Passive Oscilloscope X100 Probe

[Peter Murray]

Hi All,

On my latest build the voltage is greater than my digital oscilloscope can measure on X10. Although it can measure 400V, by moving the zero line below the display 700V can be measured.
This was still to low, so I started looking at X100 probes. The oscilloscope has got x100 and X1000 settings but the manufacturer does not supply probes for these settings. (Chinese cheapie)
Most oscilloscopes have 1MOhm resistor built in with a 9MOhm resistor in the probe. This gives a X10 reading.
So I tried tried 100MOhm resistor (actually 10 x 10KOhm in series) I set the oscilloscope to X100 the probe to X1 and it works perfectly up to 4KV.

Regards
Peter

[Prinsloo]

Peter Murray

I think you are on the right track, it is the same principle applied by the guys playing with the big Tesla-Coils. Accuracy will depend on the tolerances of the 10 x 10k Ohm resistors you use but it will give you a ballpark figure.

Would you mind sharing the circuit you build in getting these high spike/voltages.

Thanks

Theunis

[Peter Murray]

Theunis,

you are right about the ball park figure, the resistors should be 99M Ohm but as you say it does depend on the tolerance of the resistors.
The energiser that I am using is in 'Bedini Monopole 1' thread 'Bedini Original Machine FEG 1984' . The information on the energiser is out of date as I have rebuilt it to incorporate the invaluable hints & tips from Faraday88.
I will be detailing my findings at the end of this month, just before I go on a 6 week holiday. I am using one coil at the moment while I fine tune the rotor and I am getting 1400V at 25mA. This will get better in the coming days.

Regards
Peter