I have a pressure sensor, MPX2100 and I need to read its output with an Arduino. To do so I want to use a differential amplifier with a gain of 40 times (3k and 120k resistors). The impedance of the sensor's output is 3k. So is this input impedance too high that I will get non-linearities in the output?
The amp op that I am going to use is LM258.
Even though a In-amp is better I assembled the circuit above just to test my sensor while I wait my AD623 to arrive, however the gain is about 3 times! When my sensor's output is 50mV the output of the amplifier is about 170mV!
Another odd thing that is happening is that when I connect the sensor to the op-amp the voltage at the sensor's output changes to -4mV. I am not sure whether my sensor is not working properly or the amplifier circuit is messing everything up.