Radiometric level gauge with radiation filter and system

Abstract

Radiometric level gauge (100), comprising: a scintillator (101, 104) for converting radioactive radiation (110) from a useful radiation source (107) into light; an electronics (105); a light detector (102) for detecting light from the scintillator (101, 104) and for generating a signal from the detected light, from which a fill level can be calculated; a radiation filter (103) which is arranged and configured between the scintillator (101, 104) and the light detector (102) to allow the light of the scintillator (101, 104), which is due to the radioactive radiation of the useful radiation source (107), to pass in the direction of the light detector (102) and to prevent electromagnetic radiation of a different wavelength from passing through or at least to a greatly attenuated extent; wherein the radiation filter (103) is designed to prevent or at least reduce the impact of ultraviolet light on the scintillator (101, 104) during the replacement of the electronics (105).

Description

Field of the invention

[0001] The invention relates to radioactive level measurement. In particular, the invention relates to a radiometric level measuring device and a radiometric level measuring system comprising such a level measuring device. background

[0002] Radiometric level measurement measures the intensity of radioactive radiation, typically gamma rays, which penetrates the medium on its way from the radioactive source, also referred to as the useful radiation source, to the detector, which is part of the radiometric level measuring device.

[0003] A gamma source, often a cesium or cobalt isotope, emits radiation that is attenuated when it passes through materials. The measuring effect results from the absorption of the radiation by the medium being measured (filling material). Opening the container or installing any internal components is not required. The measurement is performed non-contact from the outside and is therefore suitable for extreme applications, such as highly corrosive, aggressive, and abrasive media.

[0004] DE 10 2016 122 049 A1 describes a detector unit for a radiometric density or level meter with a housing that can be opened to replace the photomultiplier unit.

[0005] US 2014 / 0131564 A1 describes a radiometric detector device comprising a scintillator, a photosensor and a control module.

[0006] DE 102015 101 705 A1 describes a measuring system for radiometric density or level measurement of a medium in a potentially explosive atmosphere. The photosensitive unit of the detector is designed in such a way that it is enclosed in an encapsulation that serves as explosion protection and consists of scintillating material, at least in part. Summary of the invention

[0007] It is an object of the invention to provide an improved radiometric measuring device for level measurement, density measurement, point level measurement or flow measurement.

[0008] This object is achieved by the features of the independent patent claims. Further developments of the invention emerge from the subclaims, the following description, and the figures.

[0009] A first aspect of the invention relates to a radiometric level measuring device comprising a scintillator, a light detector, and a radiation filter arranged therebetween. The scintillator is designed to convert radioactive radiation from a useful radiation source into light. The light detector serves to detect the light from the scintillator and generate a signal from the detected light, from which the level can be calculated.

[0010] The radiation filter, which is arranged between the scintillator and the light detector, is designed to allow the light of the scintillator, which is attributable to the radioactive radiation of the useful radiation source (i.e. is generated by it), to pass largely unhindered towards the light detector and to prevent electromagnetic radiation of a different wavelength from passing through or at least to do so only in a strongly attenuated manner.

[0011] In particular, the radiation filter is designed to prevent unwanted external light, such as ultraviolet light, from hitting the scintillator when the measuring device is open.

[0012] This makes it possible to use a scintillator that is sensitive to UV radiation, as it is protected from it during proper use. For example, the radiation filter is a UV shield that is transparent to electromagnetic radiation in the visible spectrum.

[0013] Currently, scintillators without any protective coating are installed in radiometric level measuring devices. Studies have shown that UV radiation can excite the scintillator and subsequently cause thermoluminescence. Thermoluminescence generates light pulses that can distort the measured value. Since the radiation filter prevents this electromagnetic radiation, which is harmful to the measurement result, from reaching the scintillator, scintillators can be used that enter an excited state when exposed to UV light. These scintillators can exhibit the property that, when the temperature rises to around 50°C, the excited atoms fall back to the lower energy level, emitting interfering light. To prevent this, UV protection is applied as early as possible and remains in place.

[0014] Since the scintillator is protected from this UV radiation, the excitation of the scintillator and thus the falsification of the measured value by ultraviolet radiation can be prevented.

[0015] Thermoluminescent scintillators generate more pulses than normal after exposure to UV radiation. This effect can be amplified when the device is heated. This increase in pulses causes an unwanted measurement error in the radiometric level gauge, which can be prevented or at least significantly reduced by using the radiation filter.

[0016] In particular, the scintillator may be installed in a light-tight manner during operation of the level gauge, so that it can only be reached by the radioactive radiation from the useful radiation source. However, it may occasionally be exposed to daylight, for example, during device production or during servicing when the housing is opened, for example, for an electronics replacement or repair.

[0017] These problems are circumvented by protecting the scintillator from UV radiation. This is achieved by a radiation filter, which specifically blocks UV light while allowing the light from the scintillator used for measurement to pass through to the light detector (photodetector). The light detector can be, for example, a photodiode, a photomultiplier, or a silicon photomultiplier.

[0018] Scintillator materials that can be used include LYSO, LuAg, LFS, NaI, PVT or flexible scintillation fibers.

[0019] According to one embodiment of the invention, the radiation filter is designed to allow the light of the scintillator, which is attributable to the radioactive radiation of the useful radiation source, to pass largely unhindered in the direction of the light detector.

[0020] According to a further embodiment of the invention, the radiation filter is designed to absorb only ultraviolet light. Alternatively, the radiation filter is designed to absorb all electromagnetic radiation with a wavelength different from the wavelength of the scintillator light, which is attributable to the radioactive radiation from the useful radiation source, or exclusively light with a shorter wavelength.

[0021] According to a further embodiment of the invention, the radiation filter is made of glass or plastic. For example, the radiation filter is designed as a plate or disc. For example, it can be part of a sight glass that separates the scintillator from the light detector and ensures that the level measuring device is explosion-proof.

[0022] According to a further embodiment of the invention, the radiation filter is designed as a coating or partial coating of the scintillator. In particular, the radiation filter can be designed to filter out the UV-A spectrum and / or the UV-B spectrum of sunlight. It can also be provided that the radiation filter comprises both a coating of the scintillator and a separate filter element arranged between the scintillator and the light detector.

[0023] According to a further embodiment of the invention, the radiation filter is designed for explosion-proof encapsulation of the electronics of the level measuring device and insulates the electronics in the direction of the scintillator.

[0024] According to a further embodiment of the invention, the scintillator comprises a reference scintillator and a main scintillator, wherein the radiation filter is arranged only in front of the reference scintillator in order to prevent the unwanted electromagnetic radiation “of the other wavelength” from reaching the reference scintillator, at least when both scintillators are installed and the housing is opened.

[0025] A further aspect of the invention relates to a radiometric level measuring system comprising a radiometric level measuring device as described above and below and a useful radiation source.

[0026] Further embodiments of the invention are described below with reference to the figures. Where the same reference numerals are used in the following description of the figures, they denote identical or similar elements. The representations in the figures are schematic and not to scale. Short description of the characters Fig. 1 shows a radiometric level measurement system according to an embodiment of the invention. Fig. 2 shows a radiometric level measuring device according to an embodiment of the invention. Fig. 3 shows a radiometric level measuring device according to another embodiment of the invention. Fig. 4 shows a radiometric level measuring device according to another embodiment of the invention. Detailed description of embodiments

[0027] Fig. Figure 1 shows a radiometric level measurement system with a useful radiation source 107 and a radiometric level measuring device 100. The useful radiation source 107 is located on one side of the container 108, in which a medium (filling material) 109 is stored. The useful radiation source 107 emits radioactive radiation 110, for example gamma radiation, which penetrates the container 108 and, after passing through the container, reaches the detector or scintillator of the radiometric level measuring device 100. The scintillator converts the radiation into light flashes, which are at least partially detected by a light detector and converted into an electrical signal from which the fill level or limit level can be calculated.

[0028] If the entire scintillator is surrounded by the radiation filter (cf. Fig. 4), the absorption properties of the radiation filter are designed such that the radiation from the useful radiation source can pass through the filter largely unhindered. The light generated by the scintillator can also pass through the filter largely unhindered, or at least only slightly attenuated. In particular, UV radiation and any other radiation that could lead to unwanted excitation of the atoms of the scintillator material is largely blocked, i.e., absorbed or filtered out, by the radiation filter.

[0029] Fig. Figure 2 shows a radiometric level measuring device 100 according to an embodiment of the invention. The measuring device has a housing 111 that encloses at least the electronics 105 and the light detector 102. The level measuring device can be read and, if necessary, parameterized via the user interface 106. A scintillator 101 is provided in the lower area of ​​the housing. If necessary, a reference scintillator 104 is also provided, with which the device can be calibrated. This allows temperature influences and aging effects to be compensated.

[0030] A radiation filter 103, for example in the form of a glass pane, which may be coated, is arranged between the scintillators 101, 104 and the light detector 102. The purpose of this radiation filter is to prevent unwanted electromagnetic radiation from reaching the scintillators 101, 104 from above when the housing is open.

[0031] In the embodiment according to Fig. 2, the radiation filter 103 has the same or a slightly larger diameter as the scintillator 101. According to a further embodiment, the optical transmission range is smaller than the scintillator and thus the diameter of the UV filter can also be smaller than that of the scintillator.

[0032] The housing 111 can be constructed in several parts, and the lower portion of the housing, in which the scintillator 101 is arranged, can be removed. In this case, the radiation filter 103 can be inserted into the lower housing part in the form of a sealing window. Thus, when the housing is opened, the radiation filter prevents unwanted electromagnetic radiation from outside from reaching the scintillators 101 and 104.

[0033] This makes it possible to repair the 105 electronics or replace them on-site without having any subsequent problems with thermoluminescence.

[0034] Various materials can be used as UV filters, such as glass, quartz glass, PE film, or plastic. It is important that the visible light from the LYSO at approximately 420 nm passes through the radiation filter so that the scintillator's actual useful signal can be used for the measurement.

[0035] The part of the scintillator that may come into contact with daylight is advantageously covered or shielded with the filter material. The shielding may extend over the entire scintillator, as shown in the Fig. 4, in which both scintillators 101, 104 are completely surrounded by the radiation filter. It can also be provided that the scintillator is protected by the radiation filter only on its upper side (see Fig. 2, in which both scintillators 101, 104 are protected against radiation from above and Fig. 3, in which only the reference scintillator 104 is shielded on its top side).

[0036] The remaining part of the scintillator surface can be housed, for example, in a light-tight foil or in a metal housing.

[0037] The scintillator itself can be coated with the filter material. Alternatively or additionally, the filter material is located in a connecting layer between the light detector 102 and the scintillator 101, 104, for example, in a sight glass used for the flameproof encapsulation of an explosion-proof level measuring device.

[0038] As already mentioned, it is also possible that the radiation filter 103 is used only for the reference scintillator 104.

[0039] Additionally, it should be noted that "comprising" and "having" do not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. Furthermore, it should be noted that features or steps described with reference to one of the above embodiments may also be used in combination with other features or steps of other embodiments described above. Reference signs in the claims are not to be considered limitations.

Claims

[1] Radiometric level measuring device (100), comprising: a scintillator (101, 104) for converting radioactive radiation (110) from a useful radiation source (107) into light; an electronics (105); a light detector (102) for detecting light from the scintillator (101, 104) and for generating a signal from the detected light from which a fill level can be calculated; a radiation filter (103) arranged between the scintillator (101, 104) and the light detector (102) and configured to allow the light of the scintillator (101, 104), which is attributable to the radioactive radiation of the useful radiation source (107), to pass in the direction of the light detector (102) and to prevent electromagnetic radiation of a different wavelength from passing through or to allow it to pass through at least in a strongly attenuated manner; wherein the radiation filter (103) is designed to prevent or at least attenuate ultraviolet light from impinging on the scintillator (101, 104) when replacing the electronics (105). [2] Radiometric level measuring device (100) according to claim 1, wherein the radiation filter (103) is arranged to allow the light of the scintillator, which is attributable to the radioactive radiation of the useful radiation source, to pass through largely unhindered. [3] Radiometric level measuring device (100) according to claim 1 or 2, wherein the radiation filter (103) is designed to absorb ultraviolet light. [4] Radiometric level measuring device (100) according to one of the preceding claims, wherein the radiation filter (103) is designed to absorb all light having a wavelength different from the wavelength of the light of the scintillator which is attributable to the radioactive radiation of the useful radiation source. [5] Radiometric level measuring device (100) according to one of the preceding claims, wherein the radiation filter (103) is made of glass or plastic. [6] Radiometric level measuring device (100) according to one of the preceding claims, wherein the radiation filter (103) is plate-shaped. [7] Radiometric level measuring device (100) according to one of the preceding claims, wherein the radiation filter (103) is designed as a coating of the scintillator (101, 104). [8] Radiometric level measuring device (100) according to one of the preceding claims, wherein the radiation filter (103) is designed for the pressure-tight encapsulation of the electronics of the level measuring device. [9] Radiometric level measuring device (100) according to one of the preceding claims, wherein the scintillator (101, 104) comprises a reference scintillator (104); wherein the radiation filter (103) is arranged only in front of the reference scintillator to prevent the electromagnetic radiation of the other wavelength from reaching the reference scintillator. [10] Radiometric level measuring system, comprising: a radiometric level measuring device (100) according to one of the preceding claims; a useful radiation source (107).

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