Feature: T&M


immunity (infrequent events, such as electrostatic discharge due to someone touching the equipment). Criterion C allows temporary loss of function and applies to severe transient immunity that is very infrequent, such as a power surge or supply voltage interruption. Permanent loss of function will be a failure.


Doing more with less EMC standards have evolved to include broader frequency ranges and higher bandwidths, and the electromagnetic environment is becoming more congested with intentional and unintentional sources. This means the requirement to measure and control them needs to change, too. Test methods must therefore adapt to emulate the environment, and automation has increasingly become a need. Consequently, in EMC testing there is a shift from a manual to an automated approach. In many cases software helps a great deal to speed up pre-test verification, by using the same parameters each time the test is performed. If set up properly, the software will take that data and allow the user to observe performance trends that would take considerably more time if done manually. Testing resources are finite and, as the market evolves,


TUV SUD EMC chamber


there is growing demand for EMC test laboratories to do more with the same resources. Despite this complexity, EMC testing must remain accurate and consistent. To be more effective, EMC testing needs to evolve along the lines of Industry 4.0. For example, if you think of the test laboratory as a manufacturer that produces test reports, these must be as consistent as possible. One of the design principles of Industry 4.0 is


The standards set strict limits for emissions and immunity.


Emission limits control the amount of electrical interference a device produces that might interfere with radio and television reception, mobile phones, Bluetooth, Wi-Fi and a host of other wireless technologies we use today. Immunity limits require the product to operate in its


intended electromagnetic environment without disruption or degradation to its intended functions or that of others. Equipment must therefore be designed and manufactured with a reasonable level of immunity to electromagnetic disturbances, and so the electromagnetic disturbance it creates is not excessive. While a single item of equipment might meet these limits, there is no guarantee that overall emission levels will still be satisfactory if multiple items or additional components are combined. Therefore, the final integrated product must be assessed against EMC standards. For immunity testing there are three performance criteria – A, B and C – that are specified in the EMC standards, and each immunity test has one of them specified. Criterion A requires the product must continue to operate as normal at all times and applies to tests for continuous EMC phenomena (like immunity to adjacent mobile phones). Criterion B allows some degradation during the test and applies to tests for transient


information transparency and virtualisation. This is essentially the capability of information systems to simulate and create virtual copies of physical world elements. This is achieved through the creation of digital models that are fed by all the data received through sensors or instrumentation. For EMC testing, an automated software algorithm can


use modelled test data to verify what output should be expected from the system under test. A machine-learning tool can be trained on thousands of good and bad data sets, and can identify if the shape of a trace shown on a plot is correct. Machine learning eliminates the need for plots to be manually checked by engineers and supervisors to ensure measurements were accurate and that the equipment under test was set up correctly. While we want machine learning to take over some of the


workload, the reality is that not all decisions can be fully automated and human planning and interpretation are still key to successful EMC testing. In most cases there should be a mix of semi-autonomous capabilities in collaboration with people. It is still vital to recognise the need to sometimes have human engineering judgement applied against test results. The availability of real-time test data is also very important as it allows test engineers to make quick decisions and minimise a product’s time in the test laboratory.


www.electronicsworld.co.uk June 2023 29


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