Process automation field device

Abstract

The invention relates to a process automation field device (1) for determining a property of a medium, in particular a flow meter (100) for determining a flow velocity-based measurement variable, comprising: - at least one sensor component (21) of a sensor (20) for determining the property of a medium; - at least one electronic component (31) of an electronic unit (30) for operating the sensor (20); - a housing (10) for accommodating the at least one electronic component and / or sensor component (21, 31), the housing (10) having a housing body (11) with a housing wall (12) and a housing chamber (13), which is delimited by the housing wall (12) and in which the at least one electronic component (31) and / or sensor component (21) is at least partly situated; and - a cable guide (50), which is formed in particular from a plastic, for guiding at least one cable (60), which connects the at least one sensor component (31) to the at least one electronic component (21), the cable guide (50) having at least one guide (51), along which the at least one cable (60) extends, and the at least one guide being designed and configured to hold at least one cable in a specified cable position and protect the cable against tensile forces and / or vibrations.

Description

[0001] Field device for process automation

[0002] The invention relates to a field device for process automation for determining a medium property of a medium, in particular a flow meter for determining a flow velocity-dependent measured quantity.

[0003] In automation technology, particularly in process automation, field devices are frequently used to detect and / or control process variables. Sensors, such as those integrated into level gauges, flow meters, pressure and temperature gauges, pH / ORP meters, conductivity meters, etc., are used to detect process variables, measuring levels, flow rates, pressure, temperature, pH, and conductivity. Actuators, such as valves or pumps, are used to control process variables, changing the flow rate of a liquid in a pipe section or the fill level in a container. In principle, all devices used close to the process that provide or process process-relevant information are considered field devices.

[0004] A field device is specifically selected from a group consisting of flow meters, level meters, pressure meters, temperature meters, limit level meters and / or analytical measuring instruments.

[0005] Flow meters include, in particular, Coriolis, ultrasonic, vortex, thermal, and / or magnetic-inductive flow meters. Level meters include, in particular, radar-based level meters, microwave level meters, ultrasonic level meters, time-domain reflectometric level meters, radiometric level meters, capacitive level meters, inductive level meters, and / or temperature-sensitive level meters. Pressure meters include, in particular, absolute, gauge, or differential pressure meters. Temperature meters include, in particular, meters with thermocouples and / or temperature-dependent resistors. Limit level meters include, in particular, vibronic limit level meters, ultrasonic limit level meters, and / or capacitive limit level meters.Analytical measuring instruments include, in particular, pH sensors, conductivity sensors, oxygen and active oxygen sensors, (spectro)photometric sensors, and / or ion-selective electrodes.

[0006] The field device used to determine medium properties is frequently exposed to vibrations and mechanical shocks during operation. This can cause connectors linking the sensor unit to the electronics unit to become loose, or electromechanical coupling can disrupt the measurement. Such influences must generally be prevented. Current solutions include the use of clamps, cable ties, and / or a cured potting compound to secure the connectors and cables. These solutions are complex and result in higher installation costs.

[0007] The invention is based on the objective of remedying the problem.

[0008] The problem is solved by the field device according to claim 1.

[0009] The field device according to the invention for process automation for determining a medium property of a medium, in particular a flow meter for determining a flow velocity-dependent measured quantity, comprising:

[0010] - at least one sensor component of a sensor for determining the medium property of a medium;

[0011] - at least one electronic component of an electronic system for operating the sensor;

[0012] - a housing for accommodating the at least one electronic and / or sensor component, wherein the housing has a housing body with a housing wall, wherein the housing has a housing chamber which is bounded by the housing wall, wherein the at least one electronic and / or sensor component is arranged at least partially in the housing chamber,

[0013] - a cable guide, in particular made of plastic, for guiding at least one cable connecting the at least one sensor component to the at least one electronic component, wherein the cable guide has at least one guide along which the at least one cable extends, wherein the at least one guide is designed and configured to hold at least one cable in a predetermined cable position and to protect it against tensile force and / or vibration.

[0014] Field devices, especially flow meters, can be exposed to vibrations or mechanical shocks. These can cause connectors to detach or disrupt measurements due to electromechanical coupling. Such influences must be prevented in the area of ​​the electrical connection between the sensor and the electronics. This is usually achieved using various components, such as clamps, cable ties, etc. This results in increased space requirements and higher costs for components and assembly. The positional locking of various wire connections between the sensor and the electronics is achieved precisely and cost-effectively with the field guidance system according to the invention. The following problems from the prior art no longer exist.There is no undefined cable position that could lead to interference and / or failure due to vibration; no mounting points are required on the electronics, resulting in improved utilization of the electronic surface area. Furthermore, apart from cost-optimized standard components, no complex electrical connection components are required, and no cable assemblies or soldered connections are necessary.

[0015] Advantageous embodiments of the invention are the subject of the dependent claims.

[0016] One embodiment provides that the cable routing in the housing chamber is held in a predetermined position by means of a form-fit and / or force-fit connection.

[0017] One embodiment provides that the electronic component comprises a printed circuit board, with the cable routing acting in conjunction with the printed circuit board and / or a printed circuit board holder designed to hold the printed circuit board in a predetermined position within the housing chamber.

[0018] One embodiment provides that at least one guide is located in an outer edge area of ​​the cable guide and is designed as a slot.

[0019] One embodiment provides that the at least one guide further comprises at least one cable tab, in particular two cable tabs mirrored about a mirror plane, which is or are designed as strain relief.

[0020] The use of two tabs is particularly suitable for cables that do not have an elastic sheath.

[0021] One embodiment provides that the at least one guide further comprises at least one separating element, in particular at least one separating stud, which at least partially covers the at least one cable, for separating and strain relief of a two-core cable.

[0022] When using separating elements, a single tab is sufficient if the cable sheath is elastic. This allows for a force-fit connection. The cable in question could, for example, be a two-core cable, a coil cable (i.e., a service cable).

[0023] One embodiment provides that the at least one guide comprises a first guide and a second guide, wherein an operating cable is guided in the first guide, via which an operating signal of at least 1 V can be applied at least temporarily during operation of the field device, wherein a signal cable is guided in the second guide, via which a measurement signal in the range of 0.5 to 6000 pV can be measured at least temporarily during operation of the field device, wherein there is a minimum distance of 10, in particular 40 and preferably 100 millimeters between the first guide and the second guide.

[0024] One embodiment provides that the housing chamber has an electronics section in which the at least one electronic component is arranged, wherein the housing chamber has a sensor section in which the at least one sensor component is arranged, wherein the cable routing is arranged between the electronics section and the sensor section in such a way that it reduces convection of heat from the at least one sensor component to the at least one electronic component.

[0025] One embodiment provides that the field device continues to include an insulating body which is arranged in the housing chamber, the insulating body being in contact with the cable routing.

[0026] One embodiment provides that the insulating body is designed and positioned relative to the cable routing and the at least one cable in such a way that the at least one cable is guided between the insulating body and the cable routing.

[0027] One embodiment provides that the cable routing has at least one section which is shaped like a trough, wherein the at least one section conceals the at least one electronic component.

[0028] One embodiment provides that the cable routing has at least two sections which are shaped like troughs, wherein the two trough-shaped sections are separated by a partition, in particular a crossbar.

[0029] One embodiment provides that the field device is a flow meter, in particular a magnetic-inductive flow meter with a measuring tube, wherein the at least one sensor component comprises a magnetic field-generating device arranged on an outer lateral surface of the measuring tube, in particular with at least one magnetic coil, and at least two measuring electrodes.

[0030] The invention is explained in more detail with reference to the following figures. They show:

[0031] Fig. 1: a perspective view of a partially cutaway field device;

[0032] Fig. 2: a close-up view of two designs of a guide;

[0033] Fig. 3: a longitudinal section through a sensor, electronics and cable routing;

[0034] Fig. 4: a perspective view of a cable routing arranged on an insulating body;

[0035] Fig. 5: a longitudinal section through a cable guide arranged on an insulating body; and

[0036] Figs. 6a-c: Three cross-sections offset in the longitudinal direction of a magnetic-inductive flowmeter. Fig. 1 shows a perspective view of a partially cutaway field device (1) for process automation for determining a medium property. This field device (1) is suitable for applications with a medium temperature of ≥ 100°C. In this specific case, the illustrated configuration shows a flowmeter (100) for determining a flow velocity-dependent measured quantity. The flow velocity-dependent measured quantity can be a flow velocity, a volumetric flow rate, or a mass flow rate of the medium to be monitored. The sensor (20, see Fig. 20) required for determining the flow velocity-dependent measured quantity is shown in the diagram.6a to 6c) may, depending on the measuring principle, comprise as a sensor component (21) a magnetic field generating device, a magnetic field guiding device, at least two measuring electrodes, a vortex paddle, at least one excitation coil, at least one sensor coil, at least one microwave antenna, at least two ultrasonic transducers and / or at least two temperature sensors (e.g. resistance thermometers).

[0037] The illustrated field device (1) comprises a housing (10) for accommodating the at least one sensor component (21, see Figs. 2a, 2b) and the at least one electronic component (31, see Figs. 2a, 2b) of the electronics (30). The electronics (30) are configured to operate the field device (1), in particular the flow meter (100), and / or to determine the medium property, in particular the flow velocity-dependent measured quantity. The electronics (30) may include a signal input and / or a signal output. The electronics (30), in particular the at least one electronic component (31), may include at least one transformer, one capacitor, one inductor, one power supply component, one voltage or current regulator, and / or one voltage converter. Furthermore, the electronics (30) may include a display, operating, measuring, and / or evaluation circuit. The electronics (30) may also include a microprocessor and / or a microcontroller.

[0038] The housing (10) comprises a housing body (11) which in turn has a housing wall (12). The housing body (11) can be made of plastic, metal, or a fiber composite. The housing wall (12) can, for example, be a sheet metal wall, particularly a thin-walled one. The housing wall (12) can also be made of multiple parts. For example, a shell element (14) and a frame element (15) can be joined together, particularly by a material bond, to form the housing wall (12). The shell element (14) can be joined to the frame element (15) by a material bond, particularly by a weld. Alternatively, a positive-locking and / or force-locking connection can be provided using fasteners (bolts, screws, rivets). The frame element (15) can comprise a single part, particularly a bent one, or an assembly made up of several parts.The sheath element (14) preferably has a mean thermal conductivity that is higher than the mean thermal conductivity of the frame element (15). This results in a reduced heat transfer from the medium via the frame element (15) to the at least one electronic component (31) and an increased dissipation of the heat generated at the electronic component (31) to the environment via the sheath element (14). This can be achieved by selecting the wall thickness or the materials of the individual elements. For example, the wall thickness of the wall element (14) can be less than the wall thickness of the frame element (15). The frame element (15) has a greater thickness than the wall element (14) because it must possess sufficient mechanical stability to support or hold, for example, a measuring tube (101).

[0039] Optionally, an opening for a display (not shown) may be provided in the housing wall (13), in which a display for showing measured values ​​and / or status information is arranged.

[0040] The housing (10) has one, in particular exactly one, housing chamber (13, see Figs. 6a to 6c), which is bounded by the housing wall (12) and in which at least one electronic component (31) and / or the sensor component (21) is arranged at least partially. The at least one electronic component (31) is arranged at least partially in an electronics section (EA) of the housing chamber (13), and the at least one sensor component (21) is arranged at least partially in a sensor section (SA) of the housing chamber (13).

[0041] The illustrated housing (10) further comprises a housing neck (19) (see also Figs. 6a to 6c), which housing neck (19) is arranged between the sensor section (SA) and the electronics section (EA). The housing neck (19) can be designed as a connecting tube. In contrast, the housing neck (19) of this embodiment is designed as a tapered section of the housing body (11). The housing wall (12) is bent inwards towards the housing chamber (13) on two opposite sides in the region of the housing neck (19), so that the housing wall (12) is essentially U-shaped in the region of the housing neck (19) (see Figs. 5a-c).

[0042] The field device can have an insulating body (40) that spatially separates at least partially the electronics section (EA) from the sensor section (SA) (see Figs. 4, 5, 6a to 6c). One embodiment of the insulating body (40) is shown, for example, in Figures 4 and 5. The insulating body (40) is designed and configured to reduce heat convection, i.e., heat transfer between the sensor section (SA) and the electronics section (EA). This means that the electronics section (EA) and the at least one electronic component (31) arranged therein take longer to reach a temperature increase caused by the elevated medium temperature. This ensures that the medium can briefly reach the temperature required, for example, for cleaning or sterilization processes, while the resulting electronics temperature of the electronics section (EA), in particular of the electronics (30), is reduced.the electronic component (31), however, remains below a critical limit. This results in the aging of the at least one electronic component (31) being reduced and the service life and reliability of the at least one electronic component (31) remaining stable.

[0043] The insulating body (40) can be shaped and positioned in the housing chamber (13) such that convection originating from the frame element (15) towards a center point (MP) of the at least one sensor component (31) is reduced, at least in sections. The medium under investigation can have a medium temperature that is significantly higher than the ambient temperature. For short periods, the medium temperature can also exceed the maximum application temperature specified for the field device (1). In this case, the medium temperature heats the housing wall (12), in particular the frame element (15) and the casing element (14). These release the heat to the environment but also conduct it towards the electronics section (EA).In order to prevent the heat emitted by the frame element (15) from being directed to at least one electronic component (31) and thus causing the electronic temperature there to exceed a critical limit, the insulating body (40) also extends at least partially between the frame element (15) and the electronic component (31).

[0044] Fig. 1 shows a side view of the interior of the field device according to the invention. In the housing chamber (13) the at least one sensor component (21) of the sensor (20) for determining the medium property of a medium - in this case the flow velocity-dependent measured quantity - and the at least one electronic component (31) of the electronics (30) for operating the sensor (20) - e.g. a printed circuit board with the necessary operating, measuring and / or evaluation circuitry - are arranged.

[0045] The at least one electronic component (31) can be an electrically insulating electronic component carrier, in particular a printed circuit board (32), on which electronic components (33) are arranged to form an operating, measuring and / or evaluation circuit.

[0046] The insulating body (40), in particular its two side arms (43a, 43b), can be positioned relative to the electronic component carrier, in particular the printed circuit board (32), such that, when viewed from above, the insulating body (40), in particular its two side arms (43a, 43b), each covers a partial section (TA1, TA2) of the electronic component carrier, in particular the printed circuit board (32), especially in an edge region of the printed circuit board (32). At the same time, the electronic component carrier, in particular the printed circuit board (32), has a further partial section (TA3) which, when viewed from above, is not covered by the insulating body (40), in particular not by its side arms (43a, 43b).The further subsection (TA3) differs from the subsections (TA1) and the subsection (TA2) in that at least one transformer (33a), one capacitor (33b), one choke coil (33d), one power supply component (33c), one voltage or current regulator and / or one voltage converter (33e) is or are arranged in the further subsection (TA3), while the subsection (TA1) and the subsection (TA2) are free of the aforementioned electronic components (33).

[0047] The two side arms (43a, 43b) can each have a side arm length (L1, L2). The two side arm lengths (L1, L2) can be identical. In the illustrated embodiment, the two side arm lengths (L1, L2) differ from each other. Side arm (43a) with side arm length (L2) is shorter than side arm (43b) with side arm length (L1).

[0048] The insulating body (40) can be positively fitted into the housing chamber (13). For this purpose, the insulating body (40) can have a receptacle (44, see Figs. 3 and 4) with which it interacts with another component of the field device (1) that is fixedly arranged in the housing chamber (13). Alternatively or additionally, the insulating body (40) can have a bearing surface (47) with which it rests on a component of the field device (1) that is fixedly positioned in the housing chamber (13). This component can be, for example, a grounding socket (110) and / or a dome mount (111) (e.g., a fixed threaded sleeve) via which a flange with the measuring tube can be fixed (e.g., by means of a screw).

[0049] Furthermore, the insulating body (40), in particular the two side arms (43a, 43b), can have a contact surface (45) on one side facing away from the at least one electronic component (31), which rests against one or the inner surface of the housing wall (12) and which conforms to the housing wall (12). For this purpose, the insulating body (40) can assume a shape, at least in sections, that resembles or corresponds to the contour of the housing wall (12), in particular the outer element (14).

[0050] The insulating body (40) can be spaced apart from the at least one electronic component (31), in particular the printed circuit board (32), i.e., the insulating body (40) is not in direct contact with the at least one electronic component (31), in particular with the printed circuit board (32). The insulating body (40) is therefore not designed to support a printed circuit board (32) or a display and is thus not equivalent to holding devices made of expanded polypropylene (e.g.). The insulating body (40) is mechanically fixed to the cable guide (50). The cable guide (50) can be an injection-molded plastic component that is positively and / or force-fit connected to a support (80) for holding the at least one electronic component (31).The carrier (80) comprises a main body (81) with at least one strip-shaped extension (82) which is folded inwards, forming a two-layer area in which an internal thread is arranged and which has a contact surface that is in contact with the at least one electronic component (31). Furthermore, the main body (81) has several strip-shaped extensions which are bent with respect to a reference plane defined by the main body and via which the carrier (80) is connected to the frame element (15). The main body (81) is made of a sheet approximately 1.5 mm thick, which has three strip-shaped extensions (82) and four strip-shaped extensions and bent extensions. The electrically conductive extensions (82) are U-shaped and thus form a contact area approximately 3 mm thick.A contact area has a through-hole with an internal thread to accommodate a connecting element (83) (e.g., a screw, a bolt, or a rivet). Further electrically conductive connecting elements are provided to connect the support (80) to the frame element (15) by spot soldering or resistance spot welding, creating an electrically conductive connection between the main body (80) and the frame element (15).

[0051] The sensor section (SA) contains a potting compound (16), which is cast into the housing chamber (13), particularly after the at least one sensor component (21) and / or electronic component (31) has been mounted, and which has cured to prevent condensation on the at least one sensor component (21). The potting compound (16) can, for example, be a silicone rubber that vulcanizes into a soft silicone gel at room temperature thanks to a crosslinking agent. The basic shape (41) of the insulating body (40) is at least partially covered or wetted with the potting compound (16). The insulating body (40) can also serve to separate the potting compound (16) in the sensor section (SA) from the electronic section (EA). It is advantageous if the electronic section (EA) is free of potting compound (16).

[0052] The insulating body (40), in conjunction with another component, in particular a cable guide (50) for guiding cables connecting the at least one sensor component (21) to the at least one electronic component (31), can completely separate the sensor section (SA) from the electronic section (EA), particularly in a cross-sectional plane (SE) through the housing chamber (13). Complete separation within the meaning of the invention means a coverage of the cross-sectional area of ​​the electronic chamber (13) in the cross-sectional plane (SE) by more than 80%, in particular 90%. The cross-sectional plane (SE) is perpendicular to the cross-sectional plane of the field device (1). If the field device (1) is a flow meter (100), the cross-sectional plane (SE) runs perpendicular to a cross-sectional plane of the measuring tube (101) and also perpendicular to a longitudinal plane of the measuring tube (101).

[0053] The insulating body (40) can extend at least partially through the housing neck (19) or is at least partially located in the area of ​​the housing neck (19).

[0054] The cable guide (50) is designed to hold at least one cable (60), which connects the sensor (20), in particular the at least one sensor component (21), to the electronics (30), in particular to the at least one electronic component (31), in a predetermined cable position and to protect it against tensile force and / or vibration. The cable guide (50) can be an injection-molded component made of plastic.

[0055] According to the invention, the field device (1) has a cable guide (50), in particular made of a plastic, for guiding at least one cable (60) connecting the at least one sensor component (31) to the at least one electronic component (31). The cable (60) can be configured to transmit an operating signal provided at the at least one electronic component (31) to the at least one sensor component (31) and / or to transmit a measurement signal from the sensor component (31) to the at least one electronic component (31). Accordingly, the cable (60) can be an operating cable (61) or a sensor cable (62a, 62b). The cable guide (50) can, for example, be a one-piece injection-molded component. Alternatively, the cable guide (50) can also comprise a plastic assembly made of several individual parts, in particular by positive and / or force-fit or material-fit connections.The cable guide can, for example, be made of polycarbonate. For the purpose of guiding the cable (60), the cable guide (50) has at least one guide (51) along which the at least one cable (60) extends. In the most general sense, the guide (51) is a section of the cable guide (50) that is designed and configured to hold the at least one cable (60) in a predetermined position and to protect it against tensile force and / or vibration. The guide (51) can, for example, be a feature of the cable guide (50) that limits radial movement (perpendicular to the longitudinal axis) of the cable (60). Furthermore, the illustrated cable guide (50) is planar, at least in some sections.

[0056] The cable guide (50) is held in a predetermined position within the housing chamber (13) by means of a positive-locking and / or force-locking connection. For this purpose, the cable guide (50) can have at least one connecting element that engages with a corresponding complementary receptacle or opening, thus achieving a fixed position. Suitable connecting elements include screws, pins, locking tabs, buckles, latches, clips, or hooks.

[0057] The electronic component (31) can comprise a printed circuit board (32) on which electronic components such as converters, capacitors, inductors, transformers, electronic memory, microchips, and / or processors can be arranged. The cable guide (50) interacts indirectly with the printed circuit board (32) and / or directly with a printed circuit board holder (71), which is designed to hold the printed circuit board (32) in a predetermined position within the housing chamber (13).

[0058] The at least one guide (51) comprises a first guide (51a) and a second guide (51b), wherein an operating cable (61) is guided in the first guide (51a), via which an operating signal of at least 1 V can be applied at least temporarily during operation of the field device (1), and wherein a signal cable (62) is guided in the second guide (51b), via which a measurement signal in the range of 0.5 to 6000 pV can be measured at least temporarily during operation of the field device (1), wherein there is a minimum distance of 10, in particular 40 and preferably 100 millimeters between the first guide (51a) and the second guide (51b). The electronic component can be configured to provide an operating signal of at least 1 V at least temporarily to the at least one sensor component via the operating cable. Furthermore, the electronic component can be configured to determine a measurement signal in the range of 0.5 to 6000 pV at least temporarily via the signal cable.

[0059] The field device (1) can be a flow meter, in particular – as shown – a magnetic-inductive flow meter (200), which includes a measuring tube (101) for guiding the medium to be monitored. In this case, the at least one sensor component (21) comprises a magnetic field-generating device (102) arranged on an outer surface of the measuring tube (101) for generating a magnetic field penetrating the measuring tube, in particular with at least one magnetic coil (103), and at least two measuring electrodes (104a, 104b) which are electrically connected to a measuring circuit (which can be part of the electronic component (31)). The measuring circuit is configured to measure a measuring voltage induced in the flowing medium.An evaluation circuit (which may also be part of the electronic component (31)) can be set up to determine a flow velocity-dependent measured quantity (e.g. the flow velocity, the volume flow or the mass flow) as a function of the induced measuring voltage.

[0060] The cable routing (50) is always in the same relative position to the electronics (30) and the sensor (20) in different device variants (e.g., with different nominal diameters of measuring tubes). The geometric differences between the device variants are accommodated by the thermal insulation (see Fig. 4-6).

[0061] Fig. 2 shows a close-up view of two embodiments of a guide (51). As shown, the cable guide (50) can have several guides (51) that differ in their design. The cable guide (50) has a circumferential edge (59) that delimits a partially planar section of the cable guide (50). The first embodiment of the at least one guide (51) is located in an outer edge region of the cable guide (50) and can be designed as a slot (52). In the embodiment shown, the cable guide has two slots (52, 52b). The cable (60) is guided through the slot (52), or through the two slots (52a, 52b), each in the form of a recess in the body of the cable guide (50). The cable (60) can, for example, be a sensor cable (62a). The sensor cable (62a) shown comprises two individual conductors, each extending along one of the two slots (52).At the ends, each individual conductor has a micro-HF connector (65), preferably an IPEX connector, which is connected or can be connected to a connection point on the circuit board (32).

[0062] The second embodiment of the at least one guide (51) further comprises at least one cable tab (55) that at least partially conceals the at least one cable (60), in this case also a sensor cable (62b), in particular two cable tabs (55a, 55b) mirrored about a mirror plane, which are designed as strain relief. The (respective) cable tab (55) is hook-shaped or has a projecting section that takes the form of a hook and is designed and configured to absorb a force acting on the cable so that the connector attached at the end is not pulled out of the connector when force is applied.

[0063] Furthermore, the cable guide (50) can have at least one section (KTA1) that is shaped like a trough. This means that a trough-shaped depression extends within the cable guide (50), or that the cable guide (50) is deformed or shaped section by section such that a depression extends from a planar surface on one side, and a raised section extends from a planar surface on the opposite side. The cable guide (50) is positioned relative to the electronic component (31) such that the at least one section (KTA1) conceals the at least one electronic component (31). The section (KTA1) is preferably positioned where no insulating element (40, see Fig. 4) extends from the electronic component (31) towards the sensor component (21).The trough-shaped structure of the section (KTA1) serves to create a defined distance between the cable routing and the at least one electronic component (31), so that the intervening air cushion can act as an additional thermal insulator. At the points between the electronic and sensor components (21, 32) where no insulating material is present, thermal insulation is provided by the air-plastic-air barrier.

[0064] Furthermore, the cable guide (50) can have at least two subsections (KTA1, KTA2) which are trough-shaped. The two trough-shaped subsections (KTA1, KTA2) can be separated by a partition, in particular a crossbar (57). The crossbar (57) is designed to prevent air circulation between the subsections (KTA1, KTA2).

[0065] Fig. 3 shows a longitudinal section through the sensor (20), the electronics (30), and the cable guide (50) of Fig. 2. In addition to the features mentioned above, the at least one guide (51) can further comprise at least one separating element (56), in particular at least one separating stud, which at least partially covers the at least one cable (60), for separating and strain relief of a two-core cable. In the illustrated embodiment, the separating stud is a cylindrical projection from the body of the cable guide (50). However, the separating stud can have a shape other than cylindrical. The cable guide (50) can have more than one separating element (56), in particular more than one separating stud.

[0066] The illustrated cable guide (50) includes a connecting element for attaching the cable guide (50) to the housing chamber (13) in such a way that it is held in a fixed position. This can be achieved, for example, by a positive-locking and / or force-locking connection with a holder (70), in particular a printed circuit board holder (71). For this purpose, the illustrated cable guide (51) has a locking lug (58) which engages in an opening of the holder (70), in particular the printed circuit board holder (71). The printed circuit board holder (71) is designed to hold the printed circuit board holder (71) in a fixed position. For this purpose, the printed circuit board (32) can be positively locked and / or force-locked to the printed circuit board holder (71). The printed circuit board holder (71) can, for example, be bonded to the housing wall (12).

[0067] Fig. 4 shows a perspective view of a cable guide (50) arranged on an insulating body (40). Fig. 5 shows a cross-section through an insulating body (40) in conjunction with a cable guide (50) and an electronic component (31). The cable guide (50) is designed to hold at least one cable (60), which connects the sensor (20), in particular the at least one sensor component (21), to the electronics (30), in particular to the at least one electronic component (31), in a predetermined cable position and to protect it against tensile force and / or vibration. The insulating body (40) has a receptacle (44) which encompasses the cable guide (50) at least partially. The receptacle (44) itself is formed by at least two webs (48a, 48b) projecting from the base shape (41). The cable guide (50) is planar in certain sections.At least one planar cable routing section extends into the recess (44) of the insulating body (40). In the illustrated embodiment (see Fig. 5), the at least one electronic component (31) comprises a printed circuit board (32) on which electronic components (33) are arranged. The printed circuit board (32) also provides at least one connection component for a cable (60), which cable (60) connects the at least one electronic component (31), in particular the printed circuit board (32), to the at least one sensor component (21).

[0068] The insulating body (40) can comprise a foam, in particular preferably expanded polypropylene or preferably expanded polystyrene. Alternatively, the insulating body can also consist entirely of a foam, in particular preferably expanded polypropylene or preferably expanded polystyrene. However, the insulating body (40) is preferably made of polypropylene, since the mechanical properties of the insulating body (40) made of polypropylene are better suited for assembly. The insulating body (40) shown has a basic shape (41) that extends from a first inner side (42a) of the housing wall (12), in particular of a frame element (15) of the housing wall (12), to a second inner side of the housing wall (12), in particular of the frame element (15) of the housing wall (22).This ensures that the cutting plane separating the at least one sensor component (21) from the at least one electronic component (31) is filled as completely as possible by the insulating body (40).

[0069] Furthermore, in two spaced-apart end sections of the basic shape (41) – each adjoining the frame element (15) – a side arm (43a, 43b) can extend from the basic shape (41) itself, in particular perpendicular to the basic shape (41). These two side arms (43a, 43b), which extend along the frame element (15), in particular along an inner surface of the housing wall (12), prevent the heat conducted from the sensor component (e.g., the measuring tube) via the frame element (15) from being transferred directly via the air in the electronics section (EA) to the at least one electronic component (31). The two side arms (43a, 43b) are thus designed to reduce convection from the frame element (15) to the at least one electronic component (31).The exposed area spanned by the two side arms (43a, 43b) is chosen to be exposed in order to allow the heat generated by the at least one electronic component (31) to be dissipated via the air in the electronics section (EA) towards the wall element (14).

[0070] Figures 6a to 6c show three cross-sections through the field device of the previous figures, in particular through a flow meter (100), offset along an axis. The flow meter (100) is preferably a magnetic-inductive flow meter (200). The magnetic-inductive flow meter (200) comprises a magnetic field-generating device with at least one electromagnetic coil (saddle coil or cylindrical coil), in particular with exactly two electromagnetic coils (210a, 210b), preferably arranged opposite each other, and / or at least one permanent magnet. The magnetic field-generating device is configured to generate a magnetic field penetrating the measuring tube (101) and the medium flowing through the measuring tube (101) in the application. Furthermore, the magnetic field-generating device can have at least one coil core (211), preferably in conjunction with a pole shoe.The magnetic-inductive flowmeter (200) further comprises a measuring tube (101) with a support tube, in particular made of metal, and an electrical liner in the form of an electrically insulating coating or an inserted hose or tube. Alternatively, the support tube can be made, in particular entirely, of an electrically insulating plastic or ceramic. In this case, a liner is not necessary. The support tube has two openings, in particular opposite ones, each containing a measuring electrode (130a, 130b). The measuring electrodes (130a, 130b) are electrically connected to a measuring circuit—which can be part of the electronics—that is configured to measure a measuring voltage induced in the flowing medium and, depending on this, to determine the flow velocity-dependent measured quantity.

[0071] The cable guide (50) offers the significant advantage of enabling the electrical connection (cable) to be secured and separated within the housing chamber of a fully welded field device, particularly a flow meter, and preferably a magnetic-inductive flow meter. This is especially advantageous when the device has no separable interface between the sensor and the electronics after the housing is assembled. The cable guide, in combination with the thermal insulation, inhibits convection between the separated compartments. This cable guide serves to protect the electrical connection to the sensor from vibrations and to hold it in position. In combination with thermal insulation, it separates the housing chamber between the electronics and the sensor without impairing the electrical connection.

[0072] The housing design of the illustrated embodiment integrates the electronics and the sensor, which comprises the measuring tube, the opposing electrodes, and the opposing electromagnetic coils, into a single housing chamber. The elimination of the pluggable interface between the electronics and the sensor is noteworthy, as the housing in its final form is completely welded.

Claims

PATENT CLAIMS 1. Field device (1) for process automation for determining a medium property of a medium, in particular a flow meter (100) for determining a flow velocity-dependent measured quantity, comprising: - at least one sensor component (21) of a sensor (20) for determining the medium property of a medium; - at least one electronic component (31) of an electronics (30) for operating the sensor (20); - a housing (10) for accommodating the at least one electronic and / or sensor component (21, 31), wherein the housing (10) has a housing body (11) with a housing wall (12), wherein the housing (10) has a housing chamber (13) which is bounded by the housing wall (12), wherein the at least one electronic and / or sensor component (21, 31) is arranged at least partially in the housing chamber (13), - a cable guide (50), in particular made of a plastic, for guiding at least one cable (60) connecting the at least one sensor component (31) to the at least one electronic component (31), wherein the cable guide (50) has at least one guide (51) along which the at least one cable (60) extends, wherein the at least one guide (51) is designed and configured to hold the at least one cable (60) in a predetermined cable position and to protect it against tensile force and / or vibration.

2. Field device (1) according to claim 1, wherein the cable guide (50) is held in a predetermined position in the housing chamber (13) by means of a positive and / or force-fit connection.

3. Field device (1) according to claim 1 or 2, wherein the electronic component (31) comprises a printed circuit board (32), wherein the cable guide (50) acts in conjunction with the printed circuit board (32) and / or a printed circuit board holder (71) which is configured to hold the printed circuit board (32) in the housing chamber (13) in a predetermined printed circuit board position.

4. Field device (1) according to one of the preceding claims, wherein the at least one guide (51) is located in an outer edge region of the cable guide (50) and is designed as a slot (52).

5. Field device (1) according to one of the preceding claims, wherein the at least one guide (51) further comprises at least one cable tab (55) at least partially covering the at least one cable (60), in particular two cable tabs (55a, 55b) mirrored about a mirror plane, which is or are arranged as strain relief.

6. Field device (1) according to one of the preceding claims, wherein the at least one guide (51) further comprises at least one separating element (56) at least partially covering the at least one cable (60), in particular at least one separating stud, for separating and strain relief of a multi-core, in particular two-core, cable.

7. Field device (1) according to one of the preceding claims, wherein the at least one guide (51) comprises a first guide (51a) and a second guide (51b), wherein an operating cable (61) is guided in the first guide (51a), via which an operating signal of at least 1 V can be applied at least temporarily during operation of the field device (1), wherein a signal cable (62) is guided in the second guide (51b), via which a measurement signal in the range of 0.5 to 6000 pV can be measured at least temporarily during operation of the field device (1), wherein there is a minimum distance of 10, in particular 40 and preferably 100 millimeters between the first guide (51a) and the second guide (51b).

8. Field device (1) according to one of the preceding claims, wherein the housing chamber (13) has an electronics section (EA) in which the at least one electronic component (31) is arranged, wherein the housing chamber (13) has a sensor section (SA) in which the at least one sensor component (21) is arranged, wherein the cable routing (50) is arranged between the electronics section (EA) and the sensor section (SA) in such a way as to reduce convection of heat from the at least one sensor component (21) to the at least one electronic component (31).

9. Field device (1) according to one of the preceding claims, wherein the field device (1) further comprises an insulating body (40) which is arranged in the housing chamber (13) and at least partially separates the electronics section (EA) from the sensor section (SA), wherein the insulating body (40) is configured to reduce convection between the sensor section (SA) and the electronics section (EA), wherein the insulating body (40) is in action with the cable guide (50).

10. Field device (1) according to claim 9, wherein the insulating body (40) is designed and positioned relative to the cable guide (50) and to the at least one cable (60) such that the at least one cable (60) is guided between the insulating body (40) and the cable guide (50).

11. Field device (1) according to claim 9 or 10, wherein the insulating body (40) comprises a foam, in particular a, preferably expanded, polypropylene or a, preferably expanded, polystyrene.

12. Field device (1) according to one of claims 9 to 11, wherein the insulating body (40) has a receptacle (44) into which the cable guide (50) engages.

13. Field device (1) according to one of claims 9 to 12, wherein the insulating body (40) in conjunction with the cable guide (50) completely separates the sensor section (SA) from the electronics section (EA), in particular in a section plane (SE) through the housing chamber (13).

14. Field device (1) according to one of the preceding claims, wherein the cable routing (50) has at least one subsection (KTA1) which is shaped like a trough, wherein the at least one subsection (KTA1) conceals the at least one electronic component (31).

15. Field device (1) according to claim 14, wherein the cable guide (50) has at least two subsections (KTA1 , KTA2) which are trough-shaped, wherein the two trough-shaped subsections (KTA1 , KTA2) are separated by a partition, in particular a transverse web (57).

16. Field device (1) according to one of the preceding claims, wherein the field device (1) is a flow meter (100), in particular a magnetic-inductive flow meter (200) with a measuring tube (101), wherein the at least one sensor component (21) comprises a magnetic field generating device (102) arranged on an outer lateral surface of the measuring tube (101), in particular with at least one magnetic coil (103), and at least two measuring electrodes (104a, 104b).

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