Semi-automatic compass calibrator apparatus for a vehicle mounted flux gate compass system to cancel out effect of local magnetic disturbances

摘要

Method and apparatus for determining and applying a feedback current to the two sense windings of a vehicle mounted flux gate compass in order to provide a compensating magnetic field to cancel out the effect of local magnetic disturbance field(s) produced by the vehicle. Two zero crossing detectors for each channel respectively associated with the two sense windings indicate when the output from a sense winding passes through a null. This indication is used to enable a sample and hold circuit for the voltage on the opposite coil. During the calibration sequence the vehicle traverses a complete circular path wherein each coil passes through two nulls resulting in two voltages being sampled and held for each coil. The two pairs of voltages are then averaged, which then results in two resultant voltages which are representative of the lateral and longitudinal components with respect to the vehicle of the disturbance field. These voltages are then used to drive a servo loop which stores the voltages indefinitely and in effect forms a non-volatile memory. The stored voltages are then used to drive two current sources which generate compensating feedback currents applied to the sense windings.