0V in a schematic

Rich · 2009-02-08T12:30:47+00:00

I can see that when you see a voltage statement on a schematic, that is astatement of the voltage at that point with reference to some other point inthe schematic. It's not saying necessarily that the stated voltage is acrossthe component.Okay, is 0V on a schematic meant to be zero volts above ground potential, orcan it be any arbitary voltage above ground potential? Is it an absolutestatement that the point is at zero volts with reference to ground?

Feb 08, 2009 26 Replies

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Eeyore 17 years ago

Are you really sure you're cut out for electronics ?

Graham

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Eeyore 17 years ago

But it may not be so simple.

Graham

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ian field 17 years ago

A fun situation is the reference point of a mains powered SMPSU, usually being the negative end of the bridge rectifier - makes quite a loud "pop" if you accidentally ground it!

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John Fields 17 years ago

Fuck you, Graham. At least he\'s laying it all out so that we can see what he understands and where he\'s weak so that those of us who care can help him along on his way to enlightenment. And you? Instead of helping, you try to make him feel bad about himself by insulting him. Why would you do that? JF

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John Fields 17 years ago

So explain why not... JF

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Jamie 17 years ago

Because he's ignorant? Which comes in various colors btw. :)

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Jamie 17 years ago

0 volts found in a circuit normally indicates the circuit's common "COM" reference point to all other nodes of that circuit. It does not mean how ever, that it would be a common to a remote circuit. when I say remote, I refer to a device that allows external connection from some other devices.

Hence, the 0V ref is a point to where all other nodes in that circuit are in common with it.

Keep in mind that the "Common" supplied, for external/remote connection does not have to be this same 0V ref, It could be a virtual ground derived from this circuit or an isolated unit.

0V ref normally indicates a point of reference (com) for that circuit and does not necessarily mean it's the global common.

And to confuse things more, a Virtual ground could also be the 0V ref which would also be the common through out. This is normally found where only a single stand alone rail supply is available, for example, a battery or xformer with only 1 rail output. Both would offer isolation from ground conflicts when connecting to external "common" sources, but offer a way of creating a dual rail scenario to generate signals of +/- with respect to ground/common.

assuming the (+)&(-) is from a single battery or Single rail isolated supply.

(+)-------[1k]-------(V-Grnd/0V Ref)-------[1k]--------(-)

The above VG could be used as a common in an op-amp circuit while the (+) and (-) terminals of our isolated single rail supply creates the (+) and (-) rails with respect to the VG (virtual Ground) for the Op-amp's Vcc and Vee supply terminals.

The resulting output of the op-amp could generate a true +/- signal.

The only limitations of a VG, you need twice the voltage to obtain the dual rail voltages..

12 Battery would yield 6V +/- for example minus the losses from other things, we'll not get into.

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