An apparatus which is particularly useful in measuring dielectric changes in materials, even when subjected to abrasive and/or high-pressure environments. The apparatus includes a housing adapted to mounting within a vessel containing the material to-be-tested, the housing presenting at least one exposed...http://www.google.com.tw/patents/US5184077?utm_source=gb-gplus-share專利 US5184077 - Abrasion-resistant, high pressure dielectric sensors
