# US 6,965,225 B2 · Coreless current sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,965,225 B2 - Document ID: US6965225B2 - Status: Granted - Kind: B2 - Application number: 10/609,486 - Filed: 2003-07-01 - Published: 2004-12-23 - Granted: 2005-11-15 - Earliest claimed: 2003-06-17 - Assignees: Kinectrics Inc. - Inventors: Eric George de Buda - Web page: https://patentgrep.com/patent/US6965225B2 ## CPC - G01R 15/186: {using current transformers with a core consisting of two or more parts, e.g. clamp-on type (G01R15/142 - G01R15/16 take precedence; tong testers G01R1/22)} - G01R 15/181: {using coils without a magnetic core, e.g. Rogowski coils} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A time varying current sensor is constructed using surface coils uniformly spaced around a central cavity adapted to receive the conductor through which the current to be measured flows. Accurate and uniform coil geometry is achieved using printed circuit board technology, thereby eliminating the high cost of precision toroidal coil winding. An optional hinge in the housing can allow the sensor to be easily installed on existing conductors without the need to disconnect and reconnect. ## Claims ### Claim 1 A current sensor for measuring a time varying current flowing through a conductor, comprising: a plurality of discrete planar insulating substrates substantially equidistant from a central cavity for receiving the conductor, said planar substrates being spaced apart from each other and aligned with angularly spaced planes that are oriented in substantially axial and radial directions relative to the axis of said cavity, and with at least one surface coil having at least one complete turn defined on a single surface of each said substrate, said coils being electrically interconnected such that output voltages of said coils are combined and applied to output terminals of said sensor, wherein at least a plurality of the coils on separate substrates are interconnected with each other with twisted pair wire. ### Claim 2 (depends on 1) A current sensor according to claim 1 wherein each said surface coil comprises a conductive track on the surface of the substrate. ### Claim 3 (depends on 2) A current sensor according to claim 2 wherein at least one surface coil is provided on an opposite surface of the substrate. ### Claim 4 (depends on 3) A current sensor according to claim 3 wherein at least two surface coils on opposite surfaces of the substrate are connected through a via. ### Claim 5 (depends on 2) A current sensor according to claim 2 wherein each said surface coil includes a plurality of nested conductivc turns, of progressively smaller size, one within another, on the surface of the substrate. ### Claim 6 (depends on 5) A current sensor according to claim 5 wherein the amount of substrate area occupied by a turn is very small compared to the area enclosed by said turn. ### Claim 7 (depends on 1) A current sensor according to claim 1 wherein the substrates are all spaced at equal angles. ### Claim 8 (depends on 7) A current sensor according to claim 7 further comprising a housing in which the coils are disposed, the housing being divided into at least two sections, such that said sections maybe spread apart, to allow entry of said conductor into said cavity. ### Claim 9 (depends on 8) A current sensor according to claim 8, wherein the mating surfaces of the two sections are located between substrates, so as to provide a separation distance between the mating surfaces and the coil conductors. ### Claim 10 (depends on 1) A current sensor according to claim 1 wherein the substrates are uniformly spaced at unequal angles, while oriented with symmetry about the axis of the central cavity. ### Claim 11 (depends on 10) A current sensor according to claim 10 further comprising a housing in which the coils are disposed, the housing being divided into at least two sections, such that said sections may be spread apart, to allow entry of said conductor into said cavity. ### Claim 12 (depends on 11) A current sensor according to claim 11, wherein the mating surfaces of the two sections are located between substrates, so as to provide a separation distance between the mating surfaces and the coil conductors. ### Claim 13 A current sensor for measuring a time varying current flowing through a conductor, comprising: a plurality of planar insulating substrate elements substantially equidistant from a central cavity for receiving the conductor, said substrate elements being spaced apart from each other and aligned with angularly spaced planes that are oriented in substantially axial and radial directions relative to the axis of said cavity, and with at least one surface coil having at least one complete turn defined on a single surface of each said substrate element, said coils being electrically interconnected such that output voltages of said coils are combined and applied to output terminals of said sensor, wherein at least a plurality of the substrate elements are integral with each other, being sections of a flexible substrate strip. ### Claim 14 (depends on 13) A current sensor according to claim 13 wherein each surface coil comprises a track on the surface or the substrate strip and electrical interconnections between the coils are defined by tracks on the substrate strip. ### Claim 15 (depends on 14) A current sensor according to claim 14 wherein at least one surface coil is provided on an opposite surface of the substrate element. ### Claim 16 (depends on 15) A current sensor according to claim 15 wherein at least two surface coils on opposite surface of the substrate element are connected through a via. ### Claim 17 (depends on 14) A current sensor according to claim 14 wherein each said surface coil includes a plurality of nested conductive turns, of progressively smaller size, one within another, on the said surface of the substrate element. ### Claim 18 (depends on 17) A current sensor according to claim 17 wherein the amount of substrate area occupied by a turn is very small compared to the area enclosed by said turn. ### Claim 19 (depends on 13) A current sensor according to claim 13 wherein the substrate elements are all spaced at equal angles. ### Claim 20 (depends on 19) A current sensor according to claim 19 further comprising a housing in which the coils are disposed, the housing being divided into at least two sections, such that said sections may be spread apart, to allow entry of said conductor into said cavity. ### Claim 21 (depends on 20) A current sensor according to claim 20 wherein the mating surfaces of the two sections are located between substrate elements, so as to provide a separation distance between the mating surfaces and the coil conductors. ### Claim 22 (depends on 13) A current sensor according to claim 13 wherein the substrate elements are uniformly spaced at unequal angles, while oriented with symmetry about the axis of the central cavity. ### Claim 23 (depends on 22) A current sensor according to claim 22 further comprising a housing in which the coils are disposed, the housing being divided into at least two sections, such that said sections may be spread apart, to allow entry of said conductor into said cavity. ### Claim 24 (depends on 23) A current sensor according to claim 23 wherein the mating surfaces of the two sections are located between substrate elements, so as to provide a separation distance between the mating surfaces and the coil conductors.