Hewlett-packard Company

John S Craven

David E Clouser

A sample fluid and a reference fluid are alternately applied to a fluid detector and an output signal is derived that is proportional to the difference between the response of the detector to the fluids.

Modulated fluid detector

A thermal conductivity detector in which sample gas and reference gas are made to alternately flow through a thermal conductive cell at a given switching frequency and in which the output signal is applied to a synchronous detector wherein it is mixed with a control wave that is in phase quadrature with the flow component of the output signal.

Phase discrimination in modulated thermal conductivity detector

A thermal conductivity cell is provided that is made of cast wafers of ceramic material having a groove in one or both planar abutting surfaces. A filament is mounted in the groove by attachment to the ends of electrical conductors that extend through one of the wafers in sealed relationship. Passageways extend between points in the groove and an exterior surface of the cell. Gaskets are formed on the exterior surface around the openings where the passageways emerge. The gaskets are formed by silk screening and firing one or more layers of thick film conductor paste onto the surface of a layer of thick film conductor paste and at least one superimposed layer of gold and binder.

Growing community of inventors

West Grove, PA, United States of America

John S Craven