Oh yeah, these things are like, mondo-cool. Generally, the logic pulser
and current tracer are used together. A common failure mode for TTL
and CMOS devices is you'll have a node in a circuit stuck low.
Okay, you have a source driving two or more inputs. Who's weighing
everything down? With the circuit in some steady state, start the pulser
pulsing, and apply it to the pin that's the source. Place the tip of
the
current tracer on the trace that the source is attached to, and adjust
the
sensitivity control until the indicator light has some intensity. I
think the
light will blink at some intensity when it's set right-- Anyway, run
the
probe tip along the trace. If the light goes out, or goes dim, you
passed
the branch to where you pulses are going.
You follow the pulses until you end up at the bad device and seriously
impress the hell out of anybody watching.
Why are these things so expensive?
The element at the tip is an *EXTREMELY* sensitive hall-effect device,
it's polarized (notice the little dot on the tip), and it's a seriously
intense
analog instrument in a teeny-weenie little package.
But probably mostly because some people will pay just about anything for
anything that's made by hp (nobody ever got fired for buying an HP
product over something else).
Anyway, so that's the low-down on current tracing (well, as good as I
can remember, anyway). For random-logic, you just cant beat it.
I think I still have an old applications bulletin around here
someplace. . . .
Jeff
On Fri, 09 Oct 1998 18:08:32 -0700 Bruce Lane <kyrrin_at_jps.net> writes:
>At 14:40 09-10-98 -0500, you wrote:
>
>>Holy smokes! You're right! They're not in the 1998 catalog, but I
>found
>>them in the 1996 catalog: HP-547A Current Tracer-- $975 !
>
> <eep!>
>
> My God... I just double-checked the model number on mine.
>
> Yep... 547A. Geez, and I though the Data I/O UniSite I got a
>few years ago
>was a coup!
>
> What makes the darn things so expensive? For that matter, what
>are some of
>the uses for it? I got it mainly as a curiousity, and as part of the
>purchase of my logic pulser, but if the thing is one of those Really
>Useful
>but Obscure tools, I'd like to know about it.
>
>
>-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>Bruce Lane, Owner and head honcho, Blue Feather Technologies
>(Hamateur: WD6EOS) (E-mail: kyrrin_at_jps.net) (Web:
>http://table.jps.net/~kyrrin)
>SysOp: The Dragon's Cave (Fido 1:343/272, 253-639-9905)
>"Our science can only describe an object, event, or living thing in
>our own
>human terms. It cannot, in any way, define any of them..."
>
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Received on Fri Oct 09 1998 - 22:34:17 BST