PicoScope 7 Software
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How can the probe measure a signal without the ground?
How can the probe measure a signal without the ground?
In the image below I attached the signal generator output to a resistor. The output is a square wave.
When I attache the other probe to one side of the resistor, I see a square wave, however, because I did not attach the ground clip anywhere I am wondering how could the oscilloscope detect a signal? If I do the same with a multi meter and only use one probe of course I detect nothing. Then how could the oscilloscope detect the signal without having a closed loop/circuit? My other question is that with respect to what point the tip is showing the signal?
The image cannot be attached, so here is the link:
https://imgur.com/nx9VwX6
When I attache the other probe to one side of the resistor, I see a square wave, however, because I did not attach the ground clip anywhere I am wondering how could the oscilloscope detect a signal? If I do the same with a multi meter and only use one probe of course I detect nothing. Then how could the oscilloscope detect the signal without having a closed loop/circuit? My other question is that with respect to what point the tip is showing the signal?
The image cannot be attached, so here is the link:
https://imgur.com/nx9VwX6
Re: How can the probe measure a signal without the ground?
because all grounds of the scope are connected.
so the ground of the sig gen is connected to the ground of the scope.
The ground of the scope is also connected to the ground of your PC.
That is the reason you need to be cautious where you put the ground clip of the probe, it is not like a multimeter where the inputs are floating.
so the ground of the sig gen is connected to the ground of the scope.
The ground of the scope is also connected to the ground of your PC.
That is the reason you need to be cautious where you put the ground clip of the probe, it is not like a multimeter where the inputs are floating.
Re: How can the probe measure a signal without the ground?
Thank you for your reply.
So if I am going to use the function generator of the scope and probing using channel A, I do not need to use the ground probe of, for example, channel A. Right?
But if I need to know the potential difference across two points that neither of them are true ground of the circuit, what can I do? Should I use channel B and then subtract it from channel A? Is that why oscilloscopes always have at least two channels?!
So if I am going to use the function generator of the scope and probing using channel A, I do not need to use the ground probe of, for example, channel A. Right?
But if I need to know the potential difference across two points that neither of them are true ground of the circuit, what can I do? Should I use channel B and then subtract it from channel A? Is that why oscilloscopes always have at least two channels?!
Re: How can the probe measure a signal without the ground?
If it is low voltage < 20V that is the way to go.
You have some special scopes like the 4444 who have floating inputs but also only to 20V.
If the voltage is above 20V than you need to use differential-probe
Benno
You have some special scopes like the 4444 who have floating inputs but also only to 20V.
If the voltage is above 20V than you need to use differential-probe
Benno