WHAT IS GROUND, ANYWAY?

摘要

In the 1980s, James McLaughlin was an electronics professor at GMI (General Motors Institute)-now Kettering University. Many of the practical circuit examples he used were for automobiles. He was brutally strict in one area: the definition of "ground." "If you draw a schematic for a piece of electronics in a car and use the earth-ground symbol, I will fail you for the entire semester," he said. He explained that the earth-ground symbol (Figure A) represents a 10-foot-high copper-clad steel bar driven into the earth. Water lines or metal gas pipes also constitute earth grounds.