DRIVER CIRCUIT, CONVERTER ELECTRONICS FORMED THEREWITH AND MEASURING SYSTEM FORMED THEREWITH

Abstract

A driver circuit comprises a signal generator having a frequency control input, an amplitude control input and a signal output, an end stage having a signal input and a load output, as well as an amplitude control with an amplitude input, an amplitude output and a voltage measurement input. The signal generator is adapted to output on its signal output an at least at times periodic, electrical, analog signal having a signal frequency predetermined by a frequency control value applied on the frequency control input and a voltage- and/or electrical current amplitude predetermined by an amplitude control value applied on the amplitude control input. The end stage is adapted to drive through an electrical circuit involving the load output a load current having an electrical current level dependent on a signal voltage and/or a signal current of an electrical input signal applied on the signal input as well as to provide on the load output a load voltage having a voltage level dependent on the electrical current level of the load current. Moreover, the amplitude control is adapted, recurringly, to ascertain an amplitude deviation between an amplitude-actual value presiding on the amplitude input and an amplitude desired value. Additionally, the amplitude control is adapted, recurringly, to ascertain an indicator value, which signals whether a magnitude of a measurement voltage applied on the voltage measurement input is too high, namely whether the magnitude of a threshold value has been exceeded, and, with application of the indicator value, to ascertain an amplitude control value, in such a manner that in the case of a too high magnitude of the measurement voltage sequentially following amplitude control values of the amplitude control sequence are lessened, as well as to output on the amplitude output an amplitude control sequence of time sequentially calculated, amplitude control values. The signal output of the signal generator is, in turn, electrically connected with the signal input of the end stage and its load output is electrically connected with the voltage measurement input of the amplitude control. Moreover, the amplitude output of the amplitude control is electrically connected with the amplitude control input of the signal generator.

Claims

1-18. (canceled)

19. A driver circuit, comprising: a signal generator, including: a frequency control input; an amplitude control input and a signal output; an end stage, especially an end stage operated by means of a bipolar direct voltage, including: a signal input and a load output; as well as an amplitude control, especially formed by means of a microprocessor, including: an amplitude input, especially a digital amplitude input; an amplitude output, especially an digital amplitude output, and a voltage measurement input, wherein: said signal generator is adapted to output on its signal output an at least at times periodic, harmonic, electrical, analog signal, said analog signal showing a signal frequency predetermined by a frequency control value, especially a digital frequency control value, applied on said frequency control input and said analog signal showing a voltage and/or electrical current amplitude predetermined by an amplitude control value, especially a digital amplitude control value, applied on said amplitude control input; said end stage is adapted to drive through an electrical circuit involving said load output a load current showing an electrical current level dependent on a signal voltage and/or a signal current of an electrical input signal applied on said signal input as well as to provide on said load output a load voltage showing a voltage level dependent on the electrical current level of the load current; said amplitude control is adapted recurringly to ascertain an amplitude deviation, namely a deviation, especially a relative or absolute deviation, between an amplitude-actual value presiding on said amplitude input and an amplitude desired value, especially one provided in the amplitude control and/or transmitted to such; said amplitude control is adapted recurringly to ascertain an indicator value which signals whether a magnitude of a measurement voltage applied on the voltage measurement input is too high, namely whether the magnitude has exceeded a threshold value, especially a threshold value provided in the amplitude control and/or transmitted to such and, with application of said indicator value, especially to ascertain a digital amplitude control value and/or an amplitude control value serving for lessening, or minimizing, the amplitude deviation, in such a manner that in the case of a too high magnitude of the measurement voltage and/or an indicator value signaling a too high magnitude of the measurement voltage sequentially following amplitude control values of the amplitude control sequence are lessened, especially also in the case of an increasing amplitude deviation and/or successively; and said amplitude control is adapted to output on the amplitude output an amplitude control sequence, namely a sequence of amplitude control values calculated timewise one after the other; and the signal output of said signal generator is electrically connected with the signal input of the end stage and the load output of the end stage is electrically connected with the voltage measurement input of the amplitude control, in such a manner that the electrical current level of the load current output from the end stage is dependent on the voltage and/or the electrical current of the electrical analog signal output from said signal generator, and the load voltage lies on the voltage measurement input of the amplitude control; and the amplitude control output of said amplitude control is electrically connected with the amplitude control input of said signal generator, in such a manner that the voltage and/or electrical current amplitude of the analog signal are/is predetermined by amplitude control values of the amplitude control sequence applied on the amplitude control input.

20. The driver circuit as claimed in claim 19, wherein: the amplitude control is adapted to ascertain a time fraction, in which the measurement voltage is during a predetermined measurement interval, as a whole, too high; and the amplitude control is adapted so to ascertain the indicator value that such quantifies the time fraction, especially relatively, i.e. with reference to the measurement interval.

21. The driver circuit as claimed in claim 19, wherein: the load voltage, thus the measurement voltage applied on the voltage measurement input of the amplitude control, has, at least at times, a periodic behavior, especially in such a manner that the load voltage and the measurement voltage changes over a time period of at least two periods with a predetermined frequency, namely, a frequency corresponding to the frequency control value.

22. The driver circuit as claimed in claim 19, wherein: the amplitude control is adapted in the case of a too high magnitude of the measurement voltage to calculate a next amplitude control value such that the amplitude control value is less than a preceding amplitude control value; and/or the amplitude control is adapted so to ascertain the indicator value that such signals whether the magnitude of the measurement voltage applied on the voltage measurement input is too low, namely, whether the magnitude has at least subceeded the threshold value; and/or the amplitude control is adapted so to calculate amplitude control values that in the case of a too low magnitude of the measurement voltage sequentially following amplitude control values of the amplitude control sequence are increased, especially successively; and/or the amplitude control is adapted to calculate an amplitude deviation weighted with the indicator value, in such a manner that the weighted amplitude deviation in the case of too high measurement voltage is less than the amplitude deviation; and/or the amplitude control is adapted to calculate an amplitude desired value weighted with the indicator value, in such a manner that the weighted amplitude desired value in the case of too high measurement voltage is less than the amplitude desired value; and/or the amplitude control is adapted to ascertain, by what amount the measurement voltage is too high, by which the measurement voltage is too high; and/or the amplitude control is adapted so to ascertain the indicator value that the indicator value quantifies an extent, by which the measurement voltage is too high.

23. The driver circuit as claimed in claim 19, wherein: the amplitude control includes a first comparator having a non-inverting voltage input and an inverting voltage input; and the voltage measurement input of the amplitude control is formed by means of the non-inverting voltage input, and wherein a first reference voltage is placed on the inverting voltage input.

24. The driver circuit as claimed in claim 23, wherein: the amplitude control includes a second comparator having a non-inverting voltage input and an inverting voltage input; the voltage measurement input of the amplitude control is formed by means of the inverting voltage input; and a second reference voltage deviating from the first reference voltage is placed on the non-inverting voltage input.

25. Transmitter electronics, comprising: a driver circuit as defined in claim 19; as well as a load circuit, especially one embodied as a component of an electro-mechanical or electro-magnetic actuator of a physical-electrical measuring transducer and/or formed by means of at least one coil; wherein the load output of the end stage is electrically connected both with the voltage measurement input of the amplitude control as well as also with the load circuit, in such a manner that the load voltage is both applied to the voltage measurement input of the amplitude control as well as also falls across the load circuit.

26. The transmitter electronics as claimed in claim 25, wherein: the load circuit includes a coil; and/or the load circuit includes a resistance element, especially one serving for limiting the load current to an electrical current level guaranteeing intrinsic safety of the load circuit and/or of the transmitter electronics.

27. The transmitter electronics as claimed in claim 25, further comprising: a two-conductor connection circuit for connecting the transmitter electronics to an evaluation and supply unit remote therefrom.

28. The transmitter electronics as claimed in claim 27, wherein: the two-conductor connection circuit is adapted to draw from the evaluation and supply unit, especially via a (4 mA to 20 mA-) electrical current loop, electrical power required for operation of the driver circuit.

29. The transmitter electronics as claimed in claim 27, wherein: the two-conductor connection circuit is adapted to transmit measurement data generated by means of the measurement and control circuit to the evaluation and supply unit, especially by modulation of an electrical current flowing in the two-conductor connection circuit and/or serving for providing electrical power for the driver circuit and/or the measurement and control circuit.

30. The transmitter electronics as claimed in claim 27, further comprising: a measurement and control circuit having: a measurement signal input, a frequency output, especially a digital frequency output; and an amplitude output, especially a digital amplitude output, wherein: the measurement circuit is adapted to ascertain from an input signal applied on the measurement signal input both a signal frequency as well as also a signal amplitude; and the measurement and control circuit is adapted to output on the amplitude output an amplitude sequence, namely a sequence of amplitude values ascertained based on the input signal, especially amplitude values quantifying the signal amplitude of the input signal and/or digital amplitude values, and on the frequency output a frequency sequence, namely a sequence of frequency values ascertained based on the input signal, especially frequency values quantifying a signal frequency to be set for the input signal and/or digital frequency values.

31. A measurement system, comprising: a transmitter electronics as defined in claim 30, as well as a measuring transducer electrically connected to said transmitter electronics and adapted to register at least one physical, measured value, especially a mass flow rate and/or a density and/or a viscosity of a fluid guided in a pipe, tube or pipeline or a fill level of a bulk good held in a container, and to transduce such into a corresponding measurement signal, in such a manner that the measurement signal follows a change of the physical, measured variable with a change of at least one signal parameter, especially a signal amplitude, a signal frequency and/or a phase angle.

32. The measuring system as claimed in claim 31, wherein: the frequency output of the measurement and control circuit is electrically connected with the frequency control input of the signal generator of the driver circuit, in such a manner that the frequency control value applied on its frequency control input corresponds to a frequency value of the frequency sequence; the amplitude output of the measurement and control circuit is electrically connected with the amplitude input of the amplitude control of the driver circuit, in such a manner that the amplitude-actual value on its amplitude input corresponds to an amplitude value of the amplitude sequence; and the measuring transducer is electrically coupled with the measurement signal input of the measurement and control circuit, in such a manner that the measurement and control circuit receives the at least one measurement signal and that both the frequency as well as also the amplitude sequence are dependent on the measurement signal.

33. The measuring system as claimed in claim 32, wherein: measurement and control circuit is adapted based on the measurement signal to ascertain measured values, especially digital measured values, representing the at least one physical measured variable; and/or the measuring transducer is coupled electrically and/or electromagnetically with the load circuit, in such a manner that behavior of the measurement signal as a function of time is dependent on behavior of the load current and/or the load voltage as a function of time; especially in such a manner that a signal frequency of the measurement signal is dependent on a frequency of the load current, or a frequency of the load voltage and/or in such a manner that a signal amplitude of the measurement signal is dependent on the electrical current level of the load current and/or the voltage level of the load voltage; and/or the measuring transducer has a measuring tube, especially a measuring tube mechanically connected with a magnet interacting with a coil of the load circuit, and wherein the measuring tube is adapted to convey a fluid measured material, especially to be flowed through by a fluid measured material and during that to be caused to vibrate; and/or the measuring transducer has a permanent magnet, especially a rod-shaped or pot shaped, permanent magnet, which interacts with a coil integrated in the load circuit.

34. The measuring system as claimed in claim 31, further comprising: an evaluation and supply unit, especially an evaluation and supply unit remote from the transmitter electronics, wherein: the transmitter electronics is connected to the evaluation and supply unit.

35. The measuring system as claimed in claim 34, wherein: the transmitter electronics draws electrical power from measurement and supply unit required for operation of the driver circuit.

36. The measuring system as claimed in claim 35, wherein: the transmitter electronics transmits measurement data generated by means of the measurement and control circuit, especially mass flow-measured values representing a mass flow rate of a medium flowing in a pipe, tube or pipeline, density-measured values representing a density of a medium, or viscosity-measured values representing a viscosity of a medium, to the evaluation and supply unit, especially by modulation of an electrical current flowing in a two-conductor connection circuit provided in the transmitter electronics.

Description

[0038] The figures of the drawing show as follows:

[0039] FIG. 1 a measuring systemhere embodied as a compact measuring devicefor media flowing in pipelines;

[0040] FIG. 2 schematically in the manner of a block diagram, an embodiment of a measuring system of FIG. 1 having a transmitter electronics and an active measuring transducer connected thereto;

[0041] FIG. 3 schematically in the manner of a block diagram, a driver circuit suitable for a transmitter electronics of FIG. 2, consequently a measuring system of FIG. 1, for an active measuring transducerhere a measuring transducer formed as a measuring transducer of vibration-type with at least one oscillating measuring tube;

[0042] FIG. 4 schematically in the manner of a block diagram, an embodiment of a driver circuit of FIG. 3; and

[0043] FIG. 5 as a function of time, a (measuring-)voltage detectable in a driver circuit of FIG. 3, or 4.

[0044] Shown in FIGS. 1 and 2 is a measuring system for flowable, especially fluid, respectively bulk good, media. The measuring system is insertable into a process line (not shown), for instance, a pipeline of an industrial plant, and formed, for example, by means of a Coriolis-mass flow measuring device, density measuring device, viscosity measuring device or the like. In the example of an embodiment shown here, the measuring system serves for measuring and/or monitoring at least one additional physical, measured variable of a medium guided in the pipeline, i.e. a medium allowed to flow, such as, for instance, a measured variable in the form of a mass flow rate, a density, a viscosity or the like. The measuring systemimplemented here by means of an inline measuring device in compact constructioncomprises a physical-electrical measuring transducer MT connected to the process line via an inlet end #111 as well as an outlet end #112. Measuring transducer MT is connected to transmitter electronics TE of the measuring system, especially a transmitter electronics supplied during operation with electrical energy from the exterior via connection cable and/or by means of internal energy storer. In an embodiment of the invention, the measurement transducer is especially adapted so to register the at least one physical, measured variable and to transduce such into the corresponding, for example, electrical, measurement signal, in such a manner that the measurement signal follows a change of the physical, measured variable with a change of at least one signal parameter, for example, a signal amplitude, a signal frequency and/or a phase angle. For such purpose, in an additional embodiment of the invention, a sensor arrangement formed, for example, by means of at least one sensor 51 or, as well as also indicated in FIG. 2, by means of an additional (second) sensor 52, for example, one embodied equally to the sensor 51, is provided in the measurement transducer. The at least one sensor 51 can be, for example, an electrodynamic oscillation sensor having, for example, at least one coil L.sub.sens for registering mechanical oscillations of the measurement transducer, such that the measurement signals s1, s2 delivered from the sensor arrangement can, accordingly, be oscillation measurement signals.

[0045] The measuring transducer MT is, moreover, an active measuring transducer correspondingly converting an electrical, for example, bipolar and/or at least at times periodic, driver signal e1, and its electrical signal powerhere delivered by the transmitter electronics TEby means of an actuator 41, for example, an electro-mechanical, electro-acoustic or electro-magnetic exciter, into a measurable effectsuch as, for instance, Coriolis forces or electrical voltages induced in the mediumserving for registering the measured variable. The measuring transducer MT can, accordingly, be, for example, a flow measuring transducer flowed through during operation correspondingly by the medium to be measured, such as, for instance, a liquid and/or a gas, such as, for instance, a measuring transducer of vibration-type having a measuring tube and adapted to convey a fluid measured material, especially to be flowed through by a fluid measured material and during that to be caused to vibrate, and having an electro-mechanical oscillation exciter acting thereon, a magneto inductive measuring transducer for conductive liquids or an ultrasonic, measuring transducer for fluids having at least one acoustic transmitter, or, however, for example, also an HF transmitting-/receiving transducer for electromagnetic microwaves, working according to the echo principle. For the case, in which the measuring transducer MT is one of vibration-type for flowing media, it is, furthermore, provided in an embodiment of the invention that the measuring transducer has at least one measuring tube 10 excited by means of the actuator 41, for example, an actuator in the form of an electrodynamic oscillation exciter and/or in the form of a plunging armature-coil arrangement (L.sub.exc), consequently thus, an inductive actuator, to execute mechanical oscillations. Serving as oscillations can be, for example, such, which have as a result of Coriolis forces in the medium flowing through the measuring transducer an oscillation form dependent on an instantaneous mass flow rate and/or a wanted frequency dependent on an instantaneous density of the medium guided in the measuring transducer and/or a damping dependent on an instantaneous viscosity of the medium guided in the measuring transducer. The measuring tube 10 can, as well as also indicated in FIG. 2, or directly evident from a combination of FIGS. 1 and 2be accommodated together with the actuator 41, and, in given cases, additional components of the measuring transducer, within a measuring transducer-housing 100.

[0046] In advantageous manner, the, especially programmable and/or remotely parameterable, transmitter electronics ME can, furthermore, be so designed that it can during operation of the measurement system exchange with an electronic data processing system (not shown), for example, a programmable logic controller (PLC), a personal computer and/or a work station, superordinated to the transmitter electronics via a data transmission system, for example, a fieldbus system and/or wirelessly per radio, measuringand/or other operating data, such as, for instance, current measured values or tuning- and/or diagnostic values serving for control of the measurement system. In such case, the transmitter electronics TE can have, for example, such a connection circuit, which during operation is fed power from a (central) evaluation- and supply unit provided in the above described data processing system remote from the measurement system. For example, the transmitter electronics TE can, in such case, furthermore, be so embodied that it is electrically connectable with the external electronic data processing system via a two-conductor connection 2L configured, for example, as a 4-20 mA-electrical current loop, and can be supplied with electrical energy thereby as well as transmit measured values to the data processing system. The transmitter electronics TE can have, furthermore, for connecting the transmitter electronics to the two-conductor connection 2L a two-conductor connection circuit, via which the transmitter electronics TE draws the electrical power required for its operation from the above described evaluation- and supply unit, for instance, in the form of a direct current supplied from the evaluation- and supply unit via a (4 mA to 20 mA-) electrical current loop and a terminal voltage corresponding therewith at an input of the two-conductor connection circuit, and via which the transmitter electronics during operation transmits generated measurement data, and -values, to the evaluation- and supply unit, for example, by (load-)modulation of the supplied direct current.

[0047] For operating the measuring transducer, the transmitter electronics TE, for example, also the intrinsically safe transmitter electronics and/or a transmitter electronics nominally operated with a maximum power of 1 W or less, includes, as shown schematically in FIGS. 2, 3, and 4 in the manner of a block diagram, furthermore, a driver circuit Exc serving especially for generating the above described driver signal e1 for operating the actuator 41. The driver circuit Exc is in an additional embodiment of the invention, furthermore, electrically connected with a load circuit LC provided in the transmitter electronics TEhere namely a load circuit formed as a component of the above described actuator 41 of a physical to electrical-measuring transducer and/or formed by means of at least one coil L.sub.exc. In an additional embodiment of the invention, as well as also indicated in FIGS. 3, and 4, in each case, a resistance element R.sub.ex-i is, furthermore, provided in the load circuit, serving especially for limiting the load current to an electrical current level guaranteeing intrinsic safety of the load circuit, and the transmitter electronics formed therewith.

[0048] The driver circuit Exc comprises, as shown schematically in FIGS. 3 and 4, a signal generator SIN, for example, one formed by means of a digital signal processor and/or by means of a digital-to-analog converter. Signal generator SIN has a frequency control input (f.sub.set), an amplitude control input (X.sub.set) and a signal output (sin.sub.exc). Signal generator SIN is adapted to output on its signal output an at least at times periodic, for example, also at least at times harmonic, electrical, analog signal u.sub.sin(t) having a signal frequency (f.sub.exc) predetermined by adigital or, in given cases, also analogfrequency control value f.sub.set applied on the frequency control input and a voltage- and/or electrical current amplitude predetermined by adigital or, in given cases, also analogamplitude control value X.sub.set applied on the amplitude control input. For the above described case, in which the measuring transducer MT is of vibration-type, the frequency control value f.sub.set can correspond (f.sub.setf.sub.exc), for example, to a mechanical resonant frequency of the at least one measuring tube 10 to be excited by means of the driver circuit Exc, and serving, consequently, as the above-mentioned wanted frequency. Furthermore, the driver circuit includes an end stage TR operated by means of a direct voltage U.sub.Tr, for example, a bipolar direct voltage, with a signal input, especially a high resistance signal input and/or a signal input having an input resistance greater than 0.5 MO, and with a load output. The direct voltage U.sub.Tr can, additionally, be, for example, also the operating- and/or reference voltage of the mentioned digital-to-analog converter of the signal generator SIN. The end stage TR is, especially, adapted to drive through an electrical circuit involving the load output a load current i.sub.e1(t) having a electrical current level dependent on a signal voltage and/or a signal current of an electrical input signal, for example, a bipolar and/or at least an at times periodic input signal, applied on the signal input, as well as to provide on the load output a load voltage u.sub.e1(t) having a voltage level dependent on the electrical current level of the load current i.sub.e1(t). In other words, end stage TR thus, serves to convert the electrical input- or even control signal applied on its signal input into a corresponding electrical output signal (e.sub.1) on the load output, namely to amplify the input signal, so that the output signal corresponding therewith, in given cases, corresponding only to an amplitude modulation of the input signal, has an electrical power, which is higher than an electrical power of the input signal but otherwise essentially corresponding to the input signal as a function of time. As evident from FIG. 3, in the case of the driver circuit of the invention, the signal input of the end stage TR is electrically connected with the signal output of the signal generator SIN, so that the electrical current level of the load current i.sub.e(t) output from the end stage is dependent on the voltage u.sub.sin(t) and/or the electrical current i.sub.sin(t) of the electrical, analog signal output from the signal generator SIN, and the analog signal output from the signal generator is amplified by means of the end stage TR and converted into the output signal output on the load output. For the case shown in FIGS. 3 and 4, in which the load output and the actuator 41 of the measuring transducer are electrically connected with one another, the output signal output on the load output can then, thus, serve as the aforementioned driver signal e1. For such purpose, in an additional embodiment of the invention, the load output of the end stage is electrically connected with the load circuit LC, in such a manner that the load voltage falls across the load circuit. The load voltage u.sub.e(t) can, for example, be so embodied that it has, at least at times, a periodic behavior, especially in such a manner that the load voltage u.sub.e(t) changes over a time period of at least two periods with a predetermined frequency (f.sub.exc), namely a frequency corresponding to the frequency control value f.sub.set. For setting the electrical current level of the load current ie(t), for example, to its peak value or to its effective value, and the voltage level of the load voltage u.sub.e(t), for example, to its peak value or to its effective value, to, in each case, correspondingly predetermined desired values, and for tuning an amplitude of the driver signal e1, the driver circuit Exc of the invention includes, furthermore, an amplitude control AMP, for example, one at least partially formed by means of the above described microprocessor and/or by means of the above described signal processorwith adigital or analogamplitude input and with adigital or analogamplitude output.

[0049] The amplitude control AMP of the driver circuit Exc of the invention is, additionally, adapted, recurringly, to ascertain an amplitude deviation X, namely arelative or absolutedeviation between an amplitude-actual value X.sub.actual presiding on the amplitude input and an amplitude desired value X.sub.NOMhere representing a nominal amplitude, namely an amplitude predetermined for a normal, undisturbed operation of the driver circuit Exc(|X.sub.ACTUALX.sub.NOM|.fwdarw.X, |X.sub.ACTUALX.sub.NOM|/X.sub.NOM.fwdarw.X). The amplitude desired value X.sub.NOM can, for example, be provided directly in the amplitude control AMP and/or, as well as also indicated in FIG. 3, be forwarded during operation from the measurement- and control circuit to the amplitude control. Moreover, the amplitude control is AMP adapted, recurringly, to ascertain an amplitude control value X.sub.exchere representing an instantaneously to be controlled, or by means of the end stage actually controllable, amplitude of the analog signal, for example, an actually controllable maximum voltage (peak value),, for example, to calculate such based on the above described amplitude deviation X, as well as to output on the amplitude output an amplitude control sequence, namely a sequence of time sequentially calculated amplitude control values. The amplitude output of the amplitude control is, in turn, electrically connected with the amplitude control input of the signal generator, in such a manner that the voltage- and/or electrical current amplitudes of the analog signal are specified by amplitude control values (X.sub.set) of the amplitude control sequence applied on the amplitude control input.

[0050] In the case of the measuring system of the invention, the above-mentioned measuring transducer MT can be coupled, for example, electrically and/or electromagneticallywith the load circuit, in such a manner that a behavior of the measurement signal as a function of time depends on the load current i.sub.e(t) and/or the load voltage as a function of time, for instance, in such a manner that a signal frequency of the measurement signal depends on a frequency of the load current, or the load voltage u.sub.e(t) and/or that a signal amplitude of the measurement signal s1 depends on the electrical current level of the load current i.sub.e(t) and/or the voltage level u.sub.e(t) of the load voltage. Particularly for the above described case, in which the measuring transducer is a measuring transducer of vibration-type, additionally, a magnet connected mechanically with the measuring tube 10 can interact with a coil L.sub.exc integrated in the load circuit LC, namely be electromagnetically coupled with such. The magnet can be, for example, especially a rod-shaped or pot shaped, permanent magnet.

[0051] For processing measurement signals delivered from the measuring transducer, the transmitter electronics of an additional embodiment of the invention includes, furthermore, a measurement- and control circuit MCC. The measurement- and control circuit MCC as shown schematically in FIG. 3 is electrically connected with measuring transducer MT, i.e. its sensor arrangement 51 (or 51, 52) and, especially, adapted based on the at least one measurement signal s1 of the measuring transducer MT during operation to ascertain measured values representing the at least one measured variable, such as e.g. a mass flow rate, and correspondingly to output such, for example, in the form of digital values. The measurement signals s1, s2 generated by the measuring transducer, for example, in each case, formed as an oscillation measurement signal, which in the case of a measuring transducer of vibration-type have, in each case, a signal component with a signal frequency corresponding to an instantaneous oscillation frequency of the at least one f.sub.exc oscillating measuring ng measuring tube, amounting for example, to between 100 Hz (=hertz) and 2 kHz, are, as well as also shown in FIG. 2, fed to the transmitter electronics TE, thus to the therein provided measurement- and control circuit MCC, where they are, firstly, preprocessed, for example, preamplified, filtered and digitized, by means of a corresponding input circuit, in order then to be able to be suitably evaluated. In an additional embodiment of the invention, measurement- and control circuit MCC includes, accordingly, at least one measurement signal input and the measurement circuit is, furthermore, adapted to ascertain from an input signal applied on the measurement signal input both a signal frequency as well as also a signal amplitude. Moreover, measurement- and control circuit MCC includes, as well as also shown in FIGS. 3 and 4, in each case, adigital or analogfrequency output as well as adigital or analogamplitude output. Additionally, the measurement- and control circuit MCC is also adapted to output on the amplitude output an amplitude sequence, namely a sequence of amplitude values X.sub.set ascertained based on the input signal, for example, amplitude values X.sub.set quantifying the signal amplitude of the input signal and/or digital amplitude values X.sub.set and on the frequency output a frequency sequence, namely a sequence of frequency values f.sub.ACTUAL ascertained based on the input signal, for example, frequency values f.sub.ACTUAL quantifying a signal frequency to be set for the input signal and/or digital frequency values f.sub.ACTUAL. In an additional embodiment of the invention, it is, furthermore, provided that the frequency output of the measurement- and control circuit MCC is electrically connected with the frequency control input of the signal generator SIN of the driver circuit Exc, in such a manner that the frequency control value F.sub.set applied on its frequency control input corresponds to a frequency value f.sub.ACTUAL of the frequency sequence. Moreover, the amplitude output of the measurement- and control circuit MCC can, additionally, be electrically connected with the amplitude input of the amplitude control AMP of the driver circuit Exc, in such a manner that the amplitude-actual value X.sub.ACTUAL present on its amplitude input corresponds to an amplitude value X.sub.ACTUAL of the amplitude sequence.

[0052] In an additional embodiment of the invention, the measuring transducer is, additionally, electrically coupled with the measurement signal input of the measurement- and control circuit, in such a manner that the measurement- and control circuit receives the at least one measurement signal and that both the frequencyas well as also the amplitude sequence depend on the measurement signal. For the above described case, in which the measuring transducer is of vibration-type, the frequency values of the frequency sequence can, such as mentioned above, correspond to an oscillation frequency of oscillations of the at least one measuring tube, in each case, to be set by means of the driver signal e1 generated by the driver circuit Exc, for example, a resonant frequency to be excited for the at least one measuring tube, and the amplitude values of the amplitude sequence can correspond to a oscillation amplitude of oscillations of the at least one measuring tube to be set, in each case, by means of the driver signal. In an additional embodiment of the invention, the measurement- and control circuit is, furthermore, adapted based on the measurement signal to ascertainanalog and/or digitalmeasured values representing the at least one physical measured variable.

[0053] In an additional embodiment of the invention, the measurement- and control circuit MCC is provided by means of a microcomputer in the transmitter electronics TE, for example, implemented by means of a digital signal processor DSP, and by means of program-code running therein. The program-code can be stored persistently e.g. in a non-volatile data memory EEPROM of the microcomputer and in the case of starting of the same be loaded into volatile data memory RAM, e.g. integrated in the microcomputer. Of course, the measurement signals are, such as just indicated, to be converted into corresponding digital signals by means of a corresponding analog-to-digital converter (A/D converter) of the transmitter electronics ME for processing in the microcomputer; compare, in this regard, for example, the above cited U.S. Pat. No. 6,311,136 or US-A 2011/0271756. The measurement- and control circuit MCC can communicate during operation besides with the measuring transducer, for example, additionally, with the driver-circuit Exc, for example, in order correspondingly to take into consideration amplitude control values (X.sub.exc) generated therewith in the case of calculating the measured values.

[0054] The driver circuit Exc and the above-mentioned measurement- and control circuit MCC as well as other electronic components of the transmitter electronics TE serving for operation of the measurement system, such as, for instance, an internal energy supply circuit VS for providing internal supply direct voltages and/or a transmitting- and receiving circuit COM serving for communication with a superordinated measurement data processing system, or over an external fieldbus, can, as well as also directly evident from a combination of FIGS. 1 and 2, for example, be accommodated in a corresponding electronics housing 200, especially an impact- and/or even explosion-resistantly and/or hermetically sealed electronics housing 200. For visualizing measuring system internally produced measured values and/or, in given cases, measuring system internally generated status reports, such as, for instance, an error report or an alarm, on-site, the measurement system can, furthermore, have a display- and servicing element HMI communicating at least at times with the measurement- and control circuit, such as, for instance, an LCD-, OLED- or TFT-display placed in the aforementioned electronics housing 200 behind a window correspondingly provided therein as well as a corresponding input keypad and/or a touch screen. The electrical connecting of the measuring transducer MT to the transmitter electronics TE can occur by means of corresponding connecting lines, for example, via electrical cable, which leads from the electronics-housing 200. The connecting lines can, in such case, be embodied, at least partially, as electrical line wires surrounded, at least sectionally, by 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 connecting lines can at least sectionally also be formed by means of conductive traces of an, especially flexible, in given cases, lacquered circuit board.

[0055] As indicated above, in the case of measuring systems of the type being discussed, not least of all also in the case of two-conductor field devices, and vibronic measuring systems, an accuracy of measurement, with which the measured values for the at least one measured variable are ascertained, can depend on whether the driver circuit operates within a predetermined working range, consequently not or, at most, only for a short time is overloaded. Especially, also those overload situations, in the case of which overdriving of the end stage occurs during measuring, are to be prevented, in order to assure that the output load current i.sub.e(t), and the output load voltage u.sub.e(t), are not distorted in comparison with the analog signal lying on the input, consequently in order to assure that the so formed driver signal e1, and the corresponding exciting of the measuring transducer, actually correspond to the specifications stored in the measurement- and control circuit and transmitted to the signal generator. For example, a course of the load voltage u.sub.e(t) corresponding to that shown in FIG. 5 as a function of time is to be prevented or should at least be allowed, as well as also indicated in FIG. 5, at most, only for a short time. For registering an impending or actually arisen overload situation of the driver circuit Exc, for example, an overdriving of the end stage TR, the amplitude control of the driver circuit of the invention includes, furthermore, an especially high resistance voltage measurement input (U.sub.M), especially one having an input resistance greater than 0.5 M (=megaohm). Additionally, the amplitude control is, especially, also adapted, recurringly, to ascertain an indicator value J, which signals whether a magnitude |u.sub.M( )|=U.sub.M of a measurement voltage u.sub.M(t) applied on the voltage measurement input is too high, namely whether the magnitude |u.sub.M(t)|=U.sub.M exceeds a predetermined threshold value U.sub.TH1 (U.sub.MU.sub.TH1). In an additional embodiment of the invention, the amplitude control AMP is, furthermore, also adapted in the case of a too high magnitude U.sub.M of the measurement voltage u.sub.M, then to calculate a next amplitude control value such that the amplitude control value is less than its preceding amplitude control value.

[0056] In another embodiment of the invention, the amplitude control is, additionally, adapted to ascertain, by what amount the measurement voltage is too high, thus, to quantify an extent, by which the measurement voltage is too high, for example, to ascertain by how much a magnitude of a voltage amplitude of the measurement voltage lies above the threshold value U.sub.TH1 and/or for how long the magnitude of the measurement voltage within a predetermined time interval lies above the threshold value U.sub.TH1, and the amplitude control is, additionally, adapted so to ascertain the indicator value J that such quantifies an extent, by which the measurement voltage, thus the load voltage u.sub.e(t), is too high. For example, as well as also indicated in FIG. 5, for the purpose of measuring the indicator value J by means of the amplitude control, a time fraction T.sub.1 can be ascertained, in which the measurement voltage u.sub.M(t), thus the load voltage u.sub.e(t), is, i.e. has been, as a whole, too high in a measurement interval T.sub.M, for example, predetermined with 20 ms (=milliseconds) and/or with greater than an oscillation period of the above described signal frequency f.sub.exc,, for example, an earlier, most recentmeasurement interval T.sub.M, and, based thereon, the indicator value J can be so generated by the amplitude control AMP that such quantifies the time fraction, for example, relativey, with reference to the measurement interval T.sub.M (T.sub.1/T.sub.M.fwdarw.J). In an additional embodiment of the invention, it is, consequently, furthermore, provided that the amplitude control AMP calculates the indicator value J based on a formula J=J.sub.maxT.sub.1/T.sub.M, i.e. that the indicator value ascertained by the amplitude control fulfills the formula, wherein J.sub.max represents an earlier established, maximum allowable value for the indicator value J, for example, corresponding to the threshold value U.sub.TH1, i.e. equivalent thereto (J.sub.maxU.sub.TH1). The above-mentioned measurement interval T.sub.M can in advantageous manner, furthermore, be so dimensioned that it fulfills a condition T.sub.Mf.sub.exc.sup.1, especially also a condition 20.Math.f.sub.exc.sup.1>T.sub.Mf.sub.exc.sup.1.

[0057] For the purpose of an as rapid as possible feedback of a load voltage detected as too high in the working range actually predetermined for the driver circuit, the amplitude control AMP can, furthermore, also be adapted to calculate a next, lower, amplitude control value as a function of the ascertained extent to which the measurement voltage u.sub.M(t) is too high, for example, in such a manner that a difference between the next amplitude control value and the preceding amplitude control value is proportional to a difference between the magnitude of the (instantaneously superelevated) measurement voltage u.sub.M(t) and the threshold value U.sub.TH1. In an additional embodiment of the invention, the amplitude control AMP is, consequently, adapted to calculate, recurringly, an amplitude desired value X.sub.LIM (X.sub.LIM=J.Math.X.sub.NOM) weighted with the (current) indicator value J and/or an amplitude deviation X.sub.LIM (X.sub.LIM=J.Math.X) weighted with the indicator value, in such a manner that the weighted amplitude desired value X.sub.LIM in the case of too high measurement voltage is less than the amplitude desired value X.sub.NOM, or that the weighted amplitude deviation X.sub.LIM in the case of too high measurement voltage u.sub.M(t) is less than the amplitude deviation X. For the above described case, in which by means of the amplitude control AMP, firstly, the weighted amplitude deviation X.sub.LIM is ascertained, the amplitude control AMP can, furthermore, also be adapted to calculate the amplitude control values based on the weighted amplitude deviation X.sub.LIM. For the purpose of calculating the amplitude control valuesbe it based on the amplitude deviation X and the indicator value J as input variables or the weighted amplitude deviation X.sub.LIMthere can be implemented in the amplitude control AMP, furthermore, a corresponding (digital-) controller, for example, with an at least partially proportional and/or at least partially integrating controller behavior (P-controller, I-controller, or PI-controller).

[0058] In an additional embodiment of the invention, the amplitude control is, furthermore, conversely, also adapted so to ascertain the indicator value that such signals whether, in given cases, the magnitude of the measurement voltage applied on the voltage measurement input is too low, namely whether the magnitude has subceeded at least the threshold value U.sub.TH1 or, in given cases, also a correspondingly predetermined, additional, (second) threshold value U.sub.TH2namely one lower in comparison with the (first) threshold value U.sub.TH1. Alternatively or supplementally, the amplitude control can, additionally, also be adapted so to calculate amplitude control values that, in the case of a too low magnitude U.sub.M of the measurement voltage u.sub.M(t), thus the load voltage u.sub.e(t), sequentially following, amplitude control values of the amplitude control sequence are increased, for example, successively increased.

[0059] The above-mentioned threshold value U.sub.TH1, and, in given cases, the likewise required threshold value U.sub.TH2, can, for example, be kept in the amplitude control, for example, in the form of a digital default value, or, as well as also indicated in FIGS. 3 and 4, be generated within the amplitude control in the form of an analog default value U.sub.TH1=|+U.sub.TRU.sub.|=|U.sub.TR+U.sub.| by means of comparators based on reference voltages (+U.sub.TRU.sub.), respectively (U.sub.TR+U.sub.) appropriately placed on corresponding reference voltage inputs. Moreover, the amplitude control AMP is, furthermore, adapted to calculate, with application of the indicator value J, an amplitude control value especially an amplitude control value serving for lessening, or minimizing, the amplitude deviation and/or a digital, amplitude control value, in such a manner that in the case of a too high magnitude U.sub.M of the measurement voltage u.sub.M(t) sequentially following amplitude control values X.sub.exc of the amplitude control sequence are, in given cases, also lessened, for example, successively, in given cases, also with a predetermined, or constant, step difference, in spite of a continuously too high, or further increasing, amplitude deviation X. As shown in FIGS. 3 and 4, in an additional embodiment of the invention, the load output of the end stage TR is electrically connected with the voltage measurement input of the amplitude control AMP, in such a manner that the load voltage u.sub.e(t) lies on the voltage measurement input of the amplitude control, thus serving as measurement voltage u.sub.M(t) to be monitored as regards magnitude (|u.sub.e(t)|.fwdarw.U.sub.M). By selecting a suitable threshold value U.sub.TH1=|+U.sub.TRU.sub.|=|U.sub.TR+U.sub.|, for example, one matched to a dynamic range of the driver circuit Exc, or of a voltage regulator for the load voltage u.sub.e(t) formed by means of the signal generator SIN, the end stage TR as well as the amplitude control AMP, or by corresponding selection of the reference voltages |+U.sub.TRU.sub.|, |U.sub.TR+U.sub.| corresponding, in given cases, to this threshold value, it can in very simple, equally as well effective manner be assured that the end stage TR, and the driver circuit Exc formed therewith, are operated as far as possible only within a stable working range, and that the end stage TR overshoots, at most, only for very short times.

[0060] In an additional embodiment of the invention, the amplitude control includes for measuring the indicator value J a first comparator COMP1 with a non inverting-voltage input (+) and with an inverting voltage input (), wherein, as well as also shown in FIG. 4the voltage measurement input of the amplitude control is formed by means of the non inverting-voltage input, and wherein a first reference voltage (+U.sub.TRU.sub.) is placed on the inverting voltage input. Moreover, the amplitude control can, additionally, have a second comparator COMP2 with a non inverting-voltage input and with an inverting voltage input, wherein the voltage measurement input of the amplitude control is also formed by means of the inverting voltage input and wherein a second reference voltage (U.sub.TR+U.sub.) differing from the first reference voltage (+U.sub.TRU.sub.) is placed on the non inverting-voltage input.