Endress + Hauser Gmbh + Co.

Endress U. Hauser Gmbh U. Co.

Peter Jung

Peter Gerst

Karlheinz Banholzer

Evaluation unit of a differential-pressure sensor An evaluation unit of a differential-pressure sensor is provided which supplies an output signal which corresponds to a differential pressure (.DELTA.P) which has been corrected with respect to a measuring error due to the static pressure (P.sub.S). The differential-pressure sensor has a capacitive single-chamber differential-pressure measuring cell with two capacitors (4, 5) as sensor element (1), and a temperature sensor (6) is arranged at the sensor element (1). The differential-pressure measured value is corrected by means of a first correction value (.DELTA.K) which is a measure of the static pressure (P.sub.S) at a reference temperature (T.sub.R). This correction value (.DELTA.K) is determined from the difference between a sensor temperature (T.sub.S) determined by means of the temperature sensor (6) and a sum of a temperature discrepancy (T.sub.0) and an internal temperature (T.sub.i) assigned to the sum (.SIGMA.) of the reciprocal values of the capacitances of the two capacitors (4, 5).

Evaluation unit of a differential-pressure sensor

The differential pressure measuring apparatus comprises a single chamber differential pressure sensor having two resilient sensor diaphragms which enclose a volume filled with a fluid. In the single chamber differential pressure sensor two measuring capacitors are formed whose capacitances vary in opposite senses in response to the sensor differential pressure between the pressures acting on the two sensor diaphragms. The single chamber differential pressure sensor is connected to an adaptor comprising a volume filled with a fluid which is closed on the one hand by one of the two sensor diaphragms and on the other hand by an elastic adaptor diaphragm. An evaluation circuit calculates the sensor differential pressure from the capacitances of the measuring capacitors. The evaluation circuit comprises a first compensation arrangment which compensates the influences of the sensor temperature and of the sensor parameters on the calculated sensor differential pressure, and a second compensation arrangement which compensates the influences of the adaptor temperature and of the adaptor parameters on the sensor differential pressure corrected by the first compensation arrangement.

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Steinen, Germany

Peter Jung