# US 7,994,773 B2 · Apparatus and method for in-field magnetic measurements > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,994,773 B2 - Document ID: US7994773B2 - Status: Granted - Kind: B2 - Application number: 12/171,626 - Filed: 2008-07-11 - Published: 2010-01-14 - Granted: 2011-08-09 - Earliest claimed: 2008-07-11 - Assignees: Data Security, Inc. - Inventors: Robert A. Schultz - Web page: https://patentgrep.com/patent/US7994773B2 ## CPC - G01R 33/0023: {Electronic aspects, e.g. circuits for stimulation, evaluation, control; Treating the measured signals; calibration (G01R33/0017 takes precedence)} - G01R 33/072: {Constructional adaptation of the sensor to specific applications} - G01R 35/005: {Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references (G01R33/0035, G01R35/002 take precedence)} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A magnetic field verifier apparatus includes a magnetic field detection element configured to produce a voltage signal in response to an applied magnetic field wherein the voltage signal corresponds to the strength of the applied magnetic field. A current source coupled to the magnetic field detection element provides a stimulating current for the magnetic field detection element that builds in a ramp-like progression. A microcontroller is in communication with the voltage signal wherein the microcontroller is configured to detect and control the ramping time of the magnetic field detection element and to sense after the ramping time the voltage signal from the magnetic field detection element. The magnetic field verifier apparatus is configurable to sense particular field strengths at various frequencies and store the readings to provide the user with a reliable verification that a particular magnetic field strength has been produced in a particular environment. ## Claims ### Claim 1 An apparatus for sensing magnetic fields comprising: a magnetic field detection element configured to produce a voltage signal in response to an applied magnetic field wherein the voltage signal corresponds to the strength of the applied magnetic field; a current source configured to provide current to the magnetic field detection element such that a stimulating current builds in a ramp-like progression; a microcontroller operatively in communication with the magnetic field detection element wherein the microcontroller is configured to detect a ramping time of the magnetic field detection element and to sense after the ramping time the voltage signal from the magnetic field detection element. ### Claim 2 (depends on 1) The apparatus of claim 1 wherein the microcontroller further comprises a pulse width modulator circuit that controls and senses the ramping time of the magnetic field detection element. ### Claim 3 (depends on 1) The apparatus of claim 1 further comprising a display operatively connected to the microcontroller. ### Claim 4 (depends on 3) The apparatus of claim 3 wherein the display comprises a binary indication of whether the applied magnetic field's maximum strength exceeded a predetermined amount. ### Claim 5 (depends on 3) The apparatus of claim 3 wherein the display comprises a numeric output corresponding to the applied magnetic field's maximum strength. ### Claim 6 (depends on 1) The apparatus of claim 1 wherein the current source comprises a capacitor operatively coupled across the magnetic field detection element such that an applied voltage creates the stimulating current that builds in a ramp-like progression. ### Claim 7 (depends on 6) The apparatus of claim 6 wherein the current source further comprises a resistor with a first end operatively connected to the capacitor and the magnetic field detection element and a second end operatively connected to a voltage source, such that resistance of the resistor relative to resistance of the magnetic field detection element in combination with a voltage from the voltage source approximates a current source. ### Claim 8 (depends on 1) The apparatus of claim 1 further comprising a removably connectable display. ### Claim 9 (depends on 8) The apparatus of claim 8 wherein the removably connectable display comprises a computer operatively connectable to the microcontroller through at least one of a group comprising a wireless connection, a serial connection, and a universal serial bus connection. ### Claim 10 A method of calibrating a magnetic field detection device placed in a known magnetic field comprising: a) applying a current that builds in a ramp-like progression to the magnetic field detection element; b) sensing a voltage output from the magnetic field detection element after a predetermined length of time; c) storing at least one value corresponding to the predetermined length of time as a predetermined function of a value corresponding to the voltage output and the known magnetic field. ### Claim 11 (depends on 10) The method of claim 10 further comprising: d) varying the predetermined length of time; e) repeating steps a through c. ### Claim 12 (depends on 11) The method of claim 11 further comprising storing a value corresponding to a range of predetermined lengths of time as a predetermined function of the value corresponding to the voltage output and the known magnetic field. ### Claim 13 (depends on 10) The method of claim 10 wherein the predetermined function comprises determining whether the value corresponding to the voltage output corresponds to an expected value based on the known magnetic field. ### Claim 14 A method of sensing an applied magnetic field comprising: applying a stimulating voltage to a magnetic field detection element via a capacitor such that the current builds in a ramp-like progression; sensing an output voltage corresponding to a strength of the applied magnetic field from the magnetic field detection element upon the passing of a predetermined time period after applying the stimulating voltage to the magnetic field detection element; determining which of a first value corresponding to the output voltage and a second value corresponding to a second output voltage has a larger value; storing the larger value. ### Claim 15 (depends on 14) The method of claim 14 wherein the step of applying a stimulating voltage to a magnetic field detection element via a capacitor such that the current builds in a ramp-like progression further comprises applying the stimulating voltage via a pulse width modulation voltage pulse from a microcontroller. ### Claim 16 (depends on 14) The method of claim 14 where the step of determining which of the first value corresponding to the output voltage and the second value corresponding to the second output voltage has the larger value further comprises determining which of a first absolute value corresponding to the output voltage and a second absolute value corresponding to a second output voltage has the larger value. ### Claim 17 A method of sensing an applied magnetic field comprising: applying a stimulating voltage to a magnetic field detection element via a capacitor such that the current builds in a ramp-like progression; sensing an output voltage corresponding to a strength of the applied magnetic field from the magnetic field detection element upon the passing of a predetermined time period after applying the stimulating voltage to the magnetic field detection element; storing a value corresponding to the output voltage. ### Claim 18 (depends on 17) The method of claim 17 wherein storing a value corresponding to the output voltage further comprises determining whether the value exceeds a predetermined value. ### Claim 19 (depends on 16, 17) The method of claim 17 further comprising repeating the method of claim 16 and storing a plurality of values corresponding to the output voltage on a memory circuit. ### Claim 20 (depends on 19) The method of claim 19 further comprising removing the memory circuit from the applied magnetic field and operatively connecting the memory circuit to a display. ### Claim 21 (depends on 17) The method of claim 17 wherein the step of applying a stimulating voltage to a magnetic field detection element via a capacitor such that the current builds in a ramp-like progression further comprises applying the stimulating voltage via a pulse width modulation voltage pulse from a microcontroller. ### Claim 22 A device for sensing magnetic fields in at least two directions comprising: at least two magnetic field detection units wherein each magnetic field detection unit comprises: a magnetic field detection element configured to produce a voltage signal in response to an applied magnetic field wherein the voltage signal corresponds to the strength of the applied magnetic field; a capacitor operatively coupled across the magnetic field detection element such that a stimulating current for the magnetic filed detection element builds in a ramp-like progression upon application of a stimulating voltage; an amplifier operatively coupled to the voltage signal from the magnetic field detection element; at least one microcontroller operatively coupled to at least one of the amplifiers for the magnetic field detection units wherein the microcontroller is configured to detect the ramping time of each magnetic field detection element and to sense after the ramping time an amplifier signal corresponding to the voltage signal from each magnetic field detection element; at least one display connectable to the at least one microcontroller. ### Claim 23 (depends on 22) The apparatus of claim 22 wherein each magnetic field detection unit includes at least one microcontroller. ### Claim 24 (depends on 22) The apparatus of claim 22 wherein the display comprises a numeric output corresponding to the applied magnetic field's maximum strength. ### Claim 25 (depends on 22) The apparatus of claim 22 wherein the display comprises a removably connectable display. ### Claim 26 (depends on 22) The apparatus of claim 22 wherein the removably connectable display comprises a computer operatively connectable to the microcontroller through at least one of a group comprising a wireless connection, a serial connection, and a universal serial bus connection. ### Claim 27 (depends on 22) The apparatus of claim 22 wherein the magnetic field detection units each further comprises a housing with fasteners such that the magnetic field detection units are removably securable to each other whereby the magnetic field detection elements of the magnetic field detection unit are approximately mutually orthogonal. ### Claim 28 A device for sensing magnetic fields in at least three directions comprising: at least three magnetic field detection units wherein each magnetic field detection unit comprises: a magnetic field detection element configured to produce a voltage signal in response to an applied magnetic field wherein the voltage signal corresponds to the strength of the applied magnetic field; a microcontroller operatively coupled to the magnetic field detection element wherein the microcontroller is configured to detect the voltage signal from the magnetic field detection element; a reset switch in communication with the magnetic field detection units; wherein the magnetic field detection units each further comprises a housing with fasteners such that the magnetic field detection units are removably securable to each other such that the magnetic field detection elements of the magnetic field detection unit are approximately mutually orthogonal. ### Claim 29 (depends on 28) The apparatus of claim 28 further comprising at least one display in communication with at least one of the magnetic field detection units. ### Claim 30 (depends on 29) The apparatus of claim 29 wherein the display comprises a numeric output corresponding to the applied magnetic field's maximum strength. ### Claim 31 (depends on 29) The apparatus of claim 29 wherein the display comprises a removably connectable display. ### Claim 32 (depends on 31) The apparatus of claim 31 wherein the removably connectable display comprises a computer operatively connectable to the microcontroller through at least one of a group comprising a wireless connection, a serial connection, and a universal serial bus connection.