The Most Common EMI Problems (a work in progress!)
This paper is based on over 30 years experience in the lab,
not sitting behind a desk!

1.   Power Supplies

Noisy Power Supplies are one of the most common problems we see in systems. It all starts with good clean power. Before you choose to buy thousands of a particular power supply ask the manufacturer of the supply for the Declaration of Conformity (DoC) and their CE Test Report. If they can’t provide at least a DoC – Run don’t walk to another vendor! Over the years we’ve seen tons of “Fake CE Marks”. 

Some of our customers will actually test several samples for Conducted and Radiated emissions before committing to buy several thousand of a particular Power Supply. We can do this testing within our two hour minimum for $700.

DC-DC converters are also a big noise source. Make sure to follow any guidelines for schematic and board layout that the manufacturer provides for you in the User Guide with respect to noise reduction and EMI.