# US 12,000,909 B2 · Measuring device for weak and slowly changing magnetic fields, in particular for biomagnetic fields > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,000,909 B2 - Document ID: US12000909B2 - Status: Granted - Kind: B2 - Application number: 17/621,298 - Filed: 2020-06-09 - Published: 2022-09-15 - Granted: 2024-06-04 - Earliest claimed: 2019-06-21 - Assignees: Christian-Albrechts-Universitaet zu Kiel - Applicants: Christian-Albrechts-Universitaet zu Kiel - Inventors: Eckhardt Quandt; Reinhard Knoechel; Patrick Hayes; Sebastian Toxvaerd - Web page: https://patentgrep.com/patent/US12000909B2 ## CPC - G01R 33/0286: {comprising microelectromechanical systems [MEMS] (MEMS devices in general B81B)} - G01R 33/18: Measuring magnetostrictive properties - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A magnetic field measuring device having a cantilevered, mechanically vibratable, rectangular substrate strip, at least one flat side of the substrate strip being coated with a magnetostrictive material system, further having drive means designed for the temporally periodic exertion of a force component directed perpendicular to the flat sides of the substrate strip on at least one part of a flat side of the substrate strip with a predetermined excitation frequency and having a detection device for detecting an electrical signal generated by the vibration of the substrate strip, wherein a. the substrate strip is formed from a material with a modulus of elasticity greater than 5 GPa and b. the excitation frequency is set up as a function of the dimensions of the substrate strip in such a way that the substrate strip oscillates in mechanical resonance and forms a U-mode, and c. the detection device has an induction coil which surrounds the substrate strip in a contactless manner and has a coil axis aligned along the substrate strip. ## Claims ### Claim 1 A magnetic field measuring device comprising a cantilevered, mechanically vibratable, rectangular substrate strip having a long axis and a short axis, at least one flat side of the substrate strip being coated with a magnetostrictive material system, further comprising drive means designed for temporally periodic exertion of a force component directed perpendicular to the flat sides of the substrate strip on at least part of a flat side of the substrate strip with a predetermined excitation frequency, and comprising a detection device for detecting an electrical signal generated by the vibration of the substrate strip, wherein the substrate strip is formed from a material with a modulus of elasticity greater than 5 GPa, the detection device has an induction coil which surrounds the substrate strip in a contactless manner and has a coil axis aligned along the substrate strip, and the predetermined excitation frequency is a function of the dimensions of the substrate strip such that the substrate strip oscillates in mechanical resonance and forms a U-mode, wherein a U-mode is a bending of the strip along the short axis in the shape of a symmetrical arc open upwards or downwards, wherein the substrate strip oscillates in mechanical resonance and forms a U-mode with at least one nodal line and the induction coil is formed from at least two coaxial, non-overlapping, series-connected partial coils, wherein each two adjacent partial coils have opposite winding directions and are arranged on different sides of the at least one node line. ### Claim 2 (depends on 1) The magnetic e field measuring device according to claim 1, wherein the substrate strip is formed from a material with a modulus of elasticity greater than 20 GPa. ### Claim 3 (depends on 2) The magnetic field measuring device according to claim 2, wherein the substrate strip is formed from a ceramic, a semiconductor or a glass. ### Claim 4 (depends on 1) The magnetic field measuring device according to claim 1, wherein the substrate strip is formed from a monocrystalline semiconductor. ### Claim 5 (depends on 1) The magnetic field measuring device according to claim 1, wherein the drive means comprise an electrical frequency generator and at least one piezo transducer, the at least one piezo transducer being arranged on a flat side of the substrate strip which is opposite the flat side coated with the magnetostrictive material system. ### Claim 6 (depends on 5) The magnetic field measuring device according to claim 5, wherein the at least one piezo transducer completely covers the flat side. ### Claim 7 (depends on 5) The magnetic field measuring device according to claim 5, wherein the at least one piezo transducer is sputtered aluminum nitride between two metal layers. ### Claim 8 (depends on 1) The magnetic field measuring device according to claim 1, wherein the substrate strip is formed from a material with a modulus of elasticity greater than 75 GPa. ### Claim 9 (depends on 1) The magnetic field measuring device according to claim 1, wherein the substrate strip is formed from silicon. ### Claim 10 A magnetic field measuring device comprising a cantilevered, mechanically vibratable, rectangular substrate strip having a long axis and a short axis, at least one flat side of the substrate strip being coated with a magnetostrictive material system, further comprising drive means designed for temporally periodic exertion of a force component directed perpendicular to the flat sides of the substrate strip on at least part of a flat side of the substrate strip with a predetermined excitation frequency, and comprising a detection device for detecting an electrical signal generated by the vibration of the substrate strip, wherein the substrate strip is formed from a material with a modulus of elasticity greater than 5 GPa, the detection device has an induction coil which surrounds the substrate strip in a contactless manner and has a coil axis aligned along the substrate strip, and the predetermined excitation frequency is a function of the dimensions of the substrate strip such that the substrate strip oscillates in mechanical resonance and forms a U-mode, wherein a U-mode is a bending of the strip along the short axis in the shape of a symmetrical arc open upwards or downwards, wherein the substrate strip oscillates in mechanical resonance and forms a U-mode with at least one nodal line and the induction coil as an electrical oscillating circuit has a resonance frequency and the mechanical resonance frequency of the substrate strip, at which a U-mode is formed, lies within the half-width of the induction coil resonance. ### Claim 11 (depends on 10) The magnetic field measuring device according to claim 10, wherein the magnetic field measuring device has a trimming capacitor connected in parallel with the induction coil.