Abstract: A fluid pressure sensing device for a fluid-containing vessel, and a method of assembling said device, is disclosed. A metallic diaphragm is preferably laser-fused to one end of the sensing device to define the end surface thereof. The sensing device is preferably mounted and sealed with the wall of the vessel such that the diaphragm and such sealing engagement is substantially flush or coplanar with the inside surface of the wall. A passageway extending through the sensing device admits an indicator fluid to one side of the diaphragm for measuring the pressure of the fluid in the vessel. The passageway also includes an adjustable nozzle for pre-calibrating the sensing device.

Abstract: An apparatus for measuring fluid pressures which comprises a gas-type pressure sensor and a sensor control for supplying controlled purge gas to the sensor and for receiving vent gas from the sensor. The apparatus further includes a unique pressure-reducing device operable in response to a differential gas pressure in the sensor control for creating a zone of pressure less than any other in the apparatus, which zone is placed in fluid communication with gas in the apparatus to reduce the overall pressure thereof. This permits the accurate measuring of pressure at or below atmospheric. An integral design and a retrofit design are disclosed.