Current Tracers

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(a)jps.net> writes: ___________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com or call Juno at (800) 654-JUNO [654-5866]