Vibration bridge for vibrating wire sensor and vibrating wire sensor

Abstract

The utility model relates to a vibration bridge for a vibrating wire sensor, comprising clamping points which lie opposite one another for connecting the vibration bridge to the vibrating wire sensor, and a plurality of vibration parts which are arranged between the clamping points and which are mechanically connected to a fastening point and can be placed under tension by means of the fastening point, one of the vibration parts does not have a vibration exciter or a vibration probe and the other vibration part is provided with a vibration exciter.

Description

Technical Field

[0001] The utility model relates to a vibration bridge (Schwingbrücke) used for a vibrating string sensor (Schwingsaitensensor) and a vibrating string sensor. Background Art

[0002] Vibrating wire sensors are known and are used on a wide basis for a variety of measurement technology applications. According to the basic principle, a vibrating wire sensor has a mechanism in which a vibrating wire is stretched, wherein a stress in the vibrating wire is generated by elastic deformation of the mechanism.

[0003] The mechanism can then be arranged as specified at two measuring points on any type of component or machine element and its deformation is thus reduced due to the displacement of the measuring points relative to one another. This deformation displacement causes an elastic deformation of the mechanism of the vibrating wire sensor, which in turn causes a changing stress in the vibrating wire. With this changing stress, the resonant frequency of the vibrating wire, which is set into vibration by the excitation component during operation, changes, which in turn can be detected by the evaluation component. Thus, a certain resonant frequency of the vibrating wire corresponds to a certain displacement of the measuring points.

[0004] It is known to the person skilled in the art that, due to the high Q factor or high quality of the vibrating wire, a vibrating wire sensor can be used for precise displacement measurements in the micrometer or even nanometer range. It is also known that by determining the force acting on the mechanism, a force measurement is also possible, since a certain force is required for a certain elastic deformation of the mechanism. The Q factor or quality is a measure of the damping or energy loss of a system that can vibrate. A high Q factor means that the system (here the vibrating wire) is weakly damped and thus has a high amplitude in the resonance range, so that the resonance range can be clearly defined.

[0005] Vibrating wire sensors are correspondingly more precise than strain gauges, for example, and have a higher resolution and less creep behavior than strain gauges. However, vibrating wire sensors are relatively large and consist of many components; in addition, they consume relatively high electrical power during operation. In particular, vibrating wire sensors based on magnetic excitation of a vibrating wire have relatively energy-intensive, complex and large components for generating the magnetic field required for this purpose.

[0006] Therefore, a particular focus is placed on vibrating wire sensors with a metallic vibrating bridge, which, although strictly speaking, may not have a (more or less) flexible vibrating wire but rather a spring-like elastic vibrating part with a larger spring constant, currently belong to the category of vibrating wire sensors due to the basic operating principle of resonant excitation.

[0007] For example, instead of a vibrating wire clamped at both ends, the vibrating bridge has one or more vibrating beams clamped at the ends and arranged side by side, which vibrate in antiphase, so that during operation the center of gravity of the vibrating bridge itself advantageously hardly vibrates, which in turn leads to less electrical power consumption.

[0008] In addition to other excitation methods for vibrating beams, piezoelectric actuators arranged thereon are also known. However, it has been shown that by introducing piezoelectric ceramics on the vibrating beam, interference factors are introduced into the properties of the vibrating bridge, which, among other disadvantages, lead to inaccurate measured values ​​(for the displacement / force) and in particular to a drift of the measured values ​​over time, so that the specific advantages of vibrating wire sensors are significantly reduced or lost. The reasons for this can be seen in the use of components and mounting materials on the vibrating beam, since they are subject to changes in mass due to water absorption or gas evolution, to changes in elasticity due to temperature or aging, which change the resonance properties of the vibrating beam and can ultimately also lead to undesirable hardening of the vibrating beam that affects the resonance frequency.

[0009] CA 2619996 now discloses a vibration bridge for a vibrating wire sensor with three vibrating beams arranged next to each other, which are excited by a piezoelectric actuator, wherein a further piezoelectric actuator receives (abnehmen, sometimes referred to as picking up) the current frequency of the vibrating beam. All piezoelectric elements are arranged outside the vibrating beams in the vicinity of the clamping point of the vibration bridge, thereby overcoming the above-mentioned disadvantages, so that accurate measured values ​​can be expected. However, this arrangement leads to other disadvantages, which significantly deteriorate the measurement or measurement accuracy that could be accurate per se in the case of a vibrating wire sensor.

[0010] One disadvantage is that the two piezoelectric elements are arranged directly next to each other as vibration exciters and vibration detectors, so that an additional piezoelectric element must be provided as a second vibration detector in order to be able to form a differential signal of the two vibration detectors, which has twice the strength of the signal of only one vibration detector and is therefore suitable for further processing by evaluation electronics and produces small errors.

[0011] According to the applicant's knowledge, other disadvantages are caused, for example, by the fact that in the known arrangement of the piezoelectric element, strong harmonics can be generated in the vibration beam and kinetic energy flows directly from the excitation element to the detection element or into the clamping point of the vibration bridge. Other reasons for the disadvantageous properties of the known arrangement are not yet clear.

[0012] This means that, despite the inherently feasible arrangement of the piezoelectric elements in this way, the measuring accuracy of the vibrating bridge disclosed in CA 2619996 does not reach the quality that is possible in a vibrating wire sensor, even if an unsatisfactory arrangement of the piezoelectric elements on the vibrating beam is avoided. Utility Model Content

[0013] Accordingly, it is an object of the present invention to provide a vibrating bridge or a vibrating wire sensor which achieves a high and constant measuring accuracy.

[0014] This object is achieved by a vibrating bridge described below and by a vibrating wire sensor described below.

[0015] In the present invention, the vibration bridge has clamping locations located opposite one another for connecting the vibration bridge to the vibrating wire sensor and has a plurality of vibration parts arranged between the clamping locations and mechanically connected to the clamping locations, wherein one of the plurality of vibration parts is subjected to tension or compression during operation via the clamping locations. Only one of the vibration parts subjected to tension or compression is designed as a resonant vibration part and has no vibration exciter or vibration detector, and another vibration part is provided with a vibration exciter.

[0016] The vibrating wire sensor has the above-described vibration bridge, has an excitation component for the vibration exciter, which is provided with an input for the frequency signal of the vibration detector, and is designed to output a frequency corresponding to the frequency signal as an excitation frequency to the vibration exciter.

[0017] Alternatively, the vibrating wire sensor has the above-described vibrating bridge. The vibrating wire sensor has an excitation arrangement for the vibration exciting element, which is designed to detect a current detection signal generated by the vibration exciting element in a phase without excitation of the vibration exciting element.

[0018] In a preferred embodiment, the excitation component is further configured to excite the vibration excitation element in an excitation phase following a non-excitation phase of the vibration excitation element by means of the excitation signal at a frequency that corresponds to a detection signal generated by the vibration excitation element in a preceding non-excitation phase.

[0019] Alternatively again, the vibrating wire sensor has the above-described vibrating bridge. The vibrating bridge also has a detection oscillation part with a resonant frequency different from the resonant frequency of the resonant oscillation part and with a resonance curve that runs flatter than the resonance curve of the resonant oscillation part, and the vibrating bridge is designed so that the detection oscillation part itself vibrates with an amplitude higher than the detection amplitude of the excitation component when the resonant oscillation part vibrates with an amplitude higher than the transmission amplitude during operation, and the vibrating wire sensor is provided with an excitation component, which is designed to generate an excitation signal for a vibration exciter and to process a currently detected detection signal of a vibration detector arranged on the detection oscillation part, wherein the detection signal is not used to determine the frequency and amplitude of the detection oscillation part below the detection amplitude, wherein the resonance curves of the resonant oscillation part and the detection oscillation part overlap in a range above the higher of the detection amplitude and the transmission amplitude.

[0020] In a preferred embodiment, the excitation component is further configured to not use the currently detected detection signal to determine the frequency and amplitude of the detection vibration part when the frequency of the detection vibration part is not in a predetermined permissible frequency interval within the frequency range of the resonant vibration part that is higher than the transmission amplitude.

[0021] Since one of the vibration parts does not have an excitation element or a vibration detector, the vibration part can be used as a resonant vibration part, whose resonance characteristics are not affected, so that the vibration part has a high Q factor and thus allows optimal measurement accuracy in principle. By arranging the vibration excitation element on another vibration part that acts as an excitation vibration part, although it can be predicted that the vibration properties of the excitation vibration part will be negatively affected, unexpectedly, there is no negative impact on the excitation and resonance properties of the resonant vibration part itself. Equally unexpectedly, this also applies to the arrangement of the vibration detection element on the detection vibration part. As a result, the highest measurement accuracy that can be achieved by a vibrating wire sensor in principle can be achieved through the vibration bridge according to the utility model, wherein the drift of the measured values ​​is also eliminated.

[0022] In addition to the stated object, the excitation arrangement according to the invention makes it possible to shorten the time interval between individual measurements, since essentially a repeated frequency search for the corresponding resonance frequency is dispensed with.

[0023] In a preferred embodiment, the vibration exciter can be operated as a vibration detector.

[0024] In a preferred embodiment, three vibration parts are provided which are arranged parallel to one another in a plane, wherein one of the outer vibration parts is provided with a vibration exciter and another is provided with a vibration detector, and at least the middle vibration part can be placed under tension and has no vibration exciter and vibration detector, wherein preferably the outer vibration part can also be placed under tension.

[0025] In a preferred embodiment, the mass of the outer vibrating part with the vibration exciter and the vibration receiver is substantially the same as the mass of the middle vibrating part, and the vibration bridge is designed in such a way that the center of gravity of the vibration bridge remains substantially stationary when the outer vibrating part vibrates in an antiphase relationship with the middle vibrating part.

[0026] In a preferred embodiment, the vibration part provided with the vibration exciter is designed as a vibration tongue.

[0027] In a preferred embodiment, a further vibration part is provided which is designed as a vibration tongue and has a vibration detector.

[0028] In a preferred embodiment, the vibration portion configured as a vibration tongue is disposed opposite to the counter-vibration tongue.

[0029] In a preferred embodiment, the engaging tongue is provided with a counterweight which has such a mass that, during operation of the vibration bridge, the engaging tongue vibrates essentially in phase with the tongue associated therewith.

[0030] In a preferred embodiment, at least one of the vibration exciters or vibration receivers provided is designed as a piezoelectric ceramic.

[0031] In a preferred embodiment, at least one of the vibration parts, preferably the vibration bridge, is made of a material different from the piezoelectric material, particularly preferably of metal, quite preferably of spring steel.

[0032] In a preferred embodiment, at least one of the vibration parts is configured as an elongated rod, preferably configured as a quadrilateral.

[0033] In a preferred embodiment, the vibration exciter and the vibration detector are arranged at the center of the vibration part associated therewith.

[0034] In a preferred embodiment, the resonant vibration part further has no further elements serving any purpose and is preferably uncoated. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention is described in somewhat more detail below with reference to the accompanying drawings.

[0036] in:

[0037] Figure 1 The first embodiment of the vibration bridge according to the utility model is schematically shown.

[0038] Figure 2 The second embodiment of the vibration bridge according to the utility model is schematically shown.

[0039] Figure 3 A third embodiment of the vibration bridge according to the present invention is schematically shown, and

[0040] Figure 4 A diagram is schematically shown for a vibrating wire sensor with one specific embodiment of a vibrating bridge according to the invention, which has a vibration exciter and a vibration detector with different resonance frequencies. DETAILED DESCRIPTION

[0041] Figure 1 A vibrating wire sensor 1 is schematically shown with connection points 1a and 1b for fastening it to a measuring point of a component or machine part of any type. Furthermore, the vibrating wire sensor 1 has a vibration bridge 2 and an electronic excitation component 3 for a vibration excitation element, which is designed here as a piezoelectric actuator 4, wherein the actuator 4 is connected to the excitation component 3 via lines 5, 6.

[0042] In the embodiment shown, the vibration bridge 2 has a vibration part in the form of a vibration beam, for example rectangular in cross section, which is configured as an excitation vibration part 7 and a vibration part in the form of a resonance vibration part 8. A left-hand base section 10 and a right-hand base section 11 of the vibration bridge 2 are integrally connected to these vibration parts, between which the excitation vibration part 7 and the resonance vibration part 8 extend. In each base section 10, 11, a clamping position 12, 13 is provided for clamping the vibration bridge 2 to the vibrating wire sensor 1 in a mechanism that is not shown for the sake of simplifying the drawing but is basically known to a person skilled in the art. Thus, the excitation vibration part 7 and the resonance vibration part 8 are mechanically connected to the clamping positions 12, 13 arranged opposite each other via the base regions 10, 11. The excitation vibration part 7 and the resonance vibration part 8 themselves have essentially the same resonance frequency and the same Q factor, because they are made of the same material here (but not necessarily for all embodiments); in addition, they are subjected to the same tensile load during operation. However, the Q factor of the exciter 7 is significantly reduced by the actuator 4 arranged thereon, wherein the resonance frequency of the exciter 7 also experiences a drift for the reasons mentioned at the outset.

[0043] During operation of the vibrating wire sensor 1, the excitation component 3 performs a frequency search by applying a voltage (excitation signal) via the lines 5, 6 to the piezoelectric actuator 4 at a frequency that changes continuously in a predetermined frequency interval. As a result, the actuator 4 causes the excitation oscillator 7 to be subjected to forced vibration, wherein the forced vibration in turn excites the resonant oscillator 8 via the adjacent regions of the base sections 10, 11. As a result, the resonant oscillator is in resonance as soon as the frequency generated by the excitation component 3 or the frequency of the excitation signal corresponds to the current resonant frequency of the resonant oscillator, which in turn is given by the tensile load of the resonant oscillator 8 currently caused by the clamping points 12, 13.

[0044] In the embodiment shown, during the frequency search, the excitation component 3 switches periodically between an excitation phase and a detection phase (ie, a non-excitation phase following the excitation phase).

[0045] In the corresponding detection phase, due to the damping of the excitation vibration part, the forced vibration of the excitation vibration part 7 decays rapidly, unless the excitation vibration part itself is now significantly excited by the resonant vibration part 8 (by the adjacent area of ​​the base sections 10, 11), but only when it is in resonance (and as long as its amplitude is still large enough for this in a short time, but this is the case for a long enough time). This excitation then generates an AC voltage through the piezoelectric effect in the actuator 4, which in the detection phase is applied to the excitation component 3 via the wires 5, 6 and represents the frequency and amplitude signal (detection signal) of the current vibration frequency of the excitation vibration part 7. Through this detection signal, it is detected based on the large amplitude of the detection signal that the resonant vibration part is in resonance and what the resonance frequency is.

[0046] Thus, in the detection phase, the excitation component 3 detects whether the resonant oscillator 8 is in resonance. If this is the case, the excitation component thereby detects the current resonance frequency of the resonant oscillator.

[0047] As a result, the vibration exciter can preferably also be operated as and as a vibration detector (in the embodiment shown, due to its piezoelectric properties).

[0048] The excitation component 3 can now also be designed by means of a suitable oscillating circuit in such a way that, if a resonant frequency of the resonant oscillator 8 is detected, this frequency is used in the excitation phase after the detection phase, so that the frequency search is interrupted and the excitation oscillator 7 continues to be maintained in forced vibration with the current resonant frequency of the resonant oscillator 8. This, on the one hand, compensates for the damping in the resonant oscillator 8, so that the resonant oscillator amplitude does not decrease.

[0049] On the other hand, however, it is also possible to track changing resonance frequencies: if the tensile load of the resonant oscillator 8 changes, the resonant oscillator will at the latest continue to vibrate at a new resonance frequency in the following non-excitation phase due to the vibration energy contained in it. This then also applies to the exciting oscillator 7 in the detection phase (via the adjacent areas of the base sections 10, 11), wherein this changed frequency is then detected by the excitation component 3 as a new resonance frequency and is used to excite the exciting oscillator in the next excitation phase.

[0050] With this feedback of the resonant frequency, a changing tensile load of the vibrating bridge 2 can be quickly followed - a time-consuming new frequency search is dispensed with. However, if the change in the tensile load occurs very suddenly, the resonant frequency is no longer detected. Subsequently, the frequency search can simply be restarted.

[0051] A vibrating wire sensor with a vibrating bridge is obtained, which preferably has an excitation component for the vibration excitation element, which is designed to detect a current detection signal generated by the vibration excitation element in a detection phase of the vibration excitation element. More preferably, the excitation component is designed to excite the vibration excitation element in an excitation phase of the vibration excitation element after the detection phase by the excitation signal with a frequency that corresponds to the detection signal generated by the vibration excitation element in the preceding detection phase.

[0052] During the entire frequency search, this "excitation / detection" cycle of the excitation component 3 is preferably repeated for each search frequency. The frequency search itself is also carried out in order to determine the resonance of the resonant vibration part in each case even in the case of a strong or sudden change in the tensile load of the vibration bridge 2, if it is no longer possible to detect the changed resonant frequency by feedback.

[0053] Instead of a frequency search, it is also possible to apply a single excitation pulse (Heaviside impulse) as an excitation signal to the excitation vibration part 7. All frequencies are reflected in the Heaviside impulse. As a result, the resonant vibration part 8 is excited at its resonant frequency, so that in the subsequent detection phase, for example, the piezoelectric element, such as the actuator 4, can generate a corresponding detection signal and transmit the detection signal to the excitation component 3. It is feasible for a person skilled in the art to provide a voltage step function to the piezoelectric element by correspondingly constructing the electronic device, thereby providing the Heaviside impulse to the excitation vibration part 7.

[0054] An evaluation unit of a vibrating wire sensor (not shown for simplicity) which is basically known to a person skilled in the art and is preferably provided in excitation component 3 outputs a measured value for the desired force / displacement measurement as a function of the detected resonance frequency of resonant oscillator 8 .

[0055] It is true that the excitation vibration part 7, due to the piezoelectric element 4 arranged thereon, appears to have properties that deteriorate for resonance measurement, in particular a reduced Q factor (increased damping), so that its resonance curve also has a large amplitude in a wide range around the resonance frequency (compared to the amplitude that decreases very rapidly near the resonance frequency in the case of only low damping, as is the case with the resonant vibration part) and a shift in its own resonance frequency due to the reasons explained at the beginning (change in mass, local hardening caused by changes in the properties of the adhesive, etc.). Due to this quality loss, the excitation vibration part 7 can also have a significant amplitude outside the resonance frequency of the resonant vibration part 8, but due to the high Q factor of the resonant vibration part 8, this does not cause interference, because the resonant vibration part has no significant amplitude outside its resonance frequency and therefore has too little vibration energy in the detection phase to be able to excite the excitation vibration part 7 sufficiently strongly for the resonant frequency signal.

[0056] Conversely, when the resonant frequencies of the two vibration parts 7, 8 differ from one another, the reduced Q factor of the exciting vibration part 7 can have a positive effect by having a wide range with high amplitudes around its resonant frequency. This is the case, for example, when the tensile stresses in the vibration parts 7, 8 differ from one another due to an undesirable assembly, when, for example, the clamping parts are not ideally screwed together, so that a torque is generated in the base section, or due to thermal stresses after welding. Thus, despite the different resonant frequencies, within the resonance range of the resonant vibration part 8, the amplitude of the exciting vibration part 7 is still large enough to be able to excite the resonant vibration part sufficiently strongly so that the resonant vibration part can be in resonance (see, for this, Figure 4 description).

[0057] However, the negative effects of placing the vibration exciter in the base section, as disclosed, for example, in CA 2619996 mentioned at the outset and leading to the generation of significant and therefore disruptive harmonics, loss of kinetic energy via nearby clamping points, etc., are relatively eliminated.

[0058] Figure 2 Another embodiment of a vibration bridge 20 according to the utility model is shown, which has three vibration parts arranged in parallel in a common plane instead of two, namely, a resonant vibration part 21 located in the middle, an excitation vibration part 22 on one side, and a detection vibration part 23 placed on the other side of the resonant vibration part 21. On the excitation vibration part, there is a vibration excitation element which is also configured as a piezoelectric actuator 24 here, and on the detection vibration part 23, there is a vibration detector 25 configured as a piezoelectric element. Wires 26, 27 and 28, 29 connect the actuator 24 and the detector 25 to an excitation component 30 which is shown symbolically and in dashed lines. In order to simplify the drawing, the vibrating wire sensor itself in which the vibration bridge 20 is installed is not shown.

[0059] During operation, a frequency search is again performed by the excitation component 30, wherein the frequency Figure 2 In the embodiment shown in the figure, the detection stage is eliminated because the vibration detector 25 obtains the frequency and amplitude of the detection vibration part 23 simultaneously with the excitation of the excitation vibration part 22, generates a corresponding detection signal, and outputs the detection signal to the input part 31 for the detection signal schematically shown in the figure and to the excitation component 30, so that the excitation component 30 can process the detection signal.

[0060] If the excitation vibration part 22 is excited by the actuator 24 during the frequency search, the excitation vibration part is in forced vibration at a frequency preset by the actuator 24. If this frequency does not correspond to the resonance frequency of the resonant vibration part 21 in a narrow range corresponding to a high Q factor, the resonant vibration part does not vibrate together, and thus the detection vibration part 23 also does not vibrate together, because no significant deformation of the edge region of the base section 10, 11 occurs between the detection vibration part and the resonant vibration part 21.

[0061] However, if the actuator 24 reaches the resonant frequency of the resonant vibration part 21 accurately enough during the frequency search, the resonant vibration part is in vibration. Only then is sufficient energy transmitted to the detection vibration part 23, so that the detection vibration part also vibrates. Even if the Q factor of the detection vibration part decreases or the resonant frequency drift of the detection vibration part 25 arranged thereon occurs, the amplitude of the detection vibration part still increases significantly. The vibration of the detection vibration part 23 is in antiphase with the resonant vibration part 21, but has the same frequency as the resonant frequency of the resonant vibration part 21.

[0062] The vibration detector 25 now generates a detection signal for detecting the amplitude of the vibration part 23 and its frequency, wherein a significant increase in the amplitude indicates that the relevant frequency is the resonance frequency of the resonant vibration part 22. However, it should be noted again that the resonance frequency of the resonant vibration part 22 can also be identified only by the amplitude, because the resonance frequency corresponds to the frequency of the excitation signal. However, preferably, the detection signal contains the amplitude and the frequency, so that at a large amplitude, the frequency of the detection signal is identified as the resonance frequency.

[0063] Thus, if the resonant frequency of the resonant vibration part 22 has been found, it is possible to realize a phase-correct feedback of the frequency of the detector signal via the excitation component 3 to the actuator 24, which thus maintains the current vibration amplitude at the resonant frequency of the resonant vibration part. To this end, a person skilled in the art can provide the excitation component 3 (e.g., also according to Figure 1 In the embodiment of FIG. 1 , a corresponding oscillating circuit is provided. Thus, it is also possible to follow the change of the resonant frequency, such as according to Figure 1 This is the case with an embodiment in which the frequency search can simply be restarted if the change is too drastic.

[0064] Already targeted Figure 1 The described arrangement of , initiating the resonant oscillation of the resonant oscillating part 22 by means of a Heaviside pulse, is also possible here (generally speaking, for example in all embodiments according to the invention).

[0065] according to Figure 2 , a vibration bridge is obtained in which three vibration parts 21 to 23 are arranged parallel to each other in a plane, wherein one of the outer vibration parts is provided with a vibration exciter 24 and another with a vibration detector 25, and the middle vibration part 21 has neither, wherein preferably the outer vibration parts can also be placed under tension. More preferably, the middle vibration part 21 is completely uncovered, i.e., also without a coating or other elements for any purpose. Thus, the resonant vibration part also has no other elements for any purpose (in addition to the vibration exciter or the vibration detector) and is preferably not coated.

[0066] The lowest energy consumption of the vibration bridge 2, 20 is obtained when the center of gravity of the vibration bridge remains essentially stationary during operation. Since the vibration parts 7, 8 and 21 to 23 vibrate in antiphase, the result is that the mass of the outer vibration parts 22, 23, preferably with the vibration exciter 24 and the vibration receiver (Schwingungsabnehmer, sometimes called vibration pickup) 25, is essentially the same as the mass of the central vibration part 21, and the vibration bridge 20 is designed in such a way that the center of gravity of the vibration bridge 20 remains essentially stationary when the outer vibration parts 22, 23 vibrate in antiphase with respect to the central vibration part 21.

[0067] Preferably, the vibration exciter (at Figure 1 and 2 The actuator 4, 24 in the detector is arranged in the center of the exciting vibration part 7, 22, thereby avoiding the generation of interfering harmonics in its vibration performance. More preferably, this is also the case for the vibration detector 25 on the detector.

[0068] Figure 3 Another embodiment of a vibrating bridge 40 for a vibrating wire sensor is shown. Figure 2 ) Differently, the excitation vibration part and the detection vibration part are not constructed as vibration beams, but as vibration tongues, here constructed as excitation vibration tongues 41 and detection vibration tongues 42, and the vibration tongues respectively have at their ends preferably piezoelectric actuators 43 as vibration excitation elements or piezoelectric vibration detectors 44, both of which are connected to the excitation component 30 or its input part 31 for detecting signals in an operative manner via corresponding wires 45, 46 or 47, 48.

[0069] The excitation vibration tongue 41 is opposite to the balancing vibration tongue 50 provided with the balancing weight 49, and the detection vibration tongue 42 is opposite to the balancing vibration tongue 52 provided with the balancing weight 51. As a result, the vibration bridge 40 as a whole, especially its center of gravity, is better kept stationary during operation.

[0070] The resonant vibration part 53 again has no vibration exciter or vibration detector and preferably no other elements, likewise no coating of any kind. Figure 1 and especially Figure 2 The implementation method is carried out similarly.

[0071] and Figure 2 Compared to the embodiment of the present invention (assuming the same mechanism in the vibrating wire sensor), a measuring range is half as large, since only the tensile loads have to be absorbed by the resonant oscillator 53 - the resolution remains the same. However, due to the half-larger measuring range, a resolution that is twice as fine is obtained for this half of the measuring range.

[0072] As a result, preferably, the vibration part provided with the vibration exciter is configured as a vibration tongue, wherein more preferably, another vibration part configured as a vibration tongue and having a vibration detector is provided. Here, more preferably, the vibration part configured as a vibration tongue is arranged opposite to the matching vibration tongue. Finally, more preferably, the matching vibration tongue is provided with a counterweight, which has such a mass that the matching vibration tongue vibrates substantially in phase with the vibration tongue associated therewith during the operation of the vibration bridge.

[0073] According to the utility model, Figures 1 to 3 In the embodiments shown in the figure, what is common to the vibration bridge for the vibrating wire sensor is that it has clamping parts arranged opposite to each other for connecting the vibration bridge to the vibrating wire sensor and a plurality of vibration parts arranged between the clamping parts, which are mechanically connected to the fixing parts, wherein at least one of the vibration parts is placed under tension therethrough and has no vibration exciter or vibration detector, and another vibration part is provided with a vibration exciter.

[0074] To be more precise and to put it in general terms, a vibration bridge for a vibrating wire sensor has clamping parts arranged opposite to each other for connecting the vibration bridge to the vibrating wire sensor and a plurality of vibration parts arranged between the clamping parts and mechanically connected to the clamping parts, one of the vibration parts being configured as a resonant vibration part, wherein the resonant vibration part can be placed under tension via the clamping parts and does not have a vibration exciter or a vibration detector and is arranged on another vibration part having a vibration exciter.

[0075] Preferably, at least one of the vibration exciters or vibration detectors provided is designed as a piezoelectric element. More preferably, at least one of the vibration parts is designed as an elongated rod, preferably as a quadrilateral (more preferably, all vibration parts of an embodiment are designed identically). More preferably, at least one of the vibration parts, more preferably the vibration bridge, is made entirely of metal, spring steel or other suitable materials. Suitable are spring-like elastic materials with low damping, so that a resonance curve with a clearly definable resonance frequency appears due to a sharp increase in amplitude. Preferably, the spring-like elastic material also has a high yield limit, which then leads to a wide measuring range. However, preferably, the material is different from a piezoelectric material, because it should not be self-excited or detected, but excited or detected by a vibration exciter or a vibration detector, whereby a material that is better suited than a piezoelectric material can be used.

[0076] Finally, according to the utility model, a vibrating wire sensor with a vibrating bridge has an excitation component for a vibration exciter, which is provided with an input part for a frequency signal of a vibration detector, and the excitation component is constructed to output a frequency corresponding to the frequency signal as an excitation frequency to the vibration exciter.

[0077] Figure 4 Shown with Figures 1 to 3 The resonance curve 61 of the resonant vibration parts 7, 22, 41 and the Figures 1 to 3 Graph 60 of a resonance curve 62 of a detection vibration part 8, 23, 42. Here, the vertical axis represents the amplitude A of the vibration of the corresponding vibration part, and the horizontal axis represents the frequency f.

[0078] The detection amplitude A of the excitation components 3 and 30 can also be seen in the line diagram. D , which indicates when the amplitude of the detection signal (resonance curve 62) is captured as an amplitude and processed as such, or when it is discarded as an amplitude, for example as complete noise in the detection signal (or for other reasons). D below a threshold value, can no longer be detected by the corresponding actuation component 3, 30, and Figure 4 Draw with dotted lines.

[0079] Detection amplitude A D exist Figure 4 Schematically shown in FIG. 1 , it is related to the structural scheme of the vibration bridge, the vibration detector and the excitation assembly 3, 30 selected by a person skilled in the art in each specific case, and does not have to be constant in the frequency range of interest, but for the sake of simplicity of illustration, Figure 4 Draw it as a straight line in .

[0080] For the resonance curve 61 of the resonant vibration parts 7, 22, and 41, the detection amplitude A D is not important, since this detection amplitude is not detected - accordingly the resonance curve 61 is shown without the dashed area. However, the detection amplitude A D It can also be used for a comparison of the resonance curves 61 , 62 , since a comparison is possible at the same amplitude.

[0081] As described above, the resonance frequencies f of the resonant vibration parts 7, 22, and 41 are Rres and the resonance frequency f of the detection vibration parts 8, 23, 42 Dres In contrast, the resonance curve 61 of the resonant vibration part 7 , 22 , 41 has a narrow frequency range f due to its high Q factor. R范围 , and the resonance curve 62 of the detection vibration part 8, 23, 42 has a wider frequency range f due to its lower Q factor D范围 As a result, the resonance curve 62 runs flatter than the resonance curve 61 .

[0082] By using the piezoelectric actuators 4, 24, 43 in the resonance frequency range f R范围 Internal excitation, the amplitude of the resonant vibration part 7, 22, 41 becomes larger, and more energy is transferred to the detection vibration part 8, 23, 42, and the amplitude of the detection vibration part also increases until it exceeds the detection amplitude A D .

[0083] The amplitude required for this purpose of the resonant vibration parts 7, 22, 41, the transmission amplitude A A This is related to the specific structural scheme of the vibration bridge 1. If the transmission amplitude A is exceeded A , in the corresponding frequency range of the resonant vibration part 7, 22, 41, the vibration of the detection vibration part 8, 23, 42 according to the resonance curve 62 is generated, and this vibration then (because it is greater than the detection amplitude A D ) can be obtained through the excitation components 3, 30.

[0084] In other words, preferably, in order to determine the resonant frequency of the resonant vibration part 7, 22, 41 by the excitation component 3, 30, the resonance curve 61 of the resonant vibration part 7, 22, 41 is A The above detection vibration part 8, 23, 42 resonance curve 62 in the detection amplitude A D The above must overlap, that is, have at least one common frequency, preferably a common frequency range. Preferably, the vibration bridge 1 and the excitation components 3, 30 are designed such that the detection amplitude A D and the transfer amplitude A A overlap to keep the maximum possible overlap.

[0085] This means that, as long as there is overlap, the deviation of the resonance frequencies from each other (for example due to assembly errors or for other reasons) and the lower Q factor of the detection vibration part 8, 23, 42 are not a problem. Thus, a low Q factor is completely desirable because a larger deviation of the resonance frequency is allowed with a flatter resonance curve 62.

[0086] This results in a vibrating wire sensor 1 with a vibrating bridge 20 , 40 , wherein the vibrating bridge 20 , 40 also has a detection vibration part 23 , 42 with a resonance frequency f 21 , 53 . Rres Different resonant frequencies f Dres The vibration bridge 20, 40 is designed such that the detection vibration part 23, 42 is in operation at a resonance amplitude A higher than the transmission amplitude A of the resonance vibration part 21, 53. A The amplitude of the vibration itself is higher than the detection amplitude A of the excitation component 30 D The vibrating wire sensor 1 is provided with an excitation component 30, which is configured to generate an excitation signal for the vibration exciter 24, 44 and process the currently detected detection signal of the vibration detector 25, 45 arranged on the detection vibration part 23, 42, wherein the detection amplitude A is lower than the detection amplitude A. D The detection signal is not used to determine the frequency and amplitude of the detection vibration part 7, 23, 42, wherein the resonance curves 61, 62 of the resonant vibration part (21, 53) and the detection vibration part (23, 42) are higher than the detection amplitude A D and the transfer amplitude A A In such a vibrating wire sensor, intentionally or unintentionally different resonance curves 61, 62 and a lower Q factor of the detection vibrating part are allowed.

[0087] In a preferred embodiment, the excitation component 30 is further configured to detect the vibration when the frequency of the vibration component is not above the transmission amplitude A. A When the frequency range of the resonant vibration part is within the predetermined permissible frequency interval, the currently detected detection signal is not used to determine the frequency and amplitude of the detection vibration part 7, 23, 42. As a result, the vibration of the detection vibration part 23, 42 that is not triggered by the resonant vibration part 21, 53 can be abandoned from the beginning.

Claims

1. A vibration bridge (2, 20, 40) for a vibrating wire sensor (1), comprising clamping locations (12, 13) arranged opposite one another for connecting the vibration bridge (2, 20, 40) to the vibrating wire sensor (1), and comprising a plurality of vibration parts (7, 8, 21 to 23) arranged between the clamping locations (12, 13) and mechanically connected to the clamping locations (12, 13), wherein: During operation, one of the multiple vibration parts is placed under tension or pressure via the clamping position (12, 13), characterized in that only one of the vibration parts placed under tension or pressure is constructed as a resonant vibration part (8, 21) and has no vibration exciter or vibration detector, and the other vibration part (7, 22, 23) is provided with a vibration exciter (4, 24, 43).

2. The vibration bridge (2, 20, 40) according to claim 1, wherein: The vibration exciter can be operated as a vibration detector.

3. The vibration bridge (2, 20, 40) according to claim 1, wherein: Three vibration parts are provided which are arranged parallel to one another in a plane, wherein one of the outer vibration parts is provided with a vibration exciter and another with a vibration detector, and at least the central vibration part can be placed under tension and has no vibration exciter and vibration detector.

4. The vibration bridge (2, 20, 40) according to claim 3, wherein: The mass of the outer vibration part with the vibration exciter and the vibration receiver is substantially the same as the mass of the middle vibration part, and the vibration bridge (2, 20, 40) is constructed in such a way that when the outer vibration part vibrates in antiphase with respect to the middle vibration part, the center of gravity of the vibration bridge (2, 20, 40) remains substantially stationary.

5. The vibration bridge (2, 20, 40) according to claim 1, wherein: The vibration part provided with the vibration exciter (43) is configured as a vibration tongue (41).

6. The vibration bridge (2, 20, 40) according to claim 1, wherein: Another vibration part configured as a vibration tongue (42) is provided, and has a vibration detector (44).

7. The vibration bridge (2, 20, 40) according to claim 5 or 6, wherein: The vibrating portion configured as a vibrating tongue (41, 42) is disposed opposite to the mating vibrating tongue (50, 52).

8. The vibration bridge (2, 20, 40) according to claim 7, wherein: The engaging tongue is provided with a counterweight which has such a mass that, when the vibration bridge (2, 20, 40) is in operation, the engaging tongue vibrates substantially in phase with the tongue associated therewith.

9. The vibration bridge (2, 20, 40) according to any one of claims 1 to 6, wherein: At least one of the vibration exciters or vibration receivers provided is designed as a piezoelectric ceramic.

10. The vibration bridge (2, 20, 40) according to any one of claims 1 to 6, wherein: At least one of the vibration parts is made of a material different from the piezoelectric material.

11. The vibration bridge (2, 20, 40) according to any one of claims 1 to 6, wherein: At least one of the vibration parts is configured as an elongated rod.

12. The vibration bridge (2, 20, 40) according to claim 3, wherein: The vibration exciter (7, 22, 43) and the vibration detector (25, 44) are arranged at the center of the vibration part associated therewith.

13. The vibration bridge (2, 20, 40) according to claim 1, wherein: The resonant vibration part (8, 21, 53) also has no other elements for any purpose.

14. The vibration bridge (2, 20, 40) according to claim 3, wherein: The outer vibrating part can also be placed under tension.

15. The vibration bridge (2, 20, 40) according to claim 10, wherein: At least one of the vibration parts is made of metal.

16. The vibration bridge (2, 20, 40) according to claim 15, wherein: The metal is spring steel.

17. The vibration bridge (2, 20, 40) according to claim 10, wherein: The vibration bridge (2, 20, 40) is made of a material different from the piezoelectric material.

18. The vibration bridge (2, 20, 40) according to claim 17, wherein: The vibration bridge (2, 20, 40) is made of metal.

19. The vibration bridge (2, 20, 40) according to claim 18, wherein: The metal is spring steel.

20. The vibration bridge (2, 20, 40) according to claim 11, wherein: At least one of the vibration parts is configured in a quadrilateral.

21. The vibration bridge (2, 20, 40) according to claim 13, wherein: The resonant vibration portion (8, 21, 53) is not coated.

22. A vibrating wire sensor (1) with a vibrating bridge (2, 20, 40) according to any one of claims 1 to 21, wherein: The vibrating wire sensor has an excitation component (30) for the vibration exciter, which is provided with an input part (31) for the frequency signal of the vibration detector (25, 44), and the excitation component is designed to output a frequency corresponding to the frequency signal as an excitation frequency to the vibration exciter.

23. A vibrating wire sensor (1) with a vibrating bridge (2, 20, 40) according to claim 1, wherein: The vibrating wire sensor has an excitation component (30) for the vibration exciting element, which is designed to detect a current detection signal generated by the vibration exciting element in a phase without excitation of the vibration exciting element.

24. A vibrating wire sensor (1) according to claim 23, wherein: The excitation component (30) is further designed to excite the vibration exciting element by means of the excitation signal in an excitation phase following a non-excitation phase of the vibration exciting element at a frequency that corresponds to a detection signal generated by the vibration exciting element in a preceding non-excitation phase.

25. A vibrating wire sensor (1) with a vibrating bridge (2, 20, 40) according to claim 1, wherein: The vibration bridge (20, 40) also has a detection vibration part (23, 42) with a resonance frequency f with the resonance vibration part (21, 53). Rres Different resonant frequencies f Dres The invention relates to a vibration bridge having a resonance curve (62) extending flatter than the resonance curve (61) of the resonance vibration part (21, 53), and the vibration bridge (20, 40) is constructed so that the detection vibration part (23, 42) is in operation at a higher transmission amplitude A than the resonance vibration part (21, 53). A The excitation component (30) vibrates with a detection amplitude A higher than that of the excitation component (30). D The vibrating wire sensor (1) is provided with an excitation component (30) which is configured to generate an excitation signal for a vibration exciter (24, 44) and process a currently detected detection signal of a vibration detector (25, 45) arranged on the detection vibration part (23, 42), wherein the detection amplitude A is less than the detection amplitude A. D The detection signal is not used to determine the frequency and amplitude of the detection vibration part (7, 23, 42), wherein the resonance curves (61, 62) of the resonant vibration part (21, 53) and the detection vibration part (23, 42) are higher than the detection amplitude A D and the transfer amplitude A A The higher of the two overlaps.

26. A vibrating wire sensor according to claim 25, wherein The excitation component (30) is further configured to: when the frequency of the detection vibration part is not higher than the transmission amplitude A A When the frequency range of the resonant vibration part is within a predetermined allowed frequency interval, the frequency and amplitude of the detection vibration part (7, 23, 42) are determined without using the currently detected detection signal.

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