On Sat, 17 Jan 2004 16:28:01 +0800 budgie wrote:

On Fri, 16 Jan 2004 19:08:09 -0600, Jim Adney wrote:

On Fri, 16 Jan 2004 08:53:49 +0800 budgie wrote:

On Thu, 15 Jan 2004 16:44:35 -0600, "Steve Nosko"
wrote:

Seems to me there's a way to use a moderate current and sense the
_magnetic_ field. Follow the field around the board along the runners.
However, I don't remember what was used to sense the field.

HP used to make a hall effect (IIRC) probe for current tracing. One of their
Bench Briefs technotes described the probe and the process.

It was the HP 547A Logic Current Tracer combined with the HP 546A
Logic Pulser. These worked only with TTL or CMOS circuits. The pulser
would drive current into any point you wanted and the tracer could be
used to follow the current path.

That may have been the sensor, but the article I saw related to tracing shorts.
To that extent, it was environment-independent.

I'm sure you're right that it would work anywhere that you could use a
+5 to +15V pulse.

They work well, but the current tracers are rather hard to come by now
and they are rather expensive when you find them.

Most HP stuff I've seen works well. Being HP, I'm sure they were expensive way
back then.

The Logic probes and pulsers in this series are fairly easy to find
today, but I had to look a long time before I found one of the tracers
at a reasonable price. Yes, they cost more when they were new, but the
tracers were only about 25% more than the probes. Used, they usually
cost at least twice as much as a probe.

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Jim Adney
Madison, WI 53711 USA
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