DE102020121584A1 - Differential pressure sensor for determining the differential pressure of two pressures - Google Patents

Abstract

The invention relates to a differential pressure sensor (1) for determining the differential pressure of two pressures (p1, p2) with a measuring mechanism (2) and a converter chamber (3), with a coplanar double membrane system on or in an end region of the measuring mechanism (2) facing the process (4) is provided with two double membranes (4a, 4b) and wherein a differential pressure measuring cell (12) with a pressure-sensitive element (13) is arranged in the converter chamber (3), the two double membranes (4a, 4b) each consisting of a separating membrane ( 5a, 5b) and an overload diaphragm (6a, 6b) arranged behind the separating diaphragm (5a, 5b) in the direction of the pressure effect, with a first pressure chamber (7a) between the first separating diaphragm (5a) and the first overload diaphragm (6a) and between of the first overload diaphragm (6a) and the base body (9), a first additional pressure chamber (8a) is formed, with a second pressure chamber between the second separating diaphragm (5b) and the second overload diaphragm (6b). chamber (7b) and a second additional pressure chamber (8b) is formed between the second overload diaphragm (6b) and the base body (9), a first connecting capillary (10a) being assigned to the first additional pressure chamber (8a), the second additional pressure chamber (8b) a second connecting capillary (10b) is assigned, a first auxiliary capillary (11a) being assigned to the first pressure chamber (7a), a second auxiliary capillary (11b) being assigned to the second pressure chamber (7b), a pressure-transmitting coupling between the first auxiliary capillary ( 11a) and the second connecting capillary (10b) and between the second auxiliary capillary (11b) and the first connecting capillary (10a) in an intermediate module (19) which is provided between the measuring unit (2) and the converter chamber (3), wherein the two pressures (p1, p2) via the connecting capillary (10a, 10b)—protected against overpressure on one side—are hydraulically transmitted to the differential pressure measuring cell (12). the.

Description

The invention relates to a differential pressure sensor for determining the differential pressure of two pressures. The differential pressure sensor according to the invention is preferably used in the field of automation technology.

Differential pressure gauges are used in particular for the continuous measurement of pressure differences in measurement media, e.g. in liquids, vapours, gases and dust. For example, the level of a medium in a container or the flow of a medium through a pipe can be determined from the differential pressure.

A silicon chip is usually used as the pressure-sensitive element. In order to achieve good measuring sensitivity, a differential pressure sensor preferably works in a range that is close to a critical limit value for the pressure (nominal pressure). If the critical limit is exceeded, there is a risk that the chip will be destroyed. Since silicon chips, in particular, have a relatively low overload resistance, overload protection is usually assigned to a differential pressure sensor. This is preferably designed in such a way that it affects the measurement sensitivity and the measurement accuracy of the pressure-sensitive element as little as possible.

From the DE 3 222 620 A1 a pressure difference measuring device has become known which has a pressure measuring transducer device protected against overload. The measuring device has a central receiving body which forms an antechamber on two opposite sides between a membrane bed and a separating membrane. In the receiving body, an additional chamber is provided in each case behind the side facing away from the membrane bed, which is delimited by a prestressed additional membrane. Inside the receiving body there is also a measuring chamber, which is divided into two sub-chambers by the pressure sensor device. Each of the two partial chambers of the measuring chamber is connected to one of the two antechambers via a respective connecting channel. Each of the two connecting channels is connected to one of the two additional chambers via an additional channel.

If the device is exposed to a differential pressure below or in the range of the nominal differential pressure value, then this differential pressure is transmitted to the pressure sensor device via the connecting channels. The additional membranes develop a small effect, which is negligible in a first approximation. If the pressure difference exceeds the nominal pressure difference value by a predetermined value as a result of an overload, the pressure transmitter liquid located below it is pressed into the antechamber assigned to it on the high-pressure side of the separating membrane. The liquid that is pushed out reaches the auxiliary diaphragm on the low-pressure side via the connection channel and the auxiliary channel, causing it to lift. Thus, in the event of an overload, the liquid that is pressed out on the high-pressure side under the separating diaphragm is under the lifting additional diaphragm on the low-pressure side. Consequently, an overload of the pressure sensor device is avoided. In the case of the German patent application, the converter chamber is integrated into the measuring mechanism.

From the WO 2018/165122 A1 a coplanar differential pressure sensor has become known, in which the pressure inputs with separating membrane and overload membrane are arranged in one plane - namely in the end area facing the process - and not on opposite, parallel planes as in the aforementioned German patent application. It is a so-called double membrane system. The advantage of double membrane systems lies in the significantly lower oil volume that is required for the hydraulic operation of the differential pressure sensor. In addition, the pressure-loaded center membrane weld can be dispensed with here, so that the measuring mechanism can be made in one piece. As in the previously mentioned patent application, the overload protection is also arranged in the measuring mechanism in this known solution, ie the crossed capillaries are located in the measuring mechanism. The converter chamber is placed directly on the measuring mechanism or integrated into the measuring mechanism.

The known solutions have several disadvantages: Since the crossed hydraulic pressure feedthroughs are arranged in the measuring mechanism, e.g. in the known coplanar design, for the purpose of oil filling, externally exposed bores are required, which are closed after filling. The closure areas are potential corrosion weak points. In addition, the holes are quite long, which has a negative impact on manufacturing costs. Long bores also inevitably require a larger oil volume, which in turn makes it difficult to implement overload protection in the measuring mechanism. Since defined distances between the pressure ducts must be maintained, there are limits to minimizing the dimensions of the measuring unit.

The object of the invention is to propose a pressure sensor with overload protection and reduced oil volume. At this point, the term "oil volume" is chosen because the hydraulic transmission fluid is usually in the specified measuring range almost incompressible oil, for example a silicone oil.

The object is achieved by a differential pressure sensor for determining the differential pressure of two pressures with a measuring mechanism and a converter chamber, with a coplanar double membrane system with two double membranes being provided on or in an end region of the measuring mechanism facing the process and with a differential pressure measuring cell with a pressure-sensitive one in the converter chamber element is arranged. The pressure-sensitive element is preferably a silicon chip. The differential pressure is determined using a capacitive or resistive measuring method or a resonator.

The two double diaphragms each consist of a separating diaphragm and an overload diaphragm arranged behind the separating diaphragm in the direction of the pressure effect. A first pressure chamber is formed between the first separating diaphragm and the first overload diaphragm, and a first additional pressure chamber is formed between the first overload diaphragm and the base body. Furthermore, a second pressure chamber is formed between the second separating diaphragm and the second overload diaphragm, and a second additional pressure chamber is formed between the second overload diaphragm and the base body. A first connection capillary is assigned to the first additional pressure chamber, and a second connection capillary is assigned to the second additional pressure chamber. In addition, a first auxiliary capillary is associated with the first pressure chamber and a second auxiliary capillary is associated with the second pressure chamber. A pressure-transmitting coupling between the first auxiliary capillary and the second connecting capillary and between the second auxiliary capillary and the first connecting capillary, i.e. a crossing of the auxiliary and connecting capillaries, is arranged in an intermediate module that is provided as a separate unit between the measuring mechanism and the converter chamber. The two pressures are transmitted hydraulically to the differential pressure measuring cell via the connecting capillary - protected against overpressure on one side.

• - Das Messwerk ist einteilig ausgestaltet.
• - Das Messwerk hat einen relativ einfachen und in weiten Teilen symmetrischen Aufbau.
• - Messwerk und Wandlerkammer sind voneinander abgesetzt, dazwischen befindet sich das Zwischenmodul, in dem die Kreuzungen der Hilfskapillaren und er Verbindungskapillaren angeordnet sind. Von dem Zwischenmodul gehen nur die beiden Verbindungsleitungen zur Wandlerkammer;
• - Aufgrund des Abstands zwischen Messwerk und Wandlerkammer lässt sich eine gute mechanische und thermische Entkopplung zwischen Messwerk und Wandlerkammer erreichen.
• - Ein einseitig auftretender Überdruck auf der Hochdruckseite wird auf die Rückseite der Überlastmembrane/Zusatzmembrane der Niederdruckseite und parallel über die Verbindungsleitungen zur Wandlerkammer geleitet. Wandlerkammer und Überlastmembrane liegen druckdynamisch parallel.
• - Eine schnelle Reaktionszeit des Überlastschutzes wird über die Dimensionierung der Hilfs- und Verbindungsleitungen und ggf. über in die Leitungen eingebrachte Dynamikbremsen erreicht.
• - Aufgrund der günstigen Lage der Befüllungsöffnungen im Zwischenmodul lässt sich die Menge der Hydraulikflüssigkeit, insbesondere des Silikonöls, geringhalten.
• - Kosteneinsparung beim Messwerk, insbesondere durch Materialeinsparung (kleine Dimensionen) und infolge einer vereinfachten Fertigung und Bearbeitung, da die Anzahl der Kapillaren gering ist; die Kapillaren können z.B. kostengünstig durch Bohren oder Erodieren hergestellt werden;

The solution according to the invention has the following advantages:

• - The measuring mechanism is designed in one piece.
• - The measuring mechanism has a relatively simple and largely symmetrical structure.
• - Measuring mechanism and converter chamber are separated from each other, between them is the intermediate module, in which the crossings of the auxiliary capillaries and the connecting capillaries are arranged. Only the two connecting lines to the converter chamber go from the intermediate module;
• - Due to the distance between the measuring mechanism and the converter chamber, a good mechanical and thermal decoupling between the measuring mechanism and the converter chamber can be achieved.
• - An overpressure occurring on one side on the high-pressure side is routed to the rear of the overload diaphragm/additional diaphragm on the low-pressure side and parallel via the connecting lines to the converter chamber. In terms of pressure dynamics, the converter chamber and overload diaphragm are parallel.
• - A fast reaction time of the overload protection is achieved by the dimensioning of the auxiliary and connecting lines and, if necessary, by the dynamic brakes incorporated in the lines.
• - Due to the favorable position of the filling openings in the intermediate module, the amount of hydraulic fluid, in particular the silicone oil, can be kept low.
• - Cost savings in the measuring mechanism, in particular through material savings (small dimensions) and as a result of simplified manufacture and processing, since the number of capillaries is small; the capillaries can be produced inexpensively, for example, by drilling or eroding;

The measuring mechanism and the converter chamber, both separate components, are spatially separated from one another via a further component, the intermediate module, or both components are separated from one another via the intermediate module. This achieves a mechanical decoupling between the measuring unit and the sensitive differential pressure measuring cell, which is located in the converter chamber. The joints between the components are of course designed to be pressure-resistant and gas-tight. Due to the reduced oil volume, the measurement error of the differential pressure sensor according to the invention, which is generated by the temperature gradient, is relatively small. Furthermore, a small oil volume also enables the use of smaller diaphragm diameters, which is very advantageous for the realization of a coplanar differential pressure sensor with effective overload protection: the smaller the diameter of the diaphragms, the more sensitive the differential pressure sensor works in the range of very small pressure changes. The pressure sensor according to the invention is therefore also suitable for use in small measuring ranges, that is to say when the pressure changes to be measured are small. The reason for this can be seen in the fact that with a small measuring range, the activation or deflection of the membranes can be kept low, which is reflected in smaller measuring errors.

In general it can be said that to protect the pressure-sensitive element against overpressure, the invention ensures that overpressure occurring on one side on the coplanar double membrane system is limited when it reaches the pressure-sensitive element such that destruction of the pressure-sensitive element is ruled out.

According to one embodiment of the differential pressure sensor according to the invention, the additional membranes are prestressed in such a way that they rest against the base body over their entire surface and are form-fitting and only lift off from the base body when a predetermined critical limit pressure is exceeded. This ensures that the overload or overpressure protection is only activated when the pressure to be measured is so high that there is a risk of the pressure-sensitive element being destroyed. A process membrane / separating membrane, which can be used, inter alia, in connection with the solution according to the invention is, for example, in US 10,656,039 B2 described.

As a result of the full-area and preferably form-fitting contact of the overload membranes on the measuring unit, the measured pressure reaches the pressure chambers, the correspondingly coupled auxiliary and connecting capillaries to the corresponding additional pressure chamber and to the minus or plus side of the pressure-sensitive element. In terms of pressure dynamics, the overload membranes and the pressure-sensitive element are parallel. The deflection of the overload diaphragms is forcibly prevented up to a specified value as a result of their prestressing or is so small that it can be neglected. The preload is designed in such a way that it is larger than the measuring range of the differential pressure sensor. Aging effects are also taken into account here, so that the specified preload is ensured over the entire service life of the differential pressure sensor.

In normal measuring operation, the pressure-sensitive element receives the pressure information for the plus side via the second pressure chamber, the second auxiliary capillary and the first connection capillary coupled to it. The pressure-sensitive element receives the pressure information for the minus side via the first pressure chamber, the first auxiliary capillary and the second connecting capillary coupled to it. Due to the parallel connection of overload membranes and pressure-sensitive element, the pressures applied to both sides of the pressure-sensitive element also act on the backs of the corresponding overload membranes. The pressure-sensitive element deflects according to the applied differential pressure. Incidentally, the effect of the parallel paths via the additional pressure chambers is almost negligible due to the prestressed and form-fitting contact of the overload membranes on the base body of the measuring unit.

The prestressing of the overload membranes ensures that they are only deflected when a critical overpressure occurs on one of the double membranes, which would entail the risk of destroying the pressure-sensitive element. For example, as soon as a critical overpressure occurs at the second separating diaphragm, the second separating diaphragm is moved against the second overload diaphragm until it is in contact with the overload diaphragm. Due to the hydraulic coupling, when the pretension of the first overload membrane is exceeded, it is deflected and the transmission fluid pushed out of the second pressure chamber is pushed into the first additional pressure chamber via the second auxiliary capillary and the first connecting capillary coupled to it. The pressure in the first additional pressure chamber and in the first pressure chamber that is operatively connected to it increases. Shifting ends when all hydraulic fluid is shifted from the high-pressure side to the low-pressure side. The hydraulic pressure in the measuring unit can then no longer rise and the pressure limitation, i.e. the overpressure protection, takes effect.

The connecting capillaries and auxiliary capillaries arranged in the intermediate module are preferably capillary bores.

Furthermore, the connecting capillaries and the auxiliary capillaries in the measuring unit and the connecting capillaries in the converter chamber are also capillary bores. These preferably run essentially parallel to the longitudinal axis of the differential pressure sensor. The transitions between the connecting capillaries and the auxiliary capillaries of the measuring mechanism and intermediate module are preferably realized via capillary tubes which are fastened in the bores in a pressure-tight, non-positive and gas-tight manner. The same preferably applies to the connection of the connection capillaries of the intermediate module and converter chamber via capillary tubes.

In addition, it is proposed that the measuring unit be arranged in a process connection, with the process connection having a diameter in the area facing the process that is larger than the diameter in the area facing away from the process, in which it is pressure-, gas and / or liquid-tight is connected. Due to the separation of measuring mechanism and converter chamber, it is also possible in a simple manner to provide an electrically isolated separation between the two components—measuring mechanism and converter chamber - to realize. More on that later.

In order to ensure that a one-sided overload is limited before it reaches the pressure-sensitive element, an advantageous embodiment of the differential pressure sensor according to the invention proposes that the connecting capillaries and/or the auxiliary capillaries be designed and/or dimensioned in such a way that a pressure above the specified critical limit pressure is reached Overpressure is compensated by the overload protection before the overpressure is transmitted to the differential pressure measuring cell. In order to additionally protect the pressure-sensitive element from pressure peaks, dynamic brakes are installed in the connecting lines or in the connecting capillary between the measuring unit and the intermediate module or between the intermediate module and the converter chamber, according to one embodiment of the differential pressure sensor. The dynamic brakes are flow resistances, e.g. sintered metal inserts. The dynamic brakes can also be designed in such a way that they also assume the function of explosion protection.

Furthermore, it is provided that the auxiliary capillaries in the intermediate module in a first section run essentially parallel to the longitudinal axis of the differential pressure sensor in an area facing the measuring unit and in a second section are routed with a change of direction of approximately 90° to the corresponding connecting capillaries.

An embodiment of the differential pressure sensor according to the invention proposes that two filling holes for filling the hydraulic system of the differential pressure sensor with a hydraulic fluid are provided on the intermediate module, the filling holes being provided as an extension of the auxiliary capillaries running in the second section. The filling bores are each closed in a pressure-tight and gas-tight or at least liquid-tight manner by means of a closure element after filling with the hydraulic fluid. For example, the closure element is a ball that is pressed into the bore and then caulked. It is also possible to weld the closure element in the bore. The closure elements are preferably arranged as close as possible to the crossing points of the auxiliary capillaries with the connecting capillaries. This has the advantage that the filling quantity of transmission fluid in the hydraulic system is reduced. If the closure element is far out, i.e. close to the outer wall of the differential pressure sensor, the required amount of transmission fluid can be reduced by inserting filling elements, e.g. filling rods, into the filling bores.

Due to the arrangement of the outlets of the filling openings in the rear of the sensor and thus in the interior of the differential pressure sensor, the filling holes - behind the closing elements - are protected against corrosion. Furthermore, the corresponding areas of the filling bores can also be cast on the outside; however, this is not absolutely necessary due to the closed position of the filling bores within the housing adapter from the outside.

The connection capillaries can also be designed in such a way that they electrically insulate the converter chamber from the measuring mechanism. The electrical insulation of the converter chamber from the measuring mechanism is preferably carried out via additional elements. These can be arranged in the connecting or auxiliary capillaries of the measuring unit and/or the intermediate module and/or in the connecting capillaries of the converter chamber, in particular in the transitions between the connecting capillaries and the converter chamber. An additional insulating element can be, in particular, a ceramic insulating body or an insulating glazing. The connection must be gas-tight: either it is a soldered connection or a glazing. As stated, the electrical insulators can be provided in the converter chamber and/or in the measuring mechanism and/or in the intermediate module between the measuring mechanism and the converter chamber. In particular, the electrical insulators can also be integrated as intermediate pieces in the connecting capillaries designed as capillary tubes.

• - Guarding für besseres EMV (elektromagnetisches Verhalten);
• - Geringerer bzw. kein Fremdspannungseinfluss;
• - Möglichkeit einen kapazitiven Siliziumchip einzusetzen, bei dem das Guarding eine Voraussetzung ist, dass nur geringere Störkapazitäten auftreten;
• - Der bislang erforderliche isolierende Keramiksockel in der Wandlerkammer kann entfallen; Bei einer bevorzugten Ausgestaltung des erfindungsgemäßen Differenzdrucksensor wird das drucksensitive Element, üblicherweise ein Silizium-Chip, bevorzugt auf einen Silizium-Sockel aufgebracht. Nimmt man einen Silizium-Sockel anstelle des sonst üblichen Glassockels, so lässt sich ein günstigeres thermisches Verhalten (T-Hysterese) erreichen, was sich in einem geringeren statischen Druckfehler niederschlägt. Erklärung: Der E-Modul von Glas ist verschieden von dem E-Modul von Silizium. Bei Glas tritt eine größere Verformung und somit ein größerer Fehler infolge eines statischen Drucks auf als bei Silizium. Da Silizium jedoch kein Isolator ist, sondern eine gewisse Leitfähigkeit aufweist, sind für den sicheren elektrischen Betrieb Mindestisolationsstrecken erforderlich. Diese können z.B. durch in die Verbindungsleitungen eingesetzte keramische Isolierkörper und/oder entsprechend ausgestaltete Dynamikbremsen realisiert werden.
• - Der volle oder partielle Ex-Schutzverguss in der Wandlerkammer, der bislang bei Differenzdrucksensoren erforderlich war, kann entfallen. Bislang wurde der Verguss genutzt, um die Mindestabstände der stromführenden Elemente zum Massepotential möglichst gering halten zu können. Diese Abstandsreduzierung kann bei der Ausgestaltung der Erfindung entfallen, wo die Isolationselemente in den Verbindungskapillaren angeordnet sind. Zwecks Erzielung einer sicheren elektrischen Isolierung können die erforderlichen Mindestabstände um einiges kleiner ausfallen als beiden bislang bekannt gewordenen Lösungen. Auch lassen sich diese Mindestabstände ohne großen Aufwand erreichen.

This makes it possible to separate earth and ground (circuit zero point; Ue = reference point of the electrical supply = ground) and to achieve the following advantages for the current feedthrough:

• - Guarding for better EMC (electromagnetic behavior);
• - Lower or no external voltage influence;
• - Possibility to use a capacitive silicon chip, in which the guarding is a prerequisite that only low interference capacitances occur;
• - The previously required insulating ceramic base in the converter chamber can be omitted; In a preferred embodiment of the differential pressure sensor according to the invention, the pressure-sensitive element, usually a silicon chip, is preferably applied to a silicon base. If you take a silicon base instead of the usual glass base, a more favorable thermal behavior can be achieved ten (T-hysteresis), which is reflected in a lower static pressure error. Explanation: The modulus of elasticity of glass is different from the modulus of elasticity of silicon. Glass suffers from greater deformation and thus greater error due to static pressure than silicon. However, since silicon is not an insulator but has a certain conductivity, minimum insulation distances are required for safe electrical operation. These can be implemented, for example, by using ceramic insulating bodies in the connecting lines and/or correspondingly designed dynamic brakes.
• - The full or partial explosion protection potting in the converter chamber, which was previously required for differential pressure sensors, can be omitted. So far, encapsulation has been used in order to be able to keep the minimum distances between the current-carrying elements and the ground potential as small as possible. This reduction in distance can be omitted in the embodiment of the invention where the insulation elements are arranged in the connecting capillaries. In order to achieve reliable electrical insulation, the required minimum distances can turn out to be somewhat smaller than in the two solutions that have been known hitherto. These minimum distances can also be achieved without great effort.

Furthermore, it is provided that the electrical connecting pins or connecting lines from the electrical converter are routed in a gas-tight manner through one of the end regions of the converter chamber facing away from the process in the direction of an electronic circuit board. The gas-tightness is preferably achieved via glass bushings. Because the transducer chamber is electrically isolated from the metering mechanism, the glass feedthrough PINs can be smaller and therefore more pressure resistant. The aim is in particular to achieve a pressure resistance that is greater than 1280 bar. Smaller PINs/encapsulation elements also allow more PINs to be accommodated in the same space. This may also mean that less oil volume is required.

In order to increase the measurement accuracy, the converter chamber is designed in such a way that the same transmission liquid or oil volumes are present on the low-pressure side and the high-pressure side. The oil volumes on the high-pressure and low-pressure side can be equalized, for example, by creating a corresponding additional volume by enlarging or lengthening one of the bores.

In order to record and subsequently compensate for the influence of the static pressure on the measured values of the differential pressure sensor, a corresponding pressure-sensitive element for measuring the static pressure is provided in the converter chamber. In order to keep the oil volume as small as possible, the pressure-sensitive element for measuring the differential pressure and the pressure-sensitive element for measuring the static pressure are stacked one on top of the other. This is where the advantage of the previously mentioned reduction in the size of the PINs comes into play: since the PINs are smaller, the four additional PINs that provide the measured values of the static pressure element can be accommodated in the converter chamber without having to enlarge it . The arrangement of the PINs is dealt with in more detail below in the description of the figures. However, it is also possible to arrange the pressure-sensitive element for measuring the differential pressure and the pressure-sensitive element for measuring the static pressure next to one another, that is to say virtually in one plane.

• 1: eine Darstellung, die den Aufbau eines erfindungsgemäßen Differenzdruckaufnehmers schematisch skizziert,
• 2: eine Skizze des Verlaufs der Verbindungs- und Hilfsverbindungsleitungen bei einer Ausgestaltung des erfindungsgemäßen Differenzdrucksaufnehmers,
• 3a: eine schematische Darstellung der in 2 gezeigte Ausgestaltung im Überdruck- bzw. Überlastfall,
• 3b eine realistischere Darstellung der Arbeitsweise des koplanaren Differenzdruckmessaufnehmers im Messbetrieb,
• 3c: eine realistischere Darstellung der Arbeitsweise des koplanaren Differenzdruckmessaufnehmers im Überlastfall,
• 4: eine perspektivische Ansicht der Stromdurchführung
• 4a: eine Explosionsdarstellung einer bevorzugten Ausgestaltung der Wandlerkammer mit Stromdurchführung,
• 5: unterschiedliche Darstellungen vorteilhafter Varianten, wie die elektrische Isolierung zwischen Messwerk und Wandlerkammer erreicht wird,
• 6: unterschiedliche Ansichten und Schnitte durch eine Wandlerkammer mit einer Einheit zur Kompensation des statischen Drucks,
• 7: die Schaltung der elektrischen Anschlüsse von Differenzdruckmesszelle und statischer Druckmesszelle, und
• 8: einen Längsschnitt durch einen schematisch dargestellten Differenzdruckmesssaufnehmer, und
• 9: eine Draufsicht auf einen Füllkörper, bei dem die Druckmesszelle und die Druckmesszelle für den statischen Druck in einer Ebene angeordnet sind.

The invention is explained in more detail with reference to the following figures. It shows:

• 1 : an illustration that schematically outlines the structure of a differential pressure sensor according to the invention,
• 2 : a sketch of the course of the connecting and auxiliary connecting lines in an embodiment of the differential pressure sensor according to the invention,
• 3a : a schematic representation of the in 2 configuration shown in the case of overpressure or overload,
• 3b a more realistic representation of the mode of operation of the coplanar differential pressure sensor in measurement mode,
• 3c : a more realistic representation of the operation of the coplanar differential pressure transducer in the event of an overload,
• 4 : a perspective view of the current bushing
• 4a : an exploded view of a preferred embodiment of the converter chamber with current feedthrough,
• 5 : different representations of advantageous variants of how the electrical insulation between the measuring mechanism and the converter chamber is achieved,
• 6 : different views and sections through a converter chamber with a static pressure compensation unit,
• 7 : the wiring of the electrical connections of the differential pressure measuring cell and the static pressure measuring cell, and
• 8th : a longitudinal section through a differential pressure measuring sensor shown schematically, and
• 9 : a plan view of a packing in which the pressure measuring cell and the pressure measuring cell for the static pressure are arranged in one plane.

In 1 the structure of a differential pressure sensor 1 according to the invention is outlined. The differential pressure sensor 1 consists of a measuring unit 2 with the coplanar double membrane system 4a, 4b, an intermediate module 19 and a converter chamber 3 in which the differential pressure measuring cell 12 with the pressure-sensitive element 13 is arranged. In the differential pressure measuring cell 12, the pressures p1, p2 hydraulically transmitted by the separating membranes 5a, 5b are converted into an electrical differential pressure signal; a corresponding measured value is generated. Measuring mechanism 2 and converter chamber 3 are separated from one another by a separate component, which is referred to as intermediate module 19 . According to the invention, the intersection/coupling of the auxiliary capillaries 11a, 11b with the connecting capillaries 10a, 10b, which serves as overpressure protection, is arranged in the intermediate module 19. The connection capillaries 10a, 10b and the auxiliary capillaries 11a, 11b are in 1 only sketchily indicated and therefore not provided with reference symbols.

In 2 shows the course of the connecting capillaries 10a, 10b and the auxiliary capillaries 11a, 11b according to an embodiment of the differential pressure sensor 1 according to the invention. The differential pressure sensor 1 is used to determine the differential pressure of two pressures p1, p2. The measurement of the differential pressure of two pressures p1, p2, for example in a pipe, is used to determine the flow rate. Another application of a differential pressure sensor 1 is, for example, the determination of the fill level of a fluid medium located in a tank.

The coplanar differential pressure sensor 1 consists of a measuring unit 2, a converter chamber 3 and an intermediate module 19 arranged between the two components 2, 3. The measuring unit 2 is arranged in the process connection 21. The process connection 21 has a larger diameter in the area facing the process than in the area facing away from the process. The intermediate module 19 is located in the housing adapter 22. The process connection 21 and the housing adapter 22 are connected to one another via the joint 20 in a pressure-tight, gas-tight and/or liquid-tight manner.

In its end region facing the process, the measuring unit 2 has two double diaphragms 4a, 4b lying in one plane, which together form the coplanar double diaphragm system. Each of the two double diaphragms 4a, 4b consists of a separating diaphragm/process diaphragm 5a, 5b and an overload diaphragm 6a, 6b arranged behind the separating diaphragm 5a, 5b in the direction of the pressure effect. A first pressure chamber 7a is formed between the first separating membrane 5a and the first overload membrane 6a and a first additional pressure chamber 8a is formed between the first overload membrane 6a and the base body 9 . A second pressure chamber 7b is formed between the second separating membrane 5b and the second overload membrane 6b, and a second additional pressure chamber 8b is formed between the second overload membrane 6b and the base body 9. The overload membranes 6a, 6b are prestressed in such a way that in regular measuring operation they essentially lie against the base body 9 over their entire surface and/or with a form fit or force fit and only lift off from the base body 9 when a predetermined critical limit pressure is reached on one side - i.e. on one of the two Separating membranes 5a, 5b - is exceeded. possibly At least one hydraulic channel is provided in the membrane beds and/or the corresponding rear sides of the overload membranes. Destruction of the pressure-sensitive element 13 can only be ruled out if care is taken to ensure that the pressure transmitted to the pressure-sensitive element 13 arranged in the pressure-measuring cell 12 is always below this critical limit pressure.

The first additional pressure chamber 8a is assigned a first connecting capillary 10a and the second additional pressure chamber 8b is assigned a second connecting capillary 10b. The connecting capillaries 10a, 10b lead directly to the pressure measuring cell 12. The two pressures p1, p2 applied to the separating membranes 5a, 5b are connected hydraulically to the Minus side (+) and plus side (+) of the differential pressure measuring cell 12 and the pressure-sensitive element 13 transferred. The transmission medium in the capillary system is a liquid 16 that is largely incompressible in the specified measuring range of the differential pressure sensor 1, e.g. a silicone oil.

The connecting and auxiliary capillaries 10a, 10b, 11a, 11b are preferably designed as capillary bores. However, it is also possible to configure the capillary bores at least in part as capillary tubes 17 . In the case shown, capillary tubes 17 are provided at the transitions of the capillary bores between measuring unit 2 and intermediate module 19 or between intermediate module 19 and converter chamber 3 . The pressure-transmitting coupling between the auxiliary capillaries 11a, 11b and the connecting capillaries 10a, 10b for the purpose of overload protection is achieved by crossing the first auxiliary capillary 11a with the second connecting capillary 10b or the second auxiliary capillary 11b with the first connecting capillary 10a. According to the invention, this intersection is arranged in the intermediate module 19 which is located in the rear space of the sensor behind the measuring unit 2 . The intermediate module 19 is preferably arranged in the interior of the housing adapter 22 in front of the converter chamber 3 .

In order to also ensure that the overload protection takes effect before the pressure is transmitted in parallel to the pressure-sensitive element 13, dynamic brakes 18a, 18b are provided. These also serve to slow down any pressure peaks that may occur. In the case shown, the dynamic brakes 18a, 18b are arranged at the transitions between the connecting capillaries 10a, 10b of the intermediate module 19 and the converter chamber 3. They are advantageously integrated into the capillary tubes 18a, 18b. In connection with the solution according to the invention, the dynamic brakes 18a, 18b can be sintered metal inserts. If the differential pressure measuring transducer 1 is used in an area at risk of explosion, the dynamic brakes 18a, 18b are made of a non-conductive material. In this case, the dynamic brakes 18a, 18b then fulfill a dual function: delayed transmission of the pressure and explosion protection, which is designed according to the required type of explosion protection. It goes without saying that dynamic brakes 18a, 18b in the two variants described above can be integrated at all points within the capillary system at which their use ensures the correct functioning of the overload protection. Additionally or alternatively, the dimensions (length and diameter) of the capillaries are designed in such a way that the overload protection can develop its effect.

The capillary system of the differential pressure sensor 1 is filled with a hydraulic transmission fluid 16 via the filling bores 14a, 14b in the intermediate module 19 . The arrangement and position of the filling holes 14a, 14b is chosen so that the volume of oil required for filling is as small as possible. For this reason, the closure elements 15a, 15b are also provided as close as possible to the crossing points of the filling bores 14a, 14b. The embodiment is preferred in which the closed filling bores 14a, 14b end in the rear space of the sensor and there preferably within the housing adapter 22. Due to this arrangement in the interior of the differential pressure sensor 1, the filling bores 14a, 14b are protected against corrosion, even outside of the closure elements 15a, 15b. Furthermore, the corresponding areas of the filling bores 14a, 14b can be cast to the outside; However, this is due to the closed position of the filling holes 14a, 14b from the outside in 2 configuration shown is not absolutely necessary.

A preferably spherical closure element 15a, 15b is provided as a pressure-tight, gas-tight or at least liquid-tight closure, which is pressed from the outside into the filling bore 14a, 14b and then caulked. In principle, other methods for closing the openings are also available. However, welding is regarded as critical insofar as negative repercussions on the defined properties of the transmission liquid 16 can occur as a result of the temperature increase.

In the 3a is shown schematically by arrows pointing in the direction of how - in the case of an overpressure PeÜL applied on one side - this overpressure PeÜL is transmitted through the coupled capillaries 11b, 10a to the back of the first overload membrane 6a and parallel to the plus side of the pressure-sensitive element 13. The mode of action is related to 3c described in detail.

In the figures 3b and 3c the mode of operation of the coplanar double membrane system 4 is shown in more detail. The figures 3b and 3c refer to those in the figures 3a illustrated embodiment of the differential pressure sensor according to the invention 1.

3b shows the mode of operation of the coplanar membrane system 4 in regular measurement operation. The overload diaphragms 6a, 6b are in full contact with the base body 9 of the measuring unit 2. The system is largely form-fitting, the overload membranes 6a, 6b are suitably prestressed. The measured pressures p1, p2 reach the backs of the overload membranes 6a, 6b and parallel to the converter chamber 3 or to the sides of the pressure-sensitive element 13 via the pressure chambers 7a, 7b, the auxiliary capillaries 11a, 11b and the connecting capillaries 10a, 10b. The overload membranes 6a , 6b and the pressure-sensitive element 13 are parallel in terms of pressure dynamics, so the same pressure acts on both. The differential pressure dp=p ₁ −p ₂ forms on the pressure-sensitive element 13 . The pressure-sensitive element 13 deflects depending on the differential pressure. The overload membranes 6a, 6b are prestressed. The deflection is forcibly prevented up to a specified value. In any case, the bias voltage is greater than the measuring range.

The pressure-sensitive measuring element 13 receives the pressure information for the plus side via the pressure chamber 7b and the connecting capillaries 11b, 10a (+). The pressure information for the minus side (-) of the pressure-sensitive measuring element 13 is transmitted via the pressure chamber 7a and the connecting capillaries 11a, 10b. The effect of the parallel paths via the additional pressure chambers 8a, 8b is almost negligible due to the preloaded and approximately form-fitting contact of the overload membranes 6a, 6b on the base body 9 of the measuring mechanism 2

3c shows the mode of operation of the coplanar membrane system 4 in the event of an overload, ie when a one-sided overload occurs. As before, the overpressure PeÜL also occurs here on the right-hand side of the differential pressure sensor 1 at the separating membrane 4b.

The overload membranes 6a, 6b are prestressed and lie as positively as possible on a suitably shaped bed of the base body 9. Since the overload membrane 6b rests against the base body 9, the pressure in the additional pressure chamber 8b cannot rise. The overload pressure PeÜL reaches the back of the overload diaphragm 6a and the pressure-sensitive element 13 via the pressure chambers 7b, the auxiliary capillary 11b and the connecting capillary 10a which deflects the separating diaphragm 5a and hydraulic fluid/oil 16 is shifted from the high-pressure side to the low-pressure side. Since the pressure in the additional pressure chamber 8a and the subsequent pressure chamber 7a continuously increases, the overload diaphragm 6a and the separating diaphragm 5a are deflected in the direction of the process. The shifting ends when the separating diaphragm 5b rests on the overload diaphragm 6b and the oil has been shifted from the pressure chamber 7b into the additional pressure chambers 8a and. A further increase in pressure is subsequently excluded. As soon as this state is reached, the hydraulic pressure inside the hydraulic system cannot increase any further: the pressure limitation, i.e. the overload protection, takes effect. The pressure applied to the pressure-sensitive element 13 is below the critical limit value.

4 shows a schematic representation of the converter chamber 3 with the two connecting capillaries 10a, 10b. The pressures p1, p2 applied to the separating membranes 5a, 5b are transmitted hydraulically to the pressure-sensitive element 15 via the connecting capillaries 10a, 10b. The pressure p1 is on the plus side, the pressure p2 on the minus side. In this configuration, two vertical (ie parallel to the longitudinal axis of the differential pressure sensor 1) bores and one horizontal bore are required in the converter chamber 3 . It may also make sense to have two filling and closure accesses to make filling easier. The dynamic brakes could make filling more difficult or greatly increase the filling times.

4a shows an exploded view of a cube-shaped configuration of the differential pressure measuring cell 14 and visualizes how the individual components of the differential pressure measuring cell 14 and the current bushing 23 are arranged in the converter chamber 3 . An insulating base (eg, a ceramic base) 31 is bonded to the bottom surface of a recess in the transducer chamber 3 with a suitable adhesive 30 . The pressure measuring cell 12 , which preferably has a silicon chip as the pressure-sensitive element 13 , is connected to the ceramic base 31 by means of an adhesive 32 . For the purpose of minimizing the required volume of oil or the volume of the transmission liquid 21, a filling body 33 is provided, which encloses the pressure measuring cell 12 as closely as possible in the side area. The filling body 33 is closed with a cover 34 . The converter chamber 3 is closed to the outside with a sealing cap 34 for the current feedthrough 23 . The silicon chip 13 is insulated via the insulation base 31, which can be a ceramic base or a glass base which, for example, has a thickness d≧0.5 mm for reasons of explosion protection. Furthermore, the insulation of the silicon chip 15 and its bonded connections 24 is provided by the filling body 33 with the cover 34, which is made of a suitable plastic, for example. The connection capillaries 10a, 10b designed as capillary tubes are shown below.

5 shows different representations of advantageous variants of how the electrical insulation between measuring unit 2 and converter chamber 3 can be realized via insulation elements 25, preferably insulation tubes 25, adapted in or on the capillary tubes. Incidentally, in these configurations, the ceramic base 31 glued in place in the converter chamber 3, as described above, can be dispensed with. The electrical insulation between the measuring unit 2 and the intermediate module is preferably in the area of the capillary tubes 17 between the corresponding connecting capillaries 10a, 10b or at the transition of the capillary tubes 17 to the measuring unit 2 or to the converter chamber 3.

As in the illustration on the left 5 can be seen, the electrically insulating ceramic tubes 25 in the converter chamber 3 ( 5a) , in the intermediate module 19 ( 5b) or between the intermediate module 19 and the converter chamber 3 ( 5c ) to be executed. The insulation preferably achieves potential isolation from ground or the internal ground. This is required for Ex ia safety level and electrical safety. The alternative that the ex-separation also through ent Speaking configuration of the dynamic brakes 18 can be achieved, has already been mentioned before. The differential pressure measuring sensor 1 according to the invention can also be used in potentially explosive areas. To do this, it must meet the ex d safety requirements, for which additional safety measures are required.

6 shows a converter chamber 3 or its components and different sections through the converter chamber 3. In this embodiment, a measuring cell 27 is also provided for determining the static pressure. In 6a shows the power bushing 23 with an advantageous arrangement of the connection pins 26 for the differential pressure measuring cell 12 with the pressure-sensitive element 13 and the measuring cell 27 arranged above it for determining the static pressure. The PINs 26 are preferably found symmetrically in the edge area of the two pressure measuring cells 12, 27, which are preferably stacked one on top of the other. However, it can also be an advantage to position at least one PIN asymmetrically in order to make subsequent processing, for example soldering on the circuit board, safer later in the process (poka-yoke principle). Either the PINs 26 all end in one plane or in parallel planes. Two pins 1.1, 1.2 of the eight pins 26 ( 7c ) can be used without insulation, e.g. B. soldered, since they are on ground / housing potential.

PINS 2 and 3 could be electrically connected together, i.e. in a common PIN, to potential ( 7b) . The electrical insulation then preferably takes place via a glazing. If the ground PINS 1.1, 1.2, which correspond to PINS 1, 8, and PINS 2, 3 for the power supply are combined, the two bridges are connected in parallel to the power supply. This circuit is shown in 7c .

In order to meet the requirements of electrical safety and for use in hazardous areas, all PINs 26 are arranged or spaced such that there is sufficient dielectric strength both from PIN 26 to PIN 26 and from PIN 26 to the housing/ground of the converter chamber 3 is. Since the oil volume is all the smaller, the smaller the interior space of the converter chamber 3 is dimensioned, the interior space preferably has a diameter of <10 mm, in particular <8 mm.

6b shows a longitudinal section through the pressure measuring cells 12, 27 stacked one on top of the other. The power feedthrough 23 is designed to be pressure-resistant and gas- or liquid-resistant. The PINs 26 are either soldered or glazed. Alternatively they are pressed in or impulse welded. Only the ground PINS are arranged in the housing without insulation, all others must be insulated. This is possible if the housing is isolated and connected to the measuring unit via the capillaries. Otherwise, all PINs (including the ground PINS) must be electrically isolated.

In order to minimize the oil volume required, the differential pressure measuring cell 12 with the bonding wires 24 is embedded as closely as possible in the filling body 33 and the filling body cap 37 . The packing cap 37 has a recess for receiving the chip/static pressure cell 27 . The sealing cap 35 follows an insulating film 29. 6c shows a cross section in the area of the differential pressure measuring cell 14, while 6d shows a section in the area of the chip 27 for measuring the static pressure.

In the figures 7a , 7b and 7c the circuits for the previously mentioned arrangements of the PINs 26 are shown. The differential pressure (1.2) and the static pressure (1.1) are measured via two resistance bridges. The measured values are sent to an electronic circuit board 36 for further processing. 7a shows the basic connection diagram of the two Si chips 15, 27. In order to be able to operate the circuit completely independently, eight PINs 26 are required; minimum are six PINs 26 ( 7b) necessary. 7c shows a circuit with 7 PINs 26. This interim solution has a separate plus supply, but a common ground. The advantage of using a smaller number of PINs 26 is clearly that space can be saved. The PINs 26 for the ground connection can also be implemented as a direct connection between the corresponding PIN 26 or the corresponding PINs 26 and the conductive housing (metal housing). The connection can be made by soldering, pressing in or welding.

• (2), (3): PINs 26 für den Anschluss der Versorgungsspannung,
• (4), (5): PINs 26 für das Brückenausgangssignal der statischen Druckmesszelle 27,
• (6), (7): PINs 26 für das Brückenausgangssignal der Differenzdruckmesszelle 12,
• 1 = (1.1): Versorgungsspannungs-Minusanschluss (Masse),
• 8 = (1.2): Versorgungsspannungs-Minusanschluss (Masse).

Below is the function of each in 7 shown PINs 26 listed:

• (2), (3): PINs 26 for connecting the supply voltage,
• (4), (5): PINs 26 for the bridge output signal of the static pressure measuring cell 27,
• (6), (7): PINs 26 for the bridge output signal of the differential pressure measuring cell 12,
• 1 = (1.1): supply voltage minus connection (ground),
• 8 = (1.2): supply voltage minus connection (ground).

As already described above, a common PIN 26 can also be used for the ground connection.

• ① Innenvolumen, das ev. mit einem Verguss ausgefüllt ist
• ② Schweißung zwischen Gehäuseadapter 22 und Messwerk 2
• ③ Druckzuführung Wandlerkammer 3 - Messwerk 2
• ④ Druckzuführung zur Wandlerkammer 3
• ⑤ Stromdurchführung 23 mit PIN/Einglasung
• ⑥ Ölverschluss
• ⑧ Trennung zwischen Gehäuse und Sensorrückraum
• ⑨ Exd-Gewinde Gehäuse-Sensor, z.B. über ein Second Containment und/oder einen Verguss
• ⑩ Verschlusskappe 35 Stromdurchführung 23 (GDF)

8th shows a longitudinal section through a differential pressure measuring sensor 1 shown schematically 8th lists the different zones AG to which the differential pressure sensor 1 is exposed. Since the zones are listed by name in the figure, they will not be repeated at this point. The encircled numbers schematically document components that characterize the basic structure of the differential pressure sensor 1 according to the invention:

• ① Inner volume that may have been filled with encapsulation
• ② Welding between housing adapter 22 and measuring unit 2
• ③ Pressure supply converter chamber 3 - measuring mechanism 2
• ④ Pressure supply to converter chamber 3
• ⑤ Power feedthrough 23 with PIN/glazing
• ⑥ Oil cap
• ⑧ Separation between the housing and the rear of the sensor
• ⑨ Exd thread housing sensor, eg via a second containment and/or encapsulation
• ⑩ Closing cap 35 power feedthrough 23 (GDF)

9 shows a plan view of a packing 33 in which the pressure measuring cell 12 and the pressure measuring cell 27 for the static pressure are arranged in one plane. The distances between the pins - can be seen in the 9 only the recesses 38 for the pins from the power feedthrough - are chosen so that a galvanic isolation is ensured.

Reference List

1

differential pressure sensor

2

measuring mechanism

3

converter chamber

4

double membrane system

4a, 4b

first double diaphragm, second double diaphragm

5a, 5b

first separating diaphragm, second separating diaphragm

6a, 6b

first overload diaphragm, second overload diaphragm

7a, 7b

first pressure chamber, second pressure chamber

8a, 8b

first additional pressure chamber, second additional pressure chamber

9

body

10a, 10b

first connection capillary, second connection capillary

11a, 11b

first auxiliary capillary, second auxiliary capillary,

12

differential pressure measuring cell

13

pressure-sensitive differential pressure element

14a, 14b

filling hole

15a, 15b

closure element

16

transmission fluid

17

capillary tubes

18a, 18b

dynamic brake

19

intermediate module

20

coincidence

21

process connection

22

housing adapter

23

current feedthrough

24

bond connection

25

isolation tube

26

pin code

27

Measuring cell for determining the static pressure

28

Packing cap with recess

29

Insulation film / PTFE film

30

Adhesive for gluing the insulation base (ceramic base)

31

ceramic base

32

Adhesive for gluing the pressure measuring cell

33

random packing

34

packing cover

35

Closing cap for power feedthrough

36

electronics board

37

fill cap

38

Recess for pin

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited 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

• DE 3222620 A1 [0004]
• WO 2018/165122 A1 [0006]
• US 10656039 B2 [0014]

Claims (18)

Differential pressure sensor (1) for determining the differential pressure of two pressures (p1, p2) with a measuring mechanism (2) and a converter chamber (3), with a coplanar double diaphragm system with two double diaphragms ( 4a, 4b) and wherein a differential pressure measuring cell (12) with a pressure-sensitive element (13) is arranged in the converter chamber (3), the two double membranes (4a, 4b) each consisting of a separating membrane (5a, 5b) and an in In the direction of the pressure effect, there are overload diaphragms (6a, 6b) arranged behind the separating diaphragm (5a, 5b), with a first pressure chamber (7a) between the first separating diaphragm (5a) and the first overload diaphragm (6a) and between the first overload diaphragm (6a) and the base body (9) a first additional pressure chamber (8a) is formed, wherein between the second separating membrane (5b) and the second overload membrane (6b) a second pressure chamber (7b) and between the second A second additional pressure chamber (8b) is formed between the overload diaphragm (6b) and the base body (9), a first connecting capillary (10a) being assigned to the first additional pressure chamber (8a), a second connecting capillary (10b) being assigned to the second additional pressure chamber (8b). a first auxiliary capillary (11a) being assigned to the first pressure chamber (7a), a second auxiliary capillary (11b) being assigned to the second pressure chamber (7b), a pressure-transmitting coupling between the first auxiliary capillary (11a) and the second connecting capillary ( 10b) and between the second auxiliary capillary (11b) and the first connecting capillary (10a) in an intermediate module (19) provided between the measuring mechanism (2) and the converter chamber (3), the two pressures (p1, p2 ) via the connecting capillary (10a, 10b) and auxiliary capillaries (11a, 11b) - protected against overpressure on one side - will be hydraulically transmitted to the differential pressure measuring cell (12). n. differential pressure sensor claim 1 , wherein the overload membranes (6a, 6b) are prestressed in such a way that they rest against the base body (9) and only lift off from the base body (9) when a predetermined critical limit pressure is exceeded. Differential pressure sensor according to one or more of the preceding claims, wherein the connecting and auxiliary capillaries (10a, 10b, 11a, 11b) arranged in the intermediate module (19) are capillary bores. Differential pressure sensor according to one or more of the preceding claims, wherein the connecting capillaries (10a, 10b) and the auxiliary capillaries (11a, 11b) in the measuring unit (2) and the connecting capillaries (10a, 10b) in the converter chamber (3) are capillary bores which are essentially parallel to the longitudinal axis of the Differential pressure sensor (1) run, and the transitions between the connecting capillaries (10a, 10b) and the auxiliary capillaries (11a, 11b) of the measuring mechanism (2) and intermediate module (19) and between the connecting capillaries (10a, 10b) of the intermediate module (19) and converter chamber (3) via capillary tubes (17) are realized. Differential pressure sensor according to one or more of Claims 1 - 4 , wherein the measuring unit (2) is arranged in a process connection (21), the process connection (21) in the area facing the process having a diameter which is larger than the diameter in the area facing away from the process, in which it is connected to the intermediate module ( 19) or the housing adapter (22) is connected in a pressure-tight, gas-tight and/or liquid-tight manner. Differential pressure sensor according to one or more of Claims 1 until 5 , wherein the connecting capillaries (10a, 10b) and/or the auxiliary capillaries (11a, 11b) are designed and/or dimensioned in such a way that an overpressure (peÜL) above the predetermined critical limit pressure is limited by means of the overload protection before the overpressure is applied to the Differential pressure measuring cell (12) is transmitted. Differential pressure sensor according to one or more of Claims 1 until 6 , wherein in each of the connecting capillaries (10a, 10b) at least one dynamic pressure brake (18a, 18b) is used. Differential pressure sensor according to one or more of the preceding claims, wherein the auxiliary capillaries (11a, 11b) in the intermediate module (19) run essentially parallel to the longitudinal axis (L) of the differential pressure sensor (1) in a first section in an area facing the measuring unit (2) and are guided in a second section with a change of direction of approximately 90° to the corresponding connecting capillaries (10b, 10a). differential pressure sensor claim 8 , wherein two filling holes (14a, 14b) for filling the hydraulic system of the differential pressure sensor (1) with a hydraulic fluid (16) are provided on the intermediate module (19), the filling holes (14a, 14b) in Ver extension of the auxiliary capillaries (11a, 11b) running in the second section, with the filling bores (14a, 14b) each being closed pressure-tight and gas-tight or at least liquid-tight by means of a closure element (15a, 15b) after filling with the hydraulic fluid (16). Differential pressure sensor according to one or more of the preceding claims, wherein electrical connection pins are guided in a gas-tight manner through one of the end regions of the converter chamber (3) facing away from the process in the direction of an electronic circuit board (36). Differential pressure sensor according to one or more of the preceding claims, electrical insulators (25) being provided in the connecting capillaries (10a, 10b, 17a, 17b) which electrically insulate the converter chamber (3) from the measuring mechanism (2). differential pressure sensor claim 11 or any of the preceding Claims 1 - 10 , wherein the connecting capillaries (10a, 10b, 17a, 17b) are provided at least in sections with an electrical insulator (), in particular a ceramic insulating body or an insulating glazing, and/or via a gas-tight connection in the corresponding capillaries of the measuring unit (2) and /or the converter chamber (3) or the capillary tubes 17a, 17b). Differential pressure sensor according to one or more of the preceding claims, wherein the electrical insulators (25) are provided in the converter chamber (3) and/or in the measuring mechanism (2) and/or in the space between the measuring mechanism (2) and the converter chamber (3). Differential pressure sensor according to one or more of the preceding claims, wherein the electrical insulators (25) are each integrated as intermediate pieces in the connecting capillaries (10a, 10b) designed as capillary tubes (17a, 17b). Differential pressure sensor according to one or more of the preceding claims, wherein the pressure-sensitive element (13) is a silicon chip, and wherein the differential pressure (p2-p1) is determined using a capacitive or resistive measuring method or resonator. Differential pressure sensor according to one or more of the preceding claims, wherein the converter chamber (3) is designed in such a way that the same transmission liquid volumes are present on the low-pressure side (-) and the high-pressure side (+). Differential pressure sensor according to one or more of the preceding claims, wherein a pressure-sensitive element (27) for measuring the static pressure is provided in the converter chamber (3). Differential pressure sensor according to one or more of the preceding claims, wherein the pressure-sensitive element (13) for measuring the differential pressure and the pressure-sensitive element (27) for measuring the static pressure are stacked on top of one another or arranged next to one another in the converter chamber (3).

Images