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

F

Francis

Jan 1, 1970
0
Dear all,

I would like to measure the rise and fall time of a short pulse over a
non-grounded capacitor. The pulse is 1kV amplitude and typical rise
and fall time are some ns. Pulse width is about 100ns.
I have in mind to use 2 Tektro P5100 probes connected on each side of
the capacitor and use A-B maths function of TDS5052B oscilloscope to
evaluate the signal performance. According to datasheet, P5100 is a
x100 probe with 250MHz BW (rise time 1.75ns) with loading of 10Meg and
2.75pF.
I was told that it would be better to use a differential probe P5205.
But this probe has 100MHz BW and loading of 4Meg / 7pF each side. I
have not such a probe today.
I would like to have a measurement error less than about 5ns.
I would appreciate your comment which method has the best accuracy or
any other proposal.
Best regards,

Francis
 
L

legg

Jan 1, 1970
0
Dear all,

I would like to measure the rise and fall time of a short pulse over a
non-grounded capacitor. The pulse is 1kV amplitude and typical rise
and fall time are some ns. Pulse width is about 100ns.
I have in mind to use 2 Tektro P5100 probes connected on each side of
the capacitor and use A-B maths function of TDS5052B oscilloscope to
evaluate the signal performance. According to datasheet, P5100 is a
x100 probe with 250MHz BW (rise time 1.75ns) with loading of 10Meg and
2.75pF.
I was told that it would be better to use a differential probe P5205.
But this probe has 100MHz BW and loading of 4Meg / 7pF each side. I
have not such a probe today.
I would like to have a measurement error less than about 5ns.
I would appreciate your comment which method has the best accuracy or
any other proposal.
Best regards,

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
 
Dear all,

I would like to measure the rise and fall time of a short pulse over a
non-grounded capacitor. The pulse is 1kV amplitude and typical rise
and fall time are some ns. Pulse width is about 100ns.
I have in mind to use 2 Tektro P5100 probes connected on each side of
the capacitor and use A-B maths function of TDS5052B oscilloscope to
evaluate the signal performance. According to datasheet, P5100 is a
x100 probe with 250MHz BW (rise time 1.75ns) with loading of 10Meg and
2.75pF.
I was told that it would be better to use a differential probe P5205.
But this probe has 100MHz BW and loading of 4Meg / 7pF each side. I
have not such a probe today.
I would like to have a measurement error less than about 5ns.
I would appreciate your comment which method has the best accuracy or
any other proposal.
Best regards,

Francis
 
Dear all,

I would like to measure the rise and fall time of a short pulse over a
non-grounded capacitor. The pulse is 1kV amplitude and typical rise
and fall time are some ns. Pulse width is about 100ns.
I have in mind to use 2 Tektro P5100 probes connected on each side of
the capacitor and use A-B maths function of TDS5052B oscilloscope to
evaluate the signal performance. According to datasheet, P5100 is a
x100 probe with 250MHz BW (rise time 1.75ns) with loading of 10Meg and
2.75pF.
I was told that it would be better to use a differential probe P5205.
But this probe has 100MHz BW and loading of 4Meg / 7pF each side. I
have not such a probe today.
I would like to have a measurement error less than about 5ns.
I would appreciate your comment which method has the best accuracy or
any other proposal.
Best regards,

Francis

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.
 
F

Francis

Jan 1, 1970
0
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
 
L

legg

Jan 1, 1970
0
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.

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
 
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