Patent ID: 7841241

Claim:
A SAW based pressure sensor comprising: a base having an aperture formed therein as a through-opening; a substrate mounted on said base so as to completely overlie the aperture, said substrate being adhered to said base so as to form a fluid tight seal around the periphery of the through-opening; a first SAW resonator being mounted on said substrate wholly within the region overlying the aperture and a second SAW resonator being mounted on said substrate wholly within a region which is stiffened by adhesion to the underlying base; and a housing having side walls and a lid which together with said base define a fluid tight internal chamber, said chamber being chargeable with a reference pressure to which the whole of the upper surface of the substrate is exposed, the lower surface of the region of the substrate overlying the aperture being exposed to the atmosphere surrounding the housing, wherein said region distorts in response to a pressure differential between the reference pressure and the surrounding pressure, varying the strain field to which the first SAW is exposed.