Probe for rise/fall time measurement of 1kV floating signal

Although the nodes are ungrounded, what is the impedance and noise flora situation between the nodes and ground?

This will affect the way you might tackle the problem.

RL

You need to determine the common mode voltage in comparison to the pulse amplitude. As your pulse is large then your first choice would work. If you were trying to measure a small pulse on a large common voltage then you would need a differential probe.

| | coax +---------c---r----r----==========-50r scope ch 1 | | | your cap | | coax +---------c---r----r----==========-50r scope ch 2 | | | |

Do this if you can stand a 2K or so AC load. Use the scope in channel subtract mode.

The R's can be, say 1K 1206's or carbon comp/film parts; all are fine at this speed. Match as needed for cmrr. Ground the coaxes at both ends. Add attenuators at the scope inputs if the signals are still too big.

Or you could do a balun sort of thing, depending on your exact situation.

John

Thanks for all the infos.

The potential difference across the capacitor is zero except during the pulse of 1kV which has a duty cycle of about 1%. The impedance around the capacitor is very low during the pulse.

RL, I am sorry but I don't understand what you mean by noise flora. Could you explain? John, thanks for your solution. I will experiment. Thanks again and best regards.

Francis

Where is the system ground, with respect to the capacitor nodes? What is their capacitance/resistance to ground.

You say the nodes are floating, but you also say the impedance is low during the pulse. If this is the case, connecting coax center conductors to your scope input could be damaging, in the event of 1KV differential signals.

RL