EMI/RFI
Electro-Magnetic and Radio-Frequency Interference (EMI / RFI) qualification testing is performed to ensure equipment can perform properly when subjected to radiated or conducted emissions from nearly equipment. We see the adverse effects of EMI / RFI in our daily lives, a common example being when we leave our cell phones close to computers or speakers.
While EMI / RFI has made for some entertaining movie plots, the adverse effects in real life can be quite serious, especially with newer equipment using smaller digital components. The inductive reactance from starting a nearby large motor may have had no effect on the original analog controller, but may cause a number of unwanted effects to a new digital controller. In fact, digital equipment almost never passes EMI / RFI testing without having to make some modification – typically shielding.