Electronic compasses are not new in the art. Both flux gate and Hall effect circuitry have been used to create suitable directional displays for a variety of navigational tasks.
For example, U.S. Pat. No. 4,402,142, issued to Robert C. Dinsmore on Sep. 6, 1983, describes an electronic compass for automobiles utilizing a series of Hall effect sensors. However, the circuits used in that invention have proven to require significant amounts of current, rendering the devices relatively impractical for portable use. Because of the current demands of the Hall effect sensors, amplifiers, Schmitt triggers and display drivers, present Hall effect devices typically consume current at the rate of approximately 200 milliamperes per hour. Extremely large batteries would be necessary to power these devices for extensive periods of time.
The within invention eliminates substantial current consuming portions of the typical Hall effect or flux gate-type compass, adds a "chopper" circuit which effectively shuts the compass electronics off during most of its operating cycle, and a vibration sensing device which shuts off electrical power to the compass when it is motionless for a specified time.