Re: Curve tracers

On Wed, 28 Jun 2006 11:58:17 +0200, Gerhard Hoffmann <spamtrap@xxxxxxxx>
wrote:

4) A customer of mine used a curve tracer to check the connectivity
of signal lines to BGAs. Not for mass production, but for lab prototypes.
You can clearly see the protection diodes to vcc and gnd.
Removed a lot of doubt if sth. did not work as expected.


In the 70s - 80s I worked for a large mainframe computer company. The
models were based on ECL technology. Someone figured that a curve tracer
was great for telling if a net had its source, load, and resistive
termination. Any part of the characteristic curve missing indicated a
bad connection.

The big Tek curve tracers were spendy for this and 99% of the
functionality was not needed. One of the engineers whipped togeter a
little box with an AC transformer, a pot and a resistor or two.
Connected to the X-Y inputs of a scope you had all you needed. The I
input on the Y axis of the scope was backwards with the simple
configuration, but who cares. Good enough for our needs and cheap.

I made one and use it from time to time for looking at what is connected
to a net. Many technologies don't have opposite polarity diode
signatures on the source and load like the ECL did, but it can still be
helpful, as Gerhard mentions.

.