GB949433A - Improvements in or relating to pressure transducers - Google Patents

Abstract

949,433. Measuring pressure electrically. ROSEMOUNT ENGINEERING A. G. July 19, 1962, No. 27900/62. Heading G1N. A pressure transducer comprises a ring shaped body wall 10 closed at at least one end by a cap 11 a part of which includes a relatively thin flexible section 11A, a pressure inlet 21, a diaphragm 18 which is supported from the ring 10 by a wall 16 itself thinner than the diaphragm 18 and the ring 10, and means, such as differential condenser plates 40, 41 which form a transducer sensitive to diaphragm movement. Two pressure tight spaces divided by the diaphragm 18 are defined by the members 10,11 and a cup member 12 which are welded at 29. Condenser plates 40, 41 are arranged to have the same stiffness as the diaphragm 18 so as to render the assembly insensitive to axial acceleration, and each comprise a metallic disc 42 (Fig. 5) concentrically spaced from a metal ring 44 by glass connectors 46. Metal suspension elements 48 arranged to have the same co-efficient of thermal expansion as the wall member 16, are welded to each ring 44, and by dimples 48A, 55A to the ring 10 so as to support the plates, parallelism with the diaphragm being ensured during this operation by removable T-shaped plastic spacers 52. Lead wires 37A, 37B soldered to plates 40, 41 are brought out through metal tubes set in glass insulators 34. Pressure applied through connections 21, 25 results in upward or downward movement of the diaphragm 18 but deflections of the relatively massive cap are effectively isolated from the ring 10 by the flanged section 11A. Absolute or differential pressures may be measured depending upon whether the space 30 is evacuated and the connector 25 sealed off, or whether both connectors are utilized. Constructions utilizing only one "fixed" condenser plate 40 are envisaged and in an alternative embodiment (Fig. 9 not shown) the condenser plates are made from fused quartz, metallically coated. In a further embodiment (Fig. 10 not shown) a massive pressure tight case has suspended from its cap a ring shaped member within which the diaphragm and condenser plates are attached.