Tomi Engdahl’s ePanorama blog

Use right ground symbol in your electronics schematics and other drawings.

Earth-ground symbol represents a real connection to earth. That connection could be for example 10-foot-high copper-clad steel bar driven into the earth (at your premises or nearby provided by power company) or metal water lines. That earth ground is wired to the neutral of your house wiring at the breaker panel. You can reasonably use the earth-ground symbol for the ground pin on the electrical outlet. Your electronics equipment schematic should use the earth-ground symbol to indicate connection to the electrical outlet ground pin on equipment plugged to wall outlet.

It is bad practice to use earth-ground symbols for chassis common. You an use the chassis common wherever a power supply or circuit card connects to the chassis. In a circuit board schematic you can use chassis symbol when a standoff screws the PCB to the chassis.

Signal-ground symbols are most suitable for most circuitry on a PCB. A design can have several of these symbols, with notations to identify them.

Information source: EDN magazine article Draw the line: Isolation shields systems from shocking surprises

This entry was posted on Thursday, October 8th, 2009 at 11:10 and is filed under Electronics Design, Groundloop. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.