Magnetic field sensing circuits including wire coils and Hall effect devices are provided which produce high-gain output for a relatively low change in perceived field intensity. Series connected plural Hall effect devices are connected to the coil and include amplifier and integrator circuits interposed at selected points between Hall effect devices to modify the output signal gain and passband. The circuits may include diode and capacitance elements to modify the circuit output signal.
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of U.S. Pat. Application Ser. No. 07/262,372 filed Oct. 25, 1988 now U.S. Pat. No. 4,945,306 issued July 31, 1990.
An electric current sensor employing a Hall effect generator to be used in measuring electrical currents flowing in an electrical conductor. The sensor comprises an amplifier, a constant current source, a gapped toroid core mounted on the component side of a printed circuit board (PCB), a Hall effect generator extending via its output leads from the PCB into the gap of the toroid core, and an inductive loop positioned at the edge of the gap of the toroid core. The inductive loop itself comprises a simple trace formed on the component side of the PCB together with its plated-through-holes extending from the component of the PCB to the printed circuit (clad) side of the PCB. The PCB inductive loop placed at the edge of the gap of the toroid core and connected in series opposition to the output leads of the Hall effect generator, compensates for the unwanted induced voltages in the output leads of the Hall generator.
A technique for determining an offset-reduced Hall voltage (Uh), and/or an offset voltage (UH, offset) of a Hall sensor (1) includes applying a Hall sensor current (I) at first and second taps (a1, a2, a3) of the Hall sensor (1), and determining a first Hall voltage (Uh1) at third and fourth taps (a3, a4) displaced from the first and second taps (a1, a2, a5). A second Hall sensor current is applied modified relative to the first, and a second Hall voltage (Uh2) is determined. The Hall voltage (Uh) and/or Hall voltage offset (Uh,offset) are determined from the first and second Hall voltages. To compensate any offset present, a second measurement applies the second Hall sensor current I at taps (a3, a4) that are spatially displaced relative to the first and/or second taps.
A method for balancing the flux density of a permanent magnet includes sensing flux density in a permanent magnet and if unbalanced relative to a physical center, adjusting the cross-sectional area and shape of the magnet by removing magnetic material from the magnetic pole with the stronger magnetic flux density. This method is repeated until the magnetic flux density is balanced between the opposite poles of the permanent magnet relative to the physical center.
A magnetic resonance monitor measures static and extremely low frequency magnetic fields in order to determine the degree of magnetic resonance with the magnetic moments of a biological substrate, more particularly resonance with the magnetic moments of a human body. A digital bandpass filter varies in response to the magnitude of the static magnetic field so that it selects frequencies of the oscillating magnetic field in accordance with the gyromagnetic equation. A spatial analyzer determines the three spatial components of the filtered signals representing the magnetic field oscillating parallel to the static magnetic field vector and the two circularly-polarized components rotating perpendicular to the static field with helicities opposite to each other. A resonance analyzer evaluates accurately the resonance yield which is the change in biochemical processes due to magnetic field exposures. The magnetic resonance monitor can measure from magnetic fields in residential and workplace environments, either for research studies or for the routine evaluations of health hazards.
