Differential pressure sensor

Claim 1

A differential pressure sensor which detects a difference between two fluid pressures and provides an output signal indicative thereof, said differential pressure sensor being characterized by: first and second pistons, each including generally opposed first and second faces; means connecting said first and second pistons for joint movement thereof, said joint movement comprising said output signal; means sealing the first face of each piston from the second face thereof; first means providing fluid communication between one of said pressures and said first surface of said first piston; second means providing fluid communication between the other of said pressures and said first surface of said second piston; third means providing generally unrestricted fluid communication between said second surfaces of said pistons while accommodating leakage through a rupture of said sealing means associated with either of said pistons and applying said leakage to said second surface of the other of said pistons for fail-safe operation of said differential pressure sensor by said other piston; and fourth means providing communication between said third means and said first and second means for applying a pressure which is intermediate said two fluid pressures to both said second piston surfaces, thereby dividing said pressure difference between said first and second pistons under normal operating conditions.