Differential pressure sensor for determining the differential pressure between two pressures

A differential pressure sensor for determining the differential pressure between two pressures in a process, the sensor comprising:

• a converter chamber including a differential pressure measuring cell including a pressure-sensitive element disposed in the converter chamber;
• and
• a measuring unit comprising:
• a base body including an end portion configured to face the process;
• and
• a coplanar double-membrane system disposed in the end portion of the base body and including a first double membrane and a second double membrane,
• wherein each double membrane comprising a separating membrane and an overload membrane arranged behind the separating membrane relative to a direction of action of pressure from the process,
• wherein a first pressure chamber is defined between a first separating membrane and a first overload membrane of the first double membrane, and a first additional pressure chamber is defined between the first overload membrane and the base body of the measuring unit,
• wherein a second pressure chamber is defined between a second separating membrane and a second overload membrane of the second double membrane, and a second additional pressure chamber is defined between the second overload membrane and the base body of the measuring unit,
• wherein each of the first and second pressure chambers is connected to a corresponding capillary connection, and each of the first and second additional pressure chambers is connected to at least one further capillary connection,
• wherein each capillary connection is configured and coupled such that pressures present at the first and second separating membranes are hydraulically transmitted to the pressure-sensitive element during normal measuring operation and such that,
• when an overpressure is present at the first separating membrane or second separating membrane, thereby defining a high-pressure side and a low-pressure side, respectively, the overpressure is hydraulically transmitted from the high-pressure side to the low-pressure side via a hydraulic fluid such that the first or second overload membrane and the first or second separating membrane corresponding to the low-pressure side are deflected, and hydraulic fluid displaced from the high-pressure side is received in the respective first or second additional pressure chamber of the low-pressure side before the overpressure acts upon the pressure-sensitive element,
• wherein the base body of the measuring unit is configured as a single piece and has a substantially fully symmetrical construction, at least relative to the coupling of the capillary connections, with respect to a plane extending centrally and perpendicularly between the first double membrane and the second double membrane of the coplanar double-membrane system,
• wherein the first and second overload membranes are preloaded such that each bears against the base body of the measuring unit in a substantially form-fitting manner during normal measuring operation and such that, only when an overpressure endangering the pressure-sensitive element is exceeded, the first overload membrane corresponding to the low-pressure side is lifted off the base body due to the overpressure, while the second overload membrane on the high-pressure side is pressed against the base body.