I am using two AD8429 to sense the voltage on a same shunt resistor. The problem I have is the output reading of one of the AD8429 is changing when I disconnect the other one inputs. The shunt is in range of less than one ohm and the AD8429 input impedance is about 1.5GΩ. The change is significant, if the input voltage is 0V the change is about 60mV output for gain of 4, when I disconnect the other AD inputs. And about 1mV change when the voltage between the shunt terminals is about 0.25V, gain of 4. The picture attached will show the circuit example. This problem is confirmed on by other people, they made the same circuit and got the same problem, so no way I made a mistake in building the circuit.
Any idea why?