Patent Description:
Current measurements are used in a variety of applications, such as closed loop feedback control of power distribution systems in which a controller operates according to measured currents flowing within a particular circuit. For instance, a switching power supply may be operated so as to regulate an output current, and a feedback loop is formed to provide the power supply controller with an estimate of the output current flowing to a load. Currents flowing through a conductor may be sensed by measuring the voltage across a sense resistor connected in series with the conductor, but this approach requires dissipation of energy through the sense resistor. To overcome this difficulty, magnetic sensor technology has been developed in which one or more sensors are placed near a current-carrying conductor to detect the magnetic field strength, and the amount of current flow is estimated based on the sensed field strength. In certain situations, however, the conductor is located in a machine or other system having significant amounts of magnetic fields unrelated to the current flowing through the conductor. In these conditions, a single magnetic sensor will detect fields associated with the current flow of interest as well as extraneous fields, sometimes referred to as crosstalk. Complicated filtering and signal conditioning circuits can be used to try to separate the signal interest from the crosstalk, but this increases the cost and complexity of the sensor system. Multiple sensor systems have been developed in which a number of magnetic sensors are disposed around the outside of the conductor, with the sensor signals being jointly processed to attempt to cancel the interference for improved current measurement accuracy. However, such multiple sensor techniques are much more costly than single sensor solutions, and occupy a significant amount of space in the area around the conductor of interest. In addition, the magnetic field strength near conductors carrying high amounts of current is often beyond the sensing range of high precision magnetic sensors, and accordingly high accuracy current sensing in these situations has been limited. Consequently, a need remains for improved apparatus and techniques by which cost effective accurate current sensing can be achieved in a compact sensor configuration while mitigating the adverse effects of crosstalk. <CIT> relates to a device, an ammeter and a motor vehicle. Further, <CIT> discloses a method for measuring a current amplitude in a conductor by determination of the magnetic field generated by the conductor. Moreover, <CIT> discloses using magnetic field gradients for potential-free current measurement without voluminous ferrite cores. Besides, <CIT> discloses a measuring device to specify current passing along electrical conductor including magnetic field sensors to measure magnetic field created by current as it passes along the conductor. Further, <CIT> discloses a current sensor for detecting a current flowing in a current line which is a detection object having a structure equipped with a semiconductor substrate having seven longitudinal Hall elements. In addition, <CIT> discloses a current sensor including an electric wire to be measured, a guide portion for guiding the electric wire to be measured and a holding portion for holding the electric wire to be measured.

This provides in situ current measurement apparatus and techniques as well as conductor systems, in which a magnetometer is located inside the periphery of a conductor structure to measure current flowing through the conductor, by which the above-mentioned and other shortcomings of conventional current sensing techniques can be mitigated or avoided.

A sensor interface circuit is provided in the magnetometer to generate at least one output signal or value representing longitudinal current flow in the conductive structure based at least partially on a signal from the magnetic sensor. The magnetometer further includes a plurality of wires electrically connected to the sensor interface circuit and extending outside the outer periphery of the conductive structure. Placement of the magnetometer within the conductor facilitates use of higher sensitivity sensors such as fluxgate sensors, anisotropic magnetoresistive (AMR) sensors, gigantic magnetoresistive (GMR) sensors, a tunneling magnetoresistive or tunneling magnetoresistance (TMR) sensors, etc., due to lower magnetic field amplitude and potentially improved magnetic field uniformity within the outer periphery of the conductive structure. In addition, this magnetometer location technique advantageously reduces the amount of crosstalk sensed by the magnetometer, and occupies less space than the conventional approach of encircling the outside of the conductive structure with magnetic sensors.

The magnetic sensors in certain embodiments are fluxgate sensors including a magnetically susceptible core structure as well as an excitation winding and at least one sense winding formed around the core structure. The sensor interface provides an AC excitation signal to the excitation winding of the individual magnetic sensors and generates at least one output signal or value based at least partially on an individual vector or vector sum of signals received from the sense windings of at least some of the individual one or more or all magnetic sensors.

The individual magnetic sensors in certain embodiments may comprise bridge circuits including at least four resistive elements, in which at least one of the resistive elements is an AMR or GMR sensor element, with the interface circuit providing excitation to the individual bridge circuits and generating the output signal or value at least partially according to a vector sum of signals received from sense terminals of at least some of the individual bridge circuits.

In certain embodiments, a circular sensor can be made with a circular sensing direction. The coils of a circular fluxgate sensor or separate coils without any magnetic core can be used, such as a Rogowski coil with a circular sensing direction transverse to the longitudinal direction of the conductive structure, where the circular sensor surrounds a point along a first side of the magnetometer transverse to the longitudinal direction. Two or more such circular magnetic sensors of different diameters and/or different magnetometer sensor technology may be used in certain embodiments.

The magnetic sensor(s) in certain embodiments may be located in a recess or slot extending inward of a first side of the conductive structure, and the slot in certain embodiments may extend through to a second side of the conductive structure.

In accordance with further aspects of the disclosure, a conductor apparatus includes a conductive structure with at least one circular magnetic sensor located on an integrated circuit at least partially within the outer periphery of the conductive structure.

<FIG> shows a conductor apparatus <NUM> with a conductive bus bar structure <NUM> for conducting current along a longitudinal direction <NUM>. For reference only, the various figures include arrows example indicating X, Y, and Z coordinate axis. The longitudinal extent of the illustrated bus bar <NUM> is generally straight (e.g., along the Z axis), although curved, serpentine, curvilinear or other longitudinal conductor structures <NUM> can be used. In the illustrated example, the bus bar <NUM> includes first and second longitudinal ends <NUM> and <NUM>, respectively, and has a generally rectangular shape with an outer periphery between the ends <NUM> and <NUM> which is defined by a top or first side <NUM>, a bottom or second side <NUM>, and laterally opposite sides <NUM> and <NUM>. The bus bar <NUM> includes a slot <NUM> extending inward of the top side <NUM>, in which a magnetometer or current sensor apparatus <NUM> is positioned. In the illustrated example, the slot <NUM> is rectangular or circular or elliptical, and extends at least partially into the interior of the conductive structure <NUM>. In various possible embodiments, moreover, the slot <NUM> may extend through the conductor <NUM>, for example, including openings in both the top side <NUM> in the bottom side <NUM>, although not a strict requirement of this disclosure. In this regard, other forms of recesses <NUM> may be used by which a magnetometer or magnetic sensor element may be fully or at least partially located within the outer periphery of a conductive structure <NUM>, and such recess may be formed by any suitable technique. In the illustrated example, for instance, the slot <NUM> may be machined into the top side <NUM> of the conductive structure <NUM>, and may be sized to accommodate the magnetometer <NUM> including provision of egress for magnetometer wires <NUM> extending outwardly of the conductive structure outer periphery.

As seen in <FIG>, the magnetometer <NUM> is provided generally near the center of the vertical (X axis) extent and near the center of the lateral (Y axis) extent of the slot <NUM> and of the entire conductive structure <NUM>, although not a strict requirement of this disclosure. As previously mentioned, moreover, the recess <NUM> need not extend all the way through the conductive structure <NUM>, and a recess <NUM> of any suitable location, shape and size can be used by which the magnetometer <NUM> is at least partially situated within the periphery of the conductive structure <NUM>, and which provides external access to the output signal or value of the magnetometer <NUM> via two or more wires <NUM>.

As discussed further below, the magnetometer <NUM> in various embodiments includes one or more magnetic sensors <NUM> positioned at least partially within the outer periphery of the conductive structure <NUM>, such that an associated sensing direction of the sensor(s) is transverse to the longitudinal direction <NUM> of the conductive structure <NUM>. In the various figures, the sensing direction of the sensors <NUM> are indicated using unidirectional arrows for simplicity of illustration, but it will be appreciated that fluxgate sensors, AMR sensors, GMR sensors, TMR sensors, and other magnetic sensors may be bidirectional with the capability of sensing magnetic fields in both directions (e.g., both polarities) along the indicated direction. In this regard, locating the sensor <NUM> in this orientation allows detection and sensing of the amplitude of the magnetic field resulting from longitudinal current flow in the conductive structure <NUM>, where the sensing direction of the individual sensors <NUM> is preferably orthogonal or perpendicular to the longitudinal direction <NUM>, although any transverse orientation is sufficient to sense magnetic field strength. In other words, the magnetic sensors <NUM> are placed such that the sensing direction of the individual magnetic sensors <NUM> is not parallel to the longitudinal direction <NUM> along which current flows in the conductive structure <NUM>. In this manner, the sensor or sensors <NUM> of the magnetometer <NUM> can detect the magnetic field within the periphery of the conductive structure <NUM> and the magnetometer <NUM> can provide one or more output signals or values via wires <NUM> to represent the current flowing through the conductive structure <NUM>.

Referring to <FIG>, the provision of the recess <NUM> and the shape of the conductive structure <NUM> are believed to result in a magnetic field inside of the conductive structure <NUM> which is smaller and more uniform than is the field around the outside of the structure <NUM>. <FIG> illustrates simplified magnetic field contours simulated for a longitudinal rectangular bus bar structure <NUM>, in which three example field strength regions F1, F2 and F3 are illustrated having progressively higher magnetic field strength resulting from conduction of electrical current along the longitudinal direction <NUM> (out of the page with respect to <FIG>). As an example, for a copper bus bar having a lateral width (Y direction) of approximately <NUM> and a vertical height (X direction) of approximately <NUM> connecting a current of <NUM> A DC, the field indicated as F3 in <FIG> at and immediately outward of the bus bar periphery is approximately <NUM>-<NUM> mTesla, and is lower (e.g., approximately <NUM>-<NUM> mTesla) in the region F2 outside of the region F3, with further reduction in the field strength as the distance from the conductive structure <NUM> increases.

However, within the peripheral extent of the conductive structure <NUM>, lower field strength regions exist, including region F2c of approximately <NUM>-<NUM> mTesla (corresponding to a <NUM> A current flow in the bus bar conductor structure <NUM>, wherein different field strength values would be found for different currents). In the illustrated example, still lower field strengths below <NUM> mTesla are found in the region F1c proximate the center slot <NUM>. In particular, it is believed that the magnetic field strength at this internal region F1c is significantly lower than those immediately outlying the outer periphery of the conductive structure <NUM>, and is of considerable uniformity. Consequently, it is believed that location of the magnetometer <NUM> within this region F1c provides significant advantages compared with conventional techniques in which magnetic sensors were located around the outside of the conductor <NUM>. For instance, the lower field strength in the regions F1 facilitates employment of high sensitivity magnetic field sensors <NUM> by which improved current measurement accuracy can be achieved without saturating the sensors <NUM>. Furthermore, positioning the sensors <NUM> in the interior of the conductor periphery minimizes or reduces adverse effects of crosstalk associated with other sources of magnetic fields near the conductive structure <NUM>. As seen in <FIG>, moreover, for a symmetrical structure such as the illustrated bus bar <NUM>, the recess <NUM> is advantageously provided near the lateral center of the structure <NUM>, although not a strict requirement of this disclosure. For instance, the recess <NUM> and magnetometer <NUM> can advantageously be located laterally outward of the center (e.g., to the left or right of the region F1c in <FIG>) for operation to sense magnetic fields corresponding to current flow in the conductive structure <NUM> using sensors that might otherwise saturate if placed in the higher field strength region F3 on the outside of the conductor periphery.

It is believed that the shape and geometry of the conductive structure <NUM>, as well as that of the recess <NUM> can be used to shape the magnetic field profile within the periphery of the conductive structure <NUM>. Thus, for instance, different recess shapes and sizes or multiple recesses may be used to tailor the magnetic field strength and/or uniformity for the location in which the magnetometer <NUM> is to be positioned within the bus bar <NUM>. In this regard, the illustrated generally rectangular slot type recess <NUM> at the center is believed to provide a generally circular interior region F1c at and near the centroid of the conductive structure <NUM>. In this regard, different embodiments of the conductor apparatus <NUM> may include multiple recesses <NUM> and corresponding magnetometers <NUM>, for example, an integer number magnetometers <NUM> situated in corresponding recesses. For a given design, moreover, the location and geometry of recesses or slots <NUM> in the conductive structure <NUM> can be designed in consideration of any corresponding thermal and other effects on the current density in neighboring portions of the conductive material <NUM>.

As seen in <FIG>, the magnetometer <NUM> in certain embodiments is a relatively small integrated circuit-based structure having one or more magnetic sensors <NUM> and wiring <NUM> for providing power to the magnetometer <NUM> as well as for providing configuration settings and output signals to external devices (not shown). In one possible example, an integrated circuit magnetometer <NUM> can be fabricated to a relatively small size of approximately <NUM> square x <NUM> thick for location within a correspondingly small slot or recess <NUM>, whereby the creation of a slot or other recess <NUM> need not be a significant departure from the overall current carrying capability of the conductive structure <NUM>. In this respect, the indication in <FIG> of the relative sizes of the slot <NUM> and the magnetometer <NUM> are not necessarily drawn to scale, wherein certain embodiments are possible in which the lateral (Y direction) extent of the slot <NUM> generally corresponds to that of the magnetometer <NUM>, and the same may be true of the vertical (X direction) extents of the slot <NUM> and the magnetometer <NUM>. Moreover, multiple magnetometers <NUM> may be positioned within a given recess or slot <NUM>, for example, to provide redundant sensors in case one magnetometer <NUM> becomes inoperable.

In addition, while the simple example of a machined slot <NUM> is illustrated and described, other forms of recesses are possible, and embodiments are contemplated in which a magnetometer <NUM> is at least partially embedded within the conductive structure <NUM> by any suitable fabrication techniques. For instance, upon installation of the magnetometer <NUM> within the machined slot <NUM> in the illustrated examples, one or more types of filler materials may be introduced into the recess <NUM>, for example, to effectively encapsulate the magnetometer <NUM> while leaving parts of the wiring <NUM> extending outward of the conductive structure <NUM>, where such filler material may in certain embodiments be designed to be electrically isolating and/or thermally conductive to facilitate removal of heat from the area around the magnetometer <NUM>.

<FIG> show various illustrative embodiments of the current sensor apparatus (magnetometer) <NUM>, including various integrated circuit implementations in which one or more magnetic sensors <NUM> are formed at least partially on or in a single semiconductor substrate <NUM> (e.g., silicon) in a pattern to at least partially surround a point <NUM> along a first side of the substrate <NUM>. The illustrated magnetometers <NUM> may be installed within a slot or recess <NUM> of the illustrated conductive structures <NUM> such that the point <NUM> on the substrate <NUM> is located along the longitudinal direction <NUM> within the outer periphery of the conductive structure <NUM> into which the magnetometer <NUM> is installed, as seen in <FIG> above. In this manner, the pattern of magnetic sensors <NUM> generally surround or encompass a point along the longitudinal direction <NUM> that which current is to be sensed, with a first side or face of the magnetometer <NUM> preferably being generally normal to the longitudinal direction <NUM>, although transverse orientations other than strictly normal or perpendicular may be used.

In practice, any suitable type or form of magnetic sensors <NUM> can be used, including without limitation fluxgate sensors, AMR sensor elements, GMR sensor elements, TMR sensor elements, Rogowski coil structures or other circular magnetic sensors (e.g., AMR, CGM, TMR), etc., by which magnetic fields can be sensed to generate one or more output signals or values via the circuitry <NUM> representing current flow within the conductive structure <NUM>. Any suitable interface circuitry <NUM> can be used which generates one or more output signals or values based at least partially on signals from the magnetic sensor(s) <NUM>. In this regard, the circuitry <NUM> in certain embodiments provides an analog signal representing an individual vector or vector sum of the signals from at least one of the sensors <NUM>. In other possible implementations, the circuit <NUM> may include analog to digital conversion circuits, and may optionally include further logic including programmable or programmed processing elements, in order to provide a digital value representing an individual vector or vector sum of the signal(s) from the sensors <NUM>, and thus indicative of sensed current flowing through the conductive structure <NUM>.

<FIG> and <FIG> illustrate further example integrated circuit-based magnetometers <NUM> in which one or more circular sensors <NUM> are used. In this regard, the sensors <NUM> may be any suitable magnetic sensor having a generally circular sensing direction extending at least partially around the center point <NUM>. The circular magnetic sensors <NUM> may include at least one Rogowski coil, circular fluxgate sensor, circular anisotropic magnetoresistive (AMR) sensor, circular gigantic magnetoresistive (GMR) sensor, a tunneling magnetoresistive (TMR) sensor, or circular Hall sensor in certain embodiments. In this regard, a Rogowski coil structure <NUM> can be provided on and/or in a semiconductor substrate <NUM> by successively providing toroidal windings encircling a magnetic core structure formed on and/or in the substrate <NUM>, for example, with initial turns on a first or upper side of the substrate, and return windings on a second or lower side of the substrate <NUM>. In these examples, the interface circuitry <NUM> may include any suitable circuitry for providing an output signal representing the current flowing through the conductive structure <NUM>, for example, with electrical connection of the toroidal windings being provided to an integrated circuit (not shown) to generate a voltage output signal (or a digital value) indicative of the current flowing through the conductive structure <NUM> when the magnetometer <NUM> is installed in the recess <NUM> as described above. In the embodiment of <FIG>, a single circular sensor structure <NUM> is provided, whereas the example of <FIG> includes first and second circular sensors <NUM>, each encircling the center point <NUM>, with different diameters and/or different magnetometer sensor technology. This embodiment may be used, for example, with corresponding dual range interface circuitry <NUM> such that a first signal or value is provided based on the output of the first sensor <NUM>, and a second signal or value is provided based on the output of the second sensor <NUM>.

<FIG> illustrates a portion of an example magnetometer structure <NUM> in which fluxgate magnetic sensors <NUM> are used, wherein only two example sensors are shown. As seen, the individual fluxgate sensors <NUM> include a magnetically susceptible core structure <NUM>, such as may be formed on and/or in a semiconductor substrate <NUM>, along with a pair of excitation windings <NUM> and <NUM> and a centrally located sense winding <NUM>, where the windings <NUM>, <NUM> and <NUM> are formed around a corresponding portions of the core structure <NUM>. Any number of sense windings and excitation windings may be used in different embodiments. In this example, moreover, the magnetically susceptible core structure <NUM> includes two longitudinally opposite gaps <NUM> separating bilaterally symmetrical core portions 130a and 130b. Other other designs are possible in which no gap <NUM> is used, or a single gap may be provided, or more than two such gaps <NUM> may be included in the core structure <NUM>.

In operation, the excitation circuit <NUM> provides an AC excitation signal 127e to the excitation windings <NUM> and <NUM> associated with each of the sensors <NUM>, and the sensing circuitry <NUM> provides at least one output signal or value based at least partially on a vector sum of sensor signals <NUM> received from the sense winding <NUM> of all or at least some of the individual magnetic sensors <NUM>. As AC excitation current is provided to the excitation windings <NUM> and <NUM>, the core structure <NUM> is alternatively driven through magnetic saturation and demagnetization, thereby inducing an electrical current flow in the sensing coil <NUM>. When the core structure <NUM> is exposed to a magnetic field, such as caused by current flow within the bus bar conductive structure <NUM> (<FIG>), the core structure <NUM> is more easily saturated in alignment with that field, and less easily saturated in opposition to it. As a result, the induced sense coil current will be out of phase with the excitation current, and the difference will be related to the strength of the external magnetic field. In one possible implementation, the excitation and sensing (interface) circuit <NUM> includes an integrator circuit providing an analog output voltage proportional to the sensed magnetic field along the corresponding sensing direction of a given fluxgate magnetic sensor <NUM>. In addition, the circuitry <NUM> may include analog and/or digital processing components (not shown) to generate at least one output signal or value based at least partially on a vector sum of the integrals of the signals <NUM> received from the sense windings <NUM>.

Referring now to <FIG>, the magnetic sensors <NUM> in certain embodiments may comprise bridge circuits having at least four resistive elements, where at least one of the resistive elements is an anisotropic magnetoresistive (AMR) sensor or a gigantic magnetoresistive (GMR) sensor or a tunneling magnetoresistive (TMR) sensor. As seen in <FIG>, for example, each of the illustrated sensors <NUM> includes a bridge circuit with resistive elements R1, R2, R3 and R4, at least one of which is an AMR or GMR element or sensor. AMR elements can be made, for example, by deposition of a permalloy (e.g., nickel-iron) thin film on a semiconductor substrate <NUM>, and patterning thereof into a resistive strip as shown. In practice, the electrical resistance of such an AMR element changes by a certain percentage based on the presence of a magnetic field in the indicated sensing direction, and one or more of these AMR resistor elements may be connected in a Wheatstone bridge to measure the magnitude of the magnetic field along the sensing direction. GMR type sensor elements may be constructed on and/or in the semiconductor substrate <NUM> by formation of upper and lower ferromagnetic alloy layers, (such as PZT, etc.) above and below an ultrathin nonmagnetic nonmagnetic conducting metal layer (e.g., copper), with electrical connections to two longitudinally opposite ends of the sandwich structure (not shown). One or more of these elements can be connected in a bridge circuit as shown in <FIG> to form a sensor <NUM> with a corresponding sensing direction. As with the AMR embodiments, the excitation and sensing circuitry <NUM> in certain embodiments provides one or more excitation signals 127e to the resulting bridge circuit of the individual magnetic sensors <NUM>, and generates at least one output signal or value based at least partially on an individual vector or vector sum of signals <NUM> received from sense terminals of the individual one or more or all bridge circuits.

This disclosure thus provides a variety of magnetometer configurations and constructions by which one or more magnetic sensors <NUM> can be embedded or otherwise placed within the outer periphery of an electrically conductive structure <NUM> for sensing current flow therein. These concepts advantageously minimize the amount of physical space occupied by the sensing apparatus, and also reduce or avoid adverse effects of crosstalk in sensing current flow due to placement of the magnetic sensors <NUM> within the periphery of the conductive structure and by forming the sensors <NUM> in a pattern at least partially surrounding a point along the longitudinal direction <NUM> of the conductive structure <NUM>.

The disclosure also contemplates methods and apparatus for sensing current along a longitudinal direction <NUM> of a conductive structure <NUM>, including location or positioning of a magnetometer <NUM> comprising a plurality of magnetic sensors <NUM> within an outer periphery of the conductive structure <NUM> such that the sensing directions of individual magnetic sensors <NUM> are transverse to the longitudinal direction <NUM> and such that the sensors <NUM> form a pattern to at least partially surround a point <NUM> along the longitudinal direction <NUM>. In addition, the sensing methods include generating at least one output signal or value representing longitudinal current flow in the conductive structure <NUM> at least partially according to an individual vector or vector sum of signals <NUM> received from the magnetic sensors <NUM> using a sensor interface circuit <NUM> of the magnetometer <NUM>.

In addition, this disclosure contemplates novel current sensor apparatus <NUM> as shown above, including a semiconductor substrate <NUM> with at least two magnetic sensors <NUM> formed to have an associated sensing direction generally parallel with a first side of the semiconductor substrate <NUM>. The magnetic sensors <NUM> are formed at least partially on or in the substrate <NUM> in a pattern to at least partially surround a point <NUM> along the first side of the semiconductor substrate <NUM>. The sensor apparatus <NUM> further includes a sensor interface circuit <NUM> also formed on or in the substrate <NUM> to generate one or more output signals or values based at least partially on signals from the magnetic sensors <NUM>, as well as a plurality of wires <NUM> electrically connected to the sensor interface circuitry <NUM>. As noted above, relatively small current sensing apparatus or magnetometers <NUM> can be created using fluxgate sensors <NUM>, AMR or GMR sensor elements in a bridge circuit, or even a single or multiple circular sensors such as Rogowski coils <NUM> formed on or in an integrated circuit substrate <NUM> with corresponding interface circuitry <NUM> and wiring <NUM> to provide a relatively small structure. These devices <NUM>, moreover, can be easily inserted into a slot or other recess of a conductive structure <NUM> for high resolution and accuracy in measuring current flowing through the structure <NUM> while minimizing the amount of physical space taken up by the sensing apparatus and reducing or avoiding adverse effects of crosstalk.

Claim 1:
A conductor apparatus (<NUM>), comprising:
a conductive structure (<NUM>) operative to conduct current along a longitudinal direction, the conductive structure (<NUM>) comprising an outer periphery extending between first and second longitudinal ends (<NUM>, <NUM>); and
a magnetometer (<NUM>), comprising:
an array of at least two magnetic sensors (<NUM>) located on a single integrated circuit at least partially within the outer periphery of the conductive structure (<NUM>),wherein the magnetic sensors (<NUM>) include a circular sensor having an associated circular sensing direction transverse to the longitudinal direction of the conductive structure (<NUM>), and wherein the circular sensor surrounds a point (<NUM>) along a first side of the magnetometer (<NUM>) transverse to the longitudinal direction of the conductive structure, wherein the circular sensor is a first circular magnetic sensor (<NUM>) and the magnetometer (<NUM>) further includes a second circular magnetic sensor (<NUM>), the first and second circular sensors (<NUM>) individually having an associated circular sensing direction transverse to the longitudinal direction of the conductive structure (<NUM>) and individually surrounding the point (<NUM>) along the first side of the magnetometer (<NUM>), wherein the first and second circular sensors (<NUM>) are concentric of different diameters,
a sensor interface circuit (<NUM>) operatively coupled to the magnetic sensors (<NUM>) to generate at least one output signal or value representing longitudinal current flow in the conductive structure (<NUM>) based at least partially on at least one signal from the magnetic sensors (<NUM>), and
a plurality of wires (<NUM>) electrically connected to the sensor interface circuit (<NUM>) and extending outside the outer periphery of the conductive structure (<NUM>).