Method for manufacturing a measuring tube , flowmeter, computer program product and use of a flowmeter

The present invention relates to a method for manufacturing a measuring tube . The present invention also relates to a flowmeter which comprises a measuring tube that is manufactured accordingly . Furthermore , the invention relates to a computer program product that is configured to simulate the operational behavior of such a flowmeter . In addition to that , the present invention pertains to the use of such a flowmeter in a piping system in production process for a food or a beverage .

The patent application JPH- 0419515 A discloses a measuring tube for a flowmeter that is made of an alumina-based ceramic . A platinum rod is inserted into drilled hole in a wall of the measuring tube . The platinum rod is coated with a silicon oxide to provide for an improved adhesion to the wall of the measuring tube .

In addition to that , JPS- 6242013 A discloses a measuring tube for a flowmeter that comprises a platinum rod that is inserted through the wall of the measuring tube . At an inner end, the platinum rod is tipped with a conductive electrode . The conductive electrode may be attached to the platinum rod through brazing or a press- fit .

In several applications , precise flow measurements are required for optimal processes . Besides precision, reliability, cost-ef fectiveness and ease of manufacturing are also typical requirements for flowmeters . Among other factors , it is aspired to reduce the use of expensive materials like noble metals . Thus , it is an obj ect of the present invention to provide a flowmeter that shows an improvement in at least one of the outlined aspects . That obj ect is achieved by a manufacturing method according to the present invention . The method serves for manufacturing a measuring tube that is configured to be coupled with excitation means of a flowmeter and through which a fluid may be guided . A flow speed of the fluid is measured as it passes through a pipe section of the measuring tube . To that end, at least one measuring electrode is accommodated in the pipe section . The method for manufacturing the measuring tube comprises a first step, in which a tubular ceramic green body is provided that in turn is to form the pipe section . The tubular ceramic green body is used as a blank for the pipe section and may be cured by firing . Furthermore , a wire is provided in the first step that is to be part of the measuring electrode . The method also comprises a second step during which the wire is fastened into a wall of the tubular ceramic green body . In an assembled state , the wire extends into an at least partially radial direction . The radial direction is to be construed as being substantially perpendicular to a main central axis of the tubular ceramic green body . In other word, such an at least partially radial direction encompasses a radial component di f ferent from zero . For example , the wire may extend straight into a radial direction or may extend through the wall of the tubular ceramic green body in a sloping manner .

The method according to the invention further encompasses a third step in which the tubular ceramic green body is fired to form the pipe section . During the third step, an inner end of the wire is machined to be flush with an adj acent inner face of the wall of the tubular ceramic green body or the pipe section respectively . The machining of the wire may entail all kinds of processing the wire to make it flush with the inner face , e . g . cutting, milling, grinding and/or honing . Either the machining of the inner end of the wire or the firing of the tubular ceramic green body may be performed first in the third step . In addition to that the method according to the invention comprises a fourth step . During the fourth step, an electrode head is connected to the inner end of the wire . Once connected, the electrode head and the wire are part of the measuring electrode . The electrode head in configured to provide an enlarge receiving area on the inner face of the pipe section . The bigger the receiving area is , the more sensitive the electrode head is for capturing a physical quantity that characteri zes the flow speed of the fluid . Such a physical quantity may be an electrical quantity like voltage , current and/or an impedance . The electrode head is connected to the inner end of the wire to form an electrically conductive connection between them .

According to the invention, the fourth step is performed as an additive manufacturing step . Thus , the electrode head is provided as an unformed electrically conductive material that is applied to an area of the inner face adj acent or around the inner end of the wire . In the additive manufacturing step, the electrode head is produced as at least one layer of the electrically conductive material that is configured to electrically connect to the inner end of the wire . Being formed in an additive manufacturing step, the electrode head may have a reduced thickness . That allows for enhanced the area of the electrode head while using a reduced amount of electrically conductive material . The enhanced area of the electrode head improves its measurement sensitivity . Since that enhanced sensitivity is achieved with a reduced amount of electrically conductive material , even materials like noble metals or materials enriched with conductive nano particles may be used in a cost-ef ficient manner . Among others , the invention is based on the finding that ceramic material as in the pipe section of fer suf ficient adhesion for electrically conductive materials applied through additive manufacturing . Furthermore , the invention is also based on the finding that there is a minimi zed contact resistance between the inner end of the wire and the electrically conductive material when it is applied through additive manufacturing . Still further, the method according to the present invention omits the number of interfaces between di f ferent materials to a minimum, thus enhancing the leak tightness of the measuring tube in the vicinity of the wire and/or the electrode head .

In an embodiment of the invention, the electrode head may be substantially made of metal , particularly platinum, gold, silver, nickel , tungsten, copper or an alloy comprises at least one of those metals . Such materials of fer an increased measurement sensitivity for the electrode head . The material of the electrode , especially the metal or the alloy, may be chosen to provide a surface with a desired surface energy and/or wetting energy . The materials outlined above of fer a wide spectrum of possible surface energies . Furthermore , the electrode may be coated with glass frit , which allows for adj usting a surface tension of the electrode . At the same time , such materials may be precisely applied through additive manufacturing . As the claimed method allows for manufacturing the electrode head with a reduced amount of material , the metals mentioned above may be used in a cost-ef ficient manner . By virtue of the claimed method, electrode heads from expensive materials like platinum or gold become a more practical choice in a wide array of applications . Furthermore , measuring tubes with an increased number of electrode heads and corresponding wires become feasible in a cost-ef ficient way . In turn, having more electrode heads in a measuring tube allows for implementing more precise flow measurement concepts and/or additional functionalities in a flowmeter . Additionally, the wire and the electrode head may be made from the same metal . In another embodiment of the present method, the electrode head may comprise graphene particles or a carbon nanotube material . Graphene particles and carbon nanotubes of fer an increased electrical conductivity and may be easily processed in additive manufacturing steps . For example , graphene particles or carbon nanotube materials may be used to enrich a carrier material that is applied through an additive manufacturing step .

Moreover, the additive manufacturing step of the claimed method may comprise at least a trans fer printing step, a screen-printing step, a 3D-print step, a laser sintering step, a material j etting step, e . g . with inks and thermoplastic feedstocks , a cold-spraying step and/or a directed- energy deposition step . These additive manufacturing steps allow for processing metals and attaching them in layers on the inner face of the pipe section . Furthermore , an electrode head manufactured by one of these methods of fers a suf ficient structural strength and robustness against chemically aggressive fluids . Therefore , electrode heads manufactured according to the claimed invention will not dissolve or crumble into the fluid for an extended period . Therefore , the performance of such electrode heads persists over an extended period, too . The present method provides a measuring tube that also has an extended useful li fetime .

In a further embodiment of the invention the tubular ceramic green body shrinks during the third step and fits the wire . The shrinkage in the vicinity of the wire provides for a tight sealing . Such a sealing is durable and substantially insusceptible to failure , for example through material fatigue . Furthermore , the wire may be inserted into a bore in the wall of the tubular ceramic green body that is drilled with an increased margin of tolerance . Due to the shrinking of the tubular ceramic green body in the vicinity of the wire , imperfections in the precision of the bore are automatically compensated for . Thus , at least parts of the claimed method may be performed with simple and cost-ef ficient tools , especially the third step . Furthermore , the sealing provided in the third step may be a sealing that is configured to pass a Helium leak test .

Still further, the wire may be accommodated in a ceramic sleeve during the second step . In the second step, the ceramic sleeve may be in a green state or at least partly fired . The ceramic sleeve serves as a bushing that separates the wire from the wall of the tubular ceramic green body . The ceramic sleeve may be fitted to the wire to provide for a tight sealing . The sealing between the wire and the ceramic sleeve may be achieved through a variety of processes which may be chosen independent from the material properties of the tubular ceramic green body . That allows for choosing virtually any fitting method that is particularly suitable to provide for a tight sealing between the wire and the ceramic sleeve . For example , the ceramic sleeve and the wire may be fired to be partly cured . In addition to that , such a sealing may be easily inspected or tested during a manufacturing process . Thus , manufacturing errors may be detected at an early stage . The ceramic sleeve may be attached to the tubular ceramic green body during the third step, especially during the firing . Altogether, the claimed method provides for an improved, more reliable and durable sealing .

In another embodiment of the invention, the tubular ceramic green body is substantially made of a food-safe material , especially alumina, zirconia or magnesium oxide . More particularly, the tubular ceramic body may be made of yttria stabili zed zirconia, briefly called YSZ , zirconia reinforced alu- minum-oxide , also known as ZTA, or magnesium-oxide stabili zed zirconia, briefly PSZ . These materials are almost chemically inert to ingredients in drugs , foods or beverages and persist extended exposure to such substances . In addition to that , green alumina or zirconia based ceramics may be machined easily, thus forming pipe sections with precisely-shaped inner faces . That allows for an exact flow measurement . Magnesium oxide and magnesium-oxide reinforced aluminum-oxide of fer increased stability, zirconia reinforced aluminum-oxide of fers an enhanced surface quality . Altogether, the claimed method provides a pipe section for a precise flowmeter that is suitable to be used in a manufacturing process for a drug, a food or a beverage .

The claimed method may also comprise that the wire and/or the ceramic sleeve are fitted into the wall of the tubular ceramic green body or the pipe section with ceramic glazing and/or ceramic slurry . Ceramic glazing and ceramic slurry are pastelike substances that may be applied to the interface where the ceramic sleeve or the wire j oins the tubular ceramic green body or the pipe section . The ceramic glazing or the ceramic slurry allows for creating an additional sealing on the outer face of the tubular ceramic green body or the pipe section . Sealing an interface with ceramic glazing or ceramic slurry is a process-capable method for attaching and sealing two ceramic components to each other . Therefore , the claimed method may be integrated into an existing manufacturing process in a quick manner . Glazing materials have lower melting points than alumina slurry and allows for simpli fied manufacturing and reducing energy consumption in the manufacturing process . Additionally or alternatively, the wire may be fitted into the wall of the tubular ceramic green body or the pipe section with a metallic braze . The metallic braze may be applied during a separate brazing step .

In the third step of the claimed method, a portion of the inner face of the pipe section adj acent or around the inner end of the wire may be machined to form a recess . The recess is also part of the inner face and is configured to accommodate the electrode head that is made in the fourth step . The recess may have a depth, i . e . dimensions perpendicular to the wall of the pipe section, substantially identical to the thickness of the electrode head . Thus , the electrode head may be flush with the inner face of the pipe section that surrounds the recess . Such a configuration prevents the fluid from peeling the electrode of f the inner face . The recess may be formed when the wire is machined to be flush with the inner face of the tubular ceramic green body or the pipe section . In addition to that , the recess may be machined to have a selectable surface roughness . The surface roughness may be selected by choosing an appropriate tool for machining the recess . The surface roughness in the recess may be adj usted to form a stronger bond between the electrode head and the pipe section . All that increases the robustness and durability of the electrode head as manufactured according to the claimed method . In another embodiment of the invention, the electrode head provided in the fourth step may have a thickness of substantially 0 . 1 pm to 50 pm, preferably 0 . 5 pm to 45 pm, more preferably 5 pm to 30 pm . Layers of such thicknesses may be precisely manufactured through a variety of additive manufacturing steps , including trans fer printing . At the same time , they of fer suf ficient stability and do not dissolve or crumble when the fluid flows over their surface .

Furthermore , the electrode head may have an adj ustable outline . The outline may be adj usted by a user input or a set of datapoints that is utili zed to control a tool that applies the electrically conductive material to the inner face of the pipe section . Therefore , the outline of the electrode head may be configured to be optimi zed to serve as a receiving antenna for the physical quantities it is to capture during operation of the flowmeter . The electrode head may have any conceivable outline that is geometrically possible on the inner face of the pipe section . For example , the electrode head may have a meandering outline , or two di f ferent electrode heads may have intertwined or interlocking outlines . The claimed method allows for exploiting the knowledge of antenna theory to form optimi zed electrode heads that of fer an increased measuring sensitivity . Particularly, the electrode may be configured to detect high frequency modulations in a magnetic field in the measuring tube , which allows for detecting density fluctuations in the fluid . That allows for detecting multiphase flow, which may comprise solid impurities or inhomogeneous mixtures . Thus , the claimed method also enhances the capabilities of measuring tubes .

Moreover, the obj ect described above is also achieved by a measuring tube according to the present invention . The measuring tube is configured to measure a flow of fluid through a piping system . To that end, the measuring tube is configured to measure the flow speed of the fluid as it passes through it . In an assembled state , the flowmeter with the measuring tube is installed in line with the piping system . The measur- ing tube also comprises at least one measuring electrode that is accommodated in a wall of a pipe section of the measuring tube . The measuring electrode is configured to capture a physical quantity that is characteristic for the flow speed of the fluid . Furthermore , the measuring tube is equipped with at least one excitation means that is configured to emit a measurement pulse that af fects the physical quantity that is to be captured . According to the present invention, the measuring tube is manufactured through a method pursuant to at least one of embodiments outlined above . Such a measuring tube may use little expensive materials like noble metals for their measuring electrodes and are cost-ef ficient . Additionally, that measuring tube is suitable to be used in foodprocessing or drug-processing applications . Still further, such a measuring tube may be optimi zed in terms of measuring sensitivity and precision . Thus , the claimed measuring tube is a mani festation of the benefits yielded from its manufacturing process .

The obj ect described above may also be obtained by a flowmeter according to the present invention . The flowmeter is configured to measure a flow, i . e . a flow speed, of a fluid through a piping system and comprises a measuring tube . The flowmeter further comprises an evaluation unit that is coupled to the measuring tube . The evaluation unit is configured to receive measurement signals from the at least one measuring electrode that is part of the measuring tube . In addition to that , the evaluation unit is configured to evaluate the measurement signals and to calculate the flow speed of the fluid from it . According to the present invention, the flowmeter utili zes a measuring tube according to one of the embodiments outlined above .

Moreover, the obj ect of the invention is also achieved by a computer program product that is described in the following . The computer program product according to the invention is configured to simulate an operational behavior of a flowmeter . To that end, the computer program product may encompass a replication of at least the measuring tube used in the flowmeter, i . e . a digital description of the flowmeter that mirrors its dimensions , including its components . The operational behavior may comprise the flow readings generated by the flowmeter depending on the flow of fluid present in a piping system to which the flowmeter may be attached . In addition to that , the operational behavior may comprise an electromagnetic behavior of the fluid in response to a measurement flow depending on its present flow speed . The claimed computer program product is configured to emulate the functionality of the flowmeter it simulates . Pursuant to the invention, the simulated flowmeter comprises a measuring tube according to one of the embodiments described above .

The computer program product pursuant to the invention may comprise a calculation model that mirrors and/or tracks the functionality of the flowmeter in an abstraction that is independent of the dimensions or the shape of the components of the flowmeter, for example as a set of equations . Furthermore , the computer program product may encompass a physics module , in which the flowmeter is modelled . That model in the physics module may be configured to mirror the electromagnetic characteristics of the electrode head, the wire , and/or the fluid . Furthermore , the model in the physics module may be configured to emulate the communication behavior of the flowmeter, i . e . how it generates measurement signals that may be transmitted to an evaluation unit . The operational behavior of the flowmeter may be emulated under adj ustable operating conditions . The operating conditions may comprise the dimensions of the piping system, the temperature , the flow speed, the viscosity and/or the electrical conductivity of the fluid, an indication of the material of the electrode head and/or the fluid, the characteristics of a measurement pulse , a surface roughness of the inner face of the measuring tube or the electrode heads , and/or parameters pertaining to the vorticity of the fluid . To that end, the computer program product may encompass a data interface through which such data may be input by a user and/or other simulation programs . Moreover, the claimed computer program product may comprise a data interface for outputting it simulation results , for example to a user and/or other simulation programs .

By virtue of the claimed computer program product , defunct or degrading components of the flowmeter may be detected, such as electrode heads . To that end, the computer program product may be configured to check measuring values of the flowmeter, i . e . of the physically existent flowmeter, with measuring results of its replication inside the computer program product . Such physical and virtual measuring results may be crosschecked for plausibility . For example , a commencing degradation of a component may be compared to its spent service time . Such a comparison may show i f the detected degradation is commensurate with the spent service time of that component . Among others , the present invention is based on the surprising finding that the electromagnetic behavior of the electrode heads may be chosen to be easy to calculate . The electrode heads may have an outline to resemble an antenna whose receiving behavior may be calculated in a simpli fied manner, i . e . with a minimi zed amount of finite element calculations , substantially or even purely algebraically . Thus , the claimed computer program product of fers an exact simulation of the underlying flowmeter and requires only a reduced amount of computing power . The claimed computer program product may readily be implemented into a superordinate control unit that supervises the operation of such a flowmeter .

The computer program product according to the present invention may be embodied as a so-called digital twin, as described in US 2017 /286572 Al , for example . The contents of US 2017 /286572 Al are hereby incorporated into the present application and to be considered as disclosed with it . The claimed computer program may be embodied as a monolithic program that is runnable on a single hardware platform . Alternatively, the claimed computer program product may be embodied as a modular program with single programs being runnable on separate hardware platforms . These single programs are con- figured to interact with each other through a suitable data- link, e . g . an ethernet connection, an internet connection and/or a wireless connection like a cellphone network in order to accomplish their envisaged functionality . Particularly, the claimed computer program product may be configured to be runnable on a computer cloud .

In a preferred embodiment of the invention, the computer program product is runnable on the evaluation unit of the flowmeter and is configured to detect a defunct and/or degrading component of the flowmeter during its operation . Since the computer program product only requires a reduced amount of computing power, it may be operated as a real-time supervision of the underlying physical flowmeter . Consequently, the claimed computer program product may serve for real-time supervision of the corresponding flowmeter .

In addition to that , the obj ect of the invention is also achieved by a method for monitoring the operational behavior of a flowmeter . The method comprises a first step in which a computer program product is run that encompasses a replication of the flowmeter that is to be monitored . The computer program product is being provided with data about the present flow, for example an indication of fluid, its viscosity, its electrical conductivity and/or its flow speed . Furthermore , simulated measurement signals are generated by the computer program product . According to the present invention, the computer program product applied in the monitoring method is a computer program product according to one of the embodiments described above . The computer program product may be configured to take into account the spent service li fe of the simulated flowmeter in order to compensate for commensurate degradation of components . In a second step, measurement data from the flowmeter are captured . In a third step, the simulated measurement data and the corresponding captured measurement data compared to each other . A di f ference is between at least one simulated measurement signal and the corresponding captured measurement signal is determined . That di f fer- ence is compared to a warning threshold that represents the degree of acceptable deterioration of the flowmeter . I f the di f ference exceeds the warning threshold in terms of amount , a warning will be output to a user and/or a superordinate control unit . The computer program product may be coupled to a neural network that is configured to determine a cause of the di f ference between the simulated measurement signal and the captured measurement signal . For example , a defunct component may be identi fied by the neural network . Alternatively or additionally, the computer program product may be configured to adapt an existing measuring tube to a di f ferent fluid which may show di f ferent multiphase flow characteristics . For example , the computer program product may be used to determine optimi zed parameters for detecting multiphase flow in fluids with di f ferently si zed solid impurities . The computer program product may comprise a set of instructions , executable by a processor that implements at least one of the functionalities outlined above .

Moreover, the obj ect of the invention is also achieved by a use of a flowmeter in a piping system that guides a fluid . The fluid comprises at least one ingredient or a precursor to an ingredient of a drug, a food or a beverage . The drug, food or beverage may be one that is fit for human or animal consumption . According to the invention, the flowmeter is embodied pursuant to one of the embodiments described above . Such a flowmeter provides improved measurement characteristics , enhanced hygiene and cost-ef ficiency . Particularly, the flowmeter comprises at least one electrode head, that is stable when exposed to the fluid for an extended period . That stability encompasses chemical and mechanical stability . The electrode head will not crumble or dissolve into the fluid for an extended period of time . Since the claimed flowmeter is also cost-ef ficient to manufacture , it allows for using more flowmeters to monitor and to control the production of the drug, food or beverage . Therefore , the claimed use allows for enhancing the product quality of the respective drug, food or beverage . In the following, the invention is described based on several embodiments in di f ferent figures . The figures are to be construed as supplementing each other . Features with identical numerals have the same technical meaning . The features of di f ferent embodiments are interchangeable across the figures and may be combined with each other, too . Furthermore , the features in the figures may be combined with the features outlined above . Particularly, the figures show :

FIG 1 a first embodiment of the claimed method during a first stage in a longitudinal hal f-section;

FIG 2 the first embodiment of the claimed method during a second stage in a longitudinal hal f-section;

FIG 3 the first embodiment of the claimed method during a third stage in a longitudinal hal f-section;

FIG 4 a second embodiment of the claimed method during a first stage in a longitudinal hal f-section;

FIG 5 the second embodiment of the claimed method during a second stage in a longitudinal hal f-section;

FIG 6 the second embodiment of the claimed method during a third stage in a longitudinal hal f-section;

FIG 7 an embodiment of the claimed measuring tube in a longitudinal section;

FIG 8 another embodiment of the claimed flowmeter in a longitudinal section .

FIG 1 shows a first embodiment of the claimed method 100 during a first stage in a longitudinal hal f-section . In that first stage , a first step 110 of the claimed method 100 is finished . Thus , a tubular ceramic green body 20 and a wire 32 are provided . The tubular ceramic green body 20 substantially extends along a main central axis 15 and is to form a pipe section 16 of a measuring tube 10 that is to be manufactured by virtue of the claimed method 100 . Once fired, the tubular ceramic green body 20 serves as the pipe section 16 and i f configures to guide a fluid 12 along its inner face 17 . The fluid 12 has several physical properties 13 , which allow for measuring a flow speed 14 of the fluid 12 . The wire 32 is to form a part of a measuring electrode 30 that is to be manufactured in the course of the claimed method 100 . The wire 32 is made of a noble metal , for example platinum . A substantially radially extending bore 22 is formed during the first step 110 or a second step 120 of the method 100 . A radial direction is defined in relation to the main central axis 15 . A radially outward direction is symboli zed by the arrow 21 , a radially inward direction by the arrow 23 . During the second step 120 of the claimed method 100 , the wire 32 is inserted into the bore 22 . In such an assembled state , an inner end 33 of the wire 32 extends into the interior of the tubular ceramic green body 20 .

A second stage of the method according to the first embodiment of the claimed method 100 is shown in FIG 2 in a longitudinal hal f-section . The second stage follows the first stage , as depicted in FIG 1 , immediately or with intermediate steps . During the second stage , a third step 130 of the claimed method 100 is performed . During the third step 130 , an area 28 adj acent to the inner end 33 of the wire 32 is machined to form a recess 26 in the inner face 17 . Furthermore , the wire 32 is machined to be flush with the adj acent area 28 . The adj acent area 28 in the recess 26 is machine to have an adj ustable surface roughness 24 that of fers an improved adhesion for a later fourth step 140 . The machining 31 is substantially performed as a milling step and may utili ze a tool that is configured to create the aspired surface roughness 24 in the area 28 adj acent to the inner end 33 of the wire 32 . In addition to that , the recess 26 is made with an adj ustable recess depth 27 , which is substantially its radial dimensions . The recess 26 also has dimensions in an axial direction and a circumferential direction, which extend along the main central axis 15 or tangential to it . These dimensions form an outline 41 of the recess 26 . It is to be noted that the machining of the recess 26 and the adj acent area 28 are optional steps that may be omitted in other embodiments of the invention . In such embodiments , the wire 32 is still machined to be flush with the inner face 17 .

During the third step 130 , the tubular ceramic green body 20 with the inserted wire 32 is subj ected to a firing step 48 , in which they are exposed to a given temperature for a controlled duration . These aspects are depicted as a thermometer symbol and a clock symbol . By virtue of the firing process 48 , the tubular ceramic green body 20 is at least partly fired and becomes the pipe section 16 of the measuring tube 10 that is to be manufactured . Since the tubular ceramic green body 20 comprises alumina or zirconia, the firing step 48 causes a shrinkage 29 at the bore 22 . Due to the shrinkage 29 , the wire 32 is irremovably fastened to the pipe section 16 . The shrinkage 29 forms a durable and tight seal that isolates the fluid 12 from substances outside of the pipe section 16 . Either the machining step 31 or the firing step 48 may be performed first during the third step 130 of the claimed method 100 .

FIG 3 shows a third stage of the first embodiment of the claimed method 100 in a longitudinal hal f-section . The third stage may follow directly or indirectly after the second stage , as shown in FIG 2 . In the third stage , a fourth step 140 of the claimed method 100 is performed . In that fourth step 140 , the recess 26 formed in the third step 130 , as depicted in FIG 2 , is used to accommodate an electrode head 34 . The electrode head 34 is made through an additive manufacturing step 40 , which is symboli zed as anti-parallel arrows . The additive manufacturing step 40 is a trans fer printing step, during which an unformed material is filled into the recess 26 . The electrode head 34 is made of the same material as the wire 32 , for example a noble metal like platinum . The fourth step 140 also comprises a firing step 48 , in which the unformed material in the recess 26 is sintered to form the electrode head 34 . In the course of that firing step 48 , the electrode head 34 connects to the inner end 33 of the wire 32 . The electrode head 34 has an electrode head thickness 35 that substantially corresponds to the recess depth 27 as shown in FIG 2 . Furthermore , a surface tension is applied to the electrode head 34 , thus minimi zing crevices there . Therefore , the firing step 48 allows for forming a smooth surface . The electrode head thickness 35 is 5 pm to 50 pm . Such electrode head thicknesses 35 allow for making electrode heads 34 with little material and still may be precisely manufactured in the additive manufacturing step 40 . The electrode head 34 is substantially flush with the inner face 17 of the wall 18 , that surrounds the electrode head 34 . Since the electrode head 34 is accommodated in the recess 26 , it is robust against being peeled of f by the fluid 12 . The electrode head 34 , and in turn the wire 32 , are made of a food-safe material , that allows to use the measuring tube 10 in a drugprocessing or food-processing application .

A second embodiment of the claimed method 100 is shown in FIG 4 in a first stage . That first stage is depicted in a longitudinal hal f-section . The method 100 serves for manufacturing a measuring tube 10 that is configured to be used in a flowmeter 60 not shown in FIG 4 . In the first stage of the claimed method 100 , a first step 110 is completed . In that first step 110 , a tubular ceramic green body 20 and a wire 32 are provided . The tubular ceramic green body 20 comprises alumina and/or zirconia and the wire 32 is made of a noble metal , for example platinum . In the course of the methodl O O , the tubular ceramic green body 20 is to form a pipe section 16 and the wire 32 is to be a part of a measuring electrode 30 . The tubular ceramic green body 20 substantially extends along a main central axis 15 , which defines a radially outer direction and a radially inner direction . The radially outer direction is symboli zed by the arrow 21 and the radially inner direction by the arrow 23 . Once the tubular ceramic green body 20 is fired, is it configured to guide a fluid 12 that flows through its interior at a flow speed 14 . The fluid 12 may flow on an inner face 17 of a wall 18 that defines interior of the tubular ceramic green body 20 or the pipe section 16 respectively . The fluid 12 has several physical properties 13 , which allow for determining the flow speed 14 , when the finished measuring tube 10 is operated as a part of a flowmeter 60 .

During the first step 110 or a second step 120 , a substantially radially extending bore 22 is formed in the wall 18 . Furthermore , the wire 32 is accommodated in a ceramic sleeve 36 , which may be in a green state or be at least partly fired . The ceramic sleeve 36 with the wire 32 accommodated in it are inserted into the bore 22 during the second step 120 . The ceramic sleeve 32 and the wire 32 may be machined separately to form a tight seal between each other . Furthermore , the wire 32 and the ceramic sleeve 36 may be inspected independent of the tubular ceramic green body 20 . Still further, the sleeve 36 and an adj acent area on the wall 16 are being at least party covered with ceramic glazing 37 and/or ceramic slurry 39 . The ceramic glazing 37 and/or the ceramic slurry 39 seal an interface between the wall 18 and the ceramic sleeve 36 . With the ceramic sleeve 36 inserted into the bore 22 , an inner end 33 of the wire 32 extends into an interior of the tubular ceramic green body 20 . Instead of glazing 37 or ceramic slurry 39 , a resin, e . g . epoxy-resin may be used as a sealant for the interface between the ceramic sleeve 36 and the tubular ceramic green body 20 . The resin may be applied after firing the tubular green ceramic body 20 .

FIG 5 shows the second embodiment of the claimed method 100 during a second stage in a longitudinal hal f-section . The second stage according to FIG 5 may follow a first stage as shown in FIG 4 directly or indirectly . In the second stage , a third step 130 of the claimed method 100 is performed . Particularly, an area 28 adj acent to the inner end 33 of the wire 32 is machined to form a recess 26 in the wall 18 of the tubular ceramic green body 20 or the pipe section 16 . Along the main central axis 15 , the recess 26 extends along the inner face 17 of the wall 18 across the ceramic sleeve 36 . The wire 32 , i . e . its inner end 33 , is also machined to be flush with the adj acent area 28 that is part of the recess 26 . The machining 31 of the wire 32 and the recess 26 is substantially a milling step . Edges of the recess 26 form its outline 41 , which may be determined by a user input and/or a program that controls the machining 31 . Furthermore , tools utili zed during the machining 31 are selected to create a selectable surface roughness 24 in the area 28 adj acent to the inner end 33 of the wire 32 . The surface roughness 24 is selected to of fer an improved adhesion in a following fourth step 140 . The recess 26 is made with a selectable recess depth 27 , which is its radial dimension .

The third step 130 also include a firing step 48 in which the tubular ceramic green body 20 with the inserted ceramic sleeve 36 and the wire 32 are exposed to a given temperature for a controlled duration . These aspects are symboli zed as a thermometer symbol and a clock symbol . Through the firing step 48 , the tubular ceramic green body 20 becomes the pipe section 16 . The ceramic glazing 37 and/or the ceramic slurry 39 are also cured in the firing step 48 and seal interfaces between the pipe section 16 , the ceramic sleeve 36 and the wire 32 . Either the firing step 48 or the machining 31 may be performed first in the third step 130 .

FIG 6 shows a third stage of the first embodiment of the claimed method 100 in a longitudinal hal f-section . The third stage may follow directly or indirectly after the second stage , as shown in FIG 5 . In the third stage , a fourth step 140 of the claimed method 100 is performed . In that fourth step 140 , the recess 26 formed in the third step 130 , as depicted in FIG 5 , is used to accommodate an electrode head 34 . The electrode head 34 is made through an additive manufacturing step 40 , which is symboli zed as anti-parallel arrows . The additive manufacturing step 40 is a trans fer printing step, during which an unformed material is filled into the recess 26 . The electrode head 34 is made of the same material as the wire 32 , for example a noble metal like platinum . The fourth step 140 also comprises a firing step 48 , in which the unformed material in the recess 26 is sintered to form the electrode head 34 . In the course of that firing step 48 , the electrode head 34 connects to the inner end 33 of the wire 32 . The electrode head 34 has an electrode head thickness 35 that substantially corresponds to the recess depth 27 as shown in FIG 2 . The electrode head thickness 35 is 5 pm to 50 pm . Such electrode head thicknesses 35 allow for making electrode heads 34 with little material and still may be precisely manufactured in the additive manufacturing step 40 . The electrode head 34 is substantially flush with the inner face 17 of the wall 18 , that surrounds the electrode head 34 .

Since the electrode head 34 is accommodated in the recess 26 , it is robust against being peeled of f by the fluid 12 . The electrode head 34 , and in turn the wire 32 , are made of a food-safe material , that allows to use the measuring tube 10 in a drug-processing or food-processing application .

An embodiment of the claimed measuring tube 10 is shown in a longitudinal section in FIG 7 . The measuring tube 10 is configured to be a part of a flowmeter 60 that is not shown in FIG 7 . The measuring tube 10 comprises a pipe section 16 that is made of a ceramic material , that comprises alumina and/or zirconia . The pipe section 16 comprises a wall 18 that encloses its interior . The pipe section 16 is configured to guide a fluid 12 along its main central axis 15 . The fluid 12 has several physical properties 13 which allow for measuring its flow speed 14 . In the outside , there are excitation means 42 attached to the pipe section 16 . The excitation means 42 are configured to cause a measurement pulse 44 that interact with the fluid 12 . To that end, the excitation means 42 may be controllable coils . By virtue of its physical properties 13 , an electrical quantity in the fluid 12 is af fected by the measurement pulses 44 . On its inner face 17 , an electrode head 34 is recessed into the wall 18 of the pipe section 16 . The electrode head 34 is made of a noble metal , for example platinum, and serves as an antenna to receive the electrical quantity af fected by the measurement pulses 44 . The electrode head 34 is electrically connected to an inner end 33 of a wire 32 , that extends to the electrode head 34 in a substan- tially radial direction . Thus , the wire 32 and the electrode head 34 are part of a measuring electrode 30 . The measuring tube 10 is manufactured through a method 100 as depicted in at least one of FIG 1 through FIG 6 . Particularly, the electrode head 34 is manufactured by an additive manufacturing step 40 , as shown in FIG 3 or FIG 6 . The recess 26 , into which the electrode head 34 is recessed, may be manufactured with a selectable outline 41 . Since the electrode head 34 is manufactured to fill the recess 26 , the electrode head outline 38 assumes the outline 41 of the recess 26 . The electrode head 34 according to FIG 7 is optimi zed pursuant to antenna theory and shows an improves measurement sensitivity . At the same time , the electrode head 34 is made from little material and is therefore cost-ef ficient . Altogether, the measuring tube 10 of fers augmented measurement capabilities and improved cost-ef ficiency . Since the electrode head 34 and the pipe section 16 are made of food-safe materials , the measuring tube 10 is suitable for drug-processing or foodprocessing applications .

FIG 8 shows another embodiment of the claimed flowmeter 60 schematically in a longitudinal section . The flowmeter 60 comprises a measuring tube 10 that is manufactured pursuant to a method 100 , as outlined for example in FIG 1 to FIG 6 . The measuring tube 10 comprises a pipe section 10 that is configured to be attached to a piping system not shown in FIG 8 . The measuring tube 10 is configured to measure a flow speed 14 of a fluid 12 that flows through the measuring tube 10 . The measuring tube 10 comprises a wall 18 that guides the fluid 12 along the main central axis 15 of the measuring tube 10 . In addition to that , the measuring tube 10 is equipped with excitation means 42 that is embodied as a controllable coil . The excitation means 42 is controllable by an evaluation unit 50 that is configured to transmit control signals 47 to the excitation means 42 . The excitation means 42 is configured to emit excitation pulses 29 that interact with the fluid 12 . Due to it physical properties 13 , the fluid 12 interacts with the excitation pulses 29 and af fects electri- cal quantities that may be received by electrodes 30 that extend into the pipe section 16 . Each of the electrodes 30 comprises an electrode head 34 that is recessed into an inner face 17 of the wall 18 . The electrode heads 34 are each made of a noble metal , for example platinum, and are each electrically connected to a wire 32 . The wires 32 and the corresponding electrode heads 34 are made of the same material . The electrodes 34 are configured to capture an electrical quantity that is characteristic for the flow speed 14 and to transmit corresponding measurement signals 45 to the evaluation 50 .

The evaluation unit 50 is configured to execute an evaluation computer program 52 that processes the measurement signals 45 . As a result of that processing, the flow speed 14 of the fluid 2 is determined . Furthermore , the evaluation unit 50 is coupled to a user-interface 51 that is configured to output the determined flow speed 14 . The evaluation unit 50 is also coupled to a data interface 53 that is configured to connect the evaluation unit 50 to a superordinate control unit 55 . The data interface 53 is configured to establish a communicating data link 54 that allows for exchanging data between the evaluation unit 50 and the superordinate control unit 55 . The determined flow speed 14 may be output from the evaluation unit 50 to the superordinate control unit 55 . Moreover, the superordinate control unit 55 in configured to execute a computer program product 70 that encompasses a replication 72 of the measuring tube 10 . The replication 72 mirrors the functionality of the measuring tube 10 and is configured to simulate the operational behavior of the measuring tube 10 when executed as part of the computer program product 70 . The computer program 70 is embodied as a digital twin of the measuring tube 10 and serves for a real-time supervision of the measuring tube 10 . Furthermore , the computer program product 70 is configured to detect a defunct component of the measuring tube 10 .