Capacitive Sensors

Capacitive sensors monitor the relative dielectric of different materials to detect the presence of the target, similar to a stud-finder. It has the advantage of being able to tune-out some materials. A common use is to detect liquid level in a plastic tank by sensing through the tank wall. Another is detecting plastic pellet level in the hopper feeding an extruder or injection molding press. Range can vary greatly depending on the dielectric of the material. The same sensor might detect a web splice at 4mm, and a metal flag at one inch. Capacitives greatly outperform inductives in the detection of ferrous metals such as aluminum.