Medex, Inc.

John C Toomey

Dennis M Tomisaka

Charles Russell Patzer

Michael P Eland

Warren B Nicholson

Thomas P Frank

Glen D Brunner

A pressure transducer (10) for measuring fluid pressure in a fluid path comprising a strain gauge circuit (37) of thick film piezoresistors formed on an alumina diaphragm (36) in a Wheatstone bridge configuration. Each resistance leg of the bridge typically includes a thick film measuring piezoresistor (R1A) to which selected thick film patch-in piezoresistors (R1B, R1C, R1D, R1E) are selectively connected to create a measuring resistance network (PN1). The measuring resistance network is adjusted to a predetermined resistance value to balance and optimize the electrical symmetry of the bridge. The pressure transducer (10) includes a mechanical stop member (46) located adjacent the alumina diaphragm (36) such that the fully deflected diaphragm contacts the stop thereby physically preventing the diaphragm from deflecting an amount that would cause the diaphragm to rupture.

Low cost pressure transducer particularly for medical applications

In a blood gas sensing probe, a cylindrical sleeve contains an optical fiber. The end of the optical fiber is withdrawn into the sleeve thereby creating a receptacle at the end of the sleeve. A sensitive dye, HOPSA for example, is encapsulated in a gel and deposited in the receptacle to form the probe. In making the probe, the end of the optical fiber is in the same plane as the end of the sleeve in which it is placed. The dye and gel contact the combined ends of optical fiber and sleeve. The fiber is withdrawn into the sleeve thereby creating a vacuum which is filled by the dye and gel.

Method of making an optical fiber probe

A blood chemical sensor has a blood gas sensitive dye contained in a hydrogel matrix, the combination of dye and gel being mounted on the end of an optical fiber. The hydrogel is freeze-dried to facilitate packaging and handling.

Freeze-dried blood gas sensor

Probe for blood gas sensing

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West Worthington, OH, United States of America

John C Toomey