proximity probe (sensor ) / eddy current pre-conditioning circuit
Capacitive coupling to an opamp circuit will allow the AC through but block the DC but your AC signal will be centred around zero so you may need to use a level shifter to centre at +2.5 volts, in the middle of the ADC input range.

For the DC, take the output from the sensor and use a low pass filter (R and C and or L) to remove the AC component.