-the op amp output is connected to an analog pin on the arduino: so normally i should have no problem as far as load goes right?
IIRC the input resistance of the ATmega is a few 100K. Most op-amp specs are
with a load of 1K - 10K so you are at least an order of magnitude below the
I will indeed need the full range of the ADC in the end, having a range of about 0-500 (had to use the 3v pin as the 5v is already being used) is not sufficient for my needs:
-the useful range of data i had, before using the op amp was between 200 and 250 (as in , just 50 units of useful data out of 1023 to work with!!)
-i will have to adjust resistor values to get a lower amplification as well (went with a 10k and 1k res, so a gain of 11 which saturates darn fast when you don't have the full ADC range to work with)
-if i am not able to get sufficient precision i also though about adding a high pass filter of sorts as well, to eliminate the useless lower values too
Your problem is not with gain but with offset. You actually need a higher gain.
If your data range is 50 (250-200) you want a gain of 20. This will let you use the
full range of the ADC (1000 = 50*20). You need to subtact 200 prior to
multiplication. If you subtract 200 your signal goes from 0 to 50 (0 to 1000 with
a gain of 20).
You can configure the op-amp to subtract as well as amplify.
(* jcl *)