Coriolis flow meter with compensation for external magnetic fields

Abstract

A Coriolis flow meter (5) is provided, the Coriolis flow meter (5) comprising a flow conduit (103A, 103B) having a driver (104) connected to the flow conduit and a pick-up sensor (105, 105 '). The metering electronics (20) are configured to drive the driver (104) to oscillate the flow conduits (103A, 103B) and to receive signals from the pick-up sensors (105, 105 '). The metering electronics (20) are configured to capture a voltage for the two pick-up sensors (105, 105 ') and to determine a PO ratio and to determine whether the PO ratio falls within a predetermined PO limit. The presence of an external magnetic field is indicated if the PO ratio falls outside a predetermined PO limit. Wherein the metering electronics (20) are configured to access the PO ratio and flow offset correlation, and, in the event that the presence of an external magnetic field is detected, calculate a compensated flow corrected for an error caused by the external magnetic field using the PO ratio and flow offset correlation.

Description

Technical Field

[0001] The embodiments described below relate to vibration sensors, and more particularly to external magnetic field detection and compensation for external magnetic fields. Background Art

[0002] Vibration sensors, such as, for example, vibrating densitometers and Coriolis flowmeters are generally known and used to measure mass flow and other information related to the material flowing through the conduit in the flowmeter. Example Coriolis flowmeters are disclosed in U.S. Patent No. 4,109,524, U.S. Patent No. 4,491,025, and Reissue Patent No. 31,450. These flowmeters have a metering assembly having one or more conduits in a straight configuration or a curved configuration. Each conduit configuration in a Coriolis mass flowmeter, for example, has a set of natural vibration modes, which can be simple bending, torsion, or coupled types. Each conduit can be driven to oscillate in a preferred mode. When no flow passes through the flowmeter, the driving force applied to the conduit causes all points along the conduit to oscillate in the same phase or with a small "zero offset" - this is the time delay measured at zero flow.

[0003] When the material begins to flow through the conduit, the Coriolis force causes each point along the conduit to have a different phase. For example, the phase at the inlet end of the flow meter lags the phase at the centralized drive location, while the phase at the outlet leads the phase at the centralized drive location. Pickups on the conduit produce a sinusoidal signal that represents the motion of the conduit. The signal output from the pickups is processed to determine a time delay between the pickups, known as ΔT. The time delay between two or more pickups is proportional to the mass flow rate of the material flowing through the conduit.

[0004] Meter electronics connected to the driver generates a drive signal to operate the driver and also determines the mass flow rate and / or other characteristics of the process material based on the signal received from the pickup. The driver can include one of many known arrangements; however, a magnet and opposing drive coil has been used with great success in the flow meter industry. Alternating current is delivered to the drive coil to cause the conduit to vibrate at the desired conduit amplitude and frequency. It is also known in the art to provide the pickup as a magnet and coil arrangement very similar to the driver arrangement.

[0005] When the flow tube vibrates, the pickup windings pass through the magnetic field of the magnet, which generates a voltage. The main factor that generates such a voltage is the radial magnetic field. If the magnetic field is disturbed or changed during the operation of the meter, the output of the meter will be affected. One way to interfere with the magnetic field of the pickup is to place another magnet in close proximity to the pickup magnet. By placing an external magnet close to the pickup of the Coriolis meter, the flow reading can be changed to indicate more flow or less flow depending on the magnetic pole orientation of the external magnet or the positioning of the external magnet on the meter relative to the inlet or outlet pickup and / or driver. Once the magnet is removed, the sensor voltage and phase shift return to normal. This ability to manipulate flow can and has been used to harm the interests of uninformed parties in flow meter measurement matters. There is a need for a device and method to compensate for the external magnetic field of the flow meter so that the corrected flow value is reported and the errors caused by the external magnetic field are eliminated. Summary of the invention

[0006] According to an embodiment, a Coriolis flow meter is provided. The Coriolis flow meter includes: a flow conduit; a driver and a pick-off sensor connected to the flow conduit; and a meter electronics device configured to drive the driver to oscillate the flow conduit and receive a signal from the pick-off sensor. The meter electronics device is configured to capture voltages for two pick-off sensors and determine PO 比率 The meter electronics is also configured to determine the PO 比率 Whether it falls into the scheduled PO 限值 The meter electronics are configured to 比率 Fall on the scheduled PO 限值 The meter electronics is configured to calculate a compensated flow rate using the PO ratio versus flow offset correlation when the presence of an external magnetic field is detected. The compensated flow rate includes a flow rate corrected for an error caused by an external magnetic field.

[0007] According to an embodiment, a method for operating a Coriolis flowmeter is provided. The method includes: flowing a flow material through a flow conduit of the flowmeter; and driving a driver connected to the flow conduit to cause the flow conduit to oscillate in a first bending mode. A signal is received from a pickoff sensor connected to the flow conduit. A signal is generated for the pickoff sensor and for determining a PO 比率 And capture voltage. Determine PO 比率 Whether it falls into the scheduled PO 限值 Within, and in PO 比率 Fall on the scheduled PO 限值Indicates the presence of an external magnetic field in the event of a magnetic field being detected. Accesses the PO ratio vs. flow offset correlation. Uses the PO ratio vs. flow offset correlation to calculate the compensated flow in the event of an external magnetic field being detected. The compensated flow rate includes a flow rate corrected for an error caused by an external magnetic field.

[0008] All aspects

[0009] According to one aspect, a Coriolis flow meter includes: a flow conduit; a driver and a pickoff sensor connected to the flow conduit; and a meter electronics device configured to drive the driver to oscillate the flow conduit and configured to receive a signal from the pickoff sensor. The meter electronics device is configured to capture voltages for two pickoff sensors and determine PO 比率 The meter electronics is also configured to determine the PO 比率 Whether it falls into the scheduled PO 限值 The meter electronics are configured to 比率 Fall on the scheduled PO 限值 The meter electronics is configured to calculate a compensated flow rate using the PO ratio versus flow offset correlation when the presence of an external magnetic field is detected. The compensated flow rate includes a flow rate corrected for an error caused by an external magnetic field.

[0010] Preferably, the PO ratio and flow deviation correlation is calculated by the meter electronics.

[0011] Preferably, the PO ratio and flow deviation correlation is predetermined and stored in the meter electronics.

[0012] Preferably, the following equation is used to calculate

[0013] Preferably, use a Mag =(m*PO ratio+b) to calculate Comp Mag , where m and b include the slope constant and intercept constant, respectively.

[0014] Preferably, for Comp Mag The equation includes one of a linear equation and a non-linear equation, each including any number of coefficients, wherein the equation includes relating the PO ratio to ΔT and includes a correlation of the PO ratio to a flow offset.

[0015] Preferably, the PO ratio and flow rate offset correlation includes at least one of density compensation and temperature compensation.

[0016] According to one aspect, a method for operating a Coriolis flow meter includes: flowing a flow material through a flow conduit of the flow meter; and driving a driver connected to the flow conduit to cause the flow conduit to oscillate in a first bending mode. A signal is received from a pickoff sensor connected to the flow conduit. A signal is generated for the pickoff sensor and for determining a PO 比率 And capture voltage. Determine PO 比率 Whether it falls into the scheduled PO 限值 Within, and in PO 比率 Fall on the scheduled PO 限值 Indicates the presence of an external magnetic field in the event of a magnetic field being detected. Accesses the PO ratio vs. flow offset correlation. Uses the PO ratio vs. flow offset correlation to calculate the compensated flow in the event of an external magnetic field being detected. The compensated flow rate includes a flow rate corrected for an error caused by an external magnetic field.

[0017] Preferably, the method includes calculating, with the meter electronics, a PO ratio versus flow excursion correlation.

[0018] Preferably, the method comprises storing a predetermined PO ratio and flow excursion correlation in the meter electronics.

[0019] Preferably, the method comprises calculating using meter electronics by an equation comprising

[0020]

[0021] Preferably, the method comprises using the meter electronics by including Comp Mag =(m*PO ratio+b) to calculate Comp Mag , where m and b include the slope constant and intercept constant, respectively.

[0022] Preferably, for Comp Mag The equation includes a linear equation or a non-linear equation including any number of coefficients, wherein the equation includes relating the PO ratio to ΔT to include a correlation of the PO ratio to a flow deviation.

[0023] Preferably, the PO ratio and flow rate offset correlation includes at least one of density compensation and temperature compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Like reference numerals represent like elements throughout the drawings. It should be understood that the drawings are not necessarily drawn to scale.

[0025] Figure 1 A vibrating meter according to an embodiment is shown;

[0026] Figure 2shows a meter electronics device according to an embodiment;

[0027] Figure 3 shows the effect of a magnetic field on a flow meter sensor pick-up voltage according to an embodiment;

[0028] Figure 4 shows the effect of a magnetic field on flow measurement according to an embodiment;

[0029] Figure 5A shows the magnetic field of the pickup assembly without the presence of a magnet;

[0030] Figure 5B shows the magnetic field of a pickup assembly in the presence of an external magnet, with the south pole of the magnet oriented toward the pickup assembly;

[0031] Figure 5C shows the magnetic field of a pickup assembly in the presence of an external magnet, with the north pole of the magnet oriented toward the pickup assembly;

[0032] Figure 6 shows a flow chart relating to an example of an implementation for magnetic tamper detection;

[0033] Figure 7 shows a flow chart associated with another example implementation of magnetic tamper detection;

[0034] Figure 8 Pseudocode for a magnetic tamper implementation is shown;

[0035] Fig. 9A and Fig. 9B False flag detection for an embodiment of the present invention is shown;

[0036] Fig.10 shows an example of the change in the PO ratio of a Coriolis flowmeter due to an external magnetic field;

[0037] Fig.11 shows an example of PO ratio and flowmeter delta t (Δt) caused by an external magnetic field; and

[0038] Fig.12 Examples of PO ratio and flow signals and compensated flow signals are shown. DETAILED DESCRIPTION

[0039] Figures 1 to 12And the following description depicts specific examples to teach those skilled in the art how to implement and use the best mode of the embodiments of the sensor assembly, support rods, drivers, and pickup sensors. For the purpose of teaching the principles of the invention, some conventional aspects have been simplified or omitted. Those skilled in the art will understand variations from these examples that fall 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 multiple variations of the embodiments. Therefore, the embodiments described below are not limited to the specific examples described below, but are only limited by the claims and their equivalents.

[0040] Figure 1 A flow meter 5 according to an embodiment is shown. The flow meter 5 includes a sensor assembly 10 and a meter electronics 20. The meter electronics 20 is connected to the sensor assembly 10 via leads 100 and is configured to provide a measurement of one or more of density, mass flow, volume flow, total mass flow, temperature, or other measurements or information via a communication path 26. The flow meter 5 may include a Coriolis mass flow meter or other vibrating flow meter. It should be apparent to those skilled in the art that the flow meter 5 may include any form of flow meter 5, regardless of the number of drivers, pick-off sensors, flow conduits, or vibration operating modes.

[0041] The sensor assembly 10 includes a pair of flanges 101 and 101', manifolds 102 and 102', a driver 104, pickoff sensors 105 and 105', and flow conduits 103A and 103B. The driver 104 and the pickoff sensors 105 and 105' are connected to the flow conduits 103A and 103B.

[0042] Flanges 101 and 101' are attached to manifolds 102 and 102'. In some embodiments, manifolds 102 and 102' can be attached to opposite ends of spacer 106. Spacer 106 maintains the spacing between manifolds 102 and 102'. When sensor assembly 10 is inserted into a pipeline (not shown) carrying a process fluid being measured, the process fluid enters sensor assembly 10 through flange 101, passes through inlet manifold 102, where the process fluid volume is directed into flow conduits 103A and 103B, flows through flow conduits 103A and 103B and returns to outlet manifold 102' where the process fluid exits sensor assembly 10 through flange 101'.

[0043] The process fluid may include a liquid. The process fluid may include a gas. The process fluid may include, for example, a multiphase fluid, such as a liquid including entrained gas and / or entrained solids, without limitation. The flow conduits 103A and 103B are selected and appropriately mounted to the inlet manifold 102 and the outlet manifold 102' so as to have substantially the same mass distribution, moment of inertia, and elastic modulus about the bending axis WW and W'-W', respectively. The flow conduits 103A and 103B extend outwardly from the manifolds 102 and 102' in a substantially parallel manner.

[0044] Flow conduits 103A and 103B are driven by driver 104 in opposite directions about respective bending axes W and W' and in a so-called first out-of-phase bending mode of flow meter 5. Driver 104 may include one of many well-known arrangements, such as a magnet mounted to flow conduit 103A and an opposing coil mounted to flow conduit 103B. An alternating current is passed through the opposing coils to cause the two conduits to oscillate. A suitable drive signal is applied to driver 104 by meter electronics 20 via leads 110. Other drive arrangements are contemplated and are within the scope of the specification and claims.

[0045] Meter electronics 20 receives sensor signals on leads 111 and 111', respectively. Meter electronics 20 generates a drive signal on lead 110 that causes driver 104 to oscillate flow conduits 103A and 103B. Other sensor arrangements are contemplated and are within the scope of the specification and claims.

[0046] Meter electronics 20 processes the left and right speed signals from pickoff sensors 105 and 105' to calculate flow, etc. Communications path 26 provides input and output means that allow meter electronics 20 to interface with an operator or with other electronic systems. Figure 1 The description is provided merely as an example of the operation of a flow meter and is not intended to limit the teachings of the present invention. In embodiments, single tube flow meters and multi-tube flow meters having one or more drivers and pick-offs are contemplated.

[0047] In one embodiment, meter electronics 20 is configured to vibrate flow conduits 103A and 103B. The vibration is performed by driver 104. Meter electronics 20 also receives resulting vibration signals from pickoff sensors 105 and 105'. The vibration signals include vibration responses of flow conduits 103A and 103B. Meter electronics 20 processes the vibration responses and determines a response frequency and / or phase difference. Meter electronics 20 processes the vibration responses and determines one or more flow measurements, including mass flow and / or density of the process fluid. Other vibration response characteristics and / or flow measurements are contemplated and are within the scope of the specification and claims.

[0048] In one embodiment, as shown, flow conduits 103A and 103B comprise generally Ω-shaped flow conduits. Alternatively, in other embodiments, the flow meter may comprise generally straight flow conduits, U-shaped conduits, delta-shaped conduits, etc. Additional flow meter shapes and / or configurations may be used and are within the scope of the specification and claims.

[0049] Figure 2 is a block diagram of the meter electronics 20 of the flow meter 5 according to an embodiment. In operation, the flow meter 5 provides various measurements that can be output, including one or more of mass flow, volume flow, individual flow component mass flow and volume flow, and a measurement or average of a total flow including, for example, both volume flow and mass flow.

[0050] The flow meter 5 generates a vibration response. The vibration response is received and processed by the meter electronics 20 to generate one or more fluid measurement values. These values ​​may be monitored, recorded, saved, totaled and / or output.

[0051] Meter electronics 20 includes an interface 201, a processing system 203 in communication with interface 201, and a storage system 204 in communication with processing system 203. Although these components are shown as distinct blocks, it should be understood that meter electronics 20 may include various combinations of integrated and / or discrete components.

[0052] The interface 201 is configured to communicate with the sensor assembly 10 of the flow meter 5. The interface 201 may be configured to couple to the lead 100 (see Figure 1 ) and exchanges signals with, for example, the driver 104, the pickup sensors 105 and 105', and a temperature sensor (not shown). The interface 201 may also be configured to communicate via the communication path 26, for example, with an external device.

[0053] Processing system 203 may include any form of processing system. Processing system 203 is configured to retrieve and execute stored routines to operate flow meter 5. Storage system 204 may store routines, including flow meter routine 205 and magnetic field detection routine 209. Other measurement / processing routines are contemplated and are within the scope of the specification and claims. Storage system 204 may store measured values, received values, operating values, and other information. In some embodiments, storage system stores mass flow 221, density (ρ) 225, viscosity (μ) 223, temperature (T) 224, drive gain 306, transducer voltage 303, and any other variables known in the art. Drive gain 306 comprises a relative measure of how much power is consumed by the driver to keep the catheter vibrating at the desired frequency.

[0054] The flow meter routine 205 can generate and store fluid quantification and flow measurements. These values ​​can include approximately instantaneous measurements, or can include total or cumulative values. For example, the flow meter routine 205 can generate mass flow measurements and store them in, for example, a mass flow 221 memory of the storage system 204. The flow meter routine 205 can generate density 225 measurements and store them in, for example, a density 225 memory. As previously described and known in the art, mass flow 221 values ​​and density 225 values ​​are determined from vibration responses. The mass flow and other measurements can include approximately instantaneous values, can include samples, can include average values ​​over time intervals, or can include cumulative values ​​over time intervals. The time interval can be selected to correspond to a period of time during which certain fluid conditions are detected, such as a fluid state of only liquid or alternatively a fluid state including liquid and entrained gas. In addition, other mass flows and related quantifications are contemplated and are within the scope of the specification and claims.

[0055] By placing an external magnet close to the pick-up of a Coriolis meter, the flow reading can be changed to indicate more flow or less flow depending on the pole position of the external magnet or the positioning of the external magnet on the meter inlet or outlet.

[0056] Go to Figure 3 , shows that when using magnets and coils for pickoff sensors 105 and 105', external magnetic fields, whether from electromagnetic sources or permanent magnets, affect the readings of sensor assembly 10 by monitoring meter electronics 20. Clearly, there is a relatively sharp and symmetrical step change.

[0057] Figure 3 The area marked by bracket #1 in FIG. 1 indicates that the magnet is placed near the pick-off sensor 105' positioned closest to the flow meter output. When the magnet is placed there, the signal provided by the pick-off sensor 105' positioned closest to the flow meter output (at Figure 3 Marked as PO 输出 ) detects a relatively sharp and symmetrical step change in voltage.

[0058] Figure 3 The area marked by bracket #2 in FIG. 1 indicates that the magnet is placed near the pickoff sensor 105 located closest to the flow meter input. When the magnet is placed there, the signal provided by the pickoff sensor 105' located closest to the flow meter output (in Figure 3 Marked as PO 输出 ) also detects a relatively sharp and symmetrical step change in voltage. In the signal ( Figure 3 Marked as PO 输入) A voltage spike is also detected in the signal provided by the driver 104. A voltage spike is also detected in the signal provided by the driver 104.

[0059] Figure 3 The area marked by bracket #3 in represents that the magnet is placed near the driver 104. A detectable, relatively sharp and symmetrical step change in voltage is detected in the signal provided by the driver 104.

[0060] Go to Figure 4 , shows an external magnet affecting the ΔT reading of the flow meter 5. When the driver 104 excites the flow conduits 103A, 103B to oscillate in opposite directions at the natural resonant frequency, the flow conduits 103A, 103B oscillate and the voltage generated from each pick-off sensor 105, 105' produces a sine wave. This indicates the movement of one conduit relative to the other. The time delay between the two sine waves is called ΔT, which is proportional to the mass flow rate. If the phase of either of the flow conduits 103A, 103B is affected, the ΔT changes. The flow should cause a positive change in the phase of one pick-off sensor and an equal negative change in the phase of the other pick-off sensor.

[0061] Figure 4 The area marked by bracket #1 in indicates that the magnet is placed near the pickoff sensor 105' located closest to the flow meter output. When the magnet is placed there, a relatively sharp and symmetrical step decrease in ΔT is detected.

[0062] Figure 4 The area marked by bracket #2 in represents the placement of the magnet near the pickoff sensor 105 located closest to the flow meter input. When the magnet is placed there, a relatively sharp and symmetrical step increase in ΔT is detected.

[0063] Figure 4 The area marked by bracket #3 in φ indicates that the magnet is placed near the driver 104. When the magnet is placed there, a relatively sharp and symmetrical step decrease in ΔT is detected.

[0064] FIG. 5A to FIG. 5C shows how the magnetic field near the transducer changes in the presence of another magnet. Figure 5A The magnetic field of the pickup assembly is shown in the absence of a magnet (dashed line). Figure 5B shows the magnetic field in the presence of an external magnet, with the south pole of the magnet oriented toward the pickup assembly, and Figure 5C shows the magnetic field in the presence of an external magnet, with the north pole of the magnet oriented toward the pickup assembly. Figure 4 As shown in , if the magnetic field is disturbed or changed during operation of the meter, the output of the meter will be affected.

[0065] In an embodiment, a method for detecting magnetic tampering would be to monitor the pick-up voltage. In an embodiment, the voltage difference between the pick-up sensors 105 and 105' is measured. In an embodiment, the voltage ratio between the pick-up sensors 105 and 105' is measured.

[0066] In the following description, the pick-up ratio is discussed. However, it is contemplated that the pick-up difference may also be used. The pick-up sensors 105 and 105' will also be referred to as LPO (left pick-up) and RPO (right pick-up), respectively.

[0067] like Figure 6 A flow chart illustrating a method for determining magnetic tampering is provided. In an embodiment, as shown in step 602, a PO is determined. 零 .PO 零 is the average value captured during the zeroing process:

[0068]

[0069] in:

[0070] RPO 零 = Average value captured during the zeroing process of the RPO

[0071] LPO 零 = Average value captured during the zeroing process of the LPO

[0072] The zeroing process is usually performed when there is no flow through the flow meter, and the driving force applied to the conduit causes all points along the conduit to oscillate in the same phase or with a small "zero offset", which is the time delay measured at zero flow. The process causes the flow meter to be calibrated so that no flow is measured during the no flow condition.

[0073] In an embodiment, as shown in step 604, the PO 比率 , P.O. 比率 is the ratio of the pick-off voltages captured during fluid flow and meter operation.

[0074]

[0075] in:

[0076] RPO = Voltage value captured during meter operation for RPO

[0077] LPO = voltage value captured during meter operation for LPO

[0078] In an embodiment, as shown in step 606, a PO is established. 限值 .PO 限值 is the pick rate limit, which is the PO that can be allowed before indicating tampering 比率With PO 零 As will be appreciated by those skilled in the art, due to the many types of flow meter configurations, operating settings, installation variables, flow variables, and process variables, PO 限值 Varies depending on application.

[0079] In step 608, PO 比率 With PO 限值 Compare. If PO 比率 In PO 限值 , the flowmeter is determined to be operating within “normal” operating limits. However, if PO 比率 In PO 限值 Otherwise, a sign indicating potential magnetic tampering is generated.

[0080] Under certain flow conditions, this approach can provide a flag indicating tampering even though no tampering actually exists. In an embodiment, to limit the number of "false flags", additional logic is added involving monitoring additional meter outputs. These outputs can include one or more of mass flow, density, and drive gain.

[0081] exist Figure 7 A flow chart showing additional checks for reducing false flags is shown in . In this embodiment, multiple system states can be returned: "Normal", "Flag", and "Transition". The Normal state implies that all leading variables and pickup ratios are within their confidence intervals. The Flag state implies that all leading variables are within their confidence intervals, but the pickup ratio is outside its confidence interval. The Transition state implies that at least one leading variable is outside its confidence interval. Each of these system states can be simply stored as a digital code and read back such as via, for example, modbus communication. The digital code can be translated into human readable text and can be presented to a display.

[0082] In step 702, a plurality of zero variables are collected. The zero variables may include RPO and LPO signals, flow tube frequency, drive gain, fluid density, damping factor, and other flow meter variables known in the art.

[0083] In step 704, the ratio of the fluid flow and the pickup voltage captured during meter operation, PO, is calculated according to equation (1). 比率 In step 706, the zero variables collected over time, including the pick-off voltage ratio, are averaged and / or standard deviations are calculated. The average and standard deviation of each variable are stored in the storage system 204 using a suitable data structure such as an array.

[0084] Steps 702 to 706 are iterated during the zero process or zeroing condition. This helps to create a baseline for all collected variables, which can be set during process conditions for comparison purposes. These values ​​can be set at the factory during manufacturing and calibration, or can be set / reset in the field (i.e., after installation) under zeroing conditions.

[0085] In step 708, the flow meter is operated under process conditions and operating variables are collected. The operating variables are from the same set of variables as collected during the zero process, but are instead collected under process conditions. The operating variables may include RPO and LPO signals, flow tube frequency, drive gain, fluid density, damping factor, and other flow meter variables known in the art. These operating variables are collected over time and averaged and / or a standard deviation is calculated. The operating PO is also calculated. 比率 . Use appropriate data structures such as arrays to store PO 比率 The average values ​​and standard deviations of the RPO signal and the LPO signal are stored in the storage system 204 .

[0086] In step 710, some of the manipulated variables are compared to the zero variable. In particular, flow tube frequency, drive gain, fluid density and / or damping factor are compared, and it is determined whether all of the compared values ​​are within the confidence interval.

[0087] As will be appreciated by those skilled in the art, confidence intervals can be determined empirically based on targeting a desired outcome. i ) includes:

[0088]

[0089] in:

[0090]

[0091] deadband = factor that buffers the observable response

[0092]

[0093] The deadband is determined empirically to adjust the sensitivity of the system.

[0094] If any of the variables are outside their corresponding confidence intervals, the "transition" flag state is activated. However, if all variables are within their corresponding confidence intervals, the PO is compared in step 712. 比率 Specifically, in step 712, the PO 比率 The zero PO previously determined according to steps 702 to 704 比率If the operation PO 比率 If the PO of the operation is within its confidence interval, it returns to "normal". 比率 Outside of its confidence interval, a "flag" status is returned to indicate a potential magnetic tamper event.

[0095] It should be noted that if no zero value is stored, then Figure 7 The flow chart of may start at step 708. In this case, a reference value is substituted for the zero value for comparison. The reference value is an estimate of the approximate ideal zero value stored in memory. These values ​​will vary based on the details of the flow meter such as geometry, size, construction materials, transducer arrangement and type, etc. In an embodiment, one or more zero variables may be substituted by a reference value.

[0096] Returning to step 712, the following is an example of how the flow chart may be arranged in an implementation. The pseudo code is provided only as an aid for clarity purposes and should not be construed as limiting: The first step may be to check for density changes using the density ratio:

[0097]

[0098] in:

[0099] ρ m = measured density = Average density ratio

[0100] ρ 零 = Density reference value

[0101] An example of where the following logic can be applied is in the case of establishing a density ratio:

[0102] If then

[0103] Check Status = "Transition"

[0104] Else if then

[0105] Check Status = "Transition"

[0106] Else

[0107] Check Status = "Normal"

[0108] Where: l = Density range limit

[0109] Another output check can be the drive gain change using the drive gain ratio:

[0110]

[0111] in:

[0112] Dg m = Measured drive gain

[0113] Dg r =Average drive gain ratio

[0114] Dg 零 =Drive gain reference value

[0115] An example of the following logic that can be applied is when establishing a drive gain ratio:

[0116] If D m =100then

[0117] Check Status = "Transition"

[0118] Else if Dg r <=(1-Dg l )then

[0119] Check Status = "Transition"

[0120] Else if Dg r <=(1+Dg l )then

[0121] Check Status = "Transition"

[0122] Else

[0123] Check Status = "Normal"

[0124] Where: Dg l =Drive gain range limit

[0125] Finally, the pick ratio logic is applied, as shown in equation (2). The pick ratio logic can be shown as:

[0126] If PO r <(PO 零 -PO 限值 )then

[0127] Check Status = "Flag"

[0128] If PO r <(PO 零 +PO 限值 )then

[0129] Check Status = "Flag"

[0130] Else

[0131] Check Status = "Normal"

[0132] Among them: PO 限值 =PO range limit

[0133] exist Figure 8 An example of combinatorial logic shown using pseudocode is found in . It should be noted that the flow, density, and drive gain variables may or may not be present in an implementation, and the order in which they are analyzed may be different. Fig. 9B , compared to using the pickup ratio alone for the predetermined PO limit, applying the above flow condition logic to the Fig. 9A Looking at the PO ratio data, it will be clear that there are significantly fewer false positives ("false flags").

[0134] In addition to simply detecting magnetic tampering, in embodiments, meter electronics 20 may implement compensation to overcome the effects of such tampering. Fig.10 An example of a change in the PO ratio of a Coriolis flow meter from a baseline value to a new value due to the application of an external magnetic field is shown. The dashed line represents the PO ratio and the solid line represents Δt. The amount of change in the PO ratio can be correlated to the amount of flow offset. This correlation can be used to compensate the flow signal and eliminate the amount of error caused in the meter. Fig.10 The area marked with (1) in FIG. 1 represents the magnet placed near the pick-off sensor 105' located closest to the flow meter output. Fig.10 The area marked with (2) in FIG. 1 represents the magnet placed near the pick-off sensor 105 located closest to the flow meter input. Fig.10 The area marked with (3) indicates that the magnet is placed near the driver 104. In each case, a significant change in the PO ratio can be detected.

[0135] In an embodiment, the PO ratio and flow offset correlation is calculated by the flow meter meter electronics. In an embodiment, the PO ratio and flow offset correlation is empirically predetermined and stored in the meter electronics. In an embodiment, the meter electronics 20 accesses the PO ratio and flow offset correlation for compensation.

[0136] Fig.11 An example graph of PO ratio versus flow meter delta t (Δt) caused by an external magnet is shown. The slope formula of the line on the graph can be used as a relationship basis to eliminate the effects of the external magnet. The slope formula on the graph is shown only as an example. It will be understood that other slope formulas may be suitable for different flow meters.

[0137] The basis for magnetic compensation is derived from the basic equation used to determine mass flow:

[0138]

[0139] in:

[0140]

[0141] FCF = Flow Calibration Factor

[0142] Δt = time delay between pick-up sensors

[0143] Zero = Time delay between pick-off sensors under no flow conditions

[0144] However, equation (6) is modified to account for magnetic tampering, which results in a modified flow rate,

[0145]

[0146] in:

[0147] Comp Mag =(m*PO 比率 +b) (8)

[0148] Where: m and b are derived from, for example, Fig.11 The slope constant and intercept constant determined by the relationship of the data of the illustrated curve. It will be understood by those skilled in the art that Comp Mag The form of the equation can be linear or non-linear with any number of coefficients. The equation need only relate the PO ratio to ΔT or flow rate to form a PO ratio to flow rate offset correlation. It should also be understood that this compensation can be done in units of time or flow rate (i.e., lb / min or metric equivalent).

[0149] In an alternative embodiment, the effects of density and temperature may also be considered:

[0150]

[0151] in:

[0152] cl = density compensation

[0153] c2=Temperature compensation

[0154] ρ = density of the fluid

[0155] ρ cal = Density of the calibration fluid measured by the flow meter

[0156] T = temperature measured by the flow meter

[0157] T CAL = Temperature of the calibration fluid measured by the flow meter

[0158] In equation (9), both temperature compensation and density compensation are shown. It will be understood by those skilled in the art that in an embodiment, only density or only temperature is used to calculate the compensated flow. The values ​​of c1 and c2 are determined by testing at a test temperature or by testing density, and reflect the magnitude of the compensation change for changes in temperature and / or density.

[0159] Fig.12 Graphs of the PO ratio (dashed line) and the uncompensated flow signal (thick solid line) and the compensated flow signal (dotted line) are shown. By applying the compensation method described above, it can be seen that the flow signal output by the meter electronics 20 can be corrected despite undesirable changes in the PO ratio.

[0160] The detailed description of the above embodiments is not an exhaustive description of all embodiments contemplated by the inventor to fall within the scope of this specification. Indeed, those skilled in the art will recognize that certain elements of the above embodiments may be variously combined or removed to produce other embodiments, and such additional embodiments fall within the scope and teachings of this specification. It will also be apparent to those of ordinary skill in the art that the above embodiments may be combined in whole or in part to produce additional embodiments within the scope and teachings of this specification.

[0161] Therefore, although specific embodiments are described herein for illustrative purposes, various equivalent modifications are possible within the scope of this specification as will be appreciated by those skilled in the relevant art. The teachings provided herein may be applied to other sensors, sensor holders, and catheters, and not just to the embodiments described above and shown in the accompanying drawings. Therefore, the scope of the above embodiments should be determined by the appended claims.

Claims

1. A Coriolis flow meter (5), comprising: Flow conduits (103A, 103B); A driver (104) and a pick-off sensor (LP0, 105; RPO, 105'), the driver (104) and the pick-off sensor (LP0, 105; RPO, 105') being connected to the flow conduits (103A and 103B); Meter electronics (20) configured to drive the driver (104) to oscillate the flow conduits (103A, 103B) and receive signals from the pickoff sensors (105, 105'); wherein the meter electronics (20) is configured to capture voltages for both pickoff sensors (105, 105') and determine PO 比率 ; wherein the meter electronics (20) is configured to determine the PO 比率 Whether it falls into the scheduled PO 限值 within; and wherein the meter electronics (20) is configured to 比率 Falling on the scheduled PO 限值 In the case of an external magnetic field, it indicates the presence of an external magnetic field; wherein the meter electronics (20) is configured to access a PO ratio and flow deviation correlation; wherein the meter electronics (20) is configured to calculate a compensated flow rate using the PO ratio and flow offset correlation when the presence of an external magnetic field is detected The compensated flow rate includes a flow rate corrected for an error caused by the external magnetic field.

2. The Coriolis flow meter (5) according to claim 1, wherein: The PO ratio and flow deviation correlation is calculated by the meter electronics (20).

3. The Coriolis flow meter (5) according to claim 1, wherein: The PO ratio and flow excursion correlation is predetermined and stored in the meter electronics (20).

4. The Coriolis flow meter (5) according to claim 1, wherein: Use the equation below to calculate 5. The Coriolis flow meter (5) according to claim 4, wherein: Use Include Comp Mag =(m*PO 比率 +b) to calculate Comp Mag , where m and b include the slope constant and intercept constant, respectively.

6. The Coriolis flow meter (5) according to claim 4, wherein: For Comp Mag The equation includes one of a linear equation and a non-linear equation, each including any number of coefficients, wherein the equation includes relating the PO ratio to the ΔT and includes a correlation of the PO ratio to a flow offset.

7. The Coriolis flow meter (5) according to claim 1, wherein: The PO ratio to flow offset correlation includes at least one of density compensation and temperature compensation.

8. A method for operating a Coriolis flow meter, comprising: flowing a flow material through a flow conduit of the flow meter; driving a driver connected to the flow conduit to cause the flow conduit to oscillate in a first bending mode; receiving a signal from a pick-off sensor coupled to the flow conduit; The voltage is captured for the pick-off sensor and PO is determined 比率 ; Determine the PO 比率 Whether it falls into the scheduled PO 限值 within; and In the PO 比率 Falling on the scheduled PO 限值 In the case of an external magnetic field, it indicates the presence of an external magnetic field; Correlation between visit PO ratio and flow deviation; In the presence of an external magnetic field, the PO ratio is used to correlate the flow offset to calculate the compensated flow. The compensated flow rate includes a flow rate corrected for an error caused by the external magnetic field.

9. A method for operating a Coriolis flow meter according to claim 8, comprising calculating, with said meter electronics, said PO ratio to flow deviation correlation.

10. A method for operating a Coriolis flow meter according to claim 8, comprising storing a predetermined PO ratio and flow offset correlation in the meter electronics.

11. The method for operating a Coriolis flow meter according to claim 8, comprising using the meter electronics to calculate by an equation comprising 12. A method for operating a Coriolis flow meter according to claim 11, comprising using said meter electronics to Mag =(m*PO 比率 +b) to calculate Comp Mag ,in, m and b comprise the slope constant and intercept constant, respectively.

13. The method for operating a Coriolis flow meter according to claim 11, wherein: For Comp Mag The equation includes a linear equation or a non-linear equation including any number of coefficients, wherein the equation includes relating the PO ratio to the ΔT to include a correlation of the PO ratio to a flow deviation.

14. The method for operating a Coriolis flow meter according to claim 8, wherein: The PO ratio to flow offset correlation includes at least one of density compensation and temperature compensation.

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