Method for operating coriolis mass flow meter and corresponding coriolis mass flow meter

Abstract

To check that multiplexers are simultaneously at a measurement operation position without interrupting a measurement operation of a Coriolis mass flow meter.SOLUTION: In a Coriolis mass flow meter (2), a measuring tube through which a medium flows is vibrated by a vibration generator, vibrations at an inlet side and an outlet side of the measuring tube are detected by vibration sensors (3a, 3b) as vibration signals (s1, s2), the vibration signals (s1, s2) at respective measurement operation positions (WPM) of two multiplexers (4a, 4b) are transmitted to a control and evaluation unit (5), a vibration signal phase difference (Δφ) between transmitted vibration signals (st1, st2) in the control and evaluation unit (5) is specified to obtain a mass flow, the mass flow is obtained on the basis of the vibration signal (s1) phase-shifted by a phase deviation (φh), and it is detected that respective operation positions (MP) of the two multiplexers (4a, 4b) are simultaneously at the measurement operation positions (WPM) by comparing the vibration signal phase difference (Δφ) with the phase deviation (φh).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for operating a Coriolis mass flow measuring device, the Coriolis mass flow measuring device having at least one measuring tube, at least one vibration generator, at least two vibration sensors, at least one first multiplexer and a second multiplexer each having a plurality of operating positions, and at least one control and evaluation unit. A medium can flow through the measuring tube. The vibration generator excites and vibrates the measuring tube. The first vibration sensor and the second vibration sensor detect the vibration of the measuring tube on the inflow side and the outflow side, and supply it as a first vibration signal and also as a second vibration signal. At the measurement operating position of the first multiplexer, the first vibration signal is transmitted to the control and evaluation unit at least indirectly via the first multiplexer. At the measurement operating position of the second multiplexer, the second vibration signal is transmitted to the control and evaluation unit at least indirectly via the second multiplexer. The control and evaluation unit determines the vibration signal phase difference between the transmitted first vibration signal and the transmitted second vibration signal, and obtains the mass flow rate from the vibration signal phase difference. The present invention further relates to a corresponding Coriolis mass flow measuring device that implements the above method during operation.

[0002] Coriolis mass flow measurement devices have been known from the prior art for decades. By utilizing the Coriolis effect, the mass flow rate of the medium flowing through the measuring tube is determined. For this purpose, the measuring tube through which the medium flows is vibrated by at least one vibration generator as described above. The vibration of the measuring tube is detected on the inflow side and the outflow side, in the flow direction, by vibration sensors acting on the measuring tube and supplied as vibration signals. In the case of no flow, the detected vibration and the vibration signals supplied by the two vibration sensors are in the same phase in the theoretically ideal case. When there is a mass flow rate, Coriolis forces with different directions occur on the inflow side and the outflow side, and due to this Coriolis force, a minimum phase shift occurs between the displacements and thus also between the two vibrations detected by the vibration sensors. Therefore, in this case, a vibration signal phase difference also occurs between the vibration signals of the vibration sensors. The vibration signal phase difference is extremely small and generally in the region of (angular) minutes, but nevertheless this vibration signal phase difference contains information regarding the mass flow rate flowing through the measuring tube. The phase shift is proportional to the mass flow rate in the measuring tube. Therefore, this phase shift is evaluated and the mass flow rate is determined therefrom.

[0003] The use of multiplexers in each measurement path, each leading from one of the two vibration sensors to the control and evaluation unit, can have quite different reasons. For example, it may be desirable to use the measurement channel not only for detecting the vibration signals supplied by the vibration sensors, but also to detect another measured quantity supplied to the connected measurement channel by the multiplexer. Another reason may be to implement a switching of the measurement channels, for example, to switch the first vibration sensor to the second measurement channel and the second vibration sensor to the first measurement channel so as to be able to average different propagation times in the measurement channels.

[0004] When the first vibration signal and the second vibration signal are transmitted to the control and evaluation unit at least indirectly via a multiplexer, this means that the original vibration signal, i.e., the vibration signal arriving directly from the vibration sensor, may undergo a very extensive range of signal processing before reaching the control and evaluation unit. That is, for example, analog amplification, impedance conversion, analog / digital conversion, low-pass filtering, phase detection, and others may be performed. However, this is not of individual or detailed interest. In any case, it is important that the signals based on the vibrations originally detected by the vibration sensor are transmitted to the control and evaluation unit respectively, and the signals arriving there are referred to as the transmitted vibration signals.

[0005] Therefore, the multiplexer is arranged in the starting region of the measurement chain (generally immediately after the vibration sensor in the signal path), that is, in the region of the measurement section operating with analog signals. Therefore, the multiplexer is generally also an analog multiplexer. The multiplexer has a plurality of operating positions, and these operating positions determine which input of the multiplexer is connected to the output of the multiplexer. In order to minimize the resistance caused by the multiplexer in the measurement path, especially in measurement technology, it is preferably used together with gold-plated switch contacts. In an analog multiplexer realized mechanically, it is exactly possible that the change between different operating positions does not work well.

[0006] Therefore, what is known in the prior art is that two multiplexers together check whether each is in the measurement operation position, that is, whether the first multiplexer conducts the vibration signal of the first vibration sensor and whether the second multiplexer conducts the vibration signal of the second vibration sensor. For this purpose, a harmonic test signal is connected to the measurement channel input side where the vibration sensor is connected instead of the vibration signal of the vibration sensor. Thereby, the control and evaluation unit can identify whether this test signal is acquired in both measurement channels. The acquisition is premised on the measurement operation positions of the two multiplexers. The drawback of this method is that when checking the correct operation position of the multiplexer, the measurement operation of the Coriolis mass flow measuring device must be stopped, which of course limits the measurement operation.

[0007] Therefore, an object of the present invention is to provide a method that can check whether the multiplexer is simultaneously in the measurement operation position without interrupting the measurement operation.

[0008] The problem derived above is solved by the features of the characterizing part of independent claim 1 in the method of operating the Coriolis mass flow measuring device described at the beginning, that is, the first vibration signal is phase-shifted by a phase deviation, and the phase-shifted first vibration signal is transmitted to the control and evaluation unit at least indirectly via the first multiplexer. The control and evaluation unit determines the mass flow considering the first vibration signal transmitted with the phase shift by the phase deviation, and the control and evaluation unit compares the vibration signal phase difference with the phase deviation of the first vibration signal to detect whether the operation positions of the first multiplexer and the second multiplexer are simultaneously in the measurement operation position.

[0009] According to the described method, it is possible to easily identify whether the first multiplexer and the second multiplexer are simultaneously in the measurement operation position without interrupting the measurement operation of the Coriolis mass flow measuring device.

[0010] According to a preferred embodiment of the present method, it has been identified that the phase deviation that phase-shifts the first vibration signal is significantly larger than the maximum measured phase difference that can be caused by the mass flow rate within the measurement range. Preferably, the phase deviation is selected to be at least 10 times larger, more preferably at least 100 times larger than the maximum measured phase difference. The measured phase difference is generally in the range of a fraction of a degree. Assuming that the operating frequency of the Coriolis mass flow measuring device is in the kHz range, it is clear that the general measured phase difference is equivalent to the detection of a time difference in the range of a few microseconds (and below this time range).

[0011] In one preferred embodiment of the present method, the phase deviation of the first vibration signal is 180°, which can be relatively easily realized, for example, by an analog inverter circuit. In one particularly preferred embodiment of the present method, the 180° phase deviation of the first vibration signal is realized by assembling or connecting the first vibration sensor and the second vibration sensor such that the vibration signal generated by the same vibration of the measurement tube (thus at zero flow rate) is phase-shifted by 180°. This can be achieved, for example, by attaching coils as vibration sensors in opposite directions to the measurement tube, thereby generating exactly opposite vibration signals at the corresponding identical terminals of the vibration sensors due to the same movement of the measurement tube, or by attaching the coils as vibration sensors in the same direction to the measurement tube, but by replacing the terminals of the first coil as the first vibration sensor and connecting them to the terminals of the first multiplexer compared to the connection of the terminals of the second coil as the second vibration sensor to the terminals of the second multiplexer. The last two variant solutions shown have the advantage that no additional circuit-technical costs are required.

[0012] When the control and evaluation unit determines the mass flow rate taking into account the first vibration signal that has been shifted and transmitted only by the phase deviation, this means calculating the phase deviation from the vibration signal phase difference or from the determined phase of the transmitted first vibration signal, and determining the mass flow rate based on the vibration signal phase difference corrected in this way.

[0013] Preferably, when the vibration signal phase difference (i.e., the uncorrected vibration signal phase difference in which the phase deviation of the transmitted first vibration signal still exists) is within the tolerance range around the phase deviation of the first vibration signal, the control and evaluation unit detects the simultaneous measurement operating positions of the first multiplexer and the second multiplexer. Preferably, the tolerance range has the width of the maximum measured phase difference. This is because the variation of the phase deviation within this range is only possible by further measurements.

[0014] In one advantageous development of the method, the control and evaluation unit compares the operating positions detected by the first multiplexer and the second multiplexer (whether the first multiplexer and the second multiplexer are simultaneously in the measurement operating position) with the preset target operating positions of the first multiplexer and the second multiplexer (whether the target operating positions of the first multiplexer and the second multiplexer are simultaneously in the measurement operating position), and when the detected operating position deviates from the target operating position, the control and evaluation unit signals a deviation signal.

[0015] In one embodiment, the above-mentioned deviation signal is stored as information in the memory of the control and evaluation unit, and / or output as a bus message via the fieldbus interface of the Coriolis mass flow measuring device, and / or output as a bus message via the diagnostic interface where no measurement data is output, and / or coded as a current value and output via the current interface of the Coriolis mass flow measuring device.

[0016] The above-mentioned problem is similarly solved in the Coriolis mass flow measuring device, which has already been described many times, by shifting the phase of the first vibration signal by only a phase deviation and transmitting the phase-shifted first vibration signal, at least indirectly, to the control and evaluation unit via the first multiplexer. The mass flow rate is determined by the control and evaluation unit considering the first vibration signal that has been shifted and transmitted by only the phase deviation. The control and evaluation unit compares the vibration signal phase difference with the phase deviation of the first vibration signal to detect whether the operating positions of the first multiplexer and the second multiplexer are simultaneously in the measurement operating position.

[0017] In other respects, the various embodiments of the method described above are implemented by a correspondingly configured control and evaluation unit in the Coriolis mass flow measuring device. Preferably, the Coriolis mass flow measuring device is realized by assembling or connecting the first vibration sensor and the second vibration sensor such that the phase deviation is 180° and the vibration signals generated by the same vibration signal of the measuring tube are phase-shifted by 180°. Here, this 180° phase shift is particularly due to the coil as the vibration sensor being mounted on the measuring tube in the opposite direction, or the coil as the vibration sensor being mounted on the measuring tube in the same direction, but the terminals of the first coil as the first vibration sensor are connected to the terminals of the first multiplexer after being replaced compared to the connection between the terminals of the second coil as the second vibration sensor and the terminals of the second multiplexer.

[0018] Specifically, there are various possibilities for constructing and developing the method according to the present invention for operating the Coriolis mass flow measuring device and the corresponding Coriolis mass flow measuring device. For this, reference may be made to the patent claims dependent on the independent claims and the description of the preferred embodiments related to the drawings.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

[0020] In FIGS. 1 to 3, there are respectively shown a method 1 for operating a Coriolis mass flow measurement device 2 and specific specific aspects of the Coriolis mass flow measurement device 2 that are of interest for understanding the subject matter of the present invention hereinafter. The Coriolis mass flow measurement device 2 has at least one measurement tube due to functional requirements and at least one vibration generator that excites the measurement tube into harmonic vibration, generally in the fundamental mode of the measurement tube. The two elements are not shown for clarity. The Coriolis mass flow measurement device 2 considered here further has at least two vibration sensors 3a, 3b, at least one first multiplexer 4a and a second multiplexer 4b each having a plurality of operating positions WP, and at least one control and evaluation unit 5.

[0021] During the operation of the Coriolis mass flow measurement device 2, a medium flows through the measurement tube, and the vibration of the measurement tube is detected at the inlet side and the outlet side by the first vibration sensor 3a and the second vibration sensor 3b shown as coils in this figure, and is supplied as a first vibration signal s1 and also as a second vibration signal s2. The first vibration signal s1 has a phase position φ1, and the second vibration signal s2 has a phase position φ2. In the figure, both numbers and letters are used as reference signs. The letters only have the nature of reference signs, but with these letters, the description, understanding of the drawings, and construction of relationships become much easier.

[0022] At the measurement operation position WPM of the first multiplexer 4a, the first vibration signal s1 is indirectly transmitted to the control and evaluation unit 5 via the first multiplexer 4a, and at the measurement operation position WPM of the second multiplexer 4b, the first vibration signal s2 is indirectly transmitted to the control and evaluation unit 5 via the second multiplexer 4b. By the expression "indirectly transmitted", the situation is considered where further signal processing may be performed on the first vibration signal s1 and the second vibration signal s2 supplied by the vibration sensors 3a, 3b until the vibration signals s1, s2 finally reach the control and evaluation unit 5. Therefore, although the first vibration signal s1 and the second vibration signal s2 may be converted depending on the situation, this conversion is not a problem in detail here. In any case, finally in the control and evaluation unit 5, the first vibration signal s1 arrives as the first transmitted vibration signal st1 having the phase position φt1, and finally in the control and evaluation unit 5, the second vibration signal s2 arrives as the transmitted second transmitted vibration signal st2 having the phase position φt2. Then, the control and evaluation unit 5 specifies the vibration signal phase difference Δφ between the first transmitted vibration signal st1 and the second transmitted vibration signal st2, and finally, from the vibration signal phase difference Δφ, the mass flow rate represented as the dot m in the figure, that is, the time change of the mass flowing through the measurement pipe, is obtained.

[0023] In FIG. 1, what is idealized and shown in relation to the control and evaluation unit 5 is that the phase difference Δφ between the phase position φt1 of the first transmitted vibration signal st1 and the phase position φt2 of the second transmitted vibration signal st2 is equal to the difference between the phase position φ1 of the first vibration signal s1 and the phase position φ2 of the second vibration signal st2. Practically, this should not necessarily be the case (due to disturbing actions), but this is not a problem in the object of the method actually of interest in the present invention. In FIGS. 1 and 2, the signal processing through which the detected first vibration signal s1 and the detected second vibration signal s2 pass is schematically shown as the measurement channels 6a, 6b.

[0024] The multiplexers 4a, 4b are implemented as analog multiplexers. In such multiplexers, there is a possibility of an error that the switching between different operating positions WP of the multiplexer does not occur. As already described in the general description section, the multiplexers 4a, 4b are used to connect various different measurement signals to the measurement channels 6a, 6b. In the measurement operating position WPM, the first vibration signal s1 is transferred to the control and evaluation unit 5 via the first measurement channel 6a, and the second vibration signal s2 is similarly transferred to the control and evaluation unit 5 via the second measurement channel 6b.

[0025] Another operating position WP of the multiplexers 4a, 4b is shown, which realizes an altered operating position WPC in which the first vibration signal s1 is connected to the second measurement channel 6b and the second vibration signal s2 is connected to the first measurement channel 6a. This is used, for example, in many cases for removing the propagation time difference in the different measurement channels 6a, 6b by calculation in the control and evaluation unit 5. Another operating position WP of the multiplexers 4a, 4b is further shown, and in this other operating position WP, for example, yet another measurement signal can be led to the measurement channels 6a, 6b, but this will not be described in more detail in the figure.

[0026] In the prior art shown in FIG. 1, one possibility is shown to check whether the multiplexers 4a, 4b are in their measurement operating positions WPM. Thus, what is checked is whether both multiplexers 4a, 4b are together in the measurement operating position WPM, that is, whether the first multiplexer 4a conducts the vibration signal s1 of the first vibration sensor 3a to the control and evaluation unit 5, and whether the second multiplexer 4b conducts the vibration signal s2 of the second vibration sensor 3b to the control and evaluation unit 5. For this purpose, instead of the vibration signals s1, s2 of the vibration sensors 3a, 3b, a harmonic test signal ts is connected to the input sides of the multiplexers 4a, 4b connected upstream of the respective measurement channels 6a, 6b, whereby it is possible for the control and evaluation unit 5 to identify whether this test signal ts is obtained in both measurement channels 6a, 6b. Although not shown in detail in FIG. 1, in order to achieve the disconnection of the vibration sensors 3a, 3b from the input sides of the multiplexers 4a, 4b, sometimes further circuit technical means are required, but this is not a problem here either. The disadvantage of this method is that during the check of the correct operating position WP of the multiplexers 4a, 4b, the measurement operation of the Coriolis mass flow measuring device 2 must be stopped, which of course limits the measurement operation.

[0027] In the method 1 according to FIG. 2 and the embodiment of the Coriolis mass flow measuring device 2, something different is done. The first vibration signal s1 is phase-shifted by a phase deviation φh by means of the phase shifter 6 and the phase-shifted first vibration signal s1 is transmitted via the first multiplexer 4a (here also at least indirectly) to the control and evaluation unit 5. The control and evaluation unit 5 determines (i.e., for example calculates) the mass flow taking into account the first vibration signal st1 transmitted with a phase shift by the phase deviation φh, and thus fulfills the first task of the Coriolis mass flow measuring device 2. In the calculation shown in FIG. 2, it is again assumed for simplicity that the phase positions φ1, φ2 of the vibration signals s1, s2 are ideally maintained (in any case relative to each other) in the transmitted vibration signals st1, st2.

[0028] What is important here is that the control and evaluation unit 5 compares the vibration signal phase difference Δφ with the phase deviation φh of the first vibration signal s1, thereby detecting whether the operating position WP of the first multiplexer 4a and the operating position WP of the second multiplexer 4b are simultaneously the measurement operating position WPM (WP(M1) = WP(M2) = WPM). In FIG. 2, M1 and M2 represent the first multiplexer 4a and the second multiplexer 4b. However, different from the prior art method 1 shown in FIG. 1, this can be clearly and distinguishable performed while simultaneously performing the flow rate measurement, which is a significant improvement in operating characteristics.

[0029] The phase deviation φh that causes the phase shift of the first vibration signal s1 is selected to be significantly larger than the maximum measured phase difference that can be caused by the mass flow rate within the measurement range. In this embodiment, the phase deviation φh is selected to be 100 times larger than the maximum measured phase difference. More precisely, in the embodiment according to FIG. 2, the phase deviation φh of the first vibration signal s1 is 180°, which can be easily realized by an analog inverter.

[0030] What is actually done in the embodiment according to FIG. 2 is that when the vibration signal phase difference Δφ is within the tolerance range around the phase deviation φh of the first vibration signal s1 and within the tolerance range having the width of the maximum measured phase shift, the simultaneous measurement operating position WPM of the first multiplexer 4a and the second multiplexer 4b is detected by the control and evaluation unit 5. This ensures that phase shifts within the range of possible measurement phase shifts that may occur in some cases are tolerated.

[0031] In method 1 according to FIG. 2 and in the Coriolis mass flowmeter 2, the control and evaluation unit 5 further compares the detected operating positions WP of the first multiplexer 4a and the second multiplexer 4b (whether the first multiplexer 4a and the second multiplexer 4b are simultaneously in the measurement operating position WPM) with the preset target operating positions WPdet of the first multiplexer 4a and the second multiplexer 4b (whether the target operating position WPdet of the first multiplexer 4a and the target operating position WPdet of the second multiplexer 4b are simultaneously in the measurement operating position WPM), and signals a deviation signal fault if the detected operating position WP and the target operating position WPdet deviate from each other.

[0032] In method 1 according to FIG. 3 and in the Coriolis mass flowmeter 2, a phase deviation φh of 180° is achieved, and moreover, it is achieved very easily. Similar to the case of the embodiment of FIG. 2, the vibration sensors 3a, 3b are realized as coils. The two terminals of the coil are guided via a multiplexer 4 implemented as a dual multiplexer, and thus, in this embodiment, the vibration signal is a differential signal. For clarity, the multiplexer is not shown as an internal circuit. The first vibration sensor 3a and the second vibration sensor 3b are assembled such that the vibration signals generated by the same vibration of the measuring tube are phase-shifted by 180°. The coils are attached to the measuring tube in opposite directions, which is indicated by different signs at the coil terminals.

[0033] Equivalent solutions not shown in this figure are realized by coils as signal sensors 3a, 3b, which are attached to the measuring tube in the same direction, but are replaced compared to the connection between the terminals of the second coil as the second vibration sensor 3b and the terminals of the second multiplexer 4b, and the terminals of the first coil as the first vibration sensor 3a are connected to the terminals of the first multiplexer 4a.

Description of reference numerals

[0034] 1 Method 2 Coriolis mass flow measuring device 3a, 3b Vibration sensors 4a, 4b First multiplexer and second multiplexer 5 Control and evaluation unit 6 Phase shifter s1, s2 First vibration signal and second vibration signal φ1, φ2 Phase positions of the first vibration signal and the second vibration signal st1, st2 Transmitted first transmitted vibration signal and transmitted second vibration signal φt1, φt2 Phase positions of the transmitted first vibration signal and the transmitted second vibration signal Δφ Vibration signal phase difference WP Operating position of the multiplexer WPM Measuring operating position of the multiplexer ts Test signal WPC Changed measuring operating position of the multiplexer WPdet Target operating position of the multiplexer fault Deviation signal

Claims

1. A method (1) for operating a Coriolis mass flow measuring device (2), wherein the Coriolis mass flow measuring device (2) comprises at least one measuring tube, at least one vibration generator, at least two vibration sensors (3a, 3b), at least one first multiplexer (4a) and a second multiplexer (4b) each having a plurality of operating positions (WP), and at least one control and evaluation unit (5), wherein a medium can flow through the measuring tube, the vibration generator excites and vibrates the measuring tube, the first vibration sensor (3a) and the second vibration sensor (3b) detect the vibration of the measuring tube on the inflow side and the outflow side, and supply it as a first vibration signal (s1) and also as a second vibration signal (s2), at the measuring operating position (WPM) of the first multiplexer (4a), the first vibration signal (s1) is transmitted to the control and evaluation unit (5) at least indirectly via the first multiplexer (4a), at the measuring operating position (WPM) of the second multiplexer (4b), the second vibration signal (s2) is transmitted to the control and evaluation unit (5) at least indirectly via the second multiplexer (4b), the control and evaluation unit (5) determines the vibration signal phase difference (Δφ) between the transmitted first vibration signal (st1) and the transmitted second vibration signal (st2), and obtains the mass flow from the vibration signal phase difference (Δφ). In the method, the first vibration signal (s1) is phase-shifted by a phase deviation (φ), and the phase-shifted first vibration signal (s1) is transmitted to the control and evaluation unit (5) at least indirectly via the first multiplexer (4a), the control and evaluation unit (5) obtains the mass flow in consideration of the first vibration signal (st1) transmitted after being shifted by the phase deviation (φh), and the control and evaluation unit (5) compares the vibration signal phase difference (Δφ) with the phase deviation (φh) of the first vibration signal (s1) to detect whether the operating position (MP) of the first multiplexer (4a) and the operating position (MP) of the second multiplexer (4b) are simultaneously the measuring operating position (WPM). This is the feature of the method (1).

2. The phase deviation (φh) for phase-shifting the first vibration signal (s1) is significantly larger than the maximum measured phase difference that can be caused by the mass flow rate within the measurement range. In particular, the phase deviation (φh) is selected to be at least 10 times, particularly preferably at least 100 times larger than the maximum measured phase difference. The method (1) according to claim 1, characterized in that.

3. The phase deviation (φh) of the first vibration signal (s1) is 180°. In particular, the phase deviation (φh) is realized by an analog inverter. The method (1) according to claim 1 or 2, characterized in that.

4. By assembling or connecting the first vibration sensor (3a) and the second vibration sensor (3b) such that the vibration signals generated by the same vibration of the measurement tube are phase-shifted by 180°, the 180° phase deviation (φh) of the first vibration signal (s1) is realized. Here, the assembly or connection is particularly due to the coil as the vibration sensor (3a, 3b) being attached to the measurement tube in the opposite direction, or the coil as the vibration sensor (3a, 3b) being attached to the measurement tube in the same direction, but the terminals of the second coil as the second vibration sensor (3b) are replaced compared to the connection with the terminals of the second multiplexer (4b), and the terminals of the first coil as the first vibration sensor (3a) are connected to the terminals of the first multiplexer (4a). The method (1) according to claim 3, characterized in that.

5. When the vibration signal phase difference (Δφ) is within the tolerance range around the phase deviation (φh) of the first vibration signal (s1), in particular, within the tolerance range having the width of the maximum measured phase shift, the control and evaluation unit (5) detects the simultaneous measurement operation positions (WPM) of the first multiplexer (4a) and the second multiplexer (4b). The method (1) according to any one of claims 1 to 4, characterized in that.

6. The control and evaluation unit (5) compares the detected operating position (WP) of the first multiplexer (4a) and the second multiplexer (4b) (whether the first multiplexer (4a) and the second multiplexer (4b) are simultaneously at the measured operating position WPM) with the preset target operating position (WPdet) of the first multiplexer (4a) and the second multiplexer (4b) (whether the target operating position (WPdet) of the first multiplexer (4a) and the target operating position (WPdet) of the second multiplexer (4b) are simultaneously at the measured operating position (WPM)), and signals a deviation signal (fault) when the detected operating position (WP) deviates from the target operating position (WPdet). The method (1) according to any one of claims 1 to 5, characterized in that.

7. The deviation signal (fault) is stored as information in the memory of the control and evaluation unit (5), and / or the deviation signal (fault) is output together with a bus message via the field bus interface of the Coriolis mass flow measuring device (2), and / or the deviation signal (fault) is output together with a bus message via the diagnostic interface of the Coriolis mass flow measuring device (2) where no measurement data is output, and / or the deviation signal (fault) coded as a current value is output via the current interface of the Coriolis mass flow measuring device (2). The method (1) according to claim 6, characterized in that.

8. A Coriolis mass flow measuring device (2), comprising at least one measuring tube, at least one vibration generator, at least two vibration sensors (3a, 3b), and at least one control and evaluation unit (5), wherein a medium can flow through the measuring tube, the measuring tube is excited and vibrated by the vibration generator, the vibration of the measuring tube is detected on the inflow side and the outflow side by the first vibration sensor (3a) and the second vibration sensor (3b), and is supplied as a first vibration signal (s1) and also as a second vibration signal (s2), at the measuring operation position (WPM) of the first multiplexer (4a), the first vibration signal (s1) is transmitted to the control and evaluation unit (5) at least indirectly via the first multiplexer (4a), at the measuring operation position (WPM) of the second multiplexer (4b), the second vibration signal (s2) is transmitted to the control and evaluation unit (5) at least indirectly via the second multiplexer (4b), the control and evaluation unit (5) determines the vibration signal phase difference (Δφ) between the transmitted first vibration signal (st1) and the transmitted second vibration signal (st2), and the mass flow rate is determined from the vibration signal phase difference (Δφ). In the Coriolis mass flow measuring device (2), the first vibration signal (s1) is phase-shifted by only a phase deviation (φh), and the phase-shifted first vibration signal (s1) is transmitted to the control and evaluation unit (5) at least indirectly via the first multiplexer (4a), the control and evaluation unit (5) determines the mass flow rate taking into account the first vibration signal (st1) that is transmitted after being shifted by the phase deviation (φh), and by comparing, by the control and evaluation unit (5), the vibration signal phase difference (Δφ) with the phase deviation (φh) of the first vibration signal (s1), it is detected whether the operating position (WP) of the first multiplexer (4a) and the operating position (WP) of the second multiplexer (4b) are simultaneously at the measuring operation position (WPM). A Coriolis mass flow measuring device (2), characterized in that. Claim 9 The control and evaluation unit (5) is configured to carry out the method (1) according to any one of claims 2 to 7 during operation of the Coriolis mass flow rate measuring device (2), characterized in that, the Coriolis mass flow rate measuring device (2) according to claim 8.

10. The phase deviation (φh) is generated by the phase shifter (6), in particular, the phase deviation (φh) is 180°, and the phase shifter (6) is an analog inverter, characterized in that, the Coriolis mass flow rate measuring device (2) according to claim 8 or 9.

11. The phase deviation (φh) is 180°, and the first vibration sensor (3a) and the second vibration sensor (3b) are assembled or connected such that the vibration signal generated by the same vibration of the measuring tube is phase-shifted by 180°. The assembly or connection is in particular due to the coil as the vibration sensor (3a, 3b) being attached to the measuring tube in the opposite direction, or the coil as the vibration sensor (3a, 3b) is attached to the measuring tube in the same direction, but is replaced compared to the connection between the terminal of the second coil as the second vibration sensor (3b) and the terminal of the second multiplexer (4b), and the terminal of the first coil as the first vibration sensor (3a) is connected to the terminal of the first multiplexer (4a), characterized in that, the Coriolis mass flow rate measuring device (2) according to claim 8 or 9.

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