Magnetometer direction measuring system requiring no external compass

• US 4,634,978 A
• Filed: 07/19/1983
• Issued: 01/06/1987
• Est. Priority Date: 07/31/1982
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Saura Keiki Seisakusho
• Original Assignee: Kabushiki Kaisha Saura Keiki Seisakusho
• Inventors: Watanabe, Yoshiteru
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): EDMONDS, WARREN
• Application Number:
  US06/515,258
• Time in Patent Office: 1,267 Days
• Field of Search: 324/253-255, 324/259-261, 324/244, 324/246, 324/262, 324/202, 33/361, 33/DIG. 1, 340/870, 340/33, 340/987
• US Class Current: 324/253
• CPC Class Codes: G01C 17/28 Electromagnetic compasses with north seeking magnetic elements and having electric pick-offs G01C17/26
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

A system for accurately measuring the direction in which a magnetometer is to be set has a simple construction and is little affected by iron structures on a hull. The system has a magnetometer which includes an excitation source, a magnetic core, an excitation AC winding and an output winding which are both wound around the magnetic core. The output winding is composed of two series connected coils which are wound around the magnetic core and have an equal number of turns. The measuring system applies an alternating current to the core having an amplitude large enough to saturate the magnetic core, and obtains an output from the output winding corresponding to the angle formed between the geomagnetic field direction and an imaginary line obtained by interconnecting the point of connection of the two coils and the central point of the magnetic core.

Claims

1. A direction measuring system requiring no external compass for measuring a direction of an imaginary line of said system in relation to a geomagnetic field direction and for providing output pulses having equal pulsewidths corresponding thereto comprising:

a magnetometer including a toroidal magnetic core having an AC excitation winding and an output winding wound thereon, wherein said AC excitation winding and said output winding are magnetically coupled by said toroidal magnetic core and wherein said output winding consists of a pair of series connected coils having an equal number of turns arranged so as to have first and second terminals and a third common terminal located between said pair of coils;

a comparator circuit having inputs respectively connected to said first terminal of said output winding and to a reference voltage, wherein said second terminal of said output winding is connected to a reference point which is common to said comparator circuit such that said comparator outputs a first voltage when a voltage across said output winding is greater than said reference voltage and outputs a second voltage when said voltage across said output winding is less than or equal to said reference voltage;

wherein, when an alternating current is supplied to said AC excitation winding with an amplitude which is sufficient to saturate said magnetic core, said comparator circuit outputs pulses having equal pulsewidths which are proportional to an angle between the geomagnetic field direction and an imaginary line drawn between a geometric center of said toroidal magnetic core and said third terminal located between said pair of coils.