DELTA Agenda 11 – DELTA’s reverberation chamber is electronics’ worst nightmare

ISTQB Foundation Level – Software testing

DELTA’s reverberation chamber is electronics’ worst nightmare

Traditional EMC chambers struggle to reach the very high field strengths that are required by EMC tests, which over time have become an integrated process in every electronic developer’s work. This is why at the end of 2012, DELTA opened a new reverberation chamber to accelerate EMC tests in the upper end of the scale, typically field strengths of over 100 V/m and potentially up to more than 500 V/m.

The reverberation chamber

In contrast to a traditional EMC test laboratory, a reverberation chamber is not covered with absorbers. Instead its ‘bare’ walls and ceiling are covered with metal plates that reflect the incoming radio waves back, again and again, exactly like a hall of mirrors and this means significantly higher field strengths can be achieved.

One of the end walls can be moved three metres forwards or backwards and it is equipped with a mechanism that can can push and turn the metal plates to that the waves can be further varied – and thus the desired field amplification and full frequency range is achieved.

Conditions as in extreme environments

However, one of the challenges is that the same field strength cannot be achieved in the entire chamber at the same time. DELTA can only guarantee that at some point during the test the item is exposed to a high field strength at each frequency.

The chamber is a niche test intended for clients who want certainty that their products actually function in the real world in extreme environments even while the products comply with industrial standards. For example, an insulin pump that lies next to a mobile phone in a chest pocket and which is thus exposed to a high level of electromagnetic noise.

“We wanted to be able to utilise the same range of test test techniques that the automotive, military and space industries utilise. We also work with thermal and mechanical stress parameters but in the EMC area, we were lacking in respect to extreme environments,” says DELTA Senior Technology Specialist Thåstrup Jensen.

Electric car batteries tested against noise from inverter

Lithium Balance is one of the chamber’s users and it supplies control electronics for the charging/discharging of large lithium ion battery packs that are used in electric cars, etc. The minimal EMC requirements in the automotive industry are the same as industry standards but the inverter for the AC voltage produces significant amounts of electromagnetic noise.

So Lithium Balance wanted to ensure that its latest generation of products could deal with very high field strengths.

“Our equipment had not previously been able to function at such high field strengths, so until the latest generation we were only able to settle with a traditional test chamber. But we went to Aarhus and luckily it was determined that we needed to use the high frequencies,” explains Lithium Balance Senior Development Engineer Erik Nielsen who also explains that the system first began to fail at field strengths above 200 V/m.

World-class Danish electronics

To support and strengthen the Danish electronics industry, in the period 2013–2015, DELTA is implementing a test contract with the Ministry of Science, Innovation and Higher Education – with the title ‘World-class electronic products, using reverberation technique.’ The aim of the contract is to help small and medium-sized companies to be innovative and to be at the leading edge with the design of robust electrical appliances.

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