DE102017126127A1 - Radar-based level gauge - Google Patents

Abstract

The invention relates to a radar-based level measuring device for attachment to a container (2) with a round terminal (21, 21 '), wherein the round terminal (21, 21') has a predefined end contour (210). For this purpose, the level measuring device (1) comprises a lid (11) with a fastening means (110, 110 '), by means of which the lid (1) can be fastened to the container (2). In this case, the lid (11) is designed so that in the attached state, at least one contact surface of the lid (11) adjoins the end contour (210). For level measurement, a transmitting / receiving unit (12) is arranged in the lid (11) to emit radar-based transmission signals (S _HF ) in the direction of the filling material (3) and based on the received signals (E _HF ) the level (L) of the filling material (3) in the container (2) to determine. According to the invention, the cover (11) has a height (W _max ) of a maximum of 60 mm in relation to its contact surface. In this way, the lid (11) can be designed, for example, according to the dimensions of a blind flange for flange connections (21). Thus, the level gauge (1) can be mounted to save space on the container (2).

Description

The invention relates to a radar-based level gauge for attachment to a container with a round terminal, such as a flange, clamp or screw.

In process automation technology, field devices are often used to detect or influence process variables. For the detection of process variables, sensors are used which are used, for example, in level gauges, flowmeters, pressure and temperature measuring devices, pH redox potential measuring devices, conductivity meters, or comparable devices. They record the corresponding process variables, such as level, flow, pressure, temperature, pH, redox potential or conductivity. Various types of such field device types is manufactured and distributed by the company Endress + Hauser.

Non-contact measuring methods have become established for level measurement of products in containers since they are robust and require little maintenance. The term "container" in the context of the invention, non-self-contained containers, such as pools, lakes or flowing waters understood. Another advantage of non-contact measuring methods is the ability to measure the level virtually continuously. In the field of continuous level measurement, radar-based measuring methods are therefore predominantly used (in the context of this patent application, "radar" is defined as signals or electromagnetic waves with frequencies between 0.03 GHz and 300 GHz). The two common measurement principles here are the pulse-transit time principle (also known by the term "pulse radar") and the FMCW principle ("Frequency Modulated Continuous Wafe").

Level gauges are usually housed in universal field device enclosures designed for the requirements of a wide range of field device types. Accordingly, the housings are designed to meet the widest possible requirements. These relate in particular to electromagnetic compatibility ("EMC"), explosion safety (as defined, for example, in the EN 60079 series of standards), corrosion resistance or impact resistance. In addition, the enclosures usually also include several interfaces such as displays, keyboards or various cable connections. A corresponding housing for field devices, for example, in the international publication WO 2014037256 A1 shown.

Due to these extensive requirements for field device housing results in practice a comparatively space-intensive housing, which is not mountable in tight installation locations lack of space. The invention is therefore based on the object to provide a compact level gauge.

• - Einen Deckel mit
  • ○ einem Befestigungsmittel, mittels dem der Deckel am Behälter befestigbar ist.
  Der Deckel ist dabei so ausgelegt, dass im befestigten Zustand zumindest eine Kontaktfläche des Deckels an die Endkontur des Rundanschlusses anschließt, wobei der Deckel in Bezug zur Kontaktfläche eine Höhe von maximal 60 mm aufweist, und
• - eine im Deckel angeordnete Sende-/Empfangs-Einheit, die ausgelegt ist, um radar-basierte Sendesignale in Richtung des Füllgutes auszusenden und nach Reflektion an der Füllgutoberfläche anhand von entsprechenden Empfangssignalen den Füllstand eines im Behälter befindlichen Füllgutes zu bestimmen.

The invention solves this problem by a radar-based level measuring device, which can be fastened to a container with a round terminal, wherein the round terminal has a predefined end contour. According to the invention, the fill level measuring device comprises:

• - a lid with
  • ○ a fastening means by means of which the lid is attachable to the container.
  The cover is designed so that in the attached state, at least one contact surface of the lid adjoins the end contour of the round terminal, wherein the cover has a height of a maximum of 60 mm with respect to the contact surface, and
• - An arranged in the lid transmitting / receiving unit which is designed to emit radar-based transmission signals in the direction of the contents and to determine the level of a filling material located in the container after reflection on the Füllgutoberfläche based on corresponding received signals.

Due to the small height of the lid, the level measuring device according to the invention can thus be used for applications that require a flat structure of the level gauge, especially with regard to the installation height above the container. This concerns, for example, level measurement at a housing opening of a square IBC tank, which still has to be stackable despite an attached level gauge. Notwithstanding this, based on the level measuring device according to the invention, a positive-pressure closure of the round terminal can be achieved, since the lid can be designed, for example, according to the dimensions of a blind flange. Thus, the lid can potentially be designed to seal the interior of the container at least according to the nominal pressure level PN 2.5 overpressure resistant.

As a transmitting / receiving unit for the level measuring device according to the invention, it is particularly suitable if the transmitting / receiving unit is designed to emit the transmission signals at a frequency of at least 75 GHz. In this case, the transceiver unit can be made very compact, since corresponding electronic components at such frequencies (and possibly also the receipt of corresponding received signals) can be realized based on a semiconductor integrated circuit. In addition to the advantage of compactness, there is also the advantage at high frequencies that a higher absolute bandwidth can be used at higher frequencies. This in turn achieves a higher resolution or accuracy of the level measurement. This is an important requirement in particular for level measurement since, depending on the application, a highly accurate knowledge of the filling level is required.

Especially at radar frequencies above 75 GHz, it makes sense according to the invention if the cover comprises a quasi-optical lens for bundling at least the transmission signals. This can be dispensed with space-consuming (horn) antennas. In the context of the invention, the term "quasi-optical lens" is analogous to optical lenses to materials with which electromagnetic waves in the radar spectral range [0.3 to 300 GHz] are refracted, and by means of which a defined one is formed with appropriate shaping Bundling or deflection of the beam path can be achieved. Especially when implementing a quasi-optical lens (using correspondingly high radar frequencies), the level gauge according to the invention can be designed so that it can be attached to a round terminal with an inner diameter of at most 200 mm, in particular less than 65 mm. Particularly advantageous is the attachment to a round connector with an inner diameter of 50 mm (DN50 / 2) or 39 mm (DN40 / 1½)

For the purposes of the invention, the cover can be adapted to various types of round connections: Conceivable, inter alia, flange connections, screw terminals or terminal connections (better known under the English term "clamp connection", such as Tri-Clamp ®). In response, the fastener of the cover is to be designed as a flange to secure the level gauge to a corresponding flange or clamp connection of the container. In order to fix the level gauge to a corresponding screw connection of the container, the fastening means must be designed accordingly as internal thread or external thread.

In connection with the adaptability of the cover according to the invention to various round connections, the term "final contour" generally refers to that surface or planar contour of the round connection which faces the container outer side (in relation to the imaginary axis of the round connection). Accordingly, in the case of a flange or clamp connection, the end contour of the flange face of the container-side flange faces the lid-side flange. If the round connection is realized as a screw connection, the final contour is again that planar contour of the round connection which, when the cover is completely screwed, functions as its end stop.

An advantageous implementation of the invention is to couple the dimension of the height of the lid (taking into account the maximum height of 60 mm) to the inner diameter of the round terminal. A possible coupling may depend on the type of round connection. In the case of a flange connection, for example, the height can be coupled to the inner diameter of the flange in accordance with standard EN 1092-01 / 01 A for flange connections. The following table shows an excerpt from the standard and illustrates the local coupling of the (flange) height to the flange inner diameter: Flange designation (DN) Inside diameter (mm) Height (mm) 600 616.5 55 150 170.5 24 50 61.5 19

It goes without saying that the lid according to the invention can also be designed in any other coupled dimension from inner diameter to height, which is shown in this standard. When designing the cover on a terminal connection, the coupled dimension applies equally to the standards DIN 32676.

• 1: eine schematische Darstellung der Anordnung von Radar-basierten Füllstandsmessgeräten an einem Behälter,
• 2: eine erste Ausführungsvariante des erfindungsgemäßen Füllstandsmessgerätes für Flanschanschlüsse,
• 3: eine zweite Ausführungsvariante des erfindungsgemäßen Füllstandsmessgerätes für Schraubanschlüsse mit Innengewinde, und
• 4: eine dritte Ausführungsvariante des erfindungsgemäßen Füllstandsmessgerätes für Schraubanschlüsse mit einem Außengewinde.

The invention will be explained with reference to the following figures. It shows:

• 1 : a schematic representation of the arrangement of radar-based level gauges on a container,
• 2 : a first embodiment variant of the level measuring device according to the invention for flange connections,
• 3 A second variant of the filling level measuring device according to the invention for screw connections with internal thread, and
• 4 A third variant of the filling level measuring device according to the invention for screw connections with an external thread.

For a general understanding of the invention is in 1 a typical arrangement of a radar-based level gauge 1 on a flange connection 21 a container 2 shown. Inside the container 2 there is a filling material 3 whose level L through the level gauge 1 is to be determined. For this purpose, the level gauge 1 in a known installation height H above the contents 3 on the container 2 appropriate. In this case, the container 2 depending on the application more than 100 m high.

The level gauge 1 is like that on the container 2 aligned and fixed that there are radar-based transmission signals S _HF in the direction of the surface of the filling 3 sending out. As a result of the reflection of the transmission signal S _HF The filling level measuring device receives at the product surface 1 a corresponding received signal E _HF as a function of the distance d = h - L to the product surface after a corresponding running time. In level gauges according to the pulse radar principle, it is the transmission signal S _HF possibly radar pulses emitted periodically, so that on the basis of the pulse transit time between transmission of the pulse-shaped transmission signal S _HF and receiving the likewise pulsed received signal E _HF immediately the distance and thus the level L can be determined.

In the case of FMCW radar, it is the transmission signal S _HF a continuous radar signal, but with a time-modulated frequency. Accordingly, the duration and thus the distance or the level L upon implementation of the FMCW method based on the instantaneous frequency difference between the currently received receive signal E _HF and the simultaneously transmitted transmission signal S _HF be determined.

As a rule, the level gauge is 1 via an interface, such as "PROFIBUS", "HART" or "Wireless HART" with a higher-level unit 4 , such as As a process control system connected. This can be the level value L be transmitted, for example, if necessary, on the container 2 control existing inflows or outflows. But it can also provide other information about the general operating condition of the level gauge 1 be communicated.

This in 1 illustrated level gauge 1 is in a housing typical for field devices 11 * accommodated. Due to the universal design of the housing 11 * For various field device types, it therefore has comparatively massive dimensions. For this reason, the housing protrudes 11 * in practice at least 30 cm above the flange connection 21 of the container 2 out. The corresponding space above the container 2 is at the place of use for the level gauge 1 kept clear. However, in certain applications, such as stackable IBC tanks, this space can not be maintained, leaving a level gauge 1 with a conventional housing 11 * can not be used here.

This can be achieved by the level gauge according to the invention 1 , whose basic structure in 2 . 3 and 4 is overcome. In this case, the level measuring device according to the invention 1 on the container 2 arranged in the same manner as is done in the prior art.

How out 2 shows, is the level measuring device according to the invention 1 in the form of a lid 11 designed, which the round connection 21 . 21 ' of the container 2 , optionally overpressure, closes. Characteristic here is that the lid 11 in relation to the contact surface of the lid 11 , which in the attached state at the appropriate final contour 210 of the round connection 21 . 21 ' is applied, with a maximum height Wmax of 60 mm is dimensioned. If the round connection as flange connection 21 is designed ( 2 ), corresponds to the final contour 210 the planar flange surface of the container-side flange, which faces the lid-side flange. Thus, the level gauge 1 be modeled, for example, the shape of a blind flange. This is the height W _max of the lid 11 depending on the flange size to the respective inner diameter D _l or to couple, as it at least in the European area in the standard EN 1092-01 / 01 A is defined. In particular, in this geometry, a corresponding overpressure resistance of the lid 11 to effect is the lid 11 from a suitable material, such as. Stainless steel to manufacture.

The integration of the transmitting / receiving unit is favored 12 inside the lid 11 in that the transmitting / receiving unit 12 is designed to receive the radar-based transmission signals S _HF with a frequency of 75 GHz or higher. On the one hand, the transceiver unit 12 be dimensioned very small in this case, since the RF generation at such frequencies (and possibly also the receipt of corresponding received signals E _HF ) can be realized on the basis of a single semiconductor device. On the other hand, especially at over 75 GHz, no space-intensive horn antenna is required, as is customary at lower frequencies of, for example, 26 GHz. Instead of an antenna, as with the in 2 . 3 and 4 shown embodiments, the lid 11 with a quasi-optical lens 111 be designed by means of the desired bundling of the transmission signal S _HF conditions 3 (And due to the bidirectional mode of action and the bundling of the received signal E _HF gene transmitting / receiving unit 12 ) is set. As a material, PTFE, for example, can be used for this purpose.

A reduced dimension of the height W _max can also be achieved when wired power supply or wired communication of the transmitting / receiving unit 12 is waived. This can be compensated, for example, by integration of a radio module, for example according to the WLAN standard. In the wireless case, the power supply can be done, for example. On the basis of a rechargeable battery, wherein for reloading an inductive coupling can be provided.

3 illustrates that the erfindungsgenmäße level gauge 1 not only compatible with a flange connection 21 (or a structurally related terminal connection), but also, for example, compatible with a screw connection 21 ' In the embodiment variant shown there, the cover comprises 11 an external thread 110 ' leading to an internal thread on the container 2 corresponds. Here is the lid 11 designed so that it passes over the internal thread and thus over the inner diameter D _{l of} the screw connection 21 ' survives. This will ensure that the lid 11 also has a suitable contact surface in this embodiment, when screwing the lid 11 an end stop relative to the container-side end contour 210 forms.

Instead of in 3 embodiment shown, it is also conceivable, the lid according to the invention 11 suitable for a screw connection 21 ' to realize with a container-side external thread. This embodiment is in 4 shown. Such an embodiment can be used, for example, to the fill level measuring device according to the invention 1 on a union fitting for food and chemicals according to the DIN standard 11851 to fix. In addition, the level gauge could 1 be used in this embodiment to an IBC tank, as IBC tanks on top of the container 2 have a corresponding opening with an external thread.

LIST OF REFERENCE NUMBERS

1

Radar-based level gauge

2

container

3

filling

4

Parent unit

11

cover

11 *

casing

12

Transmit / receive unit

21

flange

21 '

Screw

110

flange

110 '

thread

111

Quasi-optical lens

210

final contour

D _i

Inner diameter

d

distance

E _HF

receive signals

H

installation height

L

level

S _HF

send signal

W _max

Height of housing

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2014037256 A1 [0004]

Claims (8)

Radar-based level gauge, which is fastened to a container (2) with a round terminal (21, 21 '), wherein the round terminal (21, 21') has a predefined end contour (210), comprising: - a lid (11) with ○ a Fastening means (110, 110 '), by means of which the lid (1) can be fastened to the container (2), wherein the lid (11) is designed such that in the fastened state at least one contact surface of the lid (11) against the final contour (210 ), and wherein the cover (11) has a height (Wmax) of a maximum of 60 mm with respect to the contact surface, - a transmitting / receiving unit (12) arranged in the cover (11) and designed to radar based transmission signals (S _HF ) in the direction of the contents (3) to send out and after reflection on the Füllgutoberfläche based on corresponding received signals (E _HF ) to determine the level (L) of a container (2) filling material (3). Level gauge after Claim 1 wherein the transceiver unit (12) is designed to emit the transmission signals (S _HF ) at a frequency of at least 75 GHz. Level gauge after Claim 1 or 2 wherein the lid (11) comprises a quasi-optical lens (111) for focusing at least the transmission signals (S _HF ). Level gauge after Claim 1 . 2 or 3 , wherein the fastening means (110, 110 ') is designed so that the level measuring device (1) to a round terminal (21, 21') with an inner diameter (D _i ) of a maximum of 200 mm, in particular 65 mm can be fastened. Level gauge according to one of Claims 1 to 4 in that the fastening means is designed as a flange (110) in order to fasten the level gauge (1) to a corresponding flange connection (21) of the container (2). Level gauge according to one of Claims 1 to 4 in that the fastening means is designed as an internal thread (110 ') or external thread in order to fasten the level gauge (1) to a corresponding screw connection (21') of the container (2). Level gauge according to one of Claims 1 to 4 , wherein the fastening means (110) is designed so that the level measuring device (1) can be fastened to a clamping connection of the container (2). Level gauge according to at least one of the preceding claims, wherein the lid (11) is designed to seal the interior of the container (2) at least in accordance with the nominal pressure stage PN 2.5 overpressure resistant.

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