SENSOR DEVICE AND METHOD FOR DETERMINING AND/OR MONITORING A PROCESS VARIABLE OF A MEDIUM IN A CONTAINER

Abstract

A sensor device for determining and/or monitoring a process variable of a medium in a container includes: a crystal body having at least one defect; and a magnetic field device for generating a magnetic field, the magnetic field device arranged such that a magnetic field can be generated in the region of the crystal body and in the region of the medium located within the container, so that a change of the magnetic field in the region of the crystal body is amplified, wherein the crystal body and the magnetic field device are arranged from the outside on a wall of the container. A method for determining and/or monitoring a process variable of a medium in a container using the sensor device is also disclosed.

Claims

1-9. (canceled)

10. A sensor device for determining and/or monitoring a process variable of a medium in a container, the sensor device comprising: a crystal body that includes at least one defect; a magnetic field device configured to generate a magnetic field, wherein the magnetic field device is arranged to generate the magnetic field in a region of the crystal body and in a region of the medium within the container such that a change in the magnetic field in the region of the crystal body is amplified, wherein the crystal body and the magnetic field device are configured to be arranged on a wall of the container; an excitation unit configured to generate an excitation signal to optically excite the at least one defect of the crystal body; a detection unit configured to detect a magnetic field-dependent fluorescence signal of the crystal body; and an evaluation unit configured to determine at least one statement about the process variable based on the fluorescence signal.

11. The sensor device according to claim 10, wherein the crystal body is: diamond and the at least one defect is a nitrogen defect; silicon carbide and the at least one defect is a silicon defect; or hexagonal boron nitride and the at least one defect is a defect color center.

12. The sensor device according to claim 10, wherein the magnetic field device includes a permanent magnet or a coil.

13. The sensor device according to claim 10, wherein the at least one defect includes at least two defects and/or the sensor devices comprises at least two crystal bodies, each including the at least one defect, and wherein the at least two defects and/or the at least two crystal bodies are configured to be arranged linearly and perpendicularly to ground on the wall of the container.

14. The sensor device according to claim 10, further comprising at least one optical fiber configured to conduct the excitation signal from the excitation unit to the crystal body and/or to conduct the fluorescence signal of the crystal body to the detection unit.

15. The sensor device according to claim 10, wherein the sensor device is configured to be arranged outside the container.

16. The sensor device according to claim 10, wherein the process variable the sensor device is configured to determine and/or monitor is a fill level and/or a limit level of the medium in the container.

17. The sensor device according to claim 10, wherein the sensor device is configured to be mounted flush with the wall of the container such that at least a portion of the sensor device is disposed in the wall.

18. A method for determining and/or monitoring a process variable of a medium in a container using a sensor device, wherein the sensor device comprises: a crystal body that includes at least one defect; a magnetic field device configured to generate a magnetic field, wherein the magnetic field device is arranged to generate the magnetic field in a region of the crystal body and in a region of the medium within the container such that a change in the magnetic field in the region of the crystal body is amplified, wherein the crystal body and the magnetic field device are adapted to be disposed on a wall of the container; an excitation unit configured to generate an excitation signal to optically excite the at least one defect of the crystal body; a detection unit configured to detect a magnetic field-dependent fluorescence signal of the crystal body; and an evaluation unit configured to determine at least one statement about the process variable based on the fluorescence signal, wherein the method comprises: generating the magnetic field in the area of the crystal body and in the area of the medium inside the container; stimulating the at least one defect; detecting the fluorescence signal of the crystal body; determining a gradient of the magnetic field from the fluorescence signal; and determining the at least one statement about the process variable based on the gradient of the magnetic field.

19. The method according to claim 18, wherein the at least one defect includes at least two defects and/or the sensor devices comprises at least two crystal bodies, each including the at least one defect, wherein the at least two defects and/or the at least two crystal bodies are configured to be arranged linearly and perpendicularly to ground disposed on the wall of the container, and wherein the gradient of the magnetic field is determined based on the at least two defects and/or the at least two crystal bodies with at least one defect each, which are arranged linearly and perpendicularly to ground.

Description

[0036] The invention is explained in greater detail with reference to the following drawings, FIG. 1-6. The following are shown:

[0037] FIG. 1: a simplified energy diagram for a negatively charged NV center in the diamond.

[0038] FIG. 2: a first embodiment of the sensor device according to the invention.

[0039] FIG. 3: a second embodiment of the sensor device according to the invention.

[0040] FIG. 4: a third embodiment of the sensor device according to the invention.

[0041] FIG. 5: a schematic representation of the change in the magnetic field at an interface between the medium and air.

[0042] FIG. 6: a schematic diagram of the method according to the invention.

[0043] FIG. 1 shows a simplified energy diagram for a negatively charged NV center in a diamond to exemplify the excitation and fluorescence of a defect in a crystal body. The following considerations can be transferred to other crystal bodies having corresponding vacancies.

[0044] In the diamond, each carbon atom is typically covalently bonded to four further carbon atoms. A nitrogen vacancy center (NV center) consists of a vacancy in the diamond lattice, i.e., an unoccupied lattice site, and a nitrogen atom as one of the four neighboring atoms. In particular, the negatively charged NV.sup. centers are important for the excitation and evaluation of fluorescence signals. In the energy diagram of a negatively charged NV center, there is a triplet ground state .sup.3A and an excited triplet state .sup.3E, each of which has three magnetic substates ms=01. Furthermore, there are two metastable singlet states .sup.1A and .sup.1E between the ground state .sup.3A and the excited state .sup.3E.

[0045] Excitation light 1 from the green range of the visible spectrum, e.g., an excitation light 1 with a wavelength of 532 nm, excites an electron from the ground state .sup.3A into a vibrational state of the excited state .sup.3E, which returns to the ground state .sup.3A by emitting a fluorescence photon 2 with a wavelength of 630 nm. An applied magnetic field with a magnetic field strength B leads to a splitting (Zeeman splitting) of the magnetic sub-states, so that the ground state consists of three energetically separated sub-states, each of which can be excited. However, the intensity of the fluorescence signal is dependent on the respective magnetic substrate from which it was excited, so that the magnetic field strength B, for example, can be calculated using the Zeeman formula on the basis of the distance between the fluorescence minima. In the context of the present invention, further possibilities for evaluating the fluorescence signal are provided, such as the evaluation of the intensity of the fluorescent light, which is likewise proportional to the applied magnetic field. An electrical evaluation can in turn be done, for example, via a Photocurrent Detection of Magnetic Resonance (PDMR). In addition to these examples for evaluating the fluorescence signal, there are other possibilities which also fall within the scope of the present invention.

[0046] FIG. 2 shows a first exemplary embodiment of the sensor device 3 according to the invention for determining and/or monitoring a process variable, for example a filling level or a limit level, of a medium in a container. The sensor device 3 is arranged from the outside on a wall 13 of the container 5, which is partially filled with a medium 4 to which a relative magnetic permeability .sub.r,2 is assigned. Above the medium there is usually air or a gas with the relative magnetic permeability .sub.r,1. The sensor device 3 comprises a crystal body 6 with a defect 7, an excitation unit 9 for exciting the defect 7, a detection unit 10 for detecting the fluorescence signal of the crystal body 6 and an evaluation unit 11 for determining at least one statement about the process variable on the basis of the fluorescence signal. The crystal body 6 can be, for example, a diamond with at least one nitrogen defect, silicon carbide with at least one silicon defect or hexagonal boron nitride with at least one defect color center.

[0047] Furthermore, a magnetic field device 8 is provided which generates a magnetic field in the area of the crystal body 6 and in the area of the medium 4 located inside the container 5, so that a change of the magnetic field in the area of the crystal body 6 is amplified. The magnetic field device 8 is, for example, a permanent magnet or a coil and may be arranged at least partially within the coil or between two end regions of the permanent magnet.

[0048] FIG. 2 shows a sensor device 3 which is arranged outside the container, i.e., non-invasively. As an alternative, FIG. 3 shows an invasive sensor device 3 which is flush with the wall 13 of the container 5. For example, the sensor device 3 is inserted into the wall 13 of the container by means of an adapter or a socket (not shown). The crystal body of FIG. 3 has, by way of example, two defects 7 which are arranged linearly and perpendicularly to the base on the wall 13 of the container 5. In this way, a direction of the change in the gradient of the magnetic field can be determined.

[0049] FIG. 4 shows a third exemplary embodiment of the sensor device 3, in which an optical fiber 12 is used to transmit the excitation signal from the excitation unit 9 to the crystal body 6 and to transmit the fluorescence signal of the crystal body 6 to the detection unit 10. In this example, the excitation unit 9, the detection unit 10 and the evaluation unit 11 are spatially separated from the crystal body 6.

[0050] In FIG. 5, the change of the magnetic field between the medium 4 with the relative magnetic permeability .sub.r,2 and the air with the relative magnetic permeability .sub.r,1 is shown schematically by means of the magnetic field lines which are drawn dashed. The sensor device 3 is attached to the wall 13 of the container 5. For simplicity, only the crystal body 6 and the magnetic field device 8 of the sensor device 3 are shown. Due to the difference in the magnetic permeability of the medium and the air, the otherwise parallel magnetic field lines are distorted in the area of the interface between the medium and the air. The magnetic field device 8 amplifies this distortion of the magnetic field lines in order to be able to read them subsequently by means of the fluorescence signal of the crystal body 6.

[0051] The method according to the invention is schematically depicted as a flow diagram in FIG. 6. In a first step 101, a magnetic field is generated in the area of the crystal body 6 and in the area of the medium 4. Subsequently, in a second step 102, the excitation of the at least one defect 7 takes place by means of the excitation unit 9, whereupon the crystal body 6 emits a fluorescence signal which is detected in the third step 103. On the basis of the detected fluorescence signal, the gradient of the magnetic field is determined in the fourth step 104 and finally, in the fifth step 105, a statement about the process variable is determined on the basis of the gradient of the magnetic field. The gradient of the magnetic field can be determined, for example, by means of at least two defects and/or at least two crystal bodies with at least one defect each, which are arranged linearly and perpendicular to the ground.

LIST OF REFERENCE SIGNS

[0052] 1 Excitation light [0053] 2 Fluorescent light [0054] 3 Sensor device [0055] 4 Medium [0056] 5 Container [0057] 6 Crystal body [0058] 7 Defect [0059] 8 Magnetic field device [0060] 9 Excitation unit [0061] 10 Detection unit [0062] 11 Evaluation unit [0063] 12 Optical fiber [0064] 13 Wall