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  #1  
Old 05-04-2013, 02:21 PM
idleup idleup is offline
 
Join Date: Oct 2005
Location: San Antonio, TX
Posts: 281
Default Stupid Question...

Is -12v the same as ground? I am looking at my Gretz GA-1000 Heated Pitot wiring and it shows -12v and +12v...
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  #2  
Old 05-04-2013, 02:37 PM
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RV10inOz RV10inOz is offline
 
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Location: Brisbane Qld. Aust.
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Default

If you ask me it should be called ZERO VOLTS as the GND and 0v are tied together the potential between the airframe and the NEG/GND is supposed to be 0v.

Thus the airframe is GND and the battery -ve terminal is 0v and the other terminal is +12v or +24v in some systems.

you should not have -12v as the terms suggests that you could have a real -12v and that would mean 24v to the +12v.

Maybe I am wrong here.....but Ov and 12v or 0v/24VDC is what we use in the industrial world.
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  #3  
Old 05-04-2013, 02:46 PM
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Jeff A Jeff A is offline
 
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Location: Dallas, TX
Posts: 366
Default Yes

Not the best terminology, but in this case, yes -12v is the same as ground. Read the last line of page 1 and the first 2 lines of page 2. It clearly states -12v going to ground.

http://www.angusaviation.com/LinkCli...edownload=true
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  #4  
Old 05-04-2013, 03:53 PM
idleup idleup is offline
 
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Default

Thanks guys.
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  #5  
Old 05-05-2013, 11:44 AM
jim plaster jim plaster is offline
 
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  #6  
Old 05-05-2013, 11:55 AM
idleup idleup is offline
 
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Location: San Antonio, TX
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Default

Yea, what confused me is that I have always learned that negative voltage is very different than ground and ground should not be designated like that
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  #7  
Old 05-05-2013, 12:31 PM
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airguy airguy is offline
 
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Location: Garden City, Tx
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Default

And for those of us "old-school" guys that received physics/electrical education 25+ years ago, the whole idea of power flowing from positive to negative is just WRONG - it's the electrons flowing from negative to positive in the metal that does the current delivery, but most people have trouble wrapping their heads around that. Electrical convention is thus to show power as flowing from positive to negative when in reality the opposite is true.
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