CALIBRATION STANDARD, SENSOR ARRANGEMENT AND USE

Abstract

A calibration attachment for adjusting, calibrating, and/or performing a functional check of an optical sensor, which is configured to measure at least one measured variable in a medium by light, wherein the sensor is designed to emit transmitted light of at least one wavelength in the range of 200-700 nm, in particular 200-500 nm, includes a housing and a body, which is arranged in the housing, wherein the body includes praseodymium and cerium, and wherein the body, after excitation with the transmitted light, emits light of a different, in particular longer, wavelength. A sensor arrangement includes such a calibration attachment and use thereof.

Claims

1-20. (canceled)

21. A calibration attachment for adjusting, calibrating, and/or performing a functional check of an optical sensor, which is configured to measure at least one measured variable in a medium using light, wherein the sensor is configured to emit transmitted light of at least one wavelength in a range of 200-700 nm, the calibration attachment comprising: a housing; and a body, which is disposed in the housing such that the transmitted light from the sensor is incident on the body, wherein the body comprises praseodymium and cerium, and wherein the body, upon excitation with the transmitted light, emits light of a different wavelength than the at least one wavelength of the transmitted light from the sensor.

22. The calibration attachment according to claim 21, wherein the emitted light of the different wavelength is a longer wavelength than the transmitted light.

23. The calibration attachment according to claim 1, wherein the emission of the light of the different wavelength occurs within a volume of the body.

24. The calibration attachment according to claim 21, wherein the body is a glass body.

25. The calibration attachment according to claim 24, wherein the glass body is made of barium phosphate glass or quartz glass.

26. The calibration attachment according to claim 24, wherein the glass body is doped with praseodymium and cerium.

27. The calibration attachment according to claim 21, wherein the body is made of a plastic material doped with praseodymium and cerium.

28. The calibration attachment according to claim 21, wherein the housing completely encloses the body, and wherein the housing is hermetically sealed from its environment.

29. The calibration attachment according to claim 21, wherein the body as such is substantially transparent to the transmitted light and the emitted light of the different wavelength.

30. The calibration attachment according to claim 21, wherein the surface of the body is substantially smooth.

31. The calibration attachment according to claim 21, wherein the body is configured as a three-dimensional object.

32. The calibration attachment according to claim 31, wherein the body is configured in a disk-shape or lens-shape.

33. The calibration attachment according to claim 21, wherein the body is mounted in the housing via a mechanical holder.

34. The calibration attachment according to claim 21, wherein the housing comprises a receptacle adapted to retain the sensor.

35. The calibration attachment according to claim 21, wherein the housing is substantially transparent to the transmitted light from the sensor.

36. The calibration attachment according to claim 21, wherein the housing includes an opening such that the transmitted light from the sensor is incident on the body through the opening.

37. A sensor arrangement, comprising: a sensor, comprising: at least one light source, wherein the at least one light source emits transmitted light of at least one wavelength in a range of 200-700 nm; and at least one receiver configured to receive received light of a longer wavelength than the at least one wavelength of the transmitted light; and the calibration attachment according to claim 21, wherein the emitted light from the body is the received light.

38. The sensor arrangement according to claim 37, wherein the longer wavelength of the received light is 250-800 nm.

39. A method of adjusting, calibrating, and/or performing a functional check of an optical sensor, the method comprising: exciting a body doped with praseodymium and cerium with light transmitted from the optical sensor, wherein the optical sensor is configured to emit the transmitted light at at least one wavelength in a range of 200-700 nm.

40. A method of adjusting, calibrating, and/or performing a functional check of an optical sensor, the method comprising: exciting a body doped with praseodymium and cerium with light transmitted from the optical sensor, wherein the optical sensor is configured to determine the content of a polycyclic aromatic hydrocarbon in a sample.

41. A method of adjusting, calibrating, and/or performing a functional check of an optical sensor, the method comprising: exciting a body doped with praseodymium and cerium with light transmitted from the optical sensor, wherein the optical sensor is configured to determine the content of biomass, including chlorophyll and/or algae.

42. A method of adjusting, calibrating, and/or performing a functional check of an optical sensor, the method comprising: exciting a body doped with praseodymium and cerium with light transmitted from the optical sensor, wherein the optical sensor is configured to determine the content of a rhodamine and/or fluorescein, including uranine.

Description

[0047] This is explained in more detail with reference to the following figures.

[0048] FIG. 1 shows the claimed sensor in a symbolic cross section.

[0049] FIG. 2 shows the claimed sensor.

[0050] FIG. 3 shows a cross section through the calibration attachment.

[0051] FIG. 4 shows the body with praseodymium and cerium.

[0052] FIGS. 5a/b show an emission spectrum of the claimed body at an excitation wavelength and a fluorescence spectrum of naphthalene.

[0053] FIGS. 6a-d show an emission spectrum of the claimed body at an excitation wavelength and a fluorescence spectrum of fluorescein, rhodamine, and chlorophyll.

[0054] In the figures, the same features are labeled with the same reference signs.

[0055] The claimed calibration attachment 50 is suitable for adjusting, calibrating, and/or for carrying out a functional check of an optical sensor 100, which is designed to measure at least one measured variable in a medium 5 by means of light, wherein light is transmitted light or received light (see below). The sensor is a fluorescence sensor, which is to be discussed first. The sensor in its entirety is denoted by reference sign 100 and is shown schematically in FIG. 1. FIG. 2 shows the sensor 100 with its housing 10 and an optical window 7.

[0056] In principle, the sensor 100 is suitable for determining the oil-in-water content of a medium 5 or for determining the content of a polycyclic aromatic hydrocarbon in flue gas scrubbing, for example, on ships. These are, for example, naphthalene or phenanthrene. Other applications are however possible. Mention should be made here of the measurement of acetylsalicylic acid or the application in food analysis, e.g., of vitamins, or linoleic acid or material differentiation by means of fluorescence markers.

[0057] Mention should also be made of other applications from the area of biomass, e.g., for detecting chlorophyll in algae. Further examples include the measurement of rhodamines or fluorescein, in particular, uranine, which is explained below with reference to FIG. 5 and FIG. 6.

[0058] FIG. 1 shows the sensor 100 during measurement operation. The calibration operation is discussed below with reference to FIG. 3.

[0059] A light source 1 transmits transmitted light 8 toward the medium 5. The light source 1 is, for example, an LED which emits light of a wavelength of 200-700 nm, e.g., 255 nm. It is also possible to use a laser as the light source, or Xenon or mercury gas discharge lamps (254 nm), optionally with corresponding frequency filters.

[0060] The sensor 100 comprises a data processing unit 4, e.g., a microcontroller. The data processing unit 4 controls the light source 1 to transmit transmitted light 8 toward the medium 5 (measurement operation) or calibration attachment 50 (calibration operation, FIG. 3). The LED 1 is, for example, operated with a settable current source. The amplitude of the transmitted light is approximately proportional to the operating current of the LED 1.

[0061] The transmitted light 8 impinges on a prism 6 at an angle. The prism 6 is a right-angled prism, for example. The base points toward the medium 5 to be measured. A first optical path from the light source 1 to the prism 6 results. The optical path may also contain one or more lenses or filters.

[0062] The transmitted light 8 is partially converted into received light 9 in the medium 5 by fluorescence as a function of the concentration of the substance to be measured in the medium 5. The received light 9 takes the path toward the receiver 2 via the prism 6.

[0063] The receiver 2 is a photodiode, which receives the received light 9 at a wavelength of 250-800 nm. The filter F in FIG. 1 filters, for example, for wavelengths of 340-380 nm.

[0064] In principle, the receiver 9 is able to measure in a broader range, e.g., from 190-1100 nm. A second optical path from the prism 6 to the receiver 2 results. The optical path may also contain one or more lenses or filters. The first and second optical paths are substantially parallel to one another on the side of the prism facing away from the medium.

[0065] The sensor 100 comprises a monitor diode 12, which monitors the transmission power of the LED 1.

[0066] The sensor 100 comprises a temperature sensor 11, which measures the temperature of the light source 1.

[0067] The light source 1, prism 6, and receiver 2 are arranged in a housing 10. The housing is tube-shaped, with a diameter of 35-75 mm. The housing 10 comprises an optical window 7, which is permeable at least to transmitted light 8 and received light 9, wherein the prism 6 and the window 7 are either cemented, glued, joined together, or manufactured from one piece. In one embodiment, the individual components are separate. The distance from the light source 1 or the receiver 2 to the window 7 is approximately 2-6 cm.

[0068] The filter(s) are designed as wavelength filters, e.g., as interference filters.

[0069] FIG. 1 describes the sensor 100 in measurement operation. With reference to FIG. 3, the calibration operation with the calibration attachment 50 is now discussed, wherein, from an optical point of view, the medium 5 is only exchanged with the calibration attachment 50 or body 51.

[0070] By means of the calibration attachment 50, the optical sensor 100 can be adjusted, calibrated, and/or a functional check can be performed. The calibration attachment 50 has a housing 52, which is manufactured from plastic, for example. In principle, the calibration attachment 50 can also be manufactured from a metal such as aluminum or from stainless steel.

[0071] The housing 52 has a receptacle 54 for the sensor 100. Thereby, the sensor 100 reaches the correct location and the transmitted light or received light can reach the body 51 via the optical paths from the light source 1. For this purpose, the housing 52 has an opening 55. In principle, a variant without an opening is also possible; the housing 52 must then be transparent to the corresponding wavelengths of the light source 1 or after conversion. The housing 52 can completely enclose the body 51 (see below). In one embodiment, the housing 52 with the body 51 in its interior is sealed, in particular, hermetically sealed, against the outside world. As a result, no water, steam, dust or the like can penetrate.

[0072] The body 51 is arranged in the interior of the housing 52, wherein the body 51 is fastened via a mechanical holder 53. The body 51 comprises praseodymium and cerium.

[0073] The body 51, comprising the combination of praseodymium and cerium, emits light of a different, in particular longer, wavelength after excitation with the transmitted light, in particular by absorption of the transmitted light. Precisely speaking, it is the material combination of praseodymium and cerium that emits received light, i.e., fluorescent light. This fluorescence is a spontaneous emission of the material combination of praseodymium and cerium after the excitation thereof with transmitted light 8 from the light source 1.

[0074] The body 51 is, for example, designed as a glass body. The glass body is made of an inorganic glass, e.g., of barium phosphate glass or a quartz glass. The glass body 51 is doped with the praseodymium and cerium. The glass as such is transparent to the transmitted and received light; the glass doped with praseodymium and cerium fluoresces. In one embodiment, the body 51 is made of plastic.

[0075] In general, the body 51 per se is substantially transparent to the emission wavelengths used and to the light converted by fluorescence. The body 51 is thus translucent to the transmitted light. In this respect, the body 51 behaves similarly to the medium to be measured.

[0076] The body 51 obviously has volume, i.e., is a three-dimensional object. This has the advantage that the fluorescence can arise from the entire volume of the body 51. In contrast to two-dimensional calibration plates, a larger region (a larger volume) is thus activated for the fluorescence. The fluorescence is thus greater, and a smaller amount of praseodymium and cerium can be used. The calibration attachment 50 can be designed to be smaller, which is advantageous, particularly in the (re)calibration in the field. In addition, two-dimensional calibration plates require a more accurate alignment to the light source, also in order to achieve a reproducible result.

[0077] The sensor arrangement 200 is designed for applications in liquids (i.e., in a volume of measuring medium). The measurement/calibration with the calibration attachment 50 is thus closer to the normal measuring principle, and the measurement value or the sensor behavior in liquids can be precisely reproduced.

[0078] In addition, the spatial alignment of the calibration attachment 50 in the embodiment as a volume body to the sensor can be less accurate.

[0079] The body 51 is designed to be disk-shaped or lens-shaped. However, the basic idea of the present invention also works with fragments or over an arbitrarily shaped part.

[0080] FIG. 3 thus shows the sensor arrangement 200 comprising the sensor 100 and the calibration attachment 50.

[0081] FIG. 4 shows the body 51 with praseodymium.

[0082] FIG. 5a shows an emission spectrum 30 of the body 51 at an excitation wavelength of 254 nm. FIG. 5b shows the corresponding fluorescence spectrum 31 of a PAH, here of naphthalene by way of example. The spectra in FIG. 5b and FIGS. 6b-d are taken from the freely reachable omlc database, found at https://omlc.org/spectra/index.html.

[0083] Instead of a broader emission of a solid that only contains cerium (reference sign 32), the emission spectrum 30 can be tailored, i.e., for example, changed similarly to emission spectra of hydrocarbons such as naphthalene. This is a surprising effect which can only be achieved by the combination of cerium and praseodymium.

[0084] In comparison to a pure cerium or praseodymium doping (reference sign 32 or 33), the absorption by the combination doping of cerium and praseodymium (reference sign 30) becomes more similar to the absorption range of PAHs, such as naphthalene or phenanthrene. The measurements in FIGS. 5a/b show that the absorption edge of cerium and praseodymium is hyposochromically shifted (to shorter wavelengths) in comparison to a pure cerium doping (reference sign 32) at approximately 300 nm.

[0085] FIGS. 6a-d show an emission spectrum 30 of the body 51 at a different excitation wavelength than in FIGS. 5a/b, namely at 440 nm. Shown are the fluorescence spectra 31 of fluorescein (FIG. 6b), rhodamine (FIG. 6c) and chlorophyll (FIG. 6d). It can be seen that in the emission spectrum 30, in the combination of cerium and praseodymium, the bands are at approximately 440 nm and 640 nm, i.e., precisely at the wavelengths at which fluorescein, rhodamine, and chlorophyll have bands.

[0086] This shows that different analytes can be calibrated with a solid standard 51 comprising cerium and praseodymium. Corresponding, possibly different, excitation wavelengths are used, which are used in one or more fluorescence measuring devices 200.

[0087] It has been found that not all lanthanides or all rare-earth metals are equally suitable, despite the similarities that this group has. The combination of praseodymium and cerium has the precisely correct and sufficiently strong fluorescence signal, which a single rare-earth metal, for example, does not have. Depending on the application, see the figures described above, a single rare-earth metal has properties that are completely wrong, i.e., has an unsuitable fluorescence signal. This is, for example, apparent in comparison to the measurement of naphthalene or fluorescein.

LIST OF REFERENCE SIGNS

[0088] 1 Light source [0089] 2 Receiver [0090] 4 Data processing unit [0091] 5 Medium [0092] 6 Prism [0093] 7 Optical window [0094] 8 Transmitted light [0095] 9 Received light [0096] 10 Housing [0097] 11 Temperature sensor [0098] 12 Monitor diode [0099] 30 Emission spectrum of 51 [0100] 31 Absorption spectrum [0101] 32 Emission spectrum of solid with only cerium [0102] 32 Emission spectrum of solid with only praseodymium [0103] 50 Calibration attachment [0104] 51 Body [0105] 52 Housing [0106] 53 Mechanical holder [0107] 54 Receptacle [0108] 55 Opening [0109] 100 Sensor [0110] 200 Sensor arrangement [0111] F Filter