Means for indicating direction and a method of determining a direction

• US 4,640,016 A
• Filed: 12/18/1985
• Issued: 02/03/1987
• Est. Priority Date: 12/19/1984
• Status: Expired due to Fees

• Current Assignee: Hannu Purhonen, Risto Tanner
• Original Assignee: Hannu Purhonen, Risto Tanner
• Inventors: Purhonen, Hannu, Tanner, Risto
• Primary Examiner(s): Little, Willis
• Application Number:
  US06/810,913
• Time in Patent Office: 412 Days
• Field of Search: 33/363 Q, 33/363 R, 33/355 R, 33/355 D, 33/361, 33/356
• US Class Current: 33/356
• CPC Class Codes: G01C 17/26 using electric pick-offs for transmission to final indicator, e.g. photocell

Abstract

A remote indication compass, a sensor of which is formed by a magnetic compass (1) and magnetoresistive sensors (2) attached thereto, by means of which sensors the field created by the magnetic compass is measured. The signal of the sensors is analogous as well as cyclic with respect to the angle between the fastening plate of the sensors and the northern direction indicated by the magnetic compass, the length of a cycle being 360°. The angle between the sensors is selected in such a manner that the flat areas of the signals do not coincide.

The sensor signals are amplified and digitalized and scaled. The determination of direction is carried out by comparing the sensor readings to tabulated sensor readings corresponding to different directions or alternatively by comparing the ratio of the sensor readings to the ratios of the tabulated sensor readings. The direction data so obtained is further corrected by means of a deviation correction table created in the operating condition and stored in a memory.

Claims

1. Advice for the determination of direction, comprising:

a turnable indicator having magnetic properties mounted to a frame,

two or more sensors, the operation of which is based on the dependence of the resistance of the magnetic material on a magnetic field exerted thereon, the sensors being secured on said frame and located on a plane parallel with the turning plane of the turnable indicator,

an A/D-converter for converting the sensor values into digital form, the input of said converter being connected to the sensors,

a signal treating processor connected to the output of the A/D-converter, which signal treating processor has in its memory at least one predetermined table, on the basis of which the processor determines a preliminary direction approximation, and a predetermined correction table for correcting the preliminary direction approximation, and

a display for displaying the corrected direction data, said display being connected to the output of the signal treating processor.

2. The device according to claim 1, characterized in that said sensors consist of a bridge coupling formed by magneto-resistive elements.

3. The device according to claim 1 or 2, characterized in that two sensors are provided and that the phase difference therebetween is 90°

.

4. The device according to claim 1 or 2, characterized in that three sensors are provided and the phase difference therebetween is 120°

.

5. The device according to claim 1, characterized in that the turnable indicator is a magnetic needle.

6. A method for the determination of direction using a turnable indicator and two or more sensors secured on a frame and the operation of which is based on the dependence of the resistance of the magnetic material on a magnetic field exerted thereon, said method comprising the steps of:

modifying the signals obtained from the sensors into digital form by means of an A/D-converter,

scaling the sensor readings obtained from the A/D-converter,

comparing the scaled sensor readings directly to reference values corresponding to different directions to obtain a preliminary direction approximation, and

determining the final direction by adding the preliminary direction approximation to a tabulated deflection and deviation value corresponding to the direction in question, said deflection and deviation value being created in the actual operating conditions and stored in a non-volatile memory.

8. The method according to claim 6 or 7, wherein the contents used in the scaling operation are calculated by turning said means around in a special test mode and by comparing the minimum and the maximum of the obtained signal values to desired minimum and maximum values.

7. A method for the determination of direction using a turnable indicator and two or more sensors secured on a frame and the operation of which is based on the dependence of the resistance of the magnetic material on a magnetic field exerted thereon, said method comprising the steps of:

modifying the signals obtained from the sensors into digital form by means of an A/D-converter,

scaling the sensor readings obtained from the A/D-converter,

comparing the ratio of selected sensor readings to stored ratios to obtain a preliminary direction approximation, and

determining the final direction by adding the preliminary direction approximation to a tabulated deflection and deviation value corresponding to the direction in question, said deflection and deviation value being created in the actual operating conditions and stored in a non-volatile memory.