Patent ID: 7962294

Claim:
A method of providing absolute pressure measurement values of pressures in a chamber on a pressure value scale that extends within and beyond an accurate absolute pressure measuring range of an absolute pressure sensor connected to the interior of the chamber for measuring absolute pressure in the chamber, comprising: connecting a differential pressure sensor to the chamber that can measure differential pressure between the pressure in the chamber and pressure outside of the chamber accurately in a range where the absolute pressure in the chamber is measurable accurately by the absolute pressure sensor; providing a pressure in the chamber in the range where the absolute pressure in the chamber is measurable accurately by the absolute pressure sensor and that is within or below a range where the differential pressure sensor can provide accurate differential pressure measurements, and at that pressure measuring both the absolute pressure in the chamber with the absolute pressure sensor and the differential pressure between the chamber and the outside with the differential pressure sensor; determining a correlation factor by subtracting the differential pressure measurement at that pressure from the absolute pressure measurement at that pressure; setting in a microprocessor a cross-over pressure value , and programming the microprocessor to output as absolute chamber pressure values the absolute pressure measurements from the absolute pressure sensor when such pressure measurements from the absolute pressure sensor are on one side of the cross-over pressure value, and to output as absolute chamber pressure values virtual absolute pressure values determined by adding the correlation factor to the differential pressure measurements from the differential pressure sensor when the pressure measurements from the absolute pressure sensor are on the other side of the cross-over pressure value; and reading the pressure measurements from the absolute pressure sensor and the differential pressure sensor into the microprocessor as the pressure in the chamber varies so that the microprocessor outputs the absolute pressure values of the chamber as the pressure in the chamber varies within and beyond the accurate absolute pressure measuring range of the absolute pressure sensor.