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>

Hi Terry,

I sent the boards to you yesterday, but I forgot to send you the fuses. Do 
you have any, or do you want me to send them to you. The banana jacks I got 
were "little", I didn't know there is more than one size. I don't think 
that's the kind you wanted, but I threw them on one of the boards anyway, 
because they're so easy to take off.

Here are some pictures of my board 
<http://www.hot-streamer-dot-com/chunkyboy86/diffprobe.jpg>www.hot-streamer-dot-com/chunkyboy86/diffprobe.jpg 
www.hot-streamer-dot-com/chunkyboy86/diffprobe2.jpg

If the voltage of the batteries powering it aren't equal, there is a DC 
bias, which makes it tough to read small voltages on my old scope. Why 
wasn't the VOCM pin grounded? Don't say cost ;-))

When I hooked it up to my function generator, there were some spikes at the 
leading edge of the square wave (200khz). The spike doesn't appear with my 
other probes, so I think that it is fake.

Tesla list <tesla-at-pupman-dot-com> wrote:
Original poster: "jimmy hynes by way of Terry Fritz "

Hello,

I got the boards put together today, and it seems to work. I forgot to
order the BNC connectors and the banana jacks, so I ordered them today. I
should have everything ready tomorrow.

Tesla list wrote:
Original poster: "jimmy hynes by way of Terry Fritz "

Hi Terrry,

--- Tesla list wrote:
 > Original poster: "Terry Fritz"
 >
 > Hi Jimmy,
 >
 > Cool!
 >
 > R13 to R11 and R14 to R12 seems too "thin".
 >
 > R12 to the MOV seems to have a small place where the
 > traces are thin too.

I started out making everything thin, and just widened
them later. looks like i missed a few
 >
 > The ground pad of TVS11 does not seem to have a via
 > to th! e ground plane.
 >
 > The traces for LED31 and R31 seem thin.

I didn't think it would matter for that one. The whole
wide trace thing is for low inductance, not low
resistance right? I'll fix it, but I don't see why
fatter is better there.

 >
 > I don't think the ground for the MOV on R22 is
 > right.
 >
 > We may be able to just put the fuses between the PC
 > board and the actual
 > banana jack connectors on the plastic case.

OK. That makes the insulation alot easier. The fuses
took up so much room i had to get rid of my happy face
:-(.
 >
 > I am thinking about using F211-ND fuses from
 > digi-key. They are non-stock
 > but they have 480 of them. Pigtail fuses would
 > eliminate fuse holders but
 > the fuses could also go in insulated in-line fuse
 > holders too. So
 > basically, I don't think we should worry with
 > putting the fuses on the
 > board. Th! ey are probably better off somewhere
 > between the board and the jacks.
 >
 > Thanks a bunch for doing all this!!! It should be
 > really cool!!

Thanks for designing it, and helping me with the
layout. I agree, it shoul! d be really cool!

 > Cheers,
 >
 > Terry
 >


=====
Jimmy