Here they define being floating as:
They mention Ungrounded = Floating.
But in another forum someone wrote:
The signal is consider floating when it does not have the same ground with your device. Earth has nothing to do with it. Earth is just another ground.
I'm a bit confused with the meaning of floating. Is the source floating in the below system?:
If it is not floating can you give an example of a system where the source ground is floating?
A floating source is connected to a differential amplifier. If I add a ground where the red arrow points the simulation circuit amplifies this signal very well. But if I don't use a ground the simulation corrupts.
In real do we really need a ground at that point or is this only needed in SPICE simulation? Because if I add a ground it is not floating anymore in the diagram. This is really confusing.
Even more confusion.
I always encounter such circuit topology for differential amplifiers:
Please notice that, above the input diff signals i.e the source and the diff. amplifier again share the same ground.
But when I look at the input terminals for a voltmeter or a diff. ended data acquisition board, there is no extra ground. There are inputs for -Vin and +Vin, but not GND.
Imagine now that I have a device which has an analog ground called AGND1 and this device has two differential outputs say 2V and -2V relative to its own AGND1. Now if I hook up its differential outputs to the voltmeter or a diff. ended DAQ board which has its own ground call it AGND2, we are facing a situation where AGND1 and AGND2 are not connected. But still these systems work as below:
As you see in a typical voltmeter or diff ended. DAQ board connection we don't connect two sytems grounds AGND1 and AGND2.
So the diff. amplifier topology I encounter uses grounds common but in real the grounds are not connected.
This is also very confusing since I dont know where my lack of knowledge comes from.