Determining the zero verification criteria for vibration meters

Abstract

Meter electronics (20) for determining a zero verification criterion for zero verification of a vibrometer (5) is provided, the meter electronics (20) comprising an interface (401) communicatively coupled to a sensor assembly (10) containing a fluid, and a processing system (402) communicatively coupled to the interface (401). The processing system (402) is configured to determine a property of the fluid and determine a zero verification criterion value for the sensor assembly (10) based on the property of the fluid.

Description

[Technical Field]

[0001] The embodiments described below relate to verifying the operation of a vibrometer, and more particularly to determining a zero verification criterion for zero verification of a vibrometer. [Background technology]

[0002] Vibrometers, such as Coriolis mass flow meters, liquid densitometers, gas densitometers, liquid viscometers, gas / liquid specific gravity meters, gas / liquid relative density meters, and gas molecular weight meters, are commonly known and are used to measure fluid properties. Generally, a vibrometer comprises a sensor assembly and meter electronics. The material within the sensor assembly may be flowing or stationary. The vibrometer can be used to measure the mass flow rate, density, or other properties of the material within the sensor assembly.

[0003] To measure such fluid properties of a material, the vibrometer may need to use a reference zero flow value. The reference zero flow value may be equivalent to the zero flow value of the measured property. The actual non-zero property can be quantified as a scaled or unscaled difference from the reference zero flow value. As can be appreciated, accurate measurement of the actual non-zero property may depend on an accurate reference zero flow value. An accurate reference zero flow value can be determined in a zero calibration. The accuracy of the reference zero flow value can be verified in a zero verification. Zero calibration and zero verification can be performed by fluidically isolating the vibrometer so that any measurements can be correctly assumed to reflect a property having a zero flow value (e.g., zero flow).

[0004] FIG. 1 illustrates a system 1 capable of performing zero verification and zero calibration of a vibrometer 5. As illustrated in FIG. 1, the system 1 includes a meter inlet block valve 2a and a meter outlet block valve 2b. The meter inlet and outlet block valves 2a and 2b are configured to block fluid flow. Therefore, the fluid flow rate through the vibrometer 5 can be zero. Also illustrated is a fluid bypass loop 3 including a bypass inlet pipe 3a, a bypass block valve 3b, and a bypass outlet pipe 3c. The bypass inlet pipe 3a, the bypass block valve 3b, and the bypass outlet pipe 3c are configured to allow fluid to bypass the vibrometer 5 when the bypass block valve 3b is open. Upstream from the vibrometer 5 are a blowdown valve port 4a and a thermowell port 4b.

[0005] During zero verification and zero calibration, the meter inlet and outlet block valves 2a, 2b are closed, thereby blocking fluid flow through the vibrometer 5. This may be referred to as the zero flow state of the vibrometer 5. During zero verification and zero calibration, the vibrometer 5 may measure one or more zero flow values, which may be values ​​related to zero flow of fluid. In a Coriolis meter, the zero flow value may be the time delay or phase difference between sensor signals when the vibrometer 5 is in the zero flow state.

[0006] The vibrometer 5 can use a reference zero flow value to calculate the flow rate of the fluid through the vibrometer 5. During zero calibration, the vibrometer 5 can determine one or more zero flow values ​​that can be used to calculate the reference value. During zero verification, the vibrometer 5 can compare the one or more zero flow values ​​to a reference to determine whether the reference zero flow value can be used to calculate the flow rate of the fluid. If the reference zero flow value is not acceptable, a zero calibration can be performed.

[0007] A predetermined reference zero flow value can be compared to one or more zero flow values ​​to determine whether the reference zero flow value can be used to calculate the flow rate of a fluid. In such a comparison, a zero verification criterion can be employed to determine whether a zero calibration should be performed. However, the zero verification criterion may not be suitable for a particular process. In addition, various processes may be used in a single location, requiring different degrees of accuracy in flow measurement. Therefore, there is a need to determine a zero verification criterion for zero verification of a vibrometer. Summary of the Invention

[0008] Meter electronics for determining a zero verification reference for zero verification of a vibrometer are provided. According to one embodiment, the meter electronics includes an interface communicatively coupled to a sensor assembly containing a fluid, and a processing system communicatively coupled to the interface. The processing system is configured to determine a property of the fluid and to determine a zero verification reference value for the sensor assembly based on the property of the fluid.

[0009] A method for determining a zero verification reference for zero verification of a vibrometer is provided, according to one embodiment, the method includes containing a fluid within a sensor assembly, determining a property of the fluid, and determining a zero verification reference value for the sensor assembly based on the property of the fluid.

[0010] A vibrometer capable of determining a zero verification reference for performing zero verification is provided. According to one embodiment, the vibrometer comprises a sensor assembly containing a fluid and instrument electronics communicatively coupled to the sensor assembly.

[0011] [Aspect] According to one aspect, meter electronics for determining a zero verification reference for zero verification of a vibrometer includes an interface communicatively connected to a sensor assembly containing a fluid, and a processing system communicatively connected to the interface, the processing system configured to determine a property of the fluid and to determine a zero verification reference value for the sensor assembly based on the property of the fluid.

[0012] Preferably, the processing system configured to determine a property of the fluid comprises a processing system configured to measure a property of the fluid while the fluid is contained within the sensor assembly in a non-flowing state.

[0013] Preferably, the fluid property is one of the density and phase of the fluid.

[0014] Preferably, the processing system configured to determine the zero check reference value comprises a processing system configured to determine the first zero check reference value by multiplying the second zero check reference value by a coefficient.

[0015] Preferably, the coefficient is a ratio determined based on a first tolerance associated with a first expected flow rate of the fluid and a second tolerance associated with a second expected flow rate of the fluid.

[0016] Preferably, the zero verification reference value is at least one of a bias indicator confidence threshold and a zero stability value for the reference zero flow value.

[0017] According to one aspect, a method for determining a zero verification reference for zero verification of a vibrometer includes containing a fluid in a sensor assembly, determining a characteristic of the fluid, and determining a zero verification reference value for the sensor assembly based on the characteristic of the fluid.

[0018] Preferably, the property of the fluid is measured while the fluid is contained within the sensor assembly in a non-flowing state.

[0019] Preferably, the fluid property is one of the density and phase of the fluid.

[0020] Preferably, the zero check reference value is a first zero check reference value determined by multiplying a second zero check reference value by a coefficient.

[0021] Preferably, the coefficient is a ratio determined based on a first tolerance associated with a first expected flow rate of the fluid and a second tolerance associated with a second expected flow rate of the fluid.

[0022] Preferably, the zero verification reference value is at least one of a bias indicator confidence threshold and a zero stability value for the reference zero flow value.

[0023] According to one aspect, a vibrometer capable of determining a zero verification criteria for performing zero verification comprises a sensor assembly containing a fluid and meter electronics communicatively coupled to the sensor assembly. [Brief explanation of the drawings]

[0024] Like reference numbers represent like elements in all drawings. It should be understood that the drawings are not necessarily to scale. [Figure 1] FIG. 1 shows a system 1 capable of performing zero verification and zero calibration of a vibrometer 5 . [Figure 2] FIG. 2 shows a vibrometer 5 configured to determine a zero verification criterion for the zero verification of the vibrometer 5 . [Figure 3] FIG. 3 shows a block diagram of a vibrometer 5, including a block diagram of meter electronics 20 configured to determine a zero verification criterion for zero verification of the vibrometer 5. [Figure 4] FIG. 4 shows the meter electronics 20 for determining the zero verification criteria for the zero verification of the vibrometer 5. [Figure 5] FIG. 5 shows a graph 500 illustrating the AGA11 standards for tolerances on flow measurements. [Figure 6] FIG. 6 shows a zero verification graph 600 illustrating the zero verification of the vibrometer 5 . [Figure 7] FIG. 7 illustrates a method 700 for determining a zero verification criterion for zero verification of a vibrometer. DETAILED DESCRIPTION OF THE INVENTION

[0025] 1-7 and the following description provide specific examples to teach those skilled in the art how to make and use the best mode embodiments for determining a zero verification reference for zero verification of a vibrometer. For the purpose of teaching the principles of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these embodiments that fall within the scope of the present disclosure. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations for determining a zero verification reference for zero verification of a vibrometer. Consequently, the embodiments described below are not limited to the specific examples described below, but are limited only by the claims and their equivalents.

[0026] FIG. 2 illustrates a vibrometer 5 configured to determine a zero verification criteria for zero verification of the vibrometer 5. As shown in FIG. 2, the vibrometer 5 includes a sensor assembly 10 and meter electronics 20. The sensor assembly 10 is responsive to the mass flow rate and density of a process material. The meter electronics 20 is connected to the sensor assembly 10 via leads 100 and provides density, mass flow rate, and temperature information, as well as other information, through a port 26.

[0027] The sensor assembly 10 includes a pair of manifolds 150 and 150', flanges 103 and 103' with flange necks 110 and 110', a pair of parallel conduits 130 and 130', a driver 180, a resistance temperature detector (RTD) 190, and a pair of pickoff sensors 170l and 170r. The conduits 130 and 130' have two essentially straight inlet legs 131 and 131' and outlet legs 134 and 134' that converge toward each other at the conduit mounting blocks 120 and 120'. The conduits 130 and 130' bend at two symmetrical locations along their lengths and are essentially parallel throughout their lengths. Brace bars 140 and 140' serve to define axes W and W' about which each conduit 130 and 130' oscillates. Legs 131, 131′ and 134, 134′ of conduits 130, 130′ are fixedly attached to conduit mounting blocks 120 and 120′, which are in turn fixedly attached to manifolds 150 and 150′. This provides a continuous, closed material path through sensor assembly 10.

[0028] When flanges 103 and 103', having holes 102 and 102', are connected via inlet end 104 and outlet end 104' to a process line (not shown) carrying the process material to be metered, the material enters the meter at inlet end 104 through orifice 101 in flange 103 and is directed through manifold 150 to conduit mounting block 120, having face 121. Within manifold 150, the material is split and directed through conduits 130 and 130'. Upon exiting conduits 130 and 130', the process material is recombined into a single stream within block 120', having face 121' and manifold 150', before being directed to outlet end 104', which is connected to the process line (not shown) by flange 103', having hole 102'.

[0029] The conduits 130, 130' are selected to have substantially the same mass distribution, moment of inertia, and Young's modulus about bending axes W-W and W'-W', respectively, and are appropriately mounted to the conduit mounting blocks 120, 120'. These bending axes pass through the brace bars 140, 140'. Because the Young's modulus of the conduit changes with temperature, which affects flow rate and density calculations, an RTD 190 is attached to the conduit 130' to continuously measure the temperature of the conduit 130'. The temperature of the conduit 130', and therefore the voltage appearing across the RTD 190 for a given current flowing therethrough, is determined by the temperature of the material passing through the conduit 130'. The temperature-dependent voltage appearing across the RTD 190 is used by the meter electronics 20 in a well-known manner to compensate for changes in the elastic modulus of the conduits 130, 130' due to changes in the conduit temperature. The RTD 190 is connected to the meter electronics 20 by leads 195.

[0030] Both conduits 130, 130' are driven in opposite directions about their respective bending axes W and W' and in what is called a vibrometer first out-of-phase mode by a driver 180. This driver 180 may comprise any one of a number of well-known configurations, such as a magnet attached to conduit 130' and an opposing coil attached to conduit 130 through which an alternating current flows to vibrate both conduits 130, 130'. An appropriate drive signal 185 is applied to driver 180 by meter electronics 20 via leads.

[0031] Meter electronics 20 receives the RTD temperature signal on lead 195 and sensor signal 165 appearing on lead 100, which carries left and right sensor signals 165l and 165r, respectively. Meter electronics 20 generates drive signal 185 appearing on lead to driver 180, causing conduits 130 and 130' to vibrate. Meter electronics 20 processes left and right sensor signals 165l and 165r and RTD signal 195 to calculate the mass flow rate and density of material passing through sensor assembly 10. This information, along with other information, is applied by meter electronics 20 as a signal over path 26. A more detailed discussion of meter electronics 20 follows.

[0032] 3 illustrates a block diagram of the vibrometer 5, including a block diagram of the meter electronics 20 configured to determine a zero verification criteria for the zero verification of the vibrometer 5. As shown in FIG. 3, the meter electronics 20 is communicatively connected to the sensor assembly 10. As previously described with reference to FIG. 2, the sensor assembly 10 includes left and right pickoff sensors 170l, 170r, a driver 180, and a temperature sensor 190, which are communicatively connected to the meter electronics 20 via a set of leads 100 through a communication channel 112.

[0033] Meter electronics 20 provides drive signals 185 via leads 100. More specifically, meter electronics 20 provides drive signals 185 to drivers 180 within sensor assembly 10. Additionally, sensor signals 165, including left sensor signal 165l and right sensor signal 165r, are provided by sensor assembly 10. More specifically, in the illustrated embodiment, sensor signals 165 are provided by left and right pickoff sensors 170l, 170r within sensor assembly 10. As can be seen, sensor signals 165 are each provided to meter electronics 20 through communication channel 112.

[0034] Meter electronics 20 includes a processor 210 communicatively coupled to one or more signal processors 220 and one or more memories 230. Processor 210 is also communicatively coupled to user interface 30. Processor 210 is communicatively coupled to a host through a communications port via port 26 and receives power through power port 250. Processor 210 may be a microprocessor, or any suitable processor may be used. For example, processor 210 may be comprised of sub-processors such as a multi-core processor, a serial communications port, a peripheral interface (e.g., a serial peripheral interface), on-chip memory, I / O ports, etc. In these and other embodiments, processor 210 is configured to perform operations on received and processed signals, such as digitized signals.

[0035] The processor 210 can receive digitized sensor signals from one or more signal processors 220. The processor 210 can also be configured to provide information such as a phase difference, characteristics of the fluid in the sensor assembly 10, etc. The processor 210 can provide the information to a host through a communication port. The processor 210 can also be configured to communicate with one or more memories 230 to receive and / or store information in the one or more memories 230. For example, the processor 210 can receive calibration coefficients and / or sensor assembly zeros (e.g., a phase difference at zero flow rate) from the one or more memories 230. Each of the calibration coefficients and / or sensor assembly zeros can be associated with the vibrometer 5 and / or the sensor assembly 10, respectively. The processor 210 can use the calibration coefficients to process the digitized sensor signals received from the one or more signal processors 220.

[0036] The one or more signal processors 220 are shown as comprising an encoder / decoder (CODEC) 222 and an analog-to-digital converter (ADC) 226. The one or more signal processors 220 may condition analog signals, digitize the conditioned analog signals, and / or provide digitized signals. The CODEC 222 is configured to receive the sensor signals 165 from the left and right pickoff sensors 170l, 170r. The CODEC 222 is also configured to provide the drive signals 185 to the driver 180. In alternative embodiments, more or fewer signal processors may be used.

[0037] As shown, the sensor signal 165 is provided to the CODEC 222 via a signal conditioner 240. While the signal conditioner 240 is shown as a single block, the signal conditioner 240 may be comprised of signal conditioning components such as two or more operational amplifiers, filters such as low-pass filters, and voltage-current amplifiers. For example, the sensor signal 165 may be amplified by a first amplifier, and the drive signal 185 may be amplified by a voltage-current amplifier. The amplification may ensure that the magnitude of the sensor signal 165 is close to the full-scale range of the CODEC 222.

[0038] In the illustrated embodiment, the one or more memories 230 comprise read-only memory (ROM) 232, random access memory (RAM) 234, and ferroelectric random access memory (FRAM®) 236. However, in alternative embodiments, the one or more memories 230 may comprise more or less memory. Additionally or alternatively, the one or more memories 230 may comprise different types of memory (e.g., volatile, non-volatile, etc.). For example, another type of non-volatile memory, such as, for example, an erasable programmable read-only memory (EEPROM), may be used in place of the FRAM® 236. The one or more memories 230 may be storage devices configured to store process data, such as drive or sensor signals, mass flow or density measurements, etc.

[0039] Mass flow measurements can be generated according to the following equation:

number

number

[0040] The measured time delay Δt comprises an operationally derived (i.e., measured) time delay value that includes the time delay present between pickoff sensor signals, such as the time delay due to the Coriolis effect associated with mass flow through the vibrometer 5. The measured time delay Δt is a direct measurement of the mass flow rate of the flowing material as it flows through the vibrometer 5. The zero-flow time delay Δt0 comprises the time delay at zero flow rate. The zero-flow time delay Δt0 is a zero-flow value that is determined at factory and programmed into the vibrometer 5. The zero-flow time delay Δt0 is an example of a zero-flow value. Other zero-flow values, such as a phase difference, time difference, etc., determined at zero-flow conditions, may also be used. The zero-flow time delay Δt0 may not change even as flow conditions change. The mass flow rate value of the material flowing through the vibrometer 5 is determined by multiplying the difference between the measured time delay Δt and the reference zero-flow value Δt0 by the flow calibration factor FCF. The flow calibration factor FCF is proportional to the physical stiffness of the vibrometer.

[0041] With respect to density, the resonant frequency at which each conduit 130, 130' vibrates may be a function of the square root of the spring constant of the conduit 130, 130' divided by the total mass of the conduit 130, 130' containing the material. The total mass of the conduit 130, 130' containing the material may be the mass of the conduit 130, 130' plus the mass of the material within the conduit 130, 130'. The mass of the material within the conduit 130, 130' is directly proportional to the density of the material. Therefore, the density of the material is proportional to the square of the period at which the conduit 130, 130' containing the material vibrates multiplied by the spring constant of the conduit 130, 130'. Therefore, by determining the period at which the conduit 130, 130' vibrates and scaling the result appropriately, an accurate measure of the density of the material contained within the conduit 130, 130' can be obtained. The meter electronics 20 can determine the period or resonant frequency using the sensor signal 165 and / or the drive signal 185. The conduits 130, 130' can vibrate in multiple vibration modes.

[0042] [Calibration] The vibrometer 5 can be calibrated with a factory zero flow value while the vibrometer 5 is in a no-flow or zero-flow state. At any time, the user can optionally perform a push-button calibration to obtain a push-button zero flow value. Additionally or alternatively, the vibrometer can be automatically calibrated to obtain an automatic zero flow value. The zero flow value used to measure the fluid flow rate can be a factory zero flow value, a push-button zero flow value, an automatic zero flow value, or any other suitable zero flow value.

[0043] Measurements, stored values / constants, user settings, saved tables, etc. may be used during zero calibration of the vibrometer 5. Calibration may monitor and compensate for flow meter conditions of the vibrometer 5. The conditions may include, but are not limited to, user-entered conditions, measured conditions, estimated conditions, etc. Conditions may include temperature, fluid density, flow rate, meter specifications, viscosity, Reynolds number, post-calibration corrections, etc. Additionally, different constants, such as, but not limited to, a flow calibration factor (FCF), may be applied based on operating conditions or user preferences.

[0044] The initial zero flow value may be determined during a calibration performed as part of the initial factory setup of the vibrometer 5. This may require placing the vibrometer 5 in a no-flow or zero-flow condition and determining the time delay, phase difference, etc. between the left and right sensor signals 165l, 165r. The determined value is stored in one or more memories 230 as the initial zero flow value and used as the reference zero flow value. For example, for equation [1] discussed above, the reference zero flow value may be the Δt term, which may be the no-flow or zero-flow time delay between the left and right sensor signals 165l, 165r. Once the reference zero flow value is determined, a flow calibration factor (FCF) may be established, which, as seen in equation [1] above, may be calculated by multiplying the measured time delay Δt measured and mass flow rate

number

[0045] [Zero Verification] The zero verification may include comparing the new zero flow value to a reference zero flow value. For example, the new zero flow value may be compared to a factory-determined zero flow value (e.g., a factory zero flow value), although any suitable reference zero flow value may be used. The new zero flow value may be determined, for example, by averaging multiple zero flow value measurements taken while the vibrometer 5 is installed in the process line but fluidically isolated, as described above with reference to FIG. 1.

[0046] Comparing the new zero flow value to the reference zero flow value may include comparing multiple zero flow value measurements to the reference zero flow value. If the multiple zero flow value measurements are not within an acceptable range (e.g., a "predetermined boundary," a "zero stability value," etc.) for the reference zero flow value, the reference zero flow value is no longer valid and the new zero flow value may be stored as the reference zero flow value. If the new zero flow value is within an acceptable range for the reference zero flow value, the reference zero flow value may be valid and the new zero flow value may or may not be stored as the reference zero flow value.

[0047] However, the tolerance range for the reference zero flow value may be based on calibration of the vibrometer 5 at factory conditions, which may not be suitable for all processes. Also, after installation, the vibrometer 5 may be subject to more specialized installation, operating, and / or process conditions that differ from factory conditions. For example, installation conditions may cause a relatively small shift (e.g., within the tolerance range for the reference zero flow value) in the actual zero flow time delay of the conduits 130, 130′. Furthermore, the process in which the vibrometer 5 is used may have mass flow measurement tolerances that require a tighter tolerance for the reference zero value.

[0048] Therefore, even if the measured zero flow value is within an acceptable range of the reference zero flow value, the reference zero flow value may be invalid for the process. For example, if the bias indicator for the reference zero flow value indicates that the reference zero flow value causes a measurement bias that causes the measured flow value to fall outside the acceptable range of flow measurement, the reference zero flow value may be invalid. This determination and evaluation of the bias indicator for the reference zero flow value may be performed in addition to or instead of determining whether multiple measured zero flow values ​​are within an acceptable range of the reference zero flow value.

[0049] The bias indicator for the reference zero flow value may be any indicator that can prove that the reference zero flow value causes measurement bias. For example, the bias indicator may be composed of a central tendency value and a variance value associated with the zero flow value measurements. The central tendency value may be the mean of the zero flow value measurements, and the variance value may be the standard deviation of the new zero flow value measurements. In another example, the bias indicator may be a ratio (e.g., a sign ratio) of the positive or negative value of the difference between the new zero flow value measurements and the reference zero flow value to the total number of new zero flow value measurements. However, any suitable bias indicator that can reliably indicate that the reference zero flow value causes measurement bias may be used.

[0050] Zero verification can include these and other zero verification criteria depending, for example, on the particular process, fluid type, etc. For example, as described above, the vibrometer 5 can measure liquids or gases. The zero verification criteria for liquids can be different from the zero verification criteria for gases. The zero verification criteria can have different tolerances, thresholds, etc. for the reference zero flow value. Accordingly, the meter electronics 20 can be configured to select the zero verification criteria.

[0051] FIG. 4 illustrates meter electronics 20 for determining a zero verification criteria for zero verification of vibration meter 5. As shown in FIG. 4, meter electronics 20 includes an interface 401 and a processing system 402. Meter electronics 20 receives a vibration response from a sensor assembly, such as sensor assembly 10. Meter electronics 20 processes the vibration response to obtain flow characteristics of the flowable material flowing through sensor assembly 10. Meter electronics 20 may also perform checks, verifications, calibration routines, etc. to ensure that the flow characteristics of the flowable material are accurately measured.

[0052] The interface 401 can receive the sensor signal 165 from one of the pickoff sensors 170l, 170r shown in FIGS. 2 and 3. The interface 401 can perform any necessary or desired signal conditioning, such as formatting, amplification, buffering, or the like. Alternatively, some or all of the signal conditioning can be performed in the processing system 402. Additionally, the interface 401 can facilitate communication between the meter electronics 20 and an external device. The interface 401 can be any form of electronic, optical, or wireless communication. The interface 401 can provide information based on the vibration response. The interface 401 can be coupled to a digitizer, such as the CODEC 222 shown in FIG. 3, where the sensor signal includes an analog sensor signal. The digitizer samples and digitizes the analog sensor signal to generate a digitized sensor signal.

[0053] The processing system 402 performs the operations of the meter electronics 20 and processes the flow measurements from the sensor assembly 10. The processing system 402 executes one or more processing routines, thereby processing the flow measurements to generate one or more flow characteristics. The processing system 402 is communicatively coupled to the interface 401 and configured to receive information from the interface 401.

[0054] Processing system 402 may comprise a general-purpose computer, a microprocessing system, a logic circuit, or some other general-purpose or customized processing device. Additionally or alternatively, processing system 402 may be distributed among multiple processing devices. Processing system 402 may also include any form of integrated or stand-alone electronic storage medium, such as storage system 404.

[0055] The storage system 404 can store vibrometer parameters and data, software routines, constant values, and variable values. In one embodiment, the storage system 404 includes routines executed by the processing system 402, such as a vibrometer 5 operation routine 410, a zero calibration routine 420, and a zero verification routine 430. The storage system can also store statistics such as the mean, standard deviation, and confidence interval.

[0056] The operating routine 410 can determine a mass flow value 412 and a density value 414 based on the sensor signals received by the interface 401. The mass flow value 412 can be a frequency-independent mass flow value, a directly measured mass flow value, etc. For example, as described above, the mass flow rate can be determined using an equation that does not include frequency-dependent values ​​such as frequency or density. The mass flow value 412 can be determined from the sensor signals, such as the time delay between the left and right pickoff sensor signals. The density value 414 can also be determined from the sensor signals, for example, by determining the frequency from one or both of the left and right pickoff sensor signals.

[0057] The zero calibration routine 420 may perform the zero verification described above and store the initial or factory zero as a reference zero flow value 422. As described above, the reference zero flow value 422 may be used to calculate the mass flow value 412. The zero calibration routine 420 may also determine and store a zero stability value as a reference zero stability value 424. Additionally or alternatively, the reference zero flow value 422 and the reference zero stability value 424 may be determined by calibration routines stored and executed on an external device, such as a factory calibration platform that performs the initial calibration of the vibrometer 5.

[0058] The zero verification routine 430 may verify that the reference zero flow value 422 is acceptable, for example, by using the reference zero stability value 424. For example, the zero verification routine 430 may measure the zero flow value under no-flow or zero-flow conditions of the vibrometer 5 and store the measured zero flow value as the measured zero flow value 432. The zero verification routine 430 may determine whether the measured zero flow value 432 is within the reference zero stability value 424.

[0059] Additionally or alternatively, the zero verification routine 430 may determine a bias indicator value 434 for the reference zero flow value 422. The bias indicator value 434 may indicate that the reference zero flow value 422 may cause measurement bias in the mass flow value 412. As described above, the bias indicator value 434 for the reference zero flow value 422 may be composed of a central tendency value and a variance value associated with the measured zero flow value 432. For example, the central tendency value may be the average of multiple difference values ​​between the measured zero flow value 432 and the reference zero flow value 422, and the variance value may be the standard deviation of the multiple difference values ​​about the average.

[0060] The zero verification routine 430 may also select a zero verification criterion. For example, the zero verification routine 430 may select the zero verification criterion based on the characteristics of the fluid contained by the sensor assembly 10. The zero verification criterion may consist of the reference zero stability value 424 and / or other values. For example, as shown in FIG. 4 , a first zero verification criterion 440 may include a first bias indicator confidence threshold 442. Thus, the zero verification routine 430 may determine whether the measured zero flow value 432 is within the reference zero stability value 424 and whether the bias indicator value 434 is within the first bias indicator confidence threshold 442. The first bias indicator confidence threshold 442 may be, for example, a 75% sign ratio, zero, or a dead band around zero if a null hypothesis is used as described above.

[0061] The zero verification routine 430 may also select a second zero verification criterion 450, comprising, for example, a second zero stability value 452 and a second bias indicator confidence threshold 454. The second zero stability value 452 may not be the same as the reference zero stability value 424. For example, the second zero stability value 452 may be less than the reference zero stability value 424. Thus, the second zero stability value 452 may be used when the vibrometer 5 is used in a process that requires a zero stability value that is less than the reference zero stability value 424.

[0062] For example, for an uncustodial transfer of a liquid, the zero verification routine 430 may determine whether the measured zero flow value 432 is within the reference zero stability value 424. For a custodial transfer of a liquid, the zero verification routine 430 may determine whether the measured zero flow value 432 is within the reference zero stability value 424 and the bias indicator value 434 is within a first bias indicator reliability threshold 442. For a custodial transfer of a gas, the zero verification routine 430 may determine whether the measured zero flow value 432 is within a second zero stability value 452 and the bias indicator value 434 is within a first bias indicator reliability threshold 442. These are merely examples, and any suitable range of tolerances or combination of tolerances for the reference zero flow value can be used for any suitable characteristic of the fluid.

[0063] The first and / or second bias indicator confidence thresholds 442, 454 may be user-configurable. For example, a user can set a deadband around zero to achieve a desired zero validation standard for a particular application. Thus, a confidence interval value stored as a variance value of the bias indicator values ​​434, described in more detail below, can be configured by the manufacturer, and a user can configure the first and / or second bias indicator confidence thresholds 442, 454 to be compared to the variance value, or more specifically, the confidence interval in this example. As an example, a manufacturer can set a two-sigma confidence interval value that can be compared to zero (i.e., no deadband) for one application, while for more demanding applications, a user can set a deadband value that, when compared to the two-sigma confidence interval value, is equivalent to a three-sigma confidence interval value compared to zero.

[0064] By referencing the code ratio, a user can set a code ratio value as a bias indicator reliability threshold. The code ratio value may require fewer computing resources than comparing a confidence interval to a dead band to determine whether the bias indicator is sufficiently reliable. The code ratio may also correspond to a confidence interval. For example, a code ratio value of 75% may correspond to approximately 1 sigma or a 68% confidence level. These and other values ​​may be set and stored by a user as first and / or second bias indicator reliability thresholds 442, 454 to which the bias indicator value 434 is compared.

[0065] The processing system 402 may also determine a first or second zero verification reference 440, 450. For example, the processing system 402 may calculate a second zero stability value 452 from the reference zero stability value 424. In one particular example, the second zero stability value 452 may be calculated by multiplying the reference zero stability value 424 by, for example, 0.5, to scale the reference zero stability value 424 to the second zero stability value 452. Additionally or alternatively, the first and / or second bias indicator confidence thresholds 442, 454 may be similarly calculated.

[0066] The ratio used to scale the first or second zero validation criteria 440, 450 may be based on a property of the fluid. For example, the ratio may be the ratio of error bands associated with whether the expected flow rate of the fluid is low or high, whether the fluid is a gas or a liquid, whether the density of the fluid is above or below a density threshold, etc. In one example, the ratio may be determined by dividing the error band associated with a high expected flow rate of the fluid by the error band associated with a low expected flow rate of the fluid. An example of this is described below with reference to FIG. 5.

[0067] FIG. 5 illustrates a graph 500 illustrating the AGA11 standard for tolerance ranges for flow measurements. As shown in FIG. 5, graph 500 includes a measured flow rate axis 510 and a percentage error axis 520. Measured flow rate axis 510 may be in any suitable units, such as kilograms per minute (kg / min). Measured flow rate axis 510 ranges from zero to a maximum flow rate, Qmax. Percent error axis 520 ranges from −1.60 to 1.60, although any suitable range and / or units may be used.

[0068] Graph 500 also includes an error plot 530 illustrating an exemplary error-flow rate relationship for a Coriolis meter. Error plot 530 has an associated repeatability bar that indicates, for each corresponding flow rate, the range within which measurements are expected to fall. As can be seen, error plot 530 decreases as the flow rate increases, significantly improving measurement stability. As can also be seen, as the measured flow rate decreases, the repeatability bar and error increase. The increase in repeatability bar and error may be due to an increased contribution of nonlinear effects to the flow rate measurements. Other error plots may be used, such as those with smaller increases or those in which the error is primarily linear with, for example, a reference zero flow rate value.

[0069] Graph 500 further includes an error limit band 540 having a low flow error limit band 540a and a normal flow error limit band 540b. Low flow error limit band 540a and normal flow error limit band 540b are symmetrical about the zero error rate axis. Low flow error limit band 540a corresponds to the range of flow rates between a minimum flow rate Qmin and a threshold flow rate Qt. Normal flow error limit band 540b is for flow rates between a threshold flow rate Qt and a maximum flow rate Qmax. As can be seen, low flow error limit band 540a has a larger error limit value than normal flow error limit band 540b.

[0070] To meet the AGA11 standard, a Coriolis flow meter, such as the vibrometer 5 described above, can have an error percentage that falls within the error limit band 540. However, because the error limit value of the low flow error limit band 540a is greater than the normal flow error limit band 540b, many users choose not to operate their Coriolis meters at flow rates below the threshold flow rate Qt. As a result, the operating or effective turndown ratio of such a Coriolis flow meter is defined by the threshold flow rate Qt rather than the minimum flow rate Qmin. The error plot 530 may have a non-zero error percentage for various reasons, such as measurement bias associated with the reference zero flow value. For example, in equation [1] above, the zero flow time delay Δt0 may be an inaccurate zero flow value for the Coriolis flow meter. Therefore, the measured mass flow rate

number

[0071] 5, error plot 530 can be improved by reducing the error rate represented by error plot 530. For example, error plot 530 can be shifted closer to the zero error axis by reducing the measurement bias caused by reference zero flow value 422. In addition, other routines, such as a calibration to determine FCF, may compensate for nonlinear contributions to error plot 530 at low flow rates. Thus, by shifting and flattening error plot 530, error plot 530 may fall within a normal flow error limit band 540b up to the minimum flow rate Qmin. As a result, a narrower error limit band can be used for flow rates between the threshold flow rate Qt and the minimum flow rate Qmin.

[0072] Measurement bias associated with a reference zero flow value can be removed by performing a zero calibration, which can be performed in the field by isolating the vibrometer 5 and performing a zero flow value calibration, see FIG. 1. More specifically, the vibrometer 5 can be fluidly isolated such that the flow rate through the vibrometer 5 is zero, and therefore the measured zero flow value can be assumed to represent zero flow.

[0073] The difference between the measured zero flow value and the reference zero flow value may be proportional to the measurement bias caused by an inaccurate reference zero flow value. To compensate for this measurement bias, a new measured zero flow value can replace the reference zero flow value stored in meter electronics 20. However, as can be appreciated, the measured zero flow value may not be perfectly accurate. The following describes a method for determining that the measured zero flow value is a reliable zero flow value and, therefore, an accurate measurement of the zero flow value of sensor assembly 10.

[0074] FIG. 6 illustrates a zero verification graph 600 representing the zero verification of the vibrometer 5. As shown in FIG. 6, the zero verification graph 600 includes a sample axis 610 and a zero flow value axis 620. The sample axis 610 is unitless but is shown as being in the time domain. Thus, each division on the sample axis 610 represents a sample time. The zero flow value axis 620 is shown as being represented in terms of a time delay Δt in units of time, although any suitable zero flow value, such as a phase difference, may be used. The units of the zero flow value axis 620 may be nanoseconds, although any suitable units, such as phase or angle-related units, may be used.

[0075] The zero verification graph 600 also shows a reference zero flow value 630 and a corresponding zero stability value 640. The zero stability value 640 is shown as a tolerance band about the reference zero flow value 630. The zero stability value 640 represents a verification criterion that may serve as a first zero verification criterion. In other words, if all of the measured zero flow values ​​are within the range representing the zero stability value 640, the vibrometer 5 may be considered good for a first application associated with the first zero verification criterion. The first zero verification criterion may be associated with liquid measurements in uncustody transfers.

[0076] The zero verification graph 600 also includes a zero flow value measurement 650, represented by a circular dot. The zero flow value measurement 650 may represent a zero flow value measurement made as described above with reference to FIG. 1 above. As can be seen, the zero flow value measurement 650 is consistently greater than the reference zero flow value 630. Thus, the zero flow value measurement 650 indicates that the reference zero flow value 630 may be causing measurement bias in flow measurements made according to equation [1] above. Also shown is a mean 650a and confidence interval 650b, described in more detail below, determined from the zero flow value measurement 650.

[0077] The bias indicator can prove that the difference between the reference zero flow value 630 and the measured zero flow value 650 is due to an inaccuracy in the reference zero flow value 630. The bias indicator for the reference zero flow value 630 can consist of any value or a value indicative of a new zero flow value that can reduce or eliminate the measurement bias in the flow measurement caused by the reference zero flow value 630. The following description provides examples of bias indicators for the reference zero flow value 630.

[0078] The sign ratio is the ratio of the number of positive or negative values ​​or signs to the total number of values. The sign ratio may be referred to as a positive sign ratio if the counted signs are positive, or as a negative sign ratio if the counted signs are negative. As shown in FIG. 6 , the differences between the multiple zero flow value measurements 650 and the reference zero flow value 630 are all positive values. Therefore, the positive sign ratio of the multiple differences is 100%. The negative sign ratio is 0%. If either sign ratio is greater than the bias indicator confidence threshold, the average value determined from the zero flow value measurements 650 can be used as a new reference zero flow value to reduce or eliminate measurement bias caused by an inaccurate reference zero flow value 630. Additionally or alternatively, the new reference zero flow value can be determined by performing a zero calibration.

[0079] As an example, the bias indicator reliability threshold for the sign ratio may be a predetermined value of 75%. All of the measured zero flow values ​​650 are greater than the reference zero flow value 630. Therefore, as described above, the sign ratio of the difference between the measured zero flow values ​​650 and the reference zero flow value 630 is positive 100%. This is greater than 75%, and therefore the average value 650a calculated from the measured zero flow values ​​650 can be used as the reference zero flow value to reduce or eliminate the measurement bias caused by the reference zero flow value 630.

[0080] Statistical methods that calculate the probability of an outcome can be used to calculate bias indicators in a vibrometer. For example, P statistics and T statistics can be used to test whether a null hypothesis is met for a given data set. Rejecting the null hypothesis does not determine whether a condition exists in the vibrometer, but rather that the absence of the condition is false. For zero validation, the null hypothesis can be defined as "the current zero flow value is the same as the reference zero flow value." If this null hypothesis is disproved, it can be assumed that the current zero flow value is not the same as the reference zero flow value, and therefore, the reference zero flow value is a source of measurement bias in the flow measurement.

[0081] By way of example, in a t-test, the t-value can be calculated using the following formula:

number

number

number

[0082] As mentioned above, the t-test can be used to test the null hypothesis, and in the case of a null test, the sample mean

number

[0083] However, P values ​​may be difficult to calculate with limited computing resources. For example, P values ​​can be calculated on a computer workstation with an operating system and statistical software, but may not be easily calculated on an embedded system. The meter electronics 20 described above may be an embedded system with limited computing resources.

[0084] For this purpose, a confidence interval available with the limited computing resources of the meter electronics 20 can be used instead of a P-value. As a result, the confidence interval can be calculated using built-in code on the meter electronics 20. For example, the meter electronics 20 may have a current zero flow value and a zero standard deviation value stored in two registers. As can be appreciated, the above-mentioned t-value can be calculated using the current zero flow value by using the significance level α and the degrees of freedom. As an example, the significance level α can be set to 0.01, which is a 99% confidence level. The number of zero validation tests can be set to 10. Therefore, the degrees of freedom are determined to be 9. A two-tailed Student's t-value can be calculated from the significance level α and the degrees of freedom using the Student's t-value function as follows:

number

[0085] The standard deviation of the measured zero flow values ​​can be determined. The standard error can also be calculated and is defined as follows:

number

number

number

[0086] In the above example, a 99% confidence level can be used to calculate the confidence interval and compare it to the bias indicator confidence threshold. For example, the confidence interval can be used to test the null hypothesis by determining whether the confidence interval includes 0.0. If the confidence interval includes 0.0, the null hypothesis is not rejected, and zero validation indicates that the reference zero flow value does not cause measurement bias. If the confidence interval does not include 0.0, the null hypothesis is rejected, a zero validation fault is sent, the mean of the zero flow value measurements, 650, is saved as the new reference zero flow value, a new calibration is performed, and so on. Thus, the confidence interval can be used to test the null hypothesis at a desired confidence level.

[0087] In addition to the confidence interval, a bias deadband can also be defined around zero. This bias deadband in a t-test is a value around zero where small biases with small variations do not reject the assumption that would otherwise be rejected in a confidence interval check. Therefore, this bias deadband can be set to a value that reduces the number of false bias indications at the reference zero flow value.

[0088] In the example of a confidence interval compared to zero, the bias deadband is the range around zero, and if zero is not within the confidence interval but part of the bias deadband is within the confidence interval, then the null hypothesis is not rejected. Mathematically, this test can be expressed as whether the mean zero flow value is less than the bias deadband. Alternatively, using the above terminology,

number

[0089] The bias deadband can be implemented alone or in combination with other deadbands. For example, the bias deadband can be implemented in combination with a fluctuation deadband. In one example, the fluctuation deadband is db variation =db bias / t student,99,8 can be determined from, where db variation is the fluctuation deadband. The fluctuation deadband can be compared to the zero flow value standard deviation to determine whether to reject the null hypothesis. In one embodiment, the bias deadband can be compared as described above, and the fluctuation deadband can be compared to the zero flow value standard deviation as follows:

number

number

number

[0090] The reference zero flow value 630 may be updated, replaced, etc. if the bias indicator indicates that the reference zero flow value 630 should be replaced by a zero flow value that can reduce or eliminate the measurement bias caused by the reference zero flow value 630. Thus, the meter electronics 20 may be configured to update or replace the reference zero flow value 630, for example, by storing an average value of the measured zero flow value 650 and initiating a zero calibration routine to determine a new zero flow value, etc. A zero calibration routine that obtains a new reference zero flow value may be advantageous over the measured zero flow value 650 because the zero calibration routine may include additional quality control steps / features. Additionally, additional calibration steps may also be performed, such as recalculating the FCF.

[0091] By reducing or eliminating the measurement bias, along with other routines that reduce or eliminate nonlinear contributions at low flow rates, an improved error plot from error plot 530 shown in FIG. 5 may fall within normal flow error limit band 540b, or even within a tighter error limit band, for flow rates up to the minimum flow rate Q. Thus, the zero verification criteria associated with normal flow error limit band 540b can be used for applications having flow rates below the threshold flow rate Q. As can be seen, this can improve the effective turndown ratio of vibrometer 5 (i.e., increase the ratio between the maximum flow rate Qmax and the minimum flow rate Qmin).

[0092] Certain applications with lower performance requirements may be associated with more stringent zero verification criteria. An example of an application with lower performance requirements is the uncustodial transfer of liquids. Applications or processes with higher performance requirements may be associated with zero verification criteria that include, for example, a zero stability value that is smaller than the zero stability value used in the looser zero verification criteria described above. An example of a high performance application is the custodial transfer of gases, such as the custodial transfer of natural gas at the point of consumption.

[0093] More stringent zero validation criteria may also include a bias indicator confidence threshold for the bias indicator of the reference zero flow value. For example, a central tendency value and a variance value associated with the zero flow value measurement 650 may be determined and compared to the reference zero flow value. In one example, the central tendency value associated with the zero flow value measurement 650 may be the average of the differences between multiple zero flow value measurements 650 and the reference zero flow value. The variance value associated with the zero flow value measurement 650 may be, for example, a confidence interval 650b about the average 650a of the differences between the multiple zero flow value measurements 650 and the reference zero flow value. As described above, the confidence interval 650b may be determined using a confidence level (e.g., 99%, 95%, etc.). The confidence interval 650b may be compared to a bias indicator confidence threshold, which may be zero or a dead zone around zero in the null hypothesis t-test described above.

[0094] The zero verification criteria can be determined by the meter electronics 20 based on the properties of the fluid. For example, the zero verification criteria scale can be determined based on whether the fluid is a gas or a liquid. For example, if the zero stability value 640 pertains to an uncustodial transfer of a liquid, a more stringent zero verification criteria for a custodial transfer of a gas can be calculated by scaling the zero stability value 640 by a zero verification criteria scale of, for example, 0.5, although any suitable value may be used. Other properties of the fluid, such as measured density, can be used to determine the zero verification criteria scale.

[0095] More specifically, the density of the fluid contained in the vibrometer 5 can be measured and compared to a density value threshold. If the measured density is less than the density value threshold, a first zero verification criterion can be selected. If the measured density is greater than the density value threshold, a second zero verification criterion can be selected. The first zero verification criterion may be suitable for higher performance applications, while the second zero verification criterion may be suitable for lower performance applications. The density value thresholds may be selected, entered, chosen, etc., by a user. More density value thresholds may be used. For example, there may be two or more density value thresholds, each defining a density value range associated with an additional zero verification criterion value. Thus, two or more zero verification criteria may be selected.

[0096] One of the zero verification threshold criteria may be stored in memory or scaled from another zero verification criteria. For example, referring to FIG. 5, error limit bands 540 have different values ​​based on the fluid flow rate. More specifically, low flow error limit band 540a has approximately twice the value of normal flow error limit band 540b. As can be appreciated, the zero verification criteria associated with low flow error rate limit 540a may be more or less stringent depending on the particular application, and the value of the zero verification criteria may be proportional to the ratio of low flow error limit band 540a to normal flow error limit band 540b.

[0097] Thus, the zero stability value 640 shown in FIG. 6 can be scaled (e.g., multiplied by the zero verification reference scale) depending on whether the vibrometer 5 is being employed in a higher or lower performance application. For example, if the zero stability value 640 shown in FIG. 6 is associated with the low flow error limit band 540a, the zero stability value 640 can be multiplied by 0.5 in the meter electronics 20 to determine a smaller zero stability value for the reference zero flow value 630. As an example, this may be done to achieve accurate measurement down to lower flow rates within the normal flow error limit band 540b in order to improve the Qt flow rate down to lower flow values, thus expanding the usable flow range of the meter in the application. As can be seen from FIG. 5, the zero verification scale can depend on the expected flow rate of the fluid.

[0098] As discussed above, the zero validation criteria may consist of or include a bias index confidence threshold for a reference zero flow value, such as reference zero flow value 630. The bias index may be compared to the bias index confidence threshold. The bias index may be determined, for example, using a central tendency value and a variance value associated with the zero flow value measurement 650. As shown in FIG. 6, the central tendency value is the mean 650a and the variance value is the confidence interval 650b.

[0099] Additionally or alternatively, appropriate zero verification criteria may be selected based on the characteristics of the fluid in the vibrometer 5. For example, the zero verification criteria may be selected based on a determination of whether the application is a custody transfer of a gas. The selection criteria in this example may be to determine whether the measured density is below a gas density threshold and to determine whether the vibrometer 5 should be used in a custody transfer. If both of these are true, then a more stringent zero verification criteria may be selected.

[0100] As can be appreciated, the selection of the zero verification criteria can be automated. More specifically, the user need only store a value in meter electronics 20 that indicates that vibrometer 5 is being used for a custody transfer. As a result, meter electronics 20 can be configured to determine that vibrometer 5 is measuring a custody transfer liquid and therefore employ a smaller zero stability value for the reference zero flow value during zero verification without determining a bias indicator for the reference zero flow value.

[0101] FIG. 7 illustrates a method 700 for determining a zero verification criterion for zero verification of a vibrometer. As shown in FIG. 7, the method 700 determines a property of a fluid in step 710. The fluid may be contained in a sensor assembly, such as the sensor assembly 10 described above, although any suitable sensor assembly may be used. The method 700 may determine a zero verification criterion value for the sensor assembly in step 720 based on the property of the fluid. The property of the fluid may be a property of the fluid measured while the fluid is contained in the sensor assembly in a non-flowing state. For example, the property of the fluid may be one of the density and phase of the fluid.

[0102] The zero check criterion may be a first zero check criterion determined by multiplying a second zero check criterion by a coefficient. For example, the ratio described above with reference to FIG. 5 may be multiplied by the second zero check criterion to determine the first zero check criterion. This exemplary ratio may be determined based on a first tolerance associated with a first expected flow rate of the fluid and a second tolerance associated with a second expected flow rate of the fluid.

[0103] The zero verification reference value may be one of a bias indicator confidence threshold and a zero stability value for the reference zero flow value. For example, if a bias indicator is used to perform the zero verification, the bias indicator confidence threshold may be used to determine whether the reference zero flow value is likely to include bias that may affect the flow measurement. Additionally or alternatively, the zero stability value may be used to determine whether the measured zero flow value is within the zero stability value.

[0104] Thus, a vibrometer, such as the vibrometer 5 described above, can be configured to measure the flow rate of a fluid using a zero flow rate value. The vibrometer can include a sensor assembly, such as the sensor assembly 10 described above, configured to measure the fluid, and meter electronics 20 communicatively connected to the sensor assembly 10. The meter electronics 20 can be configured to determine a characteristic of the fluid and, based on the characteristic of the fluid, determine a zero validation reference value for the sensor assembly.

[0105] The vibrometer 5, meter electronics 20, and method 700 described above can determine a zero verification reference for zero verification of a vibrometer, such as the vibrometer 5 described above. For example, the vibrometer can include a sensor assembly configured to measure a fluid. As described above, the fluid can be a gas or a liquid and can be used in various processes that may have different tolerances, such as flow measurement tolerances. The different measurement tolerances may be determined from characteristics of the fluid. Accordingly, the vibrometer can also include meter electronics communicatively connected to the sensor assembly. The meter electronics 20 can be configured to determine a characteristic of the fluid and determine a zero verification reference value for the sensor assembly based on the characteristic of the fluid.

[0106] Because the zero verification reference value is determined based on the properties of the fluid, the zero verification reference value may be more appropriate for a given process or application. For example, the zero verification reference value may be associated with a custody transfer of a gas that may have a density value less than a density value threshold. Thus, the zero verification reference value associated with a custody transfer of a gas may be appropriate for a measurement tolerance range for flow rate measurements of the custody transfer of the gas.

[0107] In one example, a zero verification reference value can be determined by multiplying another zero verification reference value by a zero verification reference scale, where the second zero verification reference value is associated with a looser tolerance for the flow measurement. Using the zero verification reference scale can be more efficient and require fewer computing resources than, for example, storing different zero verification reference values ​​for various processes or applications. Thus, a zero verification reference value suitable for a looser tolerance for the flow measurement can be a base zero verification reference value used to calculate other zero verification reference values ​​suitable for tighter tolerances for the measured flow rate.

[0108] 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 present description. Indeed, those skilled in the art will recognize that certain elements of the above embodiments can be combined or deleted in various ways to create further embodiments, and that such further embodiments will fall within the scope and teachings of the present description. It will also be apparent to those skilled in the art that the above-described embodiments can be combined, in whole or in part, to create additional embodiments within the scope and teachings of the present description.

[0109] Thus, while specific embodiments have been described herein for illustrative purposes, those skilled in the art will recognize that various equivalent modifications are possible within the scope of this description. The teachings provided herein may be applied not only to the embodiments described above and shown in the accompanying drawings, but also to other vibrometers, meter electronics methods for determining a zero verification criteria for zero verification of a vibrometer. Accordingly, the scope of the above-described embodiments should be determined by the claims.

Claims

1. 1. A meter electronics (20) for determining a zero verification criterion for zero verification of a vibrometer (5), comprising: an interface (401) communicatively connected to a sensor assembly (10) containing a fluid; a processing system (402) communicatively connected to the interface (401), the processing system (402) configured to determine a characteristic of a fluid and to determine a zero verification reference value for the sensor assembly (10) based on the characteristic of the fluid and a selected zero verification reference; The meter electronics comprises:

2. 2. The meter electronics of claim 1, wherein the processing system configured to determine a characteristic of the fluid comprises the processing system configured to measure a characteristic of the fluid while the fluid is contained within the sensor assembly in a non-flowing state.

3. The meter electronics (20) of claim 1, wherein the fluid property is one of a fluid density and a fluid phase.

4. The meter electronics (20) of claim 1, wherein the processing system (402) configured to determine the zero verification reference value based on the characteristics of the fluid and the selected zero verification criterion comprises the processing system (402) configured to determine a first zero verification reference value by multiplying a second zero verification reference value by a coefficient.

5. 5. The meter electronics of claim 4, wherein the coefficient is a ratio determined based on a first tolerance associated with a first expected flow rate of the fluid and a second tolerance associated with a second expected flow rate of the fluid.

6. The meter electronics (20) of claim 1, wherein the zero verification reference value is at least one of a bias indicator confidence threshold and a zero stability value for the reference zero flow value.

7. 1. A method for determining a zero verification criterion for zero verification of a vibrometer, comprising: containing a fluid within the sensor assembly; determining a property of the fluid; determining a zero verification reference value for the sensor assembly based on the fluid characteristics and a selected zero verification reference; A method comprising:

8. The method of claim 7 , wherein the property of the fluid is measured while the fluid is contained within the sensor assembly in a non-flowing state.

9. The method of claim 7 , wherein the fluid property is one of a density and a phase of the fluid.

10. The method described in claim 7, wherein determining the zero verification reference value based on the characteristics of the fluid and a selected zero verification criterion includes determining a first zero verification reference value by multiplying a second zero verification reference value by a coefficient.

11. 11. The method of claim 10, wherein the coefficient is a ratio determined based on a first tolerance associated with a first expected flow rate of the fluid and a second tolerance associated with a second expected flow rate of the fluid.

12. The method of claim 7 , wherein the zero verification reference value is at least one of a bias indicator confidence threshold and a zero stability value of the reference zero flow value.

13. A vibrometer (5) capable of determining a zero verification criterion for performing zero verification, a sensor assembly (10) containing a fluid; 7. A meter electronics (20) communicatively connected to the sensor assembly (10), the meter electronics (20) being as set forth in any one of claims 1 to 6; A vibrometer (5) comprising:

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