Integrated absolute and differential pressure transducer

Abstract

A method and apparatus integrates differential pressure measurements and absolute pressure measurements to provide virtual absolute pressure measurements over a wide range of pressures on a single integrated scale.

1 . A method of providing an absolute chamber pressure profile of gas pressure in a chamber as the pressure in the chamber changes over time, comprising: 
 measuring absolute pressure in the chamber with an absolute pressure sensor that has an accurate and dependable range of absolute pressure measuring capability;    measuring differential pressure between the chamber and atmospheric pressure with a differential pressure sensor that has an accurate and dependable range of differential pressure measuring capability, which corresponds with at least a portion of the accurate and dependable range of the absolute pressure sensor;    determining a correlation factor between an absolute pressure measurement from the absolute pressure sensor that is considered to be accurate and reliable and a differential pressure measurement from the differential pressure sensor;    using the absolute pressure measurements from the absolute pressure sensor for the absolute chamber pressure profile in pressure ranges where the absolute pressure measurements from the absolute pressure sensors are more accurate and reliable than the differential pressure measurements from the differential pressure sensor; and    using the differential pressure measurements from the differential pressure sensor, adjusted by the correlation factor to provide virtual absolute pressure measurements, for the absolute chamber pressure profile where the differential pressure measurements from the differential pressure sensor are more accurate and reliable than the absolute pressure measurements from the absolute pressure sensor.    
   
   
       2 . The method of  claim 1 , including determining the correlation factor by: 
 measuring the absolute pressure in the chamber at a chamber pressure;    measuring the differential pressure between the atmosphere and the chamber at said chamber pressure; and    subtracting the differential pressure measurement at said chamber pressure from the absolute pressure measurement at said chamber pressure.    
   
   
       3 . A method for measuring absolute pressures in a chamber over a variable pressure range comprising 
 measuring the absolute pressures in the chamber on an absolute pressure scale over a first portion of the variable pressure range with an absolute pressure gauge;    measuring the differential pressure between the chamber and the atmosphere on a differential pressure scale over a second portion of the variable pressure range that partially overlaps the first portion of the variable pressure range;    subtracting a differential pressure measurement measured at a particular chamber pressure from an absolute pressure measurement measured at said particular chamber pressure to determine a correlation factor; and    normalizing the differential pressure measurements in at least some of the second portion of the variable pressure range to said absolute pressure scale by adjusting said differential pressure measurements in at least some of the second portion of the variable pressure range with the correlation factor.