DE102020121580A1 - 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), the measuring mechanism (2) and a converter chamber (3) being connected via an intermediate area (15) are separated from one another, with a coplanar double membrane system (4) with two double membranes (4a, 4b) being provided on or in an end region (14) of the measuring mechanism (2) facing the process, and with a differential pressure measuring cell (12) in the converter chamber (3) with a pressure-sensitive element (13), the two double membranes (4a, 4b) each consisting of a separating membrane (5a, 5b) and an overload membrane (6a, 6b) arranged behind the separating membrane (5a, 5b) in the direction of the pressure effect , wherein between the first separating membrane (5a) and the first overload membrane (6a) a first pressure chamber (7a) and between the first overload membrane (6a) and the base body (9) a first additional pressure chamber (8a) formed ldet, a second pressure chamber (7b) being formed between the second separating diaphragm (5b) and the second overload diaphragm (6b) and a second additional pressure chamber (8b) being formed between the second overload diaphragm (6b) and the base body (9), the first A first connecting capillary (10a) or a second connecting capillary (10b) is assigned to the additional pressure chamber (8a) or the second additional pressure chamber (8b), the two connecting capillaries (10a, 10b) transmitting the pressure hydraulically to the converter chamber (3), and a first auxiliary capillary (11a) or a second auxiliary capillary (11b) being assigned to the first additional pressure chamber (8a) or the second additional pressure chamber (8b) to protect the pressure-sensitive element (13) against excess pressure, the first pressure chamber (7a) or . A third auxiliary capillary (11c) and a fourth auxiliary capillary (11d) are assigned to the second pressure chamber (7b), the hydraulic connections/crossings of the first auxiliary capillary (11 a) is arranged with the fourth auxiliary capillary (11d) and the second auxiliary capillary (11b) and the third auxiliary capillary (11c) in the intermediate region (14) of the measuring unit (2) and converter chamber (3).

Description

The invention includes 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 - specifically 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, for example in the known coplanar design, bores that are exposed from the outside are required for the purpose of oil filling, 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 an oil, e.g. a silicone oil.

The object is achieved by a differential pressure sensor for determining the differential pressure of two pressures p1, p2 with a measuring mechanism and a converter chamber, the measuring mechanism and converter chamber being separated from one another via an intermediate area or an intermediate module. A coplanar double membrane system with two double membranes is provided on or in an end area of the measuring unit facing the process. A differential pressure measuring cell with a pressure-sensitive element is arranged in the converter chamber. The two double membranes each consist of a separating membrane and an overload membrane arranged behind the separating membrane in the direction of the pressure effect, with a first pressure chamber being formed between the first separating membrane and the first overload membrane and a first additional pressure chamber being formed between the first overload membrane and the base body. 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 connecting capillary or a second connecting capillary is assigned to the first additional pressure chamber or the second additional pressure chamber. The pressures p1, p2 applied to the separating membranes reach the converter chamber hydraulically via the two connecting capillaries. In order to protect the pressure-sensitive element against excess pressure, a first auxiliary capillary or a second auxiliary capillary is assigned to the first additional pressure chamber or the second additional pressure chamber, and a third auxiliary capillary or a fourth auxiliary capillary is assigned to the first pressure chamber or the second pressure chamber, the connections/intersections are arranged between the first auxiliary capillary and the third auxiliary capillary or between the second auxiliary capillary and the fourth auxiliary capillary for the purpose of a pressure-transmitting coupling in the intermediate region of the measuring mechanism and the converter chamber.

• - Das Messwerk ist einteilig, quasi monolithisch, ausgestaltet,
• - Das Messwerk hat einen relativ einfachen und symmetrischen bzw. vollsymmetrischen Aufbau,
• - Kosteneinsparung beim Messwerk, insbesondere durch Materialeinsparung (kleine Dimensionen) und infolge einer vereinfachten Fertigung und Bearbeitung, da die Querbohrungen entfallen; die kleineren Bohrungen können z.B. kostengünstig durch Erodieren oder durch Bohren hergestellt werden;
• - Als Verbindung zwischen Messwerk und Wandlerkammer gibt es nur die beiden Verbindungsleitungen;
• - Durch das quasi Nichtvorhandensein der Zusatzdruckkammern im normalen Messbetrieb, ist das benötigte Ölvolumen erheblich reduziert;
• - Eine weitere Reduktion des benötigten Ölvolumens ist dadurch möglich, da ggf. die Befüllungsbohrungen und die langen Querbohrungen im - relativ zur Wandlerkammer größer dimensionierten - Messwerk entfallen. Die Befüllung erfolgt - gemäß einer nachfolgend noch näher beschriebenen bevorzugten Ausgestaltung - über zumindest eine Befüllungsöffnung in der Wandlerkammer. Somit entfällt die korrosionsanfällige Befüllungsöffnung bzw. der korrosionsanfällige Befüllverschluss am Messwerk. Alternativ ist natürlich auch die Befüllung über das Messwerk möglich. Eventuell können auch zwei Befüllungsöffnungen bzw. - zugänge sinnvoll sein: einer am Messwerk und einer an der Wandlerkammer.
• - Der Anschluss an die Wandlerkammer erfolgt als Reihenschaltung; der Druck wird von der Hochdruckseite zuerst auf die Rückseite der Überlastmembrane der Niederdruckseite geleitet und gelangt erst dann zu den Verbindungsleitungen, die zur Wandlerkammer führen. Dies hat erhebliche Vorteile bezüglich des Druckdynamikschutzes des drucksensitiven Elements, das auch Primärsensorelement genannt wird. Durch Variation der Kapillardurchmesser oder durch Zusatzelemente, wie z.B. Sinterelemente, lässt sich dieser Vorteil noch verstärken. Dies wird an einer nachfolgenden Stelle noch näher beschrieben.

The solution according to the invention has the following advantages:

• - The measuring mechanism is designed in one piece, almost monolithically,
• - The measuring mechanism has a relatively simple and symmetrical or fully symmetrical structure,
• - Cost savings in the measuring mechanism, in particular through material savings (small dimensions) and as a result of simplified production and processing, since the cross holes are omitted; the smaller bores can be produced inexpensively, for example, by eroding or by drilling;
• - As a connection between the measuring mechanism and the converter chamber, there are only the two connecting lines;
• - Due to the virtual non-existence of the additional pressure chambers in normal measuring operation, the required oil volume is significantly reduced;
• - A further reduction in the required oil volume is possible because the filling holes and the long cross holes in the measuring mechanism, which is larger than the converter chamber, are no longer required. According to a preferred embodiment described in more detail below, the filling takes place via at least one filling opening in the converter chamber. This eliminates the corrosion-prone filling opening or the corrosion-prone filling cap on the measuring mechanism. Alternatively, filling via the measuring mechanism is of course also possible. Two filling openings or accesses may also be useful: one on the measuring mechanism and one on the converter chamber.
• - The connection to the converter chamber is made in series; the pressure is first routed from the high-pressure side to the back of the overload diaphragm on the low-pressure side and only then reaches the connecting lines that lead to the converter chamber. This has considerable advantages with regard to the pressure dynamics protection of the pressure-sensitive element, which is also called the primary sensor element. This advantage can be increased even further by varying the capillary diameter or by using additional elements such as sintered elements. This is described in more detail at a later point.

According to the invention, it is provided that the measuring mechanism and the converter chamber are not only separate components, but that the measuring mechanism and the converter chamber are also spatially separated or spaced apart from one another. As a result, the measuring mechanism and the measuring unit in the converter chamber are mechanically decoupled from one another. The separation is of course designed to be pressure-resistant and gas-tight. Due to the reduced oil volume, the measurement error caused by the temperature gradient is lower. Furthermore, due to the smaller oil volume, smaller membranes are also possible, which is important for realizing a coplanar sensor. Small membranes, on the other hand, are required for effective overload protection. This is very important for the realization of the coplanar sensor and enables small measuring ranges. In turn, small measuring ranges mean that the activation of the membranes can be kept low, which is associated with smaller measuring errors.

In general it can be said that in order to protect the pressure-sensitive element against overpressure, it is ensured according to the invention that an overpressure occurring on one side on the pressure-sensitive element is limited in such a way that destruction of the pressure-sensitive element is ruled out. Further advantages of the invention result from the configurations of the differential pressure measuring sensor according to the invention, which are mentioned below.

According to one embodiment of the differential pressure sensor according to the invention, the additional membranes are prestressed in such a way that they lie substantially over the entire surface and/or form-fitting on the base body and only lift off the base body when a predetermined critical limit pressure is exceeded. possibly At least one hydraulic channel is provided in the membrane beds and/or on the corresponding rear sides of the overload membranes. 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.

Advantageously, the capillaries in the measuring unit run essentially parallel. Alternatively, of course, it is also possible for the capillaries to be arranged at an angle of less than 90°, preferably less than 45°, to the longitudinal axis of the measuring unit or the differential pressure sensor.

Measuring mechanism and converter chamber are spaced apart. The connecting and auxiliary capillaries are designed as capillary tubes in the intermediate area and are connected to the measuring mechanism and the converter chamber in a pressure-tight, non-positive and gas-tight manner. The capillary tubes open into appropriately arranged and/or designed capillary bores in the converter chamber and in the measuring mechanism. Alternatively, the connections/intersections of the auxiliary capillaries as well as the passage of the connection capillaries in an intermediate module are implemented as capillary bores. Due to the separation of measuring mechanism and converter chamber, it is also possible in a simple manner to implement an electrically isolated separation between the two components—measuring mechanism and converter chamber. More on that later.

The converter chamber can be of any shape, as long as it is compact. Preferably, the transducer chamber has a cube shape, or a cylindrical shape, or a cylindrical shape with flattened opposing portions. Two connecting capillaries, which are preferably arranged parallel to one another, are located at their end region facing the process.

In order to ensure that an overload is compensated for 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 an overpressure that is above the specified critical limit pressure 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 against pressure peaks, dynamic brakes are built into the connecting lines/connecting capillaries between the measuring mechanism and the converter chamber, according to one embodiment of the differential pressure measuring transducer. The dynamic brakes are flow resistances, e.g. the dynamic brakes are sintered metal inserts. The dynamic brakes can also be designed in such a way that they also assume the function of explosion protection.

Two filling bores are provided in an end area of the converter chamber facing away from the process, in particular in the end area facing away from the process or the side wall of the converter chamber. The hydraulically communicating components are filled with a hydraulic transmission fluid via the filling bores, which end in the connecting lines leading to the converter chamber. The transmission liquid is preferably an almost incompressible liquid, e.g. a silicone oil, with a low coefficient of thermal expansion. Two filling bores are preferably provided, which are arranged parallel to the longitudinal axis of the differential pressure sensor as an extension of the bores of the connecting capillaries. After filling, the filling bores are closed in a pressure-tight, gas-tight or at least liquid-tight manner by means of a closure element. 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.

Alternatively, it is provided that two additional filling holes are provided in the measuring mechanism. The two filling bores are provided essentially parallel to the connecting lines and auxiliary lines and symmetrically to one another in the measuring mechanism. They preferably extend between the end face of the end region of the measuring unit facing away from the process and one of the two additional pressure chambers.

An advantageous embodiment of the differential pressure sensor according to the invention provides that the connecting capillaries, which—as already described—are preferably small capillary tubes, are designed in such a way that they electrically insulate the converter chamber from the measuring mechanism. The electrical separation is preferably realized in that the connecting capillaries and the auxiliary capillaries are provided at least in sections with a ceramic insulating body or an insulating glazing and are fastened via a soldered connection or a glazing in the corresponding bores of the measuring mechanism or the converter chamber. Since only the connecting capillaries open into the converter chamber, it is of course sufficient to insulate them - as described above.

For the purpose of electrical isolation, the ceramic insulating body or the insulating glazing can therefore be provided in the converter chamber and/or in the measuring mechanism and/or in the space between the measuring mechanism and the converter chamber. Electrical insulation in the space between the measuring mechanism and the converter chamber is preferably achieved in that the ceramic insulating body or the insulating glazing is integrated as an intermediate piece 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 a silicon base is used instead of the usual glass base, a more favorable thermal behavior (T hysteresis) can be achieved, 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.

According to an advantageous development of the differential pressure sensor according to the invention, the pressure-sensitive element is a silicon chip; the differential pressure is determined using a capacitive or resistive measuring method. A resonator can also be used above this.

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. This is preferably done via glass bushings. Since the transducer chamber is electrically isolated from the measuring mechanism, the glass feedthroughs for the PINs can be smaller; they are therefore more pressure-resistant. The aim is in particular to achieve a pressure resistance that is greater than 1280 bar. Smaller glazing elements also allow more PINs to be accommodated in the same space. This may also mean less oil volume.

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.

To determine the influence of static pressure on the readings of the differential pressure sensor to detect and subsequently to compensate, 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 above the other or arranged next to one another. This is where the advantage of the previously mentioned miniaturization of the PINs comes into play: Since the glass feedthroughs for the PINs are smaller, the four additional PINs, which provide the measured values of the static pressure element (absolute pressure measuring cell), 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.

• 1: eine Darstellung, die den Aufbau eines erfindungsgemäßen Differenzdruckaufnehmers schematisch skizziert,
• 2a: eine Skizze des Verlaufs der Verbindungs- und Hilfsverbindungsleitungen bei einer Ausgestaltung des erfindungsgemäßen Differenzdrucksaufnehmers,
• 3a - 3c: eine Ausgestaltung des erfindungsgemäßen Differenzdruckmessaufnehmers im Überdruck- bzw. Überlastfall mit unterschiedlichen Varianten an Befüllungsbohrungen zur Befüllung des Hydrauliksystems mit Übertragungsflüssigkeit,
• 4: eine schematische Darstellung der Wandlerkammer mit dem Verlauf der beiden Verbindungskapillaren,
• 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,
• 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,
• 2a : 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 - 3c : an embodiment of the differential pressure sensor according to the invention in the event of excess pressure or overload with different variants of filling bores for filling the hydraulic system with transmission fluid,
• 4 : a schematic representation of the converter chamber with the course of the two connecting capillaries,
• 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 switching of the electrical connections of the differential pressure measuring cell and static pressure measuring cell,
• 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 is composed of a measuring unit 2 with the coplanar double membrane system 4a, 4b and a converter chamber 3 in which the differential pressure measuring cell 14 is arranged. The differential pressure measuring cell 14 converts the pressures p1, p2 hydraulically transmitted by the process diaphragms or the separating diaphragms 5a, 5b into an electrical differential pressure signal and generates a corresponding measured value. Measuring mechanism 2 and converter chamber 3 are separated from one another by an intermediate area 13 . According to the invention, the crossing of the auxiliary capillaries 11a, 11b, 11c, 11d serving as overpressure protection is realized in the intermediate region 13 . Connection capillaries and auxiliary capillaries are in 1 only sketchily indicated and therefore not provided with reference symbols.

In 2 shows the course of the connecting capillaries 10a, 10b, the auxiliary capillaries 11a, 11b, 11c, 11d and the coupling capillaries 12.1, 12.2 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. A further application of a differential pressure measuring sensor 1 is, for example, determining the fill level of a fluid medium located in a tank.

The differential pressure sensor 1 consists of a measuring unit 2 and a converter chamber 3, with the measuring unit 2 and the converter chamber 3 being separated from one another by an intermediate region 19. A coplanar double membrane system 4 with two double membranes 4a, 4b is provided on or in an end region 14 of the measuring unit 2 facing the process. A differential pressure measuring cell 12 with a pressure-sensitive element 13 is arranged in the converter chamber 3 .

The two double diaphragms 4a, 4b each consist of a process diaphragm 5a, 5b or a separating 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 . Furthermore, between the second separating membrane 5b and the second overload membrane 6b is a second pressure chamber 7b and between of the second overload membrane 6b and the base body 9, a second additional pressure chamber 8b is formed. A first connecting capillary 10a or a second connecting capillary 10b is assigned to the first additional pressure chamber 7a or the second additional pressure chamber 7b, via which the pressures p1, p2 present at the separating membranes 5a, 5b are hydraulically transmitted to the converter chamber 3.

To protect the pressure-sensitive element 15 from excess pressure/overload, the first additional pressure chamber 8a or the second additional pressure chamber 8b has a first auxiliary capillary 11a or a second auxiliary capillary 11b, and the first pressure chamber 7a or the second pressure chamber 7b has a third auxiliary capillary 11c or a fourth Assigned auxiliary capillary 11d. The connections/intersections of the auxiliary capillaries 11a, 11b, 11c, 11d for the purpose of a pressure-transmitting coupling between the first auxiliary capillary 11a and the fourth auxiliary capillary 11d or between the second auxiliary capillary 11b and the third auxiliary capillary 11c are in the intermediate area 19 of the measuring unit 2 and the transducer chamber 3 arranged. At least in the intermediate area 19, the capillaries are preferably designed as capillary tubes.

In normal measurement operation, the pressure p1 is transmitted to the minus side of the pressure-sensitive element 13 via the separating membrane 5a, the auxiliary capillary 11c, the auxiliary capillary 11b and the connecting capillary 10b. The pressure p2 is transmitted to the plus side of the pressure-sensitive element 13 via the separating membrane 5b, the auxiliary capillary 11d, the auxiliary capillary 11a and the connecting capillary 10a. If the overload membranes 6a, 6b are in a form-fitting manner on the base body 9 of the measuring unit 2, a hydraulic channel may have been introduced in the overload membranes 6a, 6b or in the two membrane beds in the base body.

In the figures 3a , 3b and 3c configurations of the differential pressure sensor 1 according to the invention are shown in the event of overload or excess pressure. The figures differ only with regard to the arrangement and/or configuration of the filling bores 14a, 14b. A description of the 3a .

In the case shown, an overpressure peÜL occurs at the separating diaphragm 5b. Without the overpressure protection device according to the invention, the overpressure peÜL would be transferred to the plus side of the pressure-sensitive element 13 . Due to the one-sided overload, there would be a risk that the silicon chip 13 would be destroyed. As a result of the overpressure PeÜL, the separating membrane 5b is moved according to the invention against the overload membrane 6b, which is essentially in positive contact with the base body 9 . The movement is stopped when the separating diaphragm 5b is pressed against the overload diaphragm 6b. Since behind the overload membrane 6b there is hardly any transfer liquid 16 that can be displaced, the overpressure cannot find its way via the connecting capillary 10b to the minus side of the pressure-sensitive element. The overpressure peÜL is hydraulically transmitted from the pressure chamber 7b via the auxiliary capillary 11d and the auxiliary capillary 11a coupled to it via a transverse bore to the back of the overload membrane 6a of the first coplanar double membrane 4a. As soon as the overpressure PeÜL exceeds the preload of the overload diaphragm 6a, the latter detaches from its diaphragm bed on the base body 9 and transfer liquid 16 is displaced from the pressure chamber 7b on the high-pressure side into the additional pressure chamber 8a. Because of the deflection of the overload diaphragm 6a and the separating diaphragm 5a, the additional pressure chamber 8a and the pressure chamber 7a can absorb transfer fluid 16. This displacement of transmission fluid 16 ends as soon as the separating diaphragm 5b comes into contact with the overload diaphragm 6b on the high-pressure side. The pressure in the capillary system of the differential pressure sensor cannot subsequently increase any further. Since the overload membranes 6a, 6b and the pressure-sensitive element 13 are connected in series in terms of pressure dynamics, only a pressure which is below the critical limit value reaches the positive side of the pressure-sensitive element 13 via the connecting capillary 10a. According to the invention, as much transfer liquid 21 is transferred from the right side of the double membrane system 4b to the left side of the double membrane system 4a until no more transfer liquid 16 can be displaced on the right side of the double membrane system 4b, since the process membrane 5b is in contact with the overload membrane 6b, which is in turn rests on the base body 9 of the measuring unit 2 . The maximum pressure applied to the left-hand side of the pressure-sensitive element 13 can be defined or dimensioned via the restoring force of the overload membranes 6a, 6b (spring in the deflected state). This effectively counteracts the destruction of the pressure-sensitive element 13, usually a silicon chip.

In order to ensure that the excess pressure first deflects the overload membrane 6a before it reaches the sensitive area of the pressure chip (usually also a membrane), the hydraulic paths are routed in series. The pressure-sensitive chip 15 is only at the end of the series connection. This is supported or ensured by appropriately adapted capillary geometries, which fulfill a braking function in the direction of the pressure-sensitive chip 13 . Additionally or alternatively, upstream dynamic brakes can also be used be provided. In particular, the connecting and auxiliary capillaries 10a, 10b, 11a, 11b, 11c, 11d are suitably dimensioned in length and diameter. According to a further development of the differential pressure measuring sensor 1 according to the invention, it is considered advantageous if so-called dynamic brakes 22 are additionally or alternatively used in the connecting capillaries 10a, 10b. These delay the transmission of the pressure, in particular an overpressure PeÜL, and protect the pressure-sensitive element 13 in particular from pressure peaks occurring in the process. The dynamic brakes 18 can be sintered metal inserts. When using the differential pressure sensor 1 in the explosion-proof area, the dynamic brakes 18 are made of a non-conductive material. In this case, the dynamic brakes 18 then fulfill a dual function: delayed transmission of the pressure and explosion protection according to a required type of explosion protection.

at 3a the capillary system is filled with a transmission liquid via the converter chamber 3. The filling bores 14a, 14b are closed gas- or liquid-tight and pressure-tight with closure elements 15a, 15b. The shutter elements 15a, 15b are arranged close to the pressure-sensitive element 13. FIG. In the 3c the closure elements 15a, 15b are located on the area of the converter chamber 3 facing away from the process 3c are additionally provided after filling bores 14a, 14b on the measuring unit 2. The filling is provided here via two separate filling bores 14, 14b, which are arranged parallel to the connecting capillaries 10a, 10b and the auxiliary capillaries 11a, 11b, 11c, 11d. The filling bores 14a, 14b open into the corresponding additional pressure chambers 8a, 8b. A preferably spherical closure element 15a, 15b is provided as a pressure-tight, gas-tight or at least liquid-tight closure, which is pressed 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.

Alternatively, filling can take place via the converter chamber 3 . The filling bores 18a, 18b preferably run from the end face of the converter chamber 3 facing away from the process to the connecting capillaries 10a, 10b. However, it is also possible to route the filling bores 19a, 19b from the side surface of the converter chamber 3 to the connecting capillaries 10a, 10b. The filling bores 14a, 14b are closed in the manner already described above. Incidentally, the arrows indicate the filling direction in each case.

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 13 via the connecting capillaries 10a, 10b. 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 18 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 12 and visualizes how the individual components of the differential pressure measuring cell 12 and the current bushing 23 are arranged in the converter chamber 3 . An insulating base (eg 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 16, 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 (for example a ceramic base or a glass base), which has a thickness d≧0.7 mm, for example. Furthermore, the insulation of the silicon chip 13 and its bonding connections 24 is provided by the filling body 33 with 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 the measuring mechanism 2 and the converter chamber 3 can be implemented via insulation elements 25, preferably insulation tubes 25, adapted in or on the capillary tubes 17. 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 mechanism 2 and the converter chamber 3 takes place in the area of the capillary tubes between the corresponding connecting capillaries 10a, 10b or at the transition of the Capillary tube to measuring element 2 or to 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 area between converter chamber 3 and measuring mechanism 2 ( 5c ) or in measuring element 2 ( 5b) 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 can also be achieved by appropriate design of the dynamic brakes 18 has already been mentioned above. 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 or its components. 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 14 with the pressure-sensitive element 15 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 14, 27, which are preferably arranged 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 12, 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 14,
• 1 = (1.1): Versorgungsspannungs-Minusanschluss (Masse),
• 8 = (1.2): Versorgungsspannungs-Minusanschluss (Masse).

Wie bereits zuvor beschrieben, kann für die Masseanschluss auch ein gemeinsamer PIN 26 verwendet werden.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 14,
• 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 15
• 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 mechanism 2
• ③ Pressure supply converter chamber 3 - measuring unit 2
• ④ Pressure supply to converter chamber 3
• ⑤ Power feedthrough 23 with PIN/glazing
• ⑥ Oil cap 15
• 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 membrane, second double membrane

5a, 5b

first separation membrane, second separation membrane

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,

11c, 11d

third auxiliary capillary, fourth 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

18

dynamic brake

19

Intermediate area / 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 [0012]

Claims (16)

Differential pressure sensor (1) for determining the differential pressure of two pressures (p1, p2) with a measuring mechanism (2) and a converter chamber (3), the measuring mechanism (2) and a converter chamber (3) being separated from one another via an intermediate region (15), a coplanar double diaphragm system (4) with two double diaphragms (4a, 4b) being provided on or in an end region (14) of the measuring unit (2) facing the process and wherein a differential pressure measuring cell (12) with a pressure-sensitive element is provided in the converter chamber (3). (13), the two double diaphragms (4a, 4b) each consisting of a separating diaphragm (5a, 5b) and an overload diaphragm (6a, 6b) arranged behind the separating diaphragm (5a, 5b) in the direction of the pressure effect, with between the first separating membrane (5a) and the first overload membrane (6a) a first pressure chamber (7a) and between the first overload membrane (6a) and the base body (9) a first additional pressure chamber (8a) is formed, wherein between the second separating diaphragm (5b) and the second overload diaphragm (6b), a second pressure chamber (7b) and between the second overload diaphragm (6b) and the base body (9) a second additional pressure chamber (8b) is formed, with the first additional pressure chamber (8a) or the second additional pressure chamber (8b) is assigned a first connecting capillary (10a) or a second connecting capillary (10b), the two connecting capillaries (10a, 10b) hydraulically transmitting the pressure to the converter chamber (3), and protecting the pressure-sensitive element (13) a first auxiliary capillary (11a) or a second auxiliary capillary (11b) is assigned to the first additional pressure chamber (8a) or the second additional pressure chamber (8b) against excess pressure, the first pressure chamber (7a) or the second pressure chamber (7b ) a third auxiliary capillary (11c) and a fourth auxiliary capillary (11d) are assigned, wherein the hydraulic connections / crossings of the first auxiliary capillary (11a) with the fourth auxiliary capillary are (11d) and the second auxiliary capillary (11b) and the third auxiliary capillary (11c) is arranged in the intermediate region (14) of the measuring unit (2) and the converter chamber (3). 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 claim 1 or 2 , wherein the connecting capillaries (10a, 10b) and the auxiliary capillaries (11a, 11b, 11c, 11d) are arranged essentially parallel to the longitudinal axis (L) of the differential pressure sensor (1), and wherein the coupling capillaries (12.1, 12.2) are arranged between the auxiliary capillaries (11a , 11c; 11b, 11d) essentially perpendicular to the longitudinal axis (L) of the differential pressure sensor (1). Differential pressure sensor according to one or more of the preceding claims, wherein an intermediate module (19) is arranged in the intermediate region (19) of measuring unit (2) and converter chamber (3), and wherein the connecting and auxiliary capillaries arranged in the intermediate module (19) are (10a, 10b, 11a, 11b, 11c, 11d) and the connections/intersections of the auxiliary capillaries (11a, 11b, 11c, 11d) are preferably capillary bores. Differential pressure sensor according to one or more of the preceding claims, wherein the connection and/or auxiliary capillaries (10a, 10b, 11a, 11b, 11c, 11d) and the connections/ Crossings of the auxiliary capillaries (11a, 11b, 11c, 11d) are capillary bores and/or capillary tubes (17). Differential pressure sensor according to one or more of the preceding claims, wherein the converter chamber (3) has two connecting capillaries (10a, 10b) at its end region facing the process, which are preferably arranged parallel to one another and which are congruent with the connecting capillaries (10a, 10b) designed as capillary bores. in the intermediate module (19) and in the measuring mechanism (2). Differential pressure sensor according to one or more of Claims 1 until 6 , wherein the connecting capillaries (10a, 10b) and/or the auxiliary capillaries (11a, 11b, 11c, 11d) 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 overpressure protection before the overpressure is transmitted to the differential pressure measuring cell (12) or the pressure-sensitive element (13). Differential pressure sensor according to one or more of the preceding claims, wherein at least one filling hole (14) is provided, which is used to fill the hydraulically communicating components with a hydraulic transmission fluid (16), each filling hole (14a, 14b) after filling over a closure element (15a, 15b) is closed pressure-tight, gas-tight or at least liquid-tight. Differential pressure sensor according to one or more of the preceding claims, electrical connection pins (26) in the converter chamber (3) being 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, wherein the connecting capillaries (10a, 10b) and auxiliary capillaries (11a, 11b, 11c, 11d) are designed in such a way that they electrically insulate the converter chamber (3) from the measuring mechanism (2). differential pressure sensor claim 10 , wherein the connecting capillaries (10a, 10b) and the auxiliary capillaries (11a, 11b, 11c, 11d) are provided at least in sections with an electrical insulator (25), in particular a ceramic insulating body or an insulating glazing, and via a gas-tight connection, in particular a Soldered joint or glazing, are fixed in the corresponding bores capillary bores of the measuring mechanism (2) or the intermediate module (19) or the converter chamber (3). Differential pressure sensor according to one or more of the preceding claims, wherein the electrical insulators (25) in the converter chamber (3) and/or in the measuring unit (2) and/or in the intermediate space (19) or in the intermediate module (19) between the measuring unit (2) and converter chamber (3) are provided. 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 a 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 (pstat) 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 (dp) and the pressure-sensitive element (27) for measuring the static pressure (pstat) are stacked on top of one another or arranged next to one another in the converter chamber (3). .

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