Electronic vibration multisensor

Abstract

The present invention relates to an apparatus (1) and a method for determining and / or monitoring at least one process variable (P) of a medium (M). The apparatus includes a sensor unit (2) having a mechanically oscillating unit (4), at least one first piezoelectric element (11a), a unit (13) for determining and / or monitoring the temperature (T) of the medium (M), and an electronic unit (6). The apparatus (1) is designed to excite the mechanically oscillating unit (4) to oscillate mechanically by means of an excitation signal (A) and to receive the mechanical oscillation of the oscillating unit (4); and to convert the mechanical oscillation into a first received signal (E). A ), transmits a transmission signal (S) and receives a second reception signal (E) S ), wherein the electronic unit (6) is designed based on the first received signal (E A ) and / or the second received signal (E S The unit (13) for determining and / or monitoring temperature (T) according to the invention includes a first temperature sensor (15a) and a second temperature sensor (15b), the first temperature sensor (15a) and the second temperature sensor (15b) being arranged at a distance from each other, and the electronic unit (6) being designed to determine the temperature (T) of the medium (M) based on the first temperature received signal and / or the second temperature received signal received from the unit by the first temperature sensor (15a) and / or the second temperature sensor (15b).

Description

Technical Field

[0001] This invention relates to an apparatus for determining and / or monitoring at least one process variable of a medium, the apparatus comprising a sensor unit having a mechanically oscillating unit, at least one piezoelectric element, a unit for determining and / or monitoring the temperature of the medium, and an electronic unit. The invention further relates to a method for determining and / or monitoring at least one process variable of a medium. The medium is located in a container, such as a vessel or pipe. Background Technology

[0002] Electronic vibration sensors are commonly used in process and / or automation engineering. In the case of level measuring devices, the level measuring device has at least one mechanically oscillating unit, such as, for example, a vibrating fork, a single rod, or a diaphragm. In operation, this at least one mechanically oscillating unit is excited to generate mechanical oscillations by means of an actuator / receiver unit, typically in the form of an electromechanical transducer unit, for example, which may be a piezoelectric actuator or an electromagnetic actuator. The applicant manufactures various corresponding field devices and distributes them, for example, under the names LIQUIPHANT or SOLIPHANT. The basic measurement principle is known in principle from numerous publications. The actuator / receiver unit excites the mechanically oscillating unit to generate mechanical oscillations by means of an electrical excitation signal. Conversely, the actuator / receiver unit is able to receive the mechanical oscillations of the mechanically oscillating unit and convert them into an electrical received signal. Therefore, the actuator / receiver unit is a separate actuator unit and a separate receiver unit, or a combined actuator / receiver unit.

[0003] In many cases, the driver / receiver unit is part of an electrical resonant feedback circuit, which excites a mechanically oscillating element to generate mechanical oscillations. For example, to achieve resonant vibration, the resonant circuit condition must be met, according to which the amplification factor is ≥1, and all phases occurring in the resonant circuit result in multiples of 360°. To excite the signal and satisfy the resonant circuit condition, a defined phase shift must be ensured between the excitation signal and the received signal. Therefore, a predetermined phase shift value is typically set, i.e., the phase shift setpoint between the excitation and received signals. For this purpose, various solutions (including analog and digital methods) can be obtained from existing technologies, such as those described in documents DE102006034105A1, DE102007013557A1, DE102005015547A1, DE102009026685A1, DE102009028022A1, DE102010030982A1, or DE00102010030982A1.

[0004] Both the excitation and received signals are characterized by their frequency ω, amplitude A, and / or phase Φ. Therefore, changes in these variables are often used to determine the corresponding process variables. For example, the process variable could be the liquid level, a specified liquid level, or the density or viscosity of the medium and its flow rate. For instance, an electronically vibrating level switch for liquids can be used to distinguish between whether an oscillating cell is covered by liquid or oscillating freely. Alternatively, these two conditions—free condition and covered condition—can be distinguished based on different resonant frequencies, i.e., based on frequency shifts.

[0005] If the oscillating cells are completely covered by the medium, then density and / or viscosity can only be determined using such measuring equipment. Regarding the determination of density and / or viscosity, different possibilities are also known from the prior art, such as those described in documents DE10050299A1, DE102007043811A1, DE10057974A1, DE102006033819A1, DE102015102834A1, or DE102016112743A1.

[0006] Therefore, electronic vibration sensors can be used to measure several process variables and characterize the corresponding process. However, in many cases, further information about the process is needed for comprehensive process monitoring and / or control, especially further knowledge of physical and / or chemical process variables and / or process parameters. This can be achieved, for example, by integrating additional field devices into the corresponding process. The measurements provided by the various measuring devices can then be further processed in an appropriate manner in the upstream units of these devices.

[0007] However, the current situation is that, for example, different measuring devices have different measurement accuracies. Furthermore, drift and / or aging effects vary considerably in each case. Such effects can make the corresponding measurements or process monitoring and / or control more difficult or inaccurate. Moreover, during continuous operation, it can be difficult to determine the individual status of each field device in each case. Therefore, an electronic vibration multi-sensor has been disclosed from a previously unpublished German patent application with reference number 102018127526.9, by means of which both electronic vibration measurement principles and ultrasonic measurement principles can be used to determine and / or monitor one or more process variables. Summary of the Invention

[0008] Starting with the prior art cited, the present invention is based on the aim of further enhancing the functionality and measurement accuracy of such electronic vibration sensors.

[0009] This objective is achieved by the device according to the invention.

[0010] The objective is achieved, relative to the aforementioned device, by an apparatus for determining and / or monitoring at least one process variable of a medium, the apparatus comprising a sensor unit having a mechanically oscillating unit, at least one first piezoelectric element, and a unit for determining and monitoring the temperature of the medium, and an electronic unit. The apparatus is designed to excite the mechanically oscillating unit to perform mechanical oscillation by means of an excitation signal, receive the mechanical oscillation of the oscillating unit and convert it into a first received signal, transmit a transmission signal, and receive a second received signal. The electronic unit is designed to use the first and / or second received signals to determine at least one process variable. According to the invention, the unit for determining and / or monitoring temperature comprises a first temperature sensor and a second temperature sensor arranged at a distance from each other, wherein the electronic unit is configured to determine the temperature of the medium by using the first and / or second temperature received signals from the first and / or second temperature sensors received by the unit.

[0011] The mechanically oscillating unit can be, for example, a diaphragm, a single rod, an arrangement of at least two oscillating elements, or a tuning fork. For instance, at least one piezoelectric element can be arranged in the region of the oscillating unit. The at least one piezoelectric element serves as a driver / receiver unit to generate mechanical oscillations of the mechanically oscillating unit generated by means of an excitation signal. When the oscillating unit is covered by a medium, the mechanical oscillations are further affected by the properties of the medium, making it possible to generate conclusions about at least one process variable using a first received signal representing the oscillations of the oscillating unit.

[0012] Furthermore, the piezoelectric element is used to generate a transmitted signal that is received in the form of a second received signal. If the transmitted signal passes through the medium at least temporarily and in segments during its path, the transmitted signal is also affected by the physical and / or chemical properties of the medium, and therefore can be used to determine the process variables of the medium.

[0013] Therefore, within the scope of this invention, at least two measurement principles can be implemented in a single device. On one hand, the sensor unit performs mechanical oscillations; on the other hand, a transmission signal is emitted. In response to both the mechanical oscillations and the transmission signal, two received signals are received and can be evaluated, for example, relative to at least two distinct process variables. Advantageously, the two received signals can be evaluated independently of each other. In this way, according to the invention, the number of determinable process variables can be significantly increased, leading to greater functionality of the corresponding sensor or an expanded range of applications.

[0014] Furthermore, the device according to the invention includes a unit for determining and / or monitoring the temperature of a medium. This unit includes two temperature sensors arranged at a distance from each other, to which the same or different temperature signals can be applied. The temperature of the medium, for example as a third process variable, can then be determined using a first and / or second temperature reception signal received from the unit. Because the two temperature sensors are arranged at a distance from each other, the temperature can be determined very accurately. In particular, non-uniform temperature distribution in the sensor unit region can be taken into account due to the different thermal conductivity of different components of the sensor unit, the medium, and the container, as well as due to the different temperatures of the surrounding environment and the medium, and due to temperature variations in the medium or the surrounding environment.

[0015] Both the ambient temperature and the temperature of the medium have a significant impact on a wide range of other process variables of the medium. Therefore, by means of additional measurements and / or monitoring, especially of temperature at different locations, the measurement accuracy of multi-sensor systems can be significantly improved, and the functionality of the sensors can be significantly enhanced.

[0016] In one embodiment, the sensor unit includes at least one second piezoelectric element, wherein the first and second piezoelectric elements are configured to excite a mechanically oscillating unit by means of an excitation signal to generate mechanical oscillations, and to receive the mechanical oscillations of the oscillating unit and convert them into a first received signal, wherein the first piezoelectric element is configured to transmit a transmission signal, and wherein the second piezoelectric element is configured to receive the transmission signal in the form of a second received signal. However, more than two piezoelectric elements may also be present, and they may be arranged at different positions relative to the oscillating unit.

[0017] In another embodiment, the mechanically oscillating unit is a vibrating fork having a first oscillating element and a second oscillating element, wherein the first piezoelectric element is at least partially arranged in the first oscillating element, and the second piezoelectric element is at least partially arranged in the second oscillating element. For example, corresponding embodiments of the sensor unit have been described in documents DE102012100728A1 and DE102017130527A1. Both applications are incorporated herein by reference in their entirety within the framework of this invention. The possible embodiments of the sensor unit described in these documents are exemplary, possible structural embodiments of the sensor unit. For example, it is not absolutely necessary to arrange the piezoelectric elements only in the region of the oscillating element. Instead, the individual piezoelectric elements used can also be arranged in the region of the diaphragm, or in other oscillating elements not used for electronic vibration excitation but also applied to the diaphragm.

[0018] In another embodiment of the device, a first temperature sensor is arranged and / or configured to detect a first temperature in a first end region of the sensor unit facing the medium, wherein a second temperature sensor is arranged and / or configured to detect a second temperature in a second end region of the sensor unit facing away from the medium, particularly a second temperature in a region where at least one piezoelectric element is arranged.

[0019] Advantageously, by detecting the temperature in the portion of the sensor unit facing the medium and the portion facing away from the medium, the heat conduction in the sensor unit region can be determined. As already mentioned, the process variables that can be determined by means of multiple sensors depend significantly on the temperature of the medium and also on the temperature of the sensor unit. For highly accurate and reliable measurements, accurate spatially resolved information about the temperature profile distribution exposed to the sensor unit is crucial.

[0020] For this purpose, at least one of the two temperature sensors can be arranged, for example, on or within the sensor unit. In the case of a sensor unit in the form of a vibrating fork, for example, it is conceivable that at least one temperature sensor is positioned on or within one of the oscillating elements. For example, one temperature sensor can be arranged in the portion of one of the oscillating elements facing the medium, while the other temperature sensor can be arranged in the end region of one of the oscillating elements facing away from the medium.

[0021] A further advantage is that the unit for determining and / or monitoring temperature includes a rod-shaped housing element arranged such that its longitudinal axis is parallel to the longitudinal axis of the oscillating unit, wherein a first temperature sensor is disposed in a first end region of the housing element facing the medium, and wherein a second temperature sensor is disposed in a second end region of the housing element facing away from the medium. Thus, the temperature sensors are positioned separately from the oscillating unit. Such an embodiment makes it easier to ensure a symmetrical configuration of the two oscillating elements, for example, in the case of a sensor unit in the form of a vibrating fork.

[0022] In another embodiment of the device, the unit for determining and / or monitoring temperature includes a temperature sensor in the form of a resistive element or a thermocouple.

[0023] Fundamentally, it is advantageous that the unit used to determine and / or monitor temperature, particularly two temperature sensors, is arranged such that it has good thermal coupling with the medium and / or the sensor unit. Thermal coupling with the medium is particularly necessary to eliminate the influence of temperature on specific process variables. It is advantageous if each of the two temperature sensors is at least temporarily and / or partially in contact with the medium. In principle, it is preferred that they be spatially close to the sensor unit. It is also advantageous that the sensor unit is configured such that its heat capacity is as low as possible. In this case, the response time for determining the temperature is short in the event of changes in the medium temperature.

[0024] In another preferred embodiment of the device, the sensor unit includes a unit for determining and / or monitoring pressure, and / or a unit for determining and / or monitoring the conductivity and / or capacitance of the medium. By implementing additional measurement principles in a single sensor, the application range and measurement accuracy of the sensor can be further broadened and improved.

[0025] The objective of this invention is further achieved through a method for determining and / or monitoring at least one process variable of a medium, wherein...

[0026] - The sensor unit is excited to oscillate mechanically by means of an excitation signal.

[0027] - Mechanical vibrations are received by the sensor unit and converted into a first received signal.

[0028] - The sensor unit transmits a transmission signal and receives a second reception signal.

[0029] - Use the first received signal and / or the second received signal to determine at least one process variable, and

[0030] - A first and / or second value of at least one temperature is determined by using a first temperature receiving signal and a second temperature receiving signal received from a first temperature sensor and / or a second temperature sensor.

[0031] The method is particularly suitable for devices according to one of the previously described embodiments. On one hand, it is conceivable to simultaneously supply excitation and transmission signals to the sensor unit, wherein the excitation and transmission signals are superimposed on each other. However, alternatively, it is also possible to supply excitation and transmission signals to the sensor unit alternately.

[0032] For example, the excitation signal is an electrical signal with at least one specifyable frequency, especially a sinusoidal or rectangular wave signal. The mechanically oscillating element is preferably excited at least temporarily to produce resonant oscillations. The mechanical oscillation is influenced by the medium surrounding the oscillating element, and thus, based on the received signal representing the oscillation, conclusions can be drawn about various properties of the medium.

[0033] The transmitted signal is preferably an ultrasonic signal, especially a pulsed ultrasonic signal, particularly at least one ultrasonic pulse. Therefore, within the scope of this invention, an ultrasonic-based measurement is performed as the second measurement method used. The separately transmitted signals at least partially pass through the medium and are affected by the medium in terms of their properties. Therefore, conclusions regarding different media can also be drawn using the separately received second received signals.

[0034] To determine the temperature, the same or different temperature signals are applied to two temperature sensors. The application of at least one temperature signal can also be performed simultaneously or alternately with the application of an excitation signal and / or a transmission signal to the sensor unit.

[0035] Using the method according to the invention, multiple different process variables can be determined by means of different measurement principles. Furthermore, the effect of temperature can be considered in each case. Advantageously, different process variables can be measured independently of each other, allowing for comprehensive analysis of the corresponding process using a single measuring device. Moreover, by using the same sensor unit for several measurement methods, the accuracy of the measurements can be significantly improved. Furthermore, various measurement principles can be used to perform monitoring of the equipment status. In this regard, many embodiments of the method according to the invention are possible, and some preferred variations of these embodiments are described below.

[0036] In one embodiment of the method, at least two distinct process variables are determined, wherein a first received signal is used to determine the first process variable, and wherein a second received signal is used to determine the second process variable.

[0037] In another embodiment, at least one process variable is a predetermined liquid level, density, viscosity, sound velocity, or a variable derived from at least one of these variables. Particularly preferably, a first received signal is thus used to measure the density and / or viscosity of the medium, and a second received signal is thus used to measure the sound velocity within the medium. However, it is implicitly understood that, in addition to the process variables explicitly mentioned herein, other process variables and / or process parameters accessible through the two measurements can also be measured and used to characterize the corresponding process.

[0038] In one embodiment of the method, the effect of the medium temperature on the first and / or second received signals or on the first and / or second process variables is compensated. Various variations are conceivable in this case, all of which fall within the scope of the invention. For example, the effect of temperature on one of the two received signals can be compensated using one of the two temperature received signals, while the effect of temperature on the corresponding other received signal can be compensated using the other temperature received signal. Alternatively, the effect of temperature on both received signals can be compensated using temperature received signals, or the effect of temperature on each of the two received signals can be compensated using both temperature received signals.

[0039] In one embodiment of the method, a first temperature value is detected by means of a first temperature sensor in the end region of the sensor unit facing the medium, and / or a second temperature value is detected by means of a second temperature sensor in the end region of the sensor unit facing away from the medium, and / or one of these temperatures is used in each case to determine one of the process variables. For example, particularly in the case of an oscillating unit in the form of a vibrating fork, the temperature in the end region of the sensor unit facing the medium has a considerable influence on the values ​​of density and viscosity measured by means of the sensor. These two process variables vary not only with respect to the medium but also with respect to temperature. Therefore, accurate knowledge of the temperature in the sensor unit region (which is sensitive to density and viscosity) ensures a significant improvement in the accuracy of measurements related to these process variables. However, in many cases, especially due to heat conduction from the process to the environment or vice versa, this temperature in the end region of the sensor unit facing the medium differs from the temperature in the end region of the sensor unit facing away from the medium. If at least one piezoelectric element is arranged, for example, in the end region facing away from the medium, the velocity of sound in that end region is also measured. Because the velocity of sound also depends on temperature, it is useful to determine the temperature in the end region of the sensor unit facing away from the medium in order to compensate for the effect of temperature on the velocity of sound. Therefore, in the cited example, two temperature sensors spaced apart from each other significantly improve the achievable measurement accuracy associated with the determined process variable.

[0040] In another embodiment of the method, based on a first and / or second temperature received signal, compensation is made for the effect of temperature on at least one physical and / or chemical property of at least one component of the sensor unit, the at least one process variable depending on said property. According to the previously mentioned example, density and / or viscosity are determined by using the mechanical oscillation of a unit capable of mechanical oscillation. For this purpose, for example, the oscillating unit is excited to resonate. In this case, the resonant frequency depends on the elastic modulus of the oscillating unit, which in turn also depends on the temperature. Therefore, in this case, accurate knowledge of the temperature is also of significant value in improving measurement accuracy. In the case of an oscillating unit, the resonant frequency is, for example, decisively influenced by the portion of the sensor unit facing away from the medium (the root region of the oscillating element).

[0041] Another embodiment provides that the process through which the medium passes is described by using the temperature of the medium. For example, it is possible to detect and / or monitor the mixing operation of different media at different temperatures by using separately determined temperatures. In this case, the temperature of the mixture may fluctuate briefly for a short period of time, which can negatively affect the measurement of individual process variables. It is also possible to identify whether the corresponding sensor is operating outside the permissible operating range for the temperature. Another possible description is to identify the cleaning process performed for each sensor. During the cleaning process, different cleaning cycles can be detected and / or monitored. Typically, the sensor unit is treated at a high temperature, such as with hot water steam, after a cold water rinse, which is accompanied by large temperature variations determined by means of the unit used to determine and / or monitor the temperature. It is also conceivable to perform calibration on the sensor unit during each process step of the cleaning process (e.g., during a cold rinse process).

[0042] In one embodiment of the method, the values ​​of the first and / or second temperatures are determined by using the electromechanical efficiency or capacitance of at least one piezoelectric element of the sensor unit. For example, temperature measurement using the electromechanical efficiency of a piezoelectric element is described in detail in document DE102016120326A1, which is incorporated herein by reference in its entirety within the scope of this invention. Temperature measurement using the capacitance of a piezoelectric element is also known from the prior art.

[0043] Therefore, it is advantageous that, for the first and / or second temperature, the values ​​of the first and / or second temperature determined by using the first and / or second temperature receiving signals are compared with the values ​​of the first and / or second temperature determined by using electromechanical efficiency or capacitance, and wherein, particularly when the deviation between the value determined by means of the first and / or second temperature receiving signals and the value determined by using electromechanical efficiency or capacitance exceeds a specified limit value, a description is made regarding at least one piezoelectric element or the first and / or second temperature sensor. Thus, the sensor unit can also be diagnosed using the determined temperature values.

[0044] The diagnosis can include, for example, a description of the unit used to determine and / or monitor temperature, particularly via the first and / or second temperature sensors, or a description of the state of the first and / or second piezoelectric elements. Advantageously, it is possible to perform a plausibility check on the measurement principles used in individual applications, particularly on the two received signals, and on the temperature received signal received by the unit used to determine and / or monitor the temperature.

[0045] In another embodiment of the method according to the invention, heat dissipation, particularly heat dissipation in the sensor unit region, is determined by using the difference between the values ​​of the first and second temperatures determined by the first and second temperature receiving signals, wherein, in particular, a warning is output if the difference exceeds a specified limit value.

[0046] Therefore, it is also possible to compare two temperature sensors with each other. Furthermore, it is possible to compare other measurement principles relative to each other based on the spatially resolvable temperature profile distribution predominant in the sensor unit region. In addition, a maximum permissible difference between the output ambient temperature and the medium temperature can be envisioned, ensuring reliable operation of the corresponding device, and issuing a warning if the difference exceeds this limit.

[0047] Furthermore, it is advantageous to determine a reference value for density by using the speed of sound, wherein a density value determined based on a first received signal is compared with a reference value. Preferably, the concentration of the reference substance dissolved in the reference medium in a specified container is determined based on the speed of sound determined based on a second received signal. A reference value for the density of the reference medium can then be determined based on the concentration. Additionally, a measured value for density can be determined based on the first received signal. The two density values ​​can then be compared with each other. Adjustments can be made based on the density value determined by the first received signal, and particularly based on the reference value for density determined by the second received signal. In this way, the adverse effects of the geometry of the respective containers on the determination of the electronic vibrations of density can be compensated for.

[0048] In yet another particularly preferred embodiment, first and second received signals and / or first and second process variables are used to determine a first concentration of a first substance contained in the medium and a second concentration of a second substance contained in the medium. According to the prior art, analysis of such a medium with respect to two different substances typically requires two separate measuring devices for the different analytes. According to the present invention, in contrast, the description of two different components in the medium can be reliably performed using a single device.

[0049] The preferred use of the method involves monitoring the fermentation process. During fermentation, sugar is converted into ethanol. In order to ensure qualitative monitoring, it is necessary to determine the concentrations of both sugar and ethanol. This is possible within the framework of the present invention.

[0050] Finally, in an advantageous embodiment of the method, first and second received signals and / or first and second process variables are used to determine whether deposits have formed on the sensor unit and / or whether drift and / or aging of the sensor unit are present. Depending on the deposits on the probe unit, drift, or aging in the sensor unit region, the two received signals are typically different in each case. Therefore, for example, the presence of deposits, drift, or aging can be determined using a temporal consideration of the two received signals and / or process variables.

[0051] Advantageously, the first and second received signals, the first and second process variables, and / or the time profile distributions of the first and second received signals and / or the time profile distributions of the first and second process variables are compared with each other. The presence of deposits, drift, or aging of the sensor unit can then be inferred from the comparison. Because at least two received signals or process variables are accessible, a high degree of accuracy can be achieved in each case relative to any description made regarding deposits, drift, or aging. Therefore, according to the invention, by performing two different measurements using a single sensor unit, the presence of deposits, or the drift or aging of the sensor unit, can be reliably detected.

[0052] In another particularly preferred embodiment, the effects of deposits, drift, and / or aging of the sensor unit on the first and / or second received signals are reduced or compensated when determining and / or monitoring at least one process variable, or when determining variables derived from at least one process variable and / or from at least one received signal. Therefore, when determining and / or monitoring individual process variables, the effects of deposits, drift, and / or aging of the sensor unit can be taken into account, making it possible to determine individual process variables regardless of the presence of deposits, drift, or aging. To mitigate or compensate for these effects, for example, suitable, particularly process-dependent algorithms can be stored, by means of which values ​​for the corresponding process variables can be determined that are not tampered with by deposits, drift, and / or aging of the sensor unit. Therefore, improved measurement accuracy can be achieved, and thus the possibility of predictive maintenance can be provided.

[0053] It should be noted that the embodiments described in conjunction with the device according to the invention can also be applied to the method according to the invention with the necessary modifications, and vice versa. Attached Figure Description

[0054] The invention will be explained in more detail with reference to the following figures, in which:

[0055] Figure 1 A schematic diagram of an electronic vibration sensor according to the prior art is shown.

[0056] Figure 2 illustrates several possible embodiments of the sensor unit, which are known from the prior art and suitable for performing the method according to the invention.

[0057] Figure 3 A possible embodiment of a device according to the invention is shown, which has a unit for determining the temperature of a medium.

[0058] In the figure, the same elements have the same reference numerals. Detailed Implementation

[0059] Figure 1 An electronic vibration sensor 1 is shown, which has a sensor unit 2. This sensor has a mechanically oscillating unit 4 in the form of a vibrating fork, the mechanically oscillating unit 4 being partially immersed in a medium M located in a container 3. An excitation / receiving unit 5 excites the oscillating unit 4 to perform mechanical oscillation, and the oscillating unit 4 can be excited, for example, by means of a piezoelectric stacked actuator or a dual piezoelectric actuator. Other electronic vibration sensors, for example, have an electromagnetic actuator / receiver unit 5. A single actuator / receiver unit 5 can be used for both exciting and detecting mechanical oscillations. However, it is also conceivable to implement both the actuator unit and the receiver unit. Furthermore, Figure 1Electronic unit 6 is described, by means of which signal acquisition, evaluation and / or feeding are performed.

[0060] Figure 2 illustrates, by way of example, various sensor units 2 suitable for implementing the method according to the invention. Figure 2a The mechanically oscillating unit 4 shown includes two oscillating elements 9a and 9b, which are mounted on a base 8 and are therefore also referred to as forks. Optionally, blades (not shown here) may be formed on the end sides of the two oscillating elements 9a and 9b respectively. In each of the two oscillating elements 9a and 9b, a first cavity 10a and a second cavity 10b, particularly a pocket-shaped cavity, are introduced, in which at least one piezoelectric element 11a and 11b of the driver / receiver unit 5 is arranged respectively. Preferably, the piezoelectric elements 11a and 11b are embedded in the first cavity 10a and the second cavity 10b. The first cavity 10a and the second cavity 10b allow the two piezoelectric elements 11a and 11b to be completely or partially located in the region of the two oscillating elements 9a and 9b. Such arrangements and similar arrangements are extensively described in DE102012100728A1.

[0061] exist Figure 2b Another possible exemplary embodiment of the sensor unit 2 is depicted. The mechanically oscillating unit 4 has two oscillating elements 9a and 9b, which are aligned parallel to each other and configured in a rod-like manner. These two oscillating elements 9a and 9b are mounted on the disk-shaped element 12 and can be independently excited to oscillate mechanically. The oscillations of these two oscillating elements can also be independently received and evaluated. The two oscillating elements 9a and 9b each have a first cavity 10a and a second cavity 10b, respectively, and at least one piezoelectric element 11a and 11b are respectively arranged in the regions facing the disk-shaped element 12 in the first cavity 10a and the second cavity 10b. Regarding the... Figure 2b The embodiments are further referenced to the previously unpublished German patent application with reference number DE102017130527A1.

[0062] like Figure 2b As schematically shown, according to the present invention, on the one hand, an excitation signal A is provided to the sensor unit 2, causing the oscillating unit 4 to be excited to oscillate mechanically. The oscillation is generated by means of two piezoelectric elements 11a and 11b. It is conceivable that the same excitation signal A is applied to both piezoelectric elements, and it is conceivable that a first excitation signal A1 is applied to the first piezoelectric element 11a, and a second excitation signal A2 is applied to the second piezoelectric element 11b. It is also conceivable that a first received signal E is received based on mechanical oscillation. A Alternatively, each oscillating element 9a, 9b may receive a separate received signal E. A1 or EA2 .

[0063] Furthermore, the transmission signal S is emitted from the first piezoelectric element 11a, and received by the second piezoelectric element 11b as a second received signal E. S The transmitted signal S is in the form of a piezoelectric element. Because the two piezoelectric elements 11a and 11b are arranged at least in the regions of the oscillating elements 9a and 9b, the transmitted signal S passes through the medium M, provided that the sensor unit 2 is in contact with the medium M and is therefore affected by the properties of the medium M. The transmitted signal S is preferably an ultrasonic signal, especially a pulsed ultrasonic signal, and particularly at least one ultrasonic pulse. However, it is also conceivable that the transmitted signal S is emitted by the first piezoelectric element 11a in the region of the first oscillating element 9a and will be reflected at the second oscillating element 9b. In this case, the second received signal E... S The signal is received by the first piezoelectric element 11a. In this case, the transmitted signal S passes through the medium M twice, which causes the transmission time τ of the transmitted signal S to double.

[0064] In addition to the two embodiments shown in the device according to the invention, many other variations are contemplated, which also fall within the scope of the invention. For example, for the device according to... Figure 2a and Figure 2b In one embodiment, only one piezoelectric element 11a, 11b can be used, and this single piezoelectric element 11a, 11b is arranged in at least one of the two oscillating elements 9a, 9b. In this case, the piezoelectric element 9a is used to generate an excitation signal and a transmission signal S, and to receive a first received signal E1 and a second received signal E2. In this case, the transmission signal is reflected at the second oscillating element 9b in the absence of the piezoelectric element 11b.

[0065] exist Figure 2c Another exemplary possibility is depicted. Here, a third piezoelectric element 11c is disposed in the region of the diaphragm. The third piezoelectric element 11c is used to generate an excitation signal A and to receive a first received signal E1; the first piezoelectric element 11a and the second piezoelectric element 11b are used to generate a transmission signal S or to receive a second received signal E2. Alternatively, for example, the excitation signal A and the transmission signal S can be generated using the first piezoelectric element 11a and / or the second piezoelectric element 11b, and the second received signal E2 can be received, wherein the third piezoelectric element 11c is used to receive the first received signal E1. The transmission signal S can also be generated using the first piezoelectric element 11a and / or the second piezoelectric element 11b, and the excitation signal A can be generated using the third piezoelectric element 11c, and the first received signal E1 and / or the first received signal E2 can be received using the first piezoelectric element 11a and / or the second piezoelectric element 11b. Figure 2cIn other embodiments, the first piezoelectric element 11a or the second piezoelectric element 11b may be omitted.

[0066] Another possible embodiment of the device is Figure 2d The theme. From Figure 2b The embodiment begins with a device comprising a third oscillating element 9c and a fourth oscillating element 9d. However, the fourth oscillating element 9d is not used to generate oscillations. More specifically, the third piezoelectric element 11c and the fourth piezoelectric element 11d are respectively arranged in additional elements. In this case, electronic vibration measurements are performed by means of the first two piezoelectric elements 11a and 11b, and ultrasonic measurements are performed by means of the other two piezoelectric elements 11c and 11d. Here, depending on the measurement principle, piezoelectric elements such as 11b and 11d can also be omitted. However, for reasons of symmetry, it is always advantageous to use two additional oscillating elements.

[0067] First received signal E A Second received signal E S These measurements are derived from different measurement methods and can be evaluated independently of each other with respect to at least one process variable P. In this regard, reference is made in its entirety to the previously unpublished German patent application No. 102018127526.9, which is within the scope of this invention.

[0068] Furthermore, according to the present invention, temperature T can be determined very accurately and reliably, and the influence of temperature T on specific determined process variables can be compensated for. For this purpose, such as... Figure 3 As shown, the device according to the invention has a unit for determining and / or monitoring temperature. In the example shown, the sensor unit 2 is designed to be similar to... Figure 2a Variants in [the original text].

[0069] Unit 13 is arranged between two oscillating elements 9a and 9b for determining and / or monitoring the temperature T of the medium. Unit 13 includes a rod-shaped housing element 14 in which a first temperature sensor 15a and a second temperature sensor 15b, spaced apart from each other, are arranged. These temperature sensors can be designed, for example, in the form of resistive elements or thermocouples. The first temperature sensor 15a is configured to determine a first temperature T1 in the end region B1 of the sensor unit 2 facing the medium M, while the second temperature sensor 15b is configured to determine a second temperature T2 in the end region B2 of the sensor unit 2 facing away from the medium M. Since the temperature of the medium is different from the ambient temperature, the first temperature T1 and the second temperature T2 are typically different from each other. Therefore, understanding the spatially resolved temperature profile distribution of the sensor unit 2 is crucial for accurately determining all available process variables. Because the temperature at different locations is determined, the achievable measurement accuracy of the electronic vibration sensor 1 can be significantly improved, and further diagnostic functions can be provided.

[0070] Alternative variations of the device according to the invention, not shown separately herein, can, for example, arrange at least one temperature sensor 15a, 15b in the region of the oscillating elements 9a, 9b or in the region of the base 8. It is also conceivable to use more than two temperature sensors positioned at a distance from each other.

[0071] List of reference numerals

[0072] 1. Electronic vibration sensor

[0073] 2 Sensor Unit

[0074] 3 containers

[0075] 4. Units capable of oscillation

[0076] 5 Driver / Receiver Units

[0077] 6 electronic units

[0078] 8 bases

[0079] 9a First oscillating element

[0080] 9b Second oscillating element

[0081] 10a First cavity

[0082] 10b Second cavity

[0083] 11a First piezoelectric element

[0084] 11b Second piezoelectric element

[0085] 12 disk-shaped elements

[0086] 13 Units for determining and / or monitoring temperature

[0087] 14 Rod-shaped housing elements

[0088] 15a First Temperature Sensor

[0089] 15b Second Temperature Sensor

[0090] M medium

[0091] P process variable

[0092] T1 First Temperature

[0093] T2 Second Temperature

[0094] A Excitation Signal

[0095] S Transmit signal

[0096] E A First received signal

[0097] E S Second received signal

[0098] E T Third received signal

[0099] ΔΦ is a specifyable phase shift.

Claims

1. An apparatus for determining and / or monitoring at least one process variable of a medium (M), comprising: Sensor unit (2), said sensor unit (2) having: Units capable of mechanical oscillation (4). At least one first piezoelectric element (11a), and Unit (13) for determining and / or monitoring the temperature (T) of the medium (M). And has Electronic unit (6) The device is designed to be: The mechanically oscillating unit (4) is excited by an excitation signal (A) to generate mechanical oscillation. Receives the mechanical oscillation of the oscillating unit (4) and converts the mechanical oscillation into a first received signal (E). A ), Transmit a transmission signal (S) and receive a second reception signal (E). S ), as well as The electronic unit (6) is designed to use the first received signal (E) A ) and / or the second received signal (E S To determine the at least one process variable, Its features The unit (13) for determining and / or monitoring the temperature (T) includes a first temperature sensor (15a) and a second temperature sensor (15b), the first temperature sensor (15a) and the second temperature sensor (15b) being arranged at a distance from each other. The electronic unit (6) is designed to determine the temperature (T) of the medium (M) by using a first temperature receiving signal and / or a second temperature receiving signal from the first temperature sensor (15a) and / or the second temperature sensor (15b) received by the unit (13) for determining and / or monitoring the temperature (T). The first temperature sensor (15a) is arranged and / or configured to detect a first temperature (T1) in a first end region (B1) of the sensor unit (2) facing the medium (M), and The second temperature sensor (15b) is arranged and / or configured to detect a second temperature (T2) in a second end region (B2) of the sensor unit (2) opposite to the medium (M).

2. The device according to claim 1, in, The sensor unit (2) includes at least a first piezoelectric element (11a) and a second piezoelectric element (11b). The first piezoelectric element (11a) and the second piezoelectric element (11b) are designed to excite the mechanically oscillating unit (4) by means of an excitation signal (A) to generate mechanical oscillation; and to receive the mechanical oscillation of the oscillating unit (4) and convert the mechanical oscillation into a first receiving signal (E). A ), The first piezoelectric element (11a) is designed to transmit a signal (S). The second piezoelectric element (11b) is designed to receive a second received signal (E). S The transmitted signal (S) in the form of ) and The mechanically oscillating unit (4) is a vibrating fork having a first oscillating element (9a) and a second oscillating element (9b), wherein the first piezoelectric element (11a) is at least partially arranged in the first oscillating element (9a), and the second piezoelectric element (11b) is at least partially arranged in the second oscillating element (9b).

3. The device according to claim 1 or 2, in, The second temperature sensor (15b) is arranged and / or configured to detect a second temperature in an area where at least one piezoelectric element is arranged.

4. The device according to claim 1 or 2, in, The unit (13) for determining and / or monitoring temperature (T) includes a rod-shaped housing element (14) arranged such that the longitudinal axis of the housing element (14) is parallel to the longitudinal axis of the oscillating unit (4), and The first temperature sensor (15a) is arranged in the first end region (B1) of the housing element (14) facing the medium (M), and the second temperature sensor (15b) is arranged in the second end region (B2) of the housing element (14) facing away from the medium (M).

5. The device according to claim 2, in, The electronic unit (6) is designed to determine at least two distinct process variables (P1, P2), wherein the first received signal (E) is used. A The first process variable (P1) is determined using the second received signal (E). S To determine the second process variable (P2). Wherein, the at least one process variable is a variable that can be specified, such as liquid level, density, viscosity, sound velocity, or a variable derived from at least one of these variables, and The electronic unit (6) is designed to compensate for the temperature (T) of the medium (M) on the first received signal (E). A ) and / or the second received signal (E S The effect of ) on the first process variable (P1) and / or the second process variable (P2).

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