> My statics and dynamics class was over 15 years ago, but if my memory
> serves, wouldn't you SUM the 4 load cells outputs to get the total weight?
> Each leg provides its own partial support, and doesn't "see" the total load,
> else 4 guys carrying the safe out of the bank, *just couldn't"

You are absolutely right, I slipped in the "average" in my first
posting before I actually thought about it real hard.  The 4 guys
would each carry 1 quarter of the weight of the safe and get 1
quarter of the loot each (less expenses, chiropracter fees, etc.)

But if you really think about it - in reality to sum OR average 4
analog values wouldn't your circuit use a 4 into 1 resistor network?!
(:-)

As a follow up to the helpful replies I got to my original question,
my need for the circuit as this time disappeared but no doubt I'll
need to do this sometime in the future.  I did however look inside a
commecial "4 load cells into one" box used for this very purpose,
and it used 8 or 12 precision resistors (100R?) and 4 x 10 turn
trimpots for balancing. (some thugs may have shorter legs?) Set up
on the four legs of the machine (not a safe), it gave impressive
repeatability from 0-300kg in 20kg steps on each end of the
machine.  I guess the trimpots might have to be set again if the
machine was moved to a significantly uneven part of the floor, but
probably their main function is matching the static resistances of
the load cells.

Brent Brown
Electronic Design Solutions
16 English Street
Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile: 025 334 069
eMail:  brent.brown@clear.net.nz