i have a AD8221 instrumentation amplifier with the following setup
+V is 3.3V
-V is -2V
Gain 100 ( 500 ohm resistor)
The circuit is a simple "3 resistor" voltage divider
Upper resistor - 10K resistor between 3.3V and +input
Lower resistor 10K between - input
Between the inputs there is a 12ohm resistor, forming a diferential voltage of about 1.97 mV.
I would expect to read about 197mV at the output, but instead i read 493mV between output and gnd.
If i replace the middle resistor with a 0 ohm resistor, i read 258mV.
Is this normal?
What i am doing wrong here?