MXPA00002873A - Combined pickoff and oscillatory driver for use in coriolis flowmeters and method of operating the same - Google Patents

Abstract

An oscillatory vibration driver (104) is operably connected to a Coriolis flowmeter (10) for use in vibrating the meter flow tubes (103A and 103B). The meter electronics (20) contain a mimetic circuit (414, 802, 902) that permits use of the driver as a signal pickoff which provides a measurement of back electromotive force for use in calculating mass flow rate and density from the Coriolis flowmeter. The mimetic circuit contains an analog coil (604) and magnet (600) that facilitate the measurement of back electromotive force, or the mimetic circuit may comprise digital means (804, 806, 808, 904, 906).

Description

OSCILLATOR AND COMBINED TRANSDUCER ACTUATOR FOR USE IN CORIOLIS FLOW METERS AND METHOD TO OPERATE THE SAME FIELD OF THE INVENTION The present invention relates to the field of oscillatory vibrational actuators that are used to convert electrical energy into mechanical drive and, particularly, oscillatory actuators of the type that vibrate the flow tubes of a Coriolis flow meter for obtaining Flow measurements based on Coriolis. Even more specifically, the oscillatory actuator according to the present invention incorporates circuits that allow the oscillating actuator to be used as a signal transducer device that measures the vibrational shapes of the Coriolis flow tubes.

DECLARATION OF THE INVENTION The use of Coriolis mass flow meters is known to measure mass flow and other information for materials flowing through a conduit. Examples of Coriolis flow meters are REF .: 32907 describe in Pat. U.S. Nos. 4,109,524 of August 29, 1978, 4,491,025 of January 1, 1985 and Re. 31,450 of February 11, 1982, all by J.E. Smith et al. These flow meters have one or more flow tubes of linear or curved configuration. Each configuration of the flow tube in a Coriolis mass flow meter has a group of natural vibration shapes, which could be of a bent, torsional or coupled type. Each flow tube is driven to oscillate in resonance in one of these natural forms. The material flows into the flow meter from a conduit connected to the inlet side of the flow meter, is directed through the flow tube or tubes and exits the flow meter through the outlet side. The natural vibration forms of the vibration system, of material filling are defined in part by the combined mass of the flow tubes and the material flowing within the flow tubes.

When there is no flow through the flow meter, all points along the flow tube oscillate due to an applied driving force with identical phase or small initial fixed phase unbalance which can be corrected. As the material begins to flow, the Coriolis force causes each point along the flow tube to have a different phase. The phase on the inlet side of the flow tube delays the actuator, while the phase on the output side leads to the actuator. The transduction detectors are placed in the flow tube to produce the sinusoidal signals representative of the movement of the flow tube. The output signals of the transduction detectors are processed to determine the phase difference between the transduction detectors. The phase difference between two transduction sensing signals is proportional to the mass flow rate of the material through the flow tube.

An essential component of each Coriolis flow meter, and each vibration tube densitometer, is the drive or excitation system. The drive system operates by applying a periodic physical force to the flow tube which causes the flow tube to oscillate. The drive system includes an actuator mounted in the flow tube of the flow meter. The drive system typically contains one of many well-known arrangements, such as a magnet mounted in a conduit and a coil mounted in the other conduit in an opposite relationship with respect to the magnet. A drive circuit continuously applies a drive voltage that is typically sinusoidal or square to the actuator. Through the interaction of the continuous alternating magnetic field produced by the coil in response to the periodic drive signal and the constant magnetic field produced by the magnet, both flow conduits are initially forced to vibrate in an opposite sinusoidal pattern which is subsequently maintained . Experts in the art recognize that, any device capable of converting an electrical signal to mechanical force is appropriate for the application as an actuator. See U.S. Patent 4,777,833 filed by Carpenter and assigned in its entirety by Micro Motian, Inc. Also, a need that does not use a sinusoidal signal, but instead any periodic signal could be appropriate as the driving signal. See U.S. Patent 5,009,109 filed by Kalotay et al. and presented in its entirety by Micro Motion, Inc.

A typical mode, although not the only mode, in which the Coriolis flow meters are triggered to vibrate is the first mode of out-of-phase curvature. The first out-of-phase bending mode is the fundamental bending mode in which the two tubes of a dual-tube Coriolis flow meter vibrate in opposition to one another. However, this is not the only mode of vibration present in the vibration structure of a Coriolis flow meter that is driven in the first out-of-phase bending mode. Finally, there are hundreds of vibration modes actually excited in a Coriolis flow meter that are driven to oscillate in the first out-of-phase bending mode. In this way, a Coriolis flow meter driven to oscillate or resonate in the first out-of-phase bending mode actually has a conduit that oscillates in many other modes in addition to the first out-of-phase bending mode. Meters operated to oscillate in a different mode than the first mode of curvature out of phase, experience the same phenomenon of multiple excited modes in addition to the intended driving mode.

Existing drive systems process a feedback signal, which is typically one of the transducer sensing signals, to produce the drive signal. Unfortunately, the drive feedback signal contains the responses of other modes in addition to the desired excitation mode. In this way, the drive feedback signal is filtered through a frequency domain filter to remove unwanted components and the filtered signal is then amplified and applied to the actuator. The frequency domain filter that is used to filter the drive feedback signal is not effective to isolate the desired simple drive mode from other mode responses present in the drive feedback signal. They can be out-resonance responses from other modes that are close to the resonance frequency of the desired mode. They could also be resonant responses at frequencies that approximate the desired resonance frequency. The filtered drive feedback signal, i.e., the driving signal, typically contains the modal content at frequencies other than the desired mode for the excitation of the flow tube.

The problems that derive from the driving signal that have the modal content at multiple frequencies affect the density measurement made by a Coriolis mass flow meter. The density measurement in a Coriolis flow meter or vibrator tube densitometer depends on the measurement of the resonance frequency of the vibrating flow tube. A problem arises when the flow tube is driven in response to a drive signal that contains the modal content in multiple modes. The superposition of the multiple modes in the drive signal may result in a flow tube that is driven out of resonance from the actual resonant frequency of the desired drive mode. It may result in an error in density measurement.

Modal filtering techniques can be used to isolate and identify the vibrational modes that are of interest for calculations of the Coriolis mass flow rate and density. Modal filtering requires that additional signal transducers be attached to the vibration tubes of a Coriolis flow meter, eg, as in the serial number of co-pending application 08 / 890,785 filed on July 11, 1997, by the applicant Timothy J. Cunningham. The use of an additional signal transducer is associated with the additional cost.

Still another problem arises, where an actuator or transducer device is connected to the vibrating tube of a flow meter or Coriolis densitometer. The connection of the additional device changes the mass of the total vibration system and, consequently, it alters natural harmonic systems for vibration at different frequencies. The accuracy of the measurement obtained from the measuring system having increased mass decreases because the increased mass causes the meter to become less sensitive to small vibrational variations. Calibration to correct these differences is complicated by the fact that variations in the mass of the system also affect the location of the actuator and transducers for maximum development, meter energy consumption, bending modes and other problems that are discussed earlier.

There is a need for an actuator circuit system for a Coriolis flow meter that doubles as a signal transducer to reduce the amount of mass that is connected to the flow tubes of Coriolis DECLARATION OF THE SOLUTION The problems identified above, and others, are solved and a technical advance in the field is achieved by the drive circuit system of the present invention. The present invention provides a method and apparatus for using a signal transducer device and combined actuator to generate a flow meter drive signal or Coriolis densitometer, while signals representative of the vibrational velocity in the tubes are also received. of flow of the Coriolis meter.

A transducer device of the combined oscillatory signal and the vibrational actuator apparatus according to the present invention includes an actuator coil assembly having a coil and a magnet. The coil is capable of emanating the field effects derived from the oscillation voltage applied to the coil. A magnet is centrally disposed within "the coil for mechanical oscillation due to field effects emanating from the coil in the manner of a conventional solenoid." An impedance circuit provides a second impedance that is comparable to the first impedance when the magnet The actuator coil assembly is held stationary in the fixed positional relation to the coil, A drive voltage is applied to the actuator coil assembly and the imitator circuit.

The applied drive voltage produces a corresponding voltage in the coil of the coil assembly of the actuator and a corresponding voltage in the impedance circuit. The relative speed (i.e., the translational vibration rate) between the coil and the magnet in the actuator coil assembly is determined as a mathematical function of the difference between the coil voltage and the impedance circuit voltage. This calculation is made possible due to the relative speed between the coil and the magnet in the mounting boxes of the actuator coil as a force with the electrometer t ri z (* against EMF ") in the coil.

An "imitator circuit" is defined herein to represent a circuit that models the development of the actuator coil assembly when the actuator coil assembly is held in a fixed or stationary position, ie, when the coil and the magnet of the assembly of the actuator coil do not move in relation to each other The specific embodiments described below describe the analogous implementations and a digital implementation of the imitator circuit.

In the simplest analog case, the mimic circuit contains a coil and a magnet which, in combination, have a global impedance which is identical to that of the impedance of the actuator coil assembly. More specifically, the assembled coil and magnet of the imitator circuit have a resistance and inductance that are identical with respect to the resistance and inductance of the actuator coil assembly. While this first analogous modality works to realize the objectives of the invention, the energy consumption is excessive due to the draining through the imitative coil.

A more preferred analogous embodiment includes a magnet and coil assembly imitators having an overall impedance that differs by a scaling factor from the impedance of the actuator coil assembly. More specifically, the inductance of the imitator coil assembly and the magnet could be multiplied by a number to arrive at the inductance of the actuator coil assembly. Similarly, the mounting resistance of the imitator coil and the magnet could be multiplied by a number to reach the resistance of the drive coil assembly.

In digital mode, an analog-to-digital converter is used to apply the voltage of the drive coil to a digital filter. The digital filter models the impedance of the imitator circuit as a balance of resistance and inductance to the resistance and inductance of the drive coil assembly. In digital modes, power consumption is greatly reduced to the point of being a negligible energy consumption in the overall system of the Coriolis flow meter.

In operation, an alternate drive voltage causes a corresponding vibration in the drive coil assembly which, in turn, vibrates the flow tubes of a Coriolis flow meter according to well-established Coriolis flow measurement practices. . The relative speed between the actuator coil and the actuator magnet is approximately proportional to the force contiguous to the roller that derives from the vibrations in the Coriolis flow tubes. This force with 1 triangle voltage is opposed to the applied drive voltage. The drive voltage that a voltmeter would measure in the drive circuit, consists of the voltage drop across the resistor and the inductance of the drive coil above the direct force ect romo tri z. The transducers of the drive signals are used to measure the external force for the Coriolis flow calculations, because the back electromotive force is related to the vibration movement of the Coriolis flow tubes. According to the present invention, the component of the drive voltage due to the counter-rotating force can be isolated from the drive voltage component resulting from the resistance and the inductance of the actuator. In this way, it is possible to use an actuator as a signal transducer. The combined signal driver and transducer device is especially used in modal filtration applications and any other Coriolis mass flow rate meter or density application, because less mass must be attached to the Coriolis flow tube. The related matter of this invention involves the method and apparatus for separating the measurement of electromotive force from the applied drive voltage signal.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 represents a Coriolis flow meter of the prior art and the associated electronic meter; FIG. 2 represents a block diagram of the electronic Coriolis flow meter of the prior art; FIG. 3 represents a block diagram of a drive system for a Coriolis flow meter of the prior art; FIG. 4 represents a schematic circuit diagram of the electronic meter for use in the practice of the present invention according to a first analogous embodiment; FIG. 5 represents an assembly of the actuator coil for use according to the present invention; FIG. 6 represents a montage of the imitating coil for use according to the present invention; FIG. 7 represents a schematic circuit diagram of the electronic meter for use in the practice of the present invention according to a second analogous embodiment; FIG. 8 represents a schematic circuit diagram of a third embodiment of the present invention that includes digital electronics; FIG. 9 represents a schematic circuit diagram of a fourth embodiment of the present invention that includes all digital electronics; Y FIG. 10 depicts a process flow diagram for using an actuator coil assembly as a transducer device.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY Coriolis Flow Meter in General - FIG. 1 Figure 1 shows a Coriolis flow meter 5 which "comprises an assembly of the Coriolis meter 10 and the electronic meter 20. The electronic meter 20 is connected to the meter assembly 10 via the conductor 100 to provide the density information, mass flow rate, volumetric flow rate and total mass flow over the route 26. A structure of the Coriolis flow meter is described, although, it is apparent to those skilled in the art that the present invention could be practiced in conjunction with a densitometer of vibrating tube without the additional measurement capability provided by a Coriolis mass flow meter.

The meter assembly 10 includes a pair of flanges 101 and 101 ', manifold 102 and flow tubes 103A and 103B. The actuator 104 and the transducer detectors 105 and 105 'are connected to the flow tubes 103A and 103B. The connecting rods 106 and 106 'serve to define the axis and W near which each flow tube oscillates.

When the flow meter 10 is inserted into a pipe line system (not shown) which bears the process material being measured, the material enters the meter assembly 10 by means of the flange 101, passes through the multiple tube 102 where the material is directed to 'enter the flow tubes 103A and 103B, flows through the flow tubes 103A and 103B and returns to the manifold 102 from where it leaves the meter 10 assembly through the flange 101 '.

The flow tubes 103A and 103B are appropriately selected and mounted to the manifold 102 to have substantially the same distribution of mass, moment of inertia and modulus of elasticity near the axes of curvature -W and W'-W, respectively. The flow tubes extend outwardly from the manifold in an essentially parallel fashion.

The flow tubes 103A-103B are driven by the actuator 104 in opposite directions near their respective axes of curvature W and W and in what is called the first out-of-phase bending mode of the flow meter. The actuator 104 could comprise any of the many well-known arrangements, such as a magnet mounted to the flow tube 103A and an opposite coil mounted to the flow tube 103B and through which an alternating current is passed to vibrate both flow tubes . An appropriate actuation signal is applied by the electronic meter 20, via the conductor 110, to the actuator 104.

The electronic meter 20 receives the left and right speed signals that appear on the conductors 111 and 111 ', respectively. The electronic meter 20 produces the drive signal that appears in the conductor 110 and causes the actuator 104 to vibrate the tubes 103A and 103B. The electronic meter 20 processes the left and right speed signals to calculate the mass flow rate and the density of the material passing through the meter assembly 10. This information is applied by the electronic meter 20 on the route 26 to a medium of use (not shown).

It is known to those skilled in the art that the Coriolis 5 flow meter is very similar in structure to a vibrating tube densitometer. The vibrating tube densi also uses a vibrating tube by means of which the fluid flows or, in the case of a simple type densitometer, within which the fluid is maintained. Vibrating tube densifiers also employ a drive system to excite the flow tube to vibrate. The vibrating tube densi tors typically use only the simple feedback signal, because a density measurement requires only the measurement of the frequency and a measurement of the phase is not necessary. The descriptions of the present invention also apply here to the vibrator tube densitometers. Those skilled in the art recognize that where an existing Coriolis flow meter has two feedback signals available to introduce to a modal filter, an existing vibrator tube densitometer has only one feedback signal typically available. Thus, it is only necessary to provide additional feedback signals in a vibrating tube densitometer to apply the present invention to a vibrating tube densitometer.

Previous Art Drive System - FIGS. 2 and 3 FIG. 2 represents a block diagram of the electronic meter 20. The electronic meter 20 includes the mass flow rate circuit 30, and the drive circuit 40. The mass flow rate circuit 30 is one of many known circuits for calculating the mass flow rate of a fluid through a vibrating tube based on the phase difference between two points in the vibrating tube. The mass flow circuit 30 produces the output to a means of use (not shown) on line 26. The means of use could be, for example, a screen. The details of the mass flow rate circuit 30 are well known to those skilled in the art and do not form part of the present invention. See U.S. Patent RE31, 450 filed by Smith on November 29, 1983 and assigned in its entirety to Micro Motion, Inc. or U.S. Pat. 4,879,911 filed by Zolock on November 14, 1989 and assigned in its entirety to Micro Motion, Inc. or U.S. Pat. 5,231,884 filed by Zolock on August 3, 1993 and assigned in its entirety to Micro Motion, Inc. for exemplary information regarding the mass flow rate circuit 30. In existing drive circuit systems, the drive circuit 40 receives a feedback signal on the route 41 of the detector of the left transducer 105. As described in more detail with respect to FIG. 3, existing drive circuit systems produce a drive signal on route 104. Those skilled in the art recognize that existing drive systems could alternatively use the right transducer detector as the feedback for drive circuit 40. , some existing drive systems use the sum of both transduction signals as the feedback for the drive circuit 40.

FIG. 3 illustrates a block diagram of an existing drive circuit 40. The drive circuit 40 receives a feedback signal in the form of one of the transducer signals of the flow meter y. suitably conditions the magnitude of the transduction signal to produce a driving signal on route 110. As noted, some of the existing drive ems add up the two transduction signals and process the summed signal to produce a drive signal. The drive circuit 40 receives a signal from the transduction 105 on the route 41. The transduction signal is fed to the rectifier 300 and then to the integrator 301. The output of the integrator signal 301 represents an average amplitude of the transduction signal 105 The average amplitude signal is input to the amplitude control 302. The amplitude control 302 compares the signal of the average amplitude of the integrator 301 to a reference voltage Vref. If the average amplitude falls below the reference voltage, then the transduction signal is amplified in the multiplier 303 and a transduction signal conditioned by the amplitude leaves the multiplier 303. The transduction signal conditioned by the amplitude is amplified by the amplifier of power 304 to produce the final drive signal that is fed behind the actuator 104. In this manner, the drive circuit 40 operates to maintain a relatively constant amplitude. The details of the existing drive control circuit 40 are well known to those skilled in the art of electronic Coriolis flow meters and do not form part of the present invention. See U.S. Patent No. 5,009,109 for a more detailed discussion of the multiple embodiments of the drive circuit 40.

A Transducer and Assembly of the Combined Actuating Coil The present invention involves the changes in the electronic meter 20 which allows the actuator 104 to be used as a combined actuator 104 and the transducer 105 or 105 '(see FIG 1). Thus, one or more of the probes 105 and 105 'can be eliminated, or a third speed signal can be supplied to the electronic meter 20 in the manner of the signals traversing the lines 111 and 111' in FIG. 1.

FIG. 4 represents a schematic circuit 400 which first comprises an analogous embodiment of an internal component to the electronic meter 20 according to the present invention. The main schematic circuit components 400 include an assembly of the conventional actuator coil indicated as the actuator 104, an impedance circuit 402 having an impedance identical to the impedance of the actuator 104 and the connective lines 404 The actuator 104 is positioned on the Coriolis flow meter 10 in the same manner as shown in FIG. 1. Specifically, as represented in FIG. 5, the actuator 104 contains a cylindrical magnet 500 that is received within a central opening 502 in the coil 504. The magnet 500 is attached to the flow tube 103A for driving the flow tube 103A. The actuator coil 504 is fixed to the flow tube 103B for driving the flow tube 103B. The application of an alternate or pulsed drive voltage on line 100 to the drive coil 504 causes the magnet 500 to be reciprocal in the directions of the double headed arrow 506. The flow tubes 103A and 103B provide the source of polarization which forces the magnet 502 to a neutral position within the opening 502. In FIG. 4, the drive coil 504 is represented as a resistor R406 and an inductance L408.

FIG. 6 represents an imitator circuit 402 in greater detail. The imitator circuit 402 includes a cylindrical magnet 600, which is disposed in the central opening 602 within the coil 604. A stationary plate 606 engages with the imitating coil 604.

A stationary plate 608 is coupled to the magnet 600. The plates 606 and 608 work in opposition to one another to prevent movement between the coil 604 and the magnet 600.

In FIG. 4, an imitator circuit 402 is represented as a resistor R410 and an inductance L412. According to the embodiment of FIG. 4, R406 is identical to R410 and L408 is identical to L412.

The connecting lines 404 include the drive line 100 (see also FIG.1), the line of the imitating circuit 414 and a common supply line 416. The drive line 100 carries the voltage Va of the common supply line 416 to a current sensing resistor 418, which is used to measure ic, ie, the current in drive line 100. The voltage Va downstream of Rcs 418 is calculated as: 1) . V? - irtRf where Vd is the voltage in the drive line 100 below RC3 418 and above the drive coil 504, id is the current in line 100, RC3 is the resistivity of the resistor that senses the current Rcs 418 and Va is the voltage on the common supply line 416.

Similarly, the imitating line 414 carries the voltage Va from the common supply line 416 to a resistor that senses the current 420, which is used to measure is, ie, the current in the imitating line 414. The voltage V3 downstream of Rcs 420 is calculated as: (2) Vs = Va - isRc where Vs is the voltage in drive line 100 below RC3 420 and above drive coil 604, is the current in line 414, Va is the voltage in common supply line 416 and Rc3 is the resistivity of the resistor that detects the Rcs 420 current.

A voltage comparator 422 (e.g., a bridge of Wheatstone or similar conventional circuit) is used to determine V ,, which is the difference between the voltage on lines 100 and 414 3) V. = VHd-Vv s The current id on line 100 can be expressed mathematically as: Vd - EMF (4) = R + j? L where id is the current in drive line 100; Va is the voltage applied to the drive line 100 and the mimic line 414; EMF is the back electromotive force in coil 504 due to the movement of the magnet 500; R is the resistance R 06f of the drive coil 504 and the resistance, Rcs, of the resistor detecting the current 418; j is the square root of the negative root; ? is the frequency of the alternating or pulsed voltage Va applied to the drive line 100, and L is the inductance L40e in the drive coil 504. Equation (4) can be easily arranged to solve for the EMF, which is the desired measurement which is needed to solve a tube movement measurement according to conventional Coriolis measurement calculations. Conventional Coriolis measurement calculations do not include the ability to separate the back electromotive force from a drive signal, in the actuator 104.

Similarly, the current is on line 414 can be expressed mathematically as: . /. = R + j? L wherein i3 is the stream in the mimic line 414; Va is the voltage applied to the imitating line 414; R is the sum of the resistance R410 of the impedance coil 604 and the resistance, RC3, of the resistor detecting the current 420; j is the square root of the negative root; ? is the frequency of the alternating or pulsed voltage Va applied to the drive line 100 and is also the relative or angular velocity of the magnet 500 with respect to the drive coil 504 (see FIG. 6); and L is the inductance L41_ of the impedance coil 604 which, by design, is equal to the inductance of the drive coil L408.

Follow from the previous equations that: EMF + R. (6) V = R + j? L where Vv is defined above in equation (3), and the remaining terms are defined with reference to equation (4). Equation (6) can be solved for the EMF, which is the desired variable measured by the independent transduction mounts 105 and 105 'for the input to the mass flow rate circuit 30 in lines 111 and lllt (see FIG. ). The conventional mass flow rate circuit 30 of the electronic meter 20 (see FIG.2) is modified for purposes of the present invention to perform the calculation according to equation (6). A) Yes, the EMF calculated according to equation (6) is used, although the measurement of the EMF had originated from the transduction 105 or 105 '.

FIG. 7 represents a second analogous embodiment of the invention, that is, the schematic circuit 700. As the numbering of the schematic circuit 400 in FIG. 4 had remained where it is possible to do this with respect to the substantially identical characteristics of the schematic circuit 700 in FIG. 7. The schematic circuit 700 is identical to the schematic circuit 400, except that the impedance coil 604 has a resistance R 704 which di f i e r e of R406 as wherein SR is a scale factor for counting the difference between R704 and R406-SR is preferably a value greater than one because R704 is preferably greater than R406. The flow measurement system saves energy when R704 is greater than R 06 because the increase in resistance R704 reduces the amount of current in line imitator 414. Similarly, L408 differs from L706 as: where SR is a scale factor to count the difference between L706 and I ÜM * In the case of the schematic circuit 700, the electronic meter 20 makes the adjustments according to equations (7) and (8) to equal L408 with L70e and R408 with R704 before entering the calculations according to Equations (1) to (6).

FIG. 8 represents a schematic digital circuit 800, which operates for the same effect as the schematic circuits 400 and 700, except that the schematic circuit 800 saves even more energy than the schematic circuit 700. As the numbering of the schematic circuit 400 in FIG. 4 where it has remained where it is possible to do this with respect to the identical characteristics of the schematic circuit 800 in FIG. 8. A significant advantage of the digital implementation is that the digital impedance circuit can be easily tuned or updated adaptively to account for the change in resistance and inductance of the drive coil.

In the embodiment of FIG. 8, the line 802 carries the voltage Va to an analog-to-digital converter 804. A digital filter 806 receives from ADC 804 the digital input corresponding to Va and uses this digital input to model the same impedance as the imitative coil 604 in the mimic line 414 of FIG. 4. Digital filters are well known to those skilled in the art, and any standard or conventional variety of digital filter implementation will provide use as the 806 digital filter. A variety of digital filter texts are available to describe filter implementations conventional digital, eg, as in the book Antonieu, Di gi tal Fl lt ers: An al ysi s De si gn, McGra-Hill (1979). The digital filter 806 uses the frequency of the input voltage Va to calculate the complex impedance corresponding to the impedance coil 604 of FIG. 4, and the digital voltage output Vs with the correct amplitude and phase using conventional digital filter techniques. The digital to analog converter 808 receives the input of the digital signal Vs of the digital filter 806 and converts the signal into an analog signal consisting of the voltage Vs. The voltage comparator 422 maintains an analog voltage comparator, as in the embodiment of FIG. 4. In this way, the schematic circuit 800 comprises a mixture of digital to analog elements.

FIG. 9 represents a fourth embodiment according to the present invention, which is the most preferred embodiment, that is, the schematic circuit 900 comprising a digital mode that conserves more energy than any of the modes according to FIGS. 4, 7 or 8. The digital schematic circuit 900 operates by the same effect as the schematic circuits 400, 700, 800, except that the schematic circuit 800 saves even more energy than the other schematic circuits. As the numbering of the schematic circuit 800 in FIG. 8 it has been maintained where it is possible to do this, with respect to the identical characteristics of the schematic circuit 900 in the FlG. 9 In the embodiment of FIG. 9, line 902 carries voltage Va to analog to digital converter 804, which provides the corresponding digital output to Va. A digital filter 806 is used to model the same impedance as the impedance coil 604 in the mimic line 414 of FIG. 4. The digital filter 806 uses the frequency of the input voltage Va to calculate the complex impedance corresponding to the imitator coil 604 of FIG. 4, and outputs a digital voltage Vs that has the correct amplitude and phase. A second analog-to-digital converter 904 receives the analog voltage signal Vd from the drive line 100 downstream of Rcs 418 and converts this analog signal into a digital output. A digital voltage comparator 906 is used to calculate Vv, and provides Vv as the digital signal to electronic meter 20 on line 906.

FIG. 10 represents a schematic process diagram P1000 for using the actuator 104 as a combined actuator and the signal transducing device. FIG. 10 will be described in the context of the reference numbers corresponding to FIG. 4, but the functional discussion of FIG. 10 is equally applicable to any of the embodiments shown in FIGS. 4, 7, 8 and 9.

In step P1002, the electronic meter 20 applies an alternate or pulsed drive voltage to the line 416, which energizes the drive line 100 and the drive coil assembly 104. According to step P1004, the same voltage of drive Va is transmitted to mimic circuit 402 in mimic line 414.

In step P1006, the voltage comparator 422 determines the voltage difference Vv, and transmits this value to the electronic meter 20 for use in a calculation of the EMF according to Equation (6). The calculation of the EMF is performed in the step P1008, and the step P1010 causes a signal corresponding to the EMF to be sent to the electronic meter 20. According to the step P1012, the signal of the EMF is used to calculate the movement of the tube in the manner of a conventional transduction signal comprising the EMF according to conventional Coriolis calculations. The electronic meter 20 uses the result of the calculation of the EMF in the calculations of the Coriolis mass flow, density and the conventional drive feedback.

Those skilled in the art will recognize that the combined actuator and transduction assembly, which are described above, could be used to outperform in the modal filtration systems the processing of the vibration signals of the Coriolis flow meter. In general terms, the modal filtration analysis is used to selectively identify the vibrational modes of interest for the mass flow, density and drive frequency measurements that are obtained from the Coriolis meters. Selective identification is used to eliminate noise, such as variations that are transmitted to the flow meter from a pipeline. Additional transductions, ie, three or more translocations 105 and 105 '(see FIG 1), could be used in Coriolis flow meters to improve the specificity and selectivity of modal filtration analysis in the identification of signals of interest and the elimination of noise. However, each additional transduction can filter an additional vibrational mode that potentially adds to the problem of specified and selectivity in noise elimination. The apparatus according to the present invention advantageously avoids the problem of adding to the number of signal transductions, because the actuator also functions as a transducer.

Those skilled in the art will understand that the preferred embodiments described above could be subject to apparent modifications without departing from the scope and real spirit of the invention. The inventors, therefore, here establish their intention in relation to the Doctrine of Equivalents, to protect their total rights in the invention.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, the content of the following is claimed as property.

Claims (17)

RE I IND ICATIONS

1. An apparatus for use as a combined oscillatory signal transducer and vibrational drive transducer device, characterized in that the apparatus comprises: an actuator coil assembly that includes a coil capable of emanating field effects derived from the oscillation voltage leading to the coil, and a magne t, the assembly of the actuator coil has a first impedance; the means for positioning the magnet in operable relation with respect to the coil wherein the magnet is driven in oscillation with respect to the coil in response to the field effects emanating from the coil; an imitator circuit that provides a second impedance comparable to the first impedance when the magnet is stationary in fixed positional relation to the coil, the means for applying a drive voltage signal to the coil and the impedance circuit to produce a corresponding coil voltage and a corresponding mimic circuit voltage; Y means for calculating a counter electromotive force in the coil using the measurements obtained from at least one imitator circuit and the assembly of the drive coil.

2. The apparatus as set forth in claim 1, characterized in that the mimic circuit is an analogous circuit.

3. The apparatus as set forth in claim 2, characterized in that the analog circuit includes a stationary coil and a stationary magnet.

4. The apparatus as set forth in claim 3, characterized in that the stationary coil and the stationary magnet in combination provide the second impedance identical to the first impedance when the actuator coil assembly is limited in movement

5. The apparatus as set forth in claim 3, characterized in that the stationary coil and the stationary magnet in combination provide the second impedance which differs by a scale factor from the first impedance when the drive coil assembly is limited in movement.

6. The apparatus as established in the claim 1, characterized in that the mimic circuit is a digital circuit.

7. The apparatus as set forth in claim 6, characterized in that the digital circuit includes a digital filter.

8. The apparatus as set forth in claim 1, characterized in that the mimic circuit includes a digital filter for modeling the first impedance and an analog voltage comparator.

9. The apparatus as established in the claim 1, characterized in that the means for positioning the magnet is operable relationship with respect to the coil includes the means for mounting the coil in a first tube of Coriolis measuring means and for mounting the magnet in a second Coriolis flow tube opposite the First Coriolis flow tube.

10. The apparatus as set forth in claim 9, characterized in that the magnet is centrally disposed within the coil.

11. The apparatus as set forth in claim 1, characterized in that the means for calculating the counter electromotive force includes the means for comparing the voltage between the mounting of the driving coil and the imitating circuit. - - -

12. The apparatus as set forth in the rei indication 11, characterized in that the means for calculating the counter electromotive force includes a processor that proceeds according to the equation: T EMF + RC R + j? L where Vv is the voltage difference between the assembly of the drive coil and the imitator circuit, EMF is the counter electromotive force in the drive coil, R is the resistance of the drive coil, j is the square root of the root negative,? is the frequency of the alternating or pulsed voltage applied to the line of the drive coil and L of the drive coil.

13. A method for using a drive coil assembly to cause vibrations, while the mounting of the drive coil is used as a transducer to receive the telemetry corresponding to the vibrations, characterized in that the method comprises the steps of: applying a drive voltage to the mounting of the drive coil having a first impedance, wherein the mounting of the drive coil includes a coil and a magnet; applying the drive voltage to a mimic circuit that provides a second impedance comparable to the first impedance when the drive coil assembly is held in a stationary position; and calculate the counter electromotive force in the coil.

14. The method as set forth in claim 13, characterized in that the step of applying the drive voltage to the drive coil assembly includes a step to vibrate a pair of flow tubes in a Coriolis flow meter.

15. The method as set forth in claim 13, characterized in that the step of calculating the counter electromotive force proceeds according to an equation: EMF + Rr V = R + j? L where Vv is the voltage difference between the assembly of the drive coil and the imitator circuit, EMF is the counter electromotive force in the drive coil, R is the resistance of the drive coil, j is the square root of the root negative,? is the frequency of the alternating or pulsed voltage applied to the line of the drive coil and L of the drive coil.

16. The method as set forth in claim 13, characterized in that the step of applying the driving voltage to an imitating circuit includes applying the driving voltage to an analog mimic circuit.

17. The method as set forth in claim 13, characterized in that the step of applying the driving voltage to an imitating circuit includes applying the driving voltage to a digital mimic circuit.