Abstract:
A voltage reference selector, used in conjunction with a multi-meter, allows user selection of a reference voltage to be used by the multi-meter from three different reference voltages of an electrical control panel when taking electrical measurements from the electrical control panel via the multi-meter. A portable voltage reference selector can be carried with and electrically connected to a multi-meter and be temporarily electrically connected to voltage reference points of an electrical control panel for taking electrical measurements from the electrical control panel with the multi-meter. In this form, a test lead from the multi-meter is used to obtain electrical measurements from the electrical control panel. A permanent voltage reference selector is permanently connected to voltage reference points of an electrical control panel and is electrically connectable to a multi-meter for taking electrical measurements from the electrical control panel with the multi-meter. In this form, a test lead of the voltage reference selector is used to obtain electrical measurements from the electrical control panel.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to equipment for taking electrical measurements of electrical circuits, components and/or devices of an electrical control panel and, more particularly, to a device for use in conjunction with a multi-meter to aide in the taking of electrical measurement of an electrical control panel. 
         [0003]    2. Background Information 
         [0004]    Industrial control systems and other electrical intensive operations such as manufacturing, use control panels to host electrical components that allow various processes to be automated. The electrical control panel commonly uses terminal blocks primarily to provide termination points between field devices and components within the control panel. During system start-up or troubleshooting electrical engineers and technicians use multi-meters such as digital multi-meters (DMMs) to take voltage readings from the control panel and typically from the terminal blocks. 
         [0005]    When taking electrical measurements of industrial control panel terminal blocks with current style test leads (both modular and non-modular), the engineer or technician must use two hands: one to hold the neutral probe (black in color according to industry standards) and one to hold the positive voltage probe (red in color according to industry standards). Because of this, there are no free hands to hold and/or operate the DMM or to write or take notes. This can create an awkward situation. 
         [0006]    When taking electrical measurements off of an electrical control panel via a multi-meter, it is necessary to provide a voltage reference to the multi-meter from the control panel. Such voltage reference is one of three references, namely, ground, 0 volts DC, and 0 volts AC or neutral. For each reference voltage, it is necessary to connect the reference lead (i.e. black lead) from the “common” terminal of the multi-meter to the appropriate reference voltage on the electrical control panel. The test or positive lead (i.e. red lead) is connected to the volts/ohms/frequency or amps/milliamps terminal of the multi-meter and then contacted to the appropriate point on the electrical control panel. Each time the reference voltage needs to be changed for taking a particular electrical measurement from the electrical control panel, the reference lead must be moved. 
         [0007]    The need to constantly move the reference lead from place to place on the electrical control panel can lead to confusion as to what reference voltage is being tapped or even where is the appropriate place to put the contact. This manner of taking electrical measurements from electrical control panels is also inefficient, thus causing such measurements to take a long time. 
         [0008]    It is evident from the above that there is a need for a device that will enable a user to more efficiently take electrical measurements from an electrical control panel with a multi-meter. 
         [0009]    It is also evident from the above that there is a need for a device that will allow a user to take electrical measurements from electrical control panels with a multi-meter without moving the reference voltage lead. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention is a voltage reference selector, used in conjunction with a multi-meter, that allows user selection of a reference voltage to be used by the multi-meter from different reference voltages of an electrical control panel when taking electrical measurements from the electrical control panel via the multi-meter. 
         [0011]    In one form, the voltage reference selector is portable so that it can be carried with and electrically connected to a multi-meter and be temporarily electrically connected to voltage reference points of an electrical control panel for taking electrical measurements from the electrical control panel with the multi-meter. In this form, a test lead from the multi-meter is used to obtain electrical measurements from the electrical control panel. 
         [0012]    In another form, the voltage reference selector is permanently connected to voltage reference points of an electrical control panel and is electrically connectable to a multi-meter for taking electrical measurements from the electrical control panel with the multi-meter. In this form, a test lead of the voltage reference selector is used to obtain electrical measurements from the electrical control panel. 
         [0013]    The present voltage reference selector is adapted to be connected to three voltage references on the electrical control panel and provides easy switching between the three reference voltages. This allows the user to use one hand to electrically probe (i.e. take electrical measurements from) the electrical control panel while providing one free hand. 
         [0014]    The portable version includes a housing or box with a three position switch. A negative (e.g. black) lead having a multi-meter plug at one end extends from an output of the box and is connectable to the common terminal of the multi-meter. A first input lead (e.g. white lead) extends from the box and is connectable to a zero volts alternating current (0 V AC) reference on the electrical control panel. A second input lead (e.g. green lead) extends from the box and is connectable to a ground (G) reference on the electrical control panel. A third input lead (e.g. blue lead) extends from the box is connected to a zero volt direct current (0 V DC) reference on the electrical control panel. The colors preferably, but not necessarily, comply with the industry standard colors for voltage references. Once the leads are connected, a test or positive lead (e.g. red lead) is used to take electrical measurements from the electrical control panel. The box may include magnets or other temporary attachment mechanism on its underside for temporary attachment to the electrical control panel. 
         [0015]    In the permanent version, the box includes the elements of the portable version with additions. One addition is the inclusion of a positive (e.g. red) lead having a multi-meter plug at one end that extends from the box and connects to the positive terminal of the multi-meter. Additionally, a positive (red) probe extends from the box, is electrically connected to the positive lead, and is used to take electrical measurements from the electrical control panel. The first, second and third input leads (e.g. the white, blue and green leads) are permanently connected to the appropriate voltage reference points on the electrical control panel as indicated above. 
         [0016]    The present invention will be more apparent upon reading the following detailed description in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0018]      FIG. 1  is an isometric view of an embodiment of a voltage reference selector fashioned in accordance with the principles of the present invention and accompanying electrical leads for use with a multi-meter in taking electrical measurements from an electrical control panel; 
           [0019]      FIG. 2  is an isometric view of a portion of an open electrical control panel in which the voltage reference selector and accompanying electrical leads of  FIG. 1  are shown in use with and connected to a multi-meter and to appropriate voltage reference points of the electrical control panel for taking electrical measurements from the electrical control panel by the multi-meter; 
           [0020]      FIG. 3  is an isometric view of another embodiment of a voltage reference selector fashioned in accordance with the principles of the present invention and accompanying electrical leads for use with a multi-meter in taking electrical measurements from an electrical control panel; 
           [0021]      FIG. 4  is an isometric view of a portion of an open electrical control panel in which the voltage reference selector of  FIG. 3  is initially situated before connection to a multi-meter for taking electrical measurements from the electrical control panel, the voltage reference leads of the accompanying leads connected to voltage reference points of the electrical control panel while the test lead of the accompanying leads hangs freely for use; and 
           [0022]      FIG. 5  is an isometric view of the portion of the open electrical control panel of  FIG. 4  with the voltage reference selector thereof situated for use in conjunction with and connected to a multi-meter for taking electrical measurements from the electrical control panel, the voltage reference leads of the accompanying leads connected to the voltage reference points of the electrical control panel while the test lead of the accompanying leads is situated for electrical measurement from a component of the electrical control panel. 
       
    
    
       [0023]    Like reference numerals indicate the same or similar parts throughout the figures. 
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0024]    Referring to  FIG. 1 , there is shown an exemplary embodiment of a voltage reference selector generally designated  10  along with various electrical leads (i.e. accompanying leads) described below fashioned in accordance with the principles of the present invention. As described below, the voltage reference selector  10  is designed for portable use with a multi-meter for taking electrical measurements from an electrical control panel. The voltage reference selector  10  includes a housing, box or enclosure  12  (housing  12 ) that may be made from metal, plastic or other material as desired. The housing  12  carries a switch  14 , here shown as a toggle switch, but may be any type of switch. The switch  14  is a three-input, one output switch such that a selected input is provided to the output. The inputs and output of the switch  14  are internal to the housing  12  and thus are not seen. 
         [0025]    The housing  12  includes a first input jack  16  that is electrically coupled or connected to one switch input of the three switch inputs. Since switch  14  is a toggle switch, the position of the toggle signifies the input selected and thus corresponds to the particular switch input to which the jack is electrically coupled. The first input jack  16  is preferably, but not necessarily, a standard female type jack but may be otherwise if desired. In all cases, the first input jack  16  is provided to releasably receive a plug of an electrical cable (as described below). The first input jack  16  is labeled via the housing as zero volts alternating current (0 V AC) and is thus intended to receive a zero volt AC reference voltage. Preferably, but not necessarily, the first input jack  16  is color coded to differentiate it from the other input jacks and allow quick connection of an input cable thereto. The first input jack  16  is color coded white (and thus per hatching standards is unhatched) as white is the industry standard color for zero volts AC cables. Of course, other colors may be used. 
         [0026]    The housing  12  includes a second input jack  18  that is electrically coupled or connected to one switch input of the three switch inputs. Since switch  14  is a toggle switch, the position of the toggle signifies the input selected and thus corresponds to the particular switch input to which the jack is electrically coupled. The second input jack  18  is preferably, but not necessarily, a standard female type jack but may be otherwise if desired. In all cases, the second input jack  18  is provided to releasably receive a plug of an electrical cable (as described below). The second input jack  18  is labeled via the housing as ground (G) and is thus intended to receive a ground reference voltage. Preferably, but not necessarily, the second input jack  18  is color coded to differentiate it from the other input jacks and allow quick connection of an input cable thereto. The second input jack  18  is color coded green (and is thus hatched accordingly per hatching standards) as green is the industry standard color for ground cables. Of course, other colors may be used. 
         [0027]    The housing  12  includes a third input jack  20  that is electrically coupled or connected to one switch input of the three switch inputs. Since switch  14  is a toggle switch, the position of the toggle signifies the input selected and thus corresponds to the particular switch input to which the jack is electrically coupled. The third input jack  20  is preferably, but not necessarily, a standard female type jack but may be otherwise if desired. In all cases, the third input jack  20  is provided to releasably receive a plug of an electrical cable (as described below). The third input jack  20  is labeled via the housing as zero volts direct current (0 V DC) and is thus intended to receive a zero volt DC reference voltage. Preferably, but not necessarily, the third input jack  20  is color coded to differentiate it from the other input jacks and allow quick connection of an input cable thereto. The third input jack  20  is color coded blue (and is thus hatched accordingly per hatching standards) as blue is the industry standard color for DC cables. Of course, other colors may be used. 
         [0028]    The housing  12  also includes an output jack  21  (see  FIG. 2 ) that is electrically coupled or connected to the switch output. The output jack  21  is preferably, but not necessarily, a standard female type jack but may be otherwise if desired. In all cases, the output jack is provided to releasably receive a plug of an electrical cable (as described below). Preferably, but not necessarily, the output jack  21  is color coded to differentiate it from the other jacks and allow quick connection of an output cable thereto. The output jack  21  is color coded black (and is thus hatched accordingly per hatching standards) as black is the industry standard color for common cable for multi-meters. Of course, other colors may be used. The output jack  21  is thus provided to allow connection to a common input of a multi-meter (as described below). It should be appreciated that the order and/or placement of the various jacks may be changed and that the terms first, second and third are arbitrary. 
         [0029]    In order to allow electrical connection to an electrical control panel, electrical cables are used. A first or 0 V AC cable  26  is provided that is preferably, but not necessarily, color coded white in like manner to and reasons for the first input jack  16 . The first cable  26  has a length of electrical cable  28 , a plug  27  on one end thereof configured for releasable connection to the first input jack  16 , and a plug  29  on another end thereof for preferably, but not necessarily, releasable connection to an electrical probe  30 . The electrical probe  30  is designed to be inserted into a 0 V AC reference point of an electrical panel. 
         [0030]    A second or G cable  32  is provided that is preferably, but not necessarily, color coded green in like manner to and reasons for the second input jack  18 . The second cable  32  has a length of electrical cable  34 , a plug  33  on one end thereof configured for releasable connection to the second input jack  18 , and a plug  35  on another end thereof for preferably, but not necessarily, releasable connection to an electrical probe  36 . The electrical probe  36  is designed to be inserted into a G reference point of an electrical panel. 
         [0031]    A third or 0 V DC cable  38  is provided that is preferably, but not necessarily, color coded blue in like manner to and reasons for the third input jack  20 . The third cable  38  has a length of electrical cable  40 , a plug  39  on one end thereof configured for releasable connection to the third input jack  20 , and a plug  41  on another end thereof for preferably, but not necessarily, releasable connection to an electrical probe  42 . The electrical probe  42  is designed to be inserted into a 0 V DC reference point of an electrical panel. 
         [0032]    In order to allow electrical connection to a multi-meter, an electrical cable is used. A first multi-meter cable  22  is provided that is preferably, but not necessarily, color coded black in like manner to and reasons for the output jack  21 . The multi-meter cable  22  has a length of electrical cable  24 , a plug  23  on one end thereof configured for releasable connection to the output jack  21 , and a multi-meter plug  25  on another end thereof for releasable connection to a multi-meter input jack (see  FIG. 2 ). 
         [0033]    Thus, the electrical input from the probe  30  is provided to the multi-meter cable  22  and thus the multi-meter when the switch  14  is set to select the 0 V AC input, the electrical input from the probe  36  is provided to the multi-meter cable  22  and thus the multi-meter when the switch  14  is set to select the G input, and the electrical input from the probe  42  is provided to the multi-meter cable  22  and thus the multi-meter when the switch  14  is set to select the 0 V DC input. 
         [0034]    It should be appreciated that the length of the cables may be different than shown. Moreover, the style of the plugs and probes may vary accordingly. Additionally, the housing  12  may enclose electronics (not shown) for conditioning, isolating or otherwise electrically connecting the inputs to the switch  14  and/or appropriately providing the inputs to and through the switch and to the multi-meter. 
         [0035]    Referring to  FIG. 2 , the voltage reference selector  10  and accompanying input cables  26 ,  32  and  38  are shown in relation to a portion  110  of an electrical panel  105  having a plurality of terminal blocks  120  for obtaining voltage measurements from the electrical panel  105  via a multi-meter  100 . The housing  12  of the voltage reference selector  10  is positioned proximate the multi-meter  100  which is shown hung (in a manner such as magnets or Velcro®) from the door  115  of the electrical control panel  105 . The housing  12  may include magnets, Velcro® or the like on a rear surface thereof to allow the housing  12  to be releasably attached to the door  115 . The output multi-meter cable  22  is connected to the output jack  21  and to the common input of the multi-meter  100 . The 0 V AC cable  26  is connected to the 0 V AC input jack  16  of the voltage reference selector  10  and to an electrical probe  43  (shown as a different style probe than in  FIG. 1  and not hatched to indicate the color white). The electrical probe  43  is connected to a 0 V AC reference point  54  of the electrical control panel  105 . The G cable  32  is connected to the G input jack  18  of the voltage reference selector  10  and to an electrical probe  44  (shown as a different style probe than in  FIG. 1  and hatched to indicate the color green). The electrical probe  44  is connected to a G reference point  56  of the electrical control panel  105 . The 0 V DC cable  38  is connected to the 0 V DC input jack  20  of the voltage reference selector  10  and to an electrical probe  45  (shown as a different style probe than in  FIG. 1  and hatched to indicate the color blue). The electrical probe  45  is connected to a 0 V DC reference point  58  of the electrical control panel  105 . 
         [0036]    Therefore, by utilizing the switch  14 , the reference voltage supplied to the multi-meter  100  may be quickly changed to one of 0 V AC, G or 0 V DC without having to disconnect a probe from the electrical control panel and reconnecting it to another place on the electrical control panel. The user is then free to use a test lead  48  (color coded red), having a length of electrical cable  50 , a plug  49  on one end thereof connected to a voltage input of the multi-meter and a plug  51  on another end thereof that is coupled to an electrical probe  52 , for taking an electrical measurement of and/or from the electrical control panel  105  such as voltage point  60 . Each time a different voltage point is desired to be measured the probe  52  is appropriately connected or contacted to the voltage point while the switch  14  is set to the appropriate setting. The multi-meter  100  is also set to an appropriate setting. 
         [0037]    Referring to  FIG. 3 , there is shown another exemplary embodiment of a voltage reference selector generally designated  62  along with various electrical leads (i.e. accompanying leads) described below fashioned in accordance with the principles of the present invention. As described below, the voltage reference selector  62  is designed for permanent placement in an electrical control panel and used with a multi-meter for taking electrical measurements from the electrical control panel. The voltage reference selector  62  includes a housing, box or enclosure  64  (housing  64 ) that may be made from metal, plastic or other material as desired. The housing  64  carries a switch  66 , here shown as a toggle switch, but may be any type of switch. The switch  66  is a three-input, one output switch such that a selected input is provided to the output. The inputs and output of the switch  66  are internal to the housing  64  and thus are not seen. The three switch positions are labeled 0 V AC, G and 0 V DC to indicate the three voltage references that may be selected to provide same to the switch output. 
         [0038]    The housing  64  includes a first electrical cable  76  having a length of cable  77  that is electrically coupled or connected to one switch input of the three switch inputs. Since switch  66  is a toggle switch, the position of the toggle signifies the input selected and thus corresponds to the particular switch input to which the cable is electrically coupled. The first cable  76  is preferably, but not necessarily, color coded to differentiate it from the other cables and allow proper connection to the electrical control panel. The first cable  76  is color coded white (and thus per hatching standards is unhatched) as white is the industry standard color for zero volts AC cables. Of course, other colors may be used. The end of the length of cable  77  terminates in bare wire for permanent connection to a 0 V AC reference point of the electrical control panel. 
         [0039]    The housing  64  includes a second electrical cable  78  having a length of cable  79  that is electrically coupled or connected to one switch input of the three switch inputs. The second cable  78  is preferably, but not necessarily, color coded to differentiate it from the other cables and allow proper connection to the electrical control panel. The second cable  78  is color coded green (and thus per hatching standards is hatched) as green is the industry standard color for G cables. Of course, other colors may be used. The end of the length of cable  79  terminates in bare wire for permanent connection to a G reference point of the electrical control panel. 
         [0040]    The housing  64  includes a third electrical cable  80  having a length of cable  81  that is electrically coupled or connected to one switch input of the three switch inputs. The third cable  80  is preferably, but not necessarily, color coded to differentiate it from the other cables and allow proper connection to the electrical control panel. The second cable  80  is color coded blue (and thus per hatching standards is hatched) as blue is the industry standard color for 0 V DC cables. Of course, other colors may be used. The end of the length of cable  81  terminates in bare wire for permanent connection to a 0 V DC reference point of the electrical control panel. 
         [0041]    The housing  64  includes a fourth or test electrical cable  82  having a length of cable  83  that is electrically coupled or connected through the housing  64  to a second multi-meter cable  72  that extends from the housing  64 . The fourth cable  82  is preferably, but not necessarily, color coded to differentiate it from the other cables and allow proper connection to the electrical control panel. The fourth cable  82  is color coded red (and thus per hatching standards is hatched) as red is the industry standard color for voltage test cables. Of course, other colors may be used. The end of the length of cable  83  terminates in a test probe  84  for contact with a voltage measurement point of the electrical control panel. The second multi-meter cable  72  is configured for attachment to a voltage input of the multi-meter and as such includes a length of cable  73  with a multi-meter plug  74  on its end. The second multi-meter cable is color coded red (and thus per hatching standards is hatched) as red is the industry standard color for multi-meter voltage cables. The test cables  82  and  72  provide a pass through of the voltage received by the probe  84  to the multi-meter via the housing  64 . 
         [0042]    The voltage reference selector  62  further includes a first multi-meter cable  68  that is preferably, but not necessarily, color coded black and hatched accordingly. The multi-meter cable  68  has a length of electrical cable  69  and a multi-meter plug  70  on another end thereof for releasable connection to a multi-meter input jack (see  FIG. 4 ). 
         [0043]    Thus, the electrical input from the cable  76  is provided to the multi-meter cable  68  and thus the multi-meter when the switch  66  is set to select the 0 V AC input, the electrical input from the cable  78  is provided to the multi-meter cable  68  and thus the multi-meter when the switch  66  is set to select the G input, and the electrical input from the cable  82  is provided to the multi-meter cable  68  and thus the multi-meter when the switch  66  is set to select the 0 V DC input. 
         [0044]    It should be appreciated that the length of the cables may be different than shown. Moreover, the style of the plugs and probes may vary accordingly. Additionally, the housing  64  may enclose electronics (not shown) for conditioning, isolating or otherwise electrically connecting the inputs to the switch  66  and/or appropriately providing the inputs to and through the switch and to the multi-meter. 
         [0045]    Referring to  FIG. 4 , the voltage reference selector  62  and accompanying input cables  77 ,  79  and  81  are shown permanently mounted in cabinet of the electrical panel  105 . The housing  64  of the voltage reference selector  62  is releasably positioned on an inside wall of the cabinet The housing  64  may include magnets, Velcro® or the like on a rear surface thereof to allow the housing  64  to be releasably attached to the cabinet wall. The 0 V AC length of cable  77  is wired to the 0 V AC voltage reference point  54  of the electrical control panel  105 . The G length of cable  79  is wired to the G voltage reference point  56  of the electrical control panel  105 . The 0 V DC length of cable  81  is connected to the 0 V DC reference point  58  of the electrical control panel  105 . The test length of cable  83  is hung via a hook  65  from the housing  66 . The voltage reference selector  62  is thus installed and awaiting use. 
         [0046]    Referring to  FIG. 5 , the voltage reference selector  62  is shown in use with respect to the multi-meter  100 . The housing  64  is moved proximate the multi-meter  100  and the two multi-meter cables from the voltage reference selector  62  are connected appropriately to the multi-meter. By utilizing the switch  6 , the reference voltage supplied to the multi-meter  100  may be quickly changed to one of 0 V AC, G or 0 V DC without having to disconnect a probe from the electrical control panel and reconnecting it to another place on the electrical control panel. The user is then free to use the probe  84  of the test lead  83  (color coded red), to take an electrical measurement of and/or from the electrical control panel  105  such as voltage point  60 . Each time a different voltage point is desired to be measured, the probe  84  is appropriately connected or contacted to the voltage point while the switch  66  is set to the appropriate setting. The multi-meter  100  is also set to an appropriate setting. Thereafter, the multi-meter is removed, the reference voltage selector  62  put back on the cabinet wall, and the test cable  83  hung back on the hook  65  of the housing  64  to be used again. 
         [0047]    While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.