Re: Oscilloscope question

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

You ought to talk to Kevin Ottalini.. he has lots of experience with HV
inverters. I think he's on the list.

Most likely, when the caps in your CW stack discharge, you are getting a
big spike back into the inverter which triggers a self protection shutdown.
 You might be able to charge through some sort of RF choke.

Tesla list wrote:
> 
> Original poster: "Darin Willson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <darin.willson-at-voyager-dot-net>
> 
> I have a 3kv 40ma inverter for a neon sign licence
> plate. I would like to use it to make a VERY
> small coil. I need to find out the frequency
> of its output but dont have access to an
> oscilloscope. I've tried to make a Cockroft-Walton
> voltage multiplier to make a DC coil but it
> appears that this wont work. Every time I
> discharge the circuit it makes the inverter
> stop working and I have to disconnect the
> power and reconnect it. Any info as to why
> this happens would be great and I wont have
> to try to figure out what Im going to ask next.
> 
> I have found an oscilloscope program that uses
> a PC's sound card mic input for the signal input.
> Does anyone know how I could safely test
> the inverter using this? Im not to crazy about
> puting 3kv into my pc, but if there is some
> simple circuit I could put between the two
> to effectivly step down the output with out
> altering the signal that would be awsome.


Use a capacitive pickup.  Connect the mike input to a piece of wire that
serves as an antenna.
Connect the inverter to another piece of wire a foot or so away from the
first one.  Start digitizing... If you get nothing, slowly move the wires
closer (do NOT let them touch, or your PC WILL fry).  

A more sophisticated approach would be to rig up a capacitive voltage
divider. You probably want something like a 3kV:30 millivolt divider (i.e.
a 100,000:1)  The top of the divider is something like a 10 pF 10 kV cap
(or a series of 5 47pF 2kV units in series...).  The bottom of the divider
is a 1 uF cap.



> 
> Thanks,
> Darin