Abstract:
A method and apparatus for configuring a current carrying and current sensing configuration using a rigid magnetically permeable guide core extending between facing first and second guide ends, the first and second ends of the core defining a sensing gap having a sensing dimension therebetween, an internal surface of the core forming a core space, the method including sliding a segment of a conductor through the sensing gap and into the core space such that the conductor extends through the core space, attaching a flux sensor to a clip member and mounting the clip member within the sensing space such that the sensor is within the sensing space.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The field of the invention is Hall effect current sensors and more specifically methods and apparatus for mounting a magnetic field sensor within a gap formed by a core or flux guide that surrounds a conductor. 
     When current passes through a conductor, the current generates a magnetic field including flux that encircles the conductor and that is directed along flux lines in a direction consistent with the well known right hand rule. The field strength is strongest at locations in close proximity to the conductor. The magnitude of current passing through the conductor is directly proportional to the total strength of the magnetic field generated thereby. Thus, if the magnetic flux generated by the current can be accurately determined, then the magnitude of the current passing through that conductor can also be determined. 
     One way to determine the magnetic flux and hence conductor current has been to design a sensor configuration that relies upon the well known Hall effect electromagnetic principle. To this end, in 1879, Edwin Hall discovered that equal-potential lines in a current carrying conductor are skewed when put in the presence of a magnetic field. This effect was observed as a voltage (Hall voltage) perpendicular to the direction of current flow. Today, Hall effect devices for measuring the Hall voltage and hence a corresponding magnetic field are packaged as single Hall effect chips and are sold as high volume commodity items. 
     A typical current sensor utilizing Hall effect technology consists of a toroid or rectangular shaped gapped core and a Hall effect chip. Exemplary cores typically include either a laminated stack or a high resistivity solid ferrite material designed to prevent unwanted eddy currents. A single current carrying conductor is positioned within the core such that the permeable core directs the magnetic flux through the core and across the gap. A Hall effect chip is placed within the gap to sense the flux density passing there across. In a well-designed Hall effect current sensor, the measured flux density is linear and directly proportional to the current flowing through the current carrying conductor. 
     One design challenge routinely faced when designing Hall effect sensors has been finding a cost effective and mechanically robust way in which to mount the Hall effect chip within a core gap. One other challenge has been to configure a sensor that has a relatively small volume footprint. With respect to cost, as with most mechanical products, minimal piece count, less and simplified manufacturing steps and less manufacturing time are all advantageous. In addition, smaller components size typically translates into reduced costs. With respect to robustness, many Hall effect sensors are designed to be employed in rugged environments such as industrial control applications where shock and vibration are routine. 
     The industry has devised several Hall effect sensor configurations. For instance, in one configuration, a donut shaped and gapped ferrite core is positioned over a vertically mounted Hall effect chip which is soldered to a circuit board. In this case the ferrite core is typically manually positioned with respect to the chip and is then glued to the circuit board. While this solution can be used to provide a robust sensor configuration, this solution has several shortcomings. First, sensor manufacturing experience has revealed that it is relatively difficult to accurately position and glue a donut shaped core relative to the circuit board mounted Hall effect chip. Also, in this regard, where the sensor is subjected to vibrations and shock, any loosening or shifting of the bond between the core and board can compromise the accuracy of the current sensor. 
     Second, the manual labor to glue a core to a board is not very efficient or cost effective and the glue curing cycle is typically relatively long. Labor and curing costs increase the overall costs associated with providing these types of Hall effect current sensors. 
     One other approach to mounting a Hall effect chip within a core gap has been to mount the chip on a board, position the core in a housing cavity with the circuit board mounted chip appropriately juxtaposed within the gap, fill the cavity with epoxy potting compound and bake the filled housing for several hours to completely cure the epoxy. As in the case of the glued donut shaped core, the manual labor required to pot the core and board is relatively expensive. Moreover, the baking time required to cure the epoxy reduces manufacturing throughput. Furthermore, the requirement for a housing increases parts count and hence overall configuration costs. 
     Yet one other approach to mounting a Hall effect chip within a core gap has been to mount a circuit board within a bobbin and mount a Hall effect chip to the circuit board where right angle pin connectors from the chip protrude out of apertures in the bobbin for connection to one or more other circuit boards. A core lamination stack is inserted into the bobbin with the bobbin formed to arrange the core and chip with respect to each other such that the chip is within the gap. Thereafter, the bobbin, core, chip and board are inserted into a first piece of a housing with the pin connectors protruding out housing apertures and a second housing piece is snapped together with the first piece to secure all of the components inside. The housed configuration forms a complete Hall effect current sensor. 
     This solution, unfortunately, requires a relatively large number of components and therefore increases costs appreciably. In addition, the pin connectors used with this type of assembly are relatively flimsy and have been known to break when used in typical industrial environments. Moreover, the pin connectors are often bent prior to installation or may be located imperfectly and therefore make installation relatively difficult. Furthermore, if the laminations are not clamped tightly by the housing, the laminations may shift laterally or rotate within the housing due to shock or vibrations. Such shifting and rotation will often result in changing the size of the core gap which alters the sensitivity of the sensor configuration. 
     One constraint on core size is the required dimensions of the conductor that passes through the core. To this end, conductors are typically selected based on the expected maximum steady state current passing through the conductors to ensure that heat generated by I 2 R losses or eddy currents does not cause the conductor temperature to exceed maximum limits defined by UL or IEC specifications. Heat generated by conductor I 2 R losses varies inversely with conductor cross-sectional area and with the square of current. Therefore, if conductor temperature is to be maintained, doubling the current requires a conductor with four times the original cross-sectional area. 
     In addition to current considerations, one other factor that may dictate conductor characteristics is the type of application in which the conductor is employed. For instance, in some applications a conductor may form a bus bar where ends of the bus bar have to have certain dimensions in order to facilitate hookup of other components via common size terminal lugs and mounting hardware that conforms with industry standards. 
     In some soft motor control (SMC) modular applications (e.g., high amp power pole sub-assemblies), bus bars are designed to minimize I 2 R have the largest area possible to facilitate maximum heat dissipation. For instance, where a module footprint is twelve inches by two inches, the bus bar may be designed to be thirteen inches long and two inches wide, the additional inch in length provided so that the bar extends from a module housing for linking to other system components. In such a case the core of a hall effect current sensor must have dimensions that can accommodate the required bus bar width. Thus, in the case of a torroidal core the core diameter would have to be greater than two inches to accommodate the bus bar therein. 
     Unfortunately, in the example above where the module footprint is twelve by two inches, if a core is provided about the bus bar, the core will exceed the module footprint. For instance, assume a core having side or annular members that are ¼ inch thick. In this case, the core about the bus bar would exceed the footprint by ½ inch along the width dimension (i.e., ¼ inch on either side of the width). A couple of ways to deal with this problem would be to increase the module footprint, reduce current levels in the bus bars or change the bar cross-section to square versus rectangular. Unfortunately all of these options severely compromise product size, ease of using standard termination lugs or mounting hardware and limit maximum optimal current levels. 
     A commonly owned patent application filed on even date herewith which is entitled “Snap Fit Hall Effect Circuit Mount Apparatus and Method” teaches one assembly that addresses many of the problems discusses above. To this end, the snap fit concepts in this reference teach a sensor mounted to a resilient clip member where the clip member is securely mountable within a core sensing gap such that the sensor is positioned substantially within the sensing gap. Thus, this solution addresses the problems discussed above with respect to mounting a sensor within a core gap by providing an inexpensive, low-parts count and simple to manufacture and configure assembly. Unfortunately, this solution does not address the other problems discussed above and related to accommodating a bus bar width and core in a relatively small area (e.g., within a small width footprint). 
     Therefore, it would be advantageous to have a simple and inexpensive solution for accommodating a bus bar width and core in a small width footprint without reducing current ratings for the bar or increasing size of the product. 
     BRIEF SUMMARY OF THE INVENTION 
     It has been recognized that a bus bar can be notched along a relatively short segment thereof and on either side such that the notched section and members of a core there around together are within a maximum dimension corresponding to a configuration footprint. In this manner, the wider portions of the bus bar operate as a heat sink for the notched segment and other bar segments and current rating is relatively unaffected. It has also been recognized that by configuring the core so as to have specific dimensions relative to the bus bar the overall size of the bar and core can be minimized and a simple method is facilitated for positioning the core and bar with respect to each other. To this end, generally, the core is formed such that a gap formed thereby is wider than the notched portion of the bus bar and a core space defined by an internal surface of the core is sized to receive the notched core segment so that the notched segment can be manipulated through the gap and into the core space. 
     Consistent with the above description, the present invention includes an apparatus for passing current and sensing magnetic field flux formed by the current, the apparatus comprising a current conductor having a length that extends between first and second conductor ends and first and second edges that extend substantially along the entire conductor length, the edges forming first and second notches at a central conductor segment such that the central segment has a central width dimension that is less than the width dimensions of conductor segments adjacent thereto and a rigid magnetically permeable guide core extending between facing first and second core ends and an internal surface formed about a core space, the first and second core ends defining a sensing gap having a gap dimension therebetween that is greater than the conductor thickness and less than the conductor width, the core including first and second member segments on opposite sides of the core space, wherein the central conductor segment is moveable through the gap and substantially into the core space with the conductor width aligned substantially perpendicular to the gap dimension and the core space is configured to allow the conductor, once substantially in the core space, to be moved into an operating position with the second member segment passing at least partially through the second notch and one of the first member segment and the gap passing at least partially through the first notch. 
     The invention also includes a method for passing current and sensing magnetic field flux formed by the current, the method comprising the steps of providing a current conductor having a length that extends between first and second conductor ends and first and second edges that extend substantially along the entire conductor length, the edges forming first and second notches at a central conductor segment such that the central segment has a central width dimension that is less than the width dimensions of conductor segments adjacent thereto, providing a rigid magnetically permeable guide core extending between facing first and second core ends and an internal surface formed about a core space, the first and second core ends defining a sensing gap having a gap dimension therebetween that is greater than the conductor thickness and less than the conductor width, the core including first and second member segments on opposite sides of the core space, moving the central conductor segment through the gap and substantially into the core space with the conductor width aligned substantially perpendicular to the gap dimension and moving the central segment into an operating position with the second member segment passing at least partially through the second notch and one of the first member segment and the gap passing at least partially through the first notch. 
     These and other aspects of the invention will become apparent from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention and reference is made therefore, to the claims herein for interpreting the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a perspective view of a first Hall effect type current sensor embodiment; 
     FIG. 2 is a perspective view of the clip assembly illustrated in FIG. 1; 
     FIG. 3 is a top plan view of the clip assembly of FIG. 2; 
     FIG. 4 is a side plan view of the clip assembly illustrated in FIG. 2; 
     FIG. 5 is a side elevational view of the guide core of FIG. 1; 
     FIG. 6 is a partial view of one end of the core of FIG. 5 taken along the lines  6 — 6 ; 
     FIG. 7 is a perspective view of a bus bar installed in an operating position relative to the core and sensing assembly of FIG. 1; 
     FIG. 8 is a schematic top plan view of the assembly of FIG. 7; 
     FIG. 9 is a side plan view illustrating one step in a method according to the present invention; 
     FIG. 10 is similar to FIG. 9, albeit illustrating another step in an inventive method; 
     FIG. 11 is similar to FIG. 9 albeit illustrating one other step in an inventive method; 
     FIG. 12 is similar to FIG. 9 albeit illustrating yet one more step in an inventive method; 
     FIG. 13 is a flow chart illustrating an inventive method; 
     FIG. 14 is a side schematic view illustrating a portion of a second inventive method; 
     FIG. 15 is similar to FIG. 14 albeit illustrating a final configuration of the components illustrated in FIG. 14; 
     FIG. 16 is a side schematic view illustrating one step in a third method according to the present invention; 
     FIG. 17 is similar to FIG. 16, albeit illustrating another step in the third method according to the present invention; and 
     FIG. 18 is similar to FIG. 16, albeit illustrating a final configuration of components. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings and, more specifically referring to FIGS. 1 through 12, a first embodiment 10 of the present invention includes, generally, a permeable guide core  12 , a sensor assembly  60  and a bus bar  122 . Core  12  includes a plurality of metallic laminations stacked together to form a substantially “C” shaped core having parallel first and second arm members  16  and  20  (also referred to as first and second member segments), a substantially elongated and straight shoulder member  18  that traverses the distance between adjacent ends of parallel members  16  and  20  (i.e., members  16  and  20  extend in the same direction from opposite ends of member  18  to distal ends) and relatively shorter first and second finger members  14  and  22  that extend from ends of members  16  and  20  opposite member  18  and toward each other and generally form a gap  13 . Members  14  and  22  terminate at distal and facing first and second core ends  25  and  27 , respectively, that form a gap therebetween. Members  14 ,  16 ,  18 ,  20  and  22  together form a core having an internal surface ( 100 ,  101 ,  102  land  103  in FIG. 5) that defines a core space  26 . As seen best in FIG. 7, when in an operating position conductor  122  is positioned so as to pass through space  26 . Core  14  is characterized by a core thickness C t  (see FIG. 6) that corresponds to the combined thickness of the laminates used to construct core  12 . 
     Referring specifically to FIGS. 1 and 5, first and second passageways or recesses  28  and  30  are formed in the first and second ends  25  and  27 , respectively, such that the passageways  28  and  30  form substantially parallel and oppositely facing elongate internal surfaces  36  and  38 , respectively. Each of the internal surfaces  36  and  38  extends generally across the thickness Ct (see FIG. 6 again) of a corresponding end (e.g.,  25 ,  27 ). The facing internal surfaces  36  and  38  generally define a space having a passageway width P w . The space between ends  25  and  27  that is bounded on one side by the conductor core space  26  and bounded on the other side by passageways  28  and  30  will be referred to hereinafter as a sensor core space  29  having a gap width G w . The space between ends  25  and  27  and on a side of passageways  28  and  30  opposite sensor core space  29  will be referred to hereinafter as a circuit core space  31 . Space  31  is illustrated as having the same width G w  as space  29  although this is not a requirement of the invention. As illustrated, gap width G w  is less than passageway width P w . The dimension between passageways  28  and  30  and space  26  must be large enough to accommodate flux sensor  94  when assembly  60  is mounted as illustrated in FIG.  1 . 
     Referring still to FIG. 5, a limit surface  102  formed by the internal surface of shoulder member  18  on a side of core space  26  opposite sensing space  29  and the internal surfaces corresponding to finger members  14  and  22  (e.g., internal surface  103 ) define a core depth Cd that is also defined by the boundary of space  29  that is flush with surface  103  and limit surface  102 . In addition, facing first and second internal surface segments  101  and  100  define a core width C w . A pivot space  104  is located along surface  102  adjacent surface  100 . Space  104  will be described in greater detail below. Each of arm members  16  and  20  has a core girth dimension C g  parallel to the gap width G w . 
     Referring again to FIGS. 1 through 4, assembly  60  includes a clip member  51 , a plug receiving socket  96 , circuit components  100  and a flux sensor  94 . Clip member  51  is a substantially flat and relatively thin lightweight member which is typically formed of some type of circuit board material. Member  51  is generally rectangularly shaped and forms first and second oppositely facing edges  64  and  66  and third and fourth oppositely facing edges  76  and  78  and has first and second oppositely facing sides  92  and  98 , respectively. First side  92  of member  51  is formed in any manner well known in the art for mounting sensor  94  via soldering or some other mounting process. Similarly, second side  98  is constructed and designed to receive various circuit components  100  and also to receive plug socket  96  which, as its label implies, is configured to receive a plug for linking sensor  94  and other circuit components  100  to other circuitry. Sensor  94  and components  100  are operably linked via circuit board runs to socket  96 . In at least one embodiment clip member  51  extends laterally such that when placed within the gap between ends  25  and  27 , a portion is laterally outside the gap. Here, socket  96  (see FIG. 1) may be mounted to the laterally extending portion so that plug  96  resides outside the gap. 
     Clip member  51  forms first and second elongate slots  72  and  74  that are substantially parallel to edges  64  and  66 , respectively, that are closed proximate fourth edge  78  and that are open proximate third edge  76 . With slots  72  and  74  formed as described above, in effect, first and second leg members  68  and  70  are formed that are separated from a body member  62  where leg members  68  and  70  are generally resiliently flexible so that they can be temporarily deformed by pushing inwardly on the distal ends thereof. Hereinafter, the ends of leg members  68  and  70  that are connected proximate fourth edge  78  to body member  62  will be referred to as proximal ends and the unconnected ends of leg members  68  and  70  proximate third edge  76  will be referred to as distal ends. 
     Referring still to FIGS. 2,  3  and  4 , first and second restraining members  84  and  86  extend laterally from the distal and proximal ends of leg member  68  in a direction away from leg member  70 . Similarly, third and fourth restraining members  88  and  90 , respectively, extend laterally and in the same direction from the distal and proximal ends of leg member  70  in a direction away from first leg member  68 . First and second restraining members  84  and  86  have facing surfaces that define a first guide receiving dimension D gr1  where dimension D gr1  is substantially equal to or slightly greater than the guide thickness T g  (see FIG.  6 ). Similarly, third and fourth restraining members  88  and  90  form facing surfaces that define a second guide receiving dimension D gr2  where dimension D gr2  is substantially similar to guide thickness T g . Moreover, referring still to FIG. 3, clip member  51  is dimensioned such that edges  64  and  66  define a clip dimension D clip  substantially equal to the gap dimension D g  illustrated in FIG.  5 . In the embodiment illustrated, the distal ends of leg members  68  and  70  are tapered toward each other so as to form sloped bearing surfaces  80  and  82  which help to facilitate temporary deformation during insertion of member  51  between core ends  25  and  27 . 
     With the core  12  and clip assembly  60  configured in the manner described above with sensor  94  mounted to first side  92 , assembly  60  can be attached within the gap between ends  25  and  27  in the following manner. First, clip member  51  is aligned such that bearing surfaces  80  and  82  are proximate internal surfaces  36  and  38  and, in fact, bear there against. In this case, the edges of surfaces  36  and  38  that surfaces  80  and  82  bear against operate as core bearing surfaces. With clip member  51  so aligned, clip member  51  is forced along a trajectory parallel with passageways  28  and  30  such that force is applied against bearing surfaces  80  and  82  causing leg members  68  and  70  to temporarily flex or deform inwardly toward each other. Eventually, leg members  68  and  70  flex inwardly to the point where restraining members  84  and  88  are forced into and along passageways  28  and  30 . Eventually, restraining members  84  and  88  are forced to the opposite ends of passageways  28  and  30  and extend therefrom. At this point, the deforming force against bearing surfaces  80  and  82  ceases and leg members  68  and  70  resiliently spring back to their original configurations. In this case, edges  64  and  66  are received within passageways  28  and  30  such that restraining members  84  and  86  and  88  and  90  maintain clip assembly  60  within the sensing gap. 
     Referring now to FIGS. 7,  8  and  9 , bus bar  122  (i.e., a conductor) is an elongated metallic member that extends between first and second ends (only first end  145  illustrated). Bar  122  generally has oppositely facing and parallel lateral edges  147  and  149  and, in the illustrated embodiment, has a constant bus bar or conductor thickness BB t  that is less than the smallest dimension within gap  13  (i.e., less than dimension G w ). Proximate end  145  bar  122  forms first and second notches  141  and  143  in edges  147  and  149 , respectively. Each notch  141  and  143  is similarly shaped and is rectangular so that a central segment  152  is formed in bar  122  that has a smaller width dimension CS w  than adjacent first and second bar end segments  150  and  154 , respectively. Thus, as illustrated, each of end segments  154  and  150  have a width dimensions BB w  while central segment  152  has a relatively smaller width dimension CS w . In at least some embodiments widths corresponding to end segments  150  and  154  may be different. More specifically, in at least some embodiments each notch  141  and  143  has a depth N d  (see FIG. 8) that is similar to or slightly greater than the arm member girth C g  (see FIG.  5 ). 
     Importantly, central segment width CS w  and end segment width BB w  are related to dimensions of core  12 . More specifically, end segment width BB w  is substantially similar to the combination of core width C w  (see FIG. 5) and the girths C g  of both arm members  16  and  20  (i.e., BB w =C w +2C g ). In addition, central segment width CS w  is slightly less than core width C w . Moreover, the internal surface of core  12  is formed between the gap  13  and the space occupied by the central segment  152  when in the operating position such that the central segment  152  can be manipulated in some fashion from within the gap into the operating position. Several manipulating processes are described herein but others are contemplated. 
     Furthermore, notches  141  and  143  extend along a central segment length CS l  where, at least in some embodiments, length CS l  is several (e.g., two or more) times as long as core thickness C t . This limitation helps to ensure current is generally passing through central segment  152  parallel to length CS l  when the current passes through a core  12  that is positioned approximately half-way along length CS l  (see FIG.  8 ). 
     Referring to FIGS. 7 and 8, the above described relative dimensions facilitate the juxtaposition illustrated where the central segment width CS w  can be aligned with the core width C w  with arm members  16  and  20  completely received in and passing through the spaces defined by notches  141  and  143 . Thus, the combined width of central segment  152  and core  12  is similar to the width BB w  of end bar segments  154  and  150  and a conductor/sensor configuration results that has a footprint that need not be enlarged to accommodate the core. 
     Referring to FIG. 13, one inventive method  168  according to the present invention is illustrated. Referring also to FIG. 9, at process block  170 , the central segment  152  of bar  122  is moved either along the trajectory indicated by arrow  120  or in some other manner into the position illustrated in FIG. 10 where the first edge  124  of segment  152  is adjacent limit surface  102  of shoulder member  18  with the second edge  126  of segment  152  located within gap  13 . Next, referring also to FIGS. 11 and 13, at block  172 , first edge  124  is moved laterally along limit surface  102  toward surface  100  and into the pivot space (see  104  in FIG.  10 ). As edge  124  is moved toward surface  100 , second edge  126  moves further into core space  26  and to a point where edge  126  will clear the adjacent end of finger member  14  (see FIG.  11 ). This movement is identified by arrow  128  in FIG.  10 . 
     Continuing, at block  174 , second edge  126  is rotated along the trajectory indicated by arrow  132  in FIG. 11 into core space  26 . Thereafter, at block  176 , central segment  152  is moved into its operating position as illustrated in FIG.  12 . Finally, at block  178  sensing assembly  60  is mounted within gap  13  as illustrated in FIG.  12 . 
     Referring now to FIGS. 14 and 15, a second embodiment of the present invention is illustrated. In FIGS. 14 and 15, many of the components are similar or substantially identical to the components described above with respect to the first embodiment and therefore will not be described again here in detail. Components in FIGS. 14 and 15 that are similar to those described above are identified by the same numerals followed by a lower case “a”. For instance, the central segment referenced above by numeral  152  is referenced in FIGS. 14 and 15 by numeral  152   a  whereas the sensing assembly identified by numeral  60  above is identified in FIGS. 14 and 15 by numeral  60   a.    
     Generally speaking, this second embodiment is different than the first embodiment only in that the form of the core  12   a  is different and the core form facilitates a slightly different, albeit similar, method to the method described above for locating central segment  152   a  within core space  26   a . To this end, while core  12   a  still includes a shoulder member  18   a , first and second arm members  16   a  and  20   a  and first and second finger members  14   a  and  22   a , finger member  14   a  is relatively longer than finger member  20   a  such that the internal surface  140   a  of finger member  14   a  is longer than the thickness BB t  of segment  152   a . In addition, the depth C d  of core space  26   a  between facing internal surfaces  140   a  and  102   a  is greater than the width CS w  of central segment  152   a . With core  12   a  so configured, segment  152   a  can be received between surfaces  140   a  and  102   a  such that a second edge  126   a  of member  152   a  is adjacent surface  140   a.    
     In this second embodiment, to position central segment  152  within space  26   a , segment  152   a  is aligned with gap  13   a  and is then slid or moved along the trajectory indicated by arrow  120   a  until first edge  124   a  is adjacent internal surface  102   a . Next, segment  152   a  is moved along the trajectory indicated by arrow  128   a  (see FIG. 14) into the operating position illustrated in FIG.  15 . Thereafter, sensing assembly  60   a  is mounted in gap  13   a  in the manner described above. 
     Referring now to FIGS. 12 and 15, it should be appreciated that the second embodiment illustrated in FIG. 15 results in an assembly where the core width C w  is less than the width required for the embodiment illustrated in FIG.  12 . 
     Referring now to FIGS. 16,  17  and  18 , a third embodiment of the present invention is illustrated. As in the case of the second embodiment, in the case of this third embodiment, many of the components are similar to the components described with respect to the first embodiment and therefore, in the interest of simplifying this explanation, the similar components will not again be described here in detail. In FIGS. 16-18, components that are similar to the components described above are identified by a similar number followed by a lower case “b”. For instance, the central segment in FIGS. 16-18 is identified by numeral  152   b  while the sensing assembly is identified by numeral  60   b.    
     Referring specifically to FIG. 16, in this embodiment, the core  12   b  is annular forming a gap  13   b  and having an internal surface that form a diameter D d  about a core space  26   b . The diameter C di  is greater than the central segment width CS w  of segment  152   b . The internal surface includes a limit surface or segment  102   b  opposite gap  13   b  and opposite segments  100   b  and  101   b  that flank segment  102   b . Again, as above, the thickness of segment  152   b  is less than the smallest dimension across gap  13   b . In this case, to position segment  152   b  within space  26   b , core  12   b  is moved along the trajectory indicated by arrow  120   b  until segment  152   b  is completely within space  26   b  as illustrated in FIG.  17 . Thereafter, core  12   b  can be rotated along the trajectory indicated by arrow  146   b  until the edges  124   b  and  126   b  of segment  152   b  are adjacent opposing surfaces  100   b  and  101   b , respectively, and the segment  152   b  is in the operating position. As illustrated in FIGS. 17 and 18, according to one method, core  12   b  is rotated through approximately 90°. 
     While the first embodiment described above is described as one wherein the central segment  152  is moved and rotated and manipulated with respect to a stationary core  12 , it should be appreciated that the motions described are relative and that, in many embodiments, instead of moving the segment  152  with respect to core  12 , core  12  may in fact be moved with respect to segment  152 . These relative motions are considered equivalent for the purposes of the present invention. 
     It should be appreciated that, while bar  122  is notched down to a smaller width along the relatively short central segment  152 , the remainder of bar  122  is relatively wide (e.g., BB w ) and therefore bar heat is not appreciably increased by the notched segment  141  and  143  and the wide segments  150  and  154  help to dissipate heat that is generated by segment  152  as well as other segments. 
     As discussed above, sensor assembly size is an important design criteria and smaller size is generally desirable. Therefore, while core width C w  is generally dictated by central segment width CS w , to the extent possible core depth C d  should be limited. Clearly, if core space  26  had to facilitate passage of wide end segment  154  or other end  150 , depth C d  would have to be relatively large. Instead of feeding bar  122  lengthwise through core space  26 , it has been recognized that central segment  152  can generally be fed through gap  13  (see arrow  120  in FIG. 9) and into space  26  and that the depth C d  required to facilitate this process is substantially minimized. The term “generally” is used to refer to the process of feeding segment  152  through gap  13  because, in fact, other manipulations are possible. For instance, bar  122  may be fed lengthwise through both gap  13  and space  26  with one edge of end segment  154  extending into and perhaps through gap  13  until central segment  152  is aligned with gap  31  at which point segment  152  may be moved further into space  26 . Other machinations are contemplated to at least reach the point where the first edge  124  of segment  152  is adjacent surface  102  of shoulder member  18  in the intermediate position. 
     It has further been recognized that once segment  152  is in the intermediate position with first edge  124  adjacent surface  102  (see FIG.  10 ), the first edge  124  may be moved (see arrow  128  in FIG. 10) toward the internal surface  100  of member  20  along surface  102  thereby causing second edge  126  to move further into space  26 . Thus, because second edge  126  moves further into space  26  during movement of edge  124  toward surface  100 , central segment width CS w  may actually be greater than core depth C d  (see relative dimensions in FIG. 10) thereby further enabling reduction in depth C d . Once second edge  126  is further inside space  26 , edge  126  can be rotated past the end of finger member  14  (see arrow  132  in FIG. 11) and into space  26 . After approximately 90° of rotation, segment  152  is aligned as illustrated in FIG. 12 with edges  124  and  126  adjacent surfaces  100  and  101 , respectively. Thereafter, sensing assembly  60  can be inserted into space  11  as described above. 
     Referring again to FIGS. 1 through 5, it has also been recognized that the core  12  can be dimensioned such that a single clip  60  and a single sensor  94  can be used to sense currents of various magnitudes. To this end, as well known in the art, sensors like sensor  94  are designed to sense flux within a specific range and, if flux is outside the expected range, the sensor will not operate properly. In most applications the current that will pass through a conductor and to be sensed via the inventive assembly will be within an expected current range that can be anticipated. Also, as well known in the art, the amount of flux passing across a core gap given a specific current passing through a conductor that extends through the space  26  is related to the gap width G w . Given a specific current magnitude, a large dimension G w  reduces the flux passing between ends of core  12  while a smaller dimension G w  increases the flux. 
     Thus, the sensing dimension of core  12  can be changed while employing a single clip/sensor configuration to enable the single clip/sensor configuration to be used to sense various current levels. For instance, given a first relatively low anticipated current magnitude within a first expected current range, a first core having a first relatively small sensing dimension G w  may be employed so that the flux that results across the sensing dimension G w  is within the sensor&#39;s optimal sensing range. Similarly, given a second relatively high anticipated current magnitude within a second expected current range, a second core having a second relatively large sensing dimension G w  may be employed so that the flux that results across the sensing dimension is again within the sensor&#39;s optimal sensing range. 
     Importantly, to employ the same clip/sensor configuration in each of these two exemplary cases and in other exemplary cases for that matter, the gap passageway width P w  formed by each of the cores would be identical. Thus, for instance, referring again to FIG. 5, in the example above, width P w  would be identical for each of the first and second cores while width G w  would be smaller for the first core (i.e., where the expected current magnitude is relatively low) than it would be for the second core (i.e., where the expected current magnitude is relatively high). 
     It should be understood that the methods and apparatuses described above are only exemplary and do not limit the scope of the invention, and that various modifications could be made by those skilled in the art that would fall under the scope of the invention. For example, the present invention may be useful where a single width conductor or bus bar is employed where ends of the bar are already attached to other components. In this case, the core can be manipulated over the bar without requiring detachment. As another example, referring to FIG. 8, instead of providing rectilinear notches  124  and  126 , the notices in the bus bar may be sloped or radiused along edges  141  and  143  and the other facing edges. 
     To apprise the public of the scope of this invention, the following claims are made: