Power ground

[Clarence L.Snyder]

Geoff Richards wrote:
> 
> Anyone have time to explain the difference between 'ground' and
> 'powerground'?
> TIA
> Geoff
I'll give it a crack.
In a DC power system on a car, the negative(usually) terminal uses a
"chassis ground" for power "return".This is your "power ground". It can
have a voltage drop of up to .1 volt across it for accessory and
charging loads, and up to one volt for starter loads.
For signal circuits, such as sensors, sometimes the .1 volt drop across
the frame ground could cause calibration errors, so a "signal ground" is
provided. Sometimes the signal can even "float" above chassis ground, as
through a protection diode with a, say, .6 volt forward voltage drop.
Can't use chassis ground return for such a signal.
Hope this helps understand it.