DE102016104760A1 - Pressure measuring device - Google Patents

Abstract

It is a pressure measuring device that can be used in a wide temperature range, with a capacitive pressure sensor (1) having a base body (3) and a pressure chamber (5) arranged on the base body (3), depending on a pressure to be measured ( p) deformable measuring membrane (7), the one on the measuring membrane (7) arranged membrane electrode (19, 19a) and one on the base body (3) arranged measuring electrode (21) comprising measuring capacitor (CP) with one of the pressure-dependent deformation of the measuring membrane (7) has dependent capacitance, and has a membrane electrode (19, 19b) arranged on the measuring diaphragm (7) and a reference capacitor (CR) comprising reference electrode (23) arranged on the base body (3), characterized in that a first oscillating electrical circuit which can be excited inductively to oscillations is provided, which comprises the measuring capacitor (CP) and a sensor connected thereto nsorinduktivität (LP), and a second inductively to vibrations excitable electrical oscillating circuit is provided, which comprises the reference capacitor (CR) and a reference inductance connected thereto (LR).

Description

The present invention relates to a pressure measuring device with a capacitive pressure sensor with a base body and a pressure chamber arranged on the base body, in response to a pressure acting thereon deformable measuring membrane, a arranged on the measuring membrane membrane electrode and arranged on the base body Measuring capacitor comprising measuring capacitor having a dependent on the pressure-dependent deformation of the measuring membrane capacitance, and having a arranged on the measuring membrane membrane electrode and arranged on the base body reference electrode comprising reference capacitor.

Pressure measuring devices with capacitive pressure sensors are used in pressure measurement for the metrological detection of pressures.

In pressure measuring devices formed as a semiconductor chip capacitive micro-electro-mechanical pressure sensors can be used, as for example in the WO 03/106952 A2 are described.

The in the WO 03/106952 A2 Capacitive pressure sensors described comprise a base body and a measuring membrane arranged under the inclusion of a pressure chamber on the base body, as a function of a pressure to be measured acting thereon. The measuring diaphragm is made of silicon and has a conductive layer on its side facing the main body, which together with a rigid counterelectrode arranged on the main body forms a measuring capacitor whose capacitance changes as a function of a pressure-dependent deflection of the measuring diaphragm. The main body comprises an inductance which is connected to the conductive layer arranged on the measuring membrane and to the rigid counterelectrode. For this purpose, the base body is designed as a multi-layered substrate comprising insulated by insulating layers spiral tracks. Inductance and measuring capacitor form a resonant circuit whose dependent on the pressure to be measured resonance frequency can be determined wirelessly via an injected electromagnetic field.

However, capacitive microelectromechanical pressure sensors designed as semiconductor chips are not heat-resistant and therefore may only be exposed to a comparatively small temperature range. In addition, due to their mechanically very sensitive measuring diaphragm, they must not normally be exposed directly to a medium under the pressure to be measured. Instead, the pressure to be measured is fed to the measuring diaphragm via upstream pressure transmitters filled with a pressure-transmitting fluid.

• – einem temperaturabhängigen Messfehler des Drucksensors und
• – einem durch das temperaturabhängige Druckübertragungsverhalten des Druckmittlers bedingten Messfehler.

Accordingly, these measuring devices have a temperature-dependent measurement error, which is composed of

• - A temperature-dependent measurement error of the pressure sensor and
• - A conditional on the temperature-dependent pressure transmission behavior of the diaphragm seal measurement error.

These disadvantages can be at least partially avoided by using ceramic pressure sensors in which the measuring diaphragm and preferably also its basic body consist of ceramic. Ceramic pressure sensors are highly temperature resistant. In addition, due to the chemical and mechanical resistance of ceramics, they can be exposed directly to a medium under the pressure to be measured. For this purpose, they are regularly clamped in such a way in a housing, that the measuring membrane can be acted upon directly via an opening in the housing with a medium under the pressure to be measured.

Such a pressure measuring device with a by means of a force acting on an outer edge of the pressure sensor clamping device in a housing clamped ceramic pressure sensor is eg in the EP 0 995 979 A1 described. Ceramic pressure sensors are relatively insensitive to stresses acting on their outer edge in the axial direction, ie perpendicular to the plane of the measuring diaphragm. In contrast, however, can cause due to the different thermal expansion coefficients of the housing and sensor acting in the radial direction stresses on the pressure sensitivity of the measuring membrane, which in turn leads to a temperature-dependent measurement error. The will be in the in the EP 0 995 979 A1 counteracted described pressure measuring device by a preferably made of ceramic existing, clamped in the axial direction decoupling ring is provided on an outer edge of a remote from the diaphragm back of the body, which serves to avoid caused by thermo-mechanical stresses temperature-dependent hysteresis effects.

• – einen Grundkörper und eine unter Einschluss einer Druckkammer auf dem Grundkörper angeordnete, in Abhängigkeit von einem darauf einwirkenden zu messenden Druck verformbare Messmembran,
• – einen eine auf der Messmembran angeordnete Membranelektrode und eine auf dem Grundkörper angeordnete Messelektrode umfassenden Messkondensator, und
• – einen die Membranelektrode und eine auf dem Grundkörper angeordnete Referenzelektrode umfassenden Referenzkondensator.

In addition, a temperature-dependent measurement error of a capacitive ceramic pressure sensor on the in the DE 10 2009 027 742 A1 and the DE 10 2013 106 045 A1 be reduced way mentioned. This includes the pressure sensor

• A base body and a measuring diaphragm arranged on the base body, including a pressure chamber, which can be deformed as a function of a pressure to be measured on it,
• A measuring capacitor arranged on the measuring diaphragm and a measuring capacitor arranged on the base body, and
• A reference capacitor comprising the membrane electrode and a reference electrode arranged on the base body.

In this case, the two capacitors are preferably dimensioned such that the capacitance of the measuring capacitor is equal to the capacitance of the reference capacitor when the measuring diaphragm is in its rest position. Since the pressure-dependent deformation in the central region of the measuring diaphragm is greater in the edge region of the measuring diaphragm, the capacitance of the measuring capacitor depends to a much greater extent on the pressure to be measured than the capacitance of the reference capacitor. These pressure sensors measure the capacitances of the two capacitors and determine the pressure to be measured based on the two capacitances.

Ceramic pressure sensors with measuring and reference capacitors have the problem that due to the sensitivity of unamplified capacitance measuring signals, the capacitance measurements regularly require a suburb electronics preferably located in the immediate vicinity of the capacitors, which must be regularly connected to the capacitors via connections or connecting leads to be connected by soldering. The temperature range in which soldering effects reliable electrical and mechanical connections is dependent on the melting temperature of the solder used and thus regularly significantly lower than the temperature range in which capacitive ceramic pressure sensors could otherwise be used without difficulty.

It is an object of the invention to provide a pressure measuring device with a capacitive, ceramic pressure sensor, which can be used in a wide temperature range.

• – einem kapazitiven Drucksensor mit einem Grundkörper und einer unter Einschluss einer Druckkammer auf dem Grundkörper angeordneten, in Abhängigkeit von einem darauf einwirkenden zu messenden Druck verformbaren Messmembran, der
• – einen eine auf der Messmembran angeordnete Membranelektrode und eine auf dem Grundkörper angeordnete Messelektrode umfassenden Messkondensator mit einer von der druckabhängigen Verformung der Messmembran abhängigen Kapazität aufweist, und
• – einen eine auf der Messmembran angeordnete Membranelektrode und eine auf dem Grundkörper angeordnete Referenzelektrode umfassenden Referenzkondensator aufweist, der sich dadurch auszeichnet, dass
• – ein erster induktiv zu Schwingungen anregbarer elektrischer Schwingreis vorgesehen ist, der den Messkondensator und eine daran angeschlossene Sensorinduktivität umfasst, und
• – ein zweiter induktiv zu Schwingungen anregbarer elektrischer Schwingreis vorgesehen ist, der den Referenzkondensator und eine daran angeschlossene Referenzinduktivität umfasst.

For this purpose, the invention comprises a pressure measuring device, with

• - A capacitive pressure sensor having a base body and arranged with the inclusion of a pressure chamber on the base body, in response to a pressure acting thereon to be measured deformable measuring membrane, the
• - Has a arranged on the measuring membrane membrane electrode and arranged on the base body measuring electrode measuring capacitor having a dependent of the pressure-dependent deformation of the measuring membrane capacity, and
• - Has a arranged on the measuring diaphragm membrane electrode and arranged on the base body reference electrode comprehensive reference capacitor, which is characterized in that
• A first inductively oscillatable oscillating electrical oscillating circuit is provided, which comprises the measuring capacitor and a sensor inductance connected thereto, and
• - A second inductively to vibrations excitable electrical oscillating circuit is provided, which comprises the reference capacitor and a reference inductance connected thereto.

• – der erste Schwingkreis für sich alleine betrachtet eine von der Kapazität des Messkondensators und der Sensorinduktivität abhänge Resonanzfrequenz aufweist,
• – der zweite Schwingkreis für sich alleine betrachtet eine von der Kapazität des Referenzkondensators und der Referenzinduktivität abhänge Resonanzfrequenz aufweist, und
• – die Resonanzfrequenzen der beiden Schwingkreise verschieden sind.

A first development is characterized by the fact that

• The first oscillating circuit considered on its own has a resonant frequency which depends on the capacitance of the measuring capacitor and the sensor inductance,
• - The second resonant circuit considered by itself has one of the capacitance of the reference capacitor and the reference inductance dependent resonance frequency, and
• - The resonance frequencies of the two resonant circuits are different.

A preferred embodiment is characterized in that the capacitance of the measuring capacitor is substantially equal to the capacitance of the reference capacitor when the measuring diaphragm is in its initial position.

A second development is characterized in that the sensor inductance and the reference inductance have different inductances.

A third development is characterized in that the sensor inductance comprises a planar coil applied to a rear side of the main body facing away from the measuring diaphragm, in particular by physical deposition from the gas phase, in particular by sputtering.

• – die Referenzinduktivität eine auf eine von der Messmembran abgewandte Rückseite des Grundkörpers aufgebrachte, insb. durch physikalische Abscheidung aus der Gasphase, insb. durch Sputtern, aufgebrachte, Planarspule umfasst, oder
• – die Referenzinduktivität eine dreidimensionale Spule, insb. eine auf eine Mantelfläche eines auf der von der Messmembran abgewandten Rückseite des Grundkörpers angeordneten Isolators aufgebrachte, insb. durch physikalische Abscheidung aus der Gasphase, insb. durch Sputtern, aufgebrachte, dreidimensionale Spule, umfasst.

A fourth development is characterized by the fact that

• The reference inductance comprises a planar coil applied to a rear side of the main body remote from the measuring diaphragm, in particular by physical vapor deposition, in particular by sputtering, or
• - The reference inductance is a three-dimensional coil, esp. On a lateral surface of a facing away from the measuring membrane Rear side of the body arranged insulator applied, esp. By physical deposition from the gas phase, esp. By sputtering, applied, three-dimensional coil includes.

• – die Referenzinduktivität eine auf eine Mantelfläche eines auf der von der Messmembran abgewandten Rückseite des Grundkörpers angeordneten Isolators aufgebrachte, insb. durch physikalische Abscheidung aus der Gasphase, insb. durch Sputtern, aufgebrachte, dreidimensionale Spule umfasst, und
• – der Isolator mit einem Element, insb. einem Ferrit-Ring, aus einem Material mit hoher Permeabilität ausgestattet ist.

A fifth further education is characterized by the fact that

• The reference inductance comprises a three-dimensional coil applied to a lateral surface of an insulator arranged on the rear side of the main body facing away from the measuring diaphragm, in particular by physical vapor deposition, in particular by sputtering
• - The insulator is equipped with an element, esp. A ferrite ring, made of a material with high permeability.

• – die Referenzinduktivität eine auf eine Mantelfläche eines auf einem äußeren Rand der von der Messmembran abgewandte Rückseite des Grundkörpers angeordneten Isolators aufgebrachte dreidimensionale Spule umfasst, und
• – die dreidimensionale Spule über eine auf eine von der Messmembran abgewandte Rückseite des Grundkörpers aufgebrachte, insb. durch physikalische Abscheidung aus der Gasphase, insb. durch Sputtern, aufgebrachte, elektrisch leitfähige Beschichtung, die in elektrisch leitendem Kontakt zu einem durch den Grundkörper zur Referenzelektrode verlaufenden Kontaktstift steht, und eine auf eine dem Grundkörper zugewandte Stirnseite des Isolators aufgebrachte, insb. durch physikalische Abscheidung aus der Gasphase, insb. durch Sputtern, aufgebrachte elektrisch leitfähige Beschichtung in elektrisch leitendem Kontakt zur Referenzelektrode steht.

A sixth development is characterized by the fact that

• The reference inductance comprises a three-dimensional coil applied to a lateral surface of an insulator arranged on an outer edge of the rear side of the main body facing away from the measuring diaphragm, and
• The three-dimensional coil is applied via an electrically conductive coating which is applied to a rear side of the main body facing away from the measuring membrane, in particular by physical vapor deposition, in particular by sputtering, and which is in electrically conductive contact with one passing through the main body to the reference electrode Contact pin is, and on a the body facing the end face of the insulator applied, in particular by physical deposition from the gas phase, in particular by sputtering, applied electrically conductive coating is in electrically conductive contact with the reference electrode.

• – der Drucksensor mittels einer Einspannvorrichtung in einem Gehäuse eingespannt ist,
• – wobei die Einspannvorrichtung insb. derart ausgebildet ist, dass sie eine Einspannung, insb. eine elastische Einspannung, eines äußeren Randes des Drucksensors oder eines äußern Randes des Drucksensors und eines auf dessen von der Messmembran abgewandten Rückseite angeordneten Entkopplungsrings, insb. eines mit der Referenzinduktivität ausgestatten Isolators, bewirkt.

A further development of the pressure measuring device according to the invention or the pressure measuring device according to the last-mentioned further development provides that

• - The pressure sensor is clamped by means of a clamping device in a housing,
• - Wherein the clamping device esp. Is formed such that it a clamping, esp. An elastic clamping, an outer edge of the pressure sensor or an outer edge of the pressure sensor and arranged on the side facing away from the measuring membrane rear decoupling ring, esp. With the reference inductance equipped insulator causes.

• – die Membranelektroden von Messkondensator und Referenzkondensator voneinander getrennte Elektroden sind, oder
• – die Membranelektroden von Messkondensator und Referenzkondensator durch eine beiden Kondensatoren gemeinsame Membranelektrode gebildet sind.

A seventh development is characterized by the fact that

• - The membrane electrodes of measuring capacitor and reference capacitor are separate electrodes, or
• - The membrane electrodes of measuring capacitor and reference capacitor are formed by a common membrane electrode capacitors.

An eighth development is characterized in that an inductively coupled to the resonant circuits measuring unit is provided which is designed such that it oscillates the oscillations inductively and via an inductive coupling to the first resonant circuit of the capacitance of the measuring capacitor and an inductive coupling to second resonant circuit of the capacitance of the reference capacitor dependent measured quantities determined, on the basis of which it determines the capacities of measuring capacitor and reference capacitor.

• – von denen eine eine induktiv an die Sensorinduktivität gekoppelte Messinduktivität, insb. eine auf einer der von der Messmembran abgewandten Rückseite des Grundkörpers zugewandten Stirnseite eines Trägers aus einem Isolator aufgebrachte Planarspule, umfasst,
• – von denen die andere eine induktiv an die Referenzinduktivität gekoppelte Messinduktivität, insb. eine auf einer der von der Messmembran abgewandten Rückseite des Grundkörpers zugewandten Stirnseite eines Trägers aus einem Isolator aufgebrachte Planarspule, umfasst,
• – die jeweils eine Erregereinrichtung umfassen, die eine Wechselspannung mit zeitlich veränderlicher Frequenz erzeugt, die an einem ersten Anschluss der Messinduktivität der jeweiligen Messeinrichtung anliegt, und
• – die jeweils eine an die Messinduktivität der jeweiligen Messeinrichtung angeschlossene Messelektronik umfassen, die anhand des dabei über die jeweilige Messinduktivität fließenden Messsignals mindestens eine von der Kapazität des Messkondensators und/oder der Kapazität des Referenzkondensators abhängige Messgröße bestimmt.

A ninth further development is characterized in that a measuring unit is provided which comprises two measuring devices,

• One of which comprises a measuring inductance inductively coupled to the sensor inductance, in particular a planar coil applied to an end face of a carrier facing away from the measuring membrane from the rear side of the base body, from an insulator,
• Of which the other comprises a measuring inductance inductively coupled to the reference inductance, in particular a planar coil applied to an end face of a carrier facing away from the measuring membrane from the rear side of the base body, comprising an insulator,
• - Each comprising an excitation device which generates an alternating voltage with time-varying frequency, which is applied to a first terminal of the measuring inductance of the respective measuring device, and
• - Which each comprise a connected to the measuring inductance of the respective measuring device measuring electronics, which determines at least one of the capacitance of the measuring capacitor and / or the capacitance of the reference capacitor dependent on the basis of the respective measuring inductance flowing measurement signal.

• – die Schwingkreise im Wesentlichen entkoppelte Schwingkreise sind,
• – die Messelektronik der die induktiv an die Sensorinduktivität gekoppelte Messinduktivität umfassenden Messeinrichtung derart ausgebildet ist, dass sie eine von der Kapazität des Messkondensators abhängige Frequenz bestimmt, bei der eine Gesamtimpedanz einer durch diese Messinduktivität und den daran gekoppelten den Messkondensator umfassenden Schwingkreis gebildeten Einheit ein Maximum aufweist, und
• – die Messelektronik der die induktiv an die Referenzinduktivität gekoppelte Messinduktivität umfassenden Messeinrichtung derart ausgebildet ist, dass sie eine von der Kapazität des Referenzkondensators abhängige Frequenz bestimmt, bei der die Gesamtimpedanz eines durch diese Messinduktivität und den daran gekoppelten den Referenzkondensator umfassenden Schwingkreis gebildeten Einheit ein Maximum aufweist.

A development of the latter training is characterized by the fact that

• The resonant circuits are essentially decoupled resonant circuits,
• - The measuring electronics of the inductively coupled to the sensor inductance measuring inductance comprehensive measuring device is designed such that it determines a dependent of the capacitance of the measuring capacitor frequency at which a total impedance of a through this Measuring inductance and the coupled thereto the measuring capacitor comprehensive resonant circuit formed unit has a maximum, and
• - The measuring electronics of the inductively coupled to the reference inductance measuring inductance comprising measuring device is designed such that it determines a dependent of the capacitance of the reference capacitor frequency at which the total impedance of a unit formed by this measuring inductance and the reference capacitor comprising the resonant circuit comprising a maximum ,

• – die Schwingkreise induktiv und/oder kapazitiv gekoppelte Schwingkreise sind,
• – eine Messeinrichtung vorgesehen ist,
• – die eine induktiv an die Sensorinduktivität gekoppelte Messinduktivität, eine induktiv an die Referenzinduktivität gekoppelte Messinduktivität oder eine sowohl induktiv an die Sensorinduktivität gekoppelte als auch induktiv an die Referenzinduktivität gekoppelte Messinduktivität, insb. eine dreidimensionale Messspule, insb. eine Luftspule, oder zwei in Serie geschaltete Messspulen, insb. zwei über eine Leitung verbundene auf einer von der Messmembran abgewandten Rückseite des Grundkörpers zugewandten Stirnseite eines Trägers aus einem Isolator aufgebrachte Planarspulen, umfasst,
• – die eine Erregereinrichtung umfasst, die eine Wechselspannung mit zeitlich veränderlicher Frequenz erzeugt, die an einem ersten Anschluss der Messinduktivität anliegt, und
• – die eine an die Messinduktivität angeschlossene Messelektronik umfasst, die derart ausgebildet ist, dass sie
• – zwei verschiedene, auf unterschiedliche Weise von der Kapazität des Messkondensators und der Kapazität des Referenzkondensators abhängige Frequenzen bestimmt, bei denen eine Gesamtimpedanz einer durch die Messinduktivität und die beiden daran gekoppelten Schwingkreise gebildete Einheit jeweils ein Maximum aufweist, und
• – anhand der beiden Frequenzen die Kapazität des Messkondensator und die Kapazität des Referenzkondensators bestimmt.

A development of the first development is characterized by the fact that

• - the resonant circuits are inductively and / or capacitively coupled resonant circuits,
• A measuring device is provided,
• - The one inductively coupled to the sensor inductance measuring inductance, a inductively coupled to the reference inductance or a both inductively coupled to the sensor inductance and inductively coupled to the reference inductance measuring inductance, esp., A three-dimensional measuring coil, especially an air coil, or two connected in series Measuring coils, in particular two planar coils connected to a front side of a carrier, which are connected via a line and facing away from the measuring diaphragm on the rear side of the carrier, comprises a planar coil,
• - Which comprises an excitation device which generates an alternating voltage with time-varying frequency, which is applied to a first terminal of the measuring inductance, and
• - Which comprises a connected to the measuring inductance measuring electronics, which is designed such that they
• - determines two different, dependent in different ways on the capacitance of the measuring capacitor and the capacitance of the reference capacitor frequencies in which a total impedance of a unit formed by the measuring inductance and the two resonant circuits coupled thereto each has a maximum, and
• - Determines the capacitance of the measuring capacitor and the capacitance of the reference capacitor based on the two frequencies.

A further development is characterized in that the measuring device is part of a measuring module which can be fastened by means of a releasable mechanical fastening device to a location located on the side of the pressure sensor remote from the measuring diaphragm.

• – Messkondensator und Referenzkondensator eine beiden Kondensatoren gemeinsame Membranelektrode umfassen, und
• – eine räumlich zwischen Messelektrode und Referenzelektrode angeordnete Trennelektrode vorgesehen ist, die elektrisch auf dem Potential der Membranelektrode liegt.

Another development is characterized in that

• - Measurement capacitor and reference capacitor comprise a membrane electrode common to both capacitors, and
• - Is provided a spatially arranged between the measuring electrode and the reference electrode separation electrode, which is electrically at the potential of the membrane electrode.

The invention offers the advantage that the two capacitances can be determined by means of a measuring unit inductively coupled to the resonant circuits. Inductive couplings are wireless. Accordingly, no soldering requiring, line-bound connections of the capacitors to the measuring unit are required to measure the capacitances. The pressure measuring devices can thus be used in a much wider temperature range.

In addition, due to the inductive measurement variable detection, the invention offers the advantage that the measuring unit can be exchanged if necessary without the pressure sensor having to be released from its clamping for this purpose. Since the clamping conditions of the pressure sensor do not change when the measuring unit is replaced, the pressure measuring device can be put back into service after an exchange, without recalibration being required to determine the dependency of the pressure to be measured on the two capacitors.

The invention and its advantages will now be explained in more detail with reference to the figures of the drawing, in which two embodiments are shown. Identical elements are provided in the figures with the same reference numerals.

1 shows: a pressure measuring device with a pressure sensor with two planar coils;

2 Fig. 1 shows a pressure measuring device having a pressure sensor with a planar coil and an insulator equipped with a three-dimensional coil;

3 shows a plan view of a side facing away from the measuring membrane back of the pressure sensor of 1 ;

4 shows a plan view of a side facing away from the measuring membrane back of the pressure sensor of 2 ;

5 shows: an electrical equivalent circuit of the pressure measuring device of 1 ;

6 shows: an electrical equivalent circuit of the pressure measuring device of 2 ;

7 shows: a pressure sensor equipped with a separation electrode;

8th shows: one of the diaphragm facing the front side of the main body of the pressure sensor of 7 ; and

9 shows: an inner side facing the base of the measuring diaphragm of the pressure sensor of 7 ,

In order to represent components of very different sizes, a representation not to scale was selected in all figures.

1 and 2 each show an embodiment of a pressure measuring device according to the invention. The pressure measuring devices each comprise a capacitive pressure sensor 1 with a basic body 3 and one including a pressure chamber 5 on the body 3 arranged measuring diaphragm 7 , The pressure sensors 1 are preferably ceramic pressure sensors whose measuring membrane 7 made of a ceramic, for example made of aluminum oxide (Al ₂ O ₃ ). Preferably, the basic body also exist 3 made of ceramic, eg of aluminum oxide (Al ₂ O ₃ ). The measuring membranes 7 the pressure sensors 1 be applied in measuring operation with a pressure to be measured p, a dependent of the pressure to be measured p deformation of the respective measuring diaphragm 7 causes.

The pressure sensors 1 can, as shown here, be designed as absolute pressure sensors. In that case it is under the measuring membrane 7 enclosed pressure chamber 5 evacuated. Alternatively, they may be designed as relative or differential pressure sensors by the pressure chamber 5 about one through the main body 7 passing through - not shown here - pressure supply a reference pressure p _ref , for example, an ambient pressure, or a second pressure is supplied.

The pressure sensors 1 are for example by means of a clamping device in a housing 9 clamped, that an opening 11 has, over an outer side of the measuring diaphragm 7 with the pressure to be measured p is acted upon. The clamping device is preferably designed such that it has an elastic clamping of an outer edge of the pressure sensor 1 causes. As a clamping device, for example, is an opening 11 outside surrounding shoulder 13 of the housing 9 , on which an outer edge of the measuring membrane 7 with the interposition of a seal 15 rests and one in the housing 9 inserted pressure ring 17 that the pressure sensor 1 against the shoulder 13 suppressed. Alternatively, the pressure sensors 1 Of course, pressure measuring devices according to the invention are also mounted in a manner other than by means of the clamping device described here at a place of use and subjected to a pressure p to be measured.

The pressure sensors 1 each comprise a measuring capacitor C _p and a reference capacitor C _R. The measuring capacitor C _p includes one on the measuring diaphragm 7 arranged membrane electrode 19 . 19a and one on the measuring membrane 7 facing end face of the body 3 arranged measuring electrode 21 , The reference capacitor C _R comprises one on the measuring diaphragm 7 arranged membrane electrode 19 . 19b and one on the measuring membrane 7 facing end face of the body 3 arranged reference electrode 23 ,

The measuring electrode 21 is preferably dimensioned such that it is one of the middle of the measuring diaphragm 7 opposite region of the inside of the body 3 covered. For this purpose, it may for example be circular disk-shaped. The reference electrode 23 is preferably dimensioned such that it forms an outer edge of the measuring diaphragm 7 opposite region of the inside of the body 3 covered and from the measuring electrode 21 is spaced. For this purpose, it may be formed, for example, as an annular disc-shaped electrode, which is the measuring electrode 21 outside on all sides.

The membrane electrodes 19a . 19b of measuring capacitor C _p and reference capacitor C _R may be formed as two separate electrodes. In that case, the membrane electrode 19a of the measuring capacitor C _{p is} preferably the same shape as the measuring electrode opposite it 21 and the membrane electrode 19b of the reference capacitor C _R preferably has the same shape as the reference electrode opposite it 23 , This embodiment is in 1 shown.

Alternatively, a single, two capacitors may be common membrane electrode 19 be provided, the one to the pressure chamber 5 adjacent area of the inside of the measuring diaphragm 7 completely covered. This variant is in 2 shown.

Pressure-measuring devices according to the invention are characterized in that they comprise a first and a second oscillating electrical circuit which can be inductively excited to oscillate. The first resonant circuit comprises the measuring capacitor C _P and a sensor inductance L _P connected thereto. The second resonant circuit comprises the reference capacitor C _R and a reference inductance L _R connected thereto.

The sensor inductance L _P and / or the reference inductance L _R can each have one on one from the measuring membrane 7 opposite back of the body 3 applied planar coil 25 . 27 include. At the in 1 illustrated embodiment are both inductors as planar coils 25 . 27 educated. 3 shows a plan view of the back of the body 3 , In this variant, the sensor inductance L _{P is} preferably on a central region of the rear side of the main body 3 provided and on the outside of the on an outer edge of the back of the body 3 provided, the sensor inductance L _R forming planar coil 27 spaced.

The planar coils 25 . 27 are preferably electrically conductive coatings, such as by physical vapor deposition, esp. By sputtering, on the back of the body 3 applied coatings. The electrical connection of the planar coils 25 . 27 is preferably carried out via an electrically conductive, through the body 3 through to the measuring electrode 21 or to the reference electrode 23 extending contact pin 29 . 31 , In this case, for the preparation of the electrodes of the two capacitors and the two planar coils 25 . 27 the same materials and the same coating methods are used. Coatings applied by physical vapor deposition offer the advantage that they provide a highly temperature-resistant, electrically conductive connection to the contact pins when applied 29 . 31 received.

At the in 2 illustrated embodiment, the sensor inductance L _P comprises one of the measuring diaphragm 7 opposite back of the body 3 applied planar coil 25 and the reference inductance L _R comprises a three-dimensional coil 33 , In this variant, the three-dimensional coil 33 Preferably, a longitudinal axis which is perpendicular to the plane of the sensor inductance L _R forming planar coil 25 runs. In this variant too, the sensor inductance L _{P is} preferably on a central region of the rear side of the main body 3 intended. 4 shows a plan view of the back of the body 3 of the pressure sensor 1 from 2 , In contrast, the three-dimensional coil forming the reference inductance L _{R is} 33 preferably on an outer circumferential surface of a on the back of the body 3 arranged insulator 35 intended. In this case, the connection of the three-dimensional coil 33 preferably via one on the back of the body 3 applied electrically conductive coating 37 in electrically conductive contact with that through the body 3 to the reference electrode 23 extending contact pin 31 stands, and one on the body 3 facing end face of the insulator 35 applied coating 37 ' , Again, there are the three-dimensional coil 33 and the coatings 37 . 37 ' preferably from the material of the electrodes of the capacitors and are preferably applied by physical vapor deposition.

The insulator 35 is preferably at the same time as a decoupling ring to protect the measuring diaphragm 7 used in front of it in the radial direction acting on mechanical stresses. In that case the insulator is 35 preferably as on an outer edge of the body 3 arranged ring formed by means of the clamping device in the axial, ie parallel to the surface normal to the measuring diaphragm 7 extending direction, against the outer edge of the back of the body 3 is curious. It can be through the insulator 35 caused reduction of acting in the radial direction thermo-mechanical stresses additionally by a between the insulator 35 and the pressure ring 17 arranged foil 39 , For example, a flat gasket of polytetrafluoroethylene (PTFE) can be increased.

In its function as a decoupling ring is the insulator 35 preferably formed as a separate component, which on the outer edge of the body 3 rests. In this case, the electrically conductive connection between the reference inductance L _R and the reference capacitor C _R via the from the clamping device on the superimposed coatings 37 . 37 ' ensured clamping pressure ensured.

The decoupling ring is preferably made of the material of the main body 3 and of course - in the case without a three-dimensional coil 33 - also in the 1 embodiment shown are used.

The sensor inductance L _P and the reference inductance L _R each have a substantially constant inductance. Accordingly, the first resonant circuit, considered individually, has a resonant frequency ω _res (C _P , L _P ) which depends on the capacitance of the measuring capacitor C _P and the sensor inductance L _P. Likewise, the second resonant circuit, taken in isolation, has a resonance frequency ω _res (C _R , L _P ) which depends on the capacitance of the reference capacitor C _R and the reference inductance L _R. The vibration characteristics of the two resonant circuits are thus determined largely by the respective capacity contained therein.

If this is desired in view of the vibration characteristics of the resonant circuits, the insulator 35 with an element 41 be made of a material with high magnetic permeability. The element 41 causes a reduction in the resonant frequency of the associated resonant circuit. In addition, it can be used specifically to set a frequency spacing between to increase the resonance frequencies of the two resonant circuits. As an element 41 Is particularly suitable for one in the insulator 35 inserted ferrite ring.

Pressure measuring devices according to the invention have the advantage that the capacitances of measuring capacitor C _p and reference capacitor C _{R can be determined} by means of a measuring unit inductively coupled to the oscillating circuits. The measuring unit is preferably designed such that it inductively oscillates the resonant circuits and determines an inductive coupling to the first resonant circuit of the capacitance of the measuring capacitor C _p and via an inductive coupling to the second resonant circuit of the capacitance of the reference capacitor C _R dependent variables based which then determines the capacitances of measuring capacitor C _p and reference capacitor C _R.

In contrast to conventional pressure measuring devices with ceramic pressure sensors, no soldering to the measuring electrode is required 21 and the reference electrode 23 required to be connected. Accordingly, pressure measuring devices according to the invention can be used in a significantly larger temperature range.

If the two oscillating circuits are sufficiently decoupled from each other, they can be considered as separate oscillating circuits. In that case, the measuring unit can be a separate measuring device for each resonant circuit 43 of which one near the sensor inductance L _P and the other one arranged in the vicinity of the reference inductance L _R measuring inductance L _S1 , L _S2 . In this case, the distance between the sensor inductance L _P and the one measuring inductance L _{S1 is} dimensioned such that an inductive coupling exists between these two inductances. Analogously, the distance between the reference inductance L _R and the other measuring inductance L _{S2 is} dimensioned such that an inductive coupling also exists between these two inductances. 5 shows an embodiment of one with two measuring devices 43 equipped measuring unit together with an equivalent circuit diagram of the respective measuring inductance L _S1 , L _S2 to the respective measuring device 43 coupled resonant circuits of in 1 illustrated pressure sensor 1 ,

In this case, the measuring inductances L _S1 , L _{S2 can be used,} for example, as planar coils 49 . 51 be formed on one of the back of the main body 3 facing end face of a in the housing 9 used carrier 53 are applied from an insulator. In that case, the planar coils have 49 . 51 Preferably, a shape and an arrangement that in 3 illustrated shaping and arrangement of sensor inductance 25 and reference inductance 27 equivalent.

Planar coils have the advantage that the surrounding electromagnetic field is spatially relatively limited. Accordingly, the formation of the measuring inductances L _S1 , L _S2 , the sensor inductance L _P and the reference inductance L _R as planar coils 25 . 27 . 49 and 51 a caused via the coils inductive coupling of the resonant circuits with each other largely avoided.

For measuring the two capacities, for example, measuring devices 43 are used, each having an exciter device 45 comprise, which generates an alternating voltage with time-varying frequency, which is applied via a series resistor R to a first terminal of the associated measuring inductance L _S1 , L _S2 . As an AC voltage source is, for example, a controlled via a sawtooth voltage controlled oscillator. In addition, the measuring facilities include 43 in each case one of the measuring inductance L _S1 and L _S2 connected measuring electronics 47 , which determines, based on the measuring signal flowing through its measuring inductance L _S1 or L _S2 , a measured variable dependent on the capacitance of the resonant circuit coupled to its measuring inductance L _S1 or L _S2 .

Such a measured variable is, for example, the frequency at which the total impedance Z ¹ _ges (ω), Z ² _ges (ω) of the unit formed by the respective measuring inductance L _S1 or L _S2 and the resonant circuit directly coupled thereto is one of the capacitance to be measured of the directly coupled thereto resonant circuit has dependent maximum. The total impedance Z ¹ _ges (ω), Z ² _ges (ω), for example, based on the voltage drop U (Z ¹ _ges (ω)), U (Z ² _ges (ω)) of the respective measuring inductance L _S1 and L _S2 flowing measuring signal can be determined.

In conventional pressure measuring devices with capacitive ceramic pressure sensors, the measurement accuracy depends crucially on measuring the very small, typically in the range of Femtofarad lying capacities of measuring and reference capacitor C _p , C _R as accurately as possible. In contrast, in the pressure measuring devices according to the invention via the inductive coupling, a transformation into the frequency space takes place, which makes it possible to measure frequency changes instead of very small capacitances.

If there is an inductive and / or capacitive coupling between the two resonant circuits, then the capacitances of measuring capacitor C _P and reference capacitor C _R can no longer be read out independently of each other. A capacitive coupling is in the case of 2 shown Embodiment over the measurement capacitor C _P and the reference capacitor C _R common membrane electrode 19 given. In addition, depending on the configuration of the sensor inductance L _P and the reference inductance L _{R, there may} additionally also be an inductive coupling between the two oscillating circuits.

If the resonant circuits are coupled resonant circuits, they are designed according to the invention such that the first resonant circuit, considered individually, has a resonant frequency ω _res (C _P , L _P ) which depends on the capacitance of the measuring capacitor C _P and the sensor inductance L _P , the second resonant circuit considered by itself has a resonant frequency ω _res dependent on the capacitance of the reference capacitor C _R and the reference inductance L _R (C _R , L _P ), and the resonance frequencies ω _res (C _P , L _P ), ω _res (C _R , L _P ) of the two resonant circuits are different. For this purpose, the resonant circuits are preferably designed such that the product of the capacitance of the measuring capacitor C _P and the inductance of the sensor inductance L _P is different from the product of the capacitance of the reference capacitor C _R and the inductance of the reference inductance L _R.

It is achieved via the various resonance frequencies ω _res (C _P , L _P ), ω _res (C _R , L _P ) of the oscillating circuits that the total impedance Z _ges (ω) of a unit formed by a measuring inductance and the two oscillating circuits coupled thereto is two maxima which occur at different frequencies ω _res1 , ω _res2 . By way of the two frequencies ω _res1 , ω _res2 , two variables which are dependent on the capacitance of the measuring capacitor C _P and the capacitance of the reference capacitor C _R are thus available, by means of which the two capacitances can then be determined. For this purpose, the dependencies of the frequencies ω _res1 , ω _res2 of the two capacitances are preferably determined in advance in a calibration method and deposited, for example in the form of characteristic curves or the like, in the measuring unit.

To determine the frequencies ω _res1 , ω _res2 , for example, the in 5 illustrated measuring unit can be used. In this case, the two frequencies ω _res1 , ω _res2, on the basis of which the capacitance of the measuring capacitor C _P and the capacitance of the reference capacitor C _{R are} determined, can be determined with each of the two measuring electronics 47 be determined. However, it should be _noted that the dependencies of the frequencies ω _res1 , ω _res2 of the two capacitances due to the different measuring inductances L _S1 , L _{S2 of} the two measuring devices 43 can be different.

Alternatively, a measuring unit can be used, only one of the two in 5 shown measuring devices 43 comprises, whose measuring inductance L _S1 or L _{S2 is} coupled via the adjacent thereto sensor inductance L _P and the adjacent reference inductance L _R directly to this comprehensive resonant circuit and indirectly to the respective other resonant circuit.

Preferably, however, a measuring unit is used, the only one of in 5 shown measuring devices 43 comprises, whose measuring inductance L _{S is} formed and arranged such that there is a direct inductive coupling to the sensor inductance L _P and the reference inductance L _{R over them} . This variant is in 6 represented the measuring device 43 together with an equivalent circuit diagram of the measuring inductance L _S to the measuring device 43 coupled resonant circuits of in 2 shown pressure measuring device shows. In this variant, the measuring inductance L _{S is} preferably designed such that it comprises an inductance region arranged at a short distance from the sensor inductance L _P and an inductance region arranged at a short distance from the reference inductance L _R. The distances are again to be dimensioned such that there is an inductive coupling of the measuring inductance L _S to the sensor inductance L _P and to the reference inductance L _R. For this purpose, the measuring inductance L _S may include two measuring coils connected in series, each of which forms one of the two inductance ranges. As measuring coils are, for example, already on the basis of 1 and 3 Planar coils described 49 . 51 which in this case has an in 3 shown in dashed lines, on the front side of the carrier 53 applied wire 55 connected in series.

Alternatively, the measuring inductance L _S as a three-dimensional measuring coil 57 , For example, be designed as a spiral-shaped air coil. This variant is in 2 shown schematically. In that case the measuring coil is 57 preferably at a small distance to the back of the body 3 arranged and has a parallel to the back extending length, which is dimensioned such that their opposite ends in each case at a small distance to the reference inductance L _R- bearing insulator 35 are located. The distances are again to be dimensioned such that an inductive coupling of the measuring coil 57 to the sensor inductance L _P and to the reference inductance L _R.

Analogously, of course, the here by reference to the embodiments of 1 and 5 described pressure measuring devices with decoupled resonant circuits on the basis of the embodiments of 2 and 6 be described manner such that they have taken separately different resonant frequencies ω _res (C _P , L _P ), ω _res (C _R , L _R ). This increases the degree of decoupling of the two Resonant circuits. In addition, this measure makes it possible to carry out the determination of the capacitance of the measuring capacitor C _P in a frequency range which is different from the frequency range used to determine the capacitance of the reference capacitor C _R. Again, a further decoupling of the two resonant circuits is achieved during the measurement. Here, too, arises a frequency difference between the frequencies at which the total impedances, which have the capacity of the respective capacitor C _P , C _R dependent maxima. This frequency interval makes it possible to use these two frequencies to correct a measurement error caused by a residual coupling between the two oscillating circuits.

The different resonance frequencies ω _res (C _P , L _P ), ω _res (C _R , L _R ) of the resonant circuits of pressure measuring devices according to the invention are preferably achieved in that the sensor inductance L _P and the reference inductance L _{R have} different inductances.

In the case of pressure measuring devices according to the invention, it is advantageous, in particular, with respect to common-mode suppression of interfering signals affecting both capacitances, if the capacitance of the measuring capacitor C _{p is} dimensioned such that it is substantially equal to the capacitance of the reference capacitor C _R when the measuring membrane 7 is in their starting position.

Finally, the pressure to be measured p is determined based on the capacitances of measuring capacitor C _p and reference capacitor C _R. This is preferably done by means of sensor characteristic data determined in a calibration method, which reproduce the dependencies of the pressure p to be measured on the capacitances of measuring capacitor C _p and reference capacitor C _R.

In this case, the pressure determination can be carried out, for example, by means of a differential change g of the two capacitances C _p , C _R , for example based on the ratio of the difference C _p - C _{R of} the two capacitances to the measuring capacitance C _p according to: g = (C _p - C _R ) / C _{p is} determined. The differential change g has a highly linear dependence on the pressure p to be measured. At the same time, this form of pressure determination achieves a high-quality common-mode suppression of interference signals that equally affect both capacitances, as well as a compensation of temperature-dependent capacitance changes.

The measuring unit of the pressure measuring device according to the invention is preferably formed as part of a measuring module, which by means of a detachable, in 1 and 2 only schematically illustrated, mechanical fastening device on a on the of the measuring diaphragm 7 away side of the pressure sensor located place can be mounted. For this purpose, the measuring modules can, for example, with a radially outwardly ersteckenden paragraph 59 equipped by means of a pressure ring 61 on one in the housing 9 provided stop 63 is mounted. It is about the stop 63 a defined, reproducible positioning of the measuring inductance L _S and the measuring inductances L _S1 , L _S2 guaranteed.

Trained as measuring module measuring units offer the advantage that they can be replaced if necessary, without the pressure sensor 1 must be released from the jig. Since the clamping conditions of the pressure sensor do not change when the measuring unit is replaced, the pressure measuring device can be put back into service after an exchange, without recalibration being required to determine the dependency of the pressure to be measured on the two capacitors.

Optionally, the measuring characteristics of pressure measuring devices according to the invention can be combined with a membrane electrode common to the measuring capacitor C _p and the reference capacitor C _R 19b capacitively coupled resonant circuits can be improved by measures that cause a reduction of the coupling. One such optional measure is that between the measuring electrode 21 and the reference electrode 23 existing direct capacitive coupling by a spatially arranged between these two electrodes, at the potential of the membrane electrode 19 lying separation electrode 65 to reduce. 7 shows an embodiment of an appropriately designed pressure sensor. 8th shows a view of the measuring membrane 7 facing end face of the body 3 of the pressure sensor of 7 and 9 a view of the main body 3 facing inside of the measuring diaphragm 7 ,

The separation electrode 65 preferably has an electrode surface forming a closed ring, which is the measuring electrode spaced therefrom 21 outside on all sides. The electrical connection of the separation electrode 65 to the potential of the membrane electrode 21 preferably takes place via a pressure chamber 5 outside on all sides surrounding, an outer edge 67 of the basic body 3 with an outer edge 69 the measuring membrane 7 connecting, electrically conductive joining 71 , For ceramic pressure sensors, the addition is 71 preferably an active brazing, esp. A executed by means of a Zr-Ni alloy and titanium having ternary active brazing Aktivhartlötung. Corresponding active hard soldering are eg in the EP 0 490 807 A2 described.

For this purpose, the reference electrode 23 Preferably, an electrode surface forming an almost completely closed ring, the electrode electrode spaced therefrom 65 surrounds the outside. The through the reference electrode 23 formed ring is in a ring segment area 73 interrupted. This interruption allows the separation electrode 65 over an adjacent, through the ring segment area 73 extending electrode extension 75 with the opportunity 71 connect to. This is how the separation electrode stands 65 over the electrode extension 75 and the coincidence 71 in electrically conductive contact with the membrane side of the joint 71 adjacent membrane electrode 19 ,

When using this pressure sensor in a pressure measuring device according to the invention is of course also here in 7 not shown, connected to the measuring capacitance C _P sensor inductance L _p and provided to the reference capacitance C _R reference inductance L _R provide, for example, based on the 1 or the basis of 2 described manner can be done.

LIST OF REFERENCE NUMBERS

1

 pressure sensor

3

 body

5

 pressure chamber

7

 measuring membrane

9

 casing

11

 opening

13

 shoulder

15

 poetry

17

 pressure ring

19

 membrane electrode

21

 measuring electrode

23

 reference electrode

25

 sensor inductance

27

 reference inductance

29

 pin

31

 pin

33

 three-dimensional coil

35

 insulator

37

 coating

39

 foil

41

 element

43

 measuring device

45

 excitation device

47

 measuring electronics

49

 planar coil

51

 planar coil

53

 carrier

55

 management

57

 three-dimensional measuring coil

59

 paragraph

61

 pressure ring

63

 attack

65

 separating electrode

67

 Edge of the main body

69

 Edge of the measuring membrane

71

 coincidence

73

 Ring segment region

75

 Electrode extension

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• WO 03/106952 A2 [0003, 0004]
• EP 0995979 A1 [0008, 0008]
• DE 102009027742 A1 [0009]
• DE 102013106045 A1 [0009]
• EP 0490807 A2 [0081]

Claims (16)

Pressure measuring device, with - a capacitive pressure sensor ( 1 ) with a basic body ( 3 ) and one including a pressure chamber ( 5 ) on the base body ( 3 ), in response to a pressure (p) thereon deformable measuring membrane ( 7 ), the one on the measuring membrane ( 7 ) arranged membrane electrode ( 19 . 19a ) and one on the main body ( 3 ) arranged measuring electrode ( 21 ) measuring condenser (C _P ) with one of the pressure-dependent deformation of the measuring diaphragm ( 7 ) has dependent capacity, and - one on the measuring membrane ( 7 ) arranged membrane electrode ( 19 . 19b ) and one on the main body ( 3 ) arranged reference electrode ( 23 ) reference capacitor (C _R ), characterized in that - a first inductively oscillatable excitable electrical oscillating circuit is provided which comprises the measuring capacitor (C _P ) and a sensor inductance connected thereto (L _P ), and - a second inductively to oscillations stimitable electrical oscillating circuit is provided which comprises the reference capacitor (C _R ) and a reference inductance (L _R ) connected thereto. Pressure measuring device according to claim 1, characterized in that - the first resonant circuit considered by itself has one of the capacitance of the measuring capacitor (C _P ) and the sensor inductance (L _P ) dependent resonance frequency (ω _res (C _P , L _P ), - second resonant circuit considered by itself has one of the capacitance of the reference capacitor (C _R ) and the reference inductance (L _R ) dependent resonance frequency (ω _res (C _R , L _R ), and - the resonance frequencies (ω _res (C _P , L _P ), ω _res (C _R , L _R )) of the two resonant circuits are different. Pressure measuring device according to claim 1, characterized in that the capacitance of the measuring capacitor (C _p ) is substantially equal to the capacitance of the reference capacitor (C _R ) when the measuring diaphragm (C 7 ) is in its starting position. Pressure measuring device according to claim 1, characterized in that the sensor inductance (L _P ) and the reference inductance (L _R ) have different inductances. Pressure measuring device according to claim 1, characterized in that the sensor inductance (L _p ) one on one of the measuring membrane ( 7 ) facing away back of the body ( 3 ) applied, in particular by physical deposition from the gas phase, in particular by sputtering, applied, planar coil ( 25 ). Pressure measuring device according to claim 1, characterized in that - the reference inductance (L _R ) on one of the measuring membrane ( 7 ) facing away back of the body ( 3 ) applied, in particular by physical deposition from the gas phase, in particular by sputtering, applied, planar coil ( 27 ), or - the reference inductance (L _R ) is a three-dimensional coil ( 33 ), in particular one on a lateral surface of a on the of the measuring membrane ( 7 ) facing away from the back of the body ( 3 ) insulator ( 35 ) applied, in particular by physical deposition from the gas phase, in particular by sputtering, applied, three-dimensional coil ( 33 ). Pressure measuring device according to claim 1, characterized in that - the reference inductance (L _R ) a on a lateral surface of a on the of the measuring membrane ( 7 ) facing away from the back of the body ( 3 ) insulator ( 35 ) applied, in particular by physical deposition from the gas phase, in particular by sputtering, applied, three-dimensional coil ( 33 ), and - the insulator ( 35 ) with an element ( 41 ), esp. A ferrite ring, is made of a material with high permeability. Pressure measuring device according to claim 1, characterized in that - the reference inductance (L _R ) a on a lateral surface of an outer edge of the of the measuring membrane ( 7 ) facing away back of the body ( 3 ) insulator ( 35 ) applied three-dimensional coil ( 33 ), and - the three-dimensional coil ( 33 ) on one of the measuring membrane ( 7 ) facing away back of the body ( 3 ), in particular by physical deposition from the gas phase, in particular by sputtering, applied, electrically conductive coating ( 37 ) in electrically conductive contact with one through the main body ( 3 ) to the reference electrode ( 23 ) extending contact pin ( 31 ), and one on the body ( 3 ) facing end side of the insulator ( 35 ), in particular by physical deposition from the gas phase, in particular by sputtering, applied electrically conductive coating ( 37 ' ) in electrically conductive contact with the reference electrode ( 23 ) stands. Pressure measuring device according to claim 1 or 8, characterized in that - the pressure sensor ( 1 ) by means of a clamping device in a housing ( 9 ) is clamped -, wherein the clamping device esp. Is formed such that it is a clamping, esp. an elastic clamping, an outer edge of the pressure sensor ( 1 ) or an outer edge of the pressure sensor ( 1 ) and one of which from the measuring membrane ( 7 ) facing away from the rear decoupling ring, esp. Of the reference inductance (L _R ) equipped insulator ( 35 ), causes. Pressure measuring device according to claim 1, characterized in that - the membrane electrodes ( 19a . 19b ) of measurement capacitor (C _P ) and reference capacitor (C _R ) are separate electrodes, or - the membrane electrodes ( 19 ) of measuring capacitor (C _P ) and reference capacitor (C _R ) by a common capacitors membrane electrode ( 19 ) are formed. Pressure measuring device according to claim 1, characterized in that an inductively coupled to the resonant circuits measuring unit is provided which is designed such that it inductively oscillates the resonant circuits and an inductive coupling to the first resonant circuit of the capacitance of the measuring capacitor (C _p ) and over an inductive coupling to the second resonant circuit of the capacitance of the reference capacitor (C _R ) dependent measured variables determined by which it determines the capacitances of measuring capacitor (C _p ) and reference capacitor (C _R ). Pressure measuring device according to claim 1, characterized in that a measuring unit is provided, the two measuring devices ( 43 ), one of which is a measuring inductance (L _S1 ) inductively coupled to the sensor inductance (L _P ), in particular one on one of the measuring diaphragm ( 7 ) facing away from the back of the body ( 3 ) facing end face of a carrier ( 53 ) planar coil applied from an insulator ( 49 ), of which the other has a measuring inductance (L _S2 ) inductively coupled to the reference inductance (L _R ), in particular one on one of the measuring diaphragm ( 7 ) facing away from the back of the body ( 3 ) facing end face of a carrier ( 53 ) planar coil applied from an insulator ( 51 ), each comprising an exciter device ( 45 ), which generates an alternating voltage with a time-variable frequency, which at a first terminal of the measuring inductance (L _S1 , L _S2 ) of the respective measuring device ( 43 ), and - the one each to the measuring inductance (L _S1 , L _S2 ) of the respective measuring device ( 43 ) connected measuring electronics ( 47 ), which determines at least one of the capacitance of the measuring capacitor (C _p ) and / or the capacitance of the reference capacitor (C _R ) dependent on the basis of the respective measuring inductance (L _S1 , L _S2 ) flowing measurement signal. Pressure measuring device according to claim 12, characterized in that - the oscillating circuits are essentially decoupled oscillating circuits, - the measuring electronics ( 47 ) of the inductive to the sensor inductance (L _P ) coupled measuring inductance (L _S1 ) comprising measuring device ( 43 ) is designed such that it determines a frequency dependent on the capacitance of the measuring capacitor (C _p ) at which a total impedance (Z ¹ _ges (ω)) of a measuring inductance (L _S1 ) and the measuring capacitor (C _p ) has a maximum unit, and - the measuring electronics ( 47 ) of the inductive to the reference inductance (L _R ) coupled measuring inductance (L _S2 ) comprising measuring device ( 43 ) Is constructed such that it (determined C _R) dependent frequency at which the total impedance (Z ² _ges (ω) is one of the capacitance of the reference capacitor) of a through these measuring inductance (L _S2) and coupled thereto, the reference capacitor (C _R ) comprehensive resonant circuit unit has a maximum. Pressure measuring device according to claim 2, characterized in that - the oscillating circuits are inductively and / or capacitively coupled oscillating circuits, - a measuring device ( 43 ), - an inductively coupled to the sensor inductance (L _P ) measuring inductance (L _S1 ), a inductively coupled to the reference inductance (L _R ) measuring inductance (L _S2 ) or both inductively to the sensor inductance (L _P ) and Inductively to the reference inductance (L _R ) coupled measuring inductance (L _S ), esp. A three-dimensional measuring coil ( 57 ), esp. An air coil, or two series-connected measuring coils, in particular two via a line ( 55 ) connected to one of the measuring membrane ( 7 ) facing away from the back of the body ( 3 ) facing end face of a carrier ( 53 ) planar coils applied from an insulator ( 49 . 51 ), comprising - an exciter device ( 45 ), which generates an alternating voltage with a time-variable frequency, which is applied to a first terminal of the measuring inductance (L _S , L _S1 , L _S2 ), and - the measuring electronics connected to the measuring inductance (L _S , L _S1 , L _S2 ) ( 47 ), which is designed such that it determines - two different frequencies (ω _res1 , ω _res2 ) which depend in different ways on the capacitance of the measuring capacitor (C _p ) and the capacitance of the reference capacitor (C _R ), in which a total impedance (Z _ges (ω)) has a maximum unit formed by the measuring inductance (L _S, L _S1, L _S2 ) and the two oscillating circuits coupled thereto and, on the basis of the two frequencies (ω _res1 , ω _res2 ), the capacitance of the unit Measuring capacitor (C _p ) and the capacitance of the reference capacitor (C _R ) determined. Pressure measuring device according to claim 1, characterized in that the measuring device is part of a measuring module, which by means of a releasable mechanical fastening device on a on the of the measuring membrane ( 7 ) facing away from the pressure sensor ( 3 ) is fixable place. Pressure measuring device according to claim 1, characterized in that - measuring capacitor (C _p ) and reference capacitor (C _R ) a membrane electrode common to both capacitors ( 19 ), and - a spatially between measuring electrode ( 21 ) and reference electrode ( 23 ) arranged separating electrode ( 65 ) is provided which electrically at the potential of the membrane electrode ( 19 ) lies.

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