Pressure measuring apparatus

Abstract

An apparatus which utilizes solid state piezoresistive strain sensing means to measure the static pressure as well as the differential pressure across a primary element, such as an orifice plate, venturi tube, nozzle or wedge. In a preferred embodiment, the apparatus includes a dual pressure sensing transducer comprising a body, means for applying two different pressures to the body, first and second pressure diaphragms respectively, hermetically sealed to the body at first and second spaced apart portions of the body with a back wall of the second diaphragm forming one wall of a chamber which contains a desired reference pressure, a compliant cantilever beam fixedly mounted at one end thereof to the body, a strut wire coupled between the beam and the first diaphragm to cause deflection of the beam in response to movement of the first diaphragm due to an applied differential pressure, a first plurality of piezoresistive strain elements contained on a thinned portion of the beam for deflection therewith so that movement of the first diaphragm will result in changes in the electrical resistance of the first plurality of elements that are indicative of the differential pressure applied across the first diaphragm, a second plurality of piezoresistive strain elements contained on a front wall of the second diaphragm for deflection therewith so that movement of the second diaphragm in response to the static (line) pressure will result in changes in the electrical resistance of the second plurality of elements that are indicative of the static pressure with respect to the reference pressure.