virtual Ground question

Hi,

Got a project that is a comm's sniffer / injector, project works fine however it needs two connections to work i.e. GND and test point as you would expect.

I had a thought and it's only a thought so no flames please, is it possible to only use one connection without having to find a common ground (by a wire that is) I saw mention of "virtual ground" not sure if this is what I'm talking about as it's all a bit heavy reading.

So question is, to pull a line high / low do I really need a wire connctingh to the GND on target?

Thanks

Steve

To inject an AC signal without accuracy it may work.
For DC, no.
For AC, you could use a capacitor from the ground lead to true ground to provide some isolation.

Scarr said:

I saw mention of "virtual ground" not sure if this is what I'm talking about as it's all a bit heavy reading.

Click to expand...

No, not really - "virtual ground" usually refers to generating a reference point between two supply lines (that is then used as the common or ground for a circuit). It is useful when trying to eliminate ground loops, or hum in AF circuits.

Scarr said:

So question is, to pull a line high / low do I really need a wire connctingh to the GND on target?

Click to expand...

As flat5 mentions, if the signal was AC or RF, you could use stray ground capacitance to provide a coupling in to the circuit under test (depending on circuit impedances) - but DC really does require something to reference it against.