Durable, stable gauge for testing IC engine pressures - uses strain gauge linked to metal diaphragm which is subjected to pressure being measured

摘要

A pressure gauge measures the pressure by a flat metal membrane and an annular thicker mounting which is integral with it and holds it round the rim. The front of the membrane is exposed to the pressure to be tested of a fluid. The back of the membrane has a strain gauge with at least one metallic strain strip and its appropriate contacts. The deformation of the membrane caused by the pressure of the fluid is applied to the (at least one) strip, and the change produced in its electrical resistance is measured. The system has a cup-shaped housing with a chamber between its base and surrounding wall. The gauge is located in this chamber and the annular membrane mounting is bonded airtight to the edge of the chamber wall. The back of the membrane faces the interior of the chamber. A cable with metal outer sleeve has wire leads going through its sleeve and has an insulating guide to hold the wires in position. The cable passes through a hole in the base of the housing to which its sheath is bonded. The wire leads have their ends projecting freely into the chamber, their tips being in electrical contact with the relevant contacts on the strain gauge. Each such projecting end is bent across the axis of the cable and reacts as an elastic leaf spring; as a result the tip of each end is held elastically and only this maintains it in touch with its respective contact. The design preferably includes and adhesive based on polyimide or silicone rubber. The gauge is suitable for use over prolonged periods. It is therefore not only mechanically stable but also it provides stable signals. It is simple and cheap to produce. It is suitable for testing pressures inside I.C. engines. @(7pp Dwg.No.1/9)@