Patent ID: 6418793
Filing Date: 2002-07-16
Classification: G01L

Abstract:
A differential pressure sensor comprising a housing formed of two portions that are assembled together hermetically and that define a closed internal cavity between them, a deformable membrane dividing said internal cavity into two non-communicating chambers which are in communication with sources of fluid under pressure by means of two orifices respectively formed in said portions of the housing, said membrane being made in such a manner as to constitute a plate of first and second variable capacitance capacitors by being associated with two other plates installed in stationary manner in the housing of the sensor on either side of the movable central plate formed by the membrane, and sensor means that are sensitive to deformation of the membrane as a result of a difference between pressures existing in the two chambers in order to produce an electrical signal representative of said pressure difference, wherein the sensor means comprise a measurement circuit for measuring the corresponding capacitances of the first and second variable capacitance capacitors, which circuit is made up of first and second double-sided interconnected circuits, of size similar to that of the membrane, which are respectively disposed in the two non-communicating chambers close to the membrane and substantially parallel to said membrane in such a manner as to divide each of the chambers into two communicating portions, which interconnected circuits are fixed to the membrane in its peripheral region by connection means, faces of the circuits which face the deformable membrane each comprising a region on which the fixed plate of the corresponding first or second variable capacitance capacitor is installed, and faces of the circuits which face away from the membrane each comprising a respective region on which the components that are sensitive to the displacement of the membrane towards one or other of the fixed plates are respectively mounted, and a respective region that is insensitive to stray capacitance, which regions are respectively constituted by peripheral regions of the circuits, another region that is insensitive to stray capacitance being provided on one of said faces facing away from the membrane for mounting the components which form the remainder of the measurement circuit.