Notch filter for vibration-type flow meter

Abstract

To simplify a drive algorithm or a circuit of a vibration-type meter.SOLUTION: There is provided a meter electronic apparatus 20 having a notch filter 26 configured to perform filter processing for a sensor signal from a sensor assembly 10 of a vibration-type meter. The meter electronic apparatus 20 includes the notch filter 26 communicatively connected to the sensor assembly 10. The meter electronic apparatus 20 is configured to receive, from the sensor assembly 10, a sensor signal composed of a first component in a resonant frequency of the sensor assembly 10 and a second component in a non-resonant frequency, and in the notch filter, to pass the first component with substantially zero phase shift and to substantially attenuate the second component.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The embodiments described below relate to vibratory flow meters, and more particularly, to notch filters for vibratory flow meters. [Background technology]

[0002] Vibratory meters, such as Coriolis flow meters, liquid density meters, gas density meters, liquid viscosity meters, gas / liquid specific gravity meters, gas / liquid relative density meters, gas molecular weight meters, and the like, are commonly known and used to measure fluid properties. Generally, vibratory meters include a sensor assembly and meter electronics. The material in the sensor assembly may be flowing or stationary. Each type of sensor assembly may have unique characteristics that the meter must take into account to achieve optimal performance. For example, some sensor assemblies may require a tubing device that vibrates at a particular displacement level. Other types of sensor assemblies may require special compensation algorithms.

[0003] In addition to performing other functions, the meter electronics typically stores sensor calibration values ​​for the particular sensor assembly being used. For example, the meter electronics may include a reference sensor time period (i.e., the inverse of the reference resonant frequency). The reference sensor time period represents the basic measurement performance of the sensor geometry of the particular sensor assembly measured under reference conditions at the factory. Changes between the sensor time period measured after the vibration meter is installed at a customer site and the reference sensor time period may represent physical changes in the sensor assembly due to coating, erosion, corrosion, or damage to the conduits in the sensor assembly, among other causes. Meter verification or health check tests may detect these changes.

[0004] Meter verification testing is typically performed using a multi-component drive signal, sometimes referred to as a multi-tone drive signal, applied to the sensor assembly. A multi-tone drive signal typically consists of a resonant component, or drive tone, at the resonant frequency of the sensor assembly, and multiple non-resonant components, or test tones, having frequencies away from the frequency of the drive tone. This differs from an approach in which multiple test tones are repeated sequentially. When a sequential tone approach is used, the presence of time changes in the system (e.g., temperature dependent effects, flow changes) can perturb the evaluation of the frequency response of the sensor assembly. A multi-tone drive signal is advantageous because data samples are acquired simultaneously.

[0005] Components associated with the test tone, i.e., non-resonant components, are filtered out so that they are not included in the signal processing loops for flow and density measurements as well as the feedback loop used to provide the drive tone. Typically, a notch filter is used to filter out the non-resonant components before the feedback loop. However, a notch filter can cause a delay or phase shift in the resonant components in the passband portion of the notch filter. This phase delay or shift can cause the frequency of the drive tone to deviate from the resonant frequency of the sensor assembly. Therefore, a notch filter is needed that has a passband that does not cause a delay or phase shift in the resonant components and does not allow the components associated with the test tone to reach the feedback loop. Summary of the Invention

[0006] configured to filter a sensor signal from a sensor assembly of a vibration meter According to one embodiment, the meter electronics includes a notch filter communicatively connected to the sensor assembly. The notch filter has a first component at a resonant frequency of the sensor assembly and a second component at a non-resonant frequency of the sensor assembly. and a second component from the sensor assembly, and a notch filter is provided. is configured to pass the first component with substantially zero phase shift and to substantially attenuate the second component at

[0007] A method for notch filtering a sensor signal of a vibration meter is provided. According to one embodiment, the method includes filtering a first component at a resonant frequency of the sensor assembly and a second component at a non-resonant frequency of the sensor assembly. receiving a sensor signal including a first component at a resonant frequency and a second component at a notch filter; and passing the first component with substantially zero phase shift and substantially attenuating the second component with a notch filter.

[0008] A method for configuring a notch filter for a vibration meter is provided. According to one embodiment, the method includes the steps of providing a notch filter configured to receive a sensor signal having a first component at a resonant frequency of the sensor assembly and a second component at a non-resonant frequency, and performing a phase shift of the first component by passing the first component and substantially attenuating the second component. and adjusting the notch filter so that the difference is qualitatively minimized.

[0009] Aspects According to one embodiment, a sensor signal from a sensor assembly (10) of a vibration meter (5) is flicked. Meter electronics (20) having a notch filter (26) configured to filter includes a notch filter (26) communicatively connected to the sensor assembly (10). The notch filter (26) is configured to filter a first component at a resonant frequency of the sensor assembly (10) and a second component at a non-resonant frequency of the sensor assembly (10). and a second component at a frequency from the sensor assembly. and configured to pass the first component with substantially zero phase shift in the notch filter and to substantially attenuate the second component.

[0010] Preferably, the filter is configured to pass the first component with substantially zero phase shift. The filter (26) is a fixed-point precision filter.

[0011] Preferably, the sensor signal further comprises at least one further non-resonant component; The notch filter is adapted to substantially attenuate at least one further non-resonant component. It is composed of:

[0012] Preferably, the meter electronics (20) is communicatively coupled to the notch filter (26) and determines a saturation value for the sensor assembly (10) based on the first component passed by the notch filter (26). The present invention further comprises a drive circuit (22) configured to generate a multi-tone drive signal of

[0013] According to one aspect, a method for filtering a sensor signal of a vibration meter with a notch filter includes the steps of receiving, at a notch filter, a sensor signal having a first component at a resonant frequency of a sensor assembly and a second component at a non-resonant frequency; filtering, at the notch filter, the first component. passing the component with substantially zero phase shift and substantially attenuating the second component. Includes:

[0014] Preferably, the method further comprises the steps of: filtering the first component with a notch filter that is a fixed-point precision filter; The method further includes passing the signal with substantially zero phase shift.

[0015] Preferably, the sensor signal further comprises at least one further non-resonant component; substantially attenuating at least one further non-resonant component with a notch filter. Further includes:

[0016] Preferably, the method further comprises: determining a sensor average based on a first component passed by the notch filter; The method further includes generating a multi-tone drive signal for the assembly.

[0017] According to one aspect, a method for configuring a notch filter for a vibration meter includes providing a notch filter configured to receive a sensor signal including a first component at a resonant frequency of a sensor assembly and a second component at a non-resonant frequency; passing the first component; and adjusting the notch filter such that the second component is substantially attenuated and the phase shift of the first component is substantially minimized.

[0018] Preferably, the notch filter is arranged such that the phase shift of the first component is substantially minimized. The adjusting step includes adjusting the phase shift of the first component over a frequency range that includes the resonant frequency. The step of adjusting the notch filter so that the difference is substantially minimized.

[0019] Preferably, the notch filter is arranged such that the phase shift of the first component is substantially minimized. The adjusting step is performed such that a phase shift of the first component is substantially minimized at the resonant frequency. The step of adjusting the notch filter so as to

[0020] Preferably, the method further comprises the step of minimizing an error in a fixed-point precision implementation of the notch filter by comparing a first phase shift for a notch filter having a first fixed-point precision and a second phase shift for a notch filter having a second fixed-point precision.

[0021] Preferably, the method further comprises the step of implementing a form of the notch filter in a manner that substantially minimises errors in a fixed-point precision implementation of the notch filter. [Brief description of the drawings]

[0022] Like reference numbers refer to like elements in all figures. It should be understood that the drawings are not necessarily to scale. [Figure 1] A vibrating meter 5 equipped with a notch filter is shown. [Diagram 2] 1 shows a block diagram of a vibratory meter 5 with a notch filter according to an embodiment. [Diagram 3] 3 shows a graph 300 illustrating the phase response of a notch filter in a vibratory meter with significant phase shift. [Figure 4] 4 shows a graph 400 illustrating the phase response of a notch filter in a vibratory meter with significant phase shift. [Diagram 5] 5 illustrates a method 500 for notch filtering a sensor signal from a sensor assembly of a vibratory meter. [Figure 6] 6 illustrates a method 600 for constructing a notch filter for filtering a sensor signal from a sensor assembly of a vibratory meter. [Figure 7] 7 shows a graph 700 illustrating the phase response of a notch filter according to one embodiment. [Figure 8] 8 shows a graph 800 illustrating the phase response of a notch filter according to one embodiment. [Figure 9] 9 shows a graph 900 illustrating the phase response of a notch filter of a vibration meter according to one embodiment. [Figure 10] 1 shows a graph 1000 illustrating the phase response of a notch filter of a vibration meter according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] 1 to 10 and the following description show the best mode of an embodiment of a notch filter for a vibration meter. Specific examples are provided to teach those skilled in the art how to make and use the embodiments. For the purpose of teaching the principles of the invention, some conventional aspects have been simplified or omitted. Those skilled in the art will recognize variations from these examples that are within the scope of the present disclosure. Those skilled in the art will recognize that the features described below can be combined in various ways to form numerous variations of vibration meter notch filters. As a result, the embodiments described below are not limited to the specific examples described below, but only by the claims and their equivalents.

[0024] The notch filter can provide the resonant component to the drive signal generator by removing the non-resonant components while allowing the resonant component to pass. To ensure that the phase shift of the resonant component is zero, the notch filter can be configured to substantially minimize the phase shift of the resonant component. The phase shift can be substantially minimized at or near the resonant frequency, as well as over a frequency range that accounts for a wide range of resonant frequencies. The phase shift can also be substantially minimized, for example, by selecting fixed-point precision values ​​that also reduce the computational burden on the meter electronics. Thus, not having to adjust the phase shift of the resonant component can simplify the drive algorithm or circuitry.

[0025] FIG. 1 shows a vibration meter 5 equipped with a notch filter. As shown in FIG. The vibratory meter 5 includes a sensor assembly 10 and meter electronics 20. The meter 10 is responsive to the mass flow rate and density of the process material. The meter electronics 20 is connected to the path 6. The sensor assembly 10 is connected by leads 100 to provide density, mass flow rate, and temperature information at 100, as well as other information.

[0026] The sensor assembly 10 includes a pair of manifolds 150 and 150', flanges 103 and 103' having flange necks 110 and 110', a pair of parallel conduits 130 and 130', a drive mechanism 180, a resistance temperature detector (RTD) 190, and a pair of pick-off sensors 170l and 170r. The conduits 130 and 130' have two essentially straight inlet legs 131, 131' and outlet legs 134, 134' that converge toward each other at the conduit mounting blocks 120 and 120'. The conduits 130, 130' are bent at two symmetrical locations along their length, The legs 131 of the conduits 130, 130' are essentially parallel throughout their length. The stiffening bars 140 and 140' function to define the central axes W and W' of vibration of each of the conduits 130, 130'. , 131' and 134, 134' are rigidly attached to the conduit mounting blocks 120 and 120'. 1, and these blocks are then rigidly attached to manifolds 150 and 150'. This provides a continuous, closed material pathway through sensor assembly 10.

[0027] When flanges 103 and 103', containing holes 102 and 102', are connected via inlet end 104 and outlet end 104' to process piping (not shown) carrying the process material to be measured, the material enters the meter at inlet end 104 through orifice 101 in flange 103 and passes through manifold 106. The manifold 150 leads to a conduit mounting block 120 having a surface 121. In the step 150, the material is divided and sent through the conduits 130, 130'. Upon exiting, the process material passes into a block 120' having a surface 121' and into a manifold 150'. 102'。 At 102' the two streams are recombined into a single stream and then directed to an outlet end 104' which is connected to process piping (not shown) by a flange 103' with holes 102'.

[0028] The conduits 130, 130' are selected and appropriately mounted in the conduit mounting blocks 120, 120' so as to have substantially the same mass distribution, moment of inertia, and Young's modulus about their respective bending axes WW and W'-W', which pass through the stiffening bars 140, 140'. Because the Young's modulus of the conduit changes with temperature and this change affects flow 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 passing through the RTD 190, is is governed by the temperature of the material passing through the conduit 130'. The differential voltage is used in a known manner by meter electronics 20 to compensate for changes in the elastic modulus of conduits 130, 130' due to changes in the temperature of the conduits. to meter electronics 20.

[0029] Both conduits 130, 130 are rotated by drive mechanism 180 about their respective bending axes W and W'. The flow meter is driven in the opposite direction, in what is called the first antiphase bending mode. The actuator 180 is attached to a magnet attached to the conduit 130' and to the conduit 130. The conduits 130, 130' may comprise any one of a number of well known configurations, such as opposing coils through which an alternating current is passed to vibrate the conduits 130, 130'. This is applied to the drive mechanism 180 via lead wire 185 .

[0030] Meter electronics 20 receives the RTD temperature signal on lead 195 and the left and right sensor signals appearing on lead 100 carrying left and right sensor signals 165l and 165r, respectively. , generates a drive signal appearing on lead 185 to drive mechanism 180 and vibrate conduits 130, 130'. Meter electronics 20 processes the left and right sensor signals and the RTD signal to It calculates the mass flow rate and density of material passing through assembly 10. This information, along with other information, is applied by meter electronics 20 as a signal via path 6.

[0031] FIG. 2 illustrates a block diagram of a vibratory meter 5 with a notch filter according to one embodiment. As shown in FIG. 2, the vibratory meter 5 includes a sensor assembly 10 and meter electronics 20 communicatively connected to the sensor assembly 10. The meter electronics 20 is configured to provide a multi-tone drive signal to the sensor assembly 10. The sensor assembly 10 provides a sensor signal to the meter electronics 20. The meter electronics 20 includes a drive circuit 22 communicatively connected to the sensor assembly 10 and a demodulation filter 24. The demodulation filter 24 is communicatively connected to an FRF estimation unit 25. A notch filter 26 is provided to the drive circuit 22 and the demodulation filter 24. The notch filtered signal is provided to the flow and density measurement module 27, which measures the flow rate and density of the vibratory meter 5. Body flow and / or density are determined.

[0032] The driver circuit 22 receives the resonant component of the sensor signal from the notch filter 26. The driver circuit 22 is configured to generate a multi-tone drive signal for the sensor assembly 10. The multi-tone drive signal is composed of a drive tone and a test tone. The drive tone is based on the resonant component provided by the notch filter 26. For example, the driver circuit 22 may include a feedback circuit that receives the resonant component and generates the drive tone by amplifying the resonant component. Other methods are also possible. Additionally, the driver circuit 22 may generate a test tone at a predetermined frequency away from the resonant frequency.

[0033] The demodulation filter 24 receives the sensor signal from the sensor assembly 10 and removes intermodulation distortion signals that may be present in the sensor signal. For example, the drive tones and test tones of a multi-tone drive signal may cause intermodulation distortion signals in the sensor signal provided by the sensor assembly 10. To remove the intermodulation distortion signals, the demodulation filter 24 may include a demodulation window or passband that includes the frequencies of the drive tones and test tones. Thus, the demodulation filter 24 provides a sensor signal that is comprised of a resonant component and a component corresponding to the test tone while preventing the intermodulation distortion signals from compromising meter verification of the sensor assembly 10. Meter verification involves comparing the test tones and the components corresponding to the test tones to characterize the frequency response of the sensor assembly. This is performed using an FRF estimation unit 25 which

[0034] The notch filter 26 is used during meter verification. Thus, the notch filter 26 may not be used during normal flow and density measurements. Due to the significant frequency changes during normal operation, the coefficients of the notch filter 26 need to be frequently calculated and updated, resulting in additional computational load and potentially undesirable transients. Instead, when meter verification is utilized, the driving tone is sampled to determine the carrier frequency, and the coefficients of the notch filter 26 are calculated based on the determined carrier frequency. The notch filter 26 is then used to increase the test tone to a desired amplitude. During meter verification, the carrier frequency can be monitored, and if the difference between the determined carrier frequency (determined when sampling the driving tone as described above) and the carrier frequency during meter verification is greater than a threshold, the meter verification can be terminated, for example, by removing the notch filter 26 and turning off the test tone.

[0035] To remove the sensor signal components, the notch filter 26 includes multiple stop bands centered at or near the frequency of the test tones. The sensor signal components are attenuated or removed because they are centered at or near the stop band frequencies. The resonant signal is passed because it is in the pass band of the notch filter 26. However, the notch filter may introduce a phase shift into the resonant signal. This phase shift may increase the overall phase delay of the drive feedback, which may increase the overall complexity of the drive algorithm or circuitry that generates the drive tones, while also needing to be corrected for when the notch filter 26 is used for meter verification.

[0036] Figures 3 and 4 show graphs 300, 400 illustrating the phase response of a vibratory meter notch filter with significant phase shift. As shown in Figures 3 and 4, the graphs 300, 400 include a frequency axis 310, 410 and a phase shift axis 320, 420. In Figure 3, the frequency axis 310 ranges from 102 to 108 Hertz (Hz) and the phase shift axis 320 ranges from -180 to 180 degrees. 4, the frequency axis 410 ranges from 104.85 to 105.15 Hz, and the phase shift axis ranges from approximately -39.7 to approximately -37.6 degrees. The graphs 300, 400 also include a phase plot 330. More specifically, FIG. 4 shows an expanded view of the phase plot 330 shown in FIG. , graphs 300 , 400 also include a carrier frequency line 340 and a frequency drift line 350 .

[0037] As can be seen in FIG. 4, the phase plot 330 appears as a straight line from about -37.6 degrees to about -39.7 degrees over the frequency range of about 104.85 to 105.15 Hz. At the indicated carrier frequency of approximately 105.1 Hz, the phase plot 330 is at approximately -38.6 degrees. As a result, the phase shift of the resonant signal passed through the notch filter is approximately 38.6 degrees. The drive algorithm or circuitry must account for the phase shift or delay to ensure that the overall phase delay of the drive algorithm or circuitry is a desired value, for example substantially zero.

[0038] Figure 5 shows a vibration meter with a sensor assembly that is notch filtered. 5 illustrates a method 500 for processing a sensor signal including a first component at a resonant frequency of the sensor assembly and a second component at a non-resonant frequency at a notch filter in step 510. In step 520, the method passes the first component and substantially attenuates the second component at the notch filter, where the first component is passed with substantially zero phase shift.

[0039] The first component corresponds to a drive tone of a multi-component drive signal provided to the sensor assembly. The first component may be at a resonant frequency of the sensor assembly. The filter may have a passband with a phase shift centered about a resonant frequency, as discussed in more detail below with reference to FIGS.

[0040] The second component may be, for example, the time domain of the multi-tone drive signal provided to the sensor assembly 10. The non-resonant component may correspond to one of the two tones. and for the density measurement module 27, the absence of a second component after the notch filter 26. For the FRF estimation unit 25, both the first and second components may be needed. For example, the unfiltered sensor signal may be used to fit a pole-zero or other curve that describes the frequency response of the sensor assembly 10.

[0041] The notch filter configured to pass the first component can include a passband having a frequency range around the first component. For example, the resonant frequency of the sensor assembly can change within a frequency range for various reasons, such as temperature changes, causing the first component to change. As a result, the frequency of the first component may vary within the passband of the notch filter. Nevertheless, the frequency of the first component may pass through the notch filter. When varying within the band, the phase shift of the first component remains essentially zero The notch filter can be constructed to ensure that:

[0042] FIG. 6 shows a filter for filtering a sensor signal from a sensor assembly of a vibration meter. 6 illustrates a method 600 for constructing a notch filter. As shown in FIG. 6, the method 600 includes: In step 610, a notch filter is provided that is configured to receive a sensor signal that includes a first component having a frequency at a resonant frequency of the sensor assembly and a second component. In step 620, the method 600 adjusts the notch filter to pass the first component and substantially attenuate the second component, where a phase shift of the first component is substantially minimized. do.

[0043] Similar to method 500, the first component received in method 600 is a coherent component of the sensor assembly 10. In step 620, the method 600 includes centering the passband of the notch filter at a resonant frequency of the sensor assembly. The notch filter can be tuned to pass the first component by The resonant frequency at which the passband should be centered may be determined, for example, during design of the sensor assembly, during calibration, during operation, etc.

[0044] The notch filter can be adjusted to fit either a finite impulse response filter (FIR) or an infinite impulse This can include adjusting the coefficients of digital filters such as IIR response filters. Such filters are discussed in more detail below with reference to FIG. 10. Additionally, tuning of the notch filter can also include tuning other elements within the notch filter, such as phase shift elements that can compensate for phase shifts due to the design of the notch filter. For example, it may be desirable to introduce delays into the filter to increase the computation speed of the filter, while compensating for the delays with phase shift elements.

[0045] The phase shift of the first component is, for example, zero at the resonant frequency. The phase shift can be minimized by centering the passband of a notch filter designed to match the phase shift of the input signal. The phase shift can also be minimized by minimizing the phase shift of the passband over a range of frequencies. For example, the phase shift can be minimized by minimizing the phase shift of the passband over a range of frequencies. As seen, the phase shift of the passband can vary within the frequency range of the first component.

[0046] As a result, the first component can pass through the notch filter with substantially zero phase shift. However, some variation in the resonant frequency of the sensor assembly is also allowed. The filters and their phase responses are discussed in more detail below with reference to FIGS.

[0047] 7 and 8 show graphs 700, 800 illustrating the phase response of a notch filter according to one embodiment. As shown in FIG. 7 and FIG. 8, the graphs 700, 800 include a frequency axis 710, 810 and a phase shift axis 720, 820. The graph 700 in FIG. 7 is for a relatively high frequency vibratory meter, and the graph 800 shown in FIG. 8 is for a relatively low frequency vibratory meter. In FIG. 7, the frequency axis 710 ranges from about 483.8 Hz to about 484.8 Hz, and the phase shift axis 720 ranges from about -0.125 to about 0.15 degrees. In FIG. 8, the frequency axis 810 ranges from about 75.44 to about 75.64 Hz, and the phase shift axis 820 ranges from about -0.5 to about 0.65 degrees. Phase response plots 730, 830 and carrier frequency lines 740, 840 are also shown in FIG. 7 and FIG. 8. On each side of the carrier frequency line 740, 840 there is a frequency drift line 750, 850.

[0048] As can be seen, the phase response plots 730, 830 are centered substantially at the resonant frequency of the sensor assembly. The illustrated portions of the phase response plots 730, 830 are within the passband of the notch filter. Thus, the passband of the notch filter is centered at the resonant frequency of the sensor assembly 10. As a result, the notch filter passes the resonant component (e.g., the first component described above with reference to methods 500, 600) with substantially zero phase shift. It is possible.

[0049] In addition, the frequency of the resonant component may vary within a range, such as within the range defined by the frequency drift lines 750, 850, and still pass through the notch filter with substantially zero phase shift. For example, with reference to FIG. 7, at about 484 Hz, the phase shift of the notch filter is about 0.1 degrees. At a frequency of about 484.65 Hz, the phase shift of the notch filter is about 0.1 degrees. The offset is approximately -0.1 degrees. As a result, the resonant component can vary or drift within this range without incurring a phase shift of more than 0.1 degrees. Similarly, referring to FIG. 4, the phase shifts range from about 0.4 degrees at about 75.47 Hz to about -0.3 Hz at about 75.61 Hz. These phase shifts are in line with the 38-39 degree phase shifts discussed above with reference to FIG. Thus, a notch filter characterized by the phase response plots 730, 830 can pass a resonant component with substantially zero phase shift over the frequency drift range of the resonant component.

[0050] As can be appreciated, the notch filters characterized by the phase response plots 730, 830 can be further configured or tuned according to the methods 500, 600 to further reduce the phase shift of the first component. For example, the notch filter may have multiple stop bands similar to those shown in FIG. 3 that can be tuned to reduce the phase shift in the pass band of the notch filter. More specifically, the phase shift in the passband of the notch filter can be reduced to reduce the variation of the phase shift in the passband of the notch filter. Thus, referring to FIG. 7, the phase shift range within the range of frequencies defined by the frequency drift line 750 can be further reduced from 0.1 degrees to -0.1 degrees.

[0051] Additionally, as can be appreciated, the signal processing used to implement the notch filter may have a precision associated with each discrete value. For example, a given sample of the sensor signal may be a floating point number or a fixed point number. However, it may be desirable to utilize fixed point numbers to ensure proper and efficient signal processing, for example, by a processor in meter electronics 20. Thus, a given fixed point precision may be minimized while still allowing for a certain amount of precision, for example at a resonant frequency, as described in more detail below with reference to FIGS. 9 and 10. It is also ensured that the phase shift caused by the input signal is substantially zero or substantially minimized.

[0052] 9 and 10 show the phase response of a notch filter in a vibration meter according to one embodiment. Graphs 900 and 1000 are shown. As shown in FIG. 9 and FIG. 10, the graphs 900 and 1000 are 9 and 10, the frequency axes 910, 1010 and the phase shift axes 920, 1020 are included. The frequency axis 910 ranges from 104.85 to 106.15 Hz, and the phase shift axis ranges from -1.8 to 0.2 degrees. Also shown in the graphs 900, 1000 are phase plots 930, 1030. Additionally, the graphs 900, 1000 include a carrier frequency line 940 and a frequency drift line 1050. The carrier frequency line 940 is at approximately 105 Hz.

[0053] As can be seen, the phase plots 930, 1030 are in contrast to the phase plot 330 shown in FIG. As can also be seen, the phase plot 930 shown in FIG. 9 is substantially more disjointed or discontinuous than the phase plot 1040 shown in FIG. 10. The disjointed appearance of the phase plots 930, 1030 may be due to a lack of precision, which may result in, for example, coefficient quantization errors. This is due to the precision of the notch filters employed to filter the sensor signals. More specifically, the real coefficients of, for example, an IIR filter, may be quantized to the nearest number according to the digital representation.

[0054] The notch filter shown in FIG. 9 has 16-bit precision, whereas the notch filter shown in FIG. The notch filter has a precision of 32 bits. As can be seen, the phase processor shown in FIG. The phase plot 930 is not substantially zero or minimized at the carrier frequency of 105 Hz. In contrast, the phase plot 1030 shown in FIG. 10 shows In contrast, the 32-bit precision notch filter is preferable over the 16-bit precision notch filter.

[0055] In addition to the accuracy of the notch filter, the design of the notch filter can affect the phase shift of the notch filter. For example, the results shown in Figures 9 and 10 are due to the following z-propagation: This is realized by a second-order IIR filter that can be expressed as the transfer function H(z), where

[0056]

number

[0057] and ω0 is the center frequency of the stopband, α is the bandwidth parameter.

[0058] This may be an improvement over, for example, the modified second order IIR filter with delayed outputs that may introduce a phase shift as shown in Figures 3 and 4. For four test tones, including the two shown in Figures 3 and 4, the bandwidth coefficient α may be a vector of [0.9999 0.99987 0.9999 0.9999], where each value in the vector corresponds to a test tone frequency at which the stopband frequency ω0 is centered. Thus, the notch filter may be divided into four second order IIR filters. The filter can be constructed as a cascade of filter stages, each with a stopband center frequency located at the test tone frequency and a corresponding bandwidth parameter α from the vector above.

[0059] More specifically, the bandwidth parameter α of each notch filter is adjusted to ensure that the phase shift in the cascade of notch filter stages is zero at the center frequency ω. The above shows how to set four bandwidth parameters for a cascade of notch filter stages. Although the bandwidth parameter α is given, other values ​​can be used in other embodiments. The bandwidth parameter α can be set to substantially zero phase shift of the first passing signal. In these and other embodiments, the bandwidth parameter α is typically given by: Although adjusted once in an offline manner (eg, at design or calibration time), the bandwidth parameter α may also be dynamically adjusted in real time, such as during meter validation.

[0060] Furthermore, once the bandwidth parameter α is calculated, the phase shift should be substantially zero for a wide range of center frequencies. For example, the bandwidth parameter α can be calculated to work over a range of carrier frequencies, i.e., the phase shift at the center frequency ω0 should be substantially zero. We can choose that the shift is not a function of the center frequency ω. This is because the bandwidth This can be made possible by the implementation of these IIR filters, which are realized parametrically with respect to the parameter α and the center frequency ω0. The bandwidth parameter α is The bandwidth parameter α and the center frequency ω0 (and the sample The filter coefficients based on the time (time) can be calculated in real time as the filter is applied. This implementation uses only one set of bandwidth parameters α for a wide range of center frequencies ω This means that it can be used and still have minimal phase shift.

[0061] An alternative form can be used that has a lower fixed-point precision and minimal phase shift. For example, the following formula:

[0062]

number

[0063] It is possible to implement a lattice form of the notch filter described by f notch is the center frequency of the stopband of the notch filter, f sample is the sampling frequency, α is a bandwidth parameter proportional to the bandwidth of the stopband; θ1 is the notch frequency fnotch are parameters related to θ2 is a parameter related to α.

[0064] If the notch filter is implemented in a lattice format, the notch filter can have 16 bits of precision and still provide a tolerable phase shift at the carrier frequency or driving tone frequency. For example, the phase shift of a 16-bit lattice form of a notch filter is shown in Figure 9 for a 16-bit notch filter implemented in a non-lattice format. Rather than the large phase shift shown in FIG. 10, a phase shift similar to that shown in FIG. 10 can be achieved. Thus, by using a particular digital filter type, a desired substantially minimized phase shift, or even zero phase shift, can be achieved with lower fixed-point precision.

[0065] The method 600 may be configured to substantially minimize phase shifts in components of the sensor signal, such as resonant components. By substantially minimizing the phase shift, a driving algorithm or circuit may be considered to have substantially minimized phase delay, or the notch filter may be considered to have substantially zero phase delay. This may simplify the driving algorithm or circuit, thus reducing the design costs of the meter electronics 20. NEW AND IMPROVED METHOD 500 and vibratory meter 5 use a notch filter to attenuate or remove the sensor signal component of the sensor signal provided by sensor assembly 10, thereby preventing the sensor signal from being used to generate the drive signal, thereby reducing the computational load on the processor in meter electronics 20.

[0066] The detailed description of the above embodiments is not intended to be exhaustive of all embodiments that the inventors of the present invention contemplate within the scope of the present specification. Indeed, those skilled in the art will appreciate that certain elements of the above-described embodiments may be combined in various ways or removed to produce further embodiments that are within the scope and teachings of the present specification. It will also be apparent to those skilled in the art that the above-described embodiments may be combined in whole or in part to produce further embodiments within the scope and teachings of the present specification.

[0067] 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 the present disclosure. The teachings presented herein are applicable to other notch filters of vibration meters, in addition to the embodiments described above and illustrated in the accompanying drawings. Thus, the scope of the above-described embodiments should be determined from the claims that follow.

Claims

1. The sensor signal from the sensor assembly (10) of the vibration meter (5) is filtered.

1. A meter electronics system having a notch filter configured as follows: the notch filter (26) is communicatively connected to the sensor assembly (10); receiving a sensor signal from the sensor assembly (10), the sensor signal comprising a first component at a resonant frequency of the sensor assembly (10) and a second component at a non-resonant frequency; Passing the first component with substantially zero phase shift and substantially attenuating the second component by the notch filter. The meter electronics (20) are configured as follows:

2. the notch configured to pass the first component with substantially zero phase shift.

2. The meter electronics of claim 1, wherein the filter is a fixed-point precision filter.

3. The sensor signal further comprises at least one additional non-resonant component, The filter (26) is adapted to substantially attenuate the at least one further non-resonant component. The meter electronics (20) of claim 1 or 2, further configured as follows:

4. a multi-tone drive signal for the sensor assembly based on the first component passed by the notch filter; A drive circuit (22) configured to generate a The meter electronics (20) of any one of claims 1 to 3, further comprising:

5. 1. A method for filtering a sensor signal of a vibration meter with a notch filter, comprising the steps of: receiving a sensor signal at the notch filter, the sensor signal having a first component at a resonant frequency of the sensor assembly and a second component at a non-resonant frequency; the notch filter passes the first component with substantially zero phase shift; substantially attenuating the second component; The method includes:

6. The notch filter is a fixed-point precision filter, and the first component is substantially zeroed. With a phase shift of 6. The method of claim 5, further comprising:

7. the sensor signal further comprising at least one additional non-resonant component; The method comprises: The notch filter substantially attenuates the at least one further non-resonant component. Steps to take 7. The method of claim 5 or 6, further comprising:

8. for the sensor assembly based on the first component passed by the notch filter. generating a multi-tone drive signal for The method of any one of claims 5 to 7, further comprising:

9. 1. A method for setting a notch filter for a vibration meter, comprising the steps of: providing the notch filter configured to receive a sensor signal having a first component at a resonant frequency of a sensor assembly and a second component at a non-resonant frequency; Passing the first component and substantially attenuating the second component and varying the phase of the first component adjusting the notch filter such that the shift is substantially minimized; The method includes:

10. Adjusting the notch filter such that a phase shift of the first component is substantially minimized. The step of determining whether the phase shift of the first component is greater than or equal to the resonant frequency is performed over a frequency range including the resonant frequency.

10. The method of claim 9, comprising adjusting the notch filter such that a difference between the first and second inputs is substantially minimized.

11. Adjusting the notch filter such that a phase shift of the first component is substantially minimized. The step of: substantially minimizing the phase shift of the first component at the resonant frequency.

11. The method according to claim 9 or 10, further comprising adjusting the notch filter so as to method.

12. A first phase shift for a notch filter having a first fixed-point precision and a second fixed By comparing the second phase shift for a notch filter with fractional precision minimizing an error in a fixed-point precision implementation of the notch filter. The method according to any one of claims 9 to 11, further comprising:

13. implementing a form of the notch filter to substantially minimize errors in a fixed-point precision implementation of the notch filter. The method according to any one of claims 9 to 12, further comprising:

Images