Re: [TCML] ocilloscope: Yep, I blew mine, too

[Davetracer@xxxxxxx]

Having blown an oscilloscope of mine looking at Tesla Coil waveforms, I  
(learned from sad experience) would agree with Ed here that caution is in  
order.
 
I felt that having my scope many feet away and using a small wire as  the 
pickup was "careful enough". And I was wrong.
 
You could perhaps limit the danger with an input resistor network, however, 
 you'd need resistors that will hold up under *extreme* voltages. (I have 
no idea  where you'd find them. Other people on this list do know, however.) 
 
Something like this:   (I am so bad at drawing little schematics  with 
ASCII art...) would help cut the input voltage by 10x. Changing R2 to 100K  
would cut it on the order of 100x.
 
Probe "hot"
<----+
       |
      /
      \   R1  -- 10 Megohm
      /
      \
      + ----------> Scope Probe "In"
       \
       /
       \  R2    -- 1  Megohm
       /
       \
     Probe Ground ----> Scope Probe Ground  "In"
 
 
You can also do a capacitor network with resistor bypasses, but the drawing 
 for that would look just awful.
 
Another thing you can do is connect a simple ol' NE-2 neon light between  
probe-hot and ground. If it goes on, there's more than ~~70 volts between hot 
 and ground, and that's really time to back off with the probe and triple 
check,  and be certain you know what you're doing.
 
Other coilers have related stories of blowing various systems in their  
houses (burglar alarms, garage door openers, and whatnot). 
 
 
Never a dull moment with Tesla Coils! Oh, well, that's part of the  fun.
 
Thanks,
 
Dave Small
 
 
 
In a message dated 10/31/2009 9:57:04 A.M. Mountain Daylight Time,  
evp@xxxxxxxxxxx writes:

G Hunter  wrote:

>What's a wenherst generator?  Are you referring to a  Wimshurst 
electrostatic machine?  Please explain what you are trying to  do.  I don't have 
enough information to understand your question, let  alone answer it.
>
>Cheers,
>
>Gregory R.  Hunter
>
If that's what you're talking about I wouldn't  get it anywhere near 
a scope- possibility of high voltage discharge and  blowing up the input 
to the  scope.

Ed



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