Identification of the problem
The capabilities of the IFD™ TE are so extensive that they can be applied successfully to a huge variety of testing scenarios. These include:
Ø No Fault Found Troubleshooting – by detecting intermittent faults on Line Replaceable Unit (LRU) backplanes and chassis, on circuit boards and in wiring looms.
Ø Rapid checking for the correct installation of modifications.
Ø Product assurance testing to confirm the integrity of the design and assembly process for new design and development components and wiring.
Ø Integrity testing of Electrical Wiring and Interconnection Systems.
Therefore, to obtain the maximum possible benefit from the huge capabilities of the IFD™ TE, it is vital that the problem and/or the testing objective are considered. The key is to methodically and systematic carry out testing using the information available in order to gather test data to provide a decision ready outcome ie not assumption based.
In fault-finding and troubleshooting scenarios the first step is to review the available design and maintenance data. If there has been diagnostic activity and repair activity undertaken already, then the maintenance activity should be reviewed to see if component replacement has been an influence in the recorded symptom. If the symptom has been unaffected by component replacements, and repeat replacement, then a change of approach is required. This scenario is commonplace in transport maintenance (aerospace particularly) and analysis of the symptom and maintenance data is vital to establish whether the symptom remains with the platform (ie the aircraft, car etc) when a component is replaced or moves with the component (ie the WRA or LRU). If this is the case, then an intermittent fault diagnosis should be carried out to establish the most likely source of the fault. In doing so, it must be remembered that intermittency occurs most commonly in interconnections, such as wiring and connectors; see
Basic Concept of Intermittent Fault Detection. This must be borne in mind when conducting an intermittent fault diagnosis. Overall, analysis of the data in this way will reveal whether the fault can be attributed to a removed component or whether it is attributable to the platform’s wiring.
Having narrowed the likely source of the fault to the platform or to the component, the initial problem can then be investigated and defined as far as possible using basic testing or fault finding procedures. The results of these initial findings can then be used to define the nature of the problem in the context of the reported symptom, as well as narrowing down the possible area, component or sub-assembly that might be responsible for the fault. Reducing the size or complexity of the possible areas of fault to an absolute minimum is vitally important to making the design of the interface adapter and selection of tests easier for the User. The results of this in-depth analysis and exploratory testing should then be used to inform the determination of which IFD™ test mode(s) to use to achieve the quickest possible successful test result.
Prior to carrying out IFD™ testing on the chosen Unit Under Test (UUT), the User is advised to consider the following points. These should be reviewed and addressed in order to refine the test approach used and thus maximise the chance of a rapid and successful testing result:
Ø Is a simple fault expected? Therefore, only a single test may be required to find the intermittent fault.
Ø Is the fault more complex? Therefore, a series of tests may need to be planned to provide a larger dataset about what is happening at specific times to the UUT.
Ø How much of the UUT do I need to test? Initial analysis of the fault history and of the system design may help to narrow the likely fault source to a single connector, board or module.
Ø Am I looking for a single fault? Initial analysis of the fault history and of the system design should consider the possibility that there may be more than one intermittent fault contributing to the symptom reported originally.
Ø Will the testing actions I have decided upon guarantee isolation of the fault? The test actions decided upon may only lead to an approximate fault location. This will enable the User to conduct subsequent, deeper fault analysis and investigation, which can then lead to a refined testing solution being applied to a specific element of the UUT. The refined testing solution may require a specific interface adapter, or incur the need for more representative environmental stimulation, or may require the need for applying other types of test equipment, eg LogScope™, SSTDR and/or Tracker.
