Quantum sensor

Abstract

The invention relates to a sensor device (3) for determining and / or monitoring a process variable of a medium (5) in a container (4), comprising - a crystal (6) having at least one defect (7), - a magnetic field system (8) for generating a magnetic field, wherein the magnetic field system (8) is arranged such that a magnetic field (B) can be generated in the region of the crystal (6) and in the region of the medium (5) located within the container (4) by means of the magnetic field system (8), and wherein the crystal (6) and the magnetic field system (8) can be arranged externally on a wall of the container (4), - a detection unit (9) for detecting a magnetic-field-dependent fluorescence signal (2) from the crystal (6), wherein the detection unit (9) has an excitation unit (10) for optically exciting the defect (7) and a detector (11) for detecting the fluorescence signal (2), and - an evaluation unit (12) for determining at least one piece of information about the process variable on the basis of the fluorescence signal (2). Furthermore, the invention relates to a method for operating the sensor device (3) of the invention.

Description

TECHNICAL FIELD

[0001] The present invention relates to a sensor device for determining and / or monitoring a process variable of a medium in a container and a method for determining and / or monitoring a process variable by means of the sensor device of the present invention. BACKGROUND

[0002] Field devices for monitoring and / or determining at least one chemical or physical process variable of a medium are known in various embodiments in the art. In the context of the present invention, in principle, all measuring devices are referred to as field devices, which are applied in the vicinity of a process and which deliver or process process-related information, thus, all measuring devices are also referred to as remote I / O, radio adapters and are generally referred to as electronic components, which are arranged at the field level. The Endress+Hauser Group produces and sells a large number of such field devices.

[0003] Recent developments in the field of sensors relate to so-called quantum sensors, in which case the most diverse quantum effects are used for determining various physical and / or chemical measurement variables. Such methods are of great interest in the field of industrial process automation, in particular in the ongoing efforts to achieve miniaturization and to improve sensor performance.

[0004] DE 3742878 A1, for example, describes an opto-magnetic field sensor, in which a crystal is used as a magnetically sensitive optical element.

[0005] From DE 102017205099 A1 a sensor device is known, which has a crystal containing at least one defect, a light source, a high-frequency system for impinging the crystal with a high-frequency signal and a detection unit for detecting a magnetic field-dependent fluorescence signal. The light source is arranged on a first substrate and the detection system is arranged on a second substrate, while the high-frequency system and the crystal can be arranged on the two substrally connected to each other. The measured variable can be an external magnetic field, an electric current, a temperature, a mechanical stress or a pressure. A similar device is known from DE 102017205265 A1.

[0006] DE 102014219550 A1 describes a combined sensor for recording pressure, temperature and / or magnetic fields, in which the sensor element has a diamond structure with at least one nitrogen-vacancy center.

[0007] DE 102018214617 A1 discloses a sensor system, which likewise has a crystal with a plurality of color centers or F centers, in which case different filter elements are used for increasing the efficiency and for miniaturization.

[0008] DE 10 2016 210 259 A1 discloses another form of a sensor device and a calibration and evaluation method based on defects in a crystal. The sensor device comprises a crystal having at least one defect, a light source, a microwave antenna for providing microwaves to the crystal, a detection system for recording a fluorescence from the crystal, and an application system by means of which an induction current can be applied to the microwave antenna. The microwave antenna is thus used to generate microwaves and to generate an internal magnetic field. The internal magnetic field enables calibration during continuous operation. SUMMARY

[0009] Starting from the prior art, it was an object of the present application to extend the field of application of such a technology.

[0010] This object is achieved by a sensor device and a method as defined by the present application.

[0011] With regard to the sensor device, the object of the present application is achieved by a sensor device for determining and / or monitoring a process variable of a medium in a container, comprising

[0012] a crystal having at least one defect,

[0013] a magnetic field system for generating a magnetic field,

[0014] wherein the magnetic field system is arranged in such a way that by means of the magnetic field system a magnetic field can be generated in a region of the crystal and in a region of the medium located within the container, and

[0015] wherein the crystal and the magnetic field system are externally arrangeable on a wall of the container,

[0016] a detection unit for detecting a magnetic-field-dependent fluorescence signal from the crystal,

[0017] wherein the detection unit has an excitation unit for optically exciting the defect and a detector for detecting the fluorescence signal, and

[0018] an evaluation unit for determining at least one piece of information about the process variable on the basis of the fluorescence signal.

[0019] Defects in the crystal are optically excited, and their fluorescence is detected and evaluated. Furthermore, a magnetic field is generated in both the crystal and container regions using a magnetic field system. This magnetic field is then affected by the medium present in the container, for example, due to the presence or absence of the medium, changes in the fill level, or changes in at least one property of the medium, particularly physical or chemical properties. Changes in the magnetic field subsequently affect the fluorescence signal of the defects, making process monitoring possible or process variables determinable based on the magnetic field-related fluorescence signal. Advantageously, very high measurement resolution is achieved for recording medium-related magnetic field changes based on defects in the crystal. This results in very high measurement accuracy.

[0020] Furthermore, the sensor device of the present invention provides a means for external fastening at the container. It terminates flush with the container wall and is therefore non-invasive. For various reasons, determining one or more process variables by means of flush-mounted or non-invasive measuring devices is highly advantageous in the field of process automation, and there is a general effort to implement such solutions for the most diverse applications. However, this can be difficult in individual cases. Therefore, such devices can only be used in isolation, and when available, their application scope is limited. The present invention provides a flush-mounted or non-invasive sensor that enables a variety of applications and allows for comprehensive process analysis.

[0021] Containers, especially container units or pipes.

[0022] The detection unit includes an excitation unit for optically exciting defects. The excitation unit can be, for example, a laser or a light-emitting diode (LED). The detector of the detection unit can then be, for example, a photodetector or a CMOS sensor. Additionally, the detection unit can include other optical elements, such as various filters, lenses, or mirrors.

[0023] In one embodiment, the crystal is diamond with at least one nitrogen defect, silicon carbide with at least one silicon defect, or hexagonal boron nitride with at least one color center defect.

[0024] The crystal according to the invention comprises at least one defect. However, multiple defects can also be used. In this case, a linear arrangement of defects is particularly preferred. Multiple defects lead to an increase in intensity, thereby improving measurement resolution, and making intensity changes detectable even in relatively weak magnetic fields.

[0025] In an additional embodiment, the magnetic field system includes at least one coil. Advantageously, when the crystal and the magnetic field system are arranged against the wall of the container, the coil at least partially surrounds the crystal. Preferably, the crystal is at least partially arranged within the coil.

[0026] In one aspect, a compact construction of the sensor device can be chosen. In this case, the detection unit is arranged directly in the vicinity of the magnetic field system and the crystal. In another embodiment, however, the sensor device additionally comprises an optical fiber for guiding the fluorescent signal from the crystal to the detection unit. In the latter case, the detection unit is arranged spatially separate from the other components of the sensor device. Which variant is preferred depends on the particular application of the sensor device. In this case, the measurement accuracy is particularly explicitly dependent on the components of the detection unit, such as the excitation unit, the optical components, etc. The detection unit and its arrangement relative to the remaining components of the sensor device are chosen in accordance with the intended application.

[0027] Furthermore, in one aspect, it can be chosen to fasten the sensor device from the outside on the wall of the container. In this case, a non-invasive determination of at least one process variable can take place. However, an alternative embodiment provides that the sensor device is embodied such that it is flush applied in the wall of the container. Thus, the sensor device comprises a frame for introducing at least one component of the sensor device into the wall of the container in one embodiment. The frame can be arranged in a correspondingly embodied opening in the wall of the container. The frame is made of a predetermined material, such as stainless steel. One advantage in this regard is that, by means of the frame, the influence of the wall of the container on the determination of the process variable can be minimized or eliminated.

[0028] In an additional embodiment of the sensor device of the present invention, there can be a unit for exciting high-frequency or microwave radiation. This enables the electrons to be excited to higher energy levels.

[0029] Furthermore, the object of the present invention is achieved by a method for determining and / or monitoring a process variable of a medium in a container by means of the sensor device of the present invention, comprising the following method steps:

[0030] - generating a magnetic field in the region of the crystal and in the region of the medium located within the container,

[0031] - exciting defects in the crystal to emit fluorescence,

[0032] - detecting a magnetic-field-dependent fluorescent signal from the crystal, and

[0033] - determining at least one piece of information about the process variable on the basis of the fluorescent signal.

[0034] Advantageously, the method of the present invention and the sensor device of the present invention are characterized by a very high measurement accuracy, both with regard to absolute information about the medium and with regard to relative information about the medium. Even very small magnetic field changes caused by the medium or changes in the region of the medium can be detected with high accuracy, which is not possible with conventional measuring devices of the prior art.

[0035] One embodiment of the method comprises determining at least one variable characteristic of the magnetic field, in particular the magnetic susceptibility or the magnetic permeability, on the basis of the fluorescence signal. This variable characteristic of the magnetic field can then be taken into account for determining information about the process variable.

[0036] In this connection, it is, for example, advantageous to determine at least one physical and / or chemical variable characteristic of the medium on the basis of the variable characteristic of the magnetic field. In this case, the variable characteristic of the magnetic field can be, for example, the magnetic permeability of the medium, in particular in the case of a non-conducting medium. However, in the case of a conducting medium, for example, the electrical conductivity can also be determined, for example, on the basis of the eddy currents. However, other quality parameters of the medium can also be determined.

[0037] It is likewise advantageous to carry out a state monitoring of a process running in the container on the basis of the variable characteristic of the magnetic field. In particular, the variable characteristic of the magnetic field or a variable derived therefrom can be considered as a function of time. Examples of state monitoring include, for example, monitoring of a mixing of at least two media or monitoring of a chemical reaction taking place in the container.

[0038] The sensor device of the application and the method of the application can thus carry out comprehensive process monitoring.

[0039] A further embodiment of the method of the application comprises monitoring a predefinable limit level of the medium in the container. The sensor of the system of the application can thus also be used as a limit level switch for monitoring a predefinable filling level of the medium in the container.

[0040] Advantageously, in this connection, a limit value of the variable characteristic of the magnetic field is predefined, and wherein, upon exceeding or falling below the limit value, the reaching of the predefinable limit level is signaled.

[0041] Alternating fields or direct current fields can be used in connection with the method of the application. While alternating fields are advantageous, in particular for the evaluation of the measurement signal, the influence of the eddy currents formed in the case of a conducting container has to be taken into account. In this connection, a flush embodiment of the sensor device using a suitable frame of a known material can be advantageous, since in this way the influence of the eddy currents generated is known and can be minimized or eliminated.

[0042] Finally, it is provided in one embodiment of the method of the application that the magnetic field generated in the region of the crystal and in the region of the medium located in the container is generated as an alternating field, and that the frequency of this alternating field is varied. The penetration depth of the magnetic field through the wall of the container, in particular in the case of a conducting container, and into the medium depends on the frequency of the magnetic field. The penetration depth increases with decreasing frequency. By varying the frequency of the alternating field, a multidimensional analysis of the medium in the container is possible. In this way, for example, deposits, gradients of the medium composition depending on the position in the container and sediments can be detected.

[0043] It is noted here that the embodiments described in connection with the sensor device of the application can be applied in the method of the application mutatis mutandis and vice versa. BRIEF DESCRIPTION OF DRAWINGS

[0044] The application will now be explained in more detail on the basis of the drawings, which show the following:

[0045] Figure 1 is a simplified energy level diagram of a negative NV center in diamond,

[0046] Figure 2 is a first embodiment of the sensor device of the application, and

[0047] Figure 3 is a second embodiment of the sensor device of the application.

[0048] In the figures, identical elements are provided with the same reference signs. DETAILED DESCRIPTION

[0049] REFERENCE Figure 1 With reference to Fig. 1, first, the excitation of the fluorescence of a defect of a crystal will be explained, exemplarily in the case of an NV center in diamond. These considerations can be applied to other crystals with corresponding defects.

[0050] Diamond, which is one of the basic forms of carbon, has a cubic, face-centered crystal structure with two atoms per primitive cell. The so-called NV center is a vacant carbon atom (V) at a lattice position with a nitrogen atom (N) as one of the four nearest neighbor atoms. For the excitation and evaluation of the fluorescence signal, it is important, inter alia, the negative NV centers, which have an additional electron from the diamond lattice associated with them.

[0051] The diamond structure with embedded negative NV centers is assigned to the symmetry group C 3ν which determines the possible spatial eigenstates of the NV center. From Figure 1 the energy level diagram without resonant excitation and without external magnetic field it is evident that the triplet ground state 3 A2and the excited triplet 3 E, two metastable singlet states 1 Eand 1 A are located between them. The triplet ground state 3 A2has three magnetic substates m s = 0, ±1. Also in the case of the excited 3 E state, there is a splitting of the energy levels.

[0052] For example, by means of an excitation 1 with light of a wavelength λ = 532 nm, an excitation of the vibrational states of the excited 3E state takes place, followed by a Frank-Condon transition to the ground state 3A2, in this case, fluorescent photons 2 with a wavelength of λ = 630 nm are emitted. In addition, upon application of an external magnetic field, a Zeeman splitting of the energy levels occurs, and in connection therewith, two fluorescence minima are emitted, which are spaced apart, for example, in proportion to the applied magnetic field strength B.

[0053] According to the application, the evaluation of the fluorescence can be carried out in many different ways. In addition to the evaluation of the energy difference between the two energy levels mentioned above, which allows the magnetic field to be determined on the basis of the Zeeman formula, in another optical evaluation method, the intensity of the emitted light can also be taken into account, which is likewise proportional to the magnetic field. In turn, an electrical evaluation, for example via the photoelectric current detection of magnetic resonance (PDMR), is also an option. In addition to these examples of evaluation of the fluorescence signal, other options are also available, which likewise fall within the scope of the application.

[0054] Figure 2 A possible example of an embodiment of the sensor device 3 of the application is shown, which is mounted on the outer surface of a container 4 in the form of a container, which is partially filled with a medium 5. The sensor device 3 comprises a crystal 6 with at least one defect 7 and a magnetic field system 8 with at least one coil, which at least partially surrounds the crystal 6. In the case of the embodiment illustrated here, the crystal 6 is arranged within the coil 8. The magnetic field system 8 serves to generate a magnetic field B in the region of the crystal 6 and in the region of the inner volume of the container 4.

[0055] In addition, the sensor device comprises a detection unit 9 with an excitation unit 10 and a detector 11 for detecting the fluorescence signal 2, and an evaluation unit 12 for the additional evaluation of the signal 2 and for determining at least one piece of information about the process variable.

[0056] Although Figure 2 a shows a non-invasive sensor device 3, which can be fastened from the outside on the wall of a container 4, Figure 2 b shows a device 3, which is designed such that it terminates flush with the wall of a container 4. Figure 2 The device 3 of b comprises a frame 13, by means of which at least one component of the sensor device 3, here the crystal 6 and the coil, can be fastened in an opening in the wall of the container 4.

[0057] Figure 3 Another possible embodiment of a system with two devices 3 and 3' of the application is shown. In contrast to the embodiment of Figure 2 In contrast to the embodiment of Figure 3In each case, no compact construction is used, but rather the detection units 9, 9' and the evaluation units 12, 12' are arranged spatially remote from the remaining components of the sensor devices 3 and 3' and are therefore not shown. In order to be able to guide the fluorescent signal 2 to the detection units 9, 9' in each case, the two shown sensor devices 3, 3' comprise in each case an optical fiber 14, 14' for guiding the light from the crystals 6, 6' to the respective detection unit 9, 9'. It is even possible to use one detection unit 9 for both crystals 6, 6' instead of two separate detection units 9, 9'. The excitation unit 11 can be arranged in the region of the container 4 or together with the evaluation unit 12. Moreover, one shared excitation unit 11 can be used for excitation instead of two separate units.

[0058] The sensor device 3 of the application and the method of the application permit comprehensive process monitoring to expand the capabilities of the measurement methods known from the prior art for process automation. On the one hand, it is possible to monitor process variables, for example a predefinable fill level of a medium in a container. However, in addition, it is also possible to characterize the medium 5 or a process occurring within the container 4 comprehensively. In addition, the device 3 of the application is advantageously a non-invasive sensor, which therefore does not need to intrude into the ongoing process and enables miniaturization of the sensor device in a simple manner, while at the same time broadening the field of application.

[0059] Reference signs

[0060] 1 Excitation light

[0061] 2 Fluorescence

[0062] 3 Sensor device

[0063] 4 Container

[0064] 5 Medium

[0065] 6 Crystal

[0066] 7 Defect

[0067] 8 Magnetic field system

[0068] 9 Detection unit

[0069] 10 Excitation unit

[0070] 11 Detector

[0071] 12 Evaluation unit

[0072] 13 Frame

[0073] 14 Optical fiber

Claims

1. A sensor device (3) for determining and / or monitoring process variables of a medium (5) in a container (4), comprising: - A crystal (6) having at least one defect (7). - A magnetic field system for generating a magnetic field (8). in, The magnetic field system (8) is arranged such that a magnetic field (B) can be generated in the region of the crystal (6) and in the region of the medium (5) located within the container (4) by means of the magnetic field system (8). The magnetic field (B) is affected by the process variables of the medium (5), and The crystal (6) and the magnetic field system (8) can be arranged externally on the wall of the container (4). - Detection unit (9), which is used to detect the magnetic field-related fluorescence signal (2) from the crystal (6). The detection unit (9) has an excitation unit (10) for optically exciting the defect (7) and a detector (11) for detecting the fluorescence signal (2). as well as - Evaluation unit (12), the evaluation unit (12) being used to determine at least one variable feature of the magnetic field (B) based on the fluorescence signal (2) and to determine at least one piece of information about the process variable based on the variable feature of the magnetic field (B). The magnetic field system (8) includes at least one coil, and When the crystal (6) and the magnetic field system (8) are arranged on the wall of the container (4), the coil at least partially surrounds the crystal (6).

2. The sensor device (3) according to claim 1. It also includes a frame (13) for introducing at least one component of the sensor device (3) into the wall of the container (4).

3. The sensor device (3) according to claim 1 or 2. in, At least one variable characteristic of the magnetic field (B) is magnetic susceptibility or magnetic permeability.

4. The sensor device (3) according to claim 1 or 2. in, The magnetic field generated in the region of the crystal (6) and in the region of the medium (5) located within the container (4) is generated as an alternating field, wherein the frequency of the alternating field is variable.

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