DE102021109258B3 - Procedure for functional testing of a sensor - Google Patents

Abstract

The invention relates to a method for testing the function of a sensor (1), comprising the following steps:
- Providing a sensor (1) with a sensor housing (10), a control unit (20), a cleaning unit (30) and a sound unit (40), wherein the control unit (20) with the sound unit (40) and the cleaning unit (30) connected is,
wherein the cleaning unit (30) has a cleaning element (31) arranged on the outside of the sensor housing (10) for cleaning the sensor housing (10), and an electric motor (32) arranged in the sensor housing (10) for moving the cleaning element (31),
wherein the cleaning element (31) is movable between a first position and a second position,
- activation of the electric motor (32) by the control unit (20) with a control signal (S1) in such a way that the electric motor (32) causes the cleaning element (31) to vibrate in order to emit an acoustic signal (A1),
- detecting the acoustic signal (A1) by the acoustic unit (40),
- Comparing the acoustic signal (A1) with a reference signal (R1) stored in the control unit (20).

Description

The invention relates to a method for testing the function of a sensor.

In analytical measurement technology, especially in the field of water management, environmental analysis, in the industrial sector, e.g. in food technology, biotechnology and pharmacy, as well as for a wide variety of laboratory applications, measurement variables that provide information about the composition or the condition of a measurement medium to be monitored are of great importance. These measured variables can be recorded and/or monitored using various sensors, such as optical or acoustic sensors.

Sensors are arranged in a sensor housing in order to protect the sensor electronics from environmental influences, for example from the measurement medium. Over time, however, it can happen that the sensor housing becomes dirty due to environmental influences. In order for the sensor to always deliver optimal measurement results, the sensor housing, in particular the window of the sensor housing used to detect the sensor, must be cleaned regularly for this reason. If the cleaning of the sensor housing is incorrect, in most cases this has a direct impact on the quality of the measurement results of the sensor. For this reason, it is necessary for the sensor to be checked regularly by hand to ensure that it is functioning properly and, in particular, that its cleaning unit is working properly. However, a manual check of the sensor is associated with a great deal of effort.

DE 10 2016 223 483 A1 discloses a sensor device for a safety system of a motor vehicle. The sensor device has a pressure sensor and a test device for testing the functionality of the sensor device.

DE 10 2018 213 046 A1 discloses a sensor arrangement for a motor vehicle. Sensor arrangement has a cleaning device. The cleaning device includes a cleaning member which abuts a surface of a sensor cover.

It is therefore an object of the invention to propose a method for conveniently and reliably checking that a sensor is functioning correctly.

This object is achieved according to the invention by the method according to claim 1.

• - Bereitstellen eines Sensors mit einem Sensorgehäuse, einer Steuereinheit, einer Reinigungseinheit und einer Schalleinheit,

wobei die Steuereinheit mit der Schalleinheit und der Reinigungseinheit verbunden ist, wobei die Reinigungseinheit ein außen am Sensorgehäuse angeordnetes Reinigungselement zum Reinigen des Sensorgehäuses, sowie einen im Sensorgehäuse angeordneten elektrischen Motor zum Bewegen des Reinigungselements aufweist,
wobei das Reinigungselement zwischen einer ersten Position und einer zweiten Position bewegbar ist,

• - Ansteuern des elektrischen Motors durch die Steuereinheit mit einem Steuersignal derart, dass der elektrische Motor das Reinigungselement in Vibration versetzt, um ein Akustiksignal zu emittieren,
• - Detektieren des Akustiksignals durch die Schalleinheit,
• - Vergleichen des Akustiksignals mit einem in der Steuereinheit hinterlegtem Referenzsignal,
• - Ermitteln eines Funktionszustands des Sensors basierend auf dem Vergleich des Akustiksignals und des Referenzsignals.

The method according to the invention for testing the function of a sensor comprises the following steps:

• - Providing a sensor with a sensor housing, a control unit, a cleaning unit and a sound unit,

wherein the control unit is connected to the sound unit and the cleaning unit, wherein the cleaning unit has a cleaning element arranged on the outside of the sensor housing for cleaning the sensor housing, and an electric motor arranged in the sensor housing for moving the cleaning element,
wherein the cleaning element is movable between a first position and a second position,

• - activation of the electric motor by the control unit with a control signal in such a way that the electric motor causes the cleaning element to vibrate in order to emit an acoustic signal,
• - detection of the acoustic signal by the sound unit,
• - Comparing the acoustic signal with a reference signal stored in the control unit,
• - Determining a functional state of the sensor based on the comparison of the acoustic signal and the reference signal.

The method according to the invention makes it possible to recognize whether the sensor housing can be optimally cleaned by the cleaning unit. Thus, for example, it will be recognized whether the cleaning unit is worn out or defective. In particular, this enables remote diagnosis of the cleaning unit and reduces manual intervention. Ultimately, this makes it possible to always provide the best measurement conditions for the sensor. By monitoring the cleaning unit, it can also be recognized whether the cleaning unit is permanently dirty or whether the sensor is complete, ie no elements of the cleaning unit are missing. The process also makes it easier to remove particularly resistant dirt by the cleaning unit.

According to an embodiment of the invention, the control signal comprises a vibration signal and the vibration signal is an AC voltage signal. The frequency of the alternating voltage signal is selected in such a way that the cleaning element is in the first position or the second position or between the first position and the second position when the electric motor is driven by the vibration signal.

According to an embodiment of the invention, the control signal comprises the vibration signal and a turning signal. The rotation signal is suitable for moving the cleaning element between the first position and the second position when the electric motor is driven with the rotation signal.

According to an embodiment of the invention, the control signal comprises a superimposition of the vibration signal and the rotation signal.

According to an embodiment of the invention, the control signal consists of an alternation between a vibration signal and a rotation signal.
According to one embodiment of the invention, the step of comparing includes comparing an amplitude of the acoustic signal with an amplitude of the reference signal, and/or includes comparing a phase shift between the acoustic signal and the reference signal.

According to one embodiment of the invention, a message is output depending on the determined functional state of the sensor.

According to an embodiment of the invention, the vibration signal is configured prior to the step of driving the electric motor by selecting the frequency of the AC voltage signal such that the acoustic signal is at its maximum.

According to one embodiment of the invention, if the acoustic signal is attenuated compared to the reference signal, the steps of driving, detecting, comparing and determining are repeated until the acoustic signal is identical to the reference signal.

The sensor includes a sensor housing, a control unit, a cleaning unit, and a sonic unit. The cleaning unit has a cleaning element arranged on the outside of the sensor housing for cleaning the sensor housing, and an electric motor arranged in the sensor housing for moving the cleaning element. The cleaning element is movable between a first position and a second position.

The cleaning unit has, for example, an arm with a rubber lip.

The electric motor is, for example, a brushless electric motor.

• - 1: eine schematische Darstellung des erfindungsgemäßen Sensors;
• - 2: eine schematische Darstellung eines Steuersignals, welches ein Vibrationssignal und ein überlagertes Drehsignal aufweist;
• - 3: eine schematische Darstellung eines Steuersignals, welches aus einem abwechselnden Drehsignal und Vibrationssignal besteht.

The invention is explained in more detail with reference to the following description of the figures. Show it:

• - 1 : a schematic representation of the sensor according to the invention;
• - 2 1: a schematic representation of a control signal, which has a vibration signal and a superimposed rotation signal;
• - 3 : a schematic representation of a control signal, which consists of an alternating rotation signal and vibration signal.

1 1 shows a schematic representation of an exemplary embodiment of a sensor 1. The sensor 1 comprises a sensor housing 10, a control unit 20, a cleaning unit 30 and a sound unit 40. The sensor 1 is, for example, a sludge level sensor. However, in addition to the acoustic unit 40, the sensor 1 could have another type of sensor in the sensor housing 10, for example an optical sensor unit such as a radiation emitter and radiation detector.

The sensor housing 10 has a window 11 which is transparent to radiation, in particular sound or electromagnetic radiation. The sensor housing 10 is made of plastic or metal, for example. The window 11 is preferably made of plastic.

The control unit 20 is connected to the sonic unit 40 and the cleaning unit 30 . The control unit 20 includes a memory 21. A reference signal R1 is stored in the memory 21. The control unit 20 is suitable for controlling the cleaning unit 30 and for processing the signals provided by the sound unit 40 .

The cleaning unit 30 has a cleaning element 31 arranged on the outside of the sensor housing 10 and an electric motor 32 arranged in the sensor housing 10 . The electric motor 32 is controlled by the control unit 20 .

The cleaning element 31 is preferably an arm with a rubber lip. Of course, the cleaning element 31 can also have other embodiments. The cleaning element 31 preferably has mechanical contact with the sensor housing 10, in particular with the window 11, for cleaning. However, the cleaning element 31 can also be designed in such a way that no direct contact is made with the sensor housing 10 . In this case, the cleaning takes place e.g. by turbulence, which arises when the cleaning element 31 is moved in the measuring medium. This embodiment has the advantage that the window 11 cannot be scratched by the cleaning element 31 .

The cleaning member 31 is adapted to be moved between a first position and a second position. Moving the cleaning element 31 makes it possible to clean the sensor housing 10, in particular the window 11 of the sensor sor housing 10 to clean. The first position and the second position are preferably chosen such that when the cleaning element 31 is moved between the two positions, the surface of the sensor housing 10 to be cleaned, preferably the window 11, is completely swept over by the cleaning element 31. A complete cleaning of the window 11 by the cleaning unit 30 is thus possible.

The electric motor 32 is mechanically connected to the cleaning element 31 so that the electric motor 32 is able to move the cleaning element 31 . The electric motor 32 is a brushless motor, for example, in which the commutation takes place electronically by the motor control of the control unit 20 . However, the electric motor 32 can also have a motor with a commutator, such as a brush. The electric motor 32 is either a DC motor or an AC motor.

The sound unit 40 is preferably a piezo sound transducer, for example an ultrasonic sensor, or a microphone. The piezo sound converter is suitable for emitting and detecting a sound signal and for forwarding the detected signals to the control unit 20 . The sound unit 40 is preferably arranged on the wall of the sensor housing 10 . Ideally, the sound unit 40 is arranged directly behind the window 11.

The procedure for checking the function of sensor 1 is discussed below.

In a first step, the sensor 1 is provided, i.e. the sensor 1 is ready to be used in a measurement medium. For this purpose, the sensor 1 is in contact with the measurement medium, for example. The sensor 1 is, for example, an ultrasonic sensor which is suitable for emitting an ultrasonic signal and detecting a sound signal.

A step of driving the electric motor 32 by the control unit 20 then takes place. For this purpose, the control unit 20 sends such a control signal S1 that the electric motor 32 causes the cleaning element 31 to vibrate. Due to this vibration, the cleaning element 31 emits an acoustic signal A1, which 1 is shown schematically around the cleaning element 31 . The acoustic signal A1 is preferably emitted by the cleaning element 31 in all directions. In particular, the acoustic signal A1 is emitted by the cleaning element 31 in the direction of the sensor housing 10, preferably in the direction of the window 11. In this step, the sound unit 40 preferably does not emit a sound signal.

The control signal S1 includes a vibration signal V1, which is an AC voltage signal. An alternating current signal is also understood to be an alternating voltage signal. The frequency of the AC voltage signal directly influences the rotational frequency of the electric motor 32. The frequency of the AC voltage signal is selected in such a way that the cleaning element 31 is in the first position or the second position or between the first position and the second position when the electric motor 32 is connected to the Vibration signal V1 is driven. That is, the cleaning member 31 is vibrated due to the vibration signal V1. The frequency is preferably a high frequency, that is to say a frequency which lies outside the control frequency range of the electric motor 32 . The frequency at which the electric motor 32 begins to vibrate depends on the specific embodiment of the electric motor, ie on the motor type and its dimensions.

According to an optional step, before the step of driving the electric motor 32, the vibration signal V1 of the electric motor 32 is configured. In this case, the frequency of the AC voltage signal is selected in such a way that the acoustic signal A1 is at its maximum. This means that the frequency is varied so that a predetermined frequency range is run through, with the acoustic signal A1 being evaluated at the same time by means of the sound unit 40 . The frequency at which the acoustic signal A1 has the greatest amplitude, ie the strongest signal was measured, is preferably selected as the frequency of the alternating voltage signal of the vibration signal V1.

According to one embodiment, the control signal S1 comprises the vibration signal V1 and a rotation signal D1 (see FIG 2 and 3 ). The rotation signal D1 is suitable for moving the cleaning element 31 between the first position and the second position when the electric motor 32 is driven with the rotation signal D1. The rotation signal D1 is a drive signal corresponding to normal operation of the electric motor 32, for example at rated voltage and rated current.

2 12 shows an embodiment of the control signal S1, in which the control signal S1 comprises a superimposition of the vibration signal V1 and the rotation signal D1. The rotation signal D1 is, for example, a sinusoidal signal with a first frequency. The vibration signal V1 is, for example, a signal with a frequency many times higher than the frequency of the rotation signal D1 (see Fig 2 ). A superimposition of the rotation signal D1 with the vibration signal V1 enables the cleaning element 31 to move between the first position and the second position moves and at the same time vibrates when moving. Thus, on the one hand, the sensor housing 10 or the window 11 is cleaned and, at the same time, an acoustic signal A1 is emitted by the cleaning element 31 . The cleaning of the sensor housing 10 thus takes place at the same time as the functional test.

3 shows an embodiment of the control signal S1, in which the control signal S1 consists of an alternation between vibration signal V1 and rotation signal D1. Thanks to this control, it is achieved that the cleaning element 31 moves for a certain time as in normal operation between the first and second position, ie from T0 to T1 and from T2 to T3, and vibrates standing for a certain time, ie from T1 to T2 , as in 3 shown.

This is followed by a step of detecting the acoustic signal A1 by the sound unit 40.

Next follows a step of comparing the acoustic signal A1 with a reference signal R1 stored in the control unit 20 . The reference signal R1 is an acoustic signal that was stored at the factory or was stored by the user. The reference signal R1 is a signal which ensures that the sensor 1 is functioning correctly. During the initial start-up, the user can, for example, generate the reference signal R1 and store it in the memory 21. The reference signal R1 is an acoustic signal which was sent out by a functional cleaning element 31 and was detected by the sound unit 40 .

The step of comparing preferably includes comparing an amplitude of the acoustic signal A1 with an amplitude of the reference signal R1, and/or comparing a phase shift between the acoustic signal A1 and the reference signal R1. Of course, other signal characteristics can also be compared.

Then there is a step of determining a functional state of the sensor 1 based on the comparison of the acoustic signal A1 and the reference signal R1.

Depending on the determined functional state of the sensor 1, a message is preferably output. The message is, for example, a maintenance request, an error message, an acoustic or visual alarm.

If, for example, the rubber lip of the arm of the cleaning element 31 is no longer present or the entire cleaning element 31 is no longer present, no acoustic signal A1 is emitted when the electric motor 32 is activated, which the control unit 20 immediately detects when comparing the supposed acoustic signal A1 with the reference signal R1 notices. In this case, “defective” or “missing cleaning element” is recognized as the state of sensor 1 and output as a message to a control center, display, warning lamp, loudspeaker or other communication element.

If the cleaning element 31 on the shaft of the electric motor 32 is incorrectly oriented, for example, so that the area of the sensor housing 10 to be cleaned, for example the window 11, is not completely swept over by the cleaning element 31 when the cleaning element 31 is moved, this is also the case recognizable by the control unit 20. As in 3 shown, for example, the control unit 20 sends the rotation signal D1 alternating with the vibration signal V1 to the electric motor 32, which is preferably a stepper motor. The stepper motor has, for example, 24 angular steps for one revolution of the axis. The control unit 20 then evaluates the angular steps traversed by the motor and the associated acoustic signal A1. When the cleaning element 31 is placed in the middle of the window 11 directly above the sound unit 40, the acoustic signal A1 is the largest. So if no symmetrical progression of the acoustic signal can be identified in relation to the angular steps of the motor, then the cleaning element 31 does not sweep over the window 11 completely or not evenly. A corresponding message, eg "Please adjust the cleaning element", is issued in this case.

• - ein Festsitzen des Reinigungselements 31 auf dem Sensorgehäuse 10 bzw. dem Fenster 11; in diesem Zustand wird keine Amplitudenänderung des detektieren Akustiksignals A1 erkannt;
• - eine abgenutzte Gummilippe des Reinigungselements 31; in diesem Zustand wird ein schwaches Akustiksignal A1 detektiert;
• - ein verdrecktes Reinigungselement 31; in diesem Zustand wird ein gedämpftes Akustiksignal A1 detektiert.

Further exemplary recognizable states of the cleaning element 31 are:

• - A stuckness of the cleaning element 31 on the sensor housing 10 or the window 11; in this state, no change in amplitude of the detected acoustic signal A1 is detected;
• - a worn rubber lip of the cleaning element 31; in this state, a weak acoustic signal A1 is detected;
• - A dirty cleaning element 31; in this state, a damped acoustic signal A1 is detected.

If a damped acoustic signal A1 is detected, this is usually due to dirt adhering to the cleaning element 31, which has a damping effect.

In this case, the control, detection, comparison and determination steps described above are preferably repeated until the acoustic signal A1 is identical to the reference signal R1, or at least in a permissible range for the acoustic signal A1, for example greater than 70% of the reference signal R1. During activation, the vibration signal V1 is preferably sent for a predetermined first period of time and then the rotary signal D1 for a predetermined second period of time as a control signal S1 to the electric motor 32 for activation, or the rotary signal D1 with the superimposed vibration signal V1 is sent to the electric motor 32 sent for control.

Reference List

1

sensor

10

sensor housing

11

window

20

control unit

21

storage unit

30

cleaning unit

31

cleaning element

32

electric motor

40

sound unit

A1

acoustic signal

D1

turning signal

R1

reference signal

S1

control signal

V1

vibration signal

Claims (9)

Method for functional testing of a sensor (1), comprising the following steps: - Providing a sensor (1) with a sensor housing (10), a control unit (20), a cleaning unit (30) and a sound unit (40), wherein the control unit (20) is connected to the sound unit (40) and the cleaning unit (30), wherein the cleaning unit (30) has a cleaning element (31) arranged on the outside of the sensor housing (10) for cleaning the sensor housing (10), and an electric motor (32) arranged in the sensor housing (10) for moving the cleaning element (31), wherein the cleaning element (31) is movable between a first position and a second position, - activation of the electric motor (32) by the control unit (20) with a control signal (S1) in such a way that the electric motor (32) causes the cleaning element (31) to vibrate in order to emit an acoustic signal (A1), - detecting the acoustic signal (A1) by the acoustic unit (40), - Comparing the acoustic signal (A1) with a reference signal (R1) stored in the control unit (20), - Determining a functional state of the sensor (1) based on the comparison of the acoustic signal (A1) and the reference signal (R1). procedure according to claim 1 , wherein the control signal (S1) comprises a vibration signal (V1) and the vibration signal (V1) is an AC voltage signal, the frequency of the AC voltage signal being selected such that the cleaning element (31) is in the first position or the second position or between the first Position and second position is when the electric motor (32) with the vibration signal (V1) is controlled. procedure according to claim 2 , wherein the control signal (S1) comprises the vibration signal (V1) and a rotation signal (D1), the rotation signal (D1) being suitable for moving the cleaning element (31) between the first position and the second position when the electric motor (32) is controlled with the rotation signal (D1). procedure according to claim 3 , wherein the control signal (S1) comprises a superimposition of the vibration signal (V1) and the rotation signal (D1). procedure according to claim 3 , wherein the control signal (S1) consists of an alternation between vibration signal (V1) and rotation signal (D1). Method according to one of the preceding claims, wherein the step of comparing comprises comparing an amplitude of the acoustic signal (A1) with an amplitude of the reference signal (R1), and/or comparing a phase shift between the acoustic signal (A1) and the reference signal (R1) includes. Method according to one of the preceding claims, a message being output depending on the functional state of the sensor (1) determined. Method according to one of claims 2 until 7 , wherein the vibration signal (V1) is configured prior to the step of driving the electric motor (32) by selecting the frequency of the AC voltage signal such that the acoustic signal (A1) is at a maximum. Method according to one of the preceding claims, wherein if the acoustic signal (A1) is attenuated compared to the reference signal (R1), the steps of driving, of detecting, of comparing and of determining are repeated that many times until the acoustic signal (A1) is identical to the reference signal (R1).

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