An electromagnetic fluid flow transducer formed from an electromagnetic assembly having two electromagnet units and a tubular flow contact assembly to measure fluid flow velocity and fluid volume in ionic solutions. Each electromagnet unit includes a core and a winding on the core, and a housing maintains...http://www.google.com.hk/patents/US5220841?utm_source=gb-gplus-share專利 US5220841 - Electromagnetic fluid flow transducer
