RE: Primary Scoping

>I have thought about using a 1000:1 divider ratio using 4 of the dale
>100Megohm resistors in series to a  5 parallel combination of 2megohm 
>comp resistors. I'll then put some transorbs to ground before the scope
>connection. All components will be physically well mounted to prevent
>circuit disconnection.
>BTW, transorbs can be thought of as a 5ps.(thats not a typo: 5*10^-12
>second) zener with a many thousand Amp ratting. By using 2 of the
>unidirectional devices in antiparallel I can get any clamp voltage between 
>and 500 volts with only a 200pF capacitance penality.

You've just built a lowpass filter with a cutoff frequency of 2 Hz!  So you 
won't see too much of the signal you are trying to measure (100's KHz).

Fc = 1/(2*pi*R*C) = 1/(2*3.14*400e6*200e-12) = 2 Hz.

With such large resistors, any capacitance is going to severely reduce the 
frequency response.  This includes the cables and scope input capacitance.

Bryan Zublin