Abstract:
A system and method for measuring current flow through a conductor. The system includes a core having a general ring shape and a central opening. The core terminates at two ends that form a gap for receiving a Hall generator. The core is electrically coupled to a ground to prevent electrical noise on the conductor from being coupled to the Hall generator, thus permitting the direct use of the voltage signal output by the Hall generator.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to sensors for determining a level of current in a conductor, and particularly to a Hall effect current sensor system that is substantially immune to electrical noise. 
     BACKGROUND OF THE INVENTION 
     A variety of sensors are used to measure the amount of current flowing through a conductor. One such example is an open loop Hall effect current sensor. An open loop Hall sensor that measures current flowing through a conductor and provides an output signal proportional to the level of current. Such a Hall effect current sensor can include a gapped, ferrous-based core which surrounds the conductor and a Hall generator. The Hall generator is placed within the gap of the core. 
     Such an open loop configuration is typically susceptible to electrical noise on the conductor. Thus, the accuracy of the Hall generator potentially suffers due to electrical noise on the conductor being indirectly coupled through the core to the Hall generator. 
     The metallic core typically has a significant amount of surface area in parallel with the conductor, and a measurable amount of electrical noise can be capacitively coupled from the conductor to the floating core. Additionally, when a typical Hall generator is positioned in a core gap, the ends of the core have a significant amount of surface area in parallel with the generator. This allows noise on the core to be capacitively coupled to the generator. If the level of noise coupled indirectly from the conductor to the generator (via the core) is significant, the Hall effect current sensor provides an output signal that inaccurately represents the level of current in the conductor. 
     It would be advantageous to utilize an open-loop system in which the Hall generator is substantially immune from direct or indirect electrical noise. 
     SUMMARY OF THE INVENTION 
     The present invention features a system for measuring current flowing through a conductor. The system includes a core having a general ring-shape. The gap within the gapped core is defined by a pair of parallel faces. The core contains a central opening for receiving a conductor therethrough. The system further includes a Hall generator disposed in the gap and a ground. The core is electrically connected to the ground. 
     According to another aspect of the invention, a system is provided for detecting a current level in a conductor. The system includes a metallic core having an opening therethrough. The metallic core further includes a gap extending from the opening to an outer surface of the core. The system also includes at least one conductor extending through the opening, and a sensor disposed in the gap. The sensor cooperates with the core in detecting a current in at least one conductor and outputs a voltage proportional to the current. The system further includes a ground and an electrical connection between the core and the ground. 
     According to another aspect of the present invention, a method is provided for detecting a current level or change in current level in a conductor. The method includes locating a core about a conductor such that the core does not physically contact the conductor. The method further includes placing a gap in the core, and inserting a Hall generator in the gap. The Hall generator is arranged such that it cooperates with the core to output a signal proportional to the current in the conductor. The method further includes electrically grounding the core to provide immunity from electrical noise. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
     FIG. 1 is a side view of an exemplary Hall generator utilized in a preferred embodiment of the present invention; 
     FIG. 2 is a front view of a sensor system according to a preferred embodiment of the present invention; 
     FIG. 3 is a side view of the system illustrated in FIG. 2; and 
     FIG. 4 illustrates an alternate embodiment of the system illustrated in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring generally to FIG. 1, an exemplary Hall generator  10  is illustrated. Hall generator  10  represents a typical embodiment of Hall generator for use in the present invention. Hall generator  10  includes a Hall plate  12  that cooperates with the a Hall substrate  14 . Additionally, Hall generator  10  includes leads  16  designed to carry an output signal in the form of an output voltage that is proportional to the magnetic flux acting on Hall generator  10 , which is proportional to the current passing through the conductor. 
     Hall generator  10  is utilized in a Hall effect current sensor system  18 , as illustrated in FIG.  2 . Sensor system  18  includes a core  20  that is typically formed from a ferrous-based material. Core  20  includes a central opening  22  through which a conductor  24  extends. Core  20  is generally ring-shaped and includes a pair of core faces  26  that are generally parallel to each other across a gap  28 . Ring-shaped includes a variety of shapes including rectangular, U-shaped, and circular. Gap  28  preferably is sized to receive Hall generator  10 , and most preferably is sized such that core faces  26  lie proximate to the Hall generator  10  without contacting Hall generator  10 . As current passes through conductor  24 , a magnetic flux proportional to the current is established in core  20  and sensed by Hall generator  10 . 
     In the illustrated embodiment, core  20  is formed as a ring that has a generally rectangular shape, e.g. square, having four sides  30 . In this embodiment, central opening  22  also is substantially rectangular, e.g. square, and conductor  24  is rectangular, as illustrated. Also, core  20  preferably is formed from a plurality of laminations  32  to form a lamination stack  34 , as illustrated in FIG.  3 . 
     The arrangement of components in the Hall effect current sensor system  18  is selected to minimize electrical noise that can effect the signal output by Hall generator  10 . For example, core  20  is electrically connected to-a ground  36 . Ground  36  can either be a circuit ground or a protective “earth” ground. This grounding of core  20  has no detrimental effects with respect to the magnetic properties or characteristics of the metallic core  20 . However, the grounding substantially reduces or eliminates the effects of electrical noise that can be capacitively coupled from conductor  24  to a floating core, such as core  20 . Absent the grounding to ground  36 , this electrical noise can be capacitively coupled to Hall generator  10  due to the significant amount of surface area that core ends  26  have in parallel with generator  10 . Additionally, Hall generator  10  is made relatively immune to direct electrical noise on conductor  24  by positioning Hall plate  12  and Hall substrate  14  in a generally perpendicular orientation with respect to the electrical fields radiated from conductor  24 . (See FIG.  2 ). 
     Thus, Hall generator  10  is substantially immune from both direct electrical noise on conductor  24  and electrical noise that otherwise would be capacitively coupled from conductor  24  to core  20  and from core  20  to Hall generator  10 . Electrically connected core  20  to ground  36  effectively shunts the electrical noise away from Hall generator  10 . Consequently, sensor system  18  may be designed as an open loop system, illustrated in FIG. 2, because the voltage signal output through leads  16  remains stable and representative of the current passing through conductor  24 . This voltage signal can be used directly by a recipient device  38 . An exemplary recipient device  38  is any device or application for which or in which there is a need to sense or measure current. 
     An exemplary utilization of Hall effect current sensor system  18  is illustrated in FIG.  4 . In this particular implementation, core  20  is mounted to a circuit board  40  by an appropriate mounting structure  42 . Mounting structure  42  preferably holds core  20  generally perpendicular to the circuit board  40 , such that conductor  24  is generally parallel with the circuit board as it extends through central opening  22 . Also, the Hall generator  10  preferably is generally perpendicular to circuit board  40  to help isolate it from electrical noise that results from other components or circuits on board  40 . 
     Circuit board  40  may be designed in a variety of configurations for mounting in numerous devices, such as relays, that require accurate sensing of current level through one or more conductors. In this embodiment, ground  36  typically comprises a circuit ground disposed in or on circuit board  40 . The embodiment illustrated in FIG. 4 shows one of many potential uses and implementations of the unique Hall effect current sensor system  18 . 
     It will be understood that the foregoing description is of a preferred exemplary embodiment of this invention and that the invention is not limited to the specific forms shown. For example, the core may have a variety of configurations and sizes; the Hall generator preferably is centered with respect to the core ends and oriented perpendicular to conductor  24 , but those parameters may be altered; the materials utilized in forming the conductor and core may be varied depending on the specific application; and there may be several different types of recipient devices. These and other modifications may be made in the design and arrangement of the elements described above without departing from the scope of the invention as expressed in the appended claims.