Feature: Avionics


DO-160 Section 2 -Definition of Terms -General RTCA DO-160 Section 2 requires the severity of limits, known as ‘categories’, to be decided. DO-160 lists categories for each test. Note that the category reference is not the same in all tests. Due to the large number of possible categories, they are not listed here but reference should be made to the DO-160 standard and the DO-357 User Guide. Te category information can be entered onto the Environmental Qualification Form in DO-160 Appendix A.


DO-160 Section 3 –Conditions of Tests RTCA DO-160 Section 3 provides the general test requirements: • Connection and orientation of equipment; • Order of tests, multiple test articles; • Combining tests; • Environmental conditions; • Test equipment; • Multiple unit equipment; • EUT configuration for susceptibility tests. Tis describes how to set up the


equipment, test facility and test equipment. Since these apply to all the environmental tests, some will not be applicable to EMC, e.g., combining test conditions.


DO-160 Tests Section 15 to 25 specify the EMC test requirements include: 15. Magnetic effect 16. Power input 17. Voltage spike 18. Audio frequency conducted susceptibility – power inputs 19. Induced signal susceptibility 20. RF susceptibility (radiated & conducted) 21. Emission of RF energy 22. Lightning induced transient susceptibility 23. Lightning direct effects 25. Electrostatic discharge (ESD) Some tests are subdivided into multiple


sub-tests, which correspond to separate tests in other standards. When writing test plans, it is easier to consider these sub-tests as tests in their own right, since they have their own test methods and limits. Section 19 is a good example, as it comprises five different tests.


EMC general test requirements A screened room must be used for both RF emission and susceptibility measurements, to provide a low level of ambient noise (emissions) and to prevent radiated interference infringing the Wireless Telegraphy Act (susceptibility). Some low frequency and conducted tests do not require a screened room. A basic screened room has the disadvantage


that it is a metal box and will resonate at certain frequencies, increasing the measurement uncertainty (40dB has been quoted). To improve the performance of the screened room, an RF absorber is attached to the walls to provide absorption of the RF energy, thus preventing reflections and resonances. Key issues in selecting a facility for test are: • Adequate size for EUT. Antenna to be 0.3m minimum from absorber;


• Door size for EUT access; • Semi anechoic lined (to meets Def Stan 59- 411 Part 3 requirements);


• Penetration panels for test antenna/sensor and drive equipment;


• Ambient levels 6dB below limit; • Power filtered (levels 6dB below limit); • Remote monitoring for susceptibility; • Cleared of all unnecessary items and personnel;


• Other services (exhaust extraction, compressed air, water, etc.). Te choice of test facility depends on a


range of factors, such as accreditation, price, capability, location and good reputation. Choosing an accredited facility is not usually mandatory but reduces the risk to the client who will otherwise have to satisfy itlsef that a non-accredited facility has performed the testing correctly. UKAS-accredited test facilities are given on the UKAS website: https://www.ukas.com/find-an-organisation/


Test plan contents A control plan or procedure may be produced at the start of a project and is normally used for large or complex systems. It demonstrates to a purchaser a defined EM strategy and contractual compliance. It provides EMC guidance throughout the project’s lifecycle. It also defines the EM management organisation, responsibilities, EMC requirements, design approach, test and


38 September 2024 www.electronicsworld.co.uk


qualification programme. Te test plan or procedure provides all the


information to enable a test facility to perform the tests. Generally, there is one test plan per equipment/system. Te test report is produced by the test facility as a record of the tests carried out. Tis demonstrates how the equipment complies with the test standard against the requirements of the control plan/test plan, and hence contractual requirements. Guidance on the content of these documents


is provided in DO-160, which requires the test categories and minimum performance standards (specification) to be documented on an Environmental Qualification Form, examples of which are given in DO-160 Annex A. Te cost of testing and timescales can become excessive unless good engineering judgment is applied in the form of a technical rationale for the selection of tests.


Test plan generic content • Description of equipment under test: Power supply, interfaces, cable lengths, size and weight;


• Modes of operation: Exercise all functions for emission and susceptibility;


• Test configuration and layout: Block diagram and layout on the bench/floor, grounding arrangement;


• Drive and support equipment; • Test requirements and rationale (any tailored requirements);


• Susceptibility performance criteria and method of monitoring: Parameters to be monitored, failure criteria


• Sweep speed, dwell time and susceptibility modulations;


• Test procedures and limits; • QA, documentation, safety and security. To achieve consistency throughout the


phases of EMC testing, it is essential to formalise the details of the test plan/procedure for the project. A test plan/procedure should therefore be developed and agreed with the client project manager prior to the commencement of EMC testing, and should be sufficiently detailed to enable any test to be repeated by another approved test house. Without a formalised test plan/procedure, the results of the EMC test may vary considerably due to possible variations in the test arrangement, thus obscuring the effects of any modifications during development of the equipment to the production stage.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54