Light-emitting diode and turbidity sensor comprising such a light-emitting diode

Abstract

The invention relates to a light-emitting diode (5a), in particular for a turbidity sensor, comprising an LED chip (5) as radiation emitter, wherein the LED chip (5) is hermetically enclosed by a base (13), a housing and a converging lens, wherein a photodiode (8) as radiation receiver is arranged next to the LED chip (5) and as reference receiver detects the radiation intensity of the LED chip (5), wherein the LED chip (5) and the photodiode (8) are enclosed by a stop element (10), which has a through-hole (11) for forwarding the beams emitted by the LED chip (5) into the surroundings, but for the rest forms a reflection plane that causes the beams from the LED chip (5) to pass to the photodiode (8) and at the same time limits the intrusion of stray light from the surroundings. The invention additionally relates to a turbidity sensor comprising such a light-emitting diode.

Description

[0001] LED and turbidity sensor with such a LED

[0002] The invention relates to a light-emitting diode and a turbidity sensor with such a light-emitting diode.

[0003] A light-emitting diode, or LED for short, is generally defined as a semiconductor component that emits light when an electric current flows in the forward direction. It essentially consists of a semiconductor crystal, which, in the form of an LED chip, forms the actual radiation emitter and is usually arranged on a carrier plate. The LED chip is electrically connected via bonding wires. This assembly is encased in a light-concentrating, transparent housing or a sleeve with a separate converging lens.

[0004] Turbidity sensors are designed to analyze the optical properties of a medium, particularly a liquid. The primary goal is to determine the amount of suspended matter. A light source, typically an LED, 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 medium's turbidity.

[0005] The light source is naturally subject to a certain aging effect. To ensure that a reduced radiation intensity arriving at the radiation receiver is caused exclusively by the turbidity properties of the medium and is not also the result of an aging effect, it is known from the prior art, for example from DE 10 2012 007 864 A1, to arrange an additional radiation receiver within the turbidity sensor next to the light source. This additional radiation receiver then serves as a reference receiver, detecting the radiation intensity of the light source largely unaffected by the medium. Often, a slight influence by the medium cannot be completely ruled out, but in this case, it is not significant for measurement purposes.

[0006] The problem here is that the reference receiver can also be subject to stray light, which would then reduce its reliability regarding the aging effects of the light source. Furthermore, the additional component inevitably increases the space required.

[0007] The object of the invention is to monitor the radiation intensity of the light source by a reference receiver in a very compact and space-saving manner and to protect it largely from the influence of stray light.

[0008] The object is achieved according to the invention by a light-emitting diode having the features of claim 1 and by a turbidity sensor having the features of claim 2. Advantageous embodiments of the invention are specified in the subclaims.

[0009] First, the LED comprises an LED chip as a radiation transmitter, which is hermetically enclosed by a base, a housing and a collecting lens.

[0010] According to the invention, a photodiode is arranged next to the LED chip as a radiation receiver, which acts as a reference receiver to detect the radiation intensity of the LED chip. Both the LED chip and the photodiode are enclosed by a diaphragm element, which has a perforation for transmitting the rays emitted by the LED chip into the environment. Furthermore, the diaphragm element forms a reflection plane through which the rays pass from the LED chip to the photodiode, while simultaneously limiting the penetration of stray light from the environment.

[0011] The core of the invention is therefore to arrange the reference receiver within the light source, i.e., the light-emitting diode, thus realizing a very compact and extremely space-saving design. At the same time, the aperture element limits the penetration of stray light from the medium, ensuring that the reference receiver essentially only receives the radiation from the radiation transmitter, thus allowing reliable information about the current radiation intensity of the radiation transmitter and any aging effects of the radiation transmitter. Furthermore, such a design is also hermetically sealed, so that moisture, which can arise, for example, through condensation, has no effect on the LED chip, the reference receiver, or the other components within the LED.

[0012] A second aspect relates to a turbidity sensor in which the light source or radiation transmitter unit is embodied as a light-emitting diode according to the invention. Advantageously, the reference receiver is embodied as a photodiode. The aperture element is preferably made of a ceramic material.

[0013] The invention is explained in more detail below using exemplary embodiments with reference to the drawings.

[0014] They show schematically:

[0015] Figure 1 shows a turbidity sensor according to the invention;

[0016] Figure 2 is a sectional view of a sensor tip of the turbidity sensor according to the invention and

[0017] Figure 3 shows a light-emitting diode according to the invention in a sectional view.

[0018] In the following description of the preferred embodiments, like reference numerals designate like or comparable components.

[0019] 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 onto the container or a corresponding adapter. The housing or sensor tip 1a projects into the container and thus into the medium. The sensor tip 1a has a slit-like recess in the area 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 or 5b located in the first housing section 2a.Light source, which is designed as a light-emitting diode with an LED chip 5, and a radiation receiver unit with a radiation receiver s located in the second housing section 2b.

[0020] The turbidity sensor is depicted here as a so-called transmitter device, which has no display or operating unit and simply 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. Figure 2 shows a sectional view of the sensor tip 1a of the turbidity sensor 1 according to the invention. A window region 9 is arranged in each of the housing sections 2a, 2b, in the area behind the light-emitting diode 5a in the radiation direction, and in the area in front of the radiation receiver 6 in the radiation direction, through which the beam path 7 passes. The radiation intensity received by the radiation receiver 6 can then be evaluated as a measure of the turbidity of the medium.

[0021] Figure 3 shows a sectional view of an inventive light-emitting diode 5a as a radiation transmitter unit. The light-emitting diode 5a essentially consists of a base 13, a sleeve 14 located thereon, and a converging lens 12 opposite the base 13 and closing the sleeve 14. Various electrical connection pins 15, which contact a circuit board 16, are routed through the base 13. Arranged on the circuit board 16 are, among other things, the LED chip 5 as the actual radiation transmitter and the reference receiver 8 embodied as a photodiode.

[0022] The circuit board 16, and thus also the LED chip 5 and the reference receiver 8, are covered by a diaphragm element 10. This diaphragm element 10 has a through-hole 11 through which the rays emitted by the radiation transmitter 5 are passed toward the converging lens 12 and thus toward the medium. The radiation direction is indicated schematically by the three parallel arrows.

[0023] The reference receiver 8, on the other hand, is arranged between the aperture element 10 and the circuit board 16 in such a way that the influence of stray light from the medium is practically excluded, and the aperture element 10 essentially forms a reflection plane through which the rays from the LED chip 5 reach the reference receiver 8. The reflected radiation is also schematically represented by two arrows. In this way, it can be ensured that the reference receiver 8 essentially only receives the radiation from the LED chip 5, thus allowing a reliable statement about the current radiation intensity of the LED chip 5 or any aging effects of the LED chip 5. At the same time, this design measure does not lead to any significant enlargement of the entire light-emitting diode 5a as a component, so that a compact design is still possible.Since, when using this LED in a turbidity sensor 1, no externally arranged reference receiver is necessary, the turbidity sensor 1 itself can be designed to be very compact and space-saving.

[0024] List of reference symbols

[0025] 1 turbidity sensor

[0026] 1a sensor tip

[0027] 2 housings

[0028] 2a Housing section

[0029] 2b Housing section

[0030] 3 plug connection

[0031] 4 Process connection

[0032] 5 LED chip, radiation transmitter

[0033] 5a Radiation transmitter unit, light source

[0034] 6 radiation receivers

[0035] 7 Beam path

[0036] 8 reference recipients

[0037] 9 Window area

[0038] 10 aperture element

[0039] 11 Perforation

[0040] 12 Converging lens

[0041] 13 bases

[0042] 14 sleeve

[0043] 15 electrical connections

[0044] 16 circuit board

Claims

Patent claims 1. Light-emitting diode (5a), comprising an LED chip (5) as a radiation transmitter, wherein the LED chip (5) is hermetically enclosed by a base (13), a housing and a converging lens, wherein a photodiode (8) is arranged next to the LED chip (5) as a radiation receiver, which photodiode detects the radiation intensity of the LED chip (5) as a reference receiver, wherein the LED chip (5) and the photodiode (8) are enclosed by a diaphragm element (10) which has a through-hole (11) for transmitting the rays emitted by the LED chip (5) into the environment, but otherwise forms a reflection plane through which the rays pass from the LED chip (5) to the photodiode (8) and at the same time the penetration of scattered light from the environment is limited.

2. Light-emitting diode (5a) according to claim 1, wherein the aperture element (10) consists of a ceramic material.

3. Turbidity sensor, comprising a radiation transmitter unit (5a) and a radiation receiver unit (6a), 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 unit (6a) is a measure of the turbidity of the medium, characterized in that the radiation transmitter unit (5a) is designed as a light-emitting diode according to one of the preceding claims.

4. Turbidity sensor according to claim 3, characterized in that the radiation receiver (6) is designed as a photodiode.

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