Field device with radar sensor and vibration limit level sensor and method of operation thereof

Abstract

The invention relates to a field device (10) comprising a radar sensor for measuring a fill level and a vibration limit level sensor, wherein the radar sensor has a transmitting and receiving unit and an antenna, wherein the vibration limit switch has a drive unit (34) and a mechanical oscillator (24) connected thereto, wherein the antenna (14) simultaneously serves as the mechanical oscillator (24). The invention also relates to a method for operating the field device (10).

Description

Technical Field

[0001] This invention relates to a field device according to claim 1, comprising a radar sensor for measuring the level of fill material and a vibration limit level sensor. The invention also relates to a method for operating the field device according to claim 10. Background Technology

[0002] In process automation technology, field devices are widely used to detect and / or influence process variables. Field devices can specifically include actuators, sensors, data collectors (data loggers), and measurement transducers. Here, "field" refers to the area outside the control room. These field devices are typically connected to higher-level units, such as management systems or control units. These higher-level units are used for process control, process visualization, and / or process monitoring.

[0003] Field devices known in the prior art typically include a housing, a sensor unit, and an electronic module, which is arranged within the housing and contains sensor electronics. The measured process variable is typically evaluated, and the evaluation results can be used, for example, to generate switching commands and / or proportional analog or digital output variables, or to display physical characteristics or process variables.

[0004] Examples of field equipment include fill level measurement devices that operate on radar principles. Various designs are known for fill level measurement devices used to determine and / or monitor the fill level in a container. Radar level measurement devices (e.g., those operating on the time-of-flight principle) emit electromagnetic radiation pulses of a specific wavelength and then detect the time-varying curve of the reflected electromagnetic radiation as an echo curve. Here, the reflection from the surface of the liquid being measured or the surface of the fill material in the container is primarily detected. These reflections are superimposed to form a time-varying measured signal, which is detected and displayed as an echo curve, typically with multiple peaks. The fill height of the fill material in the container is then determined based on the changes in this echo curve.

[0005] Another known example of field equipment is the vibration limit level sensor (also known as a vibration-type limit level sensor). A vibration limit level sensor typically includes a diaphragm that can be excited to vibrate by a driver. This diaphragm can then be used to excite one or more mechanical oscillators arranged on it to vibrate. Depending on the degree to which at least one mechanical oscillator is covered by a filler material and the viscosity of that filler material, at least one mechanical oscillator vibrates at a characteristic frequency and amplitude that can be detected by the vibration limit level sensor and converted into a measurement signal. Summary of the Invention

[0006] The basic objective of this invention is to provide a field device that requires minimal installation work, occupies little installation space, and provides highly reliable measurements. Furthermore, a method for operating the field device should also be provided, which enables the measurement of fill level and limit level as simply as possible.

[0007] According to the present invention, this objective is achieved by the features described in the independent claim. Further specific embodiments and advantages will be described in conjunction with the dependent claims.

[0008] The field device according to the invention includes a radar sensor for measuring the fill level and a vibration limit level sensor for determining the limit level. Here, the radar sensor should be able to continuously determine (e.g., in a container) changes in the fill level, while the vibration limit level sensor should be able to detect whether the maximum limit level has been reached. This field device is a modular field device, wherein the two different types of sensors are arranged within or on a housing. The radar sensor and the vibration limit level sensor are integrated into this field device. Specifically, this field device has only one housing and a common set of sensor electronics.

[0009] The radar sensor has transmitting and receiving units as well as an antenna. Specifically, the antenna is a horn antenna with a tapered design. Specifically, a radar chip is used as both the transmitting and receiving unit. Specifically, electromagnetic waves generated at the transmitting unit are guided to the antenna via a waveguide and coupled into the antenna. The antenna is used to focus the emitted radiation onto the medium under test and to converge the radiation reflected by the medium.

[0010] The vibration limit level sensor includes a drive unit and at least one mechanical oscillator connected thereto. Specifically, the at least one mechanical oscillator is excited to vibrate via a diaphragm by a piezoelectric actuator or an inductive actuator. The mechanical oscillator can be a single-bar oscillator (Einstabschwinger) or a vibrating fork, which will be described in detail below.

[0011] According to the present invention, the antenna also functions as a mechanical oscillator. That is, radar radiation is coupled into and focused by the antenna, while the antenna is also excited by the drive unit to vibrate in its function as a mechanical oscillator.

[0012] By integrating the antenna and mechanical oscillator into a single component, both sensors (limit level sensor and fill level sensor) are integrated into a single field device, and more specifically, into a single mechanical structure. This eliminates the need for additional mechanical structures. Furthermore, integration into a single field device and mechanical structure saves installation space, as only one through-hole is needed on the container for inserting the field device, whereas typically each field device requires two separate holes.

[0013] Furthermore, the safety of field equipment is improved because the limiting level (i.e., the maximum or minimum allowable fill level) can be identified using two principles. Particularly in the vicinity of radar sensors, where fill level measurement accuracy is low, vibration limiting level sensors can be used as a secondary measurement method.

[0014] In one specific embodiment, the antenna is designed as at least two parts, including a first antenna section and a second antenna section. Here, the first antenna section constitutes a first mechanical oscillator, and the second antenna section constitutes a second mechanical oscillator. Therefore, this two-part horn antenna is used both for radar beamforming and focusing, and also as a vibrating fork for detecting limiting levels. The two-part design facilitates vibration excitation, and furthermore, the two counter-vibrating mechanical oscillators can better compensate for any potential imbalances. When the antenna is designed as at least two parts, gaps or slots are specifically designed between the antenna sections. This design is advantageous because air can escape from the antenna region when the medium being measured reaches the antenna.

[0015] In another specific embodiment, the first antenna portion and the second antenna portion extend along the arcuate section of the imaginary cone or imaginary conical antenna. That is, the first antenna portion and the second antenna portion constitute part of the imaginary conical horn antenna. Specifically, the first antenna portion and the second antenna portion extend to an angular range of 20° to 180°, preferably to an angular range greater than 40° and less than 180°. Here, both the focusing of the transmitted radar radiation and the collection of the reflected radar radiation can maintain high quality.

[0016] Specifically, the first and second antenna sections are designed as conical half-shells, with a gap forming between the two half-shells. Specifically, the gap width remains constant along its length. However, the gap can also have a varying width, for example, it can be designed to gradually narrow in one direction.

[0017] Apart from the slot, the two half-shells constitute a conical horn antenna. The slot decouples the first and second antenna sections (or the first and second mechanical oscillators) so that they can vibrate at a sufficient frequency and amplitude. The two half-shells approximately constitute a closed antenna, thus enabling particularly good focusing of radar radiation.

[0018] In another specific embodiment, the first and second antenna sections are designed as flat plates. These plates particularly have a trapezoidal base, wherein the width of the base increases along the process direction. In this embodiment, the mechanical oscillator has a particularly large base to allow for contact with as much of the medium as possible. This embodiment is particularly suitable for viscous media or for measuring the limiting level of loose materials.

[0019] Specifically, the distance between the first and second antenna sections gradually increases from the housing towards the process end. This separation of the antenna sections ensures good focusing of the radar radiation.

[0020] In particular, the first and second antenna sections are mirror-symmetrical about their axial extension. This effectively avoids imbalance between the two mechanical oscillators and ensures good centering of the radar radiation.

[0021] In another specific embodiment, the drive unit for vibrating the antenna or mechanical oscillator is arranged off-center from the central axis of the field device. Specifically, the field device has a rotationally symmetrical structure, and the central axis extends through the center of the field device. As described below, a waveguide is arranged at the center of the field device to centrally couple the radar radiation into the antenna.

[0022] Specifically, the drive unit is designed to be annular. In this context, "annular" means that the drive unit is arranged around an internal region. The drive unit can have a polygonal or toroidal geometry. The drive unit can have a closed or open geometry and can partially or completely surround the internal region. Specifically, the drive unit is designed to be circular and extends to cover the roots (Ansatz) of the first and second mechanical oscillators. Specifically, the drive unit includes a piezoelectric element that expands and contracts radially or axially upon application of a voltage, thereby causing the diaphragm and thus at least one mechanical oscillator to vibrate.

[0023] The drive unit can also be configured such that it extends only to and covers a portion of the mechanical oscillator, particularly positioned only at the root of the oscillator. For example, piezoelectric elements, electromagnets, or other oscillating drive elements can drive the mechanical oscillator. The motion of the piezoelectric element, electromagnet, or other oscillating drive element can then be indirectly transmitted to another mechanical oscillator. For this purpose, suitable transmission mechanisms, such as rotatably supported levers, can be provided.

[0024] As described above, the waveguide that transmits radar radiation from the transmitting and receiving units to the antenna extends specifically along the central axis. The waveguide is arranged such that it is coaxial with the antenna. In particular, the waveguide may also be arranged within a ring-shaped drive unit. Specifically, the waveguide is centrally arranged relative to the first and second antenna sections, such that radar radiation can be centrally coupled between the two antenna sections.

[0025] The present invention also relates to a method for operating field equipment, particularly a method for operating field equipment as described above, wherein the field equipment is mounted on a container, wherein the filling level in the container is continuously detected by means of a radar sensor, and wherein a vibration limit level sensor is used to detect a limit level when a minimum or maximum filling level is reached. Here, the antenna is capable of vibration and simultaneously functions as a mechanical oscillator.

[0026] Specifically, the first antenna section and the second antenna section are capable of vibration and simultaneously transmit radar radiation through the antenna or the first antenna section and the second antenna section. Attached Figure Description

[0027] Other specific embodiments and their advantages will be described below with reference to the accompanying drawings.

[0028] Figure 1 The field device according to the first embodiment is shown in a perspective view from an obliquely upward angle.

[0029] Figure 2 The field equipment according to the second embodiment is shown in a perspective view from an obliquely upward angle.

[0030] Figure 3 The field device according to the third embodiment is shown in a perspective view from an obliquely upward angle.

[0031] Figure 4 A schematic cross-sectional view shows a field device with a driver according to a fourth embodiment.

[0032] Figure 5 A schematic cross-sectional view shows a field device with a driver according to a fifth embodiment. Detailed Implementation

[0033] Figure 1 A field device 10 according to a first embodiment is shown. The field device 10 includes a housing 12 in which sensor electronics (not shown) are arranged. The field device 10 has a conical antenna 14 (horn antenna) at its oriented end, which has a first antenna portion 16 and a second antenna portion 18. The first antenna portion 16 is also a first mechanical oscillator 20, and the second antenna portion 18 is also a second mechanical oscillator 22.

[0034] In this regard, the field device 10 includes both a radar sensor for measuring the fill level, wherein the first antenna portion 16 and the second antenna portion 18 serve as part of the horn antenna 14. The field device 10 also includes a vibration limit level sensor, wherein the first mechanical oscillator 20 and the second mechanical oscillator 22 serve as two parts of a mechanical oscillator (vibration fork) 24 to detect the limit level.

[0035] Therefore, two measurement principles 14 and 24 can be realized through the common mechanical structures 14 and 24.

[0036] According to a first embodiment of the field device 10, the first antenna portion 16 and the second antenna portion 18 are designed as half-shells, separated from each other by a slot 26. These two half-shells 16 and 18 are each formed as part of a cone. The slot 26 has a constant slot width w along its length.

[0037] from Figure 1 It can also be seen that, in the section adjacent to the housing, a matching cone 28 is arranged between the first antenna portion 16 and the second antenna portion 18.

[0038] Combination Figures 2 to 5 Other embodiments are shown below, wherein the same reference numerals as those used in the description of the first embodiment will be used for the same or at least functionally equivalent elements.

[0039] Figure 2 A field device 10 according to a second embodiment is shown. The main difference between the field device 10 and the first embodiment lies in the design of the first antenna portion 16 and the second antenna portion 18. Here, the first antenna portion 16 and the second antenna portion 18 extend along arcuate sections on an imaginary cone. The mechanical oscillators 20 and 22 are curved. The angle range of each arcuate section is approximately 60°. The distance between the first antenna portion 16 and the second antenna portion 18 gradually increases from the housing 12, causing the mechanical oscillators 20 and 22 to be outwardly flared from each other.

[0040] Figure 3 The field device 10 in the third embodiment is shown. The field device 10 differs from the first and second embodiments in the design of the antenna components 16, 18 (or mechanical oscillators 20, 22) and the housing 12.

[0041] Here, housing 12 has a rectangular cross-section. However, it is also conceivable to construct housing 12, which has the antenna portions 16, 18 shown, as circular.

[0042] Here, the first antenna portion 16 (or the first mechanical oscillator 20) and the second antenna portion 18 (or the second mechanical oscillator 22) are constructed as flat plates with trapezoidal bottom surfaces. The widths of the first antenna portion 16 and the second antenna portion 18 gradually increase from the housing 12 towards the process direction. Therefore, the mechanical oscillators 20 and 22 are flat and not curved. The distance between the first antenna portion 16 and the second antenna portion 18 also gradually increases from the housing 12.

[0043] Figure 4 and Figure 5Two other embodiments are described, which differ in the type of driver for the mechanical oscillator 24.

[0044] Figure 4 A fourth embodiment of the field device 10 is shown. The field device 10 includes a housing 12 and a first antenna portion 14 and a second antenna portion 16 disposed thereon. Sensor electronics 30, which also includes transmitting and receiving elements (not explicitly shown) of a radar sensor, are disposed within the housing 12. A waveguide 32 extends from the sensor electronics 30 along the central axis M of the field device 10. The waveguide 32 extends coaxially with the antenna 14, which includes the first antenna portion 16 and the second antenna portion 18. Matching cones 28 are disposed at the ends of the housing 12 along the orientation path to couple radar radiation into the antenna 14.

[0045] As the driving unit 34 for the first mechanical oscillator 20 and the second mechanical oscillator 22, an annular piezoelectric element 36 is arranged in the housing 12. The piezoelectric element 36 is connected to the sensor electronics 30 via an electrical connector 40.

[0046] In principle, two different variations of the piezoelectric element 36 can be conceived, which can vibrate axially as indicated by arrow 38, or radially as indicated by arrow 40. The piezoelectric element 36 extends in a ring around the central axis M and the waveguide 32. The drive unit 34 causes the mechanical oscillators 20 and 22 to vibrate via the diaphragm 42.

[0047] Figure 5 A fifth embodiment of the field device 10 is shown, wherein the drive unit 34 shown in this embodiment is... Figure 4 There are some changes compared to the previous version. Here, the drive unit 34 is constructed asymmetrically, and only for the mechanical oscillator 20 is there a drive element in the form of a piezoelectric element 36, which can expand axially or radially (see arrow 38 or arrow 40). The movement of the piezoelectric element 36 is indirectly transmitted to the second mechanical oscillator 22 through a curved beam 44 with a rotary bearing 46.

[0048] List of reference numerals 10: Field Equipment 12: Shell 14: Antenna 16: First antenna section 18: Second Line Section 20: First mechanical oscillator 22: Second mechanical oscillator 24: Mechanical oscillator (vibration fork) 26: Gap 28: Matching vertebral bodies 30: Sensor Electronics 32: Waveguide 34: Drive Unit 36: Piezoelectric element 38: Arrow (Axial direction) 40: Arrow (radial) 42: Membrane 44: Bending Beam 46: Rotary bearing.

Claims

1. A field device comprising a radar sensor for measuring the level of filling material and a vibration limiting level sensor, wherein, The radar sensor has a transmitting and receiving unit and an antenna (14), wherein the vibration limit switch has a driving unit (34) and a mechanical oscillator (24) connected to the driving unit, wherein the antenna (14) also serves as the mechanical oscillator (24).

2. The field equipment according to claim 1, Its features are, The antenna (14) is designed as at least two parts, having a first antenna part (16) and a second antenna part (18), wherein the first antenna part (16) is a first mechanical oscillator (20) and the second antenna part (18) is a second mechanical oscillator (22).

3. The field equipment according to claim 2, Its features are, The first antenna portion (16) and the second antenna portion (18) extend along the arc-shaped section of the imaginary conical antenna, respectively.

4. The field equipment according to claim 2 or 3, Its features are, The first antenna portion (16) and the second antenna portion (18) are designed as conical half-shells, and a gap (26) is formed between the half-shells.

5. The field equipment according to any one of claims 2 to 4, Its features are, The first antenna portion (16) and the second antenna portion (18) are designed to be flat.

6. The field equipment according to any one of claims 2 to 5, Its features are, The first antenna portion (16) and the second antenna portion (18) gradually increase the distance between each other from the housing (20) toward the process end.

7. The field device according to any one of the preceding claims, Its features are, The drive unit (34) for driving at least one of the mechanical oscillators (24, 20, 22) is arranged off-center from the central axis (M) of the field device (10).

8. The field device according to any one of the preceding claims, Its features are, The drive unit (43) is designed to be ring-shaped.

9. The field device according to any one of the preceding claims, Its features are, The waveguide (32) extends along the central axis (M) to transmit radar radiation.

10. A method for operating field equipment (10), wherein, The field device (10) includes a radar sensor and a filling level sensor, wherein the filling level is continuously detected by the radar sensor and the limit level is detected by the vibration limit level sensor, wherein the antenna (14) is capable of vibration and is also used as a mechanical oscillator (24).

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