Article 647 of the 2017 National Electrical Code (NEC) provides the requirements for “sensitive electronic equipment” but does not define the term. Nor is there a definition in Art. 100.
But isn’t all electronic equipment sensitive by its very nature? After all, there’s a reason we use static discharge protection when working on circuit boards but don’t use it when working on premises wiring circuits.
One way to solve this little mystery is to go through old editions of the NEC. A version of this material was originally included in an Article that provided the requirements for audio and video production equipment. Its focus was on reducing the electrical noise that can interfere with that equipment.
One of the unsafe practices aimed at reducing noise was to install a “separate” grounding system. Anyone examining the installation with an awareness of Kirchhoff’s Law of Parallel circuits would readily surmise that it created dangerous differences of potential. It was a cure worse than the disease. Article 647 addresses noise reduction practices, including tighter limits on voltage drop.