Pressure transducer for determining and / or monitoring pressure of medium

Abstract

The invention relates to a pressure transducer for determining and / or monitoring a pressure of a medium. A pressure measuring transducer comprises a measuring cell (3) and a first pressure sensor (4) arranged in the measuring cell (3), which is supplied with a pressure of a medium (2) on a first face (4a) and with a second pressure on a second face (4b), and an isolating membrane system (5) having a first isolating membrane (6) and a second isolating membrane (7), according to the invention, the first and second insulating membranes (6, 7) each have an axisymmetric deflection, on which a non-axisymmetric, in particular antisymmetric, deflection is superimposed in order to achieve a volume change in the pressure chamber.

Description

Technical Field

[0001] The present invention relates to a pressure measuring transducer for determining and / or monitoring the pressure of a medium. Background Art

[0002] In pressure measurement technology, absolute pressure, differential pressure, and relative pressure measuring transducers are known. An absolute pressure measuring transducer determines the absolutely dominant pressure (i.e., without a vacuum), while a differential pressure measuring transducer determines the difference between two pressures. In the case of a relative pressure measuring transducer, the pressure to be measured is determined relative to a reference pressure, where the ambient atmospheric pressure prevailing in the environment of the relative pressure measuring transducer is used as the reference pressure, such that the so-called gauge pressure or manometric pressure is measured. A large number of such absolute pressure, differential pressure, and relative pressure measuring transducers are manufactured and sold by the Endress+Hauser Group.

[0003] Pressure measuring transducers are used for measuring pressure and / or for controlling and / or automating processes running in plants. Pressure measuring devices are applied in automation technology in a large number of industrial sectors, such as in the chemical industry and the food industry, to name just a few important application areas. Differential pressure measuring devices are particularly used for continuously measuring the pressure difference in measuring media such as liquids, vapors, and gases. What can be determined from the pressure difference is, for example, the filling level of the filling material in a container or the flow rate of the measuring medium through a pipe.

[0004] Pressure and differential pressure measuring transducers have a pressure-sensitive element, i.e., a so-called pressure sensor, which is respectively arranged on two opposite faces having a first pressure and a second pressure. In this case, as a rule, the pressure of the medium does not come into direct contact with the pressure sensor, but in the case of a pressure measuring transducer, it is recorded by means of a process-facing pressure-sensitive isolation membrane, and in the case of a differential pressure measuring transducer, it is recorded by means of two process-facing pressure-sensitive isolation membranes. Each isolation membrane has an isolation membrane layer, which is used for embossing its isolation membrane and limiting the displacement of the isolation membrane in the case of overload. Usually, a pressure transmission liquid is additionally applied, which transmits the pressure of the medium acting on the isolation membrane towards one of the two faces of the pressure sensor via a pressure transmission path.

[0005] In the event of rupture or damage of the isolation membrane, the medium can enter the pressure or pressure difference measuring transducer and contaminate and / or even damage it. To prevent this, the prior art in this field typically uses two isolation membranes arranged parallel to each other to apply an isolation membrane system, where one isolation membrane faces the medium and the other isolation membrane faces the pressure transmission liquid. Between the two isolation membranes is an intermediate space in which a vacuum predominates. For such an isolation membrane system consisting of two isolation membranes arranged parallel to each other, the prior art in this field typically uses so-called sinusoidal isolation membranes. The sinusoidal isolation membrane has a concentric embossed structure, the cross-section of which is in the shape of a sine wave.

[0006] The disadvantage is that when using two sinusoidal isolation membranes for the isolation membrane system, it may happen that in the event of a fault (damage or rupture), the two isolation membranes do not release from each other, and due to their sinusoidal shape and parallel arrangement, they tend to adsorb to each other.

[0007] A further disadvantage is the need for special measures to evacuate the intermediate space. For example, a surrounding annular inner cavity may be required between the two isolation membranes to evacuate air bubbles. Summary of the Invention

[0008] The object of the present invention is to solve the above problems.

[0009] The object of the present invention is achieved by a pressure measuring transducer.

[0010] The pressure measuring transducer for determining and / or monitoring the pressure of a medium according to the present invention comprises:

[0011] a measuring unit, and a first pressure sensor arranged in the measuring unit, the first pressure sensor being supplied with the pressure of the medium on a first side and a second pressure on a second side, and;

[0012] Isolation membrane system, said isolation membrane system having a first isolation membrane and a second isolation membrane, the first isolation membrane and the second isolation membrane being arranged relative to each other such that the first isolation membrane faces the medium and the second isolation membrane faces away from the medium, and further having an intermediate space between the first isolation membrane and the second isolation membrane, the intermediate space being evacuated such that the intermediate space has a vacuum, wherein the first isolation membrane and the second isolation membrane are fixedly held under pressure at their outer peripheral edges to the measuring unit to form a pressure chamber between the second isolation membrane and the measuring unit, wherein the pressure of the medium is transferred via the first isolation membrane and the second isolation membrane to the pressure chamber, wherein the pressure of the medium is transferred via the pressure chamber to the first side of the first pressure sensor, wherein the first isolation membrane and the second isolation membrane each have a deflectable, in particular mutually different, operating range and imprint profile, wherein the pressure chamber is filled with a reference volume such that the first isolation membrane and the second isolation membrane form a reference position, wherein the first isolation membrane and the second isolation membrane are deflectable from the reference position in two directions such that the volume of the pressure chamber can change, and wherein the first isolation membrane and the second isolation membrane each have an axially symmetric deflection, on which an axially asymmetric, in particular antisymmetric, deflection is superimposed to effect a volume change in the pressure chamber.

[0013] According to the invention, there is provided a use of an isolation membrane for a dual membrane system, wherein the isolation membranes for effecting a volume change in the pressure chamber each perform an axially symmetric deflection due to the applied medium pressure, on which an axially asymmetric deflection is superimposed. This provides the advantage that in the event of a fault, the two isolation membranes release from each other more easily than in the case of two sinusoidal membranes, then because each of the inner and outer membranes has to establish its own bending line.

[0014] An advantageous embodiment of the pressure measuring transducer according to the invention provides that the first isolation membrane and the second isolation membrane have different thicknesses.

[0015] Another advantageous embodiment of the pressure measuring transducer according to the invention provides that the first isolation membrane and the second isolation membrane are formed in such a way that the intermediate space can be evacuated without an annular gap. Description of the Drawings

[0016] The invention will now be explained in more detail on the basis of the drawings, the sole drawing of which is shown below:

[0017] Figure 1 is a schematic view of the pressure measuring transducer according to the invention. Detailed Description

[0018] Figure 1Shows a schematic view of the pressure measuring transducer 1 of the present invention for determining and / or monitoring the pressure p of the medium 2. The isolation membrane system 5 is arranged facing the medium 2. The isolation membrane system 5 includes a first isolation membrane 6 and a second isolation membrane 7, and the first isolation membrane 6 and the second isolation membrane 7 are pressure-tightly connected to the measuring unit 3 in the edge region. In this case, the first isolation membrane 6 faces the medium 2, and the second isolation membrane 7 faces away from the medium 2. Between the first isolation membrane 6 and the second isolation membrane 7, a pressure-tight connection with the measuring unit encloses an intermediate space 8, in which a vacuum prevails. Near the second isolation membrane 7, an isolation membrane layer 11 can be formed in the measuring unit 3.

[0019] The two isolation membranes 6, 7 have mutually different deflectable operating ranges and embossing profiles, and are connected to the measuring unit 3 at the outer peripheral edge to form a pressure chamber 10. The pressure chamber 10 is filled with a reference volume such that the first isolation membrane 6 and the second isolation membrane 7 assume a reference position, and the two isolation membranes 6, 7 can deflect in two directions from this reference position such that the volume of the pressure chamber 10 can change. The first isolation membrane 6 and the second isolation membrane 7 according to the present invention are formed in such a way that each isolation membrane has an axisymmetric deflection for realizing the volume change in the pressure chamber 10, and a non-axisymmetric, in particular anti-symmetric, deflection is superimposed on this axisymmetric deflection. In particular, the first isolation membrane 6 and the second isolation membrane 7 formed according to the teachings of EP2300739 B1 are comprehensively referenced and adopted. In particular, reference is made to the content of paragraphs 25 to 81 of the specification of EP2300739 B1.

[0020] Via the pressure chamber 10 and the first pressure transmission pipeline or path 9a, the pressure of the medium 2 is transmitted to the first surface 4a of the pressure sensor 4 arranged in the measuring unit 3. The pressure sensor 4 is supplied with a second pressure on the second surface 4b opposite to the first surface 4a. The pressure measuring transducer 1 can be realized as a relative pressure measuring transducer, which transmits the ambient pressure to the second region 4b of the pressure sensor via the second pressure transmission pipeline or path 9b. Alternatively, the pressure measuring transducer 1 can be embodied as an absolute pressure measuring transducer, wherein the second pressure is thus a vacuum. In addition, the pressure measuring transducer can also be realized as a differential pressure measuring transducer, wherein the second pressure then also contacts the medium via a pressure transmission means preferably equally embodied as an isolation membrane system.

[0021] The measurement signal of the pressure sensor 4 can be transmitted, for example, to an evaluation unit 12, and the evaluation unit 12 is configured to determine the pressure p of the medium 2 based on the measurement signal of the pressure sensor 4.

[0022] List of reference signs

[0023] 1 Pressure measuring transducer

[0024] 2 Medium

[0025] 3 Measuring unit

[0026] 4 Pressure sensor

[0027] 4a First side of the pressure sensor

[0028] 4b Second side of the pressure sensor

[0029] 5 Isolation membrane system

[0030] 6 First isolation membrane

[0031] 7 Second isolation membrane

[0032] 8 Intermediate space

[0033] 9a First pressure transmission path

[0034] 9b Second pressure transmission path

[0035] 10 Pressure chamber

[0036] 11 Membrane layer

[0037] 12 Evaluation unit.

Claims

1. A pressure measuring transducer for determining and / or monitoring the pressure of a medium, comprising: - a measuring cell (3), and a first pressure sensor (4) arranged in the measuring cell (3), the first pressure sensor (4) being supplied with the pressure of the medium (2) on a first side (4a) and with a second pressure on a second side (4b), and - an isolating membrane system (5), the isolating membrane system (5) comprising a first isolating membrane (6) and a second isolating membrane (7), the first isolating membrane (6) and the second isolating membrane (7) being arranged relative to each other such that the first isolating membrane (6) faces the medium (2) and the second isolating membrane (7) faces away from the medium (2), and further comprising an intermediate space (8) between the first isolating membrane (6) and the second isolating membrane (7), the intermediate space (8) being evacuated such that the intermediate space (8) has a vacuum, wherein the first isolating membrane (6) and the second isolating membrane (7) are pressure-tightly fixed to the measuring cell (3) at their peripheral edges to form a pressure chamber (10) between the second isolating membrane (7) and the measuring cell (3), wherein the pressure of the medium (2) is transferred to the measuring cell via the first isolating membrane (6) and the second isolating membrane (7). A pressure chamber (10), wherein the pressure of the medium (2) is transferred to the first surface (4a) of the first pressure sensor (4) via the pressure chamber (10), wherein the first isolation diaphragm (6) and the second isolation diaphragm (7) each have a deflectable, in particular mutually different, working range and embossing profile, wherein the pressure chamber (10) is filled with a reference volume so that the first isolation diaphragm (6) and the second isolation diaphragm (7) form a reference position, wherein the first isolation diaphragm (6) and the second isolation diaphragm (7) can be deflected from the reference position in two directions so that the volume of the pressure chamber (10) can be changed, and wherein the first isolation diaphragm (6) and the second isolation diaphragm (7) each have an axisymmetric deflection, on which a non-axisymmetric, in particular antisymmetric, deflection is superimposed to achieve the volume change in the pressure chamber.

2. The pressure measuring transducer according to claim 1, wherein: The first isolation film (6) and the second isolation film (7) have different thicknesses.

3. The pressure measuring transducer according to claim 1 or 2, wherein: The first isolating membrane (6) and the second isolating membrane (7) are formed in such a way that the intermediate space (8) can be evacuated without an annular gap.

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