DE102019111695A1 - Measuring device - Google Patents

Abstract

The invention relates to a measuring device (1) for determining a pressure and a dielectric value of a medium (3) located in a container (2). The pressure measurement is based on the capacitive measuring principle, according to which an electrode (14a, 14b) of a capacitor is arranged on a pressure-deformable measuring membrane (12) and on an opposing base body (11). According to the invention, the dielectric value is determined in that the electrode (14b) of the measuring membrane (12) is designed with a defined recess (16). Such a measurement signal (sx) is applied to a third electrode (17), which has approximately the shape of the recess (16) and which is arranged in the pressure chamber (13) on the base body (11) congruent with the recess (16) the third electrode (17), so that a dielectric value of the medium (3) can be determined by evaluating a corresponding received signal (sr) at the second electrode (14b). With the structure according to the invention, the pressure and the dielectric value can thus be determined independently of one another with the same measuring device.

Description

The invention relates to a measuring device and a corresponding method for determining the pressure and the dielectric value of a medium in a container.

In automation technology, in particular in process automation technology, field devices are often used which are used to record and / or to influence process variables of corresponding process media. To record process variables, sensors are used that are used, for example, in level measuring devices, flow measuring devices, pressure and temperature measuring devices, pH redox potential measuring devices, conductivity measuring devices, etc. They record the corresponding process variables, such as level, flow, pressure, temperature, pH value, redox potential or conductivity. Many of these field devices are manufactured and sold by Endress + Hauser.

In the case of pressure measurement, the pressure is often measured on the basis of the deformation of a measuring membrane with the pressure being supplied on one side. The measuring membrane can be designed as an integrated part of a semiconductor structure. Such a sensor is for example in the publication WO 03/106952 A2 described. In addition, ceramics (for example Al ₂ O ₃ ) or corrosion-resistant metals can also be used as membrane materials. The pressure chamber, which in principle has to be formed on the rear between the membrane and a non-deformable base body, is designed depending on whether the pressure sensor is used to determine a relative, differential or absolute pressure. In the case of relative or differential pressure measurement, the pressure chamber is completely closed and a vacuum or a constant reference pressure is applied. When measuring differential pressure, the pressure chamber is open to that pressure system for whose pressure the differential pressure is to be determined (that is, for example, to the ambient atmosphere).

The mechanical deformation of the measuring membrane is converted into an electrical measuring signal using the (piezo) resistive or capacitive principle. This means that one or more resistive or capacitive elements are arranged on the measuring membrane, the resistance or capacitance of which changes with the deformation.

In the field of process automation technology, various pressure measuring devices are already known from the state of the art: In the utility model DE 20 2016 101 491 U1 For example, a temperature compensation of the pressure measurement in a ceramic-based pressure measurement device for process automation technology is described. In this case, the temperature on the membrane is measured by an infrared sensor.

In addition to the pressure in the container, depending on the application, it is desirable to be able to determine additional properties of the medium in the container. A meaningful quantity here is the dielectric value or the permeability value. The determination of the dielectric value (also known as "dielectric constant" or "relative permittivity") of media in containers is of great interest, among other things, in gaseous or liquid media, as this value can represent a reliable indicator of contamination, moisture content or material composition. According to the state of the art, the capacitive measuring principle can also be used to determine the dielectric value. This makes use of the effect that the capacitance of a capacitor changes proportionally with the dielectric value of the medium that is located between the two electrodes of the capacitor. In addition, it is also possible to measure the dielectric value by means of transit time or phase measurement of high-frequency signals. Measuring devices that work according to such a measuring principle are sold, for example, by the company IMKO under the product name TRIME®.

Since it is of interest in many processes to know both the pressure and the dielectric value of the process medium currently present, it is necessary to use two separate measuring devices for this purpose, since the measurement signal of one measured variable can in principle be influenced by the other measured variable.

The invention is therefore based on the object of providing a measuring device with which both the pressure and the dielectric value of a gaseous medium in a container can be determined.

• - Einen Grundkörper,
• - eine Messmembran, die derart ausgestaltet und auf dem Grundkörper angeordnet ist,
  • • dass die Messmembran zum Grundkörper hin eine Druckkammer einschließt, und
  • • dass die Messmembran in Abhängigkeit des zu messenden Druckes, der von einer dem Grundkörper abgewandten Fläche auf die Messmembran wirkt, verformbar ist,
• - einen Kondensator, mit
  • • einer ersten Elektrode, die in der Druckkammer am Grundkörper angeordnet ist, und
  • • einer zweiten Elektrode, die derart an der Messmembran in der Druckkammer angeordnet ist, dass eine erste Kapazität des Kondensators vom Druck abhängig ist,
• - eine Auswertungs-Einheit, die ausgestaltet ist, um anhand der ersten Kapazität des Kondensators den Druck des Mediums zu bestimmen.

The invention solves this problem with a measuring device for determining a pressure and a dielectric value of a medium located in a container. For this purpose, the measuring device comprises:

• - a basic body,
• - A measuring membrane which is designed and arranged on the base body,
  • • that the measuring membrane encloses a pressure chamber towards the base body, and
  • • that the measuring membrane is deformable depending on the pressure to be measured, which acts on the measuring membrane from a surface facing away from the base body,
• - a capacitor, with
  • • a first electrode, which is arranged in the pressure chamber on the base body, and
  • • a second electrode which is arranged on the measuring membrane in the pressure chamber in such a way that a first capacitance of the capacitor depends on the pressure,
• - An evaluation unit which is designed to determine the pressure of the medium on the basis of the first capacitance of the capacitor.

In the context of the invention, the term “unit” is understood to mean in principle any electronic circuit that is designed to be suitable for the intended use. Depending on the requirements, it can therefore be an analog circuit for generating or processing corresponding analog signals. However, it can also be a digital circuit such as an FPGA or a storage medium in conjunction with a program. The program is designed to carry out the corresponding process steps or to apply the necessary arithmetic operations of the respective unit. In this context, different electronic units of the measuring device in the sense of the invention can potentially also access a common physical memory or be operated by means of the same physical digital circuit.

• - Eine definiert geformte Aussparung in der zweiten Elektrode,
• - eine dritte Elektrode, die in etwa die Form der Aussparung aufweist, und die in der Druckkammer am Grundkörper in etwa deckungsgleich zur Aussparung der zweiten Elektrode angeordnet ist.

Dabei ist die Auswertungs-Einheit ausgelegt, ein derartiges Messsignal an der dritten Elektrode einzuprägen, dass durch Auswertung eines entsprechenden Empfangssignals an der zweiten Elektrode ein Dielektrizitätswert und/oder ein Permeabilitätswert des Mediums bestimmbar ist.According to the invention, the measuring device is characterized by:

• - A defined shaped recess in the second electrode,
• a third electrode which has approximately the shape of the recess and which is arranged in the pressure chamber on the base body approximately congruently with the recess of the second electrode.

The evaluation unit is designed to impress such a measurement signal on the third electrode that a dielectric value and / or a permeability value of the medium can be determined by evaluating a corresponding received signal at the second electrode.

The third electrode in connection with the recess makes it possible according to the invention to measure the dielectric value without significantly influencing the pressure measurement on the first capacitor. In addition, due to this conception, the measuring device can in principle be designed with the same compactness with regard to the measuring membrane as is the case with pure pressure measuring devices based on the capacitive measuring principle.

In principle, it is not specified within the scope of the invention in which form the evaluation unit must generate the measurement signal to control the third electrode. There are at least two options for generating the measurement signal: the evaluation unit can generate the measurement signal as an electrical high-frequency signal, in particular with a frequency between 400 MHz and 20 GHz, provided it includes a corresponding high-frequency generator. In this case, a corresponding electromagnetic high-frequency signal is emitted at least in the near field via the third electrode and received at the second electrode. Since the transmission of the electromagnetic high-frequency signal in the medium depends on its dielectric value, the evaluation unit can, with appropriate design, determine the dielectric value or the permeability value by measuring an amplitude, a phase shift, a frequency-dependent amplitude spectrum, a transit time of the received signal in relation to the measurement signal or a combination of several of these metrics.

To generate the measurement signal, the evaluation unit can alternatively also be designed such that a second capacitance between the third electrode and the second electrode can be determined on the basis of the received signal. For example, the impedance between the second and the third electrode and thus the capacitance between the third electrode and the second electrode can be determined by means of an AC voltage signal. In this case, the evaluation unit must accordingly be designed in such a way that it can determine the dielectric value or the permeability value of the medium on the basis of the second capacitance, for example by means of a look-up table. The look-up table can be created, for example, by means of a corresponding calibration measurement for a medium with a known dielectric value.

According to the invention, the shape of the recess and the third electrode is also not permanently specified: If the measuring membrane is round, it is advisable that the recess and third electrode are also designed approximately in the form of a ring. However, a meandering, rectangular or spiral design of the recess and the third electrode is also conceivable.

To improve the stability of the pressure measurement, the measuring device can be expanded in such a way that an annular fourth electrode is arranged around the third electrode in the pressure chamber on the base body, the area of which in particular corresponds approximately to the area of the first electrode.

In this case, the evaluation unit must be designed to determine the pressure of the medium on the basis of a capacitance difference between the capacitance of the first capacitor and a third capacitance between the first electrode and the fourth electrode. The sensitivity of the dielectric value measurement can be increased if the third electrode has an area which is at least 5%, in particular approx. 20% smaller than the area of the recess. This ensures that an increased proportion of the measurement signal from the third electrode is emitted through the recess into the medium.

• - Bestimmung der ersten Kapazität des ersten Kondensators,
• - Bestimmung des Druckes des Mediums anhand der ersten Kapazität,
• - Einprägung des Messsignals an der dritten Elektrode, und
• - Bestimmung des Dielektrizitätswertes des Mediums anhand des entsprechenden Empfangssignals an der zweiten Elektrode.

Dabei kann der Druck und der Dielektrizitätswert je nach Leistungsfähigkeit der Auswertungs-Einheit entweder zeitgleich oder zyklisch abwechselnd bestimmt werden.Analogously to the measuring device according to the invention, the object on which the invention is based is achieved by a corresponding method for operating the measuring device. The process comprises the following steps:

• - Determination of the first capacitance of the first capacitor,
• - Determination of the pressure of the medium based on the first capacity,
• - Imprinting of the measurement signal on the third electrode, and
• - Determination of the dielectric value of the medium based on the corresponding received signal at the second electrode.

The pressure and the dielectric value can be determined either simultaneously or alternately, depending on the performance of the evaluation unit.

• 1: Eine schematische Darstellung der erfindungsgemäßen Messvorrichtung an einem Behälter,
• 2: eine Querschnittsdarstellung der erfindungsgemäßen Messvorrichtung, und
• 3: eine Draufsicht auf die Elektroden der Messvorrichtung.

The invention is explained in more detail using the following figures. It shows:

• 1 : A schematic representation of the measuring device according to the invention on a container,
• 2 : a cross-sectional view of the measuring device according to the invention, and
• 3 : a plan view of the electrodes of the measuring device.

For a general understanding of the measuring device according to the invention 1 is in 1 a schematic arrangement of the measuring device 1 on a container 2 shown. In the container 2 is a gaseous or liquid medium 3 such as a natural gas: To determine the dielectric value of the medium 3 and the pressure in the container 2 is the measuring device 1 on the side of a connection on the container 2 , for example. A flange connection. There is a pressure-sensitive measuring membrane 12 the measuring device 1 attached approximately positively to the inner wall of the container. In the field of application of the test technology, the pressure p to be measured potentially extends over a wide range from 1 mBar up to 40 bar.

The measuring device 1 can with a parent unit 4th , for example a process control system. "PROFIBUS", "HART", "Wireless HART" or "Ethernet" can be implemented as the interface. The determined pressure or the dielectric value can be transmitted as an amount or as a complex value with real part and imaginary part. However, other information about the general operating state of the measuring device can also be used 1 be communicated.

2 illustrates the structural design of the measuring device according to the invention 1 : As is known from prior art capacitive pressure measurement, the measuring device is based 1 on a base body 11 to which the measuring membrane 12 is appropriate. The basic body 11 is designed so that between it and the measuring membrane 12 a pressure chamber 13 is included. With the capacitive measuring principle, the pressure to be measured becomes p that surface of the measuring membrane 12 fed to the pressure chamber 13 or the base body 11 is turned away. Accordingly, this area is the measuring membrane 12 after installation in the process plant the interior of the container 2 , in which the pressure p is to be determined, facing. In the context of the invention, the container can also be, for example, a pipe of a process plant.

Depending on whether the pressure measuring device 1 is used for absolute or gauge pressure measurement is the pressure chamber 13 the measuring device 1 either with a vacuum or with a constant reference pressure. A possible design of the measuring device is not shown 1 for differential pressure measurement in which the pressure chamber 13 has an opening for connection to a corresponding differential pressure system (for example the ambient atmosphere).

As is already known with capacitive pressure measurement, it is located in the pressure chamber 13 the measuring device 1 a first capacitor 14th . Here this capacitor 14th from a first electrode 14a that are on the base body 11 is arranged, and a second electrode 14b that of the first electrode 14a in the pressure chamber 13 roughly opposite on the measuring membrane 12 is arranged, formed. The capacitance C of the first capacitor 14th can be approximately described by the formula for plate capacitors: $$\text{C.}=\frac{{\epsilon }_0{\epsilon }_r{r}^2}{l}$$

In relation to the measuring device 1 I corresponds to the distance between the two electrodes 14a , 14b of the first capacitor 14th , or the height of the pressure chamber 13 . In the case of a silicon-based measuring membrane 12 a distance I of at least approx. 1 µm is selected as standard in the undeflected state, while the distance I when using ceramic is measured to be at least approx. 20 µm. The dimension r is in the case of a round design of the electrodes 14a , 14b around their radius. The in 1 The arrangement shown experiences the first capacitor 14th a change in capacitance when the pressure p changes, which acts on the surface of the measuring membrane 12 that the pressure chamber 13 or the base body 11 is turned away, acts. As from the formula for the capacitance C of the first capacitor 14th is suggested, it is also known to amplify the change in capacitance for a given change in pressure p, the pressure chamber 14th to be filled with a dielectric material (e.g. corresponding oils or comparable fluids) with a dielectric value ε _r greater than 1. Typically the first capacitor 14th designed so that its capacitance C is in the range of a few pF up to approx. 100 nF.

zunutze gemacht werden. Entsprechend der Formel hat unter anderem das Elastizitätsmodul E des verwendeten Messmembranmaterials (vorwiegend Silizium oder eine Keramik, insbesondere Al₂O₃) Einfluss auf die Membranauslenkung. Außerdem liegt der Formel die Annahme zugrunde, dass die Messmembran 12 kreisrund mit einem definierten Durchmesser d ausgelegt ist. Bei dem in 2 dargestellten Aufbau entspricht die Messmembranauslenkung der maximalen Änderung des Abstandes zwischen den Elektroden 14a, 14b in der Mitte der Messmembran 12. Außerdem kann zur Bemaßung der Dicke t der Messmembran 12 kann die Formel $$\mathrm{\Delta }\text{lmax=}\frac{1}{2}\text{l}@p_{max}$$

als Bemessungsgrundlage verwendet werden. Durch die planare Anordnung der Elektroden 14a, 14b ist es möglich, diese beispielsweise als Leiterbahn auszulegen oder mittels mikrostrukturier-fähiger Metallisierungstechnologien, wie Sputtern oder CVD („Chemical Vapor Deposition“), herzustellen.Thus, the capacitance C of the capacitor 14th a dedicated pressure value p can be assigned, for example after a corresponding calibration of the measuring device 1 . The measuring range of the feedable pressure p depends on the dimensioning of the capacitance C of the capacitor 14th essentially depends on the design of the measuring membrane geometry (for example, undersizing the thickness of the measuring membrane 3 lead to a diaphragm rupture if the pressure p is too high; If the thickness is oversized, the deflection ΔI of the measuring membrane is 12 too small to change the capacitance of the capacitor 14th to effect). In the case of silicon, the diameter becomes d of the measuring diaphragm 12 in practice measured at approx. 1.5 mm, in the case of ceramic the diameter d is designed to be slightly higher at approx. 1 cm. For a suitable design of the geometry of the measuring membrane 12 depending on the pressure p, the relationship that can be derived from the statics can also be established $$\mathrm{\Delta }\text{l}\left(\text{p}\right)=\text{p}\ast \frac{d^{\mathrm{4th}}}{\mathrm{<figure-callout\; id="3"\; label="6th\; E.\; t"\; filenames="DE102019111695A1\_0004.png"\; state="\{\{state\}\}">6th</figure-callout>}\mathrm{E.}{t}^{}{}^3}$$

can be used. According to the formula, the modulus of elasticity E of the measuring membrane material used (primarily silicon or a ceramic, in particular Al ₂ O ₃ ) has an influence on the membrane deflection. In addition, the formula is based on the assumption that the measuring membrane 12 is designed to be circular with a defined diameter d. The in 2 The structure shown corresponds to the measuring membrane deflection of the maximum change in the distance between the electrodes 14a , 14b in the middle of the measuring membrane 12 . In addition, to dimension the thickness t of the measuring membrane 12 can the formula $$\mathrm{\Delta }\text{lmax =}\frac{1}{2}\text{l}@p_{max}$$

can be used as a tax base. Due to the planar arrangement of the electrodes 14a , 14b It is possible, for example, to design them as a conductor track or to manufacture them using metallization technologies that can be microstructured, such as sputtering or CVD (“Chemical Vapor Deposition”).

As in 2 is indicated are the first electrode 14a and the second electrode 14b of the capacitor 14th electrically each with an evaluation unit 15th connected. Thus the evaluation unit can 15th by determining the capacitance C of the capacitor 14th the pressure in the container 2 determine. The contacting of the electrodes 14a , 14b for example via corresponding bushings in the base body 11 respectively.

To determine the dielectric value or the permeability, the measuring device 1 according to the invention a defined shaped recess 16 in the second electrode 14b on the measuring membrane 12 as in the top view in 3 is shown. Corresponding to this is in the pressure chamber 13 on the main body 11 a third electrode 17th roughly congruent with the recess 16 the second electrode 14b arranged. The third electrode 17th basically the same shape of the recess 16 on. At the in 3 The variant shown are the recess 16 and the third electrode 17th designed in a ring, with a web 18th the inner area of the second electrode 14b electrically connects to their outer area. For the purposes of the invention, instead of an annular design, it is also conceivable to use the recess 16 and the third electrode 17th with a different shape, such as a meander shape, a rectangular shape or a spiral shape.

This design of the second electrode 14b with a recess 16 and a third electrode of the same shape 17th on the main body 11 allows a second capacitor 14b , 17th between the second electrode 14b and that of the third electrode 17th form, the space of this second capacitor 14b , 17th in contrast to the first capacitor 14a , 14b dielectric of the medium 3 being affected. The evaluation unit can accordingly 15th a measurement signal s _x on the third electrode 17th imprint, so that by evaluating a corresponding received signal s _r on the second electrode 14b a dielectric value and / or a permeability value of the medium 3 is determinable. This configuration with the additional second capacitor 14b , 17th the pressure and the dielectric value can thus be measured with a single measuring device 1 determine without the pressure the received signal s _r to determine the dielectric value, and vice versa. As in 2 and 3 is indicated, the sensitivity for determining the dielectric value can be increased if the area of the third electrode 17th at least 5% and up to 25% smaller than the area of the corresponding recess 16 is.

In the context of the invention it is not strictly prescribed with which characteristic the evaluation unit 15th the measurement signal s _x must generate in order by means of the corresponding received signal s _r to be able to determine the dielectric value or the permeability value. In principle, at least two measuring principles can be used for this: A first possibility is to measure the capacitance of the second capacitor 14b , 17th to determine. Because the capacity due to the recess 16 on the dielectric value or the permeability value of the medium 3 depends, the capacity can be determined by the evaluation unit 15th the corresponding dielectric value or permeability value can be assigned, for example, by means of appropriate calibration.

A second possibility of generating the measurement signal is to use the measurement signal s _x to be generated as a high-frequency signal, in particular with a frequency between 400 MHz and 20 GHz, provided the evaluation unit 15th includes a corresponding high frequency generator. Analogous to radar-based distance or speed measurement, in this case in relation to the measurement signal s _x the transit time, the phase shift or an amplitude attenuation of the received signal s _r be measured. It is also conceivable to create a frequency-dependent spectrum. After a corresponding conversion table has been created, the corresponding dielectric value or permeability value can in turn be assigned by the evaluation unit from at least one of these measured variables 15th . If the measurement signal s _x is generated as a high-frequency signal and the third electrode is designed ring-shaped or with a circumferential contour, it is also advantageous if in the third electrode 17th the circulation by an interruption 19th is electrically separated, around which the high frequency signal in the third electrode 17th expressed as a standing wave.

At the in 2 and 3 shown embodiment of the measuring device 1 is on the main body 11 in the pressure chamber 13 around the third electrode 17th around a fourth electrode 14c arranged in a ring. The outside diameter corresponds to the fourth electrode 14c the outer diameter of the second electrode 14b on the measuring membrane 12 . With this design, the evaluation unit determines 15th the pressure of the medium 3 not just based on the capacitance of the first capacitor 14a , 14b , but based on a capacitance difference between the capacitance of the first capacitor 14a , 14b and a third capacitance between the first electrode 14a and the fourth electrode 14c . By measuring this differential capacitance, a potentially better stability of the pressure measurement is achieved. It is advantageous here if the area of the fourth electrode is approximately the area of the first electrode 14a corresponds to the first capacitor 14a , 14b and the third capacitor 14a , 14c have roughly the same capacity.

Instead of this differential determination of the pressure p, the fourth electrode 14c of course also on the potential of the first electrode 14a be interconnected so that the evaluation unit 15th the pressure only through the capacity of the first capacitor 14a / c , 14b certainly. It is conceivable in the context of the invention that the evaluation unit 15th determines the pressure and the dielectric value at the same time. Depending on the operating mode, a cyclically alternating determination of the pressure and the dielectric value or the permeability value is also possible.

List of reference symbols

1

Measuring device

2

container

3

medium

4th

Parent unit

11

Base body

12

Measuring membrane

13

Pressure chamber

14th

a, b First capacitor / electrodes of the first capacitor

15th

Evaluation unit

16

Recess

17th

Third electrode

18th

web

19th

Interruption

s _x

Measurement signal

s _r

Received signal

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• WO 03/106952 A2 [0003]
• DE 202016101491 U1 [0005]

Claims (10)

Measuring device for determining a pressure and a dielectric value of a medium (3) located in a container (2), comprising: - a base body (11), - a measuring membrane (12) which is designed and arranged on the base body (11), • that the measuring diaphragm (12) encloses a pressure chamber (13) towards the base body (11), and • that the measuring diaphragm (12) acts on the measuring diaphragm (12) as a function of the pressure to be measured from a surface facing away from the base body (11) ) acts, is deformable, - a capacitor (14a, b), with • a first electrode (14a), which is arranged in the pressure chamber (13) on the base body (11), and • a second electrode (14b), which is arranged on the measuring membrane (3) in the pressure chamber (13) that a first capacitance of the capacitor (5) depends on the pressure, - an evaluation unit (15) which is designed to use the first capacitance of the capacitor ( 5) to determine the pressure of the medium (3), marked by - a defined shaped recess (16) in the second electrode (14b), - a third electrode (17) which has approximately the shape of the recess (16) and which is in the pressure chamber (13) on the base body (11) is arranged approximately congruent with the recess (16) of the second electrode (14b), the evaluation unit (15) being designed to impress such a measurement signal (s _x ) on the third electrode (17) that by evaluating a corresponding received signal (s _r ) at the second electrode (14b) a dielectric value and / or a permeability value of the medium (3) can be determined. Device according to Claim 1 , characterized in that the evaluation unit (15) for generating the measurement signal (s _x ) as an electrical high-frequency signal comprises a high-frequency generator, wherein the evaluation unit (15) is designed to measure the dielectric value or the permeability value by measuring an amplitude , a phase shift, a frequency-dependent amplitude spectrum or a transit time of the received signal (s _r ). Device according to Claim 2 , characterized in that the high-frequency generator is designed to generate the high-frequency signal (s _x ) with a frequency between 400 MHz and 20 GHz. Device according to Claim 1 , characterized in that the evaluation unit (15) is designed to generate the measurement signal (s _x ) in such a way that, based on the received signal (s _r ), a second capacitance between the third electrode (17) and the second electrode (14b) can be determined, the evaluation unit (15) being designed to determine the dielectric value or the permeability value of the medium (3) on the basis of the second capacitance. Device according to one of the preceding claims, characterized in that the recess (16) and third electrode (17) are designed to be approximately ring-shaped, meandering or spiral-shaped. Device according to Claim 5 , characterized in that an annular fourth electrode (14c) is arranged in the pressure chamber (13) on the base body (11) around the third electrode (17), the area of which corresponds in particular approximately to the area of the first electrode (14a), wherein the evaluation unit (15) is designed to measure the pressure of the medium (3) using a capacitance difference between the capacitance of the first capacitor (14a, 14b) and a third capacitance between the first electrode (14a) and the fourth electrode (14c ) to be determined. Device according to one of the preceding claims, characterized in that the third electrode (17) has an area which is at least 5%, in particular approx. 20% smaller than the area of the recess (16). Method for determining the pressure and dielectric value of a medium located in a container by means of the device according to one of the preceding claims, comprising the following method steps: - determining the first capacitance of the first capacitor (14), - determining the pressure of the medium (3) on the basis of the first capacitance, - impression of the measurement signal (s _x ) on the third electrode (17), and - determination of the dielectric value of the medium (3) on the basis of the corresponding received signal (s _r ) on the second electrode (14b). Method according to claim according to Claim 8 , whereby the pressure and the dielectric value are determined at the same time. Procedure according to Claim 8 , whereby the pressure and the dielectric value are determined cyclically alternately.

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