阅读说明：本技术 监测振动传感器的状况 (Monitoring conditions of a vibration sensor ) 是由 卡伊·乌彭坎普 克里斯蒂安·施特里马特 阿尔明·韦内特 萨沙·德安杰利科 于 2020-04-08 设计创作，主要内容包括：本发明涉及一种用于监测振动传感器(1)的状况的方法,以便确定和/或监测容纳器(2a)中的介质(2VC)的至少一个过程变量,所述传感器具有至少一个具有机械可振荡单元(4)的传感器单元(3),该方法包括以下方法步骤：-借助于激励信号(U-(A))激励机械可振荡单元(4)以执行机械振荡,并以接收信号(U-(E))的形式接收机械振荡；-确定接收信号(U-(E))的振幅(A)的测量值和频率(f)的测量值；-将振幅(A)和频率(f)的测量值分别与振幅的参考值(A-(ref))和频率的参考值(f-(ref))进行比较；以及-根据比较确定状况指示符。(The invention relates to a method for monitoring the condition of a vibration sensor (1) for determining and/or monitoring at least one process variable of a medium (2VC) in a receptacle (2a), said sensor having at least one sensor unit (3) having a mechanically oscillatable unit (4), comprising the following method steps: by means of an excitation signal (U) A ) Exciting the mechanically oscillatable unit (4) to perform mechanical oscillations and to receive a signal (U) E ) Receive the mechanical oscillation; -determining a received signal (U) E ) A measurement of the amplitude (a) and a measurement of the frequency (f); -associating the measured values of amplitude (a) and frequency (f) respectively with a reference value of amplitude (a) ref ) And a reference value (f) of the frequency ref ) IntoPerforming line comparison; and-determining a condition indicator from the comparison.)

1. A method for monitoring the condition of a vibration sensor (1) for determining and/or monitoring at least one process variable of a medium (2) in a receptacle (2a) and having at least one sensor unit (3) with a mechanically oscillatable unit (4), comprising the method steps of:

by means of an excitation signal (U)_A) Exciting the mechanically oscillatable unit (4) such that mechanical oscillation is performed, and receiving a signal (U)_E) Is configured to receive the mechanical oscillation in the form of,

-determining the received signal (U)_E) A measured value of the amplitude (A) and a measured value of the frequency (f),

-comparing the measured value of the amplitude (A) and the measured value of the frequency (f) with a reference value of amplitude (A)_ref) And a reference value (f) of the frequency_ref) Making a comparison, and

-ascertaining a condition indicator from the comparison.

2. The method of claim 1, wherein the first and second light sources are selected from the group consisting of,

wherein measured values (f, A) and reference values (f) of the frequency and/or amplitude are determined_ref、A_ref) And wherein the condition indicator is ascertained based on the deviation.

3. The method of claim 2, wherein the first and second light sources are selected from the group consisting of,

in this case, it is ascertained whether a deviation of the frequency (f) and/or of the amplitude (A) exceeds a predeterminable limit value.

4. Method according to at least one of the preceding claims,

wherein the reference value (A) of the amplitude_ref) And a reference value (f) of the frequency_ref) Are values of amplitude and frequency corresponding to the resonant oscillation of the oscillatable unit (4) in the fundamental oscillation mode and in air.

5. Method according to at least one of the preceding claims,

wherein the mechanically oscillatable unit (4) is excited in air to a mechanical resonant oscillation in the basic oscillation mode, and wherein the reception signal represents a resonant oscillation of the oscillatable unit (4) in the basic oscillation mode.

6. Method according to at least one of the preceding claims,

wherein the status indicator is: information about accretion, corrosion or wear in the area of the oscillatable unit (4); information about defects in the area of a drive/receive unit (5) by means of which excitation of the oscillatable unit (4) occurs such that mechanical oscillation is performed; or information about defects of an electronic device (6) of the sensor (1) comprising the oscillatable unit (4).

7. Method according to at least one of the preceding claims,

wherein the oscillatable unit (4) is an oscillating fork comprising a membrane (7) and two oscillating tines (8a, 8b) fixed to the membrane (7).

8. Method according to at least one of the preceding claims,

wherein the measured value of the amplitude (A) is not detectable and the measured value of the frequency (f) is less than the reference value (f)_ref) In the case of (2), then indicating the presence of corrosion and/or wear on the oscillating tines (8a, 8b) and/or the presence of hard accretions in the area of the film (7).

9. Method according to at least one of the claims 1 to 8,

wherein the measured value of the amplitude (A) is compared with a reference value (A)_ref) The deviation between the two is less than a predeterminable limit value and the measured value of the frequency (f) is less than a reference value (f)_ref) In the case of (2), then indicating the presence of hard accretions in the area of the oscillating tines (8a, 8b) and/or the presence of corrosion and/or wear in the area of the membrane (7).

10. Method according to at least one of the claims 1 to 8,

wherein the measured value at the amplitude (A) and the measured value at the frequency (f) are smaller than their reference values (f)_ref、A_ref) In the case of (2), then indicating the presence of soft accretions in the area of the oscillating tines (8a, 8b) and/or the presence of media residues in the area of the oscillatable unit (4).

11. Method according to at least one of the claims 1 to 8,

wherein the measured value at the amplitude (A) is smaller than the reference value (A)_ref) And the measured value of the frequency (f) is compared with a reference value (f)_ref) If the deviation between the values is less than a predeterminable limit value, this indicates the presence of a defect in the region of the drive/receive unit (5), in particular in the region of at least one piezoelectric element of the drive/receive unit (5), and/or in the region of the electronic component (6).

12. Method according to at least one of the preceding claims,

wherein the method is implemented according to the IO-Link standard.

Technical Field

The invention relates to a method for monitoring the condition of a vibration sensor for determining and/or monitoring at least one process variable, in particular a physical or chemical process variable, of a medium in a receptacle. The vibration sensor comprises a sensor unit with a mechanically oscillatable unit. For example, the process variable to be monitored can be the level or flow of the medium, but also the density or viscosity of the medium. For example, the receptacle is a container or a line.

Background

Vibration sensors are widely used in process and/or automation technology. In the case of a fill level measuring device, it has at least one mechanically oscillatable unit, for example an oscillating fork, a single tine or a membrane. This is stimulated during operation by means of a drive/receiving unit, usually in the form of an electromechanical transducer unit, so that a mechanical oscillation is performed. The electromechanical transducer unit may in turn be a piezoelectric actuator or an electromagnetic actuator, for example.

Corresponding field devices are manufactured by the applicant in a wide variety and are sold, for example, under the trademarks LIQUIPHANT and SOLIPHANT in the case of level measuring devices. The basic measuring principle is known in principle from a large number of publications. The drive/receiving unit excites the mechanically oscillatable unit by means of the electrical excitation signal such that a mechanical oscillation is performed. Instead, the drive/receive unit may receive the mechanical oscillations of the mechanically oscillatable unit and convert them into electrical receive signals. The driving/receiving unit may be a separate driving unit and a separate receiving unit, or may be a combined driving/receiving unit.

In this case, the drive/receiving unit is in many cases part of a feedback electrical oscillating circuit, by means of which circuit an excitation of the mechanically oscillatable unit takes place such that a mechanical oscillation is performed. For example, for resonant oscillation, the following oscillation circuit conditions must be satisfied: the amplification factor is ≧ 1 and the sum of all phases present in the oscillating circuit must be a multiple of 360 °.

In order to excite and satisfy the oscillation circuit conditions, a certain phase shift between the excitation signal and the reception signal must be ensured. Therefore, a predeterminable value for the phase shift, i.e. a desired value for the phase shift between the excitation signal and the received signal, is frequently set. Known in the prior art for this purpose are the most diverse solutions, including both analog and digital methods. In principle, the setting of the phase shift can be carried out, for example, by using a suitable filter or controlled by means of a control loop to a predeterminable phase shift, desired value. It is known, for example, from DE102006034105a1 to use a tuneable phase shifter. In contrast, an additional integration of an amplifier with an adjustable amplification factor for additional control of the oscillation amplitude is described in DE102007013557a 1. DE102005015547a1 proposes the use of an all-pass filter. Furthermore, phase shifts can be established by means of so-called frequency sweeps, as disclosed, for example, in DE102009026685a1, DE102009028022a1 and DE102010030982a 1. However, the phase shift can also be controlled to a predeterminable value by means of a phase control loop (PLL). This excitation method is the subject of DE102010030982a 1.

The excitation signal as well as the received signal are characterized by a frequency ω, an amplitude a and/or a phase Φ. Accordingly, the variation of these variables is usually taken into account to determine a specific process variable, for example a predetermined level of the medium in the container or the density and/or viscosity of the medium or the flow rate of the medium through the pipe or line. For example, in the case of a vibration limit switch for liquids, it is possible to distinguish whether the oscillatable unit is covered by the liquid or free-oscillating. The two states (free state and covered state) are distinguished in this case, for example, on the basis of different resonance frequencies (i.e. frequency shifts). The density and/or viscosity can then be ascertained with such a measuring device only when the oscillatable unit is covered with a medium, as described, for example, in DE10050299a1, DE102007043811a1, DE10057974a1, DE102006033819a1 and DE102015102834a 1.

In order to ensure reliable operation of the vibration sensor, the prior art provides different methods by means of which information about the condition of the vibration sensor can be obtained. A method for monitoring the mass of a vibration sensor is known, for example, from DE102005036409a 1. A measuring device comprises at least one power measuring unit which monitors the energy requirement of an exciter/receiving unit at least for the case of resonant oscillations. In this way, information about the mass of the vibration sensor can be obtained. The higher the mass, the less energy is required to excite the resonant oscillation. Thus, if the energy required to excite resonant oscillations rises within a predeterminable period of time or exceeds a predeterminable limit value of the mass ascertained during the production of the sensor, it can be concluded that defects, accumulations, etc. are present in the region of the oscillatable unit.

Furthermore, a vibration sensor with an electronic unit comprising a phase measuring unit, a tuneable phase shifter and a phase adaptation unit controlling the setting of the phase shift between the excitation signal and the received signal is known from DE102007008669a 1. The control parameters can be updated and stored at predeterminable time intervals during operation of the sensor. Further, monitoring of the condition may be performed based on a comparison between the stored control parameters and the current control data.

DE102017111392a1 describes a method for monitoring the condition of a vibration sensor, in which case information about the condition of the sensor is ascertained as a function of the excitation frequency on the basis of the frequency spectrum of the received signal or a variable derived therefrom.

From DE102017102550a 1a method is known for monitoring the condition of a vibration sensor on the basis of a comparison of measured values (e.g. frequency) of physical and/or chemical variables of a sensor characteristic of the sensor with reference values. In this way, information can be obtained about corrosion, wear or accretion in the area of the oscillatable unit, for example.

With the known methods, however, it is often only possible to say that there is in principle corrosion, wear or accretion. In contrast, precise localization and precise determination of the cause of the changed oscillation behavior of a particular sensor cannot generally be ascertained from the measurement signal alone.

Disclosure of Invention

It is therefore an object of the present invention to provide a method for monitoring the condition of a vibration sensor, which method is capable of monitoring the condition as accurately as possible.

According to the invention, this object is achieved by a method for monitoring the condition of a vibration sensor for determining and/or monitoring at least one process variable of a medium in a receptacle and having at least one sensor unit with a mechanically oscillatable unit, comprising the following method steps:

-exciting the mechanically oscillatable unit by means of the excitation signal such that a mechanical oscillation is performed, and receiving the mechanical oscillation in the form of the reception signal,

-determining a measure of the amplitude and a measure of the frequency of the received signal,

-comparing the measured values of amplitude and frequency with reference values of amplitude and frequency, and

-ascertaining a condition indicator from the comparison.

Since both frequency and amplitude are taken into account, a particularly precise monitoring of the condition can be achieved. Advantageously, there is no need to interrupt the process in which the sensor is located when monitoring conditions. By recording the frequency and amplitude measurements, the sensor can be observed over time.

Furthermore, the method of the present invention advantageously enables the performance of predictive maintenance. Based on the determined measurements of amplitude and frequency, it can be estimated, for example, when the sensor will need to be serviced.

In an embodiment of the method, a deviation between the measured value of the frequency and/or amplitude and the reference value is determined, and a condition indicator is ascertained on the basis of the deviation. For this purpose, it is advantageous to ascertain whether the deviation between the measured value of the frequency and/or amplitude and the reference value exceeds a predeterminable limit value.

In a further embodiment of the method, the reference values for amplitude and frequency are in each case values (in particular measured values) for amplitude and frequency, which correspond to the resonant oscillation of the oscillatable unit in the fundamental oscillation mode and in air. For example, the reference value can be ascertained during production of the sensor and stored, for example, in a memory unit, a database or a data table. The reference value in turn corresponds to the lead condition of the sensor. However, the reference value can also be ascertained at the factory of the customer and after installation in the container. Since the reference value of each sensor is determined individually, common variations in the values due to production tolerances can be directly dealt with.

An embodiment of the method comprises: the mechanically oscillatable unit is excited in air to a mechanical resonant oscillation in the fundamental oscillation mode, and wherein the received signal represents the resonant oscillation of the oscillatable unit in the fundamental oscillation mode. Therefore, in this case, when the oscillatable unit is not covered with the medium, the monitoring of the condition is performed.

In a preferred embodiment of the method, the condition indicator is: information about accretion, corrosion or wear in the area of the oscillatable unit; information about defects in the area of the drive/receive unit by means of which excitation of the oscillatable unit occurs such that mechanical oscillation is performed; or information about defects of the electronics of the sensor comprising the oscillatable unit.

Advantageously, the oscillatable unit is an oscillating fork comprising a membrane and two oscillating tines fixed to the membrane.

Condition monitoring according to the invention provides a plurality of different information about the oscillatable unit, some particularly preferred variants of condition monitoring being as follows:

embodiments of the method provide that, in the absence of a discernible measurement of amplitude and a measurement of frequency less than a reference value, then corrosion and/or wear is indicated on the oscillating tines and/or hard accretions are present in the film area.

An embodiment of the method provides that, in the case of a deviation of the measured value of the amplitude from the reference value which is less than a predeterminable reference value and the measured value of the frequency which is less than a limit value, a hard accretion in the region of the oscillating tines and/or corrosion and/or wear in the region of the film is indicated.

Another embodiment of the method comprises: when the measured values of amplitude and frequency are less than their reference values, it is indicative of soft accretion being present in the area of the oscillating tines and/or a media residue being present in the area of the oscillatable unit.

A further embodiment includes that, if the measured value of the amplitude is smaller than the reference value and the deviation of the measured value of the frequency from the reference value is smaller than a predefinable limit value, this may indicate the presence of a defect in the region of the drive/receive unit (in particular in the region of the at least one piezoelectric element of the drive/receive unit) and/or the presence of a defect in the region of the electronic unit.

In the case of an oscillatable unit performing oscillations with a predeterminable shedding frequency, it is then possible to indicate, for example, the presence of defects of the drive/receive unit, poor contacts, cable breaks, jamming of the oscillating tines or defects in the electronics unit.

In case there is no detectable measurement of the frequency, a defect of the electronic unit may be indicated.

Another preferred embodiment comprises implementing the method according to the IO-Link standard. The IO-Link standard is defined in the IEC61131-9 standard, a technology widely distributed in automation technology for connecting intelligent actuators and sensors. An IO-Link relates to a serial point-to-point connection via which data is transmitted between a so-called IO-Link master station and one or more connected IO-Link devices as slave stations. For example, the master station is a field bus module or a PLC interface module having one or more ports for connecting IO-Link devices. The IO-Link Master station represents the connection between the IO-Link device and the automation system and communicates, for example, via a field bus. In contrast, an IO-Link device is a sensor, actuator, interactive element, or display unit. In this case, the IO-Link device is described via a so-called IODD description file (IO-Link device description) containing device-specific configuration parameters, for example, of the IO-Link device.

In summary, the present invention enables accurate monitoring of the condition of a vibration sensor. Monitoring is very easy to implement and can be performed while the process continues. Since both frequency and amplitude are considered, the condition can be accurately monitored, based on which not only the presence of a defect can be indicated, but also the location of the defect within the sensor and the cause of a change in a particular behavior can be determined.

Drawings

The invention and its advantages will now be described more precisely on the basis of the accompanying drawings, which show the following:

fig. 1 shows a vibration sensor according to the prior art, an

Fig. 2 shows an oscillatable unit of a vibration sensor in the form of an oscillatory fork.

Detailed Description

Fig. 1 shows a vibration sensor 1, which comprises a sensor unit 3 having an oscillatable unit 4 in the form of an oscillatory fork, which is partially immersed in a medium 2 located in a container 2 a. The oscillatable unit 4 is excited by means of the exciter/receiving unit 5 such that a mechanical oscillation is performed. The exciter/receiving unit 5 may be, for example, a piezoelectric stack or a bimorph driver. However, it should be understood that other embodiments of the vibration sensor are also within the scope of the present invention. An electronic unit 6 is also included, by means of which signal recording, evaluation and/or feeding takes place.

Fig. 2 shows, in a side view, an oscillatable unit 4 in the form of an oscillatory fork, such as is used in the vibration sensor 1 sold by the applicant under the trademark LIQUIPHANT. The oscillating fork 4 comprises two oscillating tines 8a, 8b formed on the film 7, at the ends of which two paddles 9a, 9b are formed. The oscillating tines 8a, 8b together with the paddles 9a, 9b are also commonly referred to as fork tines. In order for the mechanically oscillatable unit 4 to perform a mechanical oscillation, a force is exerted on the membrane 7 by means of a drive/receiving unit 5 which is fixed by material bonding to the side of the membrane 7 opposite to the side carrying the oscillating tines 8a, 8b. The driving/receiving unit 5 is an electromechanical transducer unit and includes, for example, a piezoelectric element or an electromagnetic driver (not shown). The drive/receive unit 5 is composed of separate drive and receive units, or a combined drive/receive unit. In the case of a drive/receive unit 5 comprising a piezoelectric element 9, the force exerted on the membrane 7 is generated by applying an excitation signal U, for example in the form of an alternating voltage_AAnd then generated. The change in the applied voltage affects the change in the geometry of the drive/receive unit 5, i.e. the contraction or expansion within the piezoelectric element, so that an alternating voltage is applied as the excitation signal U_ACausing oscillation of the membrane 7 connected to the drive/receiving unit 5 by material bonding. Conversely, the mechanical oscillations of the oscillatable unit are transmitted via the membrane to the drive/receiving unit 5 and converted into an electrical receiving signal U_E. May then be based on the received signal U_ETo determine a specific process variable, for example a predeterminable level of the medium 2 in the container 2a, or a density or viscosity of the medium 2.

The options for monitoring the condition of the vibration sensor will now be explained based on comparing the measured frequency f and the measured amplitude a of the oscillatable unit 4 for excitation in the basic oscillation mode of the oscillatable unit 4. In a first step, a reference value f for the amplitude and frequency is determined_ref、A_refWherein the oscillatable unit 4 is excited to perform resonant oscillation in air.

In order to determine information about the condition of the sensor 1 during ongoing operation, the oscillatable unit is assisted by an excitation signal U_AIs re-excited so that mechanical oscillation is performed in a fundamental oscillation mode and a reception signal U representing the oscillation_EIs received and evaluated for frequency f and amplitude a. At this time, the oscillatable unit 4 is not covered with the medium. These values f, A are then, for example, compared with their reference values f_ref、A_refComparing and determining the measured values f, A and the reference value f_ref、A_refThe deviation of (2).

For example, predeterminable limit values can be defined. If the deviation exceeds this limit value, then in the given case there is a problem or the sensor 1 needs to be repaired. Thus, the method of the present invention provides the advantage of predictive maintenance.

Reference numerals

1 vibration sensor

2 Medium

2a container

3 sensor unit

4 oscillatable unit

5 drive/receive unit

6 electronic unit

7 film

8a, 8b oscillating tines

9a, 9b paddle

U_AExcitation signal

U_EReceiving a signal

f frequency

f_refReference value of frequency

Amplitude of A

A_refReference value of amplitude.