Radiation receiving unit and turbidity sensor comprising such a radiation receiving unit

Abstract

The invention relates to a radiation receiving unit (6a), in particular for a turbidity sensor, comprising a base (13) with a light-sensitive radiation receiver (6), a sleeve (14) placed on the base (13), a converging lens (12), a wavelength filter (16) arranged within the sleeve (14), and a plane window element (17), which is arranged within the sleeve (14) and on the inner side of which the wavelength filter (16) is arranged and on the outer side of which the converging lens (12) is arranged, wherein the sleeve (14) is hermetically tightly sealed on both sides by the window element (17) and the base (13) and the converging lens (12) is configured such that it focuses incident light through the wavelength filter (16) onto the radiation receiver (6); the invention also relates to a turbidity sensor (1) comprising such a radiation receiving unit (6a).

Description

[0001] Radiation receiving unit and turbidity sensor with such a radiation receiving unit

[0002] The invention relates to a radiation receiving unit and a turbidity sensor with such a radiation receiving unit.

[0003] A radiation receiver, also known as a photodetector or light sensor, is an electronic component that converts light into an electrical signal using the photoelectric effect. It essentially comprises a base with a light-sensitive radiation receiver and a sleeve mounted on the base. They are used in process engineering, for example, in fluorescence measurement or turbidity measurement.

[0004] Turbidity sensors are designed to analyze the optical properties of a medium, especially a liquid. The primary purpose is to determine the amount of suspended matter. A radiation transmitter transmits light, particularly infrared light, through the medium to a radiation receiver. Suspended matter in the medium attenuates the light due to scattered light and absorption, so the radiation intensity received by the radiation receiver is a measure of the turbidity of the medium. These measuring devices are widely used in process engineering, particularly in the food industry.

[0005] A wavelength filter is often placed upstream of the radiation receivers so that only radiation of a specific wavelength reaches the radiation receiver. This usually filters out visible light and allows only infrared light to pass through. Such a turbidity sensor is known from DE 102004057957 A1. However, this can increase the size of the entire optical structure on the receiver side.

[0006] Typically, the filter is arranged in front of a converging lens, allowing already filtered radiation to pass through the lens. This design is comparatively simple to implement. For comparatively large measuring devices, this correspondingly large optical design does not necessarily pose a problem. However, for smaller measuring devices, where compact design is particularly important, such a design on the receiver side can influence the entire design of the measuring device. The object of the invention is to propose a radiation receiving unit with a wavelength filter in a small and compact design, and thus also to enable a turbidity sensor with such a radiation receiving unit in a small and compact design.

[0007] The object is achieved according to the invention by a radiation receiving unit having the features of claim 1 and a turbidity sensor having the features of claim 4. Advantageous embodiments of the invention are specified in the subclaims.

[0008] According to the invention, the radiation receiving unit comprises a base with a light-sensitive radiation receiver, which is preferably designed as a photodiode, a sleeve mounted on the base, a converging lens, a wavelength filter arranged within the sleeve, and a flat window element arranged within the sleeve. The wavelength filter is arranged on the inside of the window element, and the converging lens is arranged on the outside. The sleeve is hermetically sealed by the window element on the one hand and by the base on the other hand; the window element is preferably sealed by surface adhesive, and the base is preferably sealed by welding.

[0009] This facilitates the assembly of the radiation receiving unit, since the window element acts as a support for the wavelength filter and the converging lens and also facilitates the hermetically sealed closure of the sleeve.

[0010] Compared to the prior art, the wavelength filter is now located behind the converging lens, i.e., between the converging lens and the radiation receiver. Accordingly, the converging lens is then designed to focus incoming light through the wavelength filter onto the radiation receiver.

[0011] Thus, a radiation receiving unit is created that is reduced to a minimum size, so that a turbidity sensor comprising this radiation receiving unit can also be designed in a very small and compact design.

[0012] The invention is explained in more detail below using exemplary embodiments with reference to the drawings.

[0013] They show schematically:

[0014] Figure 1 shows a turbidity sensor according to the invention; Figure 2 shows a sectional view of a sensor tip of the turbidity sensor according to the invention and

[0015] Figure 3 shows an exploded view of a radiation receiving unit according to the invention.

[0016] In the following description of the preferred embodiments, like reference numerals designate like or comparable components.

[0017] Figure 1 shows a turbidity sensor 1 according to the invention in a side view from the outside. The sensor 1 comprises a housing 2. Part of the housing 2 is a process connection 2 in the form of an external thread, with which the sensor 1 is connected to a container containing the medium to be measured, i.e. a pipeline, a tank or the like. This connection is usually made by means of a flange formed on the container or a corresponding adapter. The housing or sensor tip 1a projects accordingly into the container and thus into the medium. The sensor tip 1a has a slit-like recess in the region of two housing sections 2a, 2b, which represents the actual measuring environment.The medium to be measured is then located in this recess and thus in the beam path 7 between a radiation transmitter unit 5a located in the first housing section 2a with a radiation transmitter 5 and a radiation receiver unit 6a located in the second housing section 2b with a radiation receiver 6.

[0018] The turbidity sensor 1 is shown here as a so-called transmitter device, which has no display or operating unit and merely outputs an analog voltage or current signal corresponding to the measurement result via a plug connection 3, which is made available to a higher-level control unit, e.g. a PLC, for further processing and evaluation.

[0019] Figure 2 shows a sectional view of the sensor tip 1a of the turbidity sensor 1 according to the invention. In the housing sections 2a, 2b, in the radiation direction in the area behind the radiation transmitter 5 and in the radiation direction in the radiation direction in the area in front of the radiation receiver 6, a window region 9 is arranged through which the beam path 7 runs. The radiation intensity received by the radiation receiver 6 can then be evaluated as a measure of the turbidity of the medium. Figure 3 shows an exploded view of a radiation receiving unit 6a, also called a photodetector. The radiation receiving unit 6a here refers to the entire component shown in Fig. 3, which essentially consists of a base 13, a sleeve 14 located thereon, and a converging lens 12 opposite the base 13. An electrical connection pin 15 is guided through the base 13 and contacts a circuit board (not shown). The circuit board contains, among other things:the actual radiation receiver 6 is arranged, which is preferably designed as a photodiode.

[0020] The converging lens 12 is connected to a flat window element 17 on the outside by means of an adhesive bond 18. The inside of the window element 17 is connected to a wavelength filter 16 by means of another adhesive bond 18. The adhesive bonds 18 are flat in this case to compensate for any unevenness in the window element 17 and to enable connections without air pockets. The converging lens 12 is designed for the combined thickness of the window element 17 and the wavelength filter 16 and focuses incident light onto the radiation receiver 6. The combination of the converging lens 12, window element 17, and wavelength filter 16 hermetically seals the upper opening of the sleeve 14. The base 13, which is welded to the sleeve 14, hermetically seals the lower opening of the sleeve 14.

[0021] List of reference symbols

[0022] 1 turbidity sensor

[0023] 1a sensor tip

[0024] 2 housings

[0025] 2a Housing section

[0026] 2b Housing section

[0027] 3 plug connection

[0028] 4 Process connection

[0029] 5 radiation transmitters

[0030] 5a Radiation transmitter unit

[0031] 6 radiation receivers

[0032] 6a Radiation receiving unit

[0033] 7 Beam path

[0034] 9 Window area

[0035] 12 Converging lens

[0036] 13 bases

[0037] 14 sleeve

[0038] 15 electrical connections

[0039] 16 wavelength filters

[0040] 17 Window element

[0041] 18 Bonding

Claims

Patent claims 1. Radiation receiving unit (6a), comprising - a base (13) with a light-sensitive radiation receiver (6); - a sleeve (14) placed on the base (13); - a converging lens (12); - a wavelength filter (16) arranged within the sleeve (14) and - a flat window element (17) arranged inside the sleeve (14), on the inside of which the wavelength filter (16) is arranged and on the outside of which the converging lens (12) is arranged, wherein the sleeve (14) is hermetically sealed on both sides by the window element (17) and the base (13) and the converging lens (12) is designed such that it focuses incident light through the wavelength filter (16) onto the radiation receiver (6).

2. Radiation receiving unit according to claim 1, wherein the wavelength filter (16) and the converging lens (12) are each connected to the window element (17) by means of a surface adhesive (18).

3. Radiation receiving unit according to one of the preceding claims, wherein the radiation receiver (6) is designed as a photodiode.

4. Turbidity sensor (1), comprising a radiation transmitter (5) and a radiation receiver (6), which are arranged relative to one another in such a way that they form a beam path (7) for measuring the turbidity of a medium located in the beam path (7), and the radiation intensity received by the radiation receiver (6) is a measure of the turbidity of the medium, wherein the radiation receiver (6) is arranged in a radiation receiving unit (6a) and this radiation receiving unit (6a) is designed according to one of the preceding claims.

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