GB1412631A - Differential pressure transducers - Google Patents

Abstract

1412631 Measuring fluid pressure electrically; pressure gauges GEORGE KENT Ltd 10 Oct 1973 [10 July 1972] 32202/72 Headings G1L and GIN A differential pressure transducer for use, e.g. in fluid-flow measuring systems comprises a housing a pair of diaphragms located in the wall of the housing and forming with the housing respective chambers connected to sources of the fluids having the measurable differential pressure, and a rigid member connecting the diaphragms and displaceable in response to the differential pressure. Part of the volume enclosed within the housing is filled with a substantially incompressible fluid; the remainder is filled with a material such that the combined thermal expansion or contraction of the fluid and the material is substantially equal to that of the housing, for avoiding errors that might arise if the diaphragms were both to be deflected outwardly by internal pressure. Each of diaphragms 16 welded to opposite ends of a stainless steel housing 11 is also welded to a retainer ring 17 which forms a fluid pressure chamber 19 sealable by a ring 20. The diaphragms 16 are connected by a stainless steel rod 21 to which electrical connection (not shown) can be made. The space enclosed within the housing is mostly occupied by a pair of borosilicate glass blocks 14; the remainder is filled by a suitable oil through a filler inlet (not shown). A disc 22, which may be formed coaxial with the rod 21, forms one electrode of a differential capacitor, of which the other electrodes are conductive layers 25, 26 deposited on opposed faces of the glass blocks 14 and terminated at connectors 31, 32 via inserts 33, 34 and leads 35, 36. The diaphragms may comprise corrugated discs as illustrated, or bellows. The differential capacitor may be connected into a bridge circuit measuring the displacement of the rod 21 as a function of differential pressure. A force-balance system may be added to restore the rod 21 to a datum position.