Re: Differential voltage probes 3

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

Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi Paul,

I am thinking two grounds.  A scope/signal ground and a power, AC, HV 
ground...  I got the parts today but too busy yet to work on it.  Stay 
tuned....

Cheers,

         Terry


At 08:28 AM 7/3/2003 +0100, you wrote:
>Terry,
>
>Can you connect the differential output up to the scope input if the whole
>thing is floating?  This will reduce down the distortion products and noise
>from the IC that are coupled into the scope.  It seems that this would be
>better that use it with a single ended output.
>
>Cheers,
>
>Paul.
>
>----- Original Message -----
>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: <tesla-at-pupman-dot-com>
>Sent: Sunday, June 29, 2003 2:46 AM
>Subject: RE: Differential voltage probes 3
>
>
> > Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
> >
> > Hi,
> >
> > Ok, using bleeding edge, oh!, I mean leading edge parts...  I got it back
> > down to one IC.
> >
> > http://hot-streamer-dot-com/temp/DiffProbe21.gif
> >
> > The fabulous Ti THS4151ID apparently does all the power supply offsets and
> > CMRR fixing internally.  That chip is basically the whole enchaladia!   So
> > I just added Ohmite's little 5kV resistors, some 1% 1K resistors, some big
> > NPO caps and it's done.  It would almost fit on a quarter ;-)
> >
> > There are some relatively expensive parts now, but the total cost is not
> > that much.  The input resistors are $4 each, the IC is $9, the NPO caps
>are
> > $2...  But I think the total cost would be about $45.  Yes, it is all that
> > little surface mount stuff and you have to be careful since the high
> > voltage is very near.  Probably a good candidate for HV conformal
>coating...
> >
> > The input resistors are 5%, but hopefully they are somewhat matched as
>they
> > come off the reel.  The PCB around those resistors would have to be routed
> > out to insure voltage standoff.
> >
> > I have no idea what the frequency response would be, but it "should" be
> > pretty darn high!  The IC is 150MHz and I am feeding it just like it
> > wants.  With the input resistors being so small, a LOT of response
>problems
> > just vanish.  Caps across the 1k resistors could limit the frequency
> > response if needed.
> >
> > Unless someone has a better idea, I think I will give this one a try.
> >
> > Cheers,
> >
> > Terry
> >
> >
> >
> >
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> >