Floating analog input using Arduino with 1m cable
Most of the designs I see in the comments seem overkill for what you are trying to do (BTW: you do realize you are applying negative voltages to your µC, right?). A very simple amplifier could do the trick.

Try this configuration, which is powered from the remote bias node on the µC side:







simulate this circuit &ndash; Schematic created using CircuitLab

If the gain is excessive for your application or you want to DC-couple to the piezo, you can add a resistor on the source of the FET and/or remove C2.