Patent ID: 6865950

Claim:
A pressure monitor comprising a base having a rigid frame; a lid secured to the base to define with the base a substantially fluid tight chamber, at least part of the lid being flexible and forming a diaphragm which will deflect in response to changes in the fluid pressure surrounding the monitor, at least one surface acoustic wave (SAW) device supported within the chamber; an means remote from the edge of the frame for transmitting movement of the diaphragm to the SAW device whereby movement of the diaphragm induced by a change in pressure in a zone surrounding the monitor will result in distortion of the SAW device; and the SAW device comprising surface elements laid down on a substrate, the substrate having, in addition to the zone thereof which is subject to distortion by movement of the diaphragm, at least one other region which is not subject to substantial distortion as a result of movement of the diaphragm, and upon which at least one further set of surface elements are laid down to form at least one further SAW device to provide temperature compensation to the output of the monitor.