An apparatus and a method for determining and/or monitoring at least one process variable of a medium in a container, comprising: a mechanically oscillatable unit, a driving/receiving unit for exciting the mechanically oscillatable unit to execute mechanical oscillations by means of an electrical exciting signal and for receiving and transducing mechanical oscillations into an electrical, received signal, an electronics unit, which electronics unit is embodied, to produce the exciting signal starting from the received signal, to set a predeterminable phase shift () between the exciting signal and the received signal, and from the received signal, to determine and/or to monitor the at least one process variable. A phase correction unit is provided, which phase correction unit is at least embodied, to ascertain a phase correction value (.sub.kor) from at least one process parameter dependent, characteristic variable of at least one component of the apparatus, especially the driving/receiving unit, and to set the predeterminable phase shift () in accordance with the phase correction value (.sub.kor).

An apparatus and a method for determining and/or monitoring at least one process variable of a medium in a container, comprising: a mechanically oscillatable unit, a driving/receiving unit for exciting the mechanically oscillatable unit to execute mechanical oscillations by means of an electrical exciting signal and for receiving and transducing mechanical oscillations into an electrical, received signal, an electronics unit, which electronics unit is embodied, to produce the exciting signal starting from the received signal, to set a predeterminable phase shift () between the exciting signal and the received signal, and from the received signal, to determine and/or to monitor the at least one process variable. A phase correction unit is provided, which phase correction unit is at least embodied, to ascertain a phase correction value (.sub.kor) from at least one process parameter dependent, characteristic variable of at least one component of the apparatus, especially the driving/receiving unit, and to set the predeterminable phase shift () in accordance with the phase correction value (.sub.kor).

Systems and method to measure pressure are described herein. The system can include a force sensor can that be implanted into a patient to measure, for example, cardiac pressure. The force sensor can include first and second film layers that can define a plurality of pressure cells. An external pressure can deform the pressure cells and change their resonant frequency. When exposed to an acoustic signal, the pressure cells can resonant at a pressure-dependent resonant frequency. The system can detect reflected acoustic waves generated by the resonance of the pressure cells. The system can convert the frequency readings into pressure values.

Systems and method to measure pressure are described herein. The system can include a force sensor can that be implanted into a patient to measure, for example, cardiac pressure. The force sensor can include first and second film layers that can define a plurality of pressure cells. An external pressure can deform the pressure cells and change their resonant frequency. When exposed to an acoustic signal, the pressure cells can resonant at a pressure-dependent resonant frequency. The system can detect reflected acoustic waves generated by the resonance of the pressure cells. The system can convert the frequency readings into pressure values.

A sensor (2) is provided, having an acoustic resonator (18) for containing a fluid such as air and at least one transducer (22, 24) arranged to emit an acoustic signal into the acoustic resonator (18) in response to an excitation signal provided to the transducer (22, 24) by an electronic unit (4). The electronic unit (4) receives a response signal from at least one transducer (22, 24), and processes the excitation signal and the response signal to derive the acoustic signal response of the acoustic resonator. The pressure and/or temperature of the fluid may be derived from the acoustic signal response. More specifically, the electronic unit (4) may derive the temperature of fluid inside the acoustic resonator (18) by obtaining the resonant frequencies of the acoustic signal inside the acoustic resonator (18), or may derive the barometric pressure from the acoustic signal response in the vicinity of the fundamental frequency and its harmonics.

A sensor (2) is provided, having an acoustic resonator (18) for containing a fluid such as air and at least one transducer (22, 24) arranged to emit an acoustic signal into the acoustic resonator (18) in response to an excitation signal provided to the transducer (22, 24) by an electronic unit (4). The electronic unit (4) receives a response signal from at least one transducer (22, 24), and processes the excitation signal and the response signal to derive the acoustic signal response of the acoustic resonator. The pressure and/or temperature of the fluid may be derived from the acoustic signal response. More specifically, the electronic unit (4) may derive the temperature of fluid inside the acoustic resonator (18) by obtaining the resonant frequencies of the acoustic signal inside the acoustic resonator (18), or may derive the barometric pressure from the acoustic signal response in the vicinity of the fundamental frequency and its harmonics.

Downhole distributed pressure sensor arrays include sensor housings each comprising at least one pressure sensor in a pressure housing. Downhole pressure sensors include a housing, at least one pressure sensor in a pressure housing portion of the housing, and at least one isolation element positioned at an outer wall of the housing.

Downhole distributed pressure sensor arrays include sensor housings each comprising at least one pressure sensor in a pressure housing. Downhole pressure sensors include a housing, at least one pressure sensor in a pressure housing portion of the housing, and at least one isolation element positioned at an outer wall of the housing.

An optical pressure sensor, such as a microphone, is constituted by two membranes, but where the sound does not arrive perpendicular to the membrane, but comes in from the side. The membranes may be parallel as in a Fabry-Perot or slightly skew as in an Air-wedge shearing interferometer. The pressure sensor uses interferometric readout, and consists of two membranes with essentially equal characteristics, where at least one of the membranes is partially transmitting and partially reflective and the other membrane is at least partially reflective, the membranes being separated by a cavity defined by a spacer part, where the distance between the membranes is variable to provide a shift sensitive Fabry-Perot resonator, and where the two membranes have a common back volume being sealed or essentially sealed in the frequency one wish to measure, and where a pressure increase results in that the distance between the membranes move in opposite directions.

An optical pressure sensor, such as a microphone, is constituted by two membranes, but where the sound does not arrive perpendicular to the membrane, but comes in from the side. The membranes may be parallel as in a Fabry-Perot or slightly skew as in an Air-wedge shearing interferometer. The pressure sensor uses interferometric readout, and consists of two membranes with essentially equal characteristics, where at least one of the membranes is partially transmitting and partially reflective and the other membrane is at least partially reflective, the membranes being separated by a cavity defined by a spacer part, where the distance between the membranes is variable to provide a shift sensitive Fabry-Perot resonator, and where the two membranes have a common back volume being sealed or essentially sealed in the frequency one wish to measure, and where a pressure increase results in that the distance between the membranes move in opposite directions.