# US 7,411,386 B2 · Method for measuring the length variation of a spring, and spring with associated sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,411,386 B2 - Document ID: US7411386B2 - Status: Granted - Kind: B2 - Application number: 11/480,409 - Filed: 2006-07-05 - Published: 2008-01-10 - Granted: 2008-08-12 - Earliest claimed: 2006-07-05 - Assignees: M.D. Micro Detectors S.P.A. - Inventors: Mauro Del Monte - Web page: https://patentgrep.com/patent/US7411386B2 ## CPC - G01B 7/02: for measuring length, width or thickness (G01B7/004, G01B7/12 take precedence) - G01D 5/147: {influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other} - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR ## Abstract A method for measuring a length variation of a spring, comprising the steps of associating a measurement device with a spring, determining a measurement of the intensity of a magnetic field of the measurement device, and, on the basis of the measurement of the intensity of the magnetic field, determining the length variation of the spring. ## Claims ### Claim 1 A method for measuring a length variation of a spring, comprising the steps of: providing a measurement device that comprises; at least one magnet for generating a magnetic field; at least one magnetic field sensor; and a supporting element to which said at least one magnet and said at least one magnetic field sensor are fixed; connecting said measurement device with a spring such that said measurement device is fixed to said spring at a single point; generating, by means of said at least one magnet, a magnetic field such that said magnetic field pass through turns of said spring; determining the intensity of said magnetic field of said at least one magnet of said measurement device; on the basis of said measurement of the intensity of the magnetic field, determining the length variation of said spring. ### Claim 2 (depends on 1) The method of claim 1, wherein said magnet is constituted by a permanent magnet. ### Claim 3 (depends on 1) The method of claim 1, wherein said magnet is constituted by an electromagnet which comprises a solenoid driven by means of an external current source. ### Claim 4 (depends on 1) The method of claim 1, wherein said at least one magnetic field sensor is immersed within said magnetic field generated by said magnet, said intensity of said magnetic field depending on the length variation of said spring. ### Claim 5 (depends on 4) The method of claim 4, wherein said magnetic field sensor is a magnetoresistive sensor. ### Claim 6 (depends on 4) The method of claim 4, wherein said magnetic field sensor is a Hall sensor. ### Claim 7 (depends on 4) The method of claim 4, wherein said supporting element is made of ferromagnetic material, and said magnetic field passes through said supporting element and through said magnetic field sensor. ### Claim 8 (depends on 7) The method of claim 7, wherein the distance between said at least one magnet and said at least one magnetic field sensor both fixed to said supporting element remains constant when said spring changes in length. ### Claim 9 (depends on 1) The method of claim 1, wherein said measurement device is arranged inside said spring. ### Claim 10 (depends on 1) The method of claim 1, wherein said measurement device is arranged outside said spring. ### Claim 11 A spring comprising a measurement device which is adapted to allow detection of the variation of a length of said spring with respect to an inactive condition, wherein said measurement device comprises at least one magnet, at least one magnetic field sensor, and a supporting element to which said at least one magnet and said at least one magnetic field sensor are fixed, said measurement device being fixedly connected to said spring at a single point such that said at least one magnet generates a magnetic field that passes through turns of said spring and through said magnetic field sensor that detects an intensity of said magnetic field whereby said intensity depending on the length variation of said spring. ### Claim 12 (depends on 11) The spring of claim 11, wherein said spring is made of a material whose magnetic permeability is significantly different from the magnetic permeability of vacuum. ### Claim 13 (depends on 11) The spring of claim 11, wherein said spring is made of ferromagnetic material. ### Claim 14 (depends on 11) The spring of claim 11, wherein said spring is made of diamagnetic material. ### Claim 15 (depends on 11) The spring of claim 11, wherein said spring is made of paramagnetic material. ### Claim 16 (depends on 11) The spring of claim 11, wherein said measurement device is arranged inside said spring. ### Claim 17 (depends on 11) The spring of claim 11, wherein said measurement device is arranged outside said spring. ### Claim 18 (depends on 11) The spring of claim 11, wherein said measurement device is connected to a portion of a turn of said spring.