A gradient magnetic field sensor includes: an AC power supply connection terminal to which a first power supply terminal included in an AC power supply is connected; a first magnetic core connected between the connection terminal and the ground; a second magnetic core connected in parallel with the first magnetic core between the connection terminal and ground; an AC current control unit connected between the connection terminal and at least one of the first magnetic core and the second magnetic core and configured to control an AC current flowing through at least one of the first and second magnetic core; a first detection coil wound around the first magnetic core; a second detection coil wound around second magnetic core and differentially-connected with the first detection coil; and a detection circuit that detects a voltage difference between first voltage output from first detection coil and second voltage output from the second.

A gradient magnetic field sensor includes: an AC power supply connection terminal to which a first power supply terminal included in an AC power supply is connected; a first magnetic core connected between the connection terminal and the ground; a second magnetic core connected in parallel with the first magnetic core between the connection terminal and ground; an AC current control unit connected between the connection terminal and at least one of the first magnetic core and the second magnetic core and configured to control an AC current flowing through at least one of the first and second magnetic core; a first detection coil wound around the first magnetic core; a second detection coil wound around second magnetic core and differentially-connected with the first detection coil; and a detection circuit that detects a voltage difference between first voltage output from first detection coil and second voltage output from the second.

Apparatus includes a first portion of conductive material having varying response to a generated magnetic field along a length of the conductive material, wherein the first portion of conductive material produces a varying eddy current and a varying reflected magnetic field, in response to the generated magnetic field. The apparatus further includes one or more reference portions of conductive material having a relatively invariable response to the generated magnetic field, wherein the reference portion of conductive material produces a relatively invariable eddy current and a relatively invariable reflected magnetic field in response to the generated magnetic field.

The present invention discloses a magnetic probe device. The magnetic probe device includes a magnetic probe body and a signal processing circuit, and an output end of the magnetic probe body is connected with an input end of the signal processing circuit; the signal processing circuit includes a first capacitor, a second capacitor, a Faraday shield and a step-up transformer, and the Faraday shield is fixedly arranged between a primary winding and a secondary winding of the step-up transformer; a center tap is arranged at the primary winding of the step-up transformer, and the center tap is grounded; and a first end of the primary winding is in series connection with the first capacitor, and a second end of the primary winding is in series connection with the second capacitor. The magnetic probe device provided by the present invention can improve the signal-to-noise ratio of a magnetic probe and the measurement accuracy of the magnetic field in plasma.

A magnetic field sensor system comprising a first magnetic field sensor, one or more second magnetic field sensors and an amplifier and all magnetic field sensors are connected in series so that the respective output signals can be added up to a common input signal of the amplifier.

A magnetic field monitor includes a magnetic field sensor that generates an electronic signal at a time period representing a magnetic field of the environment and includes a sensor transducer having a sensor bobbin, a primary coil, a secondary, over-winding coil, a sensor circuit, a controller connected to the primary coil, and a digitally controlled potentiometer connected to the secondary coil and controller. A non-linear output is converted to a quantitative linear output.

A magnetic field monitor includes a magnetic field sensor that generates an electronic signal at a time period representing a magnetic field of the environment and includes a sensor transducer having a sensor bobbin, a primary coil, a secondary, over-winding coil, a sensor circuit, a controller connected to the primary coil, and a digitally controlled potentiometer connected to the secondary coil and controller. A non-linear output is converted to a quantitative linear output.

A sensor die may include a set of sensing elements and a test structure associated with determining a magnetic sensitivity of the set of sensing elements. The test structure includes a first test sensing element sensitive in a direction in a plane defined by a surface of the sensor die, a second test sensing element sensitive in the direction in the plane defined by the surface of the sensor die, and a wire on chip (WoC) associated with applying a magnetic field to the first test sensing element and the second test sensing element. The first test sensing element, the second test sensing element, and the WoC may be arranged such that, when current flows through the WoC, the first test sensing element senses a component of the magnetic field in the direction, and the second test sensing element senses a component of the magnetic field in a perpendicular direction.

A system and method that can automatically select a frequency of a magnetic field in a magnetic tracking system. A magnetic tracking system emits an alternating magnetic field using a set of three frequencies. In the present approach, a transmitter is capable of generating multiple sets of three frequencies. A processor selects a first set of frequencies to use and causes the receiver to measure the amplitude of the magnetic field at those frequencies. In one embodiment, the frequency set having the lowest energy is selected. The processor then compares an estimated jitter at those frequencies to the actual jitter experienced using the frequencies. If the actual jitter exceeds the estimated jitter by a predetermined amount, the processor switches to a different set of frequencies and causes the receiver to measure the magnetic field at the new set of frequencies. The process may repeat using the additional sets of frequencies.

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.