HK1186240A - Method and apparatus for determining a temperature of a vibrating sensor component of a vibrating meter - Google Patents

Description

Method and device for determining the temperature of a vibrating sensor component of a vibrating meter

Technical Field

The present invention relates to a vibrating meter, and more particularly, to a method and apparatus for determining the temperature of a vibrating sensor component of a vibrating meter.

Background

Vibration sensors, such as, for example, vibrating densitometers and Coriolis (Coriolis) flow meters, are generally known and are used to measure mass flow and to measure other information for materials within a conduit. The material may be flowing or stationary. Exemplary coriolis flowmeters are disclosed in all of U.S. patent 4,109,524, U.S. patent 4,491,025, and re.31,450 to j.e. smith et al. These flow meters have one or more conduits of straight or curved configuration. Each conduit configuration in a coriolis mass flowmeter has a set of natural vibration modes that can be simple bending, torsional, or coupled. Each conduit may be driven to oscillate in a preferred mode.

Material flows into the flow meter from a connecting line on the inlet side of the flow meter, is directed through the conduit(s), and exits the flow meter via the outlet side of the flow meter. The natural vibration modes of a vibrating, material-filled system are defined in part by the combined mass of the conduit and the material flowing within the conduit.

When there is no flow through the flow meter, the driving force applied to the conduit(s) causes all points along the conduit(s) to oscillate with the same phase or small "zero offset," which is the time delay measured at zero flow. As material begins to flow through the flowmeter, coriolis forces cause each point along the conduit(s) to have a different phase. For example, the phase at the inlet end of the flow meter lags the phase at the central driver position, while the phase at the outlet precedes the phase at the central driver position. Pickup sensors on the conduit(s) generate sinusoidal signals representative of the motion of the conduit(s). The signal outputs from the pickoff sensors are processed to determine the time delay between the pickoff sensors. The time delay between two or more pickup sensors is proportional to the velocity of the mass flow of material through the conduit(s).

Meter electronics connected to the driver generates drive signals to operate the driver and determines the velocity and other properties of the mass flow of material from the signals received from the pickup sensors. The driver may comprise one of many well-known arrangements; however, magnets and opposing drive coils have met with great success in the vibrating meter industry. Examples of suitable drive coils and magnet arrangements are provided in U.S. patent 7,287,438 and U.S. patent 7,628,083, both of which are literally assigned to Micro Motion, inc. Ac power is delivered to the drive coil for vibrating the conduit(s) at the desired flow tube amplitude and frequency. It is also known in the art to provide the pick-off sensor as a magnet and coil arrangement that is very similar to the driver arrangement. However, when the driver receives a current that induces motion, the pickup sensor may induce a voltage using the motion provided by the driver. The magnitude of the time delay measured by the pickup sensor is small; typically measured in nanoseconds. Therefore, it is desirable to make the transducer output very accurate.

Fig. 1 shows an example of a prior art vibrating sensor assembly 5 in the form of a coriolis flow meter, the vibrating sensor assembly 5 including a flow meter 10 and meter electronics 20. Meter electronics 20 is connected to the flow meter 10 to measure characteristics of the flow material such as, for example, density, mass flow rate, volumetric flow rate, aggregate mass flow, temperature, and other information.

The flow meter 10 includes a pair of flanges 101 and 101', manifolds 102 and 102', and conduits 103A and 103B. Manifolds 102,102' are attached to opposite ends of conduits 103A, 103B. The flanges 101 and 101' of the prior art coriolis flowmeter are attached to opposite ends of a spacer 106. Spacers 106 maintain the spacing between manifolds 102,102' to prevent undesired vibration in conduits 103A and 103B. Conduits 103A and 103B extend outwardly from the manifold in a substantially parallel manner. When the flow meter 10 is inserted into a pipeline system (not shown) carrying a flow material, the material enters the flow meter 10 via the flange 101, passes through the inlet manifold 102 (in manifold 102, the total amount of material is directed into conduits 103A and 103B), flows through conduits 103A and 103B and back into the outlet manifold 102' (in manifold 102', the material exits the flow meter 10 via flange 101 ').

The prior art flow meter 10 includes a driver 104. For example, driver 104 is attached to conduits 103A and 103B in a position where driver 104 can vibrate conduits 103A,103B in a drive mode. More specifically, the driver 104 includes a first driver component (not shown) attached to the catheter 103A and a second driver component (not shown) attached to the catheter 103B. Driver 104 may comprise one of many well-known arrangements, such as a coil mounted to catheter 103A and an opposing magnet mounted to catheter 103B.

In the current example of a prior art coriolis flow meter, the drive mode is the first out-of-phase bending mode, and conduits 103A,103B are selected and appropriately mounted to inlet and outlet manifolds 102,102' so as to provide a balanced system having substantially the same mass distribution, moment of inertia, and elastic modulus about bending axes W-W and W ' -W ', respectively. In the example where the current drive mode is the first out of phase bending mode, conduits 103A and 103B are driven in opposite directions about their respective bending axes W-W and W '-W' by driver 104. The drive signal in the form of an alternating current may be provided by the meter electronics 20 (such as, for example, via path 110), and passed through the coil to vibrate the two conduits 103A, 103B. One of ordinary skill in the art will appreciate that other drive modes may be used with a coriolis flow meter of the prior art.

The illustrated flow meter 10 includes a pair of pickoff elements 105,105' attached to conduits 103A, 103B. More specifically, a first pick-up component (not shown) is located on conduit 103A, and a second pick-up component (not shown) is located on conduit 103B. In the depicted example, the pick-up elements 105,105' may be electromagnetic detectors, e.g., pick-up magnets and pick-up coils that generate pick-up signals indicative of the velocity and position of the conduits 103A, 103B. For example, the pick-up elements 105,105 'may provide pick-up signals to the meter electronics 20 via paths 111, 111'. Those of ordinary skill in the art will appreciate that the motion of the conduits 103A,103B is proportional to certain characteristics of the flowing material, such as the velocity and density of the mass flow of material flowing through the conduits 103A, 103B.

In the example shown in FIG. 1, the meter electronics 20 receives pickup signals from the pickup elements 105, 105'. The passageway 26 provides an input and an output that allow the one or more meter electronics 20 to interface with an operator. The meter electronics 20 measures characteristics of the flowing material such as, for example, phase difference, frequency, time delay, density, velocity of mass flow, volumetric flow rate, aggregate mass flow, temperature, meter verification, and other information. More specifically, the meter electronics 20 receives one or more signals, for example, signals from the pickup elements 105,105' and one or more temperature sensors 130.

Because of the relatively small phase delay and extremely accurate measurements that can be achieved by coriolis flowmeters, temperature measurement devices, such as Resistance Temperature Detectors (RTDs) 130, are typically used to measure the temperature of at least one of the flow conduits. Unless the temperature of the process material changes rapidly, the temperature of the flow conduit is related to the temperature of the process material and is proportional to the thermal impedance between the fluid, the RTD and the ambient temperature. Thus, if the temperature of the conduit can be measured, it can be determined that the temperature of the fluid must be within an acceptable level, which may depend on the particular application. Accordingly, prior art vibrating meters, such as the prior art coriolis flow meter 10, use the well known RTD130 to generate temperature measurements of the flow conduit. In some prior art systems, multiple measurements are made with multiple RTDs to obtain temperature measurements of the catheter, the sheath surrounding the catheter, the struts, and the like.

RTDs are widely accepted because they provide accurate temperature measurements. The RTD operates by applying power to the RTD and calculating the resistance of the RTD. This is typically done by feeding a known current through the RTD and measuring the resulting voltage to calculate the resistance. The resistance of the RTD is proportional to temperature. For example, many RTDs are made of platinum with a relatively linear temperature coefficient of resistance of approximately 0.0039/° C. Thus, the RTD may be calibrated to provide a temperature based on the determined resistance of the RTD. RTDs have the advantages of accuracy, stability, relative linearity, and a wide temperature range. However, one of the main disadvantages of using RTDs is the increased cost associated with the operation of RTDs. The increased cost is due to the signal processing of the typically lower signal levels of the RTD and the cost of the RTD itself. While the increased cost associated with RTDs may be justified in some cases, other cases do not require constant temperature measurements or greater accuracy to be provided by the RTDs. One such example is where the temperature of the process fluid remains relatively stable. No RTD may be required in this case, since the expected temperature range is relatively limited and the temperature effect is reduced compared to density or volume measurements.

Accordingly, there is a need in the art to provide a temperature measurement of at least one of the conduits of a vibrating meter using existing sensor components. That is, there is a need to provide temperature measurements without requiring additional components (e.g., RTD130 of coriolis flow meter 10 of the prior art). The present invention overcomes these and other problems and achieves an advance in the art.

Disclosure of Invention

According to an embodiment of the present invention, a method for determining a temperature of a vibrating sensor component coupled to a conduit of a vibrating meter is provided. The method comprises the steps of providing a temperature determination signal to the vibrating sensor component and measuring the resulting signal. According to an embodiment of the invention, the method further comprises the step of determining the temperature of the sensor component based on the temperature determination signal and the generated signal.

According to an embodiment of the invention, a method for generating a correlation between a voltage to current ratio and a temperature of a sensor component coupled to a conduit of a vibration sensor is provided. The method comprises the step of providing a test signal to the sensor component. The method further includes the steps of measuring the first generated signal and determining a first voltage to current ratio based on the test signal and the generated signal. According to an embodiment of the invention, the method further comprises the step of measuring a first temperature of the sensor component and storing the first determined voltage to current ratio together with the first measured temperature.

In accordance with an embodiment of the present invention, meter electronics for a vibrating meter is provided that includes one or more conduits and one or more sensor components coupled to the one or more conduits. The meter electronics includes a processing system configured to provide a temperature determination signal to a sensor component of the one or more sensor components. The processing system is also configured to measure the generated signal. According to an embodiment of the invention, the method is further configured to determine the temperature of the sensor component based on the temperature determination signal and the generated signal.

Aspect(s)

According to one aspect of the invention, a method for determining a temperature of a vibrating sensor component coupled to a conduit of a vibrating meter comprises the steps of:

providing a temperature determination signal to the vibration sensor component;

measuring the resulting signal; and

based on the temperature determination signal and the generated signal, the temperature of the sensor component is determined.

Preferably, the step of determining the temperature of the sensor component comprises:

determining a voltage to current ratio from the temperature determination signal and the measured resulting signal; and

based on the correlation between the determined voltage to current ratio and temperature, the temperature of the sensor is determined.

Preferably, the temperature determination signal comprises an alternating current at a frequency substantially equal to the resonant frequency of the conduit of the vibrating meter comprising the process fluid, and wherein the method further comprises the steps of:

removing the temperature determination signal for a predetermined time;

measuring a voltage;

determining a back electromotive force; and

the voltage to current ratio is compensated for by the back emf.

Preferably, the temperature-determining signal comprises an alternating current at a frequency different from a resonant frequency of a conduit of the vibrating meter including the process fluid.

Preferably, the temperature-determining signal comprises an alternating current at a frequency substantially equal to a resonant frequency of a conduit of the vibrating meter including the process fluid.

Preferably, the temperature determining signal comprises an alternating current and the generated signal comprises a voltage.

Preferably, the temperature determining signal comprises a fixed voltage and the generated signal comprises a current.

Preferably, the sensor component comprises a driver coil.

Preferably, the sensor component comprises a pick-off sensor coil.

According to another aspect of the invention, a method for generating a correlation between a voltage to current ratio and a temperature of a sensor component coupled to a conduit of a vibration sensor comprises the steps of:

providing a test signal to the sensor component;

measuring the first generated signal;

determining a first voltage to current ratio based on the test signal and the generated signal;

measuring a first temperature of the sensor component; and

the first determined voltage to current ratio is stored with the first measured temperature.

Preferably, the method further comprises the steps of:

measuring a second temperature of the sensor component; and

measuring a second generated signal to determine at least a second voltage to current ratio if a second temperature of the sensor component varies from the first temperature by more than a threshold amount; and

the second voltage to current ratio is stored with the second temperature.

Preferably, the sensor component comprises a driver coil.

Preferably, the sensor component comprises a pick-off sensor coil.

Preferably, the test signal comprises an alternating current and the generated signal comprises a generated voltage.

Preferably, the test signal comprises a fixed voltage and the generated signal comprises a generated current.

According to another aspect of the invention, a meter electronics for a vibrating meter including one or more conduits and one or more sensor components coupled to the one or more conduits includes a processing system configured to:

providing a temperature determination signal to a sensor component of the one or more sensor components;

measuring the resulting signal; and

the temperature of the sensor component is determined based on the temperature determination signal and the generated signal.

Preferably, the processing system is further configured to:

determining a voltage to current ratio based on the temperature determination signal and the generated signal; and

the temperature of the sensor component is determined based on a correlation between the determined voltage to current ratio and the temperature.

Preferably, the temperature-determining signal comprises an alternating current at a frequency substantially equal to a resonant frequency of a conduit of the vibrating meter including the process fluid, and wherein the processing system is further configured to:

removing the temperature determination signal for a predetermined time;

measuring a voltage;

determining a back electromotive force; and

the voltage to current ratio is compensated for by the back emf.

Preferably, the temperature-determining signal comprises an alternating current at a frequency different from a resonant frequency of a conduit of the vibrating meter including the process fluid.

Preferably, the temperature-determining signal comprises an alternating current at a frequency substantially equal to a resonant frequency of a conduit of the vibrating meter including the process fluid.

Preferably, the temperature determining signal comprises an alternating current and the generated signal comprises a voltage.

Preferably, the temperature determining signal comprises a fixed voltage and the generated signal comprises a current.

Preferably, the sensor component comprises a drive coil.

Preferably, the sensor component comprises a pick-up coil.

Drawings

Fig. 1 illustrates a prior art coriolis sensor assembly.

FIG. 2 shows a vibrating meter according to an embodiment of the invention.

FIG. 3 shows meter electronics in accordance with an embodiment of the present invention.

FIG. 4 illustrates a temperature determination routine according to an embodiment of the present invention.

Fig. 5 shows a graph of the correlation between the resistance and the temperature for the driving coil according to an embodiment of the invention.

FIG. 6 illustrates a drive signal temperature routine according to an embodiment of the present invention.

FIG. 7 illustrates a temperature dependency routine according to an embodiment of the present invention.

Detailed Description

Fig. 2-7 and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will recognize variations of these examples that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific examples described below, but only by the claims and their equivalents.

FIG. 2 shows a vibrating meter 200 in the form of a meter including a sensor assembly 210 and one or more meter electronics 220. The vibratory meter 200 may include a coriolis flow meter, positive displacementFlow meters, vibrating densitometers, and the like. Accordingly, the present invention should not be limited to coriolis flow meters. Meter electronics 220 is connected to sensor assembly 210 via leads 215 to measure one or more characteristics of the substance, such as, for example, fluid density, mass flow rate, volumetric flow rate, aggregate mass flow, temperature, and other information on pathway 226. Components that are identical to the prior art flow meter 5 share similar reference numbers, however, a heading of "2" is used instead of "1". For example, prior art catheters are labeled103A and103B, and the catheter of the invention is labeled203A and203B。

further, the driver 204 is shown as including a first portion 204A and a second portion 204B. In one exemplary embodiment, the first portion 204A includes a coil and the second portion 204B includes a magnet. First portion 204A and second portion 204B are coupled to conduit 203A and conduit 203B, respectively, according to well-known techniques such as brazing, bonding, welding, adhesives, mechanical fasteners, and the like. It should be appreciated that the first portion 204A and the second portion 204B are not limited to magnet-coil combinations, but may include other known driver systems that receive an electrical drive signal and experience a resistance that may be correlated to temperature as described below. Another example may include a piezoelectric driver system. Thus, while this description discusses the driver and pick-up coils 204A, 205' a, it should be appreciated that other types of sensor components may be used. In addition to the driver 204, which is shown as including two separate components, the pickoff sensors 205,205' are shown as including first and second portions 205A, 205B,205' a and 205' B. Similar to the driver 204, the pickoff sensors 205,205' may comprise a magnet-coil combination, wherein the coil comprises a first portion 205A,205' A and the magnet comprises a second portion 205B,205' B.

Although the vibrator 200 is shown as including two conduits 203A,203B, it should be appreciated that the vibrator 200 may include more or less than two conduits. For example, if the vibrating meter 200 includes a single conduit system, for example, the first portions 204A,205 'a of the driver and pickup element may be coupled to the conduit while the second portions 204B,205B, and 205' B may be coupled to the stationary object. Thus, the portions of the driver 204 and pick-off elements 205,205 'in communication with the meter electronics 220 via the leads 210,211,211' may be coupled to a single conduit. Further, although the conduits 203A,203BA are shown as comprising curved conduits, the vibrating meter 200 may comprise a straight conduit configuration.

The vibrating meter 200 operates in the same manner as the prior art flow meter 5, except that temperature measurements of one or more of the conduits 203A,203B are obtained. As described above, prior art vibrating meters determine temperature by coupling an RTD to a conduit and applying a current to the RTD, and measuring the resulting voltage. The resulting voltage is used with the applied current to determine the resistance of the RTD. The resistance of the RTD is then correlated to a particular temperature. As can be seen, the vibrating meter 200 of the present invention does not include an RTD. Advantageously, the costs associated with RTDs and wiring and circuitry are eliminated. However, in the case of using the vibrating meter 200 of the present invention, temperature measurements are desirable, which may be obtained by determining the temperature of one or more sensor components as described in detail below, in accordance with embodiments of the present invention. As used in this application, a "sensor component" includes a transducer for imposing vibrations on one or more of the vibrating conduits 203A,203B or for receiving vibrations from one or more of the vibrating conduits 203A, 203B. Examples of sensor components are drive coils (e.g., drive coil 204), pickup coils (e.g., pickup coils 205A,205'), photodiode pickup sensors, piezoelectric drivers, and the like. The temperature of at least one of the vibration sensor components 204A, 205' may be determined from one or more operating routines as provided by the meter electronics 220. From the temperature of the sensor components, the temperature of the conduits 203A,203B and the process fluid within the conduits 203A,203B can be determined.

FIG. 3 shows meter electronics 220 according to an embodiment of the invention. Meter electronics 220 may include an interface 301 and a processing system 303. The processing system 303 may include a storage system 304. The storage system 304 may include internal memory as shown, or alternatively, the storage system 304 may include external memory. Meter electronics 220 can generate drive signal 311 and provide drive signal 311 to driver 204, and more specifically, drive signal 311 to drive coil 204A via lead 210 shown in fig. 2. The meter electronics 220 can also generate a temperature determination signal 313 and provide the temperature determination signal 313 to the drive coil 204A. In addition, the meter electronics 220 may receive sensor signals 310 from the flow meter 210, such as signals from the pickoff sensors 205,205 'via leads 211,211' shown in FIG. 2. In some embodiments, the sensor signal 310 may be received from the driver 204. Such a configuration is known from U.S. patent 6,230,104, assigned to Micro Motion, inc. The meter electronics 220 may operate as a densitometer or may operate as a mass flow meter, including operating as a coriolis mass flow meter. It should be appreciated that meter electronics 220 may also operate as some other type of vibration sensor assembly, and the particular examples provided should not limit the scope of the present invention. The meter electronics 220 can process the sensor signal 310 to obtain one or more flow characteristics of the material flowing through the conduits 203A, 203B. In some embodiments, the meter electronics 220 may also process the sensor signal 310 to determine a voltage to current ratio (V/I) to determine a temperature of one or more of the driver 204 or the pickup elements 205,205', as discussed in detail below.

The interface 301 may receive the sensor signal 310 from the driver 204 or the pickoff sensors 205,205 'via the lead 210,211,211'. The interface 301 may perform any required or desired signal conditioning, such as formatting, amplification, buffering, etc. in any manner. Alternatively, some or all of the signal conditioning may be performed in the processing system 303. Further, interface 301 may enable communication between meter electronics 220 and external devices. The interface 301 may be capable of any manner of electronic, optical, or wireless communication.

The interface 301 in one embodiment may include a digitizer (not shown), wherein the sensor signal 310 includes an analog sensor signal. The digitizer may sample and digitize the analog sensor signal and generate a digital sensor signal. The digitizer may also perform any required decimation, wherein the digital sensor signal is decimated in order to reduce the amount of signal that needs to be processed and to reduce the processing time.

The processing system 303 may perform the operations of the meter electronics 220 and process the flow measurements from the flow meter 210. The processing system 303 may perform data processing needed to implement one or more processing routines (e.g., the temperature determination routine 313, the drive signal temperature routine 318, and the temperature correlation routine 320) as well as process the flow measurements in order to generate one or more flow characteristics that compensate for the temperature.

The processing system 303 may comprise a general purpose computer, a micro-processing system, a logic circuit, or some other general purpose processing device or a custom made processing device. The processing system 303 may be distributed among a plurality of processing devices. Processing system 303 may include any manner of integrated or stand-alone electronic storage media, such as storage system 304.

It should be understood that meter electronics 220 may include various other components and functions generally known in the art. For the sake of brevity, these additional features are omitted from the description and drawings. Therefore, the present invention should not be limited to the particular embodiments shown and discussed.

As the processing system 303 generates various flow characteristics, such as, for example, the velocity of mass flow or the velocity of volumetric flow, errors may be associated with the generated characteristics due to changes in the temperature of the process fluid, the conduits 203A,203B, or both. For example, a change in temperature of the conduit may affect a Flow Calibration Factor (FCF) of the meter, e.g., a velocity used to generate mass flow according to equation (1).

（1）

Wherein:

is the velocity of the mass flow;

FCF is flow calibration;

Δt_measuredis the measured time delay between the pickups 205, 205'; and

Δt_ois the initial time delay between pickoff elements at zero flow.

The flow calibration factor is affected by, among other things, the elastic modulus of the conduits 203A, 203B. The elastic modulus of the conduits 203A,203B varies with temperature. Thus, if the temperature of the conduits 203A,203B is not accounted for, the flow calibration factor may be inaccurate, resulting in inaccurate flow rate measurements.

As discussed above with respect to FIG. 1, in operating the vibrating meter 200, a drive signal 311, typically in the form of an alternating current, may be provided by the meter electronics 220 to energize the coils of the driver 204 via path 210. Since the resistance of the coil 204A for the driver 204 varies with temperature in a similar manner to an RTD, if the resistance (or impedance when alternating current is used) of a coil coupled to one of the conduits 203A,203B can be determined, for example, the temperature of the coil can also be determined based on a previously calculated correlation. Once the system reaches steady state, the temperature of the coil is substantially equal to the temperature of the conduits 203A, 203B. For example, steady state can be achieved quickly when the conduit is well isolated by the meter housing (not shown). Once the steady state is reached due to the temperature of the process fluid, the temperature of the conduits 203A,203B may be substantially equal to the temperature of the process fluid.

According to one embodiment, the driver 204 and lead 210 may be described as an electrical circuit that is energized by an alternating current applied in the form of the drive signal 311 and/or the temperature determination signal 313. According to ohm's law, when an alternating current is applied to the circuit, the voltage produced depends on the impedance of the circuit, in this case, the impedance of the driver coil 204A. This can be seen in equation (2).

(2)

Wherein:

v is a voltage;

r is resistance;

j is the square root of-1;

f is the frequency of the alternating current;

l is the inductance of coil 204A; and

i is the current.

Equation (2) may be rearranged to find the impedance (R +)j2πL)。

According to another embodiment of the invention, the coil may be electrically energized with direct current rather than alternating current. As can be appreciated, if direct current is used, equation (2) becomes equation (3) since the DC signal does not create any inductance.

V = RI (3)

According to another embodiment of the present invention, to simplify the calculation when applying an alternating current to the drive coil 204A, the inductive reactance term (may be omitted: (m) (m)) may be omittedj2πfL). This is acceptable when the frequency of the alternating current is relatively low, resulting in a significantly larger resistive term. For example, a typical drive signal 311 may be about 250Hz, but if the signal provided to the coil to determine temperature is reduced to about 100Hz, the inductive reactance term may be ignored. Accordingly, since impedance can generally be reduced to resistance, the remainder of this description is provided in the context of the following description unless otherwise notedEven when an AC signal is supplied, the ratio of voltage to current (V/I) is referred to as "resistance". Those skilled in the art will readily recognize that if greater accuracy is desired, the inductive reactance term may be calculated, for example, by using the known inductance L of the applied signal or based on the frequency of the AC signal and the inductance of the coil as determined during initial calibration: (j2πfL) to take into account the inductance of the coil 204A.

According to an embodiment of the invention, the temperature of at least one of the conduits 203A,203B may be determined according to one of the following methods. In the methods described below, the temperature is determined from a temperature determination signal, which may include a drive signal and a measured generation signal. According to an embodiment of the present invention, the temperature is determined according to a correlation between the V/I ratio and the temperature of the associated sensor component, rather than a correlation between the resistance of the RTD and the temperature. Advantageously, the present invention uses existing sensor components to determine temperature.

According to one embodiment of the invention, the meter electronics 220 may be configured to determine the temperature of at least one of the sensor components 204A,205A,205' according to the temperature determination routine 312.

FIG. 4 illustrates a temperature determination routine 312 according to an embodiment of the present invention. The temperature determination routine 312 begins at step 401 where a temperature determination signal 313 is provided to the sensor component. According to an embodiment of the invention, the sensor component comprises a drive coil 204A. According to another embodiment of the invention, the sensor component comprises a pick-up coil, such as pick-up coil 205A or 205' a. Thus, in some embodiments, the meter electronics 220 may be configured to both provide signals to the pickups 205,205 'and receive signals from the pickups 205, 205'. Although the temperature determination routine 312 is described as providing signals to the drive coil 204A in unison, the invention is not so limited.

According to an embodiment of the present invention, the temperature determination signal 313 is different from the drive signal 311 provided to the drive coil 204A during normal operation. However, according to other embodiments, the temperature determination signal comprises the drive signal 311. The temperature determination signal 313 may be provided to the drive coil 204A instead of or in addition to the drive signal 311. For example, the temperature determination signal 313 may be superimposed on the drive signal 311. Alternatively, if the temperature determination signal 312 is provided to one of the pickoff sensors 205,205', the drive signal 311 may still be provided to the driver 204.

According to an embodiment of the present invention, the temperature determination signal 313 comprises an alternating current having a known amplitude and frequency. However, in other embodiments, the temperature determination signal 313 may alternatively comprise a fixed voltage. According to one embodiment of the present invention, temperature-determining signal 313 comprises a frequency that is different from the resonant frequency of the fluid-filled conduit, which typically comprises the frequency of drive signal 311. Preferably, the temperature determination signal 313 is at a lower frequency than the drive signal 311; however, the temperature determination signal 313 may include a higher frequency than the drive signal 311. For example, for a U-shaped catheter as shown in FIG. 2, the drive signal 311 is typically provided at about 250Hz (for a straight catheter vibrating meter, the drive signal may approach or exceed 1000 Hz). However, according to an embodiment of the present invention, the temperature determination signal 313 may be provided at about 100 Hz.

In step 402, the resulting signal is measured. According to embodiments in which the temperature-determining signal comprises an alternating current or a direct current, the generated signal may comprise the voltage Vc across the coil 204A. For example, a voltmeter (not shown) may be used to determine the voltage Vc across the coil. The voltmeter may comprise an integral component of the meter electronics 220 or comprise an external component. Alternatively, if the temperature determination signal 313 comprises a fixed voltage, the resulting signal may comprise a current and may be measured in an ammeter, for example. In yet another embodiment, the generated signal may include a resistance, which may be determined, for example, with an ohmmeter (not shown). The voltage Vc is discussed for consistency purposes.

Based on the temperature determination signal and the generated signal, the temperature of the sensor component may be determined in step 403. According to an embodiment of the invention, the temperature of the sensor component may be determined based on the voltage to current ratio V/I. Using equation (3) above, the ratio of voltage to current can be changed to the resistance of the drive coil 204A. The V/I ratio can be changed to resistance or impedance. In either case, the V/I ratio will vary with temperature. Thus, using a look-up table, chart, graph, equation, or the like, the temperature may be correlated to the determined V/I ratio. The correlation may be stored in the storage system 304 and retrieved when needed. Thus, as shown in fig. 3, the storage system 304 may include a lookup table 315, a temperature dependency equation 316, or a graph 317. An example of a suitable correlation equation is provided in equation (4).

R = R_ref[1+α(T-T_ref)] (4)

Wherein:

r is the determined resistance;

R_refis the resistance at the reference temperature;

α is the temperature coefficient of resistance for the conductor material;

t is the temperature; and

T_refis the reference temperature.

Thus, if the reference resistance for the drive coil 204A is determined at the reference temperature during the initial calibration, equation (4) may be rearranged to solve for T based on the resistance determined in step 403. The temperature coefficient of resistance, α, of the drive coil 204A will be based on the material used for the drive coil, which is typically copper or a similar known metal or alloy. Copper has a temperature coefficient of resistance α of about 0.004/° c. As an exemplary calculation, if the drive coil 204A comprises copper, R at a reference temperature of 20 ℃_refIs determined to be 25 ohms. The measured reference voltage at 20 ℃ was 0.125 volts, given a reference resistance of 25 ohms (0.125V/.005A), with a current of 0.005A provided. If the same current of 0.005A is supplied to the drive coil 204A and 0.152 voltsWhen the voltage is measured, the resistance of the drive coil 204A increases to 30.4 ohms. Equation (4) rearranged to solve for temperature is used, so the coil temperature is 74.0 ℃. If a steady state condition has been reached, the temperature of the drive coil 204A is approximately equal to the temperature of the conduit 203B as described above, the temperature of the conduit 203B being related to the temperature of the process fluid. Accordingly, the sensor component (in this case, the drive coil 204A) may be employed to obtain a temperature measurement of the conduit 203B using the temperature determination routine 312. Furthermore, in the steady state case, the temperature of conduit 203B will be approximately equal to the temperature of the process material in the conduit, giving a good estimate of the process fluid temperature within the conduit.

As described above, temperature can also be correlated to V/I or resistance using a graph. Fig. 5 shows a graph 500 of the dependence of the coil resistance with respect to the coil temperature. Thus, in some embodiments, a temperature-determining signal may be provided to the sensor component, and the resulting signal may include a resistance determined by an ohmmeter (not shown). The ohmmeter may comprise an integral or external component of the meter electronics 220. Thus, the correlation plot 500 may provide a direct correlation between coil resistance and coil temperature as determined by an ohmmeter, without the need to determine a V/I ratio.

Another correlation may be in the form of a look-up table, as provided in table 1 below.

TABLE 1

Table 1 may be generated during an initial calibration routine in which the coil is subjected to various predetermined temperatures, for example, using an oven. The temperature may alternatively or additionally be confirmed by a temperature measurement device (e.g., RTD). Table 1 was generated using the same applied currents as described above for the equation correlations. As can be appreciated, interpolation of the determined resistance of 30.4 ohms can be usedYield 74.0 deg.CTo obtain the temperature.

Although the above examples provide a correlation between resistance and temperature, other correlations may be used. For example, a similar correlation may alternatively be provided between impedance and temperature, in order to take into account the inductive reactance term in equation (2). Thus, in some embodiments, the value of interest is the ratio of V/I and not necessarily just resistance. Thus, the look-up table or graph may include a correlation of V/I with temperature. However, if this method is used, a more accurate calibration can be obtained if the current is at the same frequency and amperage during the generation of the correlation as it is during operation to account for the inductive reactance term of equation (2) (which varies with the inductance and frequency of the coil).

In the above example, the temperature determination signal 313 includes an alternating current at a frequency different from the drive signal frequency 311. According to another embodiment of the invention, the temperature determination signal 313 conversely provides a fixed voltage to the sensor component. According to this embodiment, the current produced may be measured using an ammeter instead of the voltage in order to determine the voltage to current ratio (V/I). According to yet another embodiment, the temperature determination signal 313 may comprise a DC signal. In this embodiment, the impedance is effectively zero and does not need to be estimated or disregarded.

According to another embodiment of the invention, the meter electronics 220 may use the drive signal temperature routine 317 to determine the temperature of the drive coil 204A using the drive signal 311 instead of providing a secondary signal. In other words, the temperature determination signal 313 may include the drive signal 311.

Fig. 6 illustrates a drive signal temperature determination routine 317 according to an embodiment of the present invention. According to an embodiment of the present invention, meter electronics 220 may be configured to execute a drive signal temperature routine 317. The drive signal temperature routine 317 begins at step 601 where a temperature determination signal is provided to the drive coil 204A, in accordance with an embodiment of the present invention. According to an embodiment of the invention, the temperature determination signal may comprise a drive signal 311 provided to the drive coil 204A. According to an embodiment of the present invention, the drive signal 311 may comprise an alternating current having a known amplitude and frequency. The drive signal 311 used in the drive signal temperature routine 317 may include the same drive signal 311 used during normal operation of the vibrating meter 200. The drive signal 311 may be provided to vibrate one or more of the conduits 203A,203B at the resonant frequency of the process fluid filled conduit.

In step 602, the resulting voltage is determined as discussed above.

In step 603, the driving signal 311 is removed for a predetermined time. Since drive signal 311 is provided at the resonant frequency of the fluid-filled conduit, drive signal 311 drops to zero. Thus, the conduits 203A,203B vibrate at a resonant frequency due to the drive signal 311 provided to the drive coil 204A. As a result, the measured voltage Vc is affected by the drive signal current, the resistance across the drive coil, the inductance of the drive coil, and the back electromotive force (EMF), which is the voltage opposite to the current provided in equation (5).

(5)

Wherein:

vc is voltage;

i is current;

r is resistance;

j is the square root of-1;

f is the driving signal frequency; and

l is the drive coil inductance.

Since the catheter vibrates at resonance, a back EMF is present. Thus, if the drive signal 311 is temporarily removed, R, L and I drop to zero.

In step 604, the voltage across the drive coil 204A may again be determined. The voltage Vc may be determined in step 402 in a similar manner as described above. With the drive signal 311 temporarily removed and the voltage measured again, the back EMF can be determined in step 605. Where the back EMF is determined, the loss due to the back EMF can be compensated for using the V/I ratio of the voltage determined in step 602 to determine the resistance of the coil. For example, the correlation between the ratio of V/I and temperature may not include back EMF. Thus, the back EMF can be subtracted from the V/I ratio to obtain the correct V/I ratio to use with correlation.

In step 606, the resistance of the drive coil 204A is determined. More precisely, the ratio of V/I is determined. As with the previously described embodiments, although "resistance" is described, if the inductance L of the drive coil is known, then impedance may be calculated instead of resistance.

In step 607, the temperature of the drive coil 204A may be determined as described above.

In the embodiments discussed above, the correlation between V/I and temperature, or some variation thereof, is predetermined. However, it may be desirable to update or perform the initial correlation on the vibrating meter in accordance with the correlation routine 320 described below.

FIG. 7 illustrates a relevance routine 320 according to an embodiment of the invention. For example, the correlation routine 320 may be executed by the meter electronics 220. The correlation routine 330 may be performed by a user or operator. The correlation routine 330 may be performed by the manufacturer. The correlation routine 320 may be executed to generate a correlation between the ratio of V/I and the temperature of the sensor components of the one or more vibrating meters. For example, the correlation routine 320 may be executed to generate a correlation between the resistance of the drive coil 204A and the temperature of the drive coil 204A.

The correlation routine 320 begins at step 701, where a test signal is provided to the sensor component, in which case the driver coil 204A is envisioned. For example, the test signal may comprise an alternating current. Alternatively, the test signal may comprise a fixed voltage or direct current.

In step 702, a first generated signal is measured. Where the test signal comprises alternating current, the generated signal may comprise a voltage. Alternatively, if a fixed voltage is provided as the test signal, the resulting signal may comprise the measured current.

In step 703, a first V/I ratio is determined based on the test signal and the first generated signal. In some embodiments, the ratio of V/I may include the resistance of the sensor component. In other embodiments, the ratio of V/I may include the impedance of the sensor component. In still other embodiments, the ratio of V/I may include a combination of resistance and/or impedance and/or back EMF.

In step 704, a first temperature is measured. The temperature may be measured, for example, from a temperature measuring device, such as an RTD or thermocouple. The temperature measurement device may be coupled to or positioned adjacent to the sensor component. In some embodiments, the correlation routine 320 may occur when a steady state has been reached such that the temperature of the temperature measurement device includes the temperature of the sensor component. The temperature can also be ensured by calibration in an oven.

In step 705, the first V/I ratio is stored with the first measured temperature.

In step 706, the temperature is measured again to obtain a second temperature measurement. If the second temperature differs from the first measured temperature by more than the threshold amount, the correlation routine 320 may return to step 702 where a second generated signal is determined. If the second temperature is the same as the previously measured temperature, or within a threshold difference, the correlation routine 320 may be terminated. The temperature of the system can be varied to obtain a correlation between the plurality of V/I ratios and the temperature. The plurality of correlations may be stored in a variety of ways including tables, graphs, equations, etc., and retrieved during use to determine the temperature of the sensor component.

As described above, the present invention provides a method and apparatus for determining the temperature of a sensor component of a vibrating meter. In contrast to prior art methods that require the use of additional components (such as RTDs), the present invention takes advantage of the correlation between V/I and temperature for the sensor components themselves. Advantageously, the temperature of the sensor component can be determined and then utilized to determine the temperature of the conduit coupled to the sensor component. By eliminating the need for RTDs, the costs associated with RTDs and with wiring can be eliminated.

The above detailed description of embodiments is not an exhaustive description of all embodiments contemplated by the inventors to be within the scope of the invention. Indeed, those skilled in the art will recognize that certain elements of the above-described embodiments may be variously combined or eliminated to create additional embodiments, and that such additional embodiments will fall within the scope and teachings of the present invention. It will also be apparent to those of ordinary skill in the art that the above-described embodiments may be combined in whole or in part to create additional embodiments within the scope and teachings of the present invention.

Thus, while specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. The teachings provided herein are applicable to other vibrating meters, not just the embodiments described above and shown in the figures. The scope of the invention should, therefore, be determined from the following claims.

Claims (24)

1. A method for determining a temperature of a vibrating sensor component coupled to a vibrating meter conduit, comprising the steps of:

providing a temperature determination signal to the vibration sensor component;

measuring the resulting signal; and

determining a temperature of the sensor component based on the temperature determination signal and the generated signal.

2. The method of claim 1, wherein the step of determining the temperature of the sensor component comprises:

determining a voltage to current ratio from the temperature determination signal and the measured resulting signal; and

determining a temperature of the sensor based on a correlation between the determined voltage to current ratio and temperature.

3. The method of claim 2, wherein the temperature determination signal comprises an alternating current at a frequency substantially equal to a resonant frequency of a conduit of the vibrating meter including a process fluid, and wherein the method further comprises the steps of:

removing the temperature determination signal for a predetermined time;

measuring a voltage;

determining a back electromotive force; and

the voltage to current ratio is compensated for by the back emf.

4. The method of claim 1, wherein the temperature determination signal comprises an alternating current at a frequency different from a resonant frequency of a conduit of the vibrating meter comprising a process fluid.

5. The method of claim 1, wherein the temperature determination signal comprises an alternating current at a frequency substantially equal to a resonant frequency of a conduit of the vibrating meter including a process fluid.

6. The method of claim 1, wherein the temperature-determining signal comprises an alternating current and the generated signal comprises a voltage.

7. The method of claim 1, wherein the temperature-determining signal comprises a fixed voltage and the generated signal comprises a current.

8. The method of claim 1, wherein the sensor component comprises a driver coil.

9. The method of claim 1, wherein the sensor component comprises a pick-off sensor coil.

10. A method for generating a correlation between a voltage to current ratio and a temperature of a sensor component coupled to a conduit of a vibration sensor, comprising the steps of:

providing a test signal to the sensor component;

measuring the first generated signal;

determining a first voltage to current ratio based on the test signal and the generated signal;

measuring a first temperature of the sensor component; and

storing the first determined voltage to current ratio with the first measured temperature.

11. The method of claim 10, further comprising the steps of:

measuring a second temperature of the sensor component; and

measuring a second resulting signal to determine at least a second voltage to current ratio if a second temperature of the sensor component varies from the first temperature by more than a threshold amount; and

storing the second voltage to current ratio with the second temperature.

12. The method of claim 10, wherein the sensor component comprises a driver coil.

13. The method of claim 10, wherein the sensor component comprises a pick-off sensor coil.

14. The method of claim 10, wherein the test signal comprises an alternating current and the generated signal comprises a voltage.

15. The method of claim 10, wherein the test signal comprises a fixed voltage and the generated signal comprises a current.

16. Meter electronics (220) for a vibrating meter (200), the vibrating meter (200) comprising one or more conduits (203A,203BA) and one or more sensor components (204A,205A,205' A) coupled to the one or more conduits (203A,203B), and the meter electronics (220) comprising a processing system (303), the processing system (303) configured to:

providing a temperature determination signal to a sensor component (204A,205A,205'A) of the one or more sensor components (204A,205A,205' A);

measuring the resulting signal; and

determining a temperature of the sensor component based on the temperature determination signal and the generated signal.

17. The meter electronics (220) of claim 16, wherein the processing system (303) is further configured to:

determining a voltage to current ratio based on the temperature determination signal and the generated signal;

and

determining a temperature of the sensor component based on a correlation between the determined voltage to current ratio and temperature.

18. The meter electronics (220) of claim 17, wherein the temperature determination signal comprises an alternating current at a frequency substantially equal to a resonant frequency of a conduit of the vibrating meter comprising a process fluid, and wherein the processing system (303) is further configured to:

removing the temperature determination signal for a predetermined time;

measuring a voltage;

determining a back electromotive force; and

the voltage to current ratio is compensated for by the back emf.

19. The meter electronics (220) of claim 16, wherein the temperature determination signal comprises an alternating current at a frequency different from a resonant frequency of a conduit (203A,203B) of the vibrating meter (200) comprising a process fluid.

20. The meter electronics (220) of claim 16, wherein the temperature determination signal comprises an alternating current at a frequency substantially equal to a resonant frequency of a conduit (203A,203B) of the vibrating meter (200) comprising a process fluid.

21. The meter electronics (220) of claim 16, wherein the temperature-determining signal comprises an alternating current and the generated signal comprises a voltage.

22. The meter electronics (220) of claim 16, wherein the temperature determination signal comprises a fixed voltage and the generated signal comprises a current.

23. The meter electronics (220) of claim 16, wherein the sensor component includes a drive coil (204A).

24. The meter electronics (220) of claim 16, wherein the sensor component comprises a pick-up coil (205A,205' a).