2.5V is coming out of the OPAMP that's being fed into the load cell, and it's being amplified to 2.5V (actual is about 2.49V) from the INA125 which then feeds the signal into the MSP430. I have set the ADC to REF2_5.
When I tried to apply a load (my own weight, 175lb) to the load cell, it would only go up marginally, maybe up to 32. When there's no load, it would normalize to 22. I'm expecting the value to be close to 170, but clearly it isn't. Why might this be happening?
I tested this set up by substituting the load cell with a potentiometer. I fed the 2.5V ref from the INA125 into the POT and then fed the signal into the ADC. I twisted it from left to right and it was giving me a lower bound of 0 and a upper bound of about 1010. This should mean that the setup is okay.
Advise on how to diagnose would be appreciated.
Note: if this matters, I am powering everything with a switching regulator (MAX756 set for 5V, boosted from 3V (actual is about 2.66V))
Edit: I thought about this a little more, I forgot to account for the accuracy of the measurement. With a zero balance accuracy of +/- 2%, the 22 value read seems to make sense. However with a +/- 0.5% accuracy, with 175lb, I should still be expecting about 170 steps.