WO2018114185A1

WO2018114185A1 - Field device having an antenna

Info

Publication number: WO2018114185A1
Application number: PCT/EP2017/080048
Authority: WO
Inventors: Armend Zenuni; Philipp REICHERT; Harald SCHÄUBLE; Lukas Bregler
Original assignee: Endress+Hauser SE+Co. KG
Priority date: 2016-12-20
Filing date: 2017-11-22
Publication date: 2018-06-28
Also published as: DE102016124981A1

Abstract

The invention relates to a field device (1), having a housing (2) and a housing cover (3). The housing cover (3) comprises at least a metal cover main body (31), a non-metal cover cap (32) and an antenna (33, 34), which is arranged in the housing cover (3) below the cover cap (32). By means of the arrangement of the antenna (33, 34) in the housing cover (3) of the field device (1), a wireless interface can be provided according to the invention, on the one hand. On the other hand, by means of the structural division of the housing cover (3) into two parts, adherence to any explosion protection requirements is facilitated: By means of the non-metal cover cap (32), sufficient transmission/reception power of the antenna (33, 34) is ensured, wherein the metal cover main body (31) enables a compact design of the housing cover (3) even if any explosion protection provisions are applied. By means of the integration of the antenna (33, 34) in the housing cover (3), it is also possible to correspondingly retrofit older field devices (1) without an internal wireless communication interface.

Description

Field device with antenna

The invention relates to a field device with a housing and a

Housing cover, wherein the housing cover comprises at least one antenna.

In automation technology, in particular in process automation technology, field devices are often used which serve for detecting and / or influencing process variables. For the detection of process variables, sensors are used which, for example, in

Level gauges, flowmeters, pressure and pressure gauges

Temperature measuring devices, pH redox potential measuring devices,

Conductivity meters, etc. are used. In addition, all those devices are generally referred to as field devices, the

be used close to the process and deliver or process the process-relevant information. Therefore, in the context of the invention, field devices additionally also mean remote I / Os, radio adapters or generally electronic components, which are arranged on the field level. A large number of these field devices are manufactured and sold by Endress + Hauser.

In modern industrial plants, field devices are usually over

Communication networks, such as fieldbuses (Profibus ^® ,

Foundation ^® Fieldbus, HART ^®, etc.) connected to the higher-level units. Usually the parent units are around

Control systems or control units, such as a PLC

(Programmable Logic Controller) or a PLC (Programmable Logic Controller). The higher-level units serve, among other things, the

Process control, process visualization, process monitoring and commissioning of field devices. The measured values acquired by the field devices, in particular by sensors, are transmitted via the respective bus system to one (or possibly several) higher-level unit (s).

In addition, a data transmission from the higher-level unit via the bus system to the field devices is required, in particular for

Configuration and parameterization of field devices as well as control of actuators. In addition to a wired data transmission between the field devices and the parent unit, there is also the possibility of wireless (wireless) data transmission. Especially in the bus systems Profibus®, Foundation Fieldbus® and HART® wireless data transmission via radio is specified. Furthermore, radio networks for sensors are further specified in the IEEE 802.15.4 standard.

To realize a wireless data transmission newer

Field devices, in particular sensors and actuators be realized as a self-sufficient radio field devices. These usually have a wireless

Communication interface with an antenna and optionally a power source as integral components. In this case, the antenna and the current source can be provided in the field device itself or in a radio unit permanently connected to the field device. The power source enables a self-sufficient power supply of the field device.

In addition there is the possibility of field devices without internal wireless

Communication interface through the coupling with at least one

Upgrade wireless adapter to a radio-enabled field device. A corresponding radio adapter is described, for example, in document WO 2005/103851 A1. The wireless adapter is usually connected to a

Communication interface such a field device detachably connected. Via this communication interface, the field device can send the data to be transmitted via the bus system to the radio adapter, which then transmits it via radio to the higher-level unit. Conversely, the radio adapter can receive data via radio and via this

Forward the communication interface to the field device. The supply of the field device with electrical power can be done in such cases via a power supply unit the radio adapter. An appropriate wireless adapter that supports the WirelessHART © protocol will become available

for example, produced and distributed by the Endress + Hauser Group under the name "SWA70".

A framework condition involving the use of radio transmission

Field devices difficult, lies in the encapsulation of field devices Corresponding (metal) housing: The housing protects the field device against process-specific environmental influences such as dust, temperature or corrosive atmosphere. On the other hand, a correspondingly designed housing is absolutely necessary, since the field device (and thus also its components, such as any antennas) must comply with appropriate explosion protection regulations in potentially explosive atmospheres. However, in the case of radio transmission, such a housing inherently reduces the transmission / reception power of the antenna. Effective explosion protection measures with respect to the housing are already known from the prior art. Corresponding regulations are defined in Europe by the EN 60079 series of standards. From this it can be seen that, among other things, pressure encapsulation and encapsulation are used for the explosion-proof encapsulation of electronic components. When using a casting, the standard EN 60079-18 refers to explosion protection type "m", in the case of pressure-resistant

Enclosure according to explosion protection type "d", the standard EN 60079-1 applies.

In addition, the listed explosion protection regulations also affect all those electrical interfaces of the electronic module, through which the module is contactable through the explosion-proof enclosure outwards. Thus, this also applies to

Communication interfaces for the possible connection of radio adapters:

In order to comply with the explosion protection regulations, it is necessary to design these interfaces in such a way that only a limited power or data rate can be transmitted via them.

The invention is therefore based on the object to provide a safe field device with a wireless interface.

The invention achieves this object by means of a field device having a housing and a housing cover. According to the invention, the housing cover comprises at least the following components: a metallic cover body, - a non-metallic lid cap, and

- An antenna which is arranged below the lid cap in the housing cover.

By arranging the antenna in the housing cover of the field device, according to the invention, on the one hand, a wireless interface can be provided. On the other hand, it is by means of the constructive division of the

Housing cover facilitates, any explosion protection regulations

observed:

Due to the non-metallic lid cap a sufficient transmission / reception performance of the antenna is ensured, the metallic lid base body even with the application of any

Explosion protection regulations allows a compact design of the housing cover. The integration of the antenna in the housing cover also makes it possible to use older field devices without internal wireless

Retrofit communication interface accordingly.

For the purpose of further improved transmitting / receiving power of the antenna, it is advantageous if the non-metallic lid cap

is designed dome-shaped, cuboid or conical. In this case, the non-metallic lid cap, for example, by screwing,

Gluing, or pressing be attached to the lid body.

According to the invention it is particularly advantageous if the non-metallic lid cap is made of a plastic, and / or if the lid body is made of aluminum.

A further advantageous embodiment variant of the housing cover according to the invention provides that at least the antenna is encapsulated with a casting, in particular a soft casting (for example SilGel®). In this case, an analogous advantageous variant for realizing the housing cover is to realize the non-metallic housing cover as encapsulation (in addition to or instead of the antenna encapsulation).

In particular, the antenna according to the invention is preferably designed to comply with the usual WLAN frequencies Electromagnetic waves Transmit and / or receive frequencies of 2.4 GHz and / or 5 GHz. Of course, it would be within the meaning of the invention also conceivable, the antenna using other wireless transmission standards on the

appropriate frequencies.

An advantageous embodiment of the invention for realizing the antenna provides that the antenna is configured as a conductor track structure on a printed circuit board. In this case, the geometry of the conductor track structure (designed in particular as a patch structure, conceivable, however, inter alia including corresponding fractal structures) could in turn be adapted to the transmission / reception frequency used in each case. In the case of a conductor track as an antenna substrate, it would also be conceivable that, in addition to the conductor track structure, at least one electronic component for (pre-) processing of the radio signals is arranged on the conductor track.

Of course, any other antennas, such as rod or helix antennas could be used in the context of the invention. In this case, the antenna, for example, by screwing, gluing, or pressing be attached to the lid body.

With regard to the attachment of the housing cover to the housing, an advantageous embodiment provides that the cover body and the housing can be connected to one another by means of a threaded closure. With regard to the electrical contacting of the antenna with the associated electronics unit in the field device to which the antenna is to be connected, there are several possibilities according to the invention: In addition to a possible

Cable connection, it is especially advantageous if a connector, in particular a coaxial connector (for example, a MMCX or SMA connector), is provided for electrically contacting the antenna with the electronics unit. In such an embodiment, in the event that the base body and the housing by means of

Threaded closure can be connected together, a special

advantageous embodiment possibility to design the connector so and arrange that the connector by means of Screwing the housing cover is electrically contacted to the housing. This could for example be implemented by the

Plug connection in relation to the threaded closure is arranged substantially centrally in the field device. As a result, the electrical contacting of the antenna in the field device and the attachment of the housing cover take place simultaneously in one step.

With regard to explosion safety of the field device

According to the invention, the possibility of explosion-proof design of the housing and / or the housing cover, in particular according to the standard series EN 60079. Regarding the housing cover, this is especially the

Wall thickness of the lid base body and the lid cap to be sized accordingly. Similarly, the attachment of the lid cap on

Cover base body and the connection of the housing cover to the housing in accordance with standards.

With reference to the following figure, the invention will be explained in more detail. 1 shows a housing of a field device with a device according to the invention

Housing cover.

In Fig. 1, a housing 2 of a field device 1, for example one

Level or pressure gauge, shown. On the housing 2, a housing cover 3 is arranged. In this case, the housing cover 3 by means of a threaded closure 4, consisting of a housing cover-side internal thread and a corresponding external thread on the housing 2 is attached. According to the invention the housing cover 3 is in two parts, with a metallic lid base body 31 and a non-metallic lid cap 32 constructed. Below the lid cap 32, an antenna 33, 34 is disposed in the housing cover 3. Here, the lid cap 32 in the embodiment shown in favor of the emission or reception characteristic of the antenna 33, 34 designed kuppeniförmig. In the exemplary embodiment shown, the antenna 33, 34 is based on a printed conductor structure 33 which is arranged on a printed circuit board 34. The

Printed circuit board 34 is arranged perpendicular to the base surface of the dome-shaped lid cap 32. Furthermore, for contacting the

Conductor 33 on the circuit board 34, a coaxial connector 331 is arranged. At the outer shielding connection of the coaxial connector 331, the conductor track structure 33 is designed on both sides as an approximately square patch. At the central signal terminal of the coaxial connector 331, the conductor track structure 33 is realized as an angled conductor track. Of course, it is within the meaning of the invention possible to arrange the conductor track structure on both sides of the circuit board 34 and thus the emission or

Reception characteristics continue to improve.

In the housing 2, an electronics unit 21 is arranged, with which the antenna 33, 34 is connected. The electronic unit 21 serves as a transmission /

Receive unit, which generates the respective transmission signals, for example according to the standard IEEE 802.15.4, and processes the corresponding received signals. It is not relevant within the scope of the invention whether the electronic unit 21 additionally serves as a control / evaluation unit for the actual function of the field device 1, that is to say for example for filling level or pressure measurement by means of corresponding sensors.

To connect the antenna 33, 34 with the electronics unit 21, a coaxial socket 21 1 corresponding to the coaxial plug 331 is arranged centrally in the housing 2 in relation to the threaded closure 4. In this case, the coaxial jack 21 1 and the coaxial connector 331 in the one shown in Fig. 1

Embodiment arranged so that the electrical contacting of the antenna 33, 34 in the field device 1 and attaching the housing cover 3 on the housing 2 takes place simultaneously in a working step. LIST OF REFERENCE NUMBERS

field device

casing

housing cover

thread lock

Electronics unit

Lid body

Cover cap

Conductor structure

circuit board

Coaxial socket

Coaxial connector

Claims

claims

1 . Field device with a housing (2) and a housing cover (3), wherein the housing cover (3) comprises at least the following components:

A metallic lid base (31),

a non-metallic lid cap (32), and

- An antenna (33, 34) below the lid cap (32) in

Housing cover (3) is arranged.

2. Field device according to claim 1, wherein the non-metallic lid cap (32) is designed dome-shaped, cuboid or conical.

3. Field device according to claim 1 or 2, wherein the non-metallic lid cap (32) by screwing, gluing, or pressing on the lid base body (31) is attached.

4. Field device according to at least one of claims 1 to 3, wherein the non-metallic lid cap (32) is made of a plastic, and / or wherein the lid base body (31) is made of aluminum.

5. Field device according to at least one of claims 1 to 4, wherein at least the antenna (33, 34) is encapsulated with a potting, in particular a soft casting.

6. Field device according to at least one of the preceding claims, wherein the antenna (33, 34) is designed to transmit and / or receive electromagnetic waves with frequencies of 2.4 GHz and / or 5 GHz.

7. Field device according to at least one of the preceding claims, wherein the antenna (33) is designed as a conductor track structure (33) on a printed circuit board (34).

8. Field device according to at least one of the preceding claims, wherein the antenna (33, 34) by screwing, gluing, or pressing on the lid base body (31) is attached.

9. Field device according to at least one of the preceding claims, wherein the cover base body (31) and the housing (2) by means of a

Threaded closure (4) are connectable to each other.

10. Field device according to at least one of the preceding claims, wherein in the housing (2) an electronics unit (21) is arranged, and wherein a plug connection (331, 21 1), in particular a coaxial connector, for electrically contacting the antenna ( 33, 34) is provided with the electronics unit (21).

1 1. Field device according to claim 10, wherein the plug connection (331, 21 1) for the case that the base body (31) and the housing (2) by means of

Threaded closure (4) are connectable to each other, the connector (331, 21 1) configured and arranged such that the plug connection (331, 21 1) by means of screwing the housing cover (3) on the housing (2) is electrically contacted.

12. Field device according to at least one of the preceding claims, wherein the housing (2) and / or the housing cover (3) explosion-proof, in particular according to the series EN 60079, are designed / is.