Re: Differential voltage probes 1

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Crow Leader by way of Terry Fritz <teslalist-at-qwest-dot-net>" <tesla-at-lists.symmetric-dot-net>

Tesla list writes:
>Original poster: "Stephen Conner by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>
>At 16:35 28/06/03 -0600, you wrote:
>>Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
>>So I am wondering what a good max voltage number and top frequency should 
>>be?  We could push the voltage up higher I think, but the frequency will 
>>probably just turn out at around 5 to 10MHz.  The high resistance 
>>dividers are the problem.  I note Tek drops Z wildly at high frequencies 
>>to get higher frequency response...  Note sure that is a great idea...
>>This type of probe would drop CMRR and all that to "don't care"...
>You own a Tek P6015 probe, so you know the lengths that need to be gone to 
>if you want to keep a HV divider network flat to within a measly 2%. In 
>this application you're trying to do the same, and worse still, to match 
>two networks to each other. Using physically small resistors will help you 
>by reducing parasitic capacitance and antenna pickup effects, but this 
>will also reduce the voltage safety margin.
>I think the tradeoffs involved mean that jobs like this would be better 
>done by two probes. Probe 1 would be a reasonably fast 10x active 
>differential probe, with maybe 500V common-mode capability and at least 
>20MHz bandwidth, for looking at microcontrollers, gate voltages, etc, in

What sort of microcontroller needs a 500 volt differential probe?
KEN
a
>SSTC.
>Probe 2 would be a 1000x passive single-ended HV probe (a cheap clone 
>built along P6015 lines and filled with mineral oil) or a 1000x active 
>diferential probe, good for 20kV (like the circuit you posted) for playing 
>around your conventional coils. The bandwidth of this one only needs to be 
>about 1MHz, indeed a low bandwidth might help by getting rid of spark gap 
>rubbish.
>Steve C.
>