I am trying to monitor pH from a low impedance sensor. The glass electrode is used as a reference.
The input referred noise of the amplifier needs to be low as well. AD8429 seems to be the lowest noise option. AD8421 is another option which I have not tried yet.
AD8429, dc-coupled at a gain of 5 was tested. However the sensor signal (between 0.1 -1 Hz) seems to be very low. The sensed signal (5 mV) is nearly a 100 times less than the expected signal ( 550 mV). Any reason why ?