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A helpful reply from Prototyp_V1.0 and by now I would hope the thread would have given some idea of how to calculate things. Anyway...
As already said, the gain required is 12.5. So, a straightforward solution would be to use the differential amplifier approach with that gain:
Then you need to replace R6 with resistors to the power rails to give 10k parallel resistance but 3.3V on the connection to R1 by solving:
R3.R4/(R3+R4) = 10k and
R3/(R3+R4)5 = 3.3
So:
You could drop R2 but the calculation of the level shift becomes a little trickier.
Also, you need to be careful of offsets when choosing your opamp. You only have a 400mV input range so if you are after high accuracy even a 1mV offset will affect your results.
Keith.
As already said, the gain required is 12.5. So, a straightforward solution would be to use the differential amplifier approach with that gain:
Then you need to replace R6 with resistors to the power rails to give 10k parallel resistance but 3.3V on the connection to R1 by solving:
R3.R4/(R3+R4) = 10k and
R3/(R3+R4)5 = 3.3
So:
You could drop R2 but the calculation of the level shift becomes a little trickier.
Also, you need to be careful of offsets when choosing your opamp. You only have a 400mV input range so if you are after high accuracy even a 1mV offset will affect your results.
Keith.
