Abstract:
A method of manufacturing a clamp jaw assembly for a clamp meter is provided. The method includes providing a clamp jaw core and a shield having a channel. The method further includes positioning the clamp jaw core within the channel of the shield such that the shield surrounds a portion of the clamp jaw core. The method also includes enclosing the clamp jaw core and the shield within a clamp jaw housing.

Description:
BACKGROUND 
     A digital multimeter (DMM) is an electronic test instrument that measures electrical current in a wire without the need to electrically isolating the wire. Such multimeters are typically used to measure a variety of electrical parameters, such as voltage, resistance and current. Clamp-type DMMs, also known as “clamp meters”, measure current in a conductor without having to make an electrical connection with a circuit. Instead, such DMMs include two clamp jaws having embedded electrical coils. In use, the jaws are clamped onto a conductor and measure the current within the conductor. 
     If the conductors are bundled together in a tight physical space, such as an electrical cabinet, it is often difficult to insert the clamp meter into the small area to measure an individual wire. As such, it is desirable to size the jaws of the clamp meter to fit within tight spaces. One way to reduce the size of the jaws is to minimize any space between the jaw core and the housing that surrounds the jaw core. However, reducing the space between the housing and the core can lead to safety issues. 
     The international standard for test equipment safety, IEC 61010-1, requires a minimum creepage and clearance path between the outside of the jaw housing and the nearest metallic part or circuit board inside the instrument, which is typically the jaw core. “Clearance” is the shortest distance through the air between two conductive elements. In this case, the first conductive element would be a user&#39;s hand disposed on the exterior of the housing, and the second conductive element would be the core disposed within the jaw. “Creepage” is the shortest distance along the surface of the insulative material between two conductive elements. The interior of the housing and the core are typically separated from each other by air and/or an insulative material. Reducing the air gap or the thickness of the insulative material decreases the overall size of the jaw, but it would also reduce the creepage and clearance path and would violate safety standards. 
     One known solution for reducing the overall size of the jaw of a clamp meter without reducing the clearance and creepage path includes covering at least a portion of the jaw core with an insulating tape. The tape increases the clearance path along the jaw core without adding any distance between the jaw core and the jaw housing. Although effective, the tape needs to be manually applied to the curved surfaces of the jaw core, which is time consuming and difficult to apply. Often the tape is applied unevenly and it can crease or wrinkle when adhered to a curved surface. Creases, wrinkles, and uneven application of the tape can decrease the creepage and clearance path, thereby violating safety standards and putting a user at risk. Accordingly, there is a need for a safe, easy method of increasing the creepage and clearance path in a clamp meter jaw assembly. 
     SUMMARY 
     A method of manufacturing a clamp jaw assembly for a clamp meter is provided. The method includes providing a clamp jaw core and a shield having a channel. The method further includes positioning the clamp jaw core within the channel of the shield such that the shield surrounds a portion of the clamp jaw core. The method also includes enclosing the clamp jaw core and the shield within a clamp jaw housing. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is an isometric view of a clamp meter illustrated in accordance with one embodiment of the present disclosure; 
         FIG. 2  is an isometric view of a clamp jaw assembly of the clamp meter of  FIG. 1  with the clamp meter housing removed for clarity; 
         FIG. 3  is an exploded view of the clamp jaw assembly of  FIG. 2 ; 
         FIG. 4  is an isometric view of the clamp jaw assembly of  FIG. 2 , wherein a portion of the clamp jaw assembly is shown in cross-section; 
         FIG. 5  is a cross-sectional end view of a portion of a prior art clamp jaw assembly; and 
         FIG. 6  is a cross-sectional end view of the clamp jaw assembly of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     A clamp meter  10  constructed in accordance with one embodiment of the present disclosure is best seen by referring to  FIG. 1 . The clamp meter  10  includes a body  14  and a clamp assembly  18  extending from the clamp meter  10 . The body  14  includes a body housing  16  made of a durable lightweight material, such as plastic, and is adapted to enclose typical electrical and mechanical components of the clamp meter  10 . A plurality of input and output components are disposed on the exterior of the body housing  16 , including a plurality of pushbuttons  22  for selecting one or more test functions of the clamp meter  10  and a selector knob  26  for selecting an electrical measurement mode. The clamp meter  10  may further include a display  30  for displaying measurements taken by the clamp assembly  18 . 
     The clamp assembly  18  includes first and second clamp jaws  34  and  38 . The first clamp jaw  34  is mounted at its lower end within the body housing  16  for pivoting movement relative to the second clamp jaw  38  which is fixedly secured within the body housing  16 . The first and second jaws  34  and  38  have an arcuate shape and are adapted to meet at their upper ends to define an enclosed area therebetween for measuring current within a conductor. 
     The first clamp jaw  34  is moveable between open and closed positions by operation of a trigger  42 . The trigger  42  is integrally formed on the first clamp jaw  34 . Depression of the trigger  42  towards the body housing  16  rotates the first clamp jaw  34  about its pivot point away from the fixed second clamp jaw  38  and into the open position. Once the first clamp jaw  34  is in the open or first position, the clamp meter  10  can be manipulated to position the first and second clamp jaws  34  and  38  around a conductor (not shown). The first clamp jaw  34  is preferably spring-biased into the closed position against the second clamp jaw  38  such that the first clamp jaw  34  is maintained in the closed position until the trigger  42  is depressed. 
     As may be best seen by referring to  FIGS. 2 and 3 , the first and second clamp jaws  34  and  38  each include a housing for enclosing internal components. The housing of the first clamp jaw  34  includes a top and bottom housings  46  and  50  securable together in any suitable manner known to one of ordinary skill in the art. Similarly, the housing of the second clamp jaw  38  includes a second clamp jaw top housing  54  and a second clamp jaw bottom housing  58  securable together. The top and bottom housings  46  and  50  of the first clamp jaw  34  and the top and bottom housings  54  and  58  define a first internal cavity  62  and a second internal cavity  66 , respectively. When assembled, the first and second internal cavities  62  and  66  house the internal components of the first and second clamp jaws  34  and  38 . 
     Referring to  FIG. 3 , the internal components of the first clamp jaw  34  include a first jaw core  70 , a first shield  88 , and a flexible printed circuit board (PCB)  100 . The internal components of the second clamp jaw  38  include a second jaw core  74  and a second shield  90 . The first and second jaw cores  70  and  74  are made from electrical coils in a manner well known in the art such that the first and second jaw cores  70  and  74  are adapted to sense the magnetic field created by the current flow in a conductor (not shown) when the first and second jaw cores  70  and  74  are operationally attached to the conductor. 
     The first and second jaw cores  70  and  74  are substantially identical and, therefore, only the first jaw core  70  will be described in detail. The first jaw core  70  is arcuate in shape and includes top and bottom surfaces  72  and  76  (see also  FIG. 6 ), an outer convex surface  78 , and an inner concave surface  82 . The first jaw core  70  further includes an upper transverse end  84  and a lower transverse end  86 . The upper transverse ends  84  of the first and second jaw cores  70  and  74  and the lower transverse ends  86  of the first and second jaw cores  70  and  74  are positionable adjacent one another when the jaw assembly  18  is in the closed position. Although the first and second jaw cores  70  and  72  are described as arcuate in shape, it should be apparent that other geometric shapes, including rectangular, are also within the scope of the present disclosure. 
     The upper and lower transverse ends  84  and  86  of the first jaw core  70  are covered by correspondingly shaped upper and lower end caps  112  and  116 . The upper and lower end caps  112  and  116  are receivable within open ends of the first clamp jaw  34  when the top and bottom housings  46  and  50  of the first clamp jaw  34  are secured to one another. Before being covered with the upper and lower end caps  112  and  166 , the first jaw core  70  is placed into communication with the flexible PCB  100 . The flexible PCB  100  is constructed in a manner well known in the art to provide the appropriate circuitry for detecting electrical properties of a conductor placed within the first and second clamp jaws  70  and  74 . 
     The first and second jaw cores  70  and  74  are receivable within first and second nonconductive shields  88  and  90  to increase creepage and clearance path within the first and second clamp jaws  34  and  38 . The first and second shields  88  and  90  are substantially identical in configuration and, therefore, only the first shield  88  will be described. The first shield  88  includes a first surface  94  extending between first and second sidewalls  96  and  98  to form a channel. The channel of the first shield  88  is sized and configured to receive the first jaw core  70 . More specifically, the first jaw core  70  is received within the channel of the first shield  88  such that the such that bottom surface  76  of the first jaw core  70  is exposed. The second shield  90  receives the second jaw core  74  in a similar manner. 
     The first shield  88  is made from any suitable rigid or semi-rigid, nonconductive material, such as Mylar, rubber, etc. During assembly, the jaw core is simply disposed within the channel of the first or second shield  88  or  90 . This significantly reduces the assembly time. Moreover, there is no opportunity for the first or second shield  88  or  90  to crease, bend, wrinkle, etc., that could happen when using, for instance, insulative tape. 
     Referring still to  FIG. 3 , the top and bottom housings  46  and  50  of first clamp jaw  34  are secured together to enclose the first jaw core  70 , the first shield  88 , and the flexible PCB  100 . A sponge  108  or a leaf spring  104  may be disposed between the exterior of the first shield  88  and the interior of the top and bottom housings  46  and  50  to secure the components within the first clamp jaw  34 . As noted above, the top and bottom housings  46  and  50  may be secured together in any suitable manner. Preferably, however, the top housing  46  includes a male mating portion  120  formed along its edge and the bottom housing  50  includes a corresponding female mating portion  124  formed along its edge. The male mating portion  120  is received within the female mating portion  124  to secure the top and bottom housings  46  and  50  together and to define an interference connection  128  therebetween, as shown in  FIG. 4 . The second clamp jaw  38  is assembled in a similar manner. 
     Operation of clamp jaw assembly  18  having an improved creepage and clearance path  132  may be best understood by referring to  FIGS. 5 and 6 .  FIG. 5  depicts a prior art clamp jaw assembly J having a core C disposed within a housing H. The housing is defined by an upper housing U and a lower housing L that are secured together through a housing connection N. A gap G is defined between the interior of housing H and the core C. The creepage and clearance path P begins on the exterior of the housing H at the housing connection N and extends through the housing connection N and across the gap G until meeting the core C. Thus, if the size of the core C was increased, the gap G would need to increase to ensure a sufficient creepage and clearance path P. Accordingly, an increased core size would increase the overall size of the jaw assembly J. 
       FIG. 6  depicts the creepage and clearance path  132  of the first clamp jaw  34  of the preferred jaw assembly  18 . The creepage and clearance path  132  begins on the exterior of the housing (defined by the top housing  46  and the bottom housing  50 ) at the connection  128  and extends through the connection  128 . The path  132  extends into the interior of the first clamp jaw  34  until it reaches the first sidewall  96  of the first shield  88 . The path  132  is directed downwardly along the first sidewall  96  of the first shield  88  towards the exposed, bottom surface  76  of the first core  70 . The path  132  ends where the first shield is no longer covering the first core  70 . Thus, the first shield  88  lengthens the creepage and clearance path  132  without having to increase the distance between the first core  70  and the interior of the housing. Accordingly, the core size may be increased without having to increase the overall size of the first clamp jaw  34 . 
     While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the present disclosure.