Abstract: An electronic compass has a compass housing. An electronic magnetic field sensor is disposed in a fixed position relative to the compass housing. A magnet is rotatably mounted relative to the magnetic field sensor and independently aligned with a terrestrial magnetic field. The magnet has a magnetic field with a magnetic field direction and the electronic magnetic field sensor is located within a range of influence of the magnetic field. The electronic magnetic field sensor has a first magnetoresistor with a first fixed reference axis and an electric resistance of the first magnetoresistor is a function of a first angle of rotation between the fixed first reference axis and the direction of the magnetic field. The electronic magnetic field sensor defines a first differential bridge circuit and the first magnetoresistor is disposed in the first differential bridge circuit which during operation of the compass, supplies an output voltage dependent on the first angle of rotation.

Abstract: An avionics display (10) for use in an aircraft navigation system including a navigation receiver. The avionics display (10) includes a needle (12) for indicating the position, heading, glide slope or other navigational parameter of the aircraft and a stepper motor (14) coupled with the needle and responsive to the navigation receiver for driving the needle in response to the navigation signals received by the receiver. The stepper motor drives the needle at a much higher torque than prior art displays and is therefore less sensitive to contaminates and magnetic interference and is less fragile.

Abstract: An alternating bias current is made to flow through a coil wound around an MI device incorporated in an oscillation circuit, and an alternating-current bias magnetic field is applied to the MI device. An amplitude-modulated waveform corresponding to peaks which alternate between two different heights is provided at the output of the oscillation circuit in accordance with an impedance variation in the MI device according to an external magnetic field and the alternating-current bias magnetic field. The difference in height between the peaks corresponds to the strength of the external magnetic field. The output of the oscillation circuit is envelope-detected by an envelope detecting circuit, and an alternating-current component from which a direct-current component is eliminated is inputted to a comparator. The comparator provides an output signal having a digital waveform pulse-width modulated according to the difference in height between the peaks.

Abstract: An apparatus for mounting a magnetometer including a frame and a platform mounted for rotation within the frame. The magnetometer and one or more counterweights are mounted within the platform such that gravity acting on the counterweights maintains the magnetometer in a horizontal orientation. A first coil is coupled in parallel with the magnetometer and is wound around the perimeter of the platform. A second coil is wound around the perimeter of the frame such that the first and second coils form an air core transformer. The second coil terminates in two terminals which provide a communication port. A sensing circuit coupled to the port electrically communicates with the magnetometer via the inductive coupling provided by the transformer. In alternative embodiments, each of the first and second coils is implemented as two coils with associated diodes.

Abstract: A real time directional orientation apparatus is disclosed for use in a two pi (2.pi.) geometry. The apparatus is to be affixed to an object which translates in space. A cylindrical disk is suspended in a fluid in concert with a magnet. The cylindrical disk is disposed inside a cylindrical housing. A light source is in communication with the disk and the light is propagated through the disk where it is finally projected from the disk in a radial fashion. The light beam projected is detected by a bank of photon sensitive detectors lining the interior of the cylindrical housing. The light source is propagated through two coplanar, orthogonal light channels which emanate from the center of the disk in a radial fashion. The photon sensitive detectors register the orientation of the light channels against a known starting value.

Abstract: A position sensor has a ring of a material of high permeability that is floated on a liquid within a hermetically sealed toroid, so as to hold the ring in a horizontal position. Exciting coils are distributed uniformly about the ring to enclose the cross section thereof, and receiving coils are distributed uniformly about the circumference of the ring.

Abstract: A quick ranging technique controlled by a microcomputer, makes predetermined stepped adjustments to the charge times in a ranging circuit to bring the charge time into a required range, thusly minimizing calibration time for an electronic compass; a digital filter also controlled by the microcomputer smooths out the magnetic field component signals.

Abstract: An electronic compass for vehicles comprising at least two magnetic sensors arranged in use to be respectively responsive to orthogonal horizontal components of a magnetic field which includes the earth's magnetic field and a spurious magnetic field which is associated with the vehicle, for producing electrical signals corresponding to said components, data storage means arranged to store signals derived from the sensors as the vehicle is rotated in the horizontal plane during a compass setting cycle, and signal processor means responsive to electrical signals produced by the sensors after the setting cycle has been completed and to the signals stored during the setting cycle, for providing output signals indicative of the bearing appertaining to the heading of the vehicle in which the effects of the spurious magnetic field are compensated for.

Abstract: An electronic compass for vehicles comprising three magnetic sensors arranged in use to be respectively responsive to orthogonal components of a magnetic field which includes the earth's magnetic field and a spurious magnetic field which is associated with the vehicle, for producing electrical signals corresponding to said components, tilt sensor means responsive to vehicle tilt with respect to the horizontal plane, data processor and storage means arranged to store signals derived from the sensors as the vehicle is turned through a compass setting cycle, and signal processor means responsive to electrical signals produced by the sensors after the setting cycle has been completed and to the signals stored during the setting cycle, for providing compensated signals related to the bearing appertaining to the heading of the vehicle in which the effects of the spurious magnetic field are compensated for and further processor means to which the compensated signals are applied and which is responsive to the tilt se

Abstract: A system to control the effect of northerly turning error which may occur in any direction indicating navigation instrument which includes a component responsive to the earth's magnetic field. In one form, an aircraft magnetic compass is compensated by electric current in an electromagnet which is made responsive to the rate of turn as sensed by a turn and bank indicator. In another form, an aircraft type slaved gyro directional system is protected from the effect of northerly turning error which occurs in its remotely located magnetic azimuth sensor by disconnecting its control circuit from the gyro when the turn rate reaches a predetermined level, thus allowing the gyro to act solely as a directional gyro during the turn.

Abstract: This system accepts compass outputs from a wide variety of compass output devices such as stepper and synchro devices having different coupling ratios, supply voltages and carrier frequencies. The system then, as part of a PPI radar system, electronically converts these compass outputs without the usual intermediary electromechanical devices into real-time analog reference signals properly phased with respect to the radar timing to provide an electronically stabilized PPI. This is achieved by comparing the points of equal amplitude of any two phases of gyro compass synchro output signals and using these major transition points to provide a digital code indicating the angular position of the gyro output shaft; a microprocessor then transforms the code, by comparison with a previously stored position code into coded position change signals which are then used to change a stored angular value, representing the course of the ship.

Abstract: A digital compass including a two-axis earth's magnetic field sensor and a earing processor computes the bearing for local display or transmission from a remote site to a local site for display and/or storage. The bearing processor portion of the digital compass includes an analog-to-digital converter configured for ratiometric measurements to compute the ratio of the x-axis and y-axis signals (smaller divided by the larger) from the aforementioned two-axis earth's magnetic field sensor. A programmable memory unit controlled, inter alia, by the data line outputs of the analog-to-digital converter, contains the arc tangent function for angles from 0.degree. to 90.degree.. The data line outputs from the memory unit defines a quadrant displacement angle in the range of 0.degree. to 90.degree. which is subsequently added to the cardinal point forming the lower boundary in bearing of the host quadrant.

Abstract: An electronic compass for vehicles such as automobiles comprising a float mechanism including a permanent magnet for following the earth's magnetic field and four Hall effect sensors for detecting magnet orientation at points corresponding to the cardinal compass points. The Hall effect sensors are connected to triggering circuits having overlapping thresholds so that two circumferentially adjacent sensors and sensor trigger circuits cooperate to indicate not only the corresponding cardinal compass points but also the secondary compass point intermediate the cardinal points. The sensor trigger circuitry is connected to a two-character multiple-segment display for indicating vehicle orientation at either one of the four cardinal compass points or one of the four secondary compass points intermediate successive cardinal points.

Abstract: The peaks of synchro or step data representative of compass heading are detected and the resulting logic levels are latched into a register by an enable pulse generated in response to the data itself. Three outputs from the register are fed directly to the computer input port and provide 1/6.degree. resolution and 1.degree. range. Two of the register outputs are decoded and used to operate an up/down counter. The output of the counter is applied to the computer input port and provide 1.degree. resolution and 16.degree. range.

Abstract: A direction finding system of the type finding a present direction on 4N direction divisions defined by 2N boundary levels for automotive vehicles, said system comprising a magnetic sensor circuit for generating a pair of electric signals indicating two perpendicular components of the earth's magnetic field, a logic circuit for signal-converting the electric signals, discriminating and latching to generate direction indicating 2N binary signals with reference to predetermined 2N boundary indicating levels, a sorting circuit for sorting the binary signals to generate one of 4N direction signals and a display device for displaying a corresponding direction.

Abstract: A synchro transmitter having a rotor driven by a compass communicates the heading information from that compass to a plurality of loads via respective synchro receivers whose rotors are energized with direct current or carry permanent magnets and whose stators are supplied with a triad of d-c signals from three modular units each having one input connected to an output lead of a respective stator winding of the transmitter and another input connected in parallel with a winding on the transmitter rotor to a source of alternating current. A demodulator in each unit compares the current of the respective output lead with the reference current from the a-c source and feeds the result to an integrating operational amplifier which emits the corresponding d-c signal.

Abstract: A compass device for underwater use and having substantially no magnetic nature or influence utilizes three Hall effect generators in an array wherein two of the generators have their principal axes of magnetic response extending normal to one another and at 45.degree. to the axis of the third generator. The array is rotatable relative to a base carrying three lights and solid state analog logic circuitry for causing the lights to be variously lighted and extinguished to indicate a need to turn left, to turn right, or being on course.

Abstract: Set out herein is an electronic compass suitable for public use having a conventional pin supported magnetic needle which is placed over a set of magneto diodes or Hall devices arranged in quadrature. The magneto diodes or Hall devices are thus exposed to the highly enhanced magnetic field around the needle and will thus provide a direct readout, in electrical form, of the deviation from magnetic North. In this manner a relatively conventional arrangement of a magnetic needle may be utilized to provide the necessary signal source for electronic pick-off with the same accuracy obtained by a conventionally suspended arrangement practiced in the past.

Abstract: A detector to detect angular positions of a rotatable magnet, i.e., a magnetic compass, having one or more flux-sensitive components, namely Hall-elements. The detector includes a substantially flat and circular carrying body to be mounted on the top or bottom of a compass. On the carrying body the Hall-elements are mounted parallel to and close to the flat surface and positioned on diameters perpendicular to axes of symmetry of the flat surface. The carrying body can be rotatably fastened on the compass case and locked in desired predetermined positions.

Abstract: A radar system having an adaptive compass drive capable of operation over a wide variety of compass outputs and supply voltages and frequencies. For compass outputs in the form of multi-phased analog signals, a digital phase detector converts the signals to a series of digital pulses which are used to operate a three-phase to UP-DOWN pulse converter. If the gyro compass output signals are in the form of overlapping digital signals, the converter changes the signals directly to a sequence of UP or DOWN pulses. The UP-DOWN pulses are used to operate a binary counter which operates the phases of a multi-phased stepper motor which is coupled to the true bearing scale of the radar system the output of which may also be used to operate a north stabilization synchro converter for the radar display.

Abstract: An orientation system adapted to be mounted within a vehicle, comprising a display including a rotational heading indicating compass card fabricated from an image retaining electronic display panel responsive to bearing data signals.

Abstract: A marine auto pilot employing a compass with a Hall-effect sensing element in conjunction with a magnetic circuit designed to provide a high intensity magnetic field; electrical circuitry designed to produce high servo-loop gain at frequencies lower than the normal sea wave frequencies, and lower gain at the normal sea wave frequencies; a D.C. Linear Motor drive system in conjunction with a rudder position feedback signal; and a linear ball-screw and nut gearing system for converting the high-speed output of the direct current drive motor to a low-speed high-torque drive at the rudder, having the nut and ball-screw connected through rolling contact balls.

Abstract: Apparatus for detecting the direction of a magnetic field includes a magnetoresistive device comprising an insulating substrate, first and second ferromagnetic metal film strips on the substrate for providing first and second main current conducting paths respectively perpendicular to each other, the ends of the strips being connected together to form an output terminal and having current input terminals connected to the opposed ends of the strips. A stationary bias magnet is disposed adjacent the magnetoresistive device for supplying a bias flux at a predetermined angle relative to a main current conducting path.In one application of this apparatus, the magnetic field is supplied from, for example, a magnet, such as a rotary magnet, thereby to apply, with the bias flux, a composite flux to the magnetoresistive device. An output signal is derived from the output terminal that is a function of the direction in which the magnetic field is supplied.

Abstract: A remote reading magnetic compass operative with only two electrical connections for both power and data purposes. The compass includes a disc which is photoelectrically sensed to provide output signals representative of compass heading and is supported by a gimbal assembly including pivots which serve as electrical terminals by which energizing power is supplied to the compass electronics and by which data is read out from the compass.

Abstract: An apparatus is disclosed for determining a measured direction such as the direction of a ship or airplane relative to an external magnetic field such as the magnetic field of the earth. This apparatus comprises means for establishing a magnetic field rotating at constant angular velocity, located to influence the external magnetic field. The rotating magnetic field vector bears a known angular relationship as a function of time to the measured direction. A detector is located to be influenced by the rotating and external fields for detecting the occurrence of a predetermined angular relationship between the rotating and external magnetic field vectors.

Abstract: An arrangement for indicating a relative azimuth between two objects remote from each other, such as a control station and a mobile unit remotely controlled by the station, on which are respectively mounted first and second synchronous transmitters for generating and transmitting their respective signals corresponding respectively to true azimuths of the station and the unit. The control station is further provided with a relative azimuth indicating device including outer stational and inner rotatable dials, a rotatable indicator, first and second synchronous receivers, each having means for effecting rotation by receiving one of the signals corresponding thereto, and means for transmitting the respective rotations of the receivers to the inner dial and the indicator, respectively.