INA116 instrumentation amplifier shows unexpectedly low input impedance (<1Mohm)
I put 2 V pp signal to VL through 1Mohm resistor and only get 1 V on the input, as I'd get from resistor divider with 1Mohm INA116 resistance to ground.
This value of input impedance is indirectly confirmed by other measurements taken on other parts of the circuit (not shown here)
Datasheet calls for >10^15 Ohmi input impedance, both differential and common mode.
Any thoughts are greatly appreciated