APPARATUS TO MEASURE DIFFERENTIAL PRESSURE WITH SETTABLE PRESSURE REFERENCE

摘要

A differential pressure sensor for sensing changes in pressure at a desired location, which sensor includes a sensing portion and a reference portion to produce an output indicative of the difference therebetween, both the sensin g portion and the reference portion being open to the pressure around the sens or until the sensor is located in the desired sensing location and then the reference portion is closed to capture the pressure then existing at the desired location and any pressure changes thereafter producing signals indicative of the pressure differences.