A method and apparatus for sensing magnetic field strength with a pair of Hall effect sensors includes sampling a sensed voltage for the Hall effect sensors during a first phase and combining the sensed voltage. During a second phase, obtaining sensed voltages for the Hall effect sensors and combining the sensed voltages. The sensed voltages from the first phase and the second phase are combined to obtain a summed voltage and remove the Hall effect sensor and amplifier offset error value. In one arrangement, the summed voltage corresponds to the sensed Hall voltage of the first Hall effect sensor added to the Hall voltage of the second Hall effect sensor. In another arrangement, the summed voltage corresponds to the sensed Hall voltage of the first Hall effect sensor subtracted by the sensed Hall voltage of the second Hall effect sensor. Changes in the summed voltage with respect to a reference voltage are counted to determine the speed of a rotating shaft having magnets or a similar arrangement.

To provide a magnetic sensor circuit which does not output spike-like voltage errors to a signal processing circuit. A magnetic sensor circuit is provided which is configured so as to output an output signal to a signal processing circuit through a plurality of hall elements driven by a first switch circuit and a second switch circuit controlled by a second control circuit and in which the first switch circuit controls timings at which spikes occur in the output signal of each of the hall elements in such a manner that the timings are not the same, and the second switch circuit selects and outputs an output signal having a period of a timing free of the occurrence of a spike.

According to one embodiment, a magnetic sensor attached to a mobile device detects a magnetic field generated from a magnet attached to an object. A magnetic sensor data processing module generates magnetic sensor data based on the magnetic field, where the magnetic sensor data represents a current position of the magnet of the object. An action processing module processes the magnetic sensor data to determine a movement of the object with respect to the mobile device, while the mobile device remains in a relatively steady location and identifies a predetermined action based on the movement of the object. The predetermined action is then performed within the mobile device.

A surgical locator circuit identifies a surgical target such as a kidney stone by disposing an emitter such as a magnetic source behind or adjacent the surgical target, and employing the circuit to identify an axis to the emitter, thus defining an axis or path to the surgical target. An array of sensors arranged in an equidistant, coplanar arrangement each senses a signal indicative of a distance to the emitter. A magneto resistor sensor generates a variable resistance is responsive to the distance to a magnetic coil emitting a magnetic field. An equal signal from each of the coplanar sensors indicates positioning on an axis passing through a point central to the sensors and orthogonal to the plane. A fixed element and signal conditioner augments and normalizes the signal received from each of the sensors to accommodate subtle differences in magneto resistive response among the plurality of sensors.

A Hall electromotive force signal detection circuit suppresses variations of spike-like error signals that become obstacles to high-precision detection of Hall electromotive force signals. To this end, in the Hall electromotive force signal detection circuit driving plural Hall elements by spinning current techniques and using plural transconductance amplifiers, a reference signal Vcom is supplied from a feedback network controller to a Hall signal feedback network that performs a feedback control so that common voltages of Hall electromotive force signals from the plural Hall elements match with the reference signal Vcom and to an output signal feedback network that feeds back a voltage obtained by dividing a difference between an output voltage and the reference signal Vcom. In this manner, the variations of spike signals are suppressed.

In one aspect, bridge circuitry includes a first magnetoresistance (MR) element; a second MR element connected in series with the first MR element at a first node; a third MR element; a fourth MR element connected in series with the third MR element at a second node; a first switch connected at one end to a supply voltage and connected at the other end to the third MR element; a second switch connected at one end to ground and connected at the other end to the fourth MR element; a third switch connected at one end to ground and connected at the other end to the third MR element and the first switch; and a fourth switch connected at one end to the supply voltage and the other end to the fourth MR element and the second switch. The first and second MR elements are in parallel with the third and fourth MR elements.

In a magnetic sensor using sensitive circuits sensing magnetic fields by the magnetic impedance effect, a sensitivity-to-noise ratio is improved. A magnetic sensor 10 includes: a sensitive circuit 12A including sensitive parts sensing magnetic fields by magnetic impedance effect; and a sensitive circuit 12B including sensitive parts sensing magnetic fields by magnetic impedance effect, wherein at least a part of current paths of the sensitive circuit 12A and at least a part of current paths of the sensitive circuit 12B overlap in a plan view, and one end portion of the sensitive circuit 12A and one end portion of the sensitive circuit 12B are electrically connected.

A magnetic sensor that includes a Hall element; a switch circuit configured to switch a direction of a drive current supplied to the Hall element between a first direction and a second direction; a magnetic field detection circuit configured to execute a detection operation for detecting a target magnetic field acting on the Hall element, based on a first difference between a Hall voltage generated in the Hall element when the drive current is supplied to the Hall element in the first direction and a Hall voltage generated in the Hall element when the drive current is supplied to the Hall element in the second direction; and a test magnetic field generation circuit configured to generate a test magnetic field different from the target magnetic field in a test operation.

In one aspect, bridge circuitry includes a first magnetoresistance (MR) element connected with a second MR element at a first node; a third MR element connected with the first MR element at a second node; a fourth MR element connected with the third MR element at a third node; a fifth MR element connected with a sixth MR element at a fourth node; a seventh MR element connected with the fifth MR element at a fifth node; and an eighth MR element connected with the seventh MR element at a sixth node; and a plurality of eight switches. Six of the plurality of eight switches are each connected to a corresponding one node.

A metal detection apparatus that can accurately and automatically determine whether a metal passing through the inspection area is a magnetic or non-magnetic metal comprises a detection unit quadrature-detecting a differential detection signal of magnetic field fluctuation in the inspection area due to the passage of a workpiece, and a determination unit that determines the presence or absence of a mixed metal based on both fluctuation components after the detection. The determination unit compares sample signal phase data obtained beforehand from the detection signal of the magnetic field fluctuation in the inspection area due to the passage of various metal samples, with the signal phase data obtained from the detection signal of the magnetic field fluctuation in the inspection area due to the passage of the workpiece mixed with metal, and determines the type of metal passing through the inspection area based on the phase determination result.