According to some embodiments of the present invention, a magnetometer includes at least one sensor for sensing a magnetic field component, a biasing circuit, and a processor. The sensor generates an output signal having a signal characteristic that varies in response to the sensed magnetic field component and in response to an applied bias. The biasing circuit dynamically biases the sensor in response to a bias setting signal. The processor is coupled to receive the output signal from the sensor and coupled to the biasing circuit. The processor is operable to generate the bias setting signal and thereby control the biasing circuit to dynamically bias the sensor such that the signal characteristic of the output signal is maintained in a target range. The processor determines the magnetic field component sensed by the sensor as a function of the bias setting applied to the sensor.

Magnetometer having a dynamically adjustable bias setting and electronic vehicle compass incorporating the same

A digital compass (20) has a sensing coil (60) wound on an elongated strip of high direct current permeability magnetic material. The sensing coil (60) is connected to a sensing circuit (56). The sensing coil and sensing circuit are responsive to the Earth's magnetic field to provide an oscillating signal at an output (28) of the sensing circuit (56) which varies in frequency with orientation of the at least one sensing coil (60) with respect to the Earth's magnetic field. A microprocessor (36) is connected to receive information inputs from the oscillating signal. The microprocessor converts the information inputs to an indication of orientation of the sensing coil with respect to the Earth's magnetic field based on the frequency of the oscillating signal. A display (52) receives the orientation indication from the microprocessor.

Digital compass and magnetometer having a sensor coil wound on a high permeability isotropic core

A high-frequency oscillation proximity sensor with an improved detection sensitivity uses, as a detection coil 11 , a two-thread coil formed of substantively two coil conductors joined together at their first ends to form a joint connection end and twisted together, one of the two coil conductors being used as a resonance circuit coil L 1 and the other as a copper resistance compensation coil L 2 , and comprises a drive circuit 12 for supplying a drive current to the joint connection end of the two-thread coil to thereby drive the detection coil to oscillate, a buffer 13 for taking out an oscillating output voltage generated at the joint connection end of the two-thread coil, and a phase shift circuit 15 for turning the phase of the oscillating output voltage taken out by the buffer by a predetermined angle and feeding it back to the copper resistance compensation coil to thereby negate the copper resistance of the two-thread coil. The drive circuit comprises a nonlinear amplifier 21 for changing the amplitude of the oscillating voltage generated at the two-thread coil in multiple stages to thereby impart a soft oscillation characteristic to a high-frequency oscillation circuit comprising the nonlinear amplifier and the two-thread coil.

High-frequency oscillation type proximity sensor

A magnetometer having only a single coil winding for sensing the magnetic field along a single axis. Functionally, the invention comprises an oscillator, and means for measuring the duty cycle thereof. The oscillator uses a saturating inductor which also serves as the magnetic-field-sensing element. The inductor is driven with a position voltage and when the current through the inductor exceeds a value which indicates that the core is saturated, the driving voltage switches to an equal-magnitude negative value. This negative drive is maintained until the current again indicates the core to be saturated, at which point the driving voltages switches back to the positive value. With no externally applied field, the inductor current averages to a zero value and the duty cycle of the driving voltage is fifty percent. An externally applied field helps the core saturate in one direction and hinders it in the other, resulting in a change in average inductor current and drive duty cycle.

Single-winding magnetometer with oscillator duty cycle measurement

A magnetometer having only a single coil winding for sensing the magnetic field along a single axis Functionally, the invention comprises an oscillator, an integrator, and a voltage-controlled current source The oscillator uses a saturating inductor which also serves as the magnetic-field-sensing element The inductor is driven with a positive voltage and when the current through the inductor exceeds a value which indicates that the core is saturated, the driving voltage switches to an equal-magnitude negative value This negative drive is maintained until the current again indicates the core to be saturated, at which point the driving voltages switches back to the positive value With no externally applied field, the inductor current averages to a zero value An externally applied field helps the core saturate in one direction and hinders it in the other, resulting in a change in average inductor current An integrator is used in a force-balance feedback arrangement to provide a compensation current to the coil winding The voltage output of the integrator, which is used to generate this compensation current, directly reflects the strength of the magnetic field causing the imbalance, and is the instrument's output signal

Single winding saturable core magnetometer with field nulling

A device powered by a DC source produces an output signal the frequency of which changes as a function of changes in external magnetic fields sensed by such device. A pair of non-linear amplifiers are interconnected so that the output of one amplifier is the input of the other amplifier. An inductive sensor is connected between the outputs of the amplifiers. The inductive sensor has an elongated magnetic core and a coil is wound on the core. The voltages at the outputs of the amplifiers, across the inductive sensor, switch between zero and the full voltage of the DC source.

Magnetic field intensity measuring device with frequency change indication

A device powered by a DC source produces an output signal the frequency of which changes as a function of changes in external magnetic fields sensed by such device. A pair of non-linear amplifiers are interconnected so that the output of one amplifier is the input of the other amplifier. An inductive sensor is connected between the outputs of the amplifiers. The inductive sensor has an elongated magnetic core and a coil is wound on the core. The voltages at the outputs of the amplifiers, across the inductive sensor, switch between zero and the full voltage of the DCisource.

Monroe J. Willner

Papers

Magnetic field intensity measuring device with frequency change indication

Magnetic field detector