--- Good luck with that.
Here's what the OP's got:
Vs>----------+-------+ | | [R1] [R3] | | | +-----E1 | | +-------|-----E2 | | [R2} [R4] | | GND>---------+-------+
Where the resistors are the legs of a Wheatstone bridge and E1 and E2 are the outputs from the dividers.
In one case he has a strain gage where E1-E2 = 0.01V full scale, and in another, with the same Vs, he has a strain gage where E1-E2 =
0.02V full scale, and what he wants is this: (view in Courier)Vs>----------+-------+--------------+ | | | [R1] [R3] | | | +---+---+ | +-----E1---| +|--->+5V | | | | +-------|-----E2---| -|--->0V | | +---+---+ [R2} [R4] |MAGIC | | |BOX GND>---------+-------+--------------+
Where, in the first case the magic box has a gain of:
Eout 5V Av = ------ = ------- = 500 Ein 0.01V
and in the second case, a gain of:
Eout 5V Av = ------ = ------- = 250 Ein 0.02V
Now, with only E1 and E2 available as inputs to the magic box, how's the box going to be able to tell the difference between the full-scale output of the first strain gage and the half-scale output of the second one?
That is, how is this "feedback signal" you allude to being generated, and where's it coming from?
-- John Fields Professional Circuit Designer