Front end circuits and associated apparatus, systems, and methods for use in electronic devices such as buried utility locators are disclosed. The circuits include receivers and filters on input signals that are coupled to ground rather than differentially. A multiplexing circuit allows shared use of amplifiers, and analog-to-digital converters via a switching mechanism for selectively making or breaking electrical connection to the receiver channels for efficient sharing of electronics resources while minimizing crosstalk interference and advantageously reducing costs.

A near magnetic field variation detection method comprises following steps of: measuring magnetic field by a first magnetic field sensor and a second magnetic field sensor respectively; and calculating a magnetic field measurement difference, wherein the magnetic field measurement difference is (1) a magnitude of a difference of a first-magnetic-field-measurement measured by the first magnetic field sensor and a second-magnetic-field-measurement measured by the second magnetic field sensor, or (2) a magnitude of a difference of a first-magnetic-field-measurement-component measured by the first magnetic field sensor along a characteristic direction and a second-magnetic-field-measurement-component measured by the second magnetic field sensor along the characteristic direction; wherein a near magnetic field variation is occurred when (a) the magnetic field measurement difference is continuously greater than a characteristic-threshold within a characteristic-time-period, or (b) an average value of the magnetic field measurement difference is greater than a characteristic-average-threshold within a characteristic-average-time-period.

A security screening apparatus for use in detecting ferromagnetic objects comprises a detector apparatus which comprises a housing that supports at least one magnetic sensor arranged to produce a signal indicative of an ambient magnetic field or gradient over a zone of sensitivity which extends away from the housing, the size of the zone being large enough to contain the whole body of the person, and a signal processing circuit which receives as an input the signal from the magnetic sensor and which, in response to a change in the signal produces an alert signal. A beacon that comprises a light source is able to emit at least two visually distinct colours of light, and a control means controls the light source such that in a first condition in the absence of the alert signal the beacon emits a first colour light and in a second condition corresponding to the presence of the alert signal the beacon emits a second, different, colour of light. The light source is arranged such that the position and/or size and/or shape of the illuminated area of the light source in the first condition is different from the position and/or size and or shape of the illuminated area of the light source in the second condition.

A movement detection unit includes a movable body, a first sensor, a second sensor, and a signal processor. The movable body performs a movement in a first direction. The first sensor detects a first magnetic field change which is caused by the movement of the movable body and outputs a first signal. The second sensor is provided in the first direction at a location different from a location of the first sensor. The second sensor detects a second magnetic field change which is caused by the movement of the movable body and outputting a second signal. The signal processor includes a signal generating circuit that generates a third signal and a fourth signal on a basis of the first signal. The third signal and the fourth signal have waveforms different from each other.

A method for scanning artificial structure, wherein a scanning artificial structure apparatus comprises four magnetic-field sensors, the four magnetic-field sensors are non-coplanar configured, the method comprises following steps of: moving the scanning artificial structure apparatus along a scanning path within a to-be-tested area, in the meantime, measuring magnetic field by the four magnetic-field sensors, and recording a position sequence when measuring magnetic field, wherein four magnetic-field measurement sequences are measured by the four magnetic-field sensors; and calculating a magnetic-field variation distribution from the four magnetic-field measurement sequences and the position sequence, wherein the magnetic-field variation distribution is corresponding to at least one artificial structure distribution.

A method for locating a buried casing stub may comprise a) identifying a target region, b) providing at each of a plurality of survey points in the target region a casing stub locator that includes a vector magnetometer, c) measuring the magnetic field at each of the survey points using the vector magnetometer so as to generate a plurality of magnetic field measurements, d) using the magnetic field measurements to generate a model of the magnetic field of the target region, e) fitting the model generated in step d) to a selected model of a magnetic anomaly created by the casing stub so as to generate model fit information (MFI), and f) locating the casing stub using the MFI. At each survey point, an expected Earth magnetic field can be subtracted from the measured magnetic field. A total station can measure the position and/or the azimuth of the package.

A method for modeling a subsurface anomalous magnetization zone including the steps of generating a magnetic field model of the subsurface anomalous magnetization zone, inverting the magnetic field model; and generating a model of the sub-surface anomalous magnetization zone based on the inversion. The step of generating the magnetic field model include generating the magnetic field model from induced magnetization sources and remnant magnetization sources.

Front end circuits and associated apparatus, systems, and methods for use in electronic devices such as buried utility locators are disclosed. The circuits include receivers and filters on input signals that are coupled to ground rather than differentially. A multiplexing circuit allows shared use of amplifiers, and analog-to-digital converters via a switching mechanism for selectively making or breaking electrical connection to the receiver channels for efficient sharing of electronics resources while minimizing crosstalk interference and advantageously reducing costs.

A method for correcting geomagnetic reference field includes measuring Earth magnetic field elements at least one known geodetic position. Earth magnetic field elements are measured at a position proximate the location. A disturbance function is determined from the Earth magnetic field measurements made at the at least one known geodetic position. A magnetic disturbance field measurement transfer function is estimated between the at the at least one known geodetic and proximate positions to estimate a disturbance function at the proximate position. The estimated magnetic disturbance function is used to correct geomagnetic reference field or measurements made at the location.

A movement detection unit includes a movable body, a first sensor, a second sensor, and a signal processor. The movable body performs a movement in a first direction. The first sensor detects a first magnetic field change which is caused by the movement of the movable body and outputs a first signal. The second sensor is provided in the first direction at a location different from a location of the first sensor. The second sensor detects a second magnetic field change which is caused by the movement of the movable body and outputting a second signal. The signal processor includes a signal generating circuit that generates a third signal and a fourth signal on a basis of the first signal. The third signal and the fourth signal have waveforms different from each other.