Which material has the shortest detection distance range for a capacitive sensor?

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Capacitive sensing relies on detecting changes in capacitance caused by an object entering the sensor’s electric field. The amount of change is driven by the object's dielectric properties and, for conductive objects, by how the field interacts with the material.

Non-conductive materials like wood and plastic have lower but steady dielectric constants, so they perturb the field enough to be sensed at a moderate distance. Liquids—especially water-containing ones—often have higher dielectric constants, which can enhance coupling and extend detection range in many cases.

Metal is different because it’s highly conductive. When a metal object approaches, the field lines are pulled into the conductor and eddy currents form, rapidly distorting and effectively shielding the sensor’s field. This strong interaction causes the capacitance change to occur only at very close proximity, giving the shortest possible detection range for a capacitive sensor.