WO1987007730A1

WO1987007730A1 - Cable continuity checker

Info

Publication number: WO1987007730A1
Application number: PCT/US1987/001180
Authority: WO
Inventors: Michael P Caldwell
Original assignee: Hughes Aircraft Co
Priority date: 1986-06-05
Filing date: 1987-05-21
Publication date: 1987-12-17
Also published as: EP0271524A1

Abstract

A fixture is provided for checking the continuity of a cable having wires running between terminals in two end connectors. The cable is designed so that a single path is provided by each wire and its associated terminals. The connectors are plugged into mating receptacles on the fixture which also includes an array of associated light emitting diodes and an array of pins. The user touches the stylus of a manually movable probe against each pin. Only the associated light emitting device will be energized if there is good continuity for a given path in the cable. Non energizing of the associated device or energizing any other device indicates a lack of continuity and the source thereof.

Description

CABLE CONTINUITY CHECKER
BACKGROUND OF THE INVENTION
Technical Field
This invention relates to equipment used for quality control purposes and, more particularly, to an apparatus for checking electrical cables.

Background
Electrical cables are used in a wide variety of different applications. Cables are generally characterized by a group of wires coupled at opposite ends to opposing connectors by terminals. The wires typically take the form of an electrically conductive flexible metallic core or rod which is wrapped in an insulating jacket. It is commonplace for a cable to have many wires bound together in a flexible sleeve. Some cables can contain over 100 different wires. In many applications it is important that the integrity of each wire is maintained between a terminal on one connector and its associated terminal on the opposite connector.

In other words, there can only be one electrically conductive path between the two terminals in the opposite connectors. It can be appreciated that if continuity is not maintained then it is possible for signals to be erroneously transmitted over the cable to undesirable destinations. In some cases, a wire may fray at the connector and the frayed strands will make contact with a nearby terminal. In other cases, the terminal does not in fact make good contact at a connector. Sometimes, heat generated in the wires will cause the insulation to melt and wires become shorted. Of course, it is also important that there are no broken wires in the cable; otherwise, no signal at all will be delivered to any destination. As a result, it has been general practice to perform some type of quality control to check the continuity of cables.

Cable continuity, meaning the presence of only one uninterrupted electrical conductive path for each wire and its associated terminals in the cable connectors, is obviously a critical requirement.

Unfortunately, the testing of cable continuity has been a time consuming and burdensome task and therefore costly. One commonly used approach is for -quality control personnel to use a volt-ohm meter or the like in which each terminal on one connector was
checked against every terminal in thd opposite connector to make sure that there is only one good signal path
for that given wire. Then, the user would go to the next pin and check it against all of the pins in the
opposite connector. This process is continued for each pin in the connector. Obviously such a technique can
be extremely time consuming especially where there are
a number of different wires in the cable.

SUMMARY OF THE INVENTION
Pursuant to the present invention, a fixture is
provided that enables the user to quickly and easily
check cables for proper continuity. The fixture in
cludes two receptacles, one for each connector of the cable. Means are provided for testing the continuity of the wire terminal paths in the cable and providing a visual output which is a function of the continuity of each path. In the preferred embodiment, the fixture includes a first array of light emitting devices and a second array of pins which correspond to the wires in the cable. A manually movable probe is used to touch each pin. If there is continuity for the path then only one associated light remitting device will be energized. Non energizing of the associated device or energizing any other device indicates a lack of continuity and the source thereof.

BRIEF DESCRIPTION OF THE DRAWINGS
The various advantages of the present invention will become apparent to one skilled in the art by reading the following specification and by reference to the drawings in which:
FIG. 1 is a perspective view of a fixture made in accordance with the teachings of the present invention; and
FIG. 2 is an electrical schematic diagram of a fixture of the type illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT
Turning now to the drawings, a fixture 10 is provided for testing the continuity of a cable 12. Cable 12 includes a male connector 14 and a female connector 16. As best shown in FIG. 2, the male connector 14 includes a plurality of terminals such as pins 18(a-e) which are connected to one end of wires 20(a-e) schematically illustrated by the dotted lines within flexible sleeve 22. Each wire 20 consists of an electrically conductive flexible core or rod 24 surrounded by an insulating jacket 26 throughout much of its length.

The opposite ends of the wires 20 are connected to respective terminals such as sockets 28(a-e) in female connector 16. It should be noted that the number of wires and configuration of the connectors can vary considerably and have been greatly simplified in the drawings to make the explanation of this invention easier to understand.

Cable 12 is designed so that there is only one electrical conductive path between associated terminals in the connectors. For example, there should be only one signal path between terminal pin 18d in connector 14 to terminal socket 18d in connector 16. If, however, there is an electrical short between one or more of the wires 20 then this can result in an undesirable "extra" electrically conductive path through the cable for any given wire. For example, this can result in a situation where a signal applied to terminal 18d can "branch" through the shorted wires and be delivered to two or more of the terminals 28 whose wires have been shorted together. The fixture 10 and method of using it according to the present invention is designed to check for these undesirable cable conditions, as well as for broken wires.

The fixture 10 generally consists of a box-like housing 30 having a major upper surface 32 and opposing sides 34, 36. The fixture may be designed to be handheld. On one side a female receptacle 38 is located for receiving male connector 14. (See FIG. 2) The opposite housing side 36 has a male receptacle 40 mounted thereto for receiving female connector 16 as seen in FIG. 1 as well as in FIG. 2.

Fixture 10 is provided with an array of light emitting devices 42 such as light emitting diodes (LEDs) that are preferably arranged in a given geometrical pattern. There is one LED for each wire 20 and path in the cable 12. Additionally, the array of LEDs may be arranged in a geometrical pattern that corresponds with the geometrical pattern of the terminals on connector 14. Suitable indicia such as the alphanumeric labels shown in FIG. 1 are provided on the fixture to provide the user with a correlation between each LED and its associated connector terminal. Thus, the LED array in
FIG. 1 is shown in a rectangular pattern to correspond with the rectangular pattern of male terminals 18 in connector 14.

A second array of electrically conductive contacts in the form of pins 44 is provided adjacent to the LED array; here, one pin 44 is located above an associated LED 42 on housing surface 32.

Attention should now be drawn to the electrical schematic diagram of FIG. 2. Receptacle 38 is provided with a plurality of female sockets 46(a-e) for receiving the male pins of connector 14. Each socket terminal is electrically connected to the anode of one of the LEDs 42. Thus, there is a one-to-onO relationship between the LEDs, terminals in the connectors, the wires and thus each path in the cable. The cathodes of all of the LEDs are connected together at a common node 48.

Node 48 is connected in series with a buzzer 50, power switch 52, battery 54 and a probe 56 having a stylus 58. Because LEDs are used, the power source may be kept small, whereby the overall fixture size and shape can be adapted for portability and for hand-holding. A separate on/off switch 60 for the buzzer 50 is also provided in this embodiment. Each of the pins 44 is electrically connected in a one-to-one relationship with the terminal pins 62(a-e) of receptacle 40.

The method of using fixture 10 will now be described. The connectors 14 and 16 of the cable 12 are mated together with their respective receptacles 38 and 40. The power switch 52 is turned on and the user may optionally elect to arm the buzzer by appropriately moving switch 60. Then all the user needs to do is to touch the probe stylus 58 to each pin 44. If there is good continuity for a given path which provides a single path between connector terminals then only the associated
LED 42 (the one below the pin 42 being touched) will be energized. Otherwise, another LED will be lit or two or more LEDs will be lit thereby indicating to the user that there is a lack of continuity in that particular path in the cable (e.g. that a short with the other indicated wire or terminal has ocurred).

If no LED is lit this means that there is a broken signal path between connector terminals for that wire.

-With the probe stylus in the position illustrated in FIG. 2 it can be appreciated that the fixture 10 completes an electric circuit between the opposite ends of wire 20d. Beginning with terminal 18d of connector core or rod 24 through the middle sheath portion 22 to female terminal 28d in connector 16; then through terminal pin 62d in receptacle 40 through pin 42d which projects from the top surface 32 of the fixture 10.

The circuit then passes through the probe stylus 58 to battery 54 then through switches 52 and 60 (which is shown in FIG. 2 as shorting out buzzer 50 thereby inactivating it) and then to node 48. From node 48 the circuit is completed through LED 42d and terminal 46d back to terminal 18d to which it is mated. Thus, it can be seen that only one LED is lit when there is only one electrically conductive circuit path between the one terminal at one end of the wire and the other. Assume, for example, that there is a short between wires 20d and 20e, i.e., the electrically conductive rods of these two wires are touching. Under these circumstances there is established two current paths - through LEDs 42d and 42e - thereby lighting both of them.

The user can observe this phenomena when viewing the array of
LEDs and since each LED is associated with a given wire it is possible for the user to detect which wires are shorted together. Likewise, if there is a broken wire then no LED will be energized because the wire will fail to complete the necessary circuit for any
LED to be lit.

It can further be seen that in operation the stylus can be rapidly moved from pin to pin and so long as continuity is present for each path, only the one associated LED for each pin will be lit. To the eye of the tester, the pattern of LEDs will appear as a uniform line of LEDs being sequentially lit. A lack of continuity will appear as a blatant irregularity in the light pattern, providing a quick and inexpensive cable continuity check. Further, by observing which of the LEDs are lit, a user can readily deduce the probable source and cause of the improper continuity condition.

The geometrical pattern for indicating proper/improper continuity can be varied depending on the choice of the designer. By inclusion of the LED's or other low power visual display means, the power requirements for the fixture may be kept low. As a result, the fixture may be designed to be hand-held and portable so that the test routine can be performed without elaborate or expensive equipment.

From the foregoing description it can be appreciated that the task of checking the continuity of wires in cables has been made considerably easier by way of this invention. All the user needs to do is to plug in both ends of the cable to the fixture and sequentially touch each of the pins 44 with the probe stylus 58 while observing the LEDs 42 adjacent to the pins on the fixture. Those skilled in the art can appreciate that other advantages can be obtained from the use of this invention and that modifications can be made without departing from the true spirit of the invention after studying the specification, drawings and following claims.

Claims

What is Claimed is: 1. A method of testing for the continuity of a cable having wires running between terminals in connectors at opposite ends thereof, the cable being designed so that a single path is provided by each wire and its associated terminals in the connectors, said method comprising: plugging the connectors into first and second receptacles, respectively, in a test fixture; sequentially touching electrical contacts on the fixture, said contacts associated with each path in the cable; and providing a visual output that is a function of the continuity of each path in the cable.

2. The method of Claim 1 wherein said fixture includes a plurality of light emitting devices associated with each contact and wherein only one associated light emitting device will be lit if there is continuity for the path being checked.

3. The method of Claim 2 wherein said fixture includes an array of pins projecting from an upper surface of a housing, said pin array being located adjacent to an array of said light emitting devices and wherein said method includes the steps of: sequentially touching each pin in the array with a manually movable probe; and observing the number and location of light emitting devices that are energized.

4. A fixture for testing the continuity of a cable having wires running between terminals in connectors at opposite ends thereof, the cable being designed so that a single path is provided by each wire and its associated terminals in the connectors, said fixture comprising: a housing having a main surface; a first receptacle on the housing for receiving one of the connectors; a second receptacle on the housing for receiving the other connector; each receptacle having a plurality of electrical terminals therein which mate with corresponding terminals in the received connectors; and means carried by the housing for testing the continuity of each path in the cable, said means being electricaily coupled-to the receptacles and providing a visual output which is a function of the continuity of each path.

5. The fixture of Claim 4 wherein said means comprises circuit means coupled between the first and second receptacles, said circuit means including a plurality of light emitting devices, each device having one end coupled to one of the terminals in said first receptacle; said circuit means being adapted to energize only the light emitting device for the path being tested if there is continuity for the path being tested.

6. The fixture of Claim 5 which further includes a plurality of contact members on the housing, each contact member being connected to one, of the terminals in the second receptacle; and said fixture further including manually movable probe means having a stylus electrically connected at one end to a node common to the opposite ends of all of said light emitting devices; whereby the user can touch each contact member with the stylus and observe the light emitting devices, good continuity of each path being insured if only the associated light emitting device is energized when the probe stylus touches the associated contact member.

7. The fixture of Claim 6 wherein said light emitting devices and contact members are arranged in a geometrical pattern generally corresponding to the pattern of terminals in the connectors; and wherein the fixture further includeslindicia on the housing to provide visual correlation between the light emitting devices and contact members and their respective terminals to which they are associated whereby the user can determine the probable source of any lack of continuity when other than the one associated light emitting device is energized.

8. A fixture for testing the continuity of a cable having wires running between terminals in connectors at opposite ends thereof, the cable being designed so that a single path is provided by such wire and its associated terminals in the connectors, said fixture comprising: a box-like housing having an upper major surface; a first receptacle located on one side of the housing for receiving one of the cable connectors; a second receptacle located on an opposite side of the housing for receiving the other cable connector; each receptacle having a plurality of electrical terminals which mate with corresponding terminals in their respective connectors; an array of light emitting devices arranged or said major surface in a geometrical pattern of the terminals in one connector; indicia associated with each device to correlate each device with a given terminal in said one connector;

; an array of pins projecting from said major surface of the housing adjacent to said light emitting devices; a manually movable probe having a stylus adapted to permit a user to manually touch the stylus against each pin in the array; said light emitting devices each having one of. their ends each connected to one terminal in the first receptacle, the other ends of said light emitting dEvices all being coupled to a common node; said common node being electrically connected through a battery to the probe stylus; said pins each being coupled to a terminal in said second receptacle; and whereby continuity for each path in the cable can be:

checked by the user touching each pin in the array-, and observing light emitting devices which are energized, the energizing of the one associated light- emitting device signifying good continuity for the path being tested.

9. The fixture of Claim 8 wherein the light emitting devices comprise light emitting diodes.

10. The fixture of Claim 9 which further includes an audible alarm.

11. The fixture of Claims 6 and 8 wherein the light emitting devices are so arranged that during rapid testing with the stylus, a lack of continuity will blatantly appear.

12. The fixture of Claims 4 and 8 wherein said fixture is adapted for low power operation whereby the fixture may be hand-held and portable.