing temperature display output signals in response to said temperature representative signals.

Claim 13

A compass as claimed in Claim 11 in which said stored temperature display signals including a temperature warning signal and said microprocessor provides a temperature warning output signal when input temperature representative signals correspond to said temperature warning signal.

Claim 16

A method as claimed in Claim 13 in which the aligning and storing steps are performed with the vehicle aligned in first one and then the other of two perpendicular directions.

Claim 17

A method as claimed in Claim 13 or Claim 14 in which a corrected display corresponding to an arbitary true heading of the vehicle is produced by applying the correction information signals to the circuit means.

Claim 19

A digital compass and display module (10) for a vehicle comprising: a housing for central mounting to a vehicle roof (12) near the windshield and including a digital display means (35) for providing temperature and compass-heading information; temperature and compass control switches (38, 39, 42, 44) mounted to said housing; and an electrical circuit including temperature sensing means (90) and magnetic field sensing means (13), said circuit coupled to said switch means and to said display means and mounted within said housing for selectively displaying to a vehicle operator temperature and compass heading information.

Claim 20

A digital compass and display module (10) for a vehicle comprising: a housing for central mounting to a vehicle roof (12) near the windshield and including a digital display means (35) for providing temperature and compass-heading information; temperature and compass control switches (38, 39, 42, 44) mounted to said housing; and an electrical circuit including temperature sensing means (90) and magnetic field sensing means (13), said circuit coupled to said switch means and to said display means and mounted within said housing for selectively displaying to a vehicle operator temperature and compass heading information.

Claim 21

A digital compass system for a vehicle comprising: a magnetic field sensor (13); a sensor circuit coupled to said sensor for providing output signals representative of the orientation of said sensor with respect to the earth's magnetic field; a microprocessor (75) and interface circuit means coupling said microprocessor to said sensor circuit for providing display output signals representative of the magnetic direction of orientation of said sensor; display means (35) coupled to said microprocessor (75) for displaying said magnetic direction; and compensation circuit means including operator actuated switch means (42, 44) coupled to said microprocessor for supplying signals to compensate for local magnetic field interference which otherwise causes said sensor to provide output signals which deviate from the actual magnetic orientation of said sensor such that the actual magnetic orientation of said sensor will be displayed.

Claim 22

A digital compass system for a vehicle comprising: a magnetic field sensor (13); a sensor circuit coupled to said sensor for providing output signals representative of the orientation of said sensor with respect to the earth's magnetic field; a microprocessor (75) and interface circuit means coupling said microprocessor to said sensor circuit for providing display output signals representative of the magnetic direction of orientation of said sensor; display means (35) coupled to said microprocessor (75) for displaying said magnetic direction; and compensation circuit means including operator actuated switch means (42, 44) coupled to said microprocessor for supplying signals to compensate for local magnetic field interference which otherwise causes said sensor to provide output signals which deviate from the actual magnetic orientation of said sensor such that the actual magnetic orientation of said sensor will be displayed.

Claim 23

19- A digital electrical compass system for a vehicle comprising: an electrical magnetic field sensor (13) for mounting to a vehicle; a microprocessor (75) coupled to said sensor and including memory circuit means programmed to respond to signals from said sensor to provide display output signals therefrom; a compass calibration switch (42) coupled to said microprocessor for providing a calibration command thereto when actuated to cause said microprocessor to supply a sensor correction signal applied to said sensor (13) to provide a predetermined display output signal in response thereto when the vehicle is aligned in a predetermined magnetic position; and display means (35) coupled to said microprocessor for displaying the vehicle's heading.

Claim 24

19- A digital electrical compass system for a vehicle comprising: an electrical magnetic field sensor (13) for mounting to a vehicle; a microprocessor (75) coupled to said sensor and including memory circuit means programmed to respond to signals from said sensor to provide display output signals therefrom; a compass calibration switch (42) coupled to said microprocessor for providing a calibration command thereto when actuated to cause said microprocessor to supply a sensor correction signal applied to said sensor (13) to provide a predetermined display output signal in response thereto when the vehicle is aligned in a predetermined magnetic position; and display means (35) coupled to said microprocessor for displaying the vehicle's heading.