Re: differential probes

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

Original poster: "jimmy hynes by way of Terry Fritz <teslalist-at-qwest-dot-net>" <chunkyboy86-at-yahoo-dot-com>

Hey everyone,

I'll lay it all out tomorrow so you guys can check it.
With the surface mount chips, it is probably better to
skip the prototype and go straight to the PCB, agree?
The PCB has a two day turnaround, so I can probably
get them built by the end of the week. Who wants to
try one?


--- Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
 >
 > Hi Ken,
 >
 > At 09:53 PM 7/13/2003 -0500, you wrote:
 > >On Sun, 13 Jul 2003, Tesla list wrote:
 > >
 > > > Original poster: "Terry Fritz"
 > <teslalist-at-qwest-dot-net>
 > > >
 > > > Hi Jimmy, Finn, and All,
 > > >
 > > > This is the present schematic and parts list I
 > have in mind for the
 > > > differential probe.  I have NOT assembled or
 > tested it yet!
 > > >
 > > > http://hot-streamer-dot-com/temp/DiffProbe-5.gif
 > > >
 > > > http://hot-streamer-dot-com/temp/DiffProbe-5p.gif
 > > >
 > > > It is still just using the basic 150MHz TI
 > THS4151ID differential
 > > > amplifier IC and other straight forward parts.
 > > >
 > > > One thing I am "trying" to add is a front end
 > that can take a hard hit.  I
 > > > will have a system ground stud and MOVs at 1800
 > volts each.  These will be
 > > > fused with low current but high voltage fuses.
 > The idea is if you get a
 > > > say 20,000 volt cap on the input, the MOVs will
 > clamp it and the fuses will
 > >
 > >How about some neon lamps or one of those glass or
 > ceramic tubes the size
 > >of a pencil eraser with metal leads? Both should
 > have a low capacitance,
 > >and don't conduct until 70 volts or so for neon,
 > and several thousand for
 > >the larger ones. Maybe put them both in parallel.
 > You probably want the
 > >lowest possible impedance in a short mode,
 > otherwise the probe or what's
 > >left of it will dissipate lots of heat, which leads
 > to it blowing up or
 > >catching on fire. Large energy storage caps are
 > designed this way- to
 > >short out with the lowest impedance so their energy
 > is dissipated outside
 > >the cap tank in bussbar and fuses, not inside where
 > the tank will build up
 > >pressure and rupture. MOVs are basically
 > firestarting kits.
 > >
 > >KEN
 >
 >
 > I have a "bunch" of Victoreen SGCA-2500D spark gaps:
 >
 > http://hot-streamer-dot-com/temp/P7130038.jpg
 >
 > The 2500 volt firing voltage is sort of high.  But
 > not a big deal here if I
 > put them in parallel with the MOVs...  I am hoping
 > the "fuses" will break
 > the current before any fires start...
 >
 > Jim also mentions the Sidactors.  I think I remember
 > of few of them blowing
 > up in my face in the early 90'S :o))  But they are
 > also another great
 > possibility in this case!!
 >
 > Cheers,
 >
 >          Terry
 >
 >
 >


=====
Jimmy

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