Housing assembly for a measuring device and measuring device

Abstract

Housing assembly with ground connection for a measuring device, comprising: housing chamber (GK) with conductive housing wall (GW); measuring and operating circuit with a printed circuit board (LP); conductive carrier (T), with a material thickness between 0.5 and 3 mm main body (H), and conductively connected to the housing wall (GW); wherein the carrier (T) comprises a plurality of strip-shaped support bodies (AK) which are continued from the main body (H) and are bent in a U-shape, so that contact regions (KB) are formed which have a support thickness corresponding to twice the material thickness of the main body (H), and have through-openings with a continuous internal thread (IG); wherein the support bodies (AK) are connected to the printed circuit board (LP) by means of a contact surface (KF); wherein the connection between the support body (AK) and the contact surface (KF) is formed by means of screws (S); wherein a conductive connection exists between the contact surface (KF) and the contact region (KB), so that the measuring and operating circuit, in particular the printed circuit board (LP), is at the potential of the housing wall (GW) via the carrier (T).

Description

[0001] The invention relates to a housing assembly comprising a housing frame and a support for a measuring device for measuring a measurand. Furthermore, the invention relates to a measuring device for measuring a measurand with such a housing.

[0002] Measuring devices are particularly widespread and well-known in process measurement technology. For example, magnetic-inductive flowmeters for volumetric flow measurement utilize the principle of electrodynamic induction and are known from numerous publications. Charge carriers in the medium moving perpendicular to a magnetic field induce a measuring voltage in measuring electrodes arranged essentially perpendicular to the direction of flow of the medium and perpendicular to the direction of the magnetic field. The measuring voltage induced in the measuring electrodes is proportional to the flow velocity of the medium averaged over the cross-section of the measuring tube, i.e., proportional to the volume flow. If the density of the medium is known, the mass flow in the pipeline or measuring tube can be determined.The measuring voltage is usually tapped via a pair of measuring electrodes which are arranged with respect to the coordinate along the measuring tube axis in the area of ​​maximum magnetic field strength and where consequently the maximum measuring voltage is to be expected.

[0003] Document DE102016110050A1 teaches a plug-in connection for simple and secure electrical contacting of a printed circuit board located inside a housing part of a measuring device, which can be used in a variety of field device types. The plug-in connection disclosed comprises, among other things, a housing assembly with a printed circuit board secured in a conductive housing wall by means of a clamp connector, with the printed circuit board being grounded by a contact element of the housing part.

[0004] Document DE102016124975A1 teaches a housing for a flowmeter and a flowmeter, wherein the housing comprises a housing body with a housing wall and is formed from two enclosing wall elements. The housing is configured to accommodate a measuring tube, wherein the housing wall has openings for mounting a measuring tube. The housing further comprises a spacer to ensure stabilization of the wall elements, which can also be used to support the measuring and operating circuit.

[0005] The problem with the housing according to the state of the art is that, due to the necessarily compact design, there is little space available for routing cables for the discharge of electrical currents from the electronics into the ground.

[0006] The invention therefore has the object of proposing a housing and a flow meter with a housing which circumvents the aforementioned problem.

[0007] The invention solves the problem by a housing assembly according to independent claim 1.

[0008] The housing assembly according to the invention with integrated electrical ground connection for a measuring device comprises: a housing chamber with a housing wall that is at least partially electrically conductive; a measuring and operating circuit with a printed circuit board; an at least partially electrically conductive carrier with a main body having a material thickness of at least 0.5 mm and at most 3 mm; wherein the carrier is electrically conductively connected to the housing wall; wherein the carrier comprises at least one strip-shaped support body that continues from the main body; wherein the at least one support body is folded in on itself in a U-shape, so that the at least one support body forms a contact region that has a support thickness corresponding to twice the material thickness of the main body; wherein the contact region has a through-opening with a continuous internal thread;wherein the at least one support body is connected to the circuit board by at least one contact surface; wherein the connection between the support body and the at least one contact surface is formed by means of at least one screw; wherein an electrically conductive connection exists between the at least one contact surface and the contact area, so that the measuring and operating circuit, in particular the circuit board, is connected to the potential of the housing wall via the carrier.

[0009] In a further development of the housing assembly according to the invention, the at least one screw is provided with a loosening lock to increase a loosening torque; wherein the loosening lock comprises a coating of the external thread of the at least one screw, in particular with a dry adhesive.

[0010] In a further development of the housing assembly according to the invention, the plate thickness of the main body is more than 1 mm and / or less than 2 mm.

[0011] In a further development of the housing assembly according to the invention, the carrier has at least one strip-shaped and curved connecting element extending from the main body; wherein the carrier is galvanically connected to the housing wall via the at least one connecting element.

[0012] In a further development of the housing assembly according to the invention, the carrier is integrally connected to the housing wall via the at least one connecting element by joining, in particular resistance spot welding.

[0013] A further development of the housing assembly according to the invention comprises at least one electrode arranged on at least one of the contact surfaces of the printed circuit board; wherein the contact surface has a through-hole; wherein the at least one screw protrudes through the through-hole and engages in the internal thread of the through-hole of the contact region; wherein the contact surface of the printed circuit board is connected to the contact region of the support body by means of the at least one screw such that the at least one electrode is electrically conductively connected to the support body; wherein the at least one electrode is electrically conductively connected to the housing wall.

[0014] In a further development of the housing assembly according to the invention, an elastic body, in particular a clamping washer, is inserted between the contact area of ​​the support body and the screw head of at least one screw for elastically clamping the circuit board.

[0015] In a further development of the housing assembly according to the invention, the carrier has three strip-shaped support bodies which extend from the main body.

[0016] The measuring device according to the invention for measuring a measured variable of a medium in a measuring tube comprises a housing assembly according to the invention; a measuring tube for guiding the medium; wherein the measuring tube extends through passages arranged in the housing wall.

[0017] A further development of the measuring device according to the invention further comprises at least one magnetic coil; wherein the measuring tube has two measuring electrodes; wherein the at least one magnetic coil and the two measuring electrodes are connected to the measuring and operating circuit.

[0018] The invention has the advantage that, due to the screw connection between the carrier and the housing wall, a permanent and reliable ground connection of the circuit board, and in particular of the components arranged on the circuit board, is possible without additional cabling. Another advantage is that, due to the folded support bodies, the carrier has a material thickness of half the minimum screw-in depth of 1 to 6 mm required by the screws connecting the carrier and the component.

[0019] This is advantageous because a carrier with a thinner material thickness can be used, making it easier to shape and overall cheaper to manufacture. Another advantage is that the bent connecting elements can be firmly bonded using resistance spot welding, which allows for decoupling the temperature of the carrier from that of the housing wall. Another advantage is that the housing wall can be robustly connected to the measuring device thanks to the support bodies and connecting elements according to the invention.

[0020] The invention is explained with reference to the following figures. It shows: Fig. 1 a side view of an embodiment of the carrier according to the invention; Fig. 2 a front view of the carrier according to the invention; Fig. 3 a rear view of the embodiment of the housing assembly according to the invention; Fig. 4 an embodiment of the housing assembly according to the invention. Fig. 5 an embodiment of the measuring device according to the invention.

[0021] The Fig. The side view of an embodiment of the carrier T according to the invention shown in Figure 1 shows the main body H with the strip-shaped support bodies AK, which are folded inward and thereby form a two-layer region in which an internal thread IG is arranged and which has a connection surface AF. Furthermore, the main body has a plurality of strip-shaped connection points AS, which are curved with respect to a reference plane defined by the main body.

[0022] The Fig. The front view of the carrier T according to the invention shown in Figure 2 shows the main body H made from approximately 1.5 mm thick sheet metal, which has three strip-shaped support bodies AK and four strip-shaped and bent connecting elements VE. The electrically conductive support bodies AK are bent into a U-shape and thus form a contact area with a thickness of approximately 3 mm. One contact area has a through-hole with an internal thread to accommodate a screw. The electrically conductive connecting elements VE are intended to be connected to the housing wall GW by resistance spot welding, thereby creating an electrically conductive connection between the main body and the housing wall.

[0023] The Fig. The exemplary embodiment of the housing assembly shown in Figure 3 shows a rear view of the main body H of the carrier T connected to the housing wall GW. The connecting bodies AK, which continue in strips from the main body H, are bent in a U-shape to form the contact area KB, which is connected to the printed circuit board LP by means of the screw S. At least one electrode EL is arranged on the printed circuit board LP in such a way that a conductive connection is created between the electrically conductive contact area KB of the connecting body AK and the electrode EL by means of the screw S. The printed circuit board shown has an exemplary arrangement of components BT, which include filter capacitors and electronic components.

[0024] The Fig. The embodiment of the housing assembly according to the invention shown in Figure 4 comprises a printed circuit board LP, which is connected to the carrier T by means of the at least one screw S via the contact areas KB of the at least one connecting body AK. The printed circuit board LP shown has an exemplary arrangement of components BT, which include electronic components, for example, resistors, transistors, diodes, integrated circuits, and capacitors. The carrier T is integrally connected to the housing wall GW by means of the strip-shaped, curved connecting elements VE.

[0025] The Fig. The embodiment of a measuring device according to the invention shown in Figure 5 shows the housing wall GW with the feedthrough DF, in which the measuring tube MR is arranged. The sensor module is enclosed by the housing chamber GW. List of reference symbols GK housing chamber GW housing wall LP circuit board T carrier H Main body KB Contact Area KF contact surface S screw IG internal thread AK support body KB Contact Area VE connecting element EK Elastic Body BT components EL electrode GH housing assembly MR measuring tube ME Mediums SM sensor module DF implementation

Claims

[1] Housing assembly with integrated electrical ground connection for a measuring instrument, comprising: • a housing wall that is at least partially electrically conductive (GW); • a housing chamber (GK) enclosed by the housing wall (GW); • a measuring and operating circuit with a printed circuit board (PCB), wherein the PCB has at least one contact surface (SPF); • a carrier (T) that is at least partially electrically conductive, with a main body (H) having a material thickness of at least 0.5 mm and at most 3 mm; • wherein the carrier (T) is electrically connected to the housing wall (GW); • wherein the support (T) comprises at least one strip-shaped support body (AK) extending from the main body (H); • wherein the at least one support body (AK) is folded in a U-shape, so that the at least one support body (AK) forms a contact area (KB) which has a support thickness corresponding to twice the material thickness of the main body (H); • wherein the contact area (KB) has a through-hole with a continuous internal thread (IG); • wherein the contact area (KB) of the at least one support body (AK) is connected to the at least one contact surface (KF) of the printed circuit board (LP) by means of at least one screw (S); • wherein an electrically conductive connection exists between the at least one contact surface (KF) and the contact area (KB), so that the measuring and operating circuit, in particular the printed circuit board (LP), is at the potential of the housing wall (GW) via the carrier (T). [2] Housing assembly according to claim 1, • wherein at least one screw (S) is provided with a locking device to increase the loosening torque; • wherein the anti-loosening device comprises a coating of the external thread of the at least one screw (S), in particular with a dry bonding. [3] Housing assembly according to one of claims 1 or 2, • where the plate thickness of the main body (H) is more than 1 mm and / or less than 2 mm. [4] Housing assembly according to any one of claims 1 to 3, • wherein the support (T) has at least one strip-shaped and curved connecting element (VE) extending from the main body (H); • wherein the carrier (T) is galvanically connected to the housing wall (GW) via the at least one connecting element (VE). [5] Housing assembly according to claim 4, • wherein the carrier (T) is materially connected to the housing wall (GW) via the at least one connecting element (VE) by joining, in particular resistance spot welding. [6] Housing assembly according to any one of claims 1 to 5, • wherein at least one electrode (EL) is arranged on at least one of the contact surfaces (KF) of the printed circuit board (LP); • wherein the contact surface (KF) has a through hole; • wherein at least one screw (S) protrudes through the through hole and engages in the internal thread (IG) of the through hole of the contact area (KB); • wherein the contact surface (KF) of the printed circuit board (LP) is connected to the contact area (KB) of the support body (AK) by means of at least one screw (S) in such a way that the at least one electrode (EL) is electrically conductively connected to the support body (AK); • whereby at least one electrode is electrically connected to the housing wall (GW). [7] Housing assembly according to claim 6, • wherein an elastic body (EK), in particular a clamping washer, is clamped between the contact area (KB) of the support body (AK) and the screw head of the at least one screw (S) for the elastic clamping of the printed circuit board (LP). [8] Housing assembly according to any one of claims 1 to 7, • wherein the carrier (T) has three strip-shaped support bodies (AK) extending from the main body (H). [9] Measuring instrument for measuring a quantity of a medium in a measuring tube, comprising: • a housing assembly (GH) according to any one of claims 1 to 8; • a measuring tube (MR) for guiding the medium (ME); • wherein the measuring tube (MR) extends through feedthroughs (DF) arranged in the housing wall (GW). [10] Measuring device according to claim 9, further comprising: • at least one magnetic coil; • wherein the measuring tube (MR) has two measuring electrodes; • wherein the at least one magnetic coil and the two measuring electrodes are connected to the measuring and operating circuit (MB).

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