[sdiy] A little OT, Begging a hand

[Tim Stinchcombe]

> one equation is missing (as has been pointed out already while I was 
> doodling away)... unless you know something else, e.g. about 
> the relation 
> between R4 and R5 that would allow to formulate this as 
> either a fully 
> determined linear system or at least an optimization problem.

OK, it's been 20+ years since I dealt with anything like this, but I'll
throw this out there: since we have 5 unknowns, but can easily set 3
variables, V1, V2 & V3, to each of at least 2 values (+ve, gnd and perhaps
o/c) and then measure Vout, can't we turn it into an *over*determined
system, and get say 8 equations (=2^3), and then seek some sort of 'least
squares' fit solution?? (I have all sorts of (m x n) x (m x n)^T matrix
images in my mind, but I don't know that I ever fully understood it back
then anyway...)

Tim
__________________________________________________________
Tim Stinchcombe 

Cheltenham, Glos, UK
email: tim102 at tstinchcombe.freeserve.co.uk
www.timstinchcombe.co.uk