Light-emitting diode and turbidity sensor having such 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 a light beam emitter, the LED chip (5) being hermetically surrounded by a base (13), a housing and a converging lens, a photodiode (8) being arranged next to the LED chip (5) as a light beam receiver, the light beam receiver detecting the light beam intensity of the LED chip (5) as a reference receiver, the LED chip (5) and the photodiode (8) are surrounded by an aperture element (10) having a through-hole (11) for transmitting a light beam emitted by the LED chip (5) into the environment, but otherwise forming a reflective plane through which the light beam reaches the photodiode (8) from the LED chip (5), while limiting the penetration of scattered light from the environment. The invention also relates to a turbidity sensor having such a light-emitting diode.

Description

[0001] The invention relates to a light emitting diode and a turbidity sensor having the light emitting diode.

[0002] Generally defined, a light-emitting diode (LED) is a semiconductor device that emits light when an electric current flows in the transmission direction. It essentially consists of a semiconductor crystal, which forms the actual light emitter in the form of an LED chip and is typically mounted on a carrier board. Electrical connections to the LED chip are made via bonding wires. The arrangement is surrounded by a light-collecting transparent housing or a sleeve with a separate converging lens.

[0003] Turbidity sensors analyze the optical properties of media, particularly liquids. Their primary focus is determining the proportion of suspended matter. A light source, typically a light-emitting diode (LED), transmits light, typically infrared light, through the medium to a beam receiver. Due to suspended matter in the medium, the light is attenuated by the formation and absorption of scattered light. Therefore, the intensity of the beam received by the beam receiver is a measure of the medium's turbidity.

[0004] Light sources are naturally subject to certain aging effects. To ensure that a reduced light beam intensity reaching the light beam receiver is solely due to the turbidity characteristics of the medium and not due to aging effects, it is known from the prior art, for example from DE 10 2012 007 864 A1, to arrange a further light beam receiver within the turbidity sensor in addition to the light source. This further light beam receiver then serves as a reference receiver, as it detects the light beam intensity of the light source and is largely unaffected by the medium. While slight influences of the medium cannot generally be completely ruled out, such influences are generally insignificant for the measurement.

[0005] The problem here is that the reference receiver can also be affected by interfering light, which would degrade the information about the aging effects of the light source. In addition, the additional components inevitably increase the space requirements.

[0006] The object of the invention is to allow a reference receiver to monitor the intensity of the light beam of a light source in a very compact and space-saving manner and to protect the latter to a large extent from interference light.

[0007] According to the invention, this object is achieved by a light-emitting diode having the features of claim 1 and a turbidity sensor having the features of claim 2. Advantageous embodiments of the invention are specified in the dependent claims.

[0008] First, an LED includes an LED chip as a light beam emitter, which is sealed and enclosed by a base, a housing, and a converging lens. According to the present invention, a photodiode, which serves as a light beam receiver, is positioned adjacent to the LED chip. The light beam receiver acts as a reference receiver to detect the intensity of the LED chip's light beam. The LED chip and photodiode are surrounded by an aperture element. The aperture element has a through-hole for transmitting the light beam emitted by the LED chip into the environment, but otherwise forms a reflective surface. The light beam passes through the reflective surface from the LED chip to the photodiode, while limiting the penetration of scattered light from the environment.

[0009] The core of the present invention is therefore to arrange the reference receiver within the light source (i.e., the light-emitting diode), resulting in a very compact and extremely space-saving design. At the same time, the aperture element limits the penetration of scattered light from the medium, ensuring that the reference receiver receives essentially only the light beam from the light beam transmitter. This allows reliable statements about the current beam intensity of the light beam transmitter or any aging effects of the light beam transmitter. Furthermore, this design is also airtight, so that moisture, for example due to condensation, has no effect on the LED chip, the reference receiver, and other components within the LED.

[0010] A second aspect relates to a turbidity sensor, wherein the light source or the light beam emitter unit is designed as such a light emitting diode according to the invention.

[0011] The reference receiver is advantageously designed as a photodiode. The aperture element is preferably made of a ceramic material.

[0012] The present invention will be explained in more detail below with the aid of embodiments with reference to the accompanying drawings.

[0013] Schematically shown:

[0014] Figure 1 shows a turbidity sensor according to the present invention;

[0015] Figure 2 shows a cross-sectional view of a sensor tip of a turbidity sensor according to the present invention, and

[0016] Figure 3 A cross-sectional view of a light emitting diode according to the present invention is shown.

[0017] In the following description of preferred embodiments, the same reference numerals denote the same or comparable components.

[0018] Figure 1The figure shows an external side view of a turbidity sensor 1 according to the invention. The sensor 1 comprises a housing 2. A part of the housing 2 is a process connection 2 in the form of an external thread, via which the sensor 1 is connected to a container containing the medium to be measured, i.e. a pipe, a tank, etc. In most cases, this connection is achieved by means of a flange formed on the container or a corresponding adapter. The housing or sensor tip 1a accordingly protrudes into the container and thus into the medium. The sensor tip 1a has a slot-shaped recess in the region of the two housing parts 2a, 2b, which represents the actual measuring environment. The medium to be measured is then located in this recess and is therefore located in the beam path 7 between the light beam emitter unit 5a or light source (which is designed as a light-emitting diode with an LED chip 5) in the first housing part 2a and the light beam receiver unit with a light beam receiver 6 in the second housing part 2b.

[0019] In this case, the turbidity sensor is shown as a so-called transmitter device, which has no display or operating unit and outputs via plug connection 3 only an analog voltage or current signal corresponding to the measurement result, which is available to a higher-level control unit, such as a PLC, for further processing and evaluation.

[0020] Figure 2 A cross-sectional view of the sensor tip 1a of the turbidity sensor 1 according to the present invention is shown. Window regions 9 are arranged in the housing parts 2a, 2b in the beam direction in the area behind the light-emitting diode 5a and in the beam direction in the area in front of the light beam receiver 6, respectively, through which the beam path 7 passes. The intensity of the light beam received by the light beam receiver 6 can then be evaluated as a measure of the turbidity of the medium.

[0021] Figure 3 A cross-sectional view of a light-emitting diode 5a according to the present invention, serving as a light beam transmitter unit, is shown. The light-emitting diode 5a essentially comprises a base 13, a sleeve 14 located thereon, and a converging lens 12 facing the base 13 and enclosing the sleeve 14. Various electrical connection pins 15 contacting a printed circuit board 16 extend through the base 13. The LED chip 5, serving as the actual light beam transmitter, and the reference receiver, serving as a photodiode 8, are arranged on the printed circuit board 16.

[0022] The printed circuit board 16, and therefore the LED chip 5 and the reference receiver 8, are covered by an aperture element 10. This aperture element 10 has a through-hole 11, through which the light beam emitted by the light beam emitter 5 passes in the direction of the converging lens 12 and thus in the direction of the medium. The direction of the light beam is schematically indicated by three parallel arrows.

[0023] On the other hand, the reference receiver 8 is arranged between the aperture element 10 and the printed circuit board 16 in such a way that the influence of scattered light from the medium is practically eliminated, and the aperture element 10 essentially forms a reflection plane through which the light beam from the LED chip 5 reaches the reference receiver 8. The reflected light beam is also schematically represented by two arrows. In this way, it is ensured that the reference receiver 8 essentially only receives the light beam from the LED chip 5, thereby providing reliable information about the current light beam intensity of the LED chip 5 or any aging effects of the LED chip 5. At the same time, this structural measure does not result in any significant increase in the overall number of light-emitting diodes 5a as a component, thus maintaining a compact design. However, since the use of this light-emitting diode in the turbidity sensor 1 does not require an externally arranged reference receiver to a certain extent, the turbidity sensor 1 itself can be designed to be very compact and space-saving.

[0024] Reference Signs List

[0025] 1 Turbidity sensor

[0026] 1a Sensor tip

[0027] 2 Shell

[0028] 2a Housing

[0029] 2b Housing

[0030] 3 plug connections

[0031] 4 Process connection

[0032] 5 LED chips, beam emitters

[0033] 5a Beam emitting unit, light source

[0034] 6-beam receiver

[0035] 7 Beam Path

[0036] 8 Reference Receiver

[0037] 9 Window Area

[0038] 10 Aperture element

[0039] 11 through holes

[0040] 12 Converging lens

[0041] 13 base

[0042] 14 Sleeve

[0043] 15 Electrical Connection

[0044] 16 printed circuit boards

Claims

1. A light emitting diode (5a), comprising an LED chip (5) as a light beam emitter, in, The LED chip (5) is sealed and surrounded by a base (13), a housing and a converging lens. A photodiode (8) serving as a beam receiver is arranged next to the LED chip (5), and the beam receiver serves as a reference receiver to detect the beam intensity of the LED chip (5). The LED chip (5) and the photodiode (8) are surrounded by an aperture element (10), which has a through hole (11) for transmitting the light beam emitted by the LED chip (5) into the environment, but otherwise forms a reflection plane, through which the light beam reaches the photodiode (8) from the LED chip (5) while limiting the penetration of scattered light from the environment.

2. The light-emitting diode (5a) according to claim 1, in, The aperture element (10) is made of ceramic material.

3. A turbidity sensor comprising a light beam transmitter unit (5a) and a light beam receiver unit (6a) arranged relative to each other to form a light beam path (7) for measuring the turbidity of a medium located in the light beam path (7), and wherein the intensity of the light beam received by the light beam receiver unit (6a) is a measure of the turbidity of the medium, It is characterized by: The light beam emitter unit (5a) is configured as a light emitting diode according to any of the preceding claims.

4. The turbidity sensor according to claim 3, It is characterized by: The light beam receiver (6) is designed as a photodiode.

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