forcing an Opamp channel input high via a pic and it operating correctly when...

[TimB]

Hi All a vague title sorry

I have a water level probe system and for the purposes of expediency I just drive a line high and look for the signal when it comes back through and opamp.

During periods of non testing the drive line is converted to an input.

Now I want to start balancing the current flow and that involves me having to connect a pic pin to the op amp input and drive it high and the other pin low. Than back to an input after a time that means the pseudo AC is balanced.
 
Just checking if I will get issues with the signal when that pic drive pin is made an input.

Thanks

Tim
   

[JonW]

If the input is high z then as long as the input signal does not exceed VDD or VSS (plus the esd diodes) then it should work.  Also may depend on what clocks and peripherals you have running and the gain and GBW of your amplifier, some MCU suffer from clock leakage on the pins.