age including a sensor for measuring or detecting the chemical entity and pump...http://www.google.com/patents/US4726929?utm_source=gb-gplus-sharePatent US4726929 - Replaceble modules with flow passageways, pumpAdvanced Patent SearchPublication numberUS4726929 APublication typeGrantApplication numberUS 07/041,650Publication dateFeb 23, 1988Filing dateApr 21, 1987Priority dateJan 25, 1985Fee status