This disclosure provides systems, methods and apparatus for detecting foreign objects. In one aspect an apparatus for detecting a presence of an object is provided. The apparatus includes a resonant circuit having a resonant frequency. The resonant circuit includes a sense circuit including an electrically conductive structure. The apparatus further includes a coupling circuit coupled to the sense circuit. The apparatus further includes a detection circuit coupled to the sense circuit via the coupling circuit. The detection circuit is configured to detect the presence of the object in response to detecting a difference between a measured characteristic that depends on a frequency at which the resonant circuit is resonating and a corresponding characteristic that depends on the resonant frequency of the resonant circuit. The coupling circuit is configured to reduce a variation of the resonant frequency by the detection circuit in the absence of the object.

The present disclosure discloses a safety pipe loop and method for strain monitoring of mountainous pipelines. The safety pipe loop may include a plurality of magnetic test detectors and a protective shell for protecting the plurality of magnetic test detectors. The number of the plurality of magnetic test detectors may be set to 4n, n is an integer number greater than or equal to 1. An angle between any two adjacent detectors of the plurality of magnetic test detectors may be 180°/2n. At least two of the plurality of magnetic test detectors may be connected in parallel through a data transmission line and output data through a data transmission interface. An outer layer of the protective shell may include non-magnetic hard alloy, and an inner layer of the protective shell may include non-metallic materials.

This disclosure provides systems, methods and apparatus for detecting foreign objects. In one aspect an apparatus for detecting a presence of an object is provided. The apparatus includes a resonant circuit having a resonant frequency. The resonant circuit includes a sense circuit including an electrically conductive structure. The apparatus further includes a coupling circuit coupled to the sense circuit. The apparatus further includes a detection circuit coupled to the sense circuit via the coupling circuit. The detection circuit is configured to detect the presence of the object in response to detecting a difference between a measured characteristic that depends on a frequency at which the resonant circuit is resonating and a corresponding characteristic that depends on the resonant frequency of the resonant circuit. The coupling circuit is configured to reduce a variation of the resonant frequency by the detection circuit in the absence of the object.

The invention relates to a method for observing a magnetic field of a material volume, in particular for determining properties of a workpiece under, in particular, magnetic, mechanical, thermal, and/or electrical excitation of a material volume of the workpiece, wherein the magnetic field of the material volume is sensed as a function of time and of frequency with high frequency resolution.

The invention relates to a method for observing a magnetic field of a material volume, in particular for determining properties of a workpiece under, in particular, magnetic, mechanical, thermal, and/or electrical excitation of a material volume of the workpiece, wherein the magnetic field of the material volume is sensed as a function of time and of frequency with high frequency resolution.

A monitoring and forewarning method for coal-rock dynamic disasters based on an electromagnetic radiation and an earth-sound monitoring includes the following steps: (1) calculating the weighted average value of research parameter P(t) during a time period according to the monitoring data collected by the electromagnetic radiation and the earth-sound monitoring system in real time; (2) calculating D(t), the deviation value of P(t); (3) calculating |D(t)| as the deviation threshold value, the average value of |D(t)| during period of normal mining of the working surface; (4) calculating D.sub.S, the number of times that D(t) is greater than |D(t)| in one day; (5) normalizing D.sub.S to obtain the monitoring and forewarning index ; (6) forewarning the hazard state of dynamic disaster of the working surface in real time according to and forewarning method, determining hazard level.

This disclosure provides systems, methods and apparatus for detecting foreign objects. In one aspect an apparatus for detecting a presence of an object is provided. The apparatus includes a resonant circuit having a resonant frequency. The resonant circuit includes a sense circuit including an electrically conductive structure. The apparatus further includes a coupling circuit coupled to the sense circuit. The apparatus further includes a detection circuit coupled to the sense circuit via the coupling circuit. The detection circuit is configured to detect the presence of the object in response to detecting a difference between a measured characteristic that depends on a frequency at which the resonant circuit is resonating and a corresponding characteristic that depends on the resonant frequency of the resonant circuit. The coupling circuit is configured to reduce a variation of the resonant frequency by the detection circuit in the absence of the object.

A method for referencing a plurality of sensor units that can be arranged around the measurement object for surveying a three-dimensional surface of a measurement object, and to an associated measuring device for surveying a surface of a measurement object. A more accurate surveying of the surface of the measurement object is provided.

This disclosure provides systems, methods and apparatus for detecting foreign objects. In one aspect an apparatus for detecting a presence of an object is provided. The apparatus includes a resonant circuit having a resonant frequency. The resonant circuit includes a sense circuit including an electrically conductive structure. The apparatus further includes a coupling circuit coupled to the sense circuit. The apparatus further includes a detection circuit coupled to the sense circuit via the coupling circuit. The detection circuit is configured to detect the presence of the object in response to detecting a difference between a measured characteristic that depends on a frequency at which the resonant circuit is resonating and a corresponding characteristic that depends on the resonant frequency of the resonant circuit. The coupling circuit is configured to reduce a variation of the resonant frequency by the detection circuit in the absence of the object.

A monitoring and forewarning method for coal-rock dynamic disasters based on an electromagnetic radiation and an earth-sound monitoring includes the following steps: (1) calculating the weighted average value of research parameter P(t) during a time period according to the monitoring data collected by the electromagnetic radiation and the earth-sound monitoring system in real time; (2) calculating D(t), the deviation value of P(t); (3) calculating |D(t)| as the deviation threshold value, the average value of |D(t)| during period of normal mining of the working surface; (4) calculating D.sub.S, the number of times that D(t) is greater than |D(t)| in one day; (5) normalizing D.sub.S to obtain the monitoring and forewarning index ; (6) forewarning the hazard state of dynamic disaster of the working surface in real time according to and forewarning method, determining hazard level.