Abstract:
A system is disclosed that can be inserted between cable runs of electrical equipment so as to provide access to signal/data lines associated with the electrical equipment. The system includes a microprocessor and a matrix switch and preferably display equipment and measurement instrumentation. The microprocessor controls the matrix switch so as to route signals to a high impedance probe array that then feeds data to measurement instrumentation. The system provides pattern analyzers, which are resident in the microprocessor routine software. The measurement instrument provides measurement quantities, timing, and patterns that may be compared to known good data to ascertain the state of the health of the electrical equipment. The system is also capable of blocking signal paths and providing known good signals to the associated electrical equipment. Test data is stored in memory for later retrieval and the display equipment provides a pass, fail or intermittent indication.

Description:
The invention described herein was made in the performance of official duties by employees of the Department of the Navy and may be manufactured, used, licensed by or for the Government for any governmental purpose without payment of any royalties thereon. 

   FIELD OF THE INVENTION 
   The invention described herein relates to a system for isolating faults between electrical equipment and is particularly suited for isolating intermittent faults. 
   BACKGROUND OF THE INVENTION 
   Electrical equipment aboard aircraft when subjected to harsh operational conditions frequently fail or break down. Such electrical equipment may have electronic equipment containing circuit cards and are commonly referred to as “weapon replaceable assemblies,” or WRAs. Typically, there are many WRAs within an aircraft and each is designed to be removed and replaced easily. However, narrowing a fault to a single WRA can be a time-consuming, labor-intensive, and often a very frustrating and costly process. 
   Frequently, in order to isolate a fault to a single WRA, a built-in-test (BIT) is performed which serves well its intended purpose. However, some aircraft have no BIT at all or even on aircraft with sophisticated BIT systems, locating the sources of intermittent faults (those faults not repeating regularly), as well as, false alarms can be a very difficult process. 
   The WRAs are connected by large bundles of wires, some bundles containing hundreds of wires. Currently, there is no known way to examine the electrical signals on these bundles while the WRAs are still in operation. It is desired to provide a system that allows for isolating faults between WRAs, while the WRAs are operational. Further, it is desired to provide a system that could be used to break diagnostic ambiguities between WRAs within an aircraft. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the present invention to provide a system that facilitates the isolation of faults between operational electrical equipment and is particularly suited to isolate intermittent faults. 
   It is a further object of the present invention to provide a system for extracting or injecting an electrical signal from or into one or more bundles of electrical wires interconnecting electrical equipment. 
   It is another object of the present invention to provide a system having an indication of the health of the electrical signal being monitored. 
   It is a further object of the present invention to provide a system that compares electrical signals extracted from the one or more bundles of electrical wires interconnecting the electrical equipment against known data to ascertain the health of the associated electrical equipment. 
   In one embodiment, the system is used for isolating faults associated with one or more electronic assemblies interconnected to each other by a bundle of separated electrical wires, wherein each of the separated wire is terminated in a pin of at least one connector. The system comprises; a) an adaptor having an acceptor or means for accepting each of the connectors. This means further comprising terminals that are connected to pins of the connectors. The system further comprises; b) a signal generator providing an output; and c) a selector having an output and an input connected to receive the output of the signal generator. The selector has electronic switching for selectively and separately connecting its output to the terminals of the means for accepting the at least one connector. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing objects and other advantages of the present invention will be more fully understood from the following detailed description in reference to the appended drawings wherein: 
       FIG. 1  is a block diagram of a system  10  of the present invention used for isolating faults between weapons replacement assemblies and which is particularly suited for isolating intermittent faults therebetween; 
       FIG. 2  illustrates further details of the adaptor  16  of  FIG. 1 ; and 
       FIG. 3  is a block diagram illustrating further details of the system  10  of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to the drawings,  FIG. 1  is a block diagram of a System  10  used for isolating faults associated with one or more electronic assemblies shown in  FIG. 1  as comprising Weapon Replaceable Assemblies  12  and  14  and is particularly suited for isolation intermittent faults thereof. The System  10  provides for fault isolation between Weapon Replaceable Assemblies  12  and  14 . 
   The System  10  comprises an Adaptor  16 , a Selector  18 , and a Signal Generator  20 . The Signal Generator  20  has an output that is routed to the Selector  18 , via signal path  22 . As will be further described, the Signal Generator  20  is programmed by a microprocessor to output signals for insertion into the Adaptor  16 . The System  10  preferably further comprises Measurement Instrumentation  24  and Display Equipment  26  respectively interconnected to the Selector  18  by signal paths  28  and  30 . 
   The Measurement Instrumentation  24  may be comprised of test equipment that may vary dependent upon different requirements. For example, the Measurement Instrumentation  24  may comprise an oscilloscope, a digital multimeter, a signal processor, as well as software defined for a measurement system for controlling the generation of virtual instrumentation. 
   The Display Equipment  26  may include indications of a status of the function being tested by System  10  and may be comprised of one or more light emitting diodes of different colors, so as to indicate the status of the result of the test being conducted by the System  10 . Similarly, the Display Equipment  26  may be comprised of a liquid crystal display. The System  10  may be further described with reference to  FIG. 2  illustrating further details of the Adaptor  16  having signal paths  32 ,  34 , and  36 . 
   The Adaptor  16  allows for hard wire connections of the Weapon Replaceable Assemblies  12  and  14  to be interfaced to the System  10 , more particularly, to the Selector  18  of the System  10  by way of signal path  32 . The Weapon Replaceable Assemblies  12  and  14  are interconnected to each other by a bundle of separated wires each of which is terminated in a pin or terminal of at least one connector. More particularly, as shown in  FIG. 2 , the Weapon Replaceable Assembly  12  is interconnected to the Adaptor  16 , by way of a cable  34  having pins or terminals  34   1 ,  34   2 , . . .  34   N−1  and  34   N . Similarly, the Weapon Replaceable Assembly  14  is interconnected to the Adaptor  16 , by a bundle of separated wires each of which is terminated in a pin or terminal of a connector  36  having pins  36   1 ,  36   2 , . . .  36   N−1  and  36   N . The Adaptor  16  is provided with a connector  32 , which respectively accepts each of the connectors  34  and  36  having pins  34   1 ,  34   2 , . . .  34   N−1  and  34   N  and  36   1 ,  36   2 , . . .  36   N−1  and  36   N , and which are respectively connected to pins or terminals  32   1 ,  32   2 , . . .  32   N−1  and  32   N . The System  10  may be further described with reference to  FIG. 3 . 
     FIG. 3  shows all of the elements of  FIG. 1 , but in addition thereto, shows that the Selector  18  is comprised of a 21:1 Probe Array  38 , a Matrix Switch  40 , a first Peripheral Interface Adaptor  42 , a Microprocessor  44 , a Read/Write (R/W) Memory  46 , a 1588 Tracking Clock  48 , and a second Peripheral Interface Adaptor  50 . 
   In general, the System  10  provides bidirectional multiplexer (data selector)/demultiplexer (data distributor) capability for handling both analog and digital data lines. As will be further discussed, the System  10  digitally controls which signal pathways of the Weapon Replaceable Assemblies  12  and  14  are open and which are closed to signal transmission. The System  10  is preferably provided to enable access to one or more data lines, to insert signals onto one or more data lines of the Weapon Replaceable Assemblies  12  and  14 , and to provide this data for comparison to known good data. Pattern recognition (e.g., signal rise/fall/dwell times, signal strength/values, signal timing, etc.) are performed by System  10  and comparisons are made with known good patterns. Pass/fail/intermittent status is displayed on the Display Equipment  26  as a result of continuous testing of the initiated test. The System  10  may be configured to be used with automatic test equipment (ATE) or may be packaged to be placed in situ. Power to energize the System  10  may be provided by an onboard battery or from the Weapon Replaceable Assembly  12  or  14  being tested. 
   The 21:1 Probe Array  38  of the Selector  18 , wherein the ratio 21:1 signifies that the signal is attenuated by a factor of 21, is known in the art and is commercially available. These 21:1 probes have minimal loading effects on the data lines of the Weapon Replaceable Assemblies  12  and  14  under test because of their low Q factor while still having a fast rise time. The 21:1 Probe Array  38  is primarily used to sample signal data. The 21:1 Probe Array  38  is selected to have a predetermined number of contacts (data lines) which are addressable (e.g. 64 data lines addressed by 64 separate probes) or a smaller number of array banks internally switched to address only the data lines of interest. 
   The 21:1 Probe Array  38  is bidirectional in operation, so as to accommodate both data sampling and data insertion. The bidirectional path of the 21:1 Probe Array  38  is shown in  FIG. 3  by the use of reference designation  32 A, which is operatively cooperative with and associated with transmission path  32 , transmission path  32 B between the Matrix Switch  40  and the Measurement Instrumentation  24 , transmission path  32 C between Matrix Switch  40  and the first Peripheral Interface Adaptor  42 , and transmission path  32 D between the Microprocessor  44  and the first Peripheral Interface Adaptor  42 . 
   The Matrix Switch  40  is known in the art and is commercially available. The number of contacts (data lines) of the 21:1 Probe Array  38  determines the matrix size of the Matrix Switch  40  (e.g. 64 contacts (data lines) requires and 8-by-8 matrix switch). The Matrix Switch  40  is controlled by the Microprocessor  44  by way of the first Peripheral Interface Adaptor  42 . Drivers (a pull-up resistor or a driver transistor) can be used to protect the Peripheral Interface Adaptor  42  output pins, shown by reference designator  32 C, from electrical transients, static electricity, or other damaging events. 
   The first Peripheral Interface Adaptor  42  is known in the art and is commercially available. The first Peripheral Interface Adaptor  42 , as well as the second Peripheral Interface Adaptor  50 , may be a MC6821 type or equivalent thereof. The first Peripheral Interface Adaptor  42  interfaces, via signal path  32 D, with the Microprocessor  44  (or Microcontroller) by way of an 8-bit bidirectional data bus, three chip select lines, two register select lines, two interrupt request lines, a read/write line, an enable line, and a reset line. The number of first Peripheral Interface Adaptors  42  used is determined by the number of contacts (data lines) associated with connector  32  (see  FIG. 2 ) required. The first Peripheral Interface Adaptor  42  also controls the Display Equipment  26 , via signal path  30 . 
   The Display Equipment  26  may be, as previously mentioned, comprised of light emitting diodes (LEDs) or a small liquid crystal display capable of displaying hexadecimal characters generated by the Microprocessor  44  and delivered to the Display Equipment  26 , by way of the first Peripheral Interface Adaptor  42  and signal path  30 . 
   The Microprocessor  44  is provided with Read/Write (R/W) Memory  46 . The Read/Write (R/W) Memory  46  stores data used by the Microprocessor  44 . Physically, the R/W Memory  46  may be either a Dynamic Random Access Memory (DRAM) or a non-volatile flash memory. Non-volatile memory or read only memory (ROM) may store known-good patterns used in pattern recognition processing for testing the Weapon Replaceable Assemblies  12  and  14  in a manner to be further described. 
   The Microprocessor  44  is also provided with a 1588 Tracking Clock  48 , which is a common system clock that feeds the Microprocessor  44 , via signal path  52 , the first Peripheral Interface Adaptor  42 , via signal path  54 , and any other components (not shown) that may require a clock signal to operate. The 1588 Tracking Clock  48  is known in the art and may also be used to synchronize the System  10  with any incoming clock signal associated with Weapon Replaceable Assemblies  12  and  14  by using an IEEE-1588 Clock Synchronization Protocol. 
   The Microprocessor  44  operates as the control processing unit of the System  10 . One embodiment of System  10  may be implemented by using a Motorola 68HC11 microprocessor or an equivalent microprocessor or microcontroller. The Microprocessor  44  communicates with the Signal Generator  20 , via the second Peripheral Interface Adaptor  50  and bidirectional signal paths  58  and  60 . Similarly, the Microprocessor  44  communicates with the Measurement Instrumentation  24 , via the second Peripheral Interface Adaptor  50  and bidirectional signal path  62 . The Microprocessor  44  communicates with the rest of the System  10  through the first Peripheral Interface Adaptor  42 , with the exception of the R/W Memory  46 . More particularly, the Microprocessor  44  communicates with the R/W Memory  46  directly, via signal path  56 . The Microprocessor  44  uses the 1588 Tracking Clock  46  as the system clock signal. The Microprocessor  44  does all data processing necessary in order to realize pattern recognition and to determine the status of the Weapons Replaceable Assembly  12  or  14  under test. In one embodiment, the Microprocessor  44  compares input from the first Peripheral Interface Adaptor  42  with known good patterns stored in the R/W Memory  46 . 
   In operation, and with reference to  FIG. 3 , the System  10 , more particularly the Microprocessor  44 , is programmed to operate in several modes, such as three. In the first mode, the System  10  is not electrically connected to the data lines under test, allowing normal operation of those data lines and, thus normal operation of the Weapon Replaceable Assemblies  12  and  14 . In the second mode, the System  10  is electrically connected to the data lines under test and measures and analyzes the signals passing along the data lines between the Weapon Replaceable Assemblies  12  and  14 . The status of the testing to which Weapon Replaceable Assembly  12  and/or  14  is subjected is outputted to the Display Equipment  26 , via the Microprocessor  44  (signal path  32 D), the first Peripheral Interface Adaptor  42  and signal path  30 . In the third mode, the System  10  is electrically connected to the data lines under test and isolates the incoming data lines to allow the System  10  to inject test signals on to the data lines between the Weapon Replaceable Assemblies  12  and  14 . 
   The Microprocessor  44 , in one embodiment, performs the complete series of operations, determined by resident routines, that controls all the three modes of operation of the System  10 . The Microprocessor  44 , in one embodiment, generates first, second, third and fourth control signals. The first control signal electronically connects the first Peripheral Interface Adaptor  42  to the Matrix Switch  40 , via signal paths  32 D and  32 C. The second control signal electronically connects the first Peripheral Interface Adaptor  42  to the Display Equipment  26 , via signal paths  32 D and  30 . The third control signal electronically connects the first Peripheral Interface Adaptor  42  to the Signal Generator  20 , via signal paths  32 D and  22  and also electronically connects the second Peripheral Interface Adaptor  50  to the Signal Generator  20 , via signal paths  58  and  60 . The fourth control signal electronically connects the first Peripheral Interface Adaptor  42  to the Measurement Instrumentation  24 , via signal paths  32 D and  28  and also connects the second Peripheral Interface Adaptor  52  to the Measurement Instrumentation  24 , via signal paths  58  and  62 . The Microprocessor  44  in the first mode of operation does not generate a first, second, third or fourth control signal, via signal path  32 D, thereby not activating the Peripheral Interface Adaptors  42  and  50  and the Matrix Switch  40 . 
   The Microprocessor  44 , in the second mode, generates the first, second and fourth control signals, thereby activating the Peripheral Interface Adaptors  42  and  50  and the Matrix Switch  40 . The Microprocessor  44  in response to its resident routines receives the signals passing between the Weapon Replaceable Assemblies  12  and  14 , and then measures or compares the received signal against known quantities, and analyzes these associated signals. The Microprocessor  44  analyzes the associated signals and the status of the results thereof is routed to the Display Equipment  26 . 
   The Microprocessor  44 , in the third mode, also generates the first, second and fourth control signals, via signal path  32 D, as in the second mode, but in addition thereto activates the Signal Generator  20 , via the third control signal which, in turn, generates signals, via signal path  22 , associated with the third mode that are interjected onto the data lines between the Weapon Replaceable Assemblies  12  and  14 . 
   The routines residing in the Microprocessor  44  for the second and third modes of operation are dependent upon the requirements of the signals exchanged between the Weapon Replaceable Assemblies  12  and  14  and are derived in a manner known in the art. 
   It should now be appreciated that the System  10 , when interposed between Weapon Replaceable Assemblies  12  and  14 , facilitates the isolation of faults and is particularly suited to isolate intermittent faults, because the signals associated with the Weapon Replaceable Assemblies  12  and  14  may be probed and tested, while the Weapon Replaceable Assemblies  12  and  14  are in their operational state generating active signals. 
   It should be further appreciated that the System  10  of the present invention provides for extracting or injecting electrical signals from or into one or more bundles of electrical wires interconnecting electrical equipment, such as the Weapon Replaceable Assemblies  12  and  14 . 
   It should still be further appreciated that the System  10  of the present invention displays the electrical signals being extracted or injected from or into the one or more bundles of electrical wires interconnecting the Weapon Replaceable Assemblies  12  and  14 . 
   Furthermore, it should be appreciated that the present invention provides for the ability to compare electrical signals extracted from the one or more bundles of electrical wires interconnecting the electrical equipment against known signals to ascertain the health of the associated equipment. 
   Although the invention has been described to specific embodiments thereof related to particular electrical equipment, there are more variations or modifications that will be readily apparent through those skilled in the art following the teaching given herein. It is therefore understood that, within the scope of independent claims attached hereto, the invention may be practiced other than as specifically described.