29 Nov
2009
29 Nov
'09
6:05 p.m.
On Nov 29, 2009, at 5:29 PM, dwight elvey wrote:
I have an HP non-contact current tracer, looks like a logic probe,
was supplied in a pouch with a logic probe and pulser. It is
wonderful...tremendously handy. Is that the device you're talking
about?
-Dave
--
Dave McGuire
Port Charlotte, FL
Wire-OR is
fine until you need to find out which signal is driving
the input low, or should I say to logic '1' (my machine uses -6.3v
= logic 1, 0v = logic 0). You need to isolate all the outputs to
check them, not TOO hard on a wire wrapped machine but must be a
swine if you've soldered everything together. Of course there
still the other problem, if you need two or more wire-ORs from the
same output, you need to buffer the outputs separately or generate
the signal two or more times.
HP had a clever probe that could actually measure the direction
of a few milliamperes on an IC lead. I use one of these
years ago while at Intel. I've not seen one since.
I suspect that it is because it still took an experienced
trouble shooter to actually use it effectively.
It didn't make a trouble shooter out of an idiot but
was a handy tool for a trouble shooter.
It did this by measuring the voltage drop but I suspect
that one could make a flux gate sensitive enough to detect
such a current.