Pressure transducer / sensor (0.5 - 4.5V) innacurate analog pin readings
I tried same setup with arduino uno and the problem is gone. It also works on micro as long as gnd and 5v pin is connected to uno. Uno measured voltage is 4.88V and micro 4.60V could a voltage difference this small cause this? What else could this be?


Reinstatement of incorrect edits by Annonomus Person
(AP: Please do not edit answers in such a way that you entirely change their meaning. In the current discussion "the board" is meaningless. We are trying to distinguish between symptoms seen in two different 'boards', an Arduino Uno, and an Arduino Micro.)

Looks to me like the problem is with the Arduino Micro's 5V supply then. 

If you are powering the Micro from an external supply (not USB), then 4.6V on the Micro's "5V" output would indicate that the 5V regulator is not operating within its expected range. 

If you are powering from USB, then the regulator is not in play. The 4.6V would indicate a problem with the USB's 5V supply.

Likely possibilities:, either the upstream supply is inadequate, or the micros and whatever is attached to it is drawing too much current.

I suspect that the transducer output is fluctuating in a way that's too rapid to be seen by your meter, but which is sampled by the Arduino Micro, giving your varying result numbers.

Either the "4.6V" is inadequate to run the transducer, causing erratic transducer output, or the 4.6V itself is fluctuating, with similar results at the trans output.

And you might also check the ground between micro and transducer -- are you sure that's wired correctly?