CORIOLIS MASS FLOWMETER

Abstract

The Coriolis mass flowmeter comprises a measuring transducer having at least one measuring tube (10), an exciter mechanism and a sensor arrangement as well as, both electrically coupled with the exciter mechanism as well as also with the sensor arrangement, an electronic transmitter circuit (ME) having a measurement- and control electronics (MCE) and a drive electronics (Exc) connected to the measuring and control electronics and/or driven by the measuring and control electronics. The measuring tube is adapted to convey a fluid measured substance flowing at least at times and during that to be caused to vibrate. Additionally, the exciter mechanism is adapted to convert electrical power supplied to it into forced mechanical power effecting mechanical oscillations of the at least one measuring tube and the sensor arrangement is adapted to register mechanical oscillations of the at least one measuring tube and to provide a first oscillation measuring signal (s1) representing, at least in part, oscillatory movements of the at least one measuring tube as well as to provide at least a second oscillation measuring signal (s2) representing, at least in part, oscillatory movements of the at least one measuring tube, in such a manner that the oscillation measuring signals follow a change of a mass flow rate of the measured substance guided in the measuring tube with a change of a phase difference, namely a change of a difference between a phase angle of the first oscillation measuring signal (s1) and a phase angle of the second oscillation measuring signal (s2). The sensor arrangement is, additionally, electrically coupled with the measuring and control electronics. The drive electronics is, in turn, electrically connected with the exciter mechanism and is adapted, in a first operating mode (I), to generate an electrical driver signal (e1) and therewith to supply electrical power to the exciter mechanism, in such a manner that the at least one measuring tube executes forced mechanical oscillations having at least one wanted frequency, namely an oscillation frequency predetermined by the electrical driver signal, and, in a second operating mode (II), to cease generating the electrical driver signal, in such a manner that then no electrical power is supplied by the drive electronics to the exciter mechanism. In the case of the Coriolis mass flowmeter of the invention, the transmitter circuit is, additionally, adapted to switch the drive electronics from the operating mode (I) into the operating mode (II), in such a manner that the at least one measuring tube in the case of drive electronics located in the operating mode (II) executes free, damped oscillations, at least during a measurement interval and the measuring and control electronics is adapted during the measurement interval to receive the oscillation measuring signals and based on their phase difference to generate mass flow, measured values representing the mass flow rate.

Claims

1. Coriolis mass flowmeter, comprising: a measuring transducer having at least one measuring tube, an exciter mechanism and a sensor arrangement; as well as, both electrically coupled with the exciter mechanism as well as also with the sensor arrangement, and especially formed by means of at least one microprocessor, an electronic transmitter circuit having a measuring and control electronics and a drive electronics connected, especially electrically, to the measuring and control electronics and/or driven by the measuring and control electronics; wherein the measuring tube is adapted to convey a fluid measured substance, especially a gas, a liquid or a dispersion, flowing at least at times and during that to be caused to vibrate; wherein the exciter mechanism is adapted to convert electrical power supplied it into mechanical power effecting forced mechanical oscillations of the at least one measuring tube; wherein the sensor arrangement is adapted to register mechanical oscillations of the at least one measuring tube and to provide a first oscillation measuring signal representing, at least in part, oscillatory movements of the at least one measuring tube as well as to provide at least a second oscillation measuring signal representing, at least in part, oscillatory movements of the at least one measuring tube, in such a manner that the first and second oscillation measuring signals follow a change of a mass flow rate of the measured substance guided in the measuring tube with a change of a phase difference, namely a change of a difference between a phase angle of the first oscillation measuring signal and a phase angle of the second oscillation measuring signal; wherein the drive electronics is electrically connected with the exciter mechanism and is adapted in a first operating mode, to generate an electrical driver signal and therewith to supply electrical power to the exciter mechanism, in such a manner that the at least one measuring tube executes forced mechanical oscillations having at least one wanted frequency, namely an oscillation frequency predetermined by the electrical driver signal, especially an oscillation frequency corresponding to a resonant frequency of the measuring transducer, and in a second operating mode, to cease generating the electrical driver signal, in such a manner that then no electrical power is supplied by the drive electronics to the exciter mechanism; wherein the measuring and control electronics is electrically coupled with the sensor arrangement; wherein the transmitter circuit, especially its measuring and control electronics and/or its drive electronics, is adapted to switch the drive electronics from the first operating mode to the second operating mode, in such a manner that the at least one measuring tube in the case of drive electronics located in the second operating mode executes free, damped oscillations, at least during a measurement interval lasting, especially, more than a reciprocal of the wanted frequency and/or longer than 10 ms; and wherein the measuring and control electronics is adapted during the measurement interval to receive and to evaluate the first and second oscillation measuring signals, namely based on their phase difference to generate mass flow, measured values (X.sub.M) representing the mass flow rate.

2. Measuring transducer as claimed in one of the preceding claims, wherein the sensor arrangement has for registering mechanical oscillations of the at least one measuring tube anespecially electrodynamic and/or located inlet sidefirst oscillation sensor (51) providing the first oscillation measuring signal as well as anespecially electrodynamic and/or located outlet side and/or embodied equally to the first oscillation sensorsecond oscillation sensor (52) providing the second oscillation measuring signal, especially except for the first and second oscillation sensors no additional oscillation sensors.

3. Measuring transducer as claimed in one of the preceding claims, wherein the exciter mechanism has an, especially electrodynamic and/or single, first oscillation exciter (41) for exciting oscillations of the at least one measuring tube.

4. Coriolis mass flowmeter as claimed in one of the preceding claims, wherein the measuring and control electronics has a first analog to digital-transducer for the first oscillation measuring signal as well as a second analog to digital-transducer for the second oscillation measuring signal.

5. Coriolis mass flowmeter as claimed in one of the preceding claims, wherein the measuring and control electronics is adapted, based on at least one of the first and second oscillation measuring signals, especially registered in the case of drive electronics operating in the first operating mode, to detect, whether the measured substance conveyed in the at least one measuring tube is inhomogeneous.

6. Coriolis mass flowmeter as claimed in one of the preceding claims, wherein the drive electronics is adapted in the first operating mode, based on at least one phase difference between the driver signal and one of the first and second oscillation measuring signals, to detect, whether the measured substance conveyed in the at least one measuring tube is inhomogeneous.

7. Coriolis mass flowmeter as claimed in one of the preceding claims, wherein the measuring and control electronics is adapted, based on a control signal placed on the transmitter circuitespecially based on a message transmitted therewith that the measured substance conveyed in the at least one measuring tube is inhomogeneous, and/or a control command transmitted therewithto bring about a switching of the drive electronics from the first operating mode to the second operating mode.

8. Coriolis mass flowmeter as claimed in one of the preceding claims, wherein the transmitter circuit, especially its measuring and control electronics and/or its drive electronics, is adapted to bring about a switching of the drive electronics from the first operating mode to the second operating mode, as soon as the measured substance conveyed in the at least one measuring tube is detected as inhomogeneous and/or reported as inhomogeneous.

9. Coriolis mass flowmeter as claimed in one of the preceding claims, wherein the transmitter circuit, especially its measuring and control electronics and/or its drive electronics, is adapted to bring about a switching of the drive electronics from the first operating mode to the second operating mode as a function of time, especially in such a manner that the switching occurs cyclically and/or that the drive electronics is operated predominantly in the first operating mode and/or that the drive electronics is operated in the first operating mode at least as long as it is operated in the second operating mode.

10. Coriolis mass flowmeter as claimed in one of the preceding claims, wherein the transmitter circuit, especially its measuring and control electronics and/or its drive electronics, is adapted to perform a switching of the drive electronics from the first operating mode to the second operating mode cyclically, especially in such a manner that the drive electronics change from the first operating mode to the second operating mode multiple times within a cycle and/or that the drive electronics is operated within a cycle predominantly in the first operating mode and/or that the drive electronics is operated within a cycle in the first operating mode at least so often and/or so long as in the second operating mode.

11. Use of a Coriolis mass flowmeter as claimed in one of the preceding claims for measuring and/or monitoring a fluid measured substance, especially a gas, a liquid or a dispersion, flowing, at least at times, in a pipeline, especially a measured substance, which is at least at times inhomogeneous and/or at least at times 2- or multiphase.

Description

[0027] The figures of the drawing show as follows:

[0028] FIG. 1 a vector diagram of signal components of oscillation measuring signals generated by means of conventional Coriolis mass flowmeters;

[0029] FIG. 2 a Coriolis mass flowmeter embodied here as a compact measuring device;

[0030] FIG. 3 schematically in the manner of a circuit diagram, a transmitter circuit, especially one suitable for a Coriolis mass flowmeter of FIG. 2, with vibration-type measuring transducer connected thereto, e.g. a Coriolis mass flowmeter of FIG. 2;

[0031] FIG. 4 a phasor-diagram for signal components of oscillation measuring signals generated by means of a Coriolis mass flowmeter of FIG. 2, or by means of a transmitter circuit of FIG. 3 connected to a vibration-type measuring transducer.

[0032] Shown in FIGS. 2 and 3 is a Coriolis mass flowmeter insertable into a process line (not shown)such as e.g. a pipeline of an industrial plant, for example, of a filling, or bottling, plant or a fueling apparatusfor measuring flowable, especially fluid or pourable, media, for example, also an inhomogeneous measured substance, which is, at least at times, two-phase or multiphase. The Coriolis mass flowmeter serves, especially, for measuring and/or monitoring a mass flow rate m, e.g., ascertaining mass flow, measured values X.sub.M representing the mass flow rate of a fluid measured substance, for example, a gas, a liquid or a dispersion, contained in the above described process line, and, at least at times, caused to flow therein. Furthermore, the Coriolis mass flowmeter can serve supplementally also to ascertain a density p and/or a viscosity of the measured substance. In an embodiment of the invention, the Coriolis mass flowmeter is used for ascertaining mass flow, measured values of a measured substance to be transferred, for example, in a predetermined, or predeterminable, amount from a supplier to a customer, for example, a measured substance in the form of a liquefied gas, such as, e.g., a methane and/or ethane and/or propane and/or butane containing, liquefied gas, or a liquefied natural gas (LNG) and even a mixture formed by means of liquid hydrocarbons, for example, petroleum or a liquid fuel. The Coriolis mass flowmeter can, accordingly, for example, also be embodied as a component of a transfer location for traffic in goods, where certification is obligatory, such as, for instance, a filling plant, and/or as a component of a transfer location in the manner of transfer locations shown in WO-A 02/060805, WO-A 2008/013545, WO-A 2010/099276, WO-A 2014/151829 or WO-A 2016/058745.

[0033] The Coriolis mass flowmeterfor example, one supplementally implemented also as a density- and/or viscosity measuring devicecomprises a physical to electrical measuring transducer MT connected via an inlet end #111 as well as an outlet end #112 to the process line. The measuring transducer MT is adapted to be flowed through during operation by the measured substance. The Coriolis mass flowmeter further comprises an electronic transmitter circuit ME (measuring electronics) electrically coupled with the measuring transducer MTespecially an electronic transmitter circuit supplied with electrical energy during operation by means of an internal energy storage and/or from the exterior via connection cable.

[0034] In advantageous manner, the, for example, also programmable and/or remotely parameterable, transmitter circuit ME, can, furthermore, be so designed that it can exchange measuringand/or other operating data, such as, for instance, current measured values or setting values serving for the control of the measuring systemand/or diagnostic values, during operation of the Coriolis mass flowmeter with an electronic data processing system superordinated thereto (not shown), for example, a programmable logic controller (PLC), a personal computer and/or a work station, via a data transmission system, for example, a fieldbus system and/or wirelessly per radio. Accordingly, the transmitter circuit ME can have, for example, an interface electronics, which is fed during operation from a (central) evaluating and supply unit provided in the above described data processing system and remote from the measuring system. For example, the transmitter circuit ME (in particular, its above-mentioned interface electronics) can be so embodied that it is electrically connectable with the external electronic data processing system via a two-conductor connection 2L, in given cases, also configured as a 4-20 mA electrical current loop, and via that can both draw from the above described evaluating- and supply unit of the data processing system the electrical power required for operation of the Coriolis mass flowmeter as well as also transfer measured values to the data processing system, for example, by (load) modulation of a direct current supplied from the evaluating and supply unit. Additionally, the transmitter circuit ME can also be so embodied that it can be operated nominally with a maximum power of 1 W or less and/or is intrinsically safe.

[0035] In the case of the measuring transducer MT, it is a vibration-type measuring transducer, namely a measuring transducer having at least one measuring tube 10, with an exciter mechanism 41 and a sensor arrangement 51, 52, wherein the at least one measuring tube 10 is adapted to convey the fluid measured substance flowing at least at times (i.e., to be flowed through by the measured substance) and during that to be caused to vibrate. The at least one measuring tube 10 can, as well as also indicated in FIG. 3 or directly evident from a combination of FIGS. 2 and 3, be accommodated together with the exciter mechanism 41 and the sensor arrangement, as well as, in given cases, additional components of the measuring transducer, within a transducer housing 100. The measuring transducer can be, for example, one known from the state of the art, not least of all one described in one of the above mentioned documents, EP-A 816 807, US-A 2002/0033043, US-A 2006/0096390, US-A 2007/0062309, US-A 2007/0119264, US-A 2008/0011101, US-A 2008/0047362, US-A 2008/0190195, US-A 2008/0250871, US-A 2010/0005887, US-A 2010/0011882, US-A 2010/0257943, US-A 2011/0161017, US-A 2011/0178738, US-A 2011/0219872, US-A 2011/0265580, US-A 2011/0271756, US-A 2012/0123705, US-A 2013/0042700, US-A 2016/0313162, US-A 2017/0261474, U.S. Pat. Nos. 4,491,009, 4,756,198, 4,777,833, 4,801,897, 4,876,898, 4,996,871, 5,009,109, 5,287,754, 5,291,792, 5,349,872, 5,705,754, 5,796,010, 5,796,011, 5,804,742, 5,831,178, 5,945,609, 5,965,824, 6,006,609, 6,092,429, 6,223,605, 6,311,136, 6,477,901, 6,505,518, 6,513,393, 6,651,513, 6,666,098, 6,711,958, 6,840,109, 6,920,798, 7,017,424, 7,040,181, 7,077,014, 7,200,503, 7,216,549, 7,296,484, 7,325,462, 7,360,451, 7,792,646, 7,954,388, 8,333,120, 8,695,436, WO-A 00/19175, WO-A 00/34748, WO-A 01/02816, WO-A 01/71291, WO-A 02/060805, WO-A 2005/093381, WO-A 2007/043996, WO-A 2008/013545, WO-A 2008/059262, WO-A 2010/099276, WO-A 2013/092104, WO-A 2014/151829, WO-A 2016/058745, WO-A 2017/069749, WO-A 2017/123214, WO-A 2017/143579, WO-A 85/05677, WO-A 88/02853, WO-A 89/00679, WO-A 94/21999, WO-A 95/03528, WO-A 95/16897, WO-A 95/29385, WO-A 98/02725, WO-A 99/40 394 or PCT/EP2017/067826, or a conventional vibration-type measuring transducer. The exciter mechanism of the measuring transducer is accordingly adapted to convert electrical power supplied to it into mechanical power effecting forced mechanical oscillations of the at least one measuring tube, while the sensor arrangement of the measuring transducer is adapted to register mechanical oscillations of the at least one measuring tube 10 and to provide a first oscillation measuring signal s1 representing at least in part oscillatory movements of the at least one measuring tube as well as at least a second oscillation measuring signal s2 representing at least in part oscillatory movements of the at least one measuring tube; this, especially, in such a manner that the oscillation measuring signals follow a change of the mass flow rate of the measured substance guided in the measuring tube with a change of at least one phase difference 12 (12*), namely a change of at least one difference between a phase angle 1 of the oscillation measuring signal s1 (or one of its spectral signal components) and a phase angle 2 of the oscillation measuring signal s2 (or one of its spectral signal components). Moreover, the oscillation measuring signals 51, s2 can have at least one signal frequency and/or signal amplitude dependent on the density and/or the viscosity of the measured substance. In an additional embodiment of the invention, the sensor arrangement of the invention includes a first oscillation sensor 51, for example, an electrodynamic or piezoelectric or capacitive first oscillation sensor 51, arranged on the inlet side of the at least one measuring tube, or applied near to it, as well as a second oscillation sensor 52, for example, and electrodynamic or piezoelectric or capacitive second oscillation sensor 52, arranged on the outlet side of the at least one measuring tube, or applied near to it. As quite usual in the case of vibration-type measuring transducers, or as also indicated in FIG. 3, the oscillation sensors 51, 52 can, for example, also be positioned, in each case, with the same separation from the half length point of the at least one measuring tube 10. Additionally, the two oscillation sensors 51, 52 can also be single oscillation sensors serving for registering oscillations of the at least one measuring tube 10, in such a manner that the sensor arrangement has except for the oscillation sensors 51, 52 no additional oscillation sensors. In an additional embodiment of the invention, the exciter mechanism is formed by means of at least one electromechanical, for example, electrodynamic, electromagnetic or piezoelectric oscillation exciter 41, which, as well as also indicated in FIG. 3, can, for example, be positioned at the half length point of the at least one measuring tube 10 and/or even be the single oscillation exciter of the exciter mechanism effecting oscillations of the at least one measuring tube, or of the measuring transducer formed therewith. Moreover, there can be provided in the measuring transducer, for example, also a temperature measuring arrangement 71 serving for registering temperatures within the tube arrangement and/or a strain measuring arrangement serving for registering mechanical stresses within the tube arrangement.

[0036] For processing the oscillation measuring signals s1, s2 delivered by the measuring transducer, the transmitter circuit ME includes, furthermore, a measurement and control electronics MCE. The measuring and control electronics MCE, as shown schematically in FIG. 3, is electrically connected with the measuring transducer MT, e.g. its sensor arrangement 51, 52, and is adapted to receive and to evaluate the above described oscillation measuring signals s1, s2, namely based on the at least two oscillation measuring signals s1, s2 to ascertain mass flow measured valuesanalog and/or digitalrepresenting the mass flow rate, in given cases, also to output such, for example, in the form of digital values. The oscillation measuring signals s1, s2 generated by the measuring transducer MT and the transmitter circuit ME, and supplied to the therein provided measuring and control electronics MCE, for example, via electrical connection lines, can, in given cases, be, firstly, preprocessed, for example, preamplified, filtered and digitized. In an additional embodiment of the invention, the measuring and control electronics MCE includes accordingly a first measuring signal input for the oscillation measuring signal s1 as well as at least a second measuring signal input for the oscillation measuring signal s2 and the measuring and control electronics MCE is, furthermore, adapted to ascertain from the oscillation measuring signals 51, s2 the above-mentioned phase difference. Additionally, the measuring and control electronics MCE can also be adapted to ascertain from at least one of the applied oscillation measuring signals 51, s2 the above-mentioned phase angle and/or at least one signal frequency and/or a signal amplitude, for example, to generate during operation, in each case, a sequence of digital phase values representing the phase angle and/or a sequence of digital frequency values representing the signal frequency and/or a sequence of digital amplitude values representing the signal amplitude. In an additional embodiment of the invention, the measuring and control electronics MCE provides a digital phase output as well as a digital amplitude output. Additionally, the measuring and control electronics MCE is, furthermore, also adapted to output on the amplitude output an amplitude sequence, namely a sequence of digital amplitude values ascertained based on at least one of the oscillation measuring signals and, for example, quantifying the signal amplitude of one of the oscillation measuring signals, and to output on the phase output a phase sequence, namely a sequence of digital phase values ascertained based on the oscillation measuring signals.

[0037] The measuring and control electronics MCE can, for example, also be implemented by means of a microcomputer provided in the transmitter circuit ME, for example, implemented by means of a digital signal processor DSP, and by means of program-code correspondingly implemented and running therein. The program-code can be stored persistently, e.g., in a non-volatile data memory EEPROM of the microcomputer and be loaded upon start of the same into a volatile data memory RAM, e.g. integrated in the microcomputer. The oscillation measuring signals s1, s2 are, such as already indicated, for processing in the microcomputer, converted by means of corresponding analog-to-digital (A/D) converters of the measuring and control electronics MCE, or the transmitter circuit ME formed therewith, into corresponding digital signals, compare, for this, for example, the above cited U.S. Pat. No. 6,311,136 or US-A 2011/0271756. Accordingly, there are provided in the measuring and control electronics according to an additional embodiment a first analog to digital converter for the first oscillation measuring signal as well as a second analog to digital converter for the second oscillation measuring signal.

[0038] For driving the measuring transducer, the transmitter circuit ME includes, as well as also schematically shown in FIG. 3 in the manner of a block diagram, furthermore, a drive electronics Exc electrically coupled both with the exciter mechanismfor example, connected with the exciter mechanism via electrical connection linesas well as also with the measuring and control electronics MCE, for example, connected, or electrically coupled via a transmitter circuit internal, digital bus. The drive electronics Exc is, especially, adapted to be operated at times in a first operating mode I and in the first operating mode I to generate a, for example, bipolar and/or at least at times periodic, in given cases, also harmonic, electrical driver signal e1 and therewith to supply electrical power to the exciter mechanism, in such a manner that the at least one measuring tube executes forced mechanical oscillations (for example, also oscillations effecting Coriolis forces in the measured substance flowing through the at least one measuring tube) with at least one wanted frequency f.sub.w, namely an oscillation frequency predetermined by the electrical driver signal e1, or a (wanted-)signal component E1 thereof, especially corresponding to a resonant frequency of the measuring transducer, or that each of the oscillation measuring signals s1, s2 contains, as well as also indicated in FIG. 4, in each case, a wanted signal component S1*, or S2*, namely a (spectral) signal component with signal frequency corresponding to the wanted frequency. The driver signal e1 can, accordingly, be, for example, a harmonic electrical signal forming the above-mentioned signal component E1 determining the wanted frequency f.sub.w, or, for example, also an electrical signal composed of a plurality of (spectral) signal components, equally as well, containing the above-mentioned signal component E1, thus a multi-frequent electrical signal, which, in given cases, can also be periodic for a predeterminable time period. For setting, or measuring, the wanted frequency f.sub.w, the drive electronics can have, such as quite usual in the case of Coriolis mass flowmeters, for example, one or more phase control loops (PLLphase locked loop). In an additional embodiment of the invention, the drive electronics Exc has a digital frequency output. Additionally, the drive electronics Exc is, furthermore, also adapted to output on the frequency output a frequency sequence, namely a sequence of digital frequency values quantifying the signal frequency set for the driver signal e1, for example, the instantaneously set, wanted frequency (i.e., the signal frequency of its signal component E1). In an additional embodiment of the invention, it is, furthermore, provided that the above-mentioned phase output of the measuring and control electronics MCE is electrically connected with a phase input formed, for example, by means of a phase comparator provided within the drive electronics Exc. The phase comparator can, for example, also be adapted to detect a phase difference between the above referenced signal component E1 of the driver signal e1 and at least one of the above described, wanted components S1*, S2* and/or to ascertain an extent of the phase difference. Moreover, the amplitude output of the measuring and control electronics MCE can additionally be electrically connected correspondingly with an amplitude input of the drive electronics Exc registering the amplitude of the signal component, or of the oscillations of the at least one measuring tube excited therewith.

[0039] The drive electronics Exc and the measuring and control electronics MCE as well as other electronic components of the transmitter circuit ME serving for the operation of the measuring system, such as, for instance, an internal power supply circuit PSC for providing internal direct voltages and/or a transmitting and receiving electronics COM serving for communication with a superordinated measurement data processor system, or an external fieldbus, as well as also directly evident from a combination of FIGS. 2 and 3, can furthermore be accommodated, for example, in a corresponding, especially impact and/or explosion resistant and/or hermetically sealed, electronics housing 200. The electronics housing 200, for example, as well as also shown in FIGS. 2 and 3, can be connected with the aforementioned transducer housing 100 to form a Coriolis mass flowmeter in compact construction. For presenting measuring device internally produced measured values and/or, in given cases, measuring system internally generated status messages, such as, for instance, a failure message or an alarm, on-site, the measuring system can have, furthermore, a display- and interaction element HMI communicating, at least at times, with the measuring and control electronics MCE, such as, for instance, an LCD, OLED or TFT display as well as a corresponding input keypad and/or a touch screen placed in the aforementioned electronics housing 200 behind a window pane correspondingly provided therein. The electrical connecting of the measuring transducer MT with the transmitter circuit ME can occur by means of corresponding electrical connection lines and corresponding electrical cable feedthroughs. The connection lines can be embodied, in such case, at least in part, as electrical cable wires surrounded, at least sectionally, with electrical insulation, e.g., in the form of twisted-pair lines, flat ribbon cables and/or coaxial cables. Alternatively thereto or in supplementation thereof, the connection lines can at least sectionally also be formed by means of conductive traces of an, especially flexible, in given cases, lacquered, printed circuit board.

[0040] The above referenced forced mechanical oscillations excited by means of exciter mechanism 41 and drive electronics Exc connected thereto can, such as quite usual in the case of Coriolis mass flowmeters, for example, be bending oscillations of the at least one measuring tube 10 around an associated rest position, wherein set as wanted frequency f.sub.w can be, for example, an instantaneous resonant frequency of a bending oscillation fundamental mode of the at least one measuring tube 10 having only a single oscillatory antinode, wherein the resonant frequency is also dependent on the density and/or the viscosity of the measured substance guided in the measuring tube. As a result of the forced oscillations of the at least one measuring tube 10, for example, the above described bending oscillations, as is known, Coriolis forces are generated in the measured substance flowing through the at least one measuring tube; this, especially, in such a manner that each of the previously indicated wanted signal components S1*, S2* of the oscillation measuring signals s1, s2 has, in each case, a measurement component S1, or S2 having a signal frequency corresponding to the wanted frequency f.sub.w and a phase angle dependent on the mass flow rate m of the measured substance flowing through the measuring transducer MT (S1=f(m), S2S1=f(m)), consequently, as well as also indicated in FIG. 4, there exists between the measuring component S1 of the oscillation signal 51 and the measuring component S2 of the oscillation signal s2 a phase difference 12 (12=f(m)) dependent on the mass flow rate m. However, it has been found that in the case of drive electronics Exc operating in the first operating mode, i.e., in the case of driver signal e1 supplied to the exciter mechanism, each of the oscillation measuring signals s1, s2, as well as also indicated in FIG. 4 or evident from a combination of FIGS. 1 and 4, can have, besides the above described measuring component St, S2, additionally, in each case, an undesired, disturbance component 51, S2 of frequency equal to that of the measuring component 51, S2, with, in each case, a phase angle dependent on the above described signal component E1 of the driver signal e1 and, in each case, likewise an amplitude dependent on the signal component E1. As also indicated in FIG. 4, the phase angle and/or the amplitude of the disturbance components S1, S2 can differ, in each case, from one another. Additionally, the phase angle and amplitude can vary during operation, for example, as a result of a changing wanted frequency and/or a changing amplitude of the signal component E1. Due to the disturbance component S1, S2 contained in the oscillation measuring signals s1, s2, and their wanted signal components S1*, S2*, a phase difference 12* actually measurable in the case of drive electronics Exc operating in the first operating mode between the wanted signal components S1*, S2* does not just depend on the mass flow rate m (12*=f(m, E1)), or, conversely, the phase difference 12* can, as well as also evident from FIG. 4, significantly deviate from the phase difference 412 between the measuring components S1, S2 (12*12).

[0041] For the purpose of eliminating the above described disturbance component S1, S2 from the oscillation measuring signals s1, s2, the drive electronics Exc of the Coriolis mass flowmeter of the invention is, consequently, furthermore, adapted during operation of the same, at times, to be operated in a second operating mode, for example, in the second operating mode II different from the above described first operating mode I and in the second operating mode to stop generating the electrical driver signal e1, in such a manner that then no electrical power is supplied from the drive electronics to the exciter mechanism; this namely, e.g., also in such a manner that the forced mechanical oscillations of the at least one measuring tube are replaced by free, damped oscillations.

[0042] Moreover, the drive electronics and/or the measuring and control electronics MCE is, furthermore, adapted, during operation of the Coriolis mass flowmeter to bring about, or at least to allow to happen, both a switching of the drive electronics Exc from the first operating mode to the second operating mode in such a manner that the at least one measuring tube 10 executes free, damped oscillations in the case of drive electronics located in the second operating mode at least during a, for example, predetermined and/or adaptable, measurement interval, as well as also, during the measurement interval, to receive and to evaluate the oscillation measuring signals s1, s2, namely based on their phase difference 12* to generate mass flow, measured values X.sub.M representing the mass flow rate m. The measurement interval therefor can, for example, be so selected that it lasts longer than 10 ms, for example, also more than 100 ms, and/or that it is greater than a reciprocal (1/f.sub.w) of the wanted frequency, for example, even more than 5-times the reciprocal. As also evident from FIG. 4, a temporary interrupting, or turning off, of the driver signal e1 can, on the one hand, indeed, lead to the fact that an amplitude (|S1|, |S2|) of each of the wanted signal components S1, S2 of the oscillation measuring signals s1, s2 received during the measurement interval can be significantly less compared with the amplitudes (|S*1|, |S*2|) of each of the wanted signal components S1*, S2* registered in the case of drive electronics Exc operating in the first operating mode I. On the other hand, this turning off of the driver signal e1 leads, especially, also to the fact that the wanted signal components S1, S2 then due to the absence of the driver signal e1 do not, or no longer, contain the above described disturbance components S1, S2 and, as a result, essentially correspond to the measuring components S1, S2, so that then the measurable phase difference 12* between the wanted signal components S1, S2, corresponds very exactly to the phase difference 12 actually required for measuring mass flow rate m (12*=12).

[0043] In an additional embodiment of the invention, the transmitter circuit, for example, its measuring and control electronics and/or its drive electronics is, furthermore, adapted to bring about, or to perform as a function of time, the switching of the drive electronics from the first operating mode to the second operating mode, for example, also in such a manner that such switching, and, conversely, a switching from the second back to the first operating mode occurs cyclically, or within a predetermined, or predeterminable, period of time, time clocked and multiple times. The measuring and control electronics and/or the drive electronics can, for example, be adapted cyclically to complete the switching of the drive electronics from the first operating mode to the second operating mode, in such a manner that the drive electronics transfers multiply within a cycle from the first operating mode to the second operating mode and vice versa and/or that the drive electronics is operated within one cycle predominantly in the first operating mode and/or that the drive electronics within a cycle is operated in the first operating mode at least so often and/or as long as in the second operating mode.

[0044] Alternatively or supplementally, the transmitter circuit can also be adapted recurringly to test during operation, whether the switching of the drive electronics from the first operating mode to the second operating mode, for instance, due to an inhomogeneous measured substance in the at least one measuring tube, is in order, or required, and, in given cases, to make the switching happen. For such purpose, according to an additional embodiment of the invention, the measuring and control electronics MCE is adapted, based on at least one of the oscillation measuring signals s1, s2, for example, an oscillation measuring signal s1, s2 registered in the case of drive electronics Exc operating in the first operating mode I, and/or the drive electronics Exc is adapted in the first operating mode I based on at least one phase difference between the driver signal e1 and one of the oscillation measuring signals s1, s2, for example, a phase difference established between the above referenced signal component E1 of the driver signal e1 and at least one of the above described wanted components S1*, S2*, and/or a controlling of the above-mentioned phase control loop of the drive electronics, to detect, whether the measured substance conveyed in the at least one measuring tube is inhomogeneous. For example, the drive electronics Exc can be adapted to compare the phase difference with a predetermined, phase difference-threshold value representing inhomogeneous measured substance and upon an exceeding of the phase difference-threshold value automatically to perform the switching into the second operating mode, in given cases, after this, also correspondingly to report such to the measuring and control electronics MCE. Other ways of using the drive electronics or the measuring and control electronics or both for determining an inhomogeneous measured substance by means of a transmitter circuit of the type being discussed, for example, based on time rate of change of the wanted frequency, the oscillation amplitude and/or a damping of the wanted oscillations, etc., are known, per se, to those skilled in the art and are disclosed in, among others, also the above mentioned US-A 2008/0011101, U.S. Pat. Nos. 6,311,136, 7,296,484, 7,040,181, WO-A 00/19175, and WO-A 01/71291. Alternatively or supplementally to the above discussed automatic detection of inhomogeneous measured substance in the at least one measuring tube, the transmitter circuit can, furthermore, also be adapted, based on a control signal applied thereto (from the exterior), to bring about a switching of the drive electronics from the first operating mode to the second operating mode. The control signal can, for example, be produced by and be sent from the above referenced data processing system connected to the Coriolis mass flowmeter and the data processing system can, for example, send a message classifying the measured substance as inhomogeneous and/or transfer to the transmitter circuit, or to the Coriolis mass flowmeter formed therewith, a control command triggering the switching from the first to the second operating mode.