GB2554973A

GB2554973A - Pressure Sensor

Info

Publication number: GB2554973A
Application number: GB1711263.2A
Authority: GB
Inventors: Falk Vladislav; Djordjevic Zoran; Schluter Siegmund
Original assignee: Sensata Germany GmbH
Current assignee: Sensata Germany GmbH
Priority date: 2016-07-18
Filing date: 2017-07-13
Publication date: 2018-04-18
Anticipated expiration: 2037-07-13
Also published as: GB201711263D0; GB2554973B; DE102016113209A1; DE102016113209B4

Abstract

A pressure sensor for measuring the pressure of a fluid, in particular to a high-pressure oxygen sensor, comprising a pressure measurement transducer 12 that has a pressure port 14 having a pressure passage 20 and that has a pressure measuring cell 16. Fluid is supplied to the pressure measuring cell 16 through the pressure passage 20 wherein the pressure measuring cell is fastened to the pressure port, and comprising a housing that is attached to the pressure measurement transducer. The pressure sensor is characterized in that the pressure measuring cell is manufactured from a first material and the pressure port is manufactured from a second material, with the first and second materials respectively being a copper nickel alloy. In a manufacturing process, these parts are connected together at an elevated portion 26 on the pressure port in material continuity by capacitor discharge welding.

Description

(56) Documents Cited:

EP 0336437 A2 US 3899766 A

G01L9/00 (2006.01)

WO 2012/066232 A2 (71) Applicant(s):

Sensata Germany GmbH

Potsdamer Str.14, Minden 32423, Germany, Germany (72) Inventor(s):

Vladislav Falk Zoran Djordjevic Siegmund Schliiter (58) Field of Search:

INT CL G01L

Other: EPODOC, WPI, Patent Fulltext (74) Agent and/or Address for Service:

Manitz Finsterwald Patentanwalte PartmbB Martin-Greif-Str.1, Munich, Germany, 80336, Germany (54) Title of the Invention: Pressure Sensor

Abstract Title: High pressure sensor having copper nickel alloy pressure cell and port which are welded together (57) A pressure sensor for measuring the pressure of a fluid, in particular to a high-pressure oxygen sensor, comprising a pressure measurement transducer 12 that has a pressure port 14 having a pressure passage 20 and that has a pressure measuring cell 16. Fluid is supplied to the pressure measuring cell 16 through the pressure passage 20 wherein the pressure measuring cell is fastened to the pressure port, and comprising a housing that is attached to the pressure measurement transducer. The pressure sensor is characterized in that the pressure measuring cell is manufactured from a first material and the pressure port is manufactured from a second material, with the first and second materials respectively being a copper nickel alloy. In a manufacturing process, these parts are connected together at an elevated portion 26 on the pressure port in material continuity by capacitor discharge welding.

1/2

Fiski

2/2

Fig. 4

PRESSURE SENSOR

The present invention relates to a pressure sensor for measuring the pressure of a 5 fluid, in particular to a high-pressure oxygen sensor. The pressure sensor comprises a pressure measurement transducer that has a pressure port having a pressure passage and that has a pressure measuring cell, wherein the fluid can be supplied to the pressure measuring cell through the pressure passage and wherein the pressure measuring cell is fastened to the pressure port. The pressure sensor furthermore comprises a housing that is attached to the pressure measurement transducer.

Pressure sensors for measuring the pressure of a fluid are used in different sectors and serve to convert the pressure of the fluid into a measured signal and to output the measured signal e.g. by means of an electric signal. One side of a measurement membrane of the pressure measuring cell is acted on by a fluid that is supplied via the pressure passage to the pressure measuring cell and thus to the measurement membrane for the measurement of the fluid pressure. The other side of the membrane that is remote from the fluid is exposed to a reference pressure, in particular to the hydrostatic pressure of the atmosphere surrounding the sensor. The measurement membrane is mechanically deflected on a pressure difference between its two sides. This deflection is detected and converted into the measured signal. Procedural processes and the like can then e.g. be controlled and monitored using the measured signal or the measured pressure.

Depending on the kind of fluid to be measured, the problem can occur that a material of the pressure sensor that comes into contact with the fluid is chemically changed and in particular corroded by the fluid. Such corrosion can be triggered, for example, by (pure) oxygen. The chemical change or corrosion is unwanted since the structural integrity of the pressure sensor can hereby be weakened and the service life of the pressure sensor is reduced. There is additionally the risk that the pressure sensor can suddenly no longer withstand the pressure of the fluid.

It is therefore the underlying object of the invention to provide a pressure sensor that is insensitive to corrosive fluid and that in particular also withstands high pressure.

This object is satisfied in accordance with the invention by a pressure sensor in accordance with claim 1 and in particular in that the pressure measuring cell manufactured from a first material and the pressure port is manufactured from a second material, wherein the first and second materials are each a copper nickel alloy.

Those parts of the pressure sensor that come into contact with the fluid, i.e. the pressure measuring cell and the pressure port, are therefore in particular manufactured, in particular completely in each case, from the copper nickel alloy or from the first or second material respectively. The invention exploits the recognition that a copper nickel alloy is particularly insensitive to corrosion and is therefore suitable, for example, for measuring the pressure of oxygen. Corrosion can be almost precluded by the copper nickel alloy.

Unlike e.g. for the manufacture of a pressure sensor from a steel that comprises carbon, the pressure sensor in accordance with the invention can be used particularly easily for the measurement of high-pressure oxygen since the respective copper nickel alloy at least substantially does not comprise any carbon and therefore at least substantially does not react with oxygen. The copper nickel alloy has a considerably higher combustion resistance than e.g. stainless steel. A combustion of the copper nickel alloy with the oxygen can therefore be almost precluded.

The licensing of the pressure sensor for oxygen applications can additionally be considerably simplified and accelerated by the use of the copper nickel alloy and due to the thus almost precluded reaction of oxygen.

The pressure sensor can in particular be adapted to measure a pressure of up to 260 bar, preferably of up to 300 bar, preferably of up to 370 bar, and preferably of up to 450 bar.

Advantageous embodiments and further developments of the invention can be seen from the description, from the drawings and from the dependent claims.

It is of advantage if the first and second materials are selected such that e.g. the pressure measuring cell, that typically has a smaller wall thickness than the pressure port, is produced from a more stable material than the pressure port. The pressure sensor in accordance with the invention can in this manner also withstand particularly high pressure. Manufacturing costs can in particular also be saved by the selection of the second material since the demands on the second material are smaller. It is therefore preferred if the compositions of the first and second materials differ from one another. The first material and the second material can, however, generally also be identical.

It is further preferred if at least the first material comprises aluminum, in particular if the first and second materials comprise aluminum, with the first material preferably having a higher proportion of aluminum than the second material. The strength of the respective copper nickel alloy can be increased by the addition of aluminum, wherein the strength increase is the higher - at least within a certain range - the more aluminum is added. The first material can be mechanically harder than the second material by the use of aluminum (if the second material does not comprise any aluminum) or of higher proportions of aluminum (if the second material also comprises aluminum). This is of advantage since the pressure measuring cell, in particular a measurement membrane of the pressure measuring cell, typically has a smaller wall thickness than the pressure port, but has to withstand the same pressure and the deflection of the measurement membrane should be maintained in a range required for technical measurement reasons. The property of the first material is to this extent adapted to the shape and size of the pressure measuring cell.

The first material is particularly preferably a copper nickel alloy that comprises a weight proportion of at least 60% nickel, between 25% and 35% copper, a maximum of 2.5% iron, and between 2% and 4% aluminum. Alternatively or additionally, the second material is a copper nickel alloy that comprises a weight proportion of at least 60% nickel, between 25% and 35% copper, a maximum of 3% iron, and a maximum of 1% aluminum. As already stated, the first material can have a higher strength than the second material due to the increased aluminum proportion. The first material in particular comprises between 0.35% and 0.85% titanium. The strength of the first material can be further increased by the adm ixture of titanium.

The first material is thus in particular Monel K500 and the second material is Monel 400.

The pressure measuring cell preferably comprises a measurement membrane, wherein the measurement membrane has pressure-sensitive elements at a side remote from the pressure passage. The pressure-sensitive elements can e.g. be strain gauges, in particular strain-dependent resistors, that preferably form a measurement bridge, in particular a Wheatstone bridge. The pressure-sensitive elements can, for example, be applied to the measurement membrane by means of thin film technology.

The measurement membrane is mechanically deflected on a pressure difference between the two sides of the measurement membrane. This deflection is detected by the pressure-sensitive elements. A conclusion can then be drawn on the fluid pressure from the signals of the pressure-sensitive elements.

The pressure measuring cell is particularly preferably directly connected to the pressure port with material continuity. The pressure measuring cell can, for example, be directly welded to the pressure port, e.g. by means of resistance welding and in particular by means of capacitor discharge welding. In the welding of the pressure measuring cell and the pressure port, the first and second materials are therefore welded together and form a direct connection with material continuity.

It is of advantage with the direct connection with material continuity that e.g. elastomer seals and the like can be dispensed with so that the fluid preferably only comes into contact with the first and second materials. The fluid thus does not come into contact with any material that comprises carbon.

In accordance with a further embodiment of the invention, the pressure port has an elevated portion, in particular a frustoconical elevated portion, to which the pressure measuring cell is fastened. The elevated portion can be arranged in the region of a plane of the surface of the pressure port. The pressure port can be welded to the pressure measuring cell in the region of the frustoconical elevated portion. The frustoconical elevated portion can be arranged around the pressure passage, i.e. the pressure passage is located centrally at the middle of the elevated portion.

The pressure measuring cell is preferably of hollow cylindrical shape at least regionally so that an edge of an end face of the pressure measuring cell can contact the elevated portion and in particular has a circular connection line with the elevated portion. The contact surface (i.e. the weld geometry) at which the pressure measuring cell and the pressure port touch before welding is very small due to this linear connection between the truncated cone and the pressure measuring cell. Due to the small contact surface this linear connection is particularly suitable for resistance welding and in particular for capacitor discharge welding which require high current densities. On the welding of the pressure measuring cell and the pressure port, the first and/or second material can then be liquefied for a brief time and the connection with material continuity can thus be established. After the welding the contact surface between the pressure measuring cell and the pressure port can be considerably increased.

The pressure measuring cell can in particular be manufactured as a turned part and can comprise an inner bore (i.e. a cut-out) that connects the pressure passage to the measurement membrane. The edge formed by the inner bore and the end face can contact the elevated portion of the pressure port before the welding.

The pressure passage can preferably extend in a straight line through the pressure port. The pressure passage can thus in particular define an axis. The surface of the frustoconical elevated portion can include an angle with the axis that preferably amounts to 75° +/-10°.

In accordance with a further embodiment of the invention, a flow restrictor is arranged in the pressure passage that narrows the pressure passage and is in particular formed from brass. The flow restrictor serves to reduce the throughput of the fluid and thus the exiting quantity of the fluid when e.g. there is a leak in the pressure measuring cell. The flow restrictor in particular has a cylindrical shape and comprises a passage hole. The passage hole can e.g. have a diameter of approximately 0.2 mm at its narrowest point. Alternatively to the design from brass, the flow restrictor can also be manufactured from the first or second materials. The diameter of the passage hole can be of different sizes depending on the application.

In accordance with a further embodiment of the invention, the housing is formed from a third material, preferably from a stainless steel, in particular from an austenitic stainless steel. The third material can in particular be a non-rust austenitic steel (stainless steel 1.4031). Since the housing does not come into contact with the fluid, it is not necessary that the housing is manufactured from the first or second materials and thus in particular does not comprise any carbon.

The pressure port preferably comprises a chamfer, in particular of ring shape, at which the pressure port is connected, and in particular welded, to the pressure port with material continuity. The pressure port can, for example, have a peripheral chamfer, whereby a peripheral contact surface is provided with the housing in the form of a contact line that is in turn particularly suitable for welding by means of resistance welding, in particular capacitor discharge welding. The chamfer can have a peripheral chamfered surface that includes an angle of 45° +/-10° with the axis defined by the pressure passage. A peripheral right-angled edge of the housing can contact the chamfer before the welding, with the material being welded to the pressure port in the region of the right-angled edge.

The first and second materials as well as the second and third materials can therefore be welded together in the pressure sensor. A mechanically very stable pressure sensor is produced due to the weld connections, with that material respectively simultaneously being used for the pressure measuring cell, for the pressure port and for the housing that is best suited for the respective component.

A circuit board having evaluation electronics is preferably arranged at the pressure port, with the circuit board comprising a recess, in particular a circular recess, into which the pressure measuring cell projects. The circuit board preferably evaluates the pressure-sensitive elements and outputs a pressure signal (measured signal). The pressure signal can in particular be a digital signal.

The circuit board preferably does not contact the pressure measuring cell due to the recess. A force coupling from the circuit board into the pressure measuring cell can be suppressed in this manner, whereby measurement artifacts can be avoided. The circuit board is preferably electrically connected to the pressure measuring cell by means of bond wires and bond connections. To simplify the manufacture of the bond connections, the pressure measuring cell can project so far into the recess that the measurement membrane of the pressure measuring cell is approximately arranged in a plane with the circuit board.

A space defined between the pressure port and the circuit board and/or a space bounded by the housing and the circuit board are likewise preferably at least regionally filled with a first compound. The first compound can fix the circuit board and can also protect the bond wires and the evaluation electronics from mechanical damage.

A space bounded by the housing and the first compound is further preferably at least regionally filled with a second compound, with the second compound preferably being harder than the first compound. The second compound, that provides greater mechanical protection than the first compound due to its higher hardness, can therefore be provided adjacent to the first compound. Due to the smaller hardness of the first compound, the first compound can be softer and can thus introduce fewer forces into the pressure measuring cell, whereby measuring artifacts can again be suppressed.

The outer shape of the pressure sensor is preferably of an at least substantially rotationally symmetrical design, with a center of the pressure passage, i.e. the above-mentioned axis, forming the axis of rotation. The pressure port and/or the pressure measuring cell can preferably be rotationally symmetrical.

A further subject of the invention is a method of manufacturing a pressure sensor in which an elevated portion, in particular in the form of a truncated cone, is formed at a pressure port;

a pressure measuring cell is placed onto the elevated portion; and the pressure measuring cell is connected with material continuity to the elevated portion, in particular by means of resistance welding and preferably by means of capacitor discharge welding, with the pressure measuring cell being formed from a first material and the pressure port being formed from a second material, with the first and second materials preferably each being a copper nickel alloy.

As already stated, a small contact surface which is particularly well suited for capacitor discharge welding can be created between the pressure measuring cell and the pressure port by the elevated portion. The conditions for capacitor discharge welding can be calculated, for example, by means if a finite element simulation (FEM simulation). A sensitivity of the measurement membrane can additionally also be determined by means of the simulation.

After the welding of the pressure measuring cell and the pressure port, the housing and the pressure port can subsequently be welded together in the aboveexplained manner.

In accordance with a further development of the method, the pressure passage is first cleaned after the welding of the pressure port and the pressure measuring cell. The flow restrictor is subsequently inserted and in particular pressed into the pressure passage.

The purity of the surfaces contacting medium can preferably be ensured by cleaning the pressure passage in accordance with ISO 15001. All the surfaces of the pressure measuring cell coming into contact with the fluid can thus also be cleaned like the pressure passage.

Contaminants of the pressure passage, e.g. residues of lubricating oil, and thus in particular contaminants comprising carbon, can be removed from the pressure passage by the cleaning step. For this reason, no further special measures accordingly have to be taken afterward for the use of the pressure sensor for highpressure oxygen measurement.

In another respect, the statements made on the pressure sensor in accordance with the invention apply accordingly to the method in accordance with the invention, in particular with respect to advantages and preferred embodiments and aspects.

The invention will be described in the following purely by way of example with reference to the drawings. There are shown:

Fig. 1 a pressure sensor in accordance with the invention in a perspective sectional view,

Fig. 2 a pressure port of the pressure sensor in accordance with Fig. 1 in a perspective sectional view;

Fig. 3 a pressure measuring cell of the pressure sensor in accordance with

Fig. 1 in a perspective sectional view; and

Fig. 4 the pressure sensor in accordance with Fig. 1 in a perspective sectional view, the pressure sensor being filled with a first compound and with a second compound.

Fig. 1 shows a pressure sensor 10 that is in particular suitable for high-pressure oxygen measurement. The pressure sensor 10 comprises a pressure measurement transducer 12 that has a pressure port 14 and a pressure measuring cell 16. The pressure port 14 comprises a thread 18 by which the pressure sensor 10 can e.g. be screwed to a pressure line (not shown).

A pressure passage 20 that supplies a fluid provided from the pressure line to the pressure measuring cell 16 extends through the pressure port 14. The pressure measuring cell 16 comprises a cut-out 22 in its interior that is bounded by a measurement membrane 24. The pressure passage 20 merges into the cut-out 22 so that fluid flowing through the pressure passage 20 can arrive at the measurement membrane 24. The measurement membrane 24 can be deformed by the pressure of the fluid.

To connect the pressure measuring cell 16 to the pressure port 14, the pressure port 14 comprises a frustoconical elevated portion 26 that is shown in more detail in Fig. 2. The pressure passage 20 is arranged centrally in the frustoconical elevated portion 26. The pressure measuring cell 16 is placed onto the frustoconical elevated portion 26.

The pressure measuring cell 16 is shown in more detail in Fig. 3, with it being visible from Fig. 3 that pressure-sensitive elements 28 are attached to the measurement membrane 24. The pressure measuring cell 16 has a hollow cylindrical shape regionally, with the cut-out 22 being arranged centrally in the hollow cylinder and being designed as an inner bore. An end side - a lower end side in Fig. 3 - of the pressure measuring cell 16 has a planar surface that is interrupted by the cut-out 22. A right-angled edge 30 is formed by the cut-out 22.

The right-angled edge 30 is seated on the frustoconical elevated portion 26 as is shown in Fig. 1. A capacitor discharge welding is used for the connection with material continuity of the pressure measuring cell 16 and the pressure port 14, with the right-angled edge 30 initially only forming a linear contact surface with the frustoconical elevated portion 26 prior to welding. Very high current densities can be generated in this contact surface, which results in a liquefaction of the material of the pressure measuring cell 16 and of the pressure port 14, whereby a welding is possible in a simple manner.

The pressure port 14 is manufactured from Monel 400, whereas the pressure measuring cell 16 is produced from Monel K500. Monel K500 has a greater hardness so that this material is particularly suited for the pressure measuring cell 16 since the pressure measuring cell 16 has smaller wall thicknesses than the pressure port 12.

A circuit board 32 lies on the pressure port 14. More precisely, the circuit board 32 lies on a contact surface 34. The contact surface 34 is shown in Fig. 2. The circuit board 32 is connected to the contact surface 34 by means of an adhesive that is hardened under the effect of heat.

The circuit board 32 has a central circular recess 36 that is shown in Fig. 1. The pressure measuring cell 16 projects into the central circular recess 36. The pressure measuring cell 16 is electrically connected to the circuit board 32 by means of bond wires (not shown). Measured data determined by the circuit board 32 or by the evaluation electronics are output by means of a data and supply cable 38. The data and supply cable 38 is electrically coupled to the circuit board 32 by a JST (Japan Solderless Terminal) connector 40.

A housing 42 is welded to the pressure port 14. The housing 42 is manufactured from a stainless steel and has a hexagonal outer shape regionally. The hexagonal shape can serve as a screw-in aid for the thread 18.

The housing 42 is placed against a chamfered surface 44 of the pressure port 14 for welding to the pressure port 14 (Fig. 2). An edge of the housing 42 then contacts the chamfered surface 44 so that in turn a very small contact surface results that makes possible a welding of the housing 42 and the pressure port 14 in a simple manner by means of capacitor discharge welding.

The outer shape of the pressure sensor 10 is of at least substantially a rotationally symmetrical design, with a center of the pressure passage forming the rotational axis.

After the welding of the housing 42 and the pressure port 14, a space bounded by the circuit board 32 and the pressure port 14 and a space bounded by the circuit board 32 and the housing 42 are filled with a first compound 46 The compound 46 is shown in Fig. 4. A second compound 48 that terminates flush with the housing

42 is subsequently applied to the first compound 46. The second compound 48 has a greater hardness than the first compound 46. The compounds can respectively be a compound of a silicone.

Finally in the production of the pressure sensor 10, the pressure passage 20 and the interior of the pressure measuring cell 16 (i.e. the cut-out 22) are cleaned and a flow restrictor 50 composed of brass is pressed into the pressure passage 20.

The pressure sensor 10 is thus ready for the high-pressure oxygen measurement, with the fluid (i.e. the oxygen) not coming into contact with components of the pressure sensor 10 that comprise carbon due to the use of Monel for the pressure measuring sensor 16 and for the pressure port 14.

Reference numeral list

	10	pressure sensor
	12	pressure measurement transducer
5	14	pressure port
	16	pressure measuring cell
	18	thread
	20	pressure passage
	22	cut-out
10	24	measurement membrane
	26	frustoconical elevated portion
	28	pressure-sensitive element
	30	right-angled edge
	32	circuit board
15	34	contact surface
	36	recess
	38	data and supply cable
	40	JST connector
	42	housing
20	44	chamfered surface
	46	first compound
	48	second compound
	50	flow restrictor

Claims

Claims

1. A pressure sensor (10) for measuring the pressure of a fluid, the pressure sensor (10) comprising:

a pressure measurement transducer (12), the pressure measurement transducer (12) having a pressure port (14), the pressure port (14) having a

10 pressure passage (20) and the pressure measurement transducer (12) further having a pressure measuring cell (16), with the fluid being able to be supplied to the pressure measuring cell (16) through the pressure passage (20), and with the pressure measuring cell (16) being fastened to the pressure port (14); and

15 a housing (42) that is attached to the pressure measurement transducer (12), wherein the pressure measuring cell (16) is manufactured from a first material and the pressure port (14) is manufactured from a second material, with the first and second materials each being a copper nickel alloy.
2. A pressure sensor (10) in accordance with claim 1, wherein the pressure sensor is a high-pressure oxygen sensor.

A pressure sensor (10) in accordance with claim 1 or claim 2, wherein the compositions of the first and second materials differ from one another.
4. A pressure sensor (10) in accordance with at least one of the preceding claims, wherein at least the first material comprises aluminum.
5 5. A pressure sensor (10) in accordance with claim 4, wherein the first and second materials comprise aluminum.
6. A pressure sensor (10) in accordance with claim 4 or claim 5, wherein the first material has a higher proportion of aluminum than the second material.
7. A pressure sensor (10) in accordance with at least one of the preceding claims, wherein the first material is a copper nickel alloy that comprises a weight proportion of at least 60% nickel, between 25% and 35% copper, a

15 maximum of 2.5% iron, and between 2% and 4% aluminum.
8. A pressure sensor (10) in accordance with at least one of the preceding claims, wherein the second material is a copper nickel alloy that comprises a weight

20 proportion of at least 60% nickel, between 25% and 35% copper, a maximum of 3% iron, and a maximum of 1% aluminum.
9. A pressure sensor (10) in accordance with at least one of the preceding claims,

25 wherein the pressure measuring cell (16) comprises a measurement membrane (24), with the measurement membrane (24) having pressuresensitive elements (28) at a side remote from the pressure passage (20).
10. A pressure sensor (10) in accordance with at least one of the preceding

30 claims, wherein the pressure measuring cell (16) is directly connected to the pressure port (14) with material continuity.
11. A pressure sensor (10) in accordance with at least one of the preceding

5 claims, wherein the pressure port (14) has an elevated portion (26) to which the pressure measuring cell (16) is fastened.
12. A pressure sensor (10) in accordance with claim 11,

10 wherein the elevated portion is a frustoconical elevated portion (26).
13. A pressure sensor (10) in accordance with at least one of the preceding claims, wherein a flow restrictor (50) that narrows the pressure passage (20) is 15 arranged in the pressure passage (20).
14. A pressure sensor (10) in accordance with claim 13, wherein the flow restrictor is formed from brass.

20 15. A pressure sensor (10) in accordance with at least one of the preceding claims, wherein the housing (42) is formed from a third material.

16. A pressure sensor (10) in accordance with claim 15,

25 wherein the housing (42) is formed from a stainless steel.

17. A pressure sensor (10) in accordance with claim 15 or claim 16, wherein the housing (42) is formed from an austenitic stainless steel.

18. A pressure sensor (10) in accordance with at least one of the preceding claims, wherein the pressure port (14) comprises a chamfer at which the housing (42) is connected to the pressure port (14).

19. A pressure sensor (10) in accordance with claim 18, wherein the chamfer is a ring-shaped chamfer (44).

20. A pressure sensor (10) in accordance with claim 18 or claim 19,

10 wherein the housing (4) is welded to the pressure port (14) with material continuity at the chamfer.

21. A pressure sensor (10) in accordance with at least one of the preceding claims,
15 wherein a circuit board (32) having evaluation electronics is arranged at the pressure port (14), with the circuit board (32) comprising a recess (36) into which the pressure measuring cell (16) projects.

22. A pressure sensor (10) in accordance with claim 21,
20 wherein a space defined between the pressure port (14) and the circuit board (32) and/or a space bounded by the housing (42) and the circuit board (32) is/are filled with a first compound (46).
23. A pressure sensor (10) in accordance with claim 22,

25 wherein a space bounded by the housing (42) and the first compound (46) is filled with a second compound (48).
24. A pressure sensor (10) in accordance with claim 23, wherein the second compound (48) is harder than the first compound (46).
25. A method of manufacturing a pressure sensor (10), the method comprising the steps of:

- forming an elevated portion (
26) at a pressure port (14);

- placing a pressure measuring cell (16) onto the elevated portion (26); and

5 - connecting the pressure measuring cell (16) with material continuity to the elevated portion (26);

wherein the pressure measuring cell (16) is formed from a first material and the pressure port (14) is formed from a second material.

10 26. A method in accordance with claim 25, wherein the first and second materials are each a copper nickel alloy.
27. A method in accordance with claim 25 or claim 26, wherein the elevated portion (26) is formed in the form of a truncated cone 15 at the pressure port (14).
28. A method in accordance with at least one of the claims 25 to 27, wherein the pressure measuring cell (16) is connected with material continuity to the elevated portion (26) by means of capacitor discharge

20 welding.
29. A method in accordance with at least one of the claims 25 to 28, wherein a pressure passage (20) of the pressure sensor (10) is first cleaned and a flow restrictor (50) is subsequently inserted into the pressure passage

25 (20).

Intellectual

Property

Office

Application No: GB1711263.2 Examiner: Eamonn Quirk