Coriolis flow meter with external magnetic field detection

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 meter 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 meter electronics (20) are configured to capture the voltage of both the pick-up sensors (105, 105 ') and to determine a PORATIO, and to determine whether the PORATIO falls within a predetermined POLIMIT. If the PORATIO falls outside the predetermined POLIMIT, the presence of an external magnetic field is indicated.

Description

Technical Field

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

[0002] Vibration sensors such as, for example, vibrating densitometers and Coriolis flowmeters are generally known and are used to measure mass flow and other information related to the material flowing through the conduits in the flowmeter. Example Coriolis flowmeters are disclosed in U.S. Pat. No. 4,109,524, U.S. Pat. No. 4,491,025, and Re. 31,450. These flowmeters have a meter 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, torsional, or coupled types. Each conduit can be driven to oscillate in a preferred mode. When there is no flow passing 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 generate drive signals to operate the driver and also determine mass flow and / or other characteristics of the process material based on the signals received from the pickup. The driver may comprise one of many known arrangements; however, a magnet and opposing drive coil have 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] As the flow tube vibrates, the pickup windings pass through the magnetic field of the magnet, which generates a voltage. The primary factor in generating such a voltage is the radial magnetic field. If the magnetic field is disturbed or altered during meter operation, 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 and / or coil. By placing an external magnet close to the pickup of a Coriolis meter, the flow reading may change 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 disadvantage uninformed parties in flow meter measurement matters. There is a need for an apparatus and method for detecting an external magnetic field of a flow meter. Summary of the invention

[0006] According to an embodiment, a Coriolis flow meter is provided, which includes a flow conduit and a driver and a pick-off sensor connected to the flow conduit. The meter electronics is configured to drive the driver to oscillate the flow conduit and is configured to receive a signal from the pick-off sensor. The meter electronics is configured to capture the voltage of both the pick-off sensor and determine the PO RATIO , and determine the PO RATIO Is it on the scheduled PO? LIMIT The meter electronics are configured so that if PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

[0007] According to an embodiment, a method for operating a Coriolis flow meter is provided. The method includes: flowing a flowing 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 from a pickoff sensor connected to the flow conduit is received, and a voltage of the pickoff sensor is captured, and a PO is determined. RATIO . Determine PO RATIO Is it on the scheduled PO? LIMIT Within, and if PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

[0008] aspect

[0009] According to one aspect, a Coriolis flow meter includes a flow conduit and a driver and a pickoff sensor connected to the flow conduit. The meter electronics is configured to drive the driver to oscillate the flow conduit and to receive a signal from the pickoff sensor. The meter electronics is configured to capture voltages of both the pickoff sensors and determine PORATIO , and determine the PO RATIO Is it on the scheduled PO? LIMIT The meter electronics are configured so that if PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

[0010] Preferably, a first process variable is collected and compared to a first confidence interval, wherein the meter electronics is configured to determine if the first process variable falls within the first confidence interval and the PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

[0011] Preferably, a second process variable is collected and compared to a second confidence interval, wherein the meter electronics is configured to determine if both the first process variable and the second process variable fall within their respective confidence intervals and PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

[0012] Preferably, a third process variable is collected and compared to a third confidence interval, and wherein the meter electronics is configured to determine if the first process variable, the second process variable, and the third process variable fall within their respective confidence intervals, and PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

[0013] Preferably, the first process variable, the second process variable and the third process variable each include one of a flow tube frequency, a drive gain, a fluid density and a damping factor.

[0014] Preferably, the meter electronics collects the PO ZERO , and the meter electronics respond to PO ZERO At least one of a mean value and a standard deviation is determined, and the meter electronics is configured to convert the PO LIMIT Determined to include with PO ZERO The allowable deviation.

[0015] Preferably, if any of the first process variable, the second process variable, and the third process variable are outside of their respective confidence intervals, the meter electronics returns to a "transition" state.

[0016] Preferably, if all of the first process variable, the second process variable and the third process variable are within their respective confidence intervals, and PO RATIO Fall on the scheduled PO LIMIT If the meter electronics returns to the “Normal” state,

[0017] According to one aspect, a method for operating a Coriolis flow meter includes: flowing a flowing 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. Receiving a signal from a pickoff sensor connected to the flow conduit, and capturing a voltage of the pickoff sensor, and determining a PO RATIO . Determine PO RATIO Is it on the scheduled PO? LIMIT Within, and if PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

[0018] Preferably, the method comprises: collecting a first process variable; comparing the first process variable to a first confidence interval, and if the first process variable falls within the first confidence interval, and PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

[0019] Preferably, the method comprises: collecting a second process variable; comparing the second process variable to a second confidence interval, and if both the first process variable and the second process variable fall within their respective confidence intervals, and PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

[0020] Preferably, the method includes: collecting a third process variable; comparing the third process variable to a third confidence interval, and if both the first process variable and the third process variable fall within their respective confidence intervals, and PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

[0021] Preferably, the first process variable, the second process variable and the third process variable each include one of a flow tube frequency, a drive gain, a fluid density and a damping factor.

[0022] Preferably, the method comprises: collecting PO ZERO ; For PO ZERO Determine at least one of a mean and a standard deviation; and determine the ZERO PO of the allowable deviation LIMIT .

[0023] Preferably, the method comprises returning to a "transition" state if any of the first process variable, the second process variable and the third process variable are outside their respective confidence intervals.

[0024] Preferably, the method comprises: if all of the first process variable, the second process variable and the third process variable are within their respective confidence intervals, and PO RATIO Fall on the scheduled PO LIMIT If the value is less than 0, it returns to the "normal" state. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Like reference numerals represent like elements throughout the drawings. It should be understood that the drawings are not necessarily drawn to scale.

[0026] Figure 1 A vibrating meter according to an embodiment is shown;

[0027] Figure 2 shows meter electronics according to an embodiment;

[0028] Figure 3 shows the effect of a magnetic field on a flow meter sensor pick-up voltage according to an embodiment;

[0029] Figure 4 shows the effect of a magnetic field on flow measurement according to an embodiment;

[0030] Figure 5A shows the magnetic field of the pickup assembly without the presence of a magnet;

[0031] Figure 5B shows the magnetic field of a pickup assembly in the presence of an external magnet having a south pole of the magnet oriented toward the pickup assembly;

[0032] Figure 5C shows the magnetic field of a pickup assembly in the presence of an external magnet having a north pole of the magnet oriented toward the pickup assembly;

[0033] Figure 6 shows a flow chart relating to an example of an implementation of magnetic tamper detection;

[0034] Figure 7 shows a flow chart relating to another example implementation of magnetic tamper detection;

[0035] Figure 8 Pseudo code for a magnetic tampering implementation is shown; and

[0036] Fig.9A and Fig. 9B False flag detection of an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0037] Figures 1 to 9BAnd 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.

[0038] 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 driver, pick-off sensor, number of flow conduits, or vibration operating mode.

[0039] The sensor assembly 10 includes a pair of flanges 101 and 101', manifolds 102 and 102', a driver 104, pick-off sensors 105 and 105', and flow conduits 103A and 103B. The driver 104 and the pick-off sensors 105 and 105' are connected to the flow conduits 103A and 103B.

[0040] Flanges 101 and 101′ are attached to manifolds 102 and 102′. In some embodiments, manifolds 102 and 102′ may 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 total amount of process fluid 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′.

[0041] The process fluid may include a liquid. The process fluid may include a gas. The process fluid may include, for example and without limitation, a multiphase fluid, such as a liquid including entrained gas and / or entrained solids. Flow conduits 103A and 103B are selected and appropriately mounted to inlet manifold 102 and outlet manifold 102′ so as to have substantially the same mass distribution, moment of inertia, and elastic modulus about bending axes WW and W′-W′, respectively. Flow conduits 103A and 103B extend outwardly from manifolds 102 and 102′ in a substantially parallel manner.

[0042] 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.

[0043] 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.

[0044] Among other things, the meter electronics 20 processes the left and right speed signals from the pickoff sensors 105 and 105' to calculate flow. The communications path 26 provides input and output means that allow the 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.

[0045] In one embodiment, the meter electronics 20 is configured to vibrate the flow conduits 103A and 103B. The vibration is performed by the driver 104. The meter electronics 20 also receives the resulting vibration signals from the pickoff sensors 105 and 105'. The vibration signals include the vibration response of the flow conduits 103A and 103B. The meter electronics 20 processes the vibration response and determines the response frequency and / or phase difference. The meter electronics 20 processes the vibration response 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.

[0046] 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, triangular conduits, etc. Additional flow meter shapes and / or configurations may be used and are within the scope of the description and claims.

[0047] 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).

[0048] 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.

[0049] The meter electronics 20 includes an interface 201, a processing system 203 in communication with the interface 201, and a storage system 204 in communication with the processing system 203. Although these components are shown as distinct blocks, it should be understood that the meter electronics 20 may include various combinations of integrated and / or discrete components.

[0050] The interface 201 is configured to communicate with the sensor assembly 10 of the flow meter 5. The interface 201 can be configured to be coupled 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, such as with an external device.

[0051] The processing system 203 may include any type of processing system. The processing system 203 is configured to retrieve and execute stored routines to operate the flow meter 5. The storage system 204 may store routines including a flow meter routine 205 and a magnetic field detection routine 209. Other measurement / processing routines are contemplated and are within the scope of the specification and claims. The storage system 204 may store measurements, received values, working values, and other information. In some embodiments, the storage system stores mass flow (m) 221, density (ρ) 225, viscosity (μ) 223, temperature (T) 224, drive gain 306, transducer voltage 303, and any other variable known in the art. The drive gain 306 includes a relative measurement of how much power is consumed by the driver to keep the catheter vibrating at a desired frequency.

[0052] The flow meter routine 205 can generate and store fluid quantification and flow measurements. These values ​​may include approximately instantaneous measurements, or may 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 may include approximately instantaneous values, may include samples, may include average values ​​over time intervals, or may include cumulative values ​​over time intervals. The time interval may 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 within the scope of the specification and claims.

[0053] By placing an external magnet close to the pick-up of a Coriolis meter, the flow reading may change 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.

[0054] Go to Figure 3 , shows that when the pick-off sensors 105 and 105' use magnets and coils, external magnetic fields, whether from electromagnetic sources or permanent magnets, affect the readings of the sensor assembly 10 by monitoring the meter electronics 20. It is apparent that there is a relatively sharp and symmetrical step change.

[0055] Figure 3 The area marked by bracket #1 in FIG. 1 represents the magnet being placed near the pick-off sensor 105' located closest to the flow meter output. When the magnet is placed there, the signal provided by the pick-off sensor 105' located closest to the flow meter output (in Figure 3 Marked as PO OUT ) detects a relatively sharp and symmetrical step change in voltage.

[0056] Figure 3 The area marked by bracket #2 in FIG. 1 represents the magnet being 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 OUT A relatively sharp and symmetrical step change in voltage is also detected in the signal ( Figure 3 Marked as PO IN ) 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.

[0057] 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.

[0058] Steering Figure 4 , showing the effect of an external magnet on 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.

[0059] Figure 4 The area marked by bracket #1 in represents where 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.

[0060] Figure 4 The area marked by bracket #2 in represents where the magnet is placed 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.

[0061] Figure 4The area marked by bracket #3 in represents where 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.

[0062] 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 when there is an external magnet with the south pole of the magnet oriented towards the pickup assembly, and Figure 5C 2 shows the magnetic field when there is 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.

[0063] In an embodiment, the method for detecting magnetic tampering is 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.

[0064] 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.

[0065] 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. ZERO .PO ZERO is the average value captured during the zeroing process:

[0066]

[0067] in:

[0068] RPO ZERO = Average value captured during the zeroing process for RPO

[0069] LPO ZERO = Average value captured during the zeroing process for LPO

[0070] When no flow is passing through the flowmeter, a zeroing process is typically performed 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 allows the flowmeter to be calibrated so that no flow is measured during the no-flow condition.

[0071] In an embodiment, as shown in step 604, the PO RATIO , PO RATIO is the ratio of the pick-off voltages captured during fluid flow and meter operation.

[0072]

[0073] RPO = Voltage value captured during meter operation for RPO

[0074] LPO = voltage value captured during meter operation for LPO

[0075] In an embodiment, as shown in step 606, a PO is established. LIMIT .PO LIMIT is the pick ratio limit, which is the PO that can be allowed before indicating tampering RATIO With PO ZERO 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 LIMIT Varies depending on application.

[0076] In step 608, PO RATIO With PO LIMIT Compare. If PO RATIO In PO LIMIT , the flowmeter is determined to be operating within “normal” operating limits. However, if PO RATIO In PO LIMIT In addition, a flag is generated indicating potential magnetic tampering.

[0077] Under certain flow conditions, this approach may provide a flag indicating tampering even though no tampering is actually present. In an embodiment, to limit the number of "false flags", additional logic is added involving monitoring additional meter outputs. These outputs may include one or more of mass flow, density, and drive gain.

[0078] 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 test variables and pickup ratios are within their confidence intervals. The Flag state implies that all test variables are within their confidence intervals, but the pickup ratios have exited their confidence intervals. The Transition state implies that at least one test variable has exited 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 communications. The digital code can be translated into text for human readable and can be presented to a display.

[0079] 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.

[0080] In step 704, the fluid flow and the pickup voltage ratio captured during meter operation, P0, are calculated according to equation (1). RATIO In step 706, the zero variables (including the pickup voltage ratio) collected over time 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.

[0081] Steps 702 to 706 are iterated during the zero process or zeroed condition. This helps 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 zeroed conditions.

[0082] 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 those 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. RATIO . Use appropriate data structures such as arrays to store PO RATIO The average values ​​and standard deviations of the RPO signal and the LPO signal are stored in the storage system 204 .

[0083] 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 a confidence interval.

[0084] As will be appreciated by those skilled in the art, confidence intervals can be determined empirically based on targeting of desired outcomes. i ) includes:

[0085]

[0086] in:

[0087] = standard deviation of the variable of interest

[0088] deadband = factor that buffers the observable response

[0089] = the mean value of the measurement of the variable of interest

[0090] The deadband is determined empirically to adjust the sensitivity of the system.

[0091] If any of the variables are outside of their corresponding confidence intervals, the "transition" flag state is activated. However, if all of the variables are within their corresponding confidence intervals, the PO is compared in step 712. RATIO Specifically, in step 712, the operation PO RATIO The zero PO previously determined according to steps 702 to 704 RATIO If the operation PO RATIO If the operation PO is within its confidence interval, it returns to "normal". RATIO Outside of its confidence interval, a "flag" status is returned to indicate a potential magnetic tamper event.

[0092] 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 ideal zero value that is 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.

[0093] Returning to step 712, the following is an example of how the flow chart may be arranged in an embodiment. The pseudo code is provided as an aid only for clarity and should not be construed as limiting:

[0094] A first step could be to check for density changes using the density ratio:

[0095]

[0096] in:

[0097] ρ m = measured density

[0098]

[0099] ρ zero = Density reference value

[0100] An example of where the following logic can be applied is in the case of establishing a density ratio:

[0101] Check Status = "Transition"

[0102]

[0103] Check Status = "Transition"

[0104] Else

[0105] Check Status = "Normal"

[0106] Where: l = Density range limit

[0107] Another output check can be the drive gain change using the drive gain ratio:

[0108]

[0109] in:

[0110] Dg m = Measured drive gain

[0111] Dg r =Average drive gain ratio

[0112] Dg zero =Drive gain reference value

[0113] An example of the following logic that can be applied is when establishing a drive gain ratio:

[0114] If D m =100then

[0115] Check Status = "Transition"

[0116] Else if Dg r <=(1-Dg l )then

[0117] Check Status = "Transition"

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

[0119] Check Status = "Transition"

[0120] Else

[0121] Check Status = "Normal"

[0122] Where: Dg l =Drive gain range limit

[0123] Finally, the pick ratio logic is applied, as shown in equation (2). The pick ratio logic can be shown as:

[0124] If PO r <(PO zero -PO limit )then

[0125] Check Status = "Flag"

[0126] If PO r <(PO zero -PO limit )then

[0127] Check Status = "Flag"

[0128] Else

[0129] Check Status = "Normal"

[0130] Among them: PO limit =PO range limit

[0131] 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 embodiments, and the order in which they are analyzed may be different. Fig. 9B , applying the flow condition logic above to the Fig.9A Looking at the PO ratio data for the PO range, it is clear that there are significantly fewer false detections ("false flags") than when using only the pick-up ratio alone to predetermine the PO limit.

[0132] 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. In fact, 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 these other 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.

[0133] 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') 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 the voltage of both pickoff sensors (105, 105') and determine PO RATIO ; wherein the meter electronics (20) is configured to determine the PO RATIO Is it on the scheduled PO? LIMIT within; and Wherein the meter electronics (20) is configured such that: if the PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

2. The Coriolis flow meter (5) according to claim 1, wherein: A first process variable is collected and compared to a first confidence interval; and Wherein the meter electronics (20) is configured to: if the first process variable falls within the first confidence interval and the PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

3. The Coriolis flow meter (5) according to claim 2, wherein: A second process variable is collected and compared to a second confidence interval; and wherein the meter electronics (20) is configured to: if both the first process variable and the second process variable fall within their respective confidence intervals and the PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

4. The Coriolis flow meter (5) according to claim 3, wherein: A third process variable is collected and compared to a third confidence interval; and wherein the meter electronics (20) is configured to: if the first process variable, the second process variable, and the third process variable fall within their respective confidence intervals and the PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

5. The Coriolis flow meter (5) according to claims 2 to 4, wherein: The first process variable, the second process variable, and the third process variable each include one of a flow tube frequency, a drive gain, a fluid density, and a damping factor.

6. The Coriolis flow meter (5) according to claim 1, wherein: The meter electronics (20) collects PO ZERO , and the meter electronics (20) is configured to measure the PO ZERO determining at least one of a mean and a standard deviation; as well as wherein the meter electronics (20) is configured to convert the PO LIMIT Determined to include with the PO ZERO The allowable deviation.

7. The Coriolis flow meter (5) according to claims 2 to 4, wherein: If any of the first process variable, the second process variable, and the third process variable are outside of their respective confidence intervals, the meter electronics returns to a "transition" state.

8. The Coriolis flow meter (5) according to claims 2 to 4, wherein: If all of the first process variable, the second process variable, and the third process variable are within their respective confidence intervals, and the PO RATIO Falling on the scheduled PO LIMIT within , the meter electronics returns to the "normal" state.

9. A method for operating a Coriolis flow meter, comprising: flowing a flowing material through a flow conduit of the flow meter; driving a driver coupled 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; Capture the voltage of the pickup sensor and determine PO RATIO ; Determine the PO RATIO Is it on the scheduled PO? LIMIT within; and If the PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

10. A method for operating a Coriolis flow meter according to claim 9, comprising: collecting a first process variable; comparing the first process variable to a first confidence interval; as well as If the first process variable falls within the first confidence interval and the PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

11. A method for operating a Coriolis flow meter according to claim 10, comprising: collecting a second process variable; comparing the second process variable to a second confidence interval, and wherein the meter electronics (20) is configured to determine if both the first process variable and the second process variable fall within their respective confidence intervals and the PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

12. The method for operating a Coriolis flow meter according to claim 10, comprising: collecting a third process variable; comparing the third process variable to a third confidence interval, and wherein the meter electronics (20) is configured to determine if both the first process variable and the third process variable fall within their respective confidence intervals and the PO RATIO Fall on the scheduled PO LIMIT If the voltage is outside the range of 0, it indicates the presence of an external magnetic field.

13. A method for operating a Coriolis flow meter according to claims 10 to 12, wherein: The first process variable, the second process variable, and the third process variable each include one of a flow tube frequency, a drive gain, a fluid density, and a damping factor.

14. The method for operating a Coriolis flow meter according to claim 9, comprising: Collect PO ZERO ; Regarding the PO ZERO determining at least one of a mean and a standard deviation; and Determine the inclusion of the PO ZERO PO of the allowable deviation LIMIT .

15. A method for operating a Coriolis flow meter according to claims 10 to 12, comprising: If any of the first process variable, the second process variable, and the third process variable are outside of their respective confidence intervals, a "transition" state is returned.

16. A method for operating a Coriolis flow meter according to claims 10 to 12, comprising: If all of the first process variable, the second process variable, and the third process variable are within their respective confidence intervals, and the PO RATIO Falling on the scheduled PO LIMIT If the value is less than 0, it returns to "normal" status.

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