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The thickness of plastic materials can be measured with the material placed between two electrodes a set distance apart. These form a type of capacitor. The plastic when placed between the electrodes acts as a dielectric and displaces air (which has [[dielectric constant]] of 1, different than the plastic). Consequently the capacitance between the electrodes changes. The capacitance changes can then be measured and correlated with the material's thickness.<ref>[http://www.lionprecision.com/tech-library/appnotes/dual-0010-film-thick.html Film thickness gauge]</ref>
Capacitive sensors circuits can be constructed that are able to detect changes in capacitance on the order of a 10<sup>−5</sup> [[Farad|picofarads]] (10 attofarads).<ref>[http://www.patsnap.com/patents/view/US4947131.html U.S. Patent]</ref>
===Non-conductive targets===
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