Meter electronics to optimize gas measurements in a coriolis flowmeter and related method

Abstract

A meter electronics (20) for a flowmeter (5) and related method is provided. The flowmeter (5) comprises at least one flow tube (130, 130'), at least one pickoff sensor (170L, 170R) and at least one driver (180L, 180R) attached thereto. The meter electronics (20) communicates with at least one pickoff sensor (170L, 170R) and at least one driver (180L, 180R), and sends a signal to the driver (180L, 180R) to vibrate at least one flow tube (130, 130') in a drive mode vibration, and receive a sensor signal based on a vibrational response to the vibration from at least one pickoff sensor (170L, 170R). The meter electronics (20) measures a density of the process fluid in at least one flow tube (130, 130'), determines if the density of the process fluid is below a predetermined density threshold, activates a gas optimization routine (220) if below the threshold, and adjusts a configuration parameter (218).

Description

[0001] METER ELECTRONICS TO OPTIMIZE GAS MEASUREMENTS IN A CORIOLIS FLOWMETER AND RELATED METHOD

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to flowmeters, and more particularly, to Coriolisbased measurement meter electronics and related devices that provide greater measurement accuracy of gaseous fluid flow.

[0004] BACKGROUND

[0005] Vibrating conduit sensors, such as Coriolis mass flowmeters and vibrating density meters, typically operate by detecting motion of a vibrating conduit that contains a flowing material. Properties associated with the material in the conduit, such as mass flow, density and the like, can be determined by processing measurement signals received from motion transducers associated with the conduit. The vibration modes of the vibrating material-filled system generally are affected by the combined mass, stiffness, and damping characteristics of the containing conduit and the material contained therein.

[0006] A typical Coriolis mass flowmeter includes one or more conduits (also called flow tubes) that are connected inline in a pipeline or other transport system and convey material, e.g., fluids, slurries, emulsions, and the like, in the system. Each conduit may be viewed as having a set of natural vibration modes, including for example, simple bending, torsional, radial, and coupled modes. In a typical Coriolis mass flow measurement application, a conduit is excited in one or more vibration modes as a material flows through the conduit, and motion of the conduit is measured at points spaced along the conduit. Excitation is typically provided by a driver, e.g., an electromechanical device, such as a voice coil-type actuator, that perturbs the conduit in a periodic fashion. Mass flow rate may be determined by measuring time delay or phase differences between motions at the transducer locations. Two or more such transducers (or pickoff sensors) are typically employed in order to measure a vibrational response of the flow tube or conduits and are typically located at positions upstream and downstream of the driver. Instrumentation receives signals from the pickoff sensors and processes the signals in order to derive a mass flow rate measurement. For most applications, a Coriolis flow meter is a suitable and high accuracy measurement device that is adaptable to a wide range of different process fluids and conditions. Coriolis meters offer high accuracy for single phase fluid flows, but in gaseous process fluid applications, there can be measurement challenges due to the different nature of gaseous phase fluids. These challenges can take the form of poor repeatability, perceived or real increases in the noise present in the measurement, nonlinearities, and similar issues.

[0007] What is needed is a flowmeter that accurately functions over a wide range of operating conditions. The present embodiments provide apparatuses and meter electronics for gas applications that improve measurement accuracy. Flowmeters and related meter electronics are provided wherein gaseous phase process fluid is automatically detected, and meter configuration and drive tuning settings are optimized to improve measurement quality. The embodiments also provide a mechanism to automatically inform the user of the detection of gaseous process fluids and the related suggested and / or changed settings through a local or remote user interface. In embodiments, this capability is embedded into meter electronics, and no changes to the physical hardware are necessary to practice this invention. Therefore, existing meters may be retrofitted, even in the field, to perform upgraded and optimized gas measurements. Thus, advancements in the art are achieved.

[0008] SUMMARY OF THE INVENTION

[0009] A method of operating meter electronics for improving flowmeter accuracy under gas flow conditions is provided according to an embodiment. The flowmeter comprises at least one flow tube, at least one pickoff sensor attached to the flow tube, at least one driver attached to the flow tube, and meter electronics in communication with the at least one pickoff sensor and driver, and operable to measure a fluid flowing through the at least one flow tube. The meter electronics is operable to perform vibrating at least one flow tube in a drive mode vibration with the at least one driver and receiving a sensor signal based on a vibrational response to the drive mode vibration from the at least one pickoff sensor. The meter electronics is further operable to perform measuring a density of the process fluid in the at least one flow tube, determining if the density of the process fluid is below a predetermined density threshold, and activating a gas optimization routine if the process fluid is below the predetermined density threshold, the gas optimization routine activated so that at least one configuration parameter of the meter electronics is adjusted.

[0010] A meter electronics for a flowmeter configured to improve measurement accuracy is provided according to an embodiment. The flowmeter comprises at least one flow tube, at least one pickoff sensor attached to the at least one flow tube, and at least one driver attached to the flow tube. The meter electronics is in communication with the at least one pickoff sensor and the at least one driver, and configured to send a signal to the at least one driver to vibrate at least one flow tube in a drive mode vibration, and receive a sensor signal based on a vibrational response to the drive mode vibration from the at least one pickoff sensor. The meter electronics is further configured to measure a density of the process fluid in the at least one flow tube, determine if the density of the process fluid is below a predetermined density threshold, and activate a gas optimization routine if the process fluid is below the predetermined density threshold. The gas optimization routine comprises adjusting at least one configuration parameter of the meter electronics.

[0011] ASPECTS

[0012] According to an aspect, a method of operating meter electronics for improving flowmeter accuracy under gas flow conditions is provided. The flowmeter comprises at least one flow tube, at least one pickoff sensor attached to the flow tube, at least one driver attached to the flow tube, and meter electronics in communication with the at least one pickoff sensor and driver, and operable to measure a fluid flowing through the at least one flow tube. The meter electronics is operable to perform vibrating at least one flow tube in a drive mode vibration with the at least one driver and receiving a sensor signal based on a vibrational response to the drive mode vibration from the at least one pickoff sensor. The meter electronics is further operable to perform measuring a density of the process fluid in the at least one flow tube, determining if the density of the process fluid is below a predetermined density threshold, and activating a gas optimization routine if the process fluid is below the predetermined density threshold, the gas optimization routine activated so that at least one configuration parameter of the meter electronics is adjusted. Preferably, the method comprises the step of adjusting a configuration parameter of the at least one configuration parameter comprising a damping parameter by increasing a time-windowed average of the measured flow rate.

[0013] Preferably, the method comprises the step of adjusting a configuration parameter of the at least one configuration parameter comprising changing a meter response time parameter.

[0014] Preferably, the method comprises the step of adjusting a configuration parameter of the at least one configuration parameter comprising narrowing a digital noise filter bandwidth.

[0015] Preferably, the method comprises the steps of measuring noise in a signal from the at least one pickoff sensor and adjusting the at least one configuration parameter, which comprises activating an active noise cancellation, which generates an anti-noise waveform from the detected noise and applies the anti-noise waveform to the signal from the at least one pickoff sensor.

[0016] Preferably, the method comprises the step of adjusting the configuration parameter of the at least one configuration parameter comprising increasing a drive current target.

[0017] Preferably, the method comprises the step of adjusting the configuration parameter of the at least one configuration parameter comprising raising a drive current threshold.

[0018] Preferably, the method comprises the step of adjusting the configuration parameter comprising adjusting drive proportional and integral responses until a balance between a drive circuit responsiveness and stability optimized for gas is realized.

[0019] Preferably, the predetermined density threshold is 200 kg / m3.

[0020] Preferably, an interface in communication with the meter electronics is configured to at least one of: prompt a user to initiate activating the gas optimization routine if the process fluid is below the predetermined density threshold and display a status of the gas optimization routine.

[0021] According to an aspect, a meter electronics for a flowmeter configured to improve measurement accuracy is provided. The flowmeter comprises at least one flow tube, at least one pickoff sensor attached to the at least one flow tube, and at least one driver attached to the flow tube. The meter electronics is in communication with the at least one pickoff sensor and the at least one driver, and configured to send a signal to the at least one driver to vibrate at least one flow tube in a drive mode vibration, and receive a sensor signal based on a vibrational response to the drive mode vibration from the at least one pickoff sensor. The meter electronics is further configured to measure a density of the process fluid in the at least one flow tube, determine if the density of the process fluid is below a predetermined density threshold, and activate a gas optimization routine if the process fluid is below the predetermined density threshold. The gas optimization routine comprises adjusting at least one configuration parameter of the meter electronics.

[0022] Preferably, the meter electronics comprises a configuration parameter of the at least one configuration parameter comprising a damping parameter operable to adjust a time-windowed average of the measured flow rate.

[0023] Preferably, the meter electronics comprises a configuration parameter of the at least one configuration parameter comprising a meter response time parameter operable to lower the rate at which flowmeter measurements are updated.

[0024] Preferably, the meter electronics comprises a digital noise filter bandwidth operable to narrow a digital noise filter bandwidth.

[0025] Preferably, the meter electronics is operable to measure noise in a signal derived from the at least one pickoff sensor and adjust a configuration parameter of the at least one configuration parameter comprising activating an active noise cancellation operable to generate an anti-noise waveform from the detected noise and apply the anti-noise waveform to the signal from the at least one pickoff sensor.

[0026] Preferably, the meter electronics comprises a configuration parameter of the at least one configuration parameter comprising a drive gain target operable to increase a voltage of a drive signal.

[0027] Preferably, the meter electronics comprises a configuration parameter of the at least one configuration parameter comprising adjusting a drive proportional and integral responses until a balance between a drive circuit responsiveness and stability optimized for gas is realized.

[0028] Preferably, the predetermined density threshold is 200 kg / m3.

[0029] Preferably, the meter electronics comprises an interface in communication with the meter electronics. The interface is operable to at least one of prompt a user to initiate activating the gas optimization routine if the process fluid is below the predetermined density threshold and display a status of the gas optimization routine. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 illustrates a flowmeter comprising a meter assembly and meter electronics;

[0031] FIG. 2 illustrates a block diagram of the meter electronics according to an embodiment;

[0032] FIG. 3 is a flow chart illustrating an embodiment of a gas optimization according to an embodiment; and

[0033] FIG. 4 is a graph illustrating Proportional / Integral tuning profiles.

[0034] DETAILED DESCRIPTION OF THE INVENTION

[0035] FIGS. 1-4 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 appreciate variations from 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.

[0036] FIG. 1 shows a vibratory flowmeter 5 according to an embodiment. The flowmeter 5 comprises a sensor assembly 10 and meter electronics 20 coupled to the sensor assembly 10. The sensor assembly 10 responds to at least mass flow rate and density of a process material. The meter electronics 20 is connected to the sensor assembly 10 via leads 100 to provide density, mass flow rate, and temperature information over a communication link 26, as well as other information. A Coriolis flowmeter structure is described although it is apparent to those skilled in the art that the present invention could also be operated as a vibrating tube densitometer.

[0037] The sensor assembly 10 includes manifolds 150 and 150', flanges 103 and 103' having flange necks 110 and 110', parallel flow tubes 130 and 130’, first and second drivers 180L and 180R, and first and second pickoff sensors 170L and 170R (for brevity, the drivers and pickoff sensors may herein be collectively referred to as “transducers”). The first and second drivers 180L and 180R are spaced apart on the one or more flow tubes 130 and 130’. In some embodiments, there is only a single driver. In addition, in some embodiments, the sensor assembly 10 may include a temperature sensor 190. The flow tubes 130 and 130' have two essentially straight inlet legs 131 and 131' and outlet legs 134 and 134' which converge towards each other at the flow tube mounting blocks 120 and 120'. The flow tubes 130 and 130’ bend at two symmetrical locations along their length and are essentially parallel throughout their length. The brace bars 140 and 140' serve to define the axis W and the substantially parallel axis W' about which each flow tube oscillates. It should be noted that in an embodiment, the first driver 180L may be collocated with the first pickoff sensor 170L, the second driver 180R may be collocated with the second pickoff sensor 170R.

[0038] The side legs 131, 13 T, 134, 134' of the flow tubes 130 and 130’ are fixedly attached to flow tube mounting blocks 120 and 120' and these blocks, in turn, are fixedly attached to the manifolds 150 and 150'. This provides a continuous closed material path through the sensor assembly 10.

[0039] When the flanges 103 and 103', having holes 102 and 102' arc connected, via the inlet end 104 and the outlet end 104' into a process line (not shown) which carries the process material that is being measured, material enters an inlet end 104 of the flowmeter 5 through an orifice 101 in the flange 103 and is conducted through the manifold 150 to the flow tube mounting block 120. Within the manifold 150, the material is divided and routed through the flow tubes 130 and 130’. Upon exiting the flow tubes 130 and 130’, the process material is recombined in a single stream within the manifold 150' and is thereafter routed to the outlet end 104' connected by the flange 103' having bolt holes 102' to the process line (not shown) via orifice 10T. The flow fluid can comprise a liquid. The flow fluid can comprise a gas. The flow fluid can comprise a multi-phase fluid, such as a liquid including entrained gases and / or entrained solids; or a gas including entrained liquids.

[0040] The flow tubes 130 and 130’ are selected and appropriately mounted to the flow tube mounting blocks 120 and 120' so as to have substantially the same mass distribution, moments of inertia, and Young's modulus about the bending axes W— W and W'— W', respectively. These bending axes go through the brace bars 140 and 140'. Inasmuch as the Young's modulus of the flow tubes change with temperature, and this change affects the calculation of flow and density, the temperature sensor 190, which may be a resistive temperature detector (RTD), is mounted to a flow tube 130, 130’ to continuously measure the temperature of the flow tube 130, 130'. The temperature-dependent voltage appearing across the temperature sensor 190 may be used by the meter electronics 20 to compensate for the change in the elastic modulus of the flow tubes 130 and 130’ due to any changes in flow tube temperature. The temperature sensor 190 is connected to the meter electronics 20 by lead 195.

[0041] The flow tubes 130, 130’ are typically driven by the driver 180L, 180R in opposite directions about the respective bending axes W and W' and at what is termed the first out of phase bending mode of the vibratory flowmeter 5. The driver 180L, 180R may comprise one of many well-known arrangements, such as a magnet mounted to the flow tube 130 and an opposing coil mounted to a proximate flow tube 130’. An alternating current is passed through the opposing coil to cause both flow tubes 130, 130" to oscillate. A suitable drive signal is applied by the meter electronics 20 to the driver 180L, 180R. Other driver devices are contemplated and are within the scope of the description and claims.

[0042] The meter electronics 20 receives sensor signals from the sensor assembly 10, and produces a drive signal which causes a driver 180L, 180R to oscillate the flow tubes 130, 130’. Other sensor devices are contemplated and are within the scope of the description and claims.

[0043] The meter electronics 20 processes the left and right velocity signals from the pick-off sensors 170L, 170R in order to compute a flow rate, among other things. The communication link 26 provides an input and an output means that allows the meter electronics 20 to interface with an operator or with other electronic systems.

[0044] In one embodiment, the flow tubes 130, 130’ comprise substantially U-shaped flow tubes, as shown. Alternatively, in other embodiments, the flowmeter 5 can comprise substantially straight flow tubes 130, 130’. Additional flowmeter shapes and / or configurations can be used and are within the scope of the description and claims.

[0045] The description of FIG. 1 is provided merely as an example of the operation of a flow metering device and is not intended to limit the teaching of the present invention.

[0046] FIG. 2 illustrates meter electronics 20 of the flowmeter 5 according to an embodiment of the invention. The meter electronics 20 can include an interface 201 and a processing system 203. The meter electronics 20 receives transducer signals from the sensor assembly 10, such as pickoff sensor 170L, 170R signals, for example without limitation. The meter electronics 20 processes sensor signals in order to obtain flow characteristics of the flow material flowing through the sensor assembly 10. For example, the meter electronics 20 can determine one or more of a phase difference, a frequency, a time difference (At), a density, a mass flow rate, a strain, and a volume flow rate from the sensor signals. In addition, other flow characteristics may be determined in some embodiments.

[0047] The interface 201 receives the sensor signals from the transducers via the leads 100 illustrated in FIG. 1. The interface 201 can perform any necessary or desired signal conditioning, such as any manner of formatting, amplification, buffering, etc. Alternatively, some or all of the signal conditioning can be performed in the processing system 203.

[0048] In addition, the interface 201 can enable communications between the meter electronics 20 and external devices, such as through the communication link 26, for example. The interface 201 can be capable of any manner of electronic, optical, or wireless communication.

[0049] The interface 201 in one embodiment includes a digitizer 202, wherein the sensor signal comprises an analog sensor signal. The digitizer 202 samples and digitizes the analog sensor signal and produces a digital sensor signal. The interface / digitizer 201 / 202 can also perform any needed decimation, wherein the digital sensor signal is decimated in order to reduce the amount of signal processing needed and to reduce the processing time.

[0050] The processing system 203 conducts operations of the meter electronics 20 and processes flow measurements from the sensor assembly 10. The processing system 203 executes one or more processing routines and thereby processes the flow measurements in order to produce one or more flow characteristics.

[0051] The processing system 203 can comprise a general-purpose computer, a microprocessing system, a logic circuit, or some other general purpose or customized processing device. The processing system 203 can be distributed among multiple processing devices. The processing system 203 can include any manner of integral or independent electronic storage medium, such as the storage system 204.

[0052] The processing system 203 is configured to retrieve and execute stored routines in order to operate the flowmeter 5. The storage system 204 can store routines including a general flowmeter routine 205, a gas optimization routine 220, a DSP routine 224, a PID routine 226, and other routines known in the art. The processing system 203 can determine at least a magnitude, phase difference, time difference, and a frequency of transducer signals. Other measurement / processing routines are contemplated and are within the scope of the description and claims. The storage system 204 can store measurements, received values, working values, and other information. In some embodiments, the storage system may store any one or more of a mass flow (m) 210, a density (p) 212, a viscosity (p) 214, a temperature (T) 216, configuration parameters 218, other values known in the art, and products thereof, for example without limitation. For the purposes of this description, parameters related to filters, PID settings, noise cancellation, flow rate damping, and any other embodiments having other parameters are all considered configuration parameters 218. The flowmeter routine 205 can produce and store fluid and flow measurements. These values can comprise substantially instantaneous measurement values or can comprise totaled or accumulated values and may also comprise databases and lookup tables. For example, the flowmeter routine 205 can generate mass flow measurements and store such measurements in the storage system 204. The flowmeter routine 205 can generate density measurements and store them in the storage system 204. Other measurements are contemplated to be similarly generated and stored in the storage system, as will be appreciated by one skilled in the art. The mass flow 210 and density 212 values are determined from the transducer response, as previously discussed and as known in the art. The mass flow 210 can comprise a substantially instantaneous mass flow rate value, can comprise a mass flow rate sample, can comprise an averaged mass flow rate over a time interval, or can comprise an accumulated mass flow rate over a time interval. The time interval may be chosen to correspond to a block of time during which certain fluid conditions are detected, for example, a liquid-only fluid state, or alternatively a gas-only fluid state. In addition, other mass flow quantifications are contemplated and are within the scope of the description and claims.

[0053] In an embodiment, flow is sensed by directly measuring the relative motion of the outlet 134, 134’ (or inlet 131, 131’) side of a flow tube 130, 130’ with respect to the inlet 131, 131’ (or outlet 134, 134’) side of the same flow tube 130, 130’. During fluid flow, signal outputs typically have an amplitude and phase that is a function of flow rate. In related embodiments, combined signals from one or more transducers on the inlet side of a meter and the combined signals from one or more transducers on the outlet side of the meter are input into the meter electronics. A phase measurement may be derived from the inlet and outlet signals.

[0054] Some challenges associated with gas flow measurements stem from the relatively more energetic nature of fluid flow, as compared with flow measurements of fluid in a liquid state, for example. When fluid flows through the flowmeter 5 is in the gaseous state, more turbulence, and therefore more random noise, is present, which affects measurements by making repeatability for any single measurement more challenging. In the embodiments provided herein, the flowmeter 5 is configured to detect gaseous process fluid and change flowmeter operation configuration settings to smooth this signal. This is effectuated by adding damping in some embodiments. In some embodiments, the digital signal processing is adjusted to help improve this repeatability and therefore improve measurement fidelity.

[0055] The gas optimization routine 220 comprises, at least in part, three aspects: detecting gaseous process fluid; adjusting the meter configuration and / or drive tuning settings; and interacting with the user to enable or disable and to advise of these settings and tuning changes. Not all aspects need be performed in all embodiments.

[0056] Turning to FIG. 3, a flowchart illustrating an embodiment of the gas optimization routine 220, for flowmeter optimization for gas a flow is provided.

[0057] In step 300, the gas optimization routine 220 starts, and the density of the flow through the flowmeter is measured. The natural vibration frequency of the flow tubes 130, 130’ is determined by their stiffness and mass. Since the volume of fluid in the flow tubes 130, 130’ is constant, a change in the density of the fluid causes a change in the mass within the flow tubes 130, 130’. When the mass inside the flow tubes 130, 130’ changes, the natural frequency of the tubes also changes, and this change is detected by the pickoff sensors 170L, 170R. The natural frequency is directly related to the density of the fluid inside the tubes. In embodiments, temperature is measured to compensate for the slight change in the tube stiffness (Young’s modulus) due to temperature changes, as will be understood to those skilled in the art. A predetermined density threshold to indicate gas flow is determined and stored in meter electronics. This may be input at the factory, or input by a user. In step 301, the density is compared to the predetermined threshold. If the density is greater than or equal to the predetermined threshold, step 300 is repeated. If the density is less than the predetermined threshold, the routine proceeds to step 302.

[0058] In an example, the predetermined threshold is 200 kg / m3. This is merely an example, and higher and lower thresholds are contemplated. In this example, if the measured density of fluid flow is under 200 kg / m3, it is determined that a gaseous process fluid is present. In a related embodiment, if gas flow is detected, an alert is generated and sent to the interface 201, which may include displaying the alert on a display, and / or sending the alert to a remote device via the communication link 26. If gas flow is not detected, the gas optimization routine 220 starts again, effectively polling for the presence of gas. In related embodiments, the gas routine is activated by an end user. In related embodiments, an end user is prompted to activate the gas routine when gas flow is detected.

[0059] In step 302, it is ascertained whether the gas optimization routine 220 is activated. If gas optimization is activated, which may be effectuated by an end user of the flowmeter 5, the gas optimization routine 220 proceeds to step 308. If gas optimization is not activated, then the gas optimization routine 220 starts again. When gas optimization is activated, the flowmeter will adjust various configuration parameters 218 to improve the accuracy and fidelity of the flow measurements if a gas is detected.

[0060] In an embodiment, if a gas is detected and gas optimization is active, a prompt is generated and sent to the interface 201, which may include displaying the alert on a display, and / or sending the alert to a remote device via the communication link 26. The prompt allows an end user to choose to continue with gas optimization or cancel the optimization process. In other embodiments, gas optimization will automatically occur when gas is detected. Choosing between a prompt and automatic optimization is a setting that is changeable by a user.

[0061] Turning to step 304, flowmeter configuration parameters 218 are adjusted to optimize the flowmeter for gas measurements. In an embodiment, configuration parameters 218 refer to parameters that are accessible and changeable to a user via the meter electronics 20. Examples where such parameters are accessed include data registers, Modbus registers, configuration menus, meter electronics 20 interfaces, etc. In some embodiments, configuration parameters 218 are set at the factory and are either not user-changeable or user-selectable between a predetermined number of options. Configuration parameters 218 that are not user-changeable are changed by meter electronics only in some embodiments.

[0062] In an embodiment, meter response time may be configured to improve gas measurements. Response time indicates the rate at which flowmeter measurements are updated, and thus how changes in fluid flow are captured. In an embodiment, the flowmeter response time parameter is set to a relatively high (slow, smooth, etc.) value, thus improving measurement performance by filtering a portion of the inherent noise in the flow measurement. In an embodiment, the response time dictates which filtering and signal processing configuration to activate as part of the DSP routine 224. In an embodiment, the meter response time parameter is set to a value predetermined to provide smoother responses, such as a preset entitled “smooth,” and / or an integer value (e.g. 0- 6) preset. Any preset values are stored in meter electronics 20.

[0063] In an embodiment, a flow rate damping parameter may be configured to improve gas measurements. Damping refers to adjusting a time-windowed average of the measured flow rate. In general, damping is generally set between about 0.4 seconds to 1.2 seconds as a default, for example. In an embodiment, the flowmeter damping parameter is set to between 1.6 to 10 seconds.

[0064] In an embodiment, adaptive bandwidth filtering may be activated or adjusted. This entails employing digital signal processing (DSP) as part of the DSP routine 224. In this case, a digital noise filter is coded into meter electronics, and its configuration parameters 218 are adjustable to change the bandwidth of the filter to combat the noise inherent in gas flow. In an embodiment, the filter automatically adjusts its configuration parameters 218 in response to the changing noise properties detected in the pickoff sensors 170L, 170R signals. This adaptability allows the filter to optimize its performance for varying signal conditions, thus enhancing the clarity and quality of the output, which is not possible with standard fixed-bandwidth filters commonly applied in the ait. In an embodiment, if a “gas” filter mode is selected, this configures the flowmeter to change filter constants. In an embodiment, a filter constant change includes narrowing / tightening a bandpass filter, thus removing higher frequency sources of noise that affect flow measurements. In an embodiment, a filter constant change includes activating a low-pass filter, thus removing higher frequency sources of noise that affects the flow measurement. As embodiments automatically detect gas, the filter change is automatically applied, or a user is prompted to apply the changes. In an embodiment, the filter constant configuration parameters 218 are automatically calculated by meter electronics and are based upon measured flowmeter conditions. In an embodiment, the filter constant configuration parameters 218 are predetermined by at least one of a factory setting and by user-input values.

[0065] In an embodiment, active noise cancellation (ANC) may be activated or adjusted. To reduce noise inherent in gas flow, the DSP routine 224 examines the characteristics of the noise waveform detected by pickoff sensors 170L, 170R. Noise is detected by monitoring the pickoff noise spectrum, and automatically identifying noise sources not related to the primary drive frequency or anything proximate to the delta t frequency. The DSP then generates an anti-noise waveform that is applied to the signal, which closely matches the shape and frequency of the offending noise waveform, and at an angle of 180 degrees out of phase from the noise. Adaptive cancellation, such that noise is detected with a transducer is employed in an embodiment. In this case, a transducer such as a coil and magnet, piezoelectric transducer, or audio transducer is in communication or proximate to the sensor assembly 10, provides an anti-noise signal that assists in negating noise. In an embodiment, a synthesis methodology is employed, where a plurality of samples over a period of noise cycles are stored, and an anti-noise waveform is generated based on the stored information.

[0066] In an embodiment, the flowmeter’s 5 drive gain, and / or target may be adjusted. This entails raising the drive current threshold of the meter electronics. Drive current, calculated on a scale of 0 to 100%, is an indication of the amount of power being consumed by the driver to keep the flow tubes 130 and 130’ vibrating at an appropriate magnitude. In an embodiment, the drive current is increased to maintain the flow tubes’ 130, 130’ vibratory magnitude, and thus achieve greater measurement accuracy. In an embodiment, the drive current target is adjusted. This entails redefining the definition of 100% of drive gain, such that the redefined 100% point is a higher voltage than the previously set voltage, thus driving the flow tubes 130 and 130’ harder than the previous 100% point. In an embodiment, the drive current target is between about 3.2 to about 3.6 mV / Hz, and the gas optimization routine 220 raises the drive current target to about 3.8 to 4.2 mV / Hz, thus improving the fidelity of the signal by improving the signal to noise ratio. In an embodiment, the drive current target is about 3.4 mV / Hz, and the gas optimization routine 220 raises the drive current target to about 4.0 mV / Hz.

[0067] In an embodiment, a proportional, integral, and derivative (PID) algorithm is applied, as part of the PID routine 226, to the drive circuit, which at least comprises one or more pickoff sensors 170L, 170R, one or more drivers 180L and 180R, and meter electronics 20. By detecting pickoff sensors 170L, 170R response to being driven, a desired ideal output may be ascertained by calculating proportional and integral (PI) responses and summing those components to compute the output. In an embodiment, drive PI tuning is adjusted, and this affects how the flowmeter 5 responds to flow. Generally, these tuning configuration parameters 218 are a compromise between compressible and incompressible process fluid. However, in the present embodiments, drive tuning configuration parameters 218 are tuned specifically for gas. FIG. 4 illustrates such tunings. Underdamped PI configuration parameters 218 yield a response that oscillates about the set point before eventually settling. This is illustrated by the shortdash line. An overdamped tuning tends to be relatively non-responsive, as illustrated by the long- short-long dashed line. The gas optimized setting strikes a balance between responsiveness and stability, as illustrated by the light solid line. In some embodiments, predetermined PI configuration parameters 218 for general flowmeter operation are substituted with predetermined configuration parameters 218 optimized for gas when gas optimization is implemented. In some embodiments, real-time optimization calculations are employed to arrive at optimized PI settings. In some embodiments, calculations incorporating the Ziegler-Nichols method, the Cohen-Coon method, or other algorithms, closed- or open-loop, are contemplated for PI tuning to balance between responsiveness and stability. It will be understood that there are thousands of different flowmeter permutations, considering at least flowmeter size, geometry, materials, transducers, operating parameters, process conditions, etc., where some or all characteristics may be different between flowmeter types and models, and even between individual units of the same model type due to manufacturing tolerances, and therefore no specific PI values work for all meters, as will be understood by those skilled in the art.

[0068] The sum of these configuration parameter and tuning changes provides a targeted measurement system for gaseous service, versus a general "one size fits all" approach to Coriolis meter configuration and tuning. In an embodiment, one or more configuration parameters 218 are changed during the gas optimization routine 220. In an embodiment, the one or more configuration parameters 218 changed during the gas optimization routine 220 revert to their previous values and settings implemented before the gas optimization routine 220 executed.

[0069] As there are thousands of different flowmeters each having various sizes, geometry, materials, transducers, operating parameters, process conditions, etc., it will be understood by those skilled in the art that a broad range of combined parameter values and combined gas-activated parameter values are contemplated, and will differ among different flowmeters having different applications.

[0070] The present description depicts specific examples to teach those skilled in the art how to make and use the best mode of the invention. To teach inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the invention.

[0071] The detailed descriptions of the above embodiments are not exhaustive descriptions of all embodiments contemplated by the inventors to be within the scope of the invention. Indeed, persons skilled in the art will recognize that certain elements of the above-described embodiments may variously be combined or eliminated to create further embodiments, and such further embodiments fall within the scope and teachings of the invention. It will also be apparent to those of ordinary skill in the art that the abovedescribed embodiments may be combined in whole or in part to create additional embodiments within the scope and teachings of the invention.

[0072] Thus, although 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 may be applied to other embodiments than those described above and shown in the accompanying figures. Accordingly, the scope of the invention is determined from the following claims.

Claims

CLAIMSWe claim:

1. A method of operating meter electronics (20) for improving flowmeter (5) accuracy under gas flow conditions, wherein the flowmeter (5) comprises at least one flow tube (130, 130’), at least one pickoff sensor (170L, 170R) attached to the flow tube, at least one driver (180L, 180R) attached to the flow tube, and meter electronics in communication with the at least one pickoff sensor (170L, 170R) and driver (180L, 180R), and operable to measure a fluid flowing through the at least one flow tube (130, 130’), the meter electronics (20) operable to perform: vibrating at least one flow tube (130, 130’) in a drive mode vibration with the at least one driver (180L, 180R); receiving a sensor signal based on a vibrational response to the drive mode vibration from the at least one pickoff sensor (170L, 170R); measuring a density of the process fluid in the at least one flow tube (130, 130’); determining if the density of the process fluid is below a predetermined density threshold; activating a gas optimization routine (220) if the process fluid is below the predetermined density threshold, the gas optimization routine (220) activated so that at least one configuration parameter (218) of the meter electronics is adjusted.

2. The method of claim 1, comprising the step of adjusting a configuration parameter (218) of the at least one configuration parameter (218) comprising a damping parameter by increasing a time-windowed average of the measured flow rate.

3. The method of claim 1, comprising the step of adjusting a configuration parameter (218) of the at least one configuration parameter (218) comprising changing a meter response time parameter.

4. The method of claim 1, comprising the step of adjusting a configuration parameter (218) of the at least one configuration parameter (218) comprising narrowing a digital noise filter bandwidth.

5. The method of claim 1, comprising the steps of: measuring noise in a signal from the at least one pickoff sensor (170L, 170R); adjusting the at least one configuration parameter (218), comprising activating an active noise cancellation, wherein the active noise cancellation comprises generating an anti-noise waveform from the detected noise; and applying the anti-noise waveform to the signal from the at least one pickoff sensor (170L, 170R).

6. The method of claim 1, comprising the step of adjusting the configuration parameter (218) of the at least one configuration parameter (218) comprising increasing a drive current target.

7. The method of claim 1, comprising the step of adjusting the configuration parameter (218) of the at least one configuration parameter (218) comprising raising a drive current threshold.

8. The method of claim 1 , wherein the step of adjusting the configuration parameter (218) comprising adjusting drive proportional and integral responses until a balance between a drive circuit responsiveness and stability optimized for gas is realized.

9. The method of claim 1, wherein the predetermined density threshold is 200 kg / m3.

10. The method of claim 1, wherein an interface in communication with the meter electronics is configured to at least one of: prompt a user to initiate activating the gas optimization routine (220) if the process fluid is below the predetermined density threshold; and display a status of the gas optimization routine (220).

11. Meter electronics (20) for a flowmeter (5) configured to improve measurement accuracy, wherein the flowmeter (5) comprises:at least one flow tube (130, 130'); at least one pickoff sensor (170L, 170R) attached to the at least one flow tube (130, 130’); and at least one driver (180L, 180R) attached to the flow tube (130, 130’); wherein the meter electronics (20) is in communication with the at least one pickoff sensor (170L, 170R) and the at least one driver (180L, 180R), and configured to: send a signal to the at least one driver (180L, 180R) to vibrate at least one flow tube (130, 130’) in a drive mode vibration; receive a sensor signal based on a vibrational response to the drive mode vibration from the at least one pickoff sensor (170L, 170R); wherein the meter electronics (20) is further configured to: measure a density of the process fluid in the at least one flow tube (130, 130’); determine if the density of the process fluid is below a predetermined density threshold; activate a gas optimization routine (220) if the process fluid is below the predetermined density threshold, the gas optimization routine (220) comprising adjusting at least one configuration parameter (218) of the meter electronics (20).

12. The meter electronics (20) of claim 11 , comprising a configuration parameter (218) of the at least one configuration parameter (218) comprising a damping parameter operable to adjust a time-windowed average of the measured flow rate.

13. The meter electronics (20) of claim 11, comprising a configuration parameter (218) of the at least one configuration parameter (218) comprising a meter response time parameter operable to lower the rate at which flowmeter (5) measurements are updated.

14. The meter electronics (20) of claim 11 , comprising a digital noise filter bandwidth operable to narrow a digital noise filter bandwidth.

15. The meter electronics (20) of claim 11 , operable to: measure noise in a signal derived from the at least one pickoff sensor (170L,170R); adjust a configuration parameter (218) of the at least one configuration parameter (218) comprising activating an active noise cancellation operable to: generate an anti-noise waveform from the detected noise; and apply the anti-noise waveform to the signal from the at least one pickoff sensor (170L, 170R).

16. The meter electronics (20) of claim 11, comprising a configuration parameter (218) of the at least one configuration parameter (218) comprising a drive gain target operable to increase a voltage of a drive signal.

17. The meter electronics (20) of claim 11, comprising a configuration parameter (218) of the at least one configuration parameter (218) comprising adjusting a drive proportional and integral responses until a balance between a drive circuit responsiveness and stability optimized for gas is realized.

18. The meter electronics (20) of claim 11, wherein the predetermined density threshold is 200 kg / m3.

19. The meter electronics (20) of claim 11, comprising an interface (201) in communication with the meter electronics (20), the interface (201) operable to at least one of: prompt a user to initiate activating the gas optimization routine (220) if the process fluid is below the predetermined density threshold; and display a status of the gas optimization routine (220).

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