EMI and EMC
also: electromagnetic interference · electromagnetic compatibility · emissions · immunity
EMC means a device neither emits too much electromagnetic noise (EMI) nor malfunctions when exposed to it; most markets require testing to show both.
Every electronic product leaks some electromagnetic energy, from switching power supplies, clocks, motors and digital buses, through its cables and enclosure. Emissions limits protect radio services and other equipment from interference. Immunity tests check that the product keeps working when exposed to radio fields, electrostatic discharge, surges and fast transients on its cables. Rules such as FCC Part 15 in the US and the EU EMC Directive set the requirements, generally through IEC and CISPR standards.
EMC is one of the most common reasons hardware schedules slip. Failures are usually fixable (layout changes, filtering, shielding, cable ferrites, grounding), but a fix discovered at the final certification lab can mean a board respin.
The cheapest fixes are designed in: solid ground planes, short current loops, filtered I/O, controlled switching edges, and pre-compliance scans on early prototypes.
Founder takeaway
Design for EMC from the first layout and run pre-compliance scans on early prototypes instead of discovering problems at the certification lab.
engineer review pending