Housing assembly for a measuring device, and measuring device

Abstract

The invention relates to a housing assembly having a ground connection for a measuring device, comprising: a housing chamber (GK) having a conductive housing wall (GW); a measuring and operating circuit having a printed circuit board (LP); a conductive carrier (T) having a main body (H) with a material thickness between 0.5 and 3 mm and being conductively connected to the housing wall (GW); wherein the carrier (T) comprises a plurality of strip-shaped support bodies (AK) which continue from the main body (H) and which are bent in on themselves in a U-shaped manner such 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 way of a contact surface (KF); wherein the support bodies (AK) and the contact surface (KF) are connected by means of screws (S); wherein a conductive connection exists between the contact surface (KF) and the contact region (KB) such that the measuring and operating circuit, in particular the printed circuit board (LP), lies on the potential of the housing wall (GW) via the carrier (T).

Description

[0001] Housing assembly for a measuring instrument and measuring instrument

[0002] The invention relates to a housing assembly comprising a housing frame and a support for a measuring instrument for measuring a measurand. The invention further relates to a measuring instrument for measuring a measurand with such a housing.

[0003] Measuring instruments 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 described in numerous publications. Charge carriers of the medium moving perpendicular to a magnetic field induce a measuring voltage in measuring electrodes arranged essentially perpendicular to the flow direction of the medium and perpendicular to the direction of the magnetic field. The measuring voltage induced in the measuring electrodes is proportional to the average flow velocity of the medium across the cross-section of the measuring tube, i.e., proportional to the volumetric flow rate. If the density of the medium is known, the mass flow rate in the pipeline or measuring tube can be determined.The measuring voltage is usually tapped via a pair of measuring electrodes which are arranged in the area of ​​maximum magnetic field strength with respect to the coordinate along the measuring tube axis and where the maximum measuring voltage is consequently to be expected.

[0004] German patent application DE102016110050A1 discloses a plug connection for the simple and safe electrical contacting of a printed circuit board located inside the housing of a measuring instrument, which is usable in a variety of field device types. The disclosed plug connection includes, among other things, a housing assembly with a printed circuit board secured in a conductive housing wall by means of a clamp connector, wherein the printed circuit board is grounded by a contact element of the housing.

[0005] German patent DE102016124975A1 discloses a housing for a flow meter and a flow meter itself, wherein the housing comprises a housing body with a housing wall and is formed from two enclosing wall elements. The housing is designed to accommodate a measuring tube, the housing wall having openings for the storage of a measuring tube. The housing further includes a spacer to ensure the stabilization of the wall elements, which can also be used to support the measuring and operating circuitry.

[0006] The problem with the housing according to the prior art is that, due to the necessarily compact design, little space is available for routing cables for conducting electrical currents from the electronics to the ground. The invention therefore aims to propose a housing and a flow meter with a housing that circumvents this problem.

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

[0008] The housing assembly according to the invention with integrated electrical ground connection for a measuring instrument 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; a carrier that is at least partially electrically conductive 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 extending from the main body; wherein the at least one support body is folded in a U-shape, so that the at least one support body forms a contact area having a contact thickness corresponding to twice the material thickness of the main body; wherein the contact area has a through-opening with a continuous internal thread;wherein the at least one support body is connected to the printed circuit board by means of 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 there is an electrically conductive connection between the at least contact surface and the contact area, so that the measuring and operating circuit, in particular the printed circuit board, is at the potential of the housing wall via the support.

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

[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 support has at least one strip-shaped and curved connecting element extending from the main body; the support is galvanically connected to the housing wall via this at least one connecting element. In another further development of the housing assembly according to the invention, the support is metallurgically connected to the housing wall via this at least one connecting element by joining, in particular resistance spot welding.

[0012] In a further development of the housing assembly according to the invention, at least one electrode is 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 projects through the through-hole and engages in the internal thread of the through-hole of the contact area; wherein the contact surface of the printed circuit board is connected to the contact area of ​​the support body by means of the at least one screw in such a way 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.

[0013] In a further development of the housing assembly according to the invention, an elastic body, in particular a clamping washer, is used between the contact area of ​​the support body and the screw head of the at least one screw for the elastic clamping of the printed circuit board.

[0014] In a further development of the housing assembly according to the invention, the carrier has three strip-shaped support bodies that extend from the main body.

[0015] The measuring device according to the invention for measuring a quantity 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 feedthroughs arranged in the housing wall.

[0016] 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.

[0017] The invention has the advantage that, due to the screw connection between the support and the housing wall, a permanent and reliable ground connection of the printed circuit board, and in particular of the components arranged on the printed circuit board, is possible without additional wiring. A further advantage is that, due to the folded support elements, the support has a material thickness of half the minimum screw-in depth of 1 to 6 mm required by the screws connecting the support and the component. This is advantageous because a thinner support can be used, making it easier to shape and generally more cost-effective to manufacture. A further advantage is that the bent connecting elements can be metallurgically joined by resistance spot welding, which allows the temperature of the support to be decoupled from the temperature of the housing wall.There is also the advantage that the housing wall can be robustly connected to the measuring instrument due to the support bodies and connecting elements according to the invention.

[0018] The invention is explained using the following figures. It shows:

[0019] Fig. 1 shows a side view of an embodiment of the carrier according to the invention;

[0020] Fig. 2 a front view embodiment of the carrier according to the invention;

[0021] Fig. 3 shows a rear view of the embodiment of the housing assembly according to the invention; Fig. 4 shows an embodiment of the housing assembly according to the invention.

[0022] Fig. 5 shows an embodiment of the measuring device according to the invention.

[0023] The side view shown in Fig. 1 of an embodiment of the carrier T according to the invention shows the main body H with the strip-shaped support bodies AK, which are folded inwards and thus form a two-layer area in which an internal thread IG is arranged and which has a connection surface AF. Furthermore, the main body has several strip-shaped connection points AS, which are bent with respect to a reference plane defined by the main body.

[0024] The front view of the embodiment of the carrier T according to the invention, shown in Fig. 2, depicts the main body H, which is made from a sheet approximately 1.5 mm thick and has three strip-shaped support bodies AK and four strip-shaped, curved connecting elements VE. The electrically conductive support bodies AK are U-shaped and thus form a contact area approximately 3 mm thick. One contact area has a through-hole with an internal thread to accommodate a screw. The electrically conductive connecting elements VE are designed to be joined to the housing wall GW by resistance spot welding, thereby creating an electrically conductive connection between the main body and the housing wall.

[0025] The embodiment of the housing assembly shown in Fig. 3 depicts a rear view of the main body H of the support T, which is connected to the housing wall GW. The terminal bodies AK, which extend in strip form 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 such that a conductive connection is created between the electrically conductive contact area KB of the terminal 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.

[0026] The embodiment of the housing assembly according to the invention shown in Fig. 4 comprises a printed circuit board LP, which is connected to the carrier T via the contact areas KB of the at least one terminal body AK by means of at least one screw S. 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 metallurgically connected to the housing wall GW by means of the strip-shaped, curved connecting elements VE.

[0027] The embodiment of a measuring device according to the invention shown in Fig. 5 depicts the housing wall GW with the feedthrough DF, in which feedthrough DF the measuring tube MR is arranged. The sensor module is enclosed by the housing chamber GW.

[0028] Reference symbol list

[0029] GK housing chamber

[0030] GW housing wall LP circuit board

[0031] T-beam

[0032] H Main body

[0033] KB Contact Area

[0034] KF contact surface S screw

[0035] IG internal thread

[0036] AK support body

[0037] KB Contact Area

[0038] VE connecting element EK elastic body

[0039] BT components

[0040] EL electrode

[0041] GH Housing Assembly

[0042] MR measuring tube ME mediums

[0043] SM Sensor Module

[0044] DF Implementation

Claims

Patent 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 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 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) such 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 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).

Images