Notch filter for vibrating flow meter
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- MICRO MOTION INC
- Filing Date
- 2024-10-01
- Publication Date
- 2026-06-05
Smart Images
Figure 0007870811000003 
Figure 0007870811000004 
Figure 0007870811000005
Abstract
Description
Technical Field
[0001] The embodiments described below relate to a vibratory flow meter, and more particularly, to a notch filter for a vibratory flow meter.
Background Art
[0002] Vibratory meters such as, for example, 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, etc. are generally known and are used for measuring fluid properties. Generally, a vibratory meter includes a sensor assembly and meter electronics. The substance within the sensor assembly may be flowing or stationary. Each type of sensor assembly may have unique characteristics and the meter must consider such characteristics in order to achieve optimal performance. For example, some sensor assemblies may require a tube device that vibrates at a specific 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 can include a reference sensor time period (i.e., the reciprocal of the reference resonance frequency). The reference sensor time period represents the basic measurement performance of the sensor geometry of a particular sensor assembly measured under reference conditions at the factory. Changes between the sensor time period measured after the vibratory meter has been installed at the customer's site and the reference sensor time period can represent physical changes in the sensor assembly due to, among other causes, fouling, erosion, corrosion, or damage of the conduit within the sensor assembly. Meter verification or integrity tests can detect these changes.
[0004] Meter verification tests are typically performed using a multi-component drive signal, sometimes called 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 sensor assembly's resonant frequency, and multiple non-resonant components, or test tones, with frequencies far removed from the drive tone frequency. This differs from methods where multiple test tones are repeated sequentially. When the sequential tone method is used, the presence of time-dependent changes in the system (e.g., temperature-dependent effects, flow changes) can disrupt the evaluation of the sensor assembly's frequency response. Multi-tone drive signals are advantageous because data samples are acquired simultaneously.
[0005] Components related to the test tone, i.e., non-resonant components, are filtered out so that they do not enter the signal processing loop for flow rate and density measurement, or the feedback loop used to generate the drive tone. Typically, a notch filter is used to filter out non-resonant components before the feedback loop. However, a notch filter can cause a delay or phase shift in the resonant components within 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 required that does not cause a delay or phase shift in the resonant components and has a passband that prevents components related to the test tone from reaching the feedback loop. [Overview of the Initiative]
[0006] It is configured to filter the sensor signal from the sensor assembly of a vibrating meter. A meter electronic device having a notch filter is provided. According to one embodiment, the meter electronic device comprises a notch filter communicably connected to a sensor assembly. The notch filter has a first component at the resonant frequency of the sensor assembly and a non-resonant frequency. The sensor signal, consisting of the second component, is received from the sensor assembly and a notch filter is applied. The device is configured to allow the first component to pass through with a substantially zero phase shift and to substantially attenuate the second component.
[0007] A method is provided for filtering the sensor signal of a vibratory meter with a notch filter. According to one embodiment, this method filters a first component at the resonant frequency of the sensor assembly and a non- The step of receiving the sensor signal, which includes a second component at the resonant frequency, with a notch filter. The process includes the steps of passing the first component through a notch filter with a substantially zero phase shift and substantially attenuating the second component.
[0008] A method for setting a notch filter for a vibratory meter is provided. According to one embodiment, the method includes the steps of: preparing a notch filter configured to receive a sensor signal including a first component at the resonant frequency of the sensor assembly and a second component at a non-resonant frequency; and allowing the first component to pass through, substantially attenuating the second component, and reducing the phase shift of the first component. The process includes the step of adjusting the notch filter so that it is qualitatively minimized.
[0009] manner According to one embodiment, the sensor signal from the sensor assembly (10) of the vibrating meter (5) is transmitted A meter electronic device (20) having a notch filter (26) configured for filtering includes a notch filter (26) that is communicatively connected to a sensor assembly (10). The notch filter (26) filters a first component at the resonant frequency of the sensor assembly (10) and a non-resonant component. A sensor signal consisting of a second component in frequency is received from the sensor assembly (10). The notch filter is configured to allow the first component to pass through with virtually zero phase shift and to substantially attenuate the second component.
[0010] Preferably, the noise converter is configured to allow the first component to pass through with a substantially zero phase shift. The 26 filter is a fixed-point precision filter.
[0011] Preferably, the sensor signal is further composed of at least one additional non-resonant component. The notch filter is designed to substantially attenuate at least one additional non-resonant component. It is composed of the following.
[0012] Preferably, the meter electronic equipment (20) is communicably connected to the notch filter (26) and, based on the first component passed through the notch filter (26), for the sensor assembly (10) The system further includes a drive circuit (22) configured to generate a multi-tone drive signal.
[0013] According to one embodiment, a method for filtering the sensor signal of a vibrating meter with a notch filter includes the steps of receiving a sensor signal with a notch filter that includes a first component at the resonant frequency of the sensor assembly and a second component at a non-resonant frequency, and using the notch filter to filter the first component A step in which the first component is passed through with virtually zero phase shift, and the second component is substantially attenuated. This includes.
[0014] Preferably, this method uses a notch filter, which is a fixed-point precision filter, to perform the first action This further includes passing the minutes with a phase shift of virtually zero.
[0015] Preferably, the sensor signal is further composed of at least one additional non-resonant component. The step of substantially attenuating at least one further non-resonant component with a notch filter It also includes.
[0016] Preferably, this method uses a sensor based on the first component that has passed through the notch filter. It further includes the step of generating a multi-tone drive signal for assembly.
[0017] According to one aspect, a method of setting a notch filter of a vibratory meter is configured to receive a sensor signal including a first component at the resonance frequency of the sensor assembly and a second component at a non-resonance frequency, the step of providing a notch filter, passing the first component, substantially attenuating the second component, and adjusting the notch filter so that the phase shift of the first component is substantially minimized.
[0018] Preferably, the notch filter is adjusted so that the phase shift of the first component is substantially minimized. The step of adjusting includes adjusting the notch filter so that the phase shift of the first component is substantially minimized over a frequency range including the resonance frequency.
[0019] Preferably, the notch filter is adjusted so that the phase shift of the first component is substantially minimized. The step of adjusting includes adjusting the notch filter so that the phase shift of the first component is substantially minimized at the resonance frequency.
[0020] Preferably, the method further includes minimizing the error in the implementation of the fixed-point precision 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 includes implementing the form of the notch filter so as to substantially minimize the error in the implementation of the fixed-point precision of the notch filter. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The same reference number represents the same element in all drawings. It should be understood that drawings are not necessarily on a proportional scale. [Figure 1] The image shows a vibrating meter 5 equipped with a notch filter. [Figure 2] This shows a block diagram of a vibratory meter 5 equipped with a notch filter according to one embodiment. [Figure 3] Graph 300 shows the phase response of a notch filter in a vibrating meter, which exhibits a significant phase shift. [Figure 4] Graph 400 shows the phase response of a notch filter in a vibrating meter, which exhibits a significant phase shift. [Figure 5] This shows a method 500 for filtering sensor signals from a vibrating meter's sensor assembly using a notch filter. [Figure 6] This document illustrates a method 600 for configuring a notch filter to filter sensor signals from a sensor assembly of a vibrating meter. [Figure 7] Graph 700 shows the phase response of a notch filter according to one embodiment. [Figure 8] Graph 800 shows the phase response of a notch filter according to one embodiment. [Figure 9] Graph 900 shows the phase response of a notch filter in a vibrating meter according to one embodiment. [Figure 10] Graph 1000 shows the phase response of a notch filter in a vibrating meter according to one embodiment. [Modes for carrying out the invention]
[0023] Figures 1 to 10 and the following description show the best-case configuration of a notch filter embodiment for a vibrating meter. Specific examples are given to instruct those skilled in the art on how to create and use the invention. For the purpose of teaching the principles of the present invention, some conventional embodiments have been simplified or omitted. Those skilled in the art will be able to understand the variations from these examples that are included within the scope of this specification. Those skilled in the art will understand that the features described below can be combined in various ways to form numerous variations of notch filters for vibrating meters. As a result, the embodiments described below are not limited to the specific examples described below, but are limited only by the claims and their equivalents.
[0024] A notch filter can supply resonant components to a drive signal generator by removing non-resonant components while allowing resonant components to pass through. To ensure that the phase shift of the resonant components is zero, the notch filter can be configured to substantially minimize the phase shift of the resonant components. The phase shift can be substantially minimized over a frequency range considering the resonant frequency or its vicinity, as well as a wide range of resonant frequencies. Alternatively, the phase shift can be substantially minimized by selecting a fixed-point precision value, which also reduces the computational load on meter electronics, for example. Therefore, the drive algorithm or circuit can be simplified by eliminating the need to adjust the phase shift of the resonant components.
[0025] Figure 1 shows a vibrating meter 5 equipped with a notch filter. As shown in Figure 1, The vibration meter 5 comprises a sensor assembly 10 and meter electronic equipment 20. The bri 10 responds to the mass flow rate and density of the process material. The meter electronic equipment 20 is located along path 6. The sensor assembly 10 is connected by lead wires 100 to provide information on density, mass flow rate, and temperature, and to provide further 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 in the conduit mounting blocks 120 and 120'. The conduits 130, 130' bend at two symmetrical positions along their length, and they They are essentially parallel throughout their entire length. Reinforcing bars 140 and 140' function to define the central axes W and W' of vibration of each conduit 130, 130'. Legs 131 of conduit 130, 130' ,131' and 134,134' are firmly attached to conduit mounting blocks 120 and 120'. These blocks are then firmly attached to manifolds 150 and 150'. This provides a continuous, closed path for material through the sensor assembly 10.
[0027] When flanges 103 and 103', which have 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 inlet end 104 of the meter through the orifice 101 of flange 103 and into the manifold It passes through pipe 150 and is led to conduit mounting block 120 having surface 121. Manifold At point 150, the substance is divided and transported through conduits 130, 130'. Upon exiting, the process material is directed to block 120' and manifold 150' having surface 121'. The flows then merge again to form a single flow, which is then sent to an outlet end 104' connected to process piping (not shown) by a flange 103' having a hole 102'.
[0028] The conduits 130, 130' are selected such that their mass distribution, moment of inertia, and Young's modulus are substantially the same around their respective bending axes WW and W'-W', and are properly mounted to the conduit mounting blocks 120, 120'. These bending axes pass through the reinforcing bars 140, 140'. Since the Young's modulus of the conduit changes with temperature, and this change affects the calculation of flow rate and density, the RTD190 is attached to the conduit 130' and the temperature of the conduit 130' is continuously measured. The temperature of the conduit 130', and therefore the voltage that appears across the RTD190 at a given current passing through the RTD190 This is governed by the temperature of the substance passing through conduit 130'. The temperature observed at both ends of RTD190 The residual voltage is used in a well-known manner by the meter electronic equipment 20 to compensate for the change in the elastic modulus of the conduits 130, 130' due to the change in the temperature of the conduits. The RTD190 is connected by the lead wire 195. This is then connected to the meter electronic device 20.
[0029] Both conduits 130, 130 are driven by the drive mechanism 180 around their respective bending axes W and W'. And in the opposite direction, it is driven in the so-called first reverse-phase bending mode of the flow meter. The moving mechanism 180 has a magnet attached to the conduit 130', and is attached to the conduit 130, both It may include any one of many well-known configurations, such as opposing coils through which alternating current is passed to vibrate conduits 130 and 130'. A suitable drive signal is provided by the meter electronic equipment 20. This is then applied to the drive mechanism 180 via lead wire 185.
[0030] The meter electronic equipment 20 receives the RTD temperature signal on lead wire 195 and the left and right sensor signals appearing on lead wires 100 that carry the left and right sensor signals 165l and 165r, respectively. The meter electronics 20 processes the left and right sensor signals and the RTD signal to drive the mechanism 180 and generate a drive signal that appears on the lead wire 185 to vibrate the conduits 130 and 130'. The mass flow rate and density of the substance passing through assembly 10 are calculated. This information, along with other information, is applied as a signal via path 6 by meter electronic equipment 20.
[0031] Figure 2 shows a block diagram of a vibratory meter 5 with a notch filter according to one embodiment. As shown in Figure 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 supply a multitone drive signal to the sensor assembly 10. The sensor assembly 10 brings the sensor signal to the meter electronics 20. The meter electronics 20 includes a drive circuit 22 and a demodulation filter 24 communicatively connected to the sensor assembly 10. The demodulation filter 24 is communicatively connected to an FRF estimation unit 25. The notch filter 26 is connected to the drive circuit 22 and It is communicatively connected to the flow rate and density measurement module 27. The signal processed by the notch filter is sent to the flow rate and density measurement module 27, and the flow within the vibrating meter 5 The body's flow rate and / or density are determined.
[0032] The drive circuit 22 receives the resonant component of the sensor signal from the notch filter 26. The drive circuit 22 is configured to generate a multi-tone drive signal for the sensor assembly 10. The multi-tone drive signal consists 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 drive 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. Furthermore, the drive circuit 22 can 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 any intermodulation distortion signals that may be present in the sensor signal. For example, the drive tone and test tone of a multi-tone drive signal may introduce intermodulation distortion signals into 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 tone and test tone. Thus, the demodulation filter 24 provides a sensor signal consisting of a resonant component and a component corresponding to the test tone, while preventing the meter verification of the sensor assembly 10 from being impaired by the intermodulation distortion signals. Meter verification reveals the characteristics of the frequency response of the sensor assembly by comparing the test tone with the component corresponding to the test tone. This is performed using the FRF estimation unit 25.
[0034] The notch filter 26 is used during meter verification. Therefore, the notch filter 26 may not be used during normal flow and density measurements. Due to the fairly large frequency changes in normal operation, the coefficients of the notch filter 26 need to be calculated and updated frequently, resulting in an additional computational load and potentially causing undesirable transients. Instead, when meter verification is used, a drive 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, and the test tone is amplified to the desired amplitude. During meter verification, the carrier frequency can be monitored, and if the difference between the determined carrier frequency (determined when the drive tone is sampled as described above) and the carrier frequency during meter verification is greater than a threshold, the meter verification can be terminated, for example, by disabling the notch filter 26 and turning off the test tone.
[0035] To remove the sensor signal component, the notch filter 26 includes multiple stopbands centered around or near the frequency of the test tone. Because the sensor signal component is concentrated at or near the frequencies of the stopbands, it is attenuated or removed. The resonant signal passes through because it is in the passband of the notch filter 26. However, the notch filter may cause a phase shift in 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 circuit that generates the drive tone, while the phase shift may also need to be compensated for when the notch filter 26 is used for meter verification.
[0036] Figures 3 and 4 show graphs 300 and 400 illustrating the phase response of a notch filter in a vibrating meter with a significant phase shift. As shown in Figures 3 and 4, graphs 300 and 400 include frequency axes 310 and 410 and phase shift axes 320 and 420. In Figure 3, the frequency axis 310 is in the range of 102 to 108 Hz, and the phase shift axis 320 is in the range of -180 to 180 degrees. In Figure 4, the frequency axis 410 is in the range of 104.85 to 105.15 Hz, and the phase shift axis is in the range of approximately -39.7 to approximately -37.6 degrees. Graphs 300 and 400 also include the phase plot 330. More specifically, Figure 4 shows an enlarged view of the phase plot 330 shown in Figure 3. Graphs 300 and 400 also include carrier frequency lines 340 and frequency drift lines 350.
[0037] As seen in Figure 4, the phase plot 330 appears as a straight line from approximately -37.6 degrees to approximately -39.7 degrees over a frequency range of approximately 104.85 to 105.15 Hz, due to the carrier frequency line 340. At the carrier frequency of approximately 105.1 Hz shown, phase plot 330 is at approximately -38.6 degrees. As a result, the phase shift of the resonant signal that has passed through the notch filter is approximately 38.6 degrees. The drive algorithm or circuit must take phase shift or delay into account and ensure that the overall phase delay of the drive algorithm or circuit is a desired value, such as substantially zero.
[0038] Figure 5 shows the sensor signal from the sensor assembly of the vibrating meter being filtered with a notch filter. Method 500 for processing is shown. As shown in Figure 5, Method 500 receives a sensor signal in step 510, which includes a first component at the resonant frequency of the sensor assembly and a second component at a non-resonant frequency, through a notch filter. In step 520, Method passes the first component and substantially attenuates the second component in the notch filter, where the first component passes with substantially zero phase shift.
[0039] The first component corresponds to the drive tone of the multi-component drive signal supplied to the sensor assembly. It may be a resonant signal. The first component may be at the resonant frequency of the sensor assembly. The cross filter may have a passband with a phase shift around the resonant frequency, as will be discussed in more detail below with reference to Figures 7 and 8.
[0040] The second component is, for example, the multitone drive signal supplied to the sensor assembly 10. It may be a non-resonant component corresponding to one of the tones. Drive circuit 22 and flow rate For the density measurement module 27, the absence of a second component after the notch filter 26 is important. This is desirable. For the FRF estimation unit 25, both the first and second components may be necessary. For example, an unfiltered sensor signal might be used to fit a curve, such as a pole zero, that describes the frequency response of the sensor assembly 10.
[0041] A notch filter configured to allow a first component to pass through may include a passband having a frequency range around the first component. For example, the resonant frequency of a sensor assembly may change within a certain frequency range due to various reasons such as temperature changes, thereby altering the first component. It is possible that, as a result, the frequency of the first component changes within the passband of the notch filter. It is possible that the notch filter will pass the frequency of the first component. The phase shift of the first component remains virtually zero when it changes within the bandwidth. It can be configured to guarantee this. The method for configuring a notch filter is described below.
[0042] Figure 6 shows the filtering of the sensor signal from the sensor assembly of the vibrating meter. This shows a method 600 for configuring a notch filter. As shown in Figure 6, method 600 is... Step 610 provides a notch filter configured to receive a sensor signal containing a first component having a frequency at the resonant frequency of the sensor assembly and a second component. In step 620, method 600 adjusts the notch filter to allow the first component to pass through and substantially attenuate the second component, where the phase shift of the first component is substantially minimized. ru.
[0043] Similar to method 500, the first component received in method 600 is a common component of the sensor assembly 10. The first component may be at the vibration frequency, and the second component may be at the non-resonant frequency. In step 620, method 600 aligns the center of the passband of the notch filter with the resonant frequency of the sensor assembly. By doing so, the notch filter can be adjusted to allow the first component to pass through. The resonant frequency at which the center of the passband should be located can be determined, for example, during the design, calibration, and operation of the sensor assembly.
[0044] The notch filter can be adjusted using a finite impulse response filter (FIR) or an infinite impulse filter. This may include adjusting the coefficients of digital filters such as response filters (IIRs). Such filters are discussed in more detail below with reference to Figure 10. Furthermore, tuning a notch filter can also include tuning other elements within the notch filter, such as phase shift elements that can compensate for phase shifts resulting from the notch filter's design. For example, it may be desirable to introduce a delay into the filter to increase its computational speed, while compensating for the delay with a phase shift element.
[0045] The phase shift of the first component is, for example, zero at the resonant frequency. Phase shift can be minimized by positioning the center of the passband of a notch filter designed to do so. Phase shift can also be minimized by minimizing the phase shift of the passband over a certain frequency range. For example, as described above with reference to Method 500. Thus, 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 virtually zero phase shift. On the other hand, a certain degree of variation in the resonant frequency of the sensor assembly is also acceptable. Typical notchf The filters and their phase responses will be discussed in more detail below with reference to Figures 7 and 8.
[0047] Figures 7 and 8 show graphs 700 and 800 illustrating the phase response of a notch filter according to one embodiment. As shown in Figures 7 and 8, graphs 700 and 800 include frequency axes 710 and 810 and phase shift axes 720 and 820. Graph 700 in Figure 7 relates to a relatively high-frequency vibratory meter, and graph 800 shown in Figure 8 relates to a relatively low-frequency vibratory meter. In Figure 7, the frequency axis 710 is in the range of approximately 483.8 Hz to approximately 484.8 Hz, and the phase shift axis 720 is in the range of approximately -0.125 to approximately 0.15 degrees. In Figure 8, the frequency axis 810 is in the range of approximately 75.44 to approximately 75.64 Hz, and the phase shift axis 820 is in the range of approximately -0.5 to approximately 0.65 degrees. Figures 7 and 8 also show phase response plots 730 and 830 and carrier frequency lines 740 and 840. On each side of the carrier frequency lines 740 and 840, there are frequency drift lines 750 and 850.
[0048] As can be seen, the phase response plots 730 and 830 have their centers located substantially at the resonant frequency of the sensor assembly. The illustrated portions of the phase response plots 730 and 830 are within the passband of the notch filter. Therefore, the center of the passband of the notch filter is located at the resonant frequency of the sensor assembly 10. As a result, the notch filter allows the resonant component (e.g., the first component described above with reference to methods 500 and 600) to pass through with substantially zero phase shift. It is possible.
[0049] In addition, the frequency of the resonant component may vary within the range defined by the frequency drift lines 750 and 850, but it can still pass through the notch filter with virtually zero phase shift. For example, referring to Figure 7, at approximately 484 Hz, the phase shift of the notch filter is approximately 0.1 degrees. At a frequency of approximately 484.65 Hz, the phase shift of the notch filter The pitch is approximately -0.1 degrees. As a result, the resonant component can change or drift within this range without causing a phase shift of more than 0.1 degrees. Similarly, see Figure 8. The phase shift ranges from approximately 0.4 degrees at approximately 75.47 Hz to approximately -0.3 Hz at approximately 75.61 Hz. These phase shifts are the same as the 38-39 degree phase shift mentioned above, refer to Figure 4. It is significantly smaller than that of the notch filter. Therefore, a notch filter featuring phase response plots 730, 830 can pass resonant components with virtually zero phase shift over the frequency drift range of the resonant components.
[0050] As can be understood, the notch filter, characterized by phase response plots 730 and 830, can be further configured or adjusted according to methods 500 and 600 to further reduce the phase shift of the first component. This is possible. For example, a notch filter can be adjusted to reduce the phase shift in the passband of the notch filter, and it can have multiple stopbands similar to the stopband shown in Figure 3. It is possible to reduce the phase shift in the passband of the notch filter, thereby reducing the variation in the phase shift in the passband of the notch filter. Thus, referring to Figure 7, the phase shift range within the frequency range defined by the frequency drift line 750 can be further reduced from 0.1 degrees to -0.1 degrees.
[0051] Furthermore, as can be understood, the signal processing used to implement the notch filter may have accuracy relative to 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 use a fixed-point number to ensure appropriately efficient signal processing by, for example, the processor of the meter electronic equipment 20. Thus, while a certain fixed-point precision can be minimized, as will be explained in more detail below with reference to Figures 9 and 10, for example, at the resonant frequency... It is also guaranteed that the phase shift is substantially zero or substantially minimized.
[0052] Figures 9 and 10 show the phase response of a notch filter in a vibrating meter according to one embodiment. Graphs 900 and 1000 are shown. As shown in Figures 9 and 10, Graphs 900 and 1000 are, Includes frequency axes 910, 1010 and phase shift axes 920, 1020. In Figures 9 and 10, frequency The 910 Hz frequency axis is in the range of 104.85 to 106.15 Hz, and the phase shift axis is in the range of -1.8 to 0.2 degrees. Graphs 900 and 1000 also show phase plots 930 and 1030. Furthermore, graphs 900 and 1000 also include the carrier frequency line 940 and the frequency drift line 1050. The carrier frequency line 940 is at approximately 105 Hz.
[0053] As you can see, phase plots 930 and 1030 are opposite to phase plot 330 shown in Figure 4. In fact, it is not a straight line. As can be seen, the phase plot 930 shown in Figure 9 is substantially more disjointed or discontinuous than the phase plot 1040 shown in Figure 10. The disjointed appearance of phase plots 930 and 1030 may be due to, for example, coefficient quantization errors. This is due to the precision of the notch filter used in filtering the signal. More specifically, for example, the real coefficients of an IIR filter can be quantized to the nearest digital representation.
[0054] The notch filter shown in Figure 9 has 16 bits of precision, whereas the one shown in Figure 10 The notch filter has 32-bit precision. As can be seen, the phase phase shown in Figure 9 Lot 930 is not substantially zero or minimized at a carrier frequency of 105 Hz. In contrast, phase plot 1030 shown in Figure 10 is not minimized at a carrier frequency of 105 Hz. At approximately -0.1 degrees, this is practically zero or minimized. Therefore, a 32-bit precision notch filter is preferable to a 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 as follows: This is implemented using a second-order IIR filter that can be expressed as the function H(z), where
[0056]
number
[0057] And, ω0 is the center frequency of the stopband, α is the bandwidth parameter.
[0058] This could be an improvement over a modified version of a second-order IIR filter with a delayed output that can produce a phase shift, as shown in Figures 3 and 4. For four test tones, including the two tones shown in Figures 3 and 4, the bandwidth coefficient α can be a vector [0.9999 0.99987 0.9999 0.9999]. That is, each value in the vector corresponds to the test tone frequency where the center of the stopband frequency ω0 is located. Thus, the notch filter can be modified using four second-order IIR filters. It can be constructed as a cascade of Luta stages, each having a stopband center frequency located at the test tone frequency and a corresponding bandwidth parameter α from the above vector.
[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 ω0. This is possible. The above describes four bandwidth parameters for a cascade of notch filter stages. While a value of -α is given, other values can be used in other embodiments. The above bandwidth parameter α can substantially reduce the phase shift of the first pass-through signal to zero. In these embodiments and other embodiments, the bandwidth parameter α is typically, The bandwidth parameter α is adjusted only once offline (for example, during design or calibration), but it can also be dynamically adjusted in real time, such as during meter verification.
[0060] Furthermore, once the bandwidth parameter α is calculated, the phase shift needs to be virtually zero over a wide range of center frequencies. For example, the bandwidth parameter α should function over a range of carrier frequencies, i.e., the phase at center frequency ω0. The shift can be chosen so that it is not a function of the center frequency ω0. This affects the bandwidth. This can be made possible by implementing these IIR filters parametrically with respect to the parameter α and the center frequency ω0. The bandwidth parameter α is the same as the center frequency ω0. It does not need to change accordingly. Bandwidth parameter α and center frequency ω0 (and sample Filter coefficients based on time can be calculated in real time when the filter is applied. This implementation uses only one set of bandwidth parameters α for a wide range of center frequencies ω0. It can be used, and the phase shift remains minimal.
[0061] Another form can be used that minimizes phase shift with lower fixed-point precision. For example, the following formula:
[0062]
number
[0063] A lattice form of the notch filter described by can be implemented here f notch This is the center frequency of the stopband of the notch filter, f sample This is the sampling frequency, α is a bandwidth parameter proportional to the bandwidth of the stopband. θ1 is the notch frequency fnotch These are parameters related to, θ² is a parameter related to α.
[0064] When a notch filter is implemented in lattice form, it can have 16-bit precision while still providing an acceptable phase shift at the carrier frequency or drive tone frequency. For example, the phase shift of a 16-bit lattice form notch filter is shown in Figure 9 for a 16-bit notch filter implemented in non-lattice form. Rather than a large phase shift, it can be similar to the phase shift shown in Figure 10. Therefore, by using a specific digital filter format, the desired substantially minimized phase shift can be achieved with lower fixed-point precision, or even reduced to zero.
[0065] Method 600 substantially minimizes the phase shift of sensor signal components such as resonant components. Therefore, a novel and improved notch filter is provided. By substantially minimizing the phase shift, the drive algorithm or drive circuit can be considered to have substantially minimized phase delay, or the phase delay of the notch filter can be considered to be substantially zero. This simplifies the drive algorithm or circuit and therefore reduces the design cost of the meter electronic equipment 20. Novel and improved method. The 500 and vibrating meters 5 use notch filters to attenuate or remove the sensor signal component of the sensor signal provided by the sensor assembly 10, thereby preventing the sensor signal from being used to generate the drive signal. This reduces the computational load on the processor in the meter electronics 20.
[0066] The detailed description of the embodiments described above does not exhaustively describe all embodiments that the inventors of the present invention consider to fall within the technical scope of this specification. Indeed, those skilled in the art will understand that it is possible to create further embodiments by combining or removing certain elements of the embodiments described above in various ways, and that such further embodiments are included within the technical scope and teachings of this specification. It will also be apparent to those skilled in the art that further embodiments within the technical scope and teachings of this specification can be generated by combining the embodiments described above, either whole or in part.
[0067] Thus, while specific embodiments have been described herein for illustrative purposes, various equivalent modifications are possible within the technical scope of this specification, as will be apparent to those skilled in the art. The teachings presented herein are applicable not only to the embodiments described above and illustrated in the accompanying drawings, but also to other notch filters for vibrometers. Accordingly, the technical scope of the embodiments described above must be determined by the following claims.
Claims
1. A meter electronic device (20) having a notch filter (26) configured to filter the sensor signal from the sensor assembly (10) of a vibrating meter (5), A drive circuit (22) configured to generate a drive signal, The notch filter (26) is communicably connected to the sensor assembly (10) and the drive circuit (22), The aforementioned notch filter (26) A sensor signal consisting of a first component at the resonant frequency of the sensor assembly (10) and a second component at a non-resonant frequency is received from the sensor assembly (10). The first component is allowed to pass through, the second component is substantially attenuated by the notch filter, and the first component is configured to pass through the passband of the notch filter with substantially no attenuation and zero phase shift. The aforementioned passband is Centered on the resonant frequency of the sensor assembly, and including the resonant frequency of the first component of the sensor assembly, It lies between the two stopbands of the notch filter, and one of the two stopbands is centered on the non-resonant frequency of the second component. By substantially minimizing the phase shift of the first component at or near the resonant frequency of the sensor assembly, and substantially minimizing the phase shift over the entire range of the resonant frequencies of the sensor assembly, the drive circuit and the drive algorithm of the electronic device are made to consider the phase shift to be substantially minimized, thereby preventing the sensor signal from being used to generate the drive signal. A meter electronic device (20) is configured as follows.
2. The meter electronic device (20) according to claim 1, wherein the notch filter (26) configured to pass the first component with substantially zero phase shift is a fixed-point precision filter.
3. The meter electronic device (20) according to claim 1 or 2, wherein the sensor signal is further composed of at least one further non-resonant component, and the notch filter (26) is further configured to substantially attenuate the at least one further non-resonant component.
4. The meter electronic equipment (20) according to any one of claims 1 to 3, wherein the drive circuit (22) is configured to generate a multitone drive signal for the sensor assembly (10) based on the first component passed through the notch filter (26).
5. A method for filtering the sensor signal of a vibration meter using a notch filter, The steps include generating a drive signal using the drive circuit of the electronic equipment of the aforementioned vibrating meter, The steps include receiving a sensor signal, which includes a first component at the resonant frequency of the sensor assembly and a second component at a non-resonant frequency, with the notch filter, The first component is passed through the passband of the notch filter with virtually no attenuation and zero phase shift, and the passband is Centered on the resonant frequency of the sensor assembly, and including the resonant frequency of the first component of the sensor assembly, It lies between the two stopbands of the notch filter, and one of the two stopbands is centered on the non-resonant frequency of the second component. The phase shift of the first component is substantially minimized at or near the resonant frequency of the sensor assembly, and the phase shift is substantially minimized over the entire range of the resonant frequencies of the sensor assembly. The steps include: substantially attenuating the second component with the notch filter so that the drive circuit and the drive algorithm of the electronic device can consider the phase shift to be substantially minimized, thereby preventing the sensor signal from being used to generate the drive signal; A method that includes this.
6. In the notch filter, which is a fixed-point precision filter, the first component is passed through with a substantially zero phase shift. The method according to claim 5, further comprising:
7. The sensor signal is further composed of at least one additional non-resonant component, This method is The step of substantially attenuating the at least one further non-resonant component with the notch filter. The method according to claim 5 or 6, further comprising:
8. The step of generating a multitone drive signal for the sensor assembly based on the first component that has passed through the notch filter. The method according to any one of claims 5 to 7, further comprising:
9. A method for setting the notch filter of a vibrating meter, The steps include generating a drive signal using the drive circuit of the electronic equipment of the aforementioned vibrating meter, The steps include: preparing the notch filter configured to receive a sensor signal including a first component at the resonant frequency of the sensor assembly and a second component at a non-resonant frequency; The process includes the step of adjusting the notch filter so as to substantially minimize the phase shift of the first component over a frequency range including the resonant frequency when the first component passes through the passband of the notch filter, The aforementioned passband is Centered on the resonant frequency of the sensor assembly, and including the resonant frequency of the first component of the sensor assembly, It lies between the two stopbands of the notch filter, and one of the two stopbands is centered on the non-resonant frequency of the second component. The phase shift of the first component is substantially minimized at or near the resonant frequency of the sensor assembly, and the phase shift is substantially minimized over the entire range of the resonant frequencies of the sensor assembly. A method for preventing the sensor signal from being used to generate the drive signal, by substantially attenuating the second component, thereby enabling the drive circuit and the drive algorithm of the electronic device to consider the phase shift to be substantially minimized.
10. The method according to claim 9, wherein the step of adjusting the notch filter so that the phase shift of the first component is substantially minimized includes the step of adjusting the notch filter so that the phase shift of the first component is substantially minimized at the resonant frequency.
11. A step to minimize the error in the implementation of the fixed-point precision of the notch filter by comparing a first phase shift for a notch filter having first fixed-point precision with a second phase shift for a notch filter having second fixed-point precision. The method according to claim 9 or 10, further comprising:
12. The step of implementing the form of the notch filter such that the error in the fixed-point precision implementation of the notch filter is substantially minimized. The method according to claim 11, further comprising: