problem
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3 analog inputs from 0 to 5 volts
1 output from 0 - 5 volts
3 inputs defined as i1,i2,i3
1 output defined as o1
if i1 =0 and i2 = 4 and i3 =0.1 then o1 = 1.1
if i1 =0 and i2 = 2 and i3 =0.1 then o1 = 1.2
if i1 =3 and i2 = 4 and i3 =0.2 then o1 = 3.1
if i1 =1 and i2 = 4 and i3 =0.3 then o1 = 2.1
many of these
contraint: no DAC or microprocessor. Obviously they want an OPA solution.
I expected to find a linear relationship which is damn easy with OPA-s:\nÿ1ÿ
The trick is to make an additive offset. Unfortunately to find this offset is non-trivial in matrix operations. You can experiment a little, and maybe there is a one-step octave solution as well, that just requires lower beer-level.