A fan case assembly for a gas turbine engine, comprising: a fan with a plurality of blades rotatable within a fan case with a thermally conforming fan case liner therein, the liner and the blades thermally expand or contract radially and define a gap between the liner and a tip of the fan blade; and a gap measuring assembly comprising a capacitance probe mounted to the liner that travels with the liner as the liner expands and or contracts, the capacitance probe being able to sense the gap between the liner and the fan blade tip as the fan blade tip passes relative to the liner; the capacitance probe being disposed within a housing and being attached to the liner, said capacitance probe including: a circuit board sensor including a capacitor and a metallic plate, the metallic plate disposed within an insulating material; a soft lead extending from the housing and being embedded in the liner and being flexible and movable with the liner as the liner thermally expands, the soft lead carries electronic information from the circuit board sensor to another electronic device; and the housing having a base and a cap, the base having a notch through which the soft lead passes, the circuit board sensor construction being so that the circuit board sensor is modifiable without damaging the capacitance probe, including adding, removing or adjusting capacitors on the circuit board sensor. a fan with a plurality of blades rotatable within a fan case with a thermally conforming fan case liner therein, the liner and the blades thermally expand or contract radially and define a gap between the liner and a tip of the fan blade; and a gap measuring assembly comprising a capacitance probe mounted to the liner that travels with the liner as the liner expands and or contracts, the capacitance probe being able to sense the gap between the liner and the fan blade tip as the fan blade tip passes relative to the liner; the capacitance probe being disposed within a housing and being attached to the liner, said capacitance probe including: a circuit board sensor including a capacitor and a metallic plate, the metallic plate disposed within an insulating material; a soft lead extending from the housing and being embedded in the liner and being flexible and movable with the liner as the liner thermally expands, the soft lead carries electronic information from the circuit board sensor to another electronic device; and the housing having a base and a cap, the base having a notch through which the soft lead passes, the circuit board sensor construction being so that the circuit board sensor is modifiable without damaging the capacitance probe, including adding, removing or adjusting capacitors on the circuit board sensor. a circuit board sensor including a capacitor and a metallic plate, the metallic plate disposed within an insulating material; a soft lead extending from the housing and being embedded in the liner and being flexible and movable with the liner as the liner thermally expands, the soft lead carries electronic information from the circuit board sensor to another electronic device; and the housing having a base and a cap, the base having a notch through which the soft lead passes, the circuit board sensor construction being so that the circuit board sensor is modifiable without damaging the capacitance probe, including adding, removing or adjusting capacitors on the circuit board sensor.