HK1170297A1 - Flow meter and method for detecting a cable fault in a cabling of the flow meter - Google Patents

Abstract

The embodiment of the invention provides a method for detecting a cable fault in a cable circuit of a flow meter. The method comprises the following step of: testing one or more first detection wires and one or more second detection wires of a cable circuit aiming at a detection wire open circuit fault; the method further comprises a step of: if a detection wire open circuit fault is not confirmed in the first detection wires and second detection wires, then testing the first detection wires and second detection wires aiming at a detection connection directional fault; the method further comprises a step of: testing one or more drive wires of the cable circuit aiming at a drive wire open circuit fault; and the method further comprises a step of: if the drive wire open circuit fault is not confirmed in the drive wires, then testing the drive wires aiming at a drive connection directional fault.

Description

Flow meter and method of detecting cable faults in cabling of a flow meter

Technical Field

The invention relates to a flow meter and a method of detecting a cable fault in a cabling of the flow meter.

Background

Vibrating conduit sensors, such as coriolis mass flowmeters, typically operate by detecting the motion of a vibrating conduit containing a flow material. Properties related to the substance in the conduit, such as mass flow and density, may be determined by processing measurement signals received from a motion transducer associated with the conduit. The vibration modes of a mass filled vibration system are generally affected by the combined mass, stiffness and damping characteristics of the mass containing conduit and the mass contained in the conduit.

A typical coriolis mass flowmeter includes one or more conduits that are connected in series in a pipeline or other transport system and convey material, such as fluid, mud, etc., within the system. Each conduit can be considered to have a set of natural vibration modes including, for example, simple bending, torsional, radial, and coupled modes. In a typical coriolis mass flow measurement application, a conduit is excited in one or more vibration modes as a material flows through the conduit, and motion of the conduit is measured at points spaced along the conduit. The excitation is typically provided by an actuator that perturbs the conduit in a periodic manner, for example an electromechanical device such as a voice coil drive. The mass flow rate may be determined by measuring the time delay or phase difference between the motions at the transducer locations. Two such transducers (or pickoff sensors) are typically employed to measure the vibrational response of the flow conduit and are typically located at positions upstream and downstream of the actuator. The two detection sensors are connected to the electronics by cabling (e.g., two separate pairs of wires). The instrument receives signals from the two pickoff sensors and processes the signals to derive a mass flow rate measurement.

When the flow conduit of the coriolis flowmeter is empty, then the phase difference between the two pickoff signals (pickoff signals) is ideally zero. Conversely, during normal operation, the flow through the meter causes a phase shift between the two pickoff signals due to the coriolis effect. The phase shift is proportional to the mass flow through the conduit. Thus, by accurately measuring the signal difference, the flow meter can accurately measure the mass flow rate.

Coriolis flowmeters typically use coils to drive the flow conduit and measure the resulting flow conduit vibrations. In many cases, the flow sensor devices (i.e., flow conduits, pickoff sensors, and drivers) are not integrally mounted with the transmitter electronics. A typical coriolis flow meter includes 9 wires bundled in a cable between the transmitter/meter electronics and the flow sensor device. The cabling typically includes 3 wires for a Resistance Temperature Detector (RTD) sensor, 2 wires for a first pickoff sensor, 2 wires for a second pickoff sensor, and 2 wires for a driver.

Cabling is typically connected by the user in the field. This may cause problems in cabling. Pairs of wires may be interchanged. The wires may become tangled. Poor termination or failed coils can cause an open circuit. For example, if a first pickoff sensor is connected in a first orientation and a second pickoff sensor is connected in a second, opposite orientation, then the phase shift measured during the zeroing operation will be excessive. Similarly, when the wires connected to the driver are interchanged, then the expected phase characteristics will not be observed, and the feedback loop of the drive circuit may drive the response towards zero instead of towards the fundamental frequency.

Another problem that may arise is the disconnection or unconnected wires between components. A broken or unconnected wire may not be detected before the component begins to operate. Diagnosing the fault and resolving the problem at the customer site is costly and time consuming. In addition, the user may be affected by downtime, expense, and frustration.

It is desirable that the transmitter automatically determine if the sensor is properly wired and, if not, correct the problem encountered. In addition, it is necessary to determine whether wiring is correct independent of process variations.

Disclosure of Invention

A meter electronics for detecting a cable fault in a cabling of a flow meter is provided according to an embodiment of the invention. The meter electronics includes first and second pickoff sensors and the cabling is connected to the first and second pickoff sensors. The cabling includes one or more first pickoff wires and one or more second pickoff wires. The meter electronics also includes a signal injection device connected to the cabling. The signal injection device is configured to generate an injection signal and transmit the injection signal into the cabling and to the first and second pickoff sensors. The meter electronics also includes a signal conditioning circuit connected to the cabling. The signal conditioning circuit is configured to receive at least one response signal from at least one of the first and second pickoff sensors in response to the injection signal and determine one or more of a pickoff open wire fault and a pickoff connection orientation fault in one or both of the one or more first pickoff wires and the one or more second pickoff wires of the cabling.

A meter electronics for detecting a cable fault in a cabling of a flow meter is provided according to an embodiment of the invention. The meter electronics includes a driver, first and second pickoff sensors, and the cabling is connected to the first and second pickoff sensors and to the driver. The meter electronics also includes a drive circuit connected to the cabling and configured to generate and transmit a drive signal into the cabling and to the driver. The meter electronics also includes a signal conditioning circuit connected to the cabling. The signal conditioning circuit is configured to receive at least one response signal from at least one of the first and second pickoff sensors in response to the drive signal and determine one or more of an open drive wire fault and a drive connection orientation fault in one or more drive wires of the cabling.

A method for detecting a cable fault in a cabling of a flow meter is provided according to an embodiment of the invention. The method comprises the following steps: an injected signal component of a response signal received from at least one of the first pickoff sensors and the second pickoff sensors is compared to a predetermined pickoff amplitude threshold, and if the injected signal component does not exceed the predetermined pickoff amplitude threshold, a pickoff open wire fault in the respective one or more first pickoff wires or the respective one or more second pickoff wires is determined.

A method for detecting a cable fault in a cabling of a flow meter is provided according to an embodiment of the invention. The method comprises the following steps: a phase difference between a first detected response phase of the first detected response signal and a second detected response phase of the second detected response signal is compared to a predetermined detected phase difference threshold. The first and second pickoff response signals are received from the first and second pickoff sensors via cabling. The method further comprises the following steps: determining that a connection orientation fault is detected if the phase difference exceeds the predetermined detected phase difference threshold.

A method for detecting a cable fault in a cabling of a flow meter is provided according to an embodiment of the invention. The method comprises the following steps: will cross over the driving resistance R at the output of the driving circuit_DIs compared to a predetermined voltage threshold and if the drive resistor voltage does not exceed the predetermined voltage threshold, a driver wire open fault in the one or more driver wires is determined.

A method for detecting a cable fault in a cabling of a flow meter is provided according to an embodiment of the invention. The method comprises the following steps: the response signal phase difference is compared to a predetermined driver phase difference threshold. The response signal phase difference comprises a difference between the response signal phase and the drive signal phase. The response signal phase is received from at least one of the first pickoff sensors and the second pickoff sensors. The method further comprises the following steps: determining a drive connection orientation fault in one or more drive wires if the response signal phase difference exceeds the predetermined drive phase difference threshold.

A method for detecting a cable fault in a cabling of a flow meter is provided according to an embodiment of the invention. The method comprises the following steps: a vibrational response amplitude of the vibrational response is determined, and a driver connection orientation fault in the one or more driver wires is determined if the vibrational response amplitude does not substantially track the drive signal amplitude.

A method for detecting a cable fault in a cabling of a flow meter is provided according to an embodiment of the invention. The method comprises the following steps: one or more first pickoff wires and one or more second pickoff wires of the cabling are tested for pickoff open wire faults. The one or more first pickoff wires and the one or more second pickoff wires are contained in a cabling and are connected to the first pickoff sensors and the second pickoff sensors, respectively. The method further comprises the following steps: testing the one or more first pickoff wires and the one or more second pickoff wires for a pickoff connection orientation fault if it is determined that no open wire fault is pickoff in the one or more first pickoff wires and the one or more second pickoff wires. The method further comprises the following steps: one or more driver wires of the cabling are tested for open driver wire faults. The one or more driver wires are connected to the driver. The method further comprises the following steps: testing the one or more driver wires for a driver connection orientation fault if it is determined that there is no driver wire open fault in the one or more driver wires.

In one aspect of the meter electronics, the signal conditioning circuit is configured to compare an injected signal component of at least one response signal to a predetermined detected amplitude threshold and determine a detected open wire fault in the respective one or more first detected wires or the respective one or more second detected wires if the injected signal component does not exceed the predetermined detected amplitude threshold.

In another aspect of the meter electronics, the signal conditioning circuit receives the first pickoff response signal and the second pickoff response signal, and the signal conditioning circuit is configured to compare a phase difference between the first pickoff response phase and the second pickoff response phase to a predetermined pickoff phase difference threshold and determine a pickoff connection orientation fault in the respective one or more first pickoff wires or the respective one or more second pickoff wires if the phase difference exceeds the predetermined pickoff phase difference threshold.

In yet another aspect of the meter electronics, the signal injection device comprises: a digital-to-analog (D/A) converter configured to receive a digital frequency command and output a frequency input; an injection signal generator that receives a frequency input from the D/a converter and outputs an injection signal of a frequency specified by the frequency input; and a transformer that transmits the injection signal into the cable line.

In yet another aspect of the meter electronics, the signal conditioning circuit is further configured to invert a response signal received from one of the pickoff sensors if it is determined that there is a pickoff connection orientation fault.

In yet another aspect of the meter electronics, the signal conditioning circuit is configured to bridge a drive resistance R at the output of the drive circuit_DIs compared to a predetermined voltage threshold and if the drive resistor voltage does not exceed the predetermined voltage threshold, a driver wire open fault in the one or more driver wires is determined.

In yet another aspect of the meter electronics, the signal conditioning circuit is configured to compare a response signal phase difference to a predetermined driver phase difference threshold, determine a driver connection orientation fault in the one or more driver wires if the response signal phase difference exceeds the predetermined driver phase difference threshold, the response signal phase difference comprising a difference between a response signal phase and a drive signal phase, the response signal phase received from at least one of the first pickoff sensor and the second pickoff sensor.

In yet another aspect of the meter electronics, the meter electronics is further configured to determine a vibrational response amplitude of the vibrational response, and determine a driver connection orientation fault in the one or more driver wires if the vibrational response amplitude does not substantially track the drive signal amplitude.

In yet another aspect of the meter electronics, the drive circuit is further configured to invert the drive signal if it is determined that a drive connection orientation fault exists.

In one embodiment of the method, the method further comprises: an alarm is generated if it is determined that there is a detected open wire fault.

In another embodiment of the method, the comparing and determining further comprises: comparing a first injected signal component of the first response signal from the first pickoff sensor to a predetermined pickoff amplitude threshold, and if the first injected signal component does not exceed the predetermined pickoff amplitude threshold, determining a first pickoff open wire fault in the one or more first pickoff wires; a second injected signal component of the second response signal from the second pickoff sensor is compared to a predetermined pickoff amplitude threshold and if the second injected signal component does not exceed the predetermined pickoff amplitude threshold, a second pickoff open wire fault in the one or more second pickoff wires is determined.

In yet another embodiment of the method, the method further comprises: an alarm is generated if it is determined that there is a detected connection orientation fault.

In yet another embodiment of the method, the method further comprises: after the determining, if it is determined that there is a detected connection orientation fault, a response signal received from one of the detecting sensors is inverted.

In yet another embodiment of the method, the method further comprises: if it is determined that there is an open drive wire fault, an alarm is generated.

In yet another embodiment of the method, the method further comprises: if it is determined that there is a drive connection orientation fault, an alarm is generated.

In yet another embodiment of the method, the method further comprises: after the determining, if it is determined that there is a driver connection orientation fault, the drive signal from the drive circuit is inverted.

In yet another embodiment of the method, the method further comprises: if it is determined that there is a drive connection orientation fault, an alarm is generated.

In yet another embodiment of the method, the method further comprises: after the determining, if it is determined that there is a driver connection orientation fault, the drive signal from the drive circuit is inverted.

In yet another embodiment of the method, the method further comprises: generating an alert if it is determined that an open wire fault exists in the one or more first pickoff wires, in the one or more second pickoff wires, or in the one or more driver wires.

In yet another embodiment of the method, the method further comprises: generating an alert if it is determined that a connection orientation fault exists in the one or more first detected wires, in the one or more second detected wires, or in the one or more driver wires.

In yet another embodiment of the method, the testing one or more pickoff sensors for pickoff open wire faults includes: an injected signal component of a response signal received from at least one of the first pickoff sensors and the second pickoff sensors is compared to a predetermined pickoff amplitude threshold, and if the injected signal component does not exceed the predetermined pickoff amplitude threshold, a pickoff open wire fault in the respective one or more first pickoff wires or the respective one or more second pickoff wires is determined.

In yet another embodiment of the method, the testing the one or more first pickoff wires and the one or more second pickoff wires for pickoff connection orientation faults comprises: comparing a phase difference between a first pickoff response phase of a first pickoff response signal and a second pickoff response phase of a second pickoff response signal to a predetermined pickoff phase difference threshold, receiving the first pickoff response signal and the second pickoff response signal from the first pickoff sensor and the second pickoff sensor via cabling, and determining that a connection orientation fault is pickoff if the phase difference exceeds the predetermined pickoff phase difference threshold.

In yet another embodiment of the method, the method further comprises: after the test for the detected connection orientation fault, if it is determined that a detected connection orientation fault exists, a response signal from one of the detected sensors is inverted.

In yet another embodiment of the method, testing the driver for an open wire includes: will cross over the driving resistance R at the output of the driving circuit_DIs compared to a predetermined voltage threshold and if the drive resistor voltage does not exceed the predetermined voltage threshold, a driver wire open fault in the one or more driver wires is determined.

In yet another embodiment of the method, the testing the one or more driver wires for a driver connection orientation fault includes: comparing a response signal phase difference to a predetermined driver phase difference threshold, the response signal phase difference comprising a difference between a response signal phase and a drive signal phase, the response signal phase received from at least one of the first pickoff sensor and the second pickoff sensor, and determining a driver connection orientation fault in the one or more driver wires if the response signal phase difference exceeds the predetermined driver phase difference threshold.

In yet another embodiment of the method, the testing the one or more driver wires for a driver connection orientation fault includes: determining a vibrational response amplitude of the vibrational response, and determining a driver connection orientation fault in the one or more driver wires if the vibrational response amplitude does not substantially track the drive signal amplitude.

In yet another embodiment of the method, the method further comprises: after the testing the one or more driver wires for driver connection orientation faults, if a driver connection orientation fault is determined to exist, toggling a drive signal from the driver.

Drawings

Fig. 1 illustrates a coriolis flow meter including a flow meter assembly and meter electronics.

FIG. 2 is a diagrammatic view of a portion of a flow meter in accordance with an embodiment of the present invention.

FIG. 3 is a flow chart of a method for detecting a cable fault in a cabling of a flow meter according to one embodiment of the invention.

FIG. 4 is a flow chart of a method for detecting a cable fault in a cabling of a flow meter according to one embodiment of the invention.

FIG. 5 is a flow chart of a method for detecting a cable fault in a cabling of a flow meter according to one embodiment of the invention.

FIG. 6 is a flow chart of a method for detecting a cable fault in a cabling of a flow meter according to one embodiment of the invention.

FIG. 7 is a flow chart of a method for detecting a cable fault in a cabling of a flow meter according to one embodiment of the invention.

FIG. 8 shows a flow meter according to an embodiment of the invention.

Detailed Description

Fig. 1-8 and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Variations from these examples may occur to those skilled in the art, which fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. Accordingly, the present invention is not limited to the specific examples described below, but only by the claims and their equivalents.

Fig. 1 shows a coriolis flow meter 5 comprising a flow meter assembly 10 and meter electronics 20. The meter electronics 20 is connected to the meter assembly 10 via wires 100 to provide density, mass flow rate, volume flow rate, total mass flow, temperature, and other information on the pathway 26. It should be apparent to those skilled in the art that the present invention may be used with any type of coriolis flow meter regardless of the number of drivers, pickoff sensors, flow conduits, or the mode of operation of the vibration. While it will be apparent to those skilled in the art that the present invention may be implemented as a vibrating tube densitometer without the additional measurement capability provided by a coriolis flowmeter, the structure of a coriolis flowmeter is still described.

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

Flanges 101 and 101 'are secured to manifolds 102 and 102'. Manifolds 102 and 102' are secured to opposite ends of spacer 106. Spacers 106 maintain the spacing between manifolds 102 and 102' to avoid undesirable vibrations in flow conduits 103A and 103B. When the flow meter assembly 10 is inserted into a piping system (not shown) carrying the measured material, the material enters the flow meter assembly 10 through the flange 101, passes through the inlet manifold 102 (where the total amount of the material is directed into the flow conduits 103A and 103B), flows through the flow conduits 103A and 103B and returns to the outlet manifold 102 '(where the material exits the flow meter assembly 10 through the flange 101').

Flow conduits 103A and 103B are selected and properly mounted to inlet manifold 102 and outlet manifold 102 ' such that the flow conduits have substantially the same mass distribution, moment of inertia, and elastic modulus about bending axes W-W and W ' -W ', respectively. The flow conduits extend outwardly from the manifold in a substantially parallel manner.

The flow conduits 103A-B are driven by the driver 104 in opposite directions about their respective bending axes W and W' in a first output (first out) of a so-called meter bending mode. Driver 104 may comprise one of many well-known devices, such as a magnet mounted to flow conduit 103A and a counter-acting coil mounted to flow conduit 103B. An alternating current is passed through the counter-acting coil to cause the two conduits to oscillate. Appropriate drive signals are provided by the meter electronics 20 to the driver 104 via wires 110.

The meter electronics 20 receives sensor signals on wires 111 and 111', respectively. The meter electronics 20 generates a drive signal on the lead 110 that causes the driver 104 to oscillate the flow conduits 103A and 103B. The meter electronics 20 processes the left and right velocity signals from the pickoff sensors 105 and 105' to calculate the mass flow rate. The passageway 26 provides input and output means that allow the meter electronics 20 to interact with an operator. The description of fig. 1 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.

Fig. 2 is a diagrammatic view of a portion of a flow meter 5 in accordance with an embodiment of the present invention. The flow meter 5 includes a first pickoff sensor 201a, a second pickoff sensor 201b, a driver 204, and meter electronics 20. The meter electronics 20 can operate as a mass flow meter or can operate as a density meter, including operating as a coriolis flow meter. The meter electronics 20 may include, among other components, a driver circuit 220, a signal injection device 203, and a signal conditioning circuit 202. The meter electronics 20 is connected to the pickoff sensors 201 and the driver 204 by cabling 205. Cabling 205 connects the first pickoff sensors 201a and the second pickoff sensors 201b to the signal conditioning circuit 202 and the signal injection device 203. Cabling 205 connects the driver 204 to the driver circuit 220. In one embodiment, the signal conditioning circuit 202 and the signal injection device 203 are interconnected by a line 210.

Cabling 205 may include any form of wire, cable, fiber, etc. that electrically connects the first and second pickoff sensors 201a and 201b to the signal conditioning circuit 202. In one embodiment, cabling 205 includes at least a portion of conductor 100 of fig. 1.

A typical flow meter includes 9 wires bundled in a cabling 205 between the transmitter/meter electronics 20 and the flow meter assembly 10. Cabling 205 typically includes 3 wires for a Resistance Temperature Detector (RTD) sensor, 2 wires for a first pickoff sensor, 2 wires for a second pickoff sensor, and 2 wires for a driver.

In one embodiment, the meter electronics 20 may make a cable fault determination for the cabling 205 between the meter electronics 20 and the pickoff sensors 201a, 201 b. In one embodiment, the meter electronics 20 may make a cable fault determination on the cabling 205 between the meter electronics 20 and the driver 204.

The driving circuit 220 generates a driving signal and transmits the driving signal to the driver 204. The driver 204 vibrates the flow conduits 103A and 103B in accordance with the drive signal. The drive signal thus comprises an amplitude characteristic and a frequency characteristic. When meter electronics 20 implements closed loop driving, the difference between the drive signal and the response signal is used as feedback to modify the drive signal. For example, the phase difference between the drive signal and the response signal may comprise the feedback. Ideally, under no-flow conditions, if the flow meter is accurately calibrated, the phase difference will be substantially zero.

The driving circuit 220 may generate a driving signal. In one embodiment, the drive signal comprises an operational drive signal generated by the drive circuit 220, wherein the signal causes the flow conduit 103 to vibrate. The resulting response signal to the drive signal may be received in the signal conditioning circuit 202. Alternatively, the drive signal may be generated according to the invention specifically for fault testing.

The signal injection device 203 may generate an injection signal and may transmit the injection signal to one or both of the first and second pickoff sensors 201a, 201b via the cabling 205. The signal injection device 203 may generate an injection signal based on an injection signal command that may be received from the signal conditioning circuit 202 via line 210. The injection signal may comprise any desired frequency. The injection signal may comprise a frequency higher, lower or equal to the drive signal.

The signal conditioning circuit 202 receives response signals from both the detection sensors 201a and 201 b. The signal conditioning circuit 202 may detect and/or process the response signal. The signal conditioning circuit 202 may process the response signal to generate an appropriate flow measurement. Additionally, according to embodiments of the present invention, the signal conditioning circuit 202 may process the response signal to detect a fault in the cabling 205.

The response signal may be generated by the pickoff sensors 201 in accordance with normal operation of the flow meter 5. Alternatively, the response signal may be generated by the pickoff sensors 201 in response to any form of test vibration of the flow conduit 103. In another alternative, the response signal may be generated by the pickoff sensor 201 in response to an injection signal from the signal injection device 203.

Signal conditioning circuitry 202 may determine a response signal amplitude for each of the detected sensors. The signal conditioning circuit 202 may determine a phase difference between the response signals received from the first pickoff sensors 201a and the second pickoff sensors 201 b. The amplitude and phase difference may be used to determine a connection orientation fault in the cabling 205.

In one embodiment, the meter electronics 20 may include a processor (not shown) and a cable fault diagnostic software program. The processor may execute a cable fault diagnostic software program for the cabling 205 and may initiate and monitor the determination of open wire and connection orientation faults. The cable fault diagnosis software program may initiate signals into the pickoff sensors 201a and 201 b. The processor and program may receive measurements/data from open wire and connection orientation fault tests and may make appropriate fault determinations. The processor and program may generate an alert if a problem is detected. Additionally, the processor and program may implement compensation techniques, including flipping the signal or signal response to compensate for improper wire orientation. Alternatively, the signal conditioning circuit 202, the signal injection device 203, the drive circuit 220, and the processor may comprise equivalent circuits and/or dedicated circuit components that accomplish the above described operations.

FIG. 3 is a flow chart 300 of a method for detecting a cable fault in a cabling of a flow meter according to one embodiment of the invention. In this method, a detected open-wire fault determination is performed. The detect open wire fault test may detect an open wire fault, such as a broken or unconnected one of the respective detected wires of the cabling 205.

In step 301, the injected signal is transmitted into one or more of the pickoff wires of the cabling 205. Accordingly, the injection signal is transmitted to at least one of the first and second detection sensors 201a and 201 b. For example, the injection signal may be generated by the signal injection device 203. When the injection signal is generated by the signal injection device 203, the signal conditioning circuit 202 should receive the response signals from the pickoff sensors 201a and 201b substantially simultaneously.

In step 302, the response signal is compared to a predetermined detected amplitude threshold. The injection signal sent to the detection sensor 201 will generate two different return signals for the signal conditioning circuit 202 only when the detection wire is not open. The first signal (the injection signal component) is a reflection of the injection signal and is at substantially the same frequency as the injection signal. If it is detected that the wire is not open, the injected signal component should be similar in magnitude to the injected signal and therefore comparable to the threshold. Due to the vibration effect of the flow conduit 103 and due to the influence of the flowing substance of the flow channel 103, the second signal is a response signal component and differs in frequency from the original injection signal. However, the response signal component may vary in amplitude and may be undetectable in some cases. Thus, in one embodiment, the injected signal component of the response signal is used for comparison.

In step 303, if the injected signal component does not exceed the predetermined detected amplitude threshold, the method proceeds to step 304. At step 304, it is determined that the response signal is not received and that the wires of the respective detected sensors are disconnected or unconnected. Otherwise, if the injected signal component exceeds the predetermined detected amplitude threshold, the method branches around step 304. Thus, it is determined that the response signal has been received and that the corresponding detected wire is not disconnected or not connected.

In step 304, because the injected signal component does not exceed the predetermined pickoff amplitude threshold, the corresponding pickoff wire is determined to have an open wire fault. Subsequently, meter electronics 20 may perform other functions, including generating an alarm indicating an open wire fault.

The above steps are discussed in the context of a single pickoff sensor and a single response signal amplitude. However, it should be understood that step 302 and 304 may be performed for both response signals from the detection sensors 201a and 201 b.

FIG. 4 is a flow chart 400 of a method for detecting a cable fault in a cabling of a flow meter according to one embodiment of the invention. In the method, a detected sensor connection orientation fault determination is performed.

In step 401, response signals are received from one or both pickoff sensors via cabling 205 in response to drive signals applied by the driver 204.

Under no flow conditions in the flow meter 5, the phase difference between the left and right (or first and second) detected signals will be substantially zero. Under flow conditions, the phase of the first pickoff signal will differ from the phase of the second pickoff signal by a relatively small amount depending on the mass flow rate of the flow material through the flow meter 5. However, if the phase difference between the two detected signals is too large, then a connection orientation fault exists.

In step 402, the phase difference is compared to a predetermined detected phase difference threshold. The phase difference comprises a difference between the phase of the response signal and the phase of the drive signal.

In step 403, if the phase difference exceeds a predetermined detected phase difference threshold, the method proceeds to step 404. If the phase difference does not exceed the predetermined detected phase difference threshold, the method branches around step 404.

In step 404, because the phase difference exceeds a predetermined pickoff phase difference threshold, it is determined that a connection orientation fault exists in the corresponding pickoff wire. For example, the two response signals may have a phase difference of about 180 degrees, plus or minus a relatively small portion of the phase difference caused by the response to the flow material in the flow conduit 103. As previously described, an alarm condition may be generated if it is determined that a connection orientation fault exists. In addition, the meter electronics 20 may flip all subsequent response signals received from the affected pickoff sensors. In this way, improper connection orientations can be corrected.

The above steps are discussed in the context of a single pickoff sensor and a single phase difference. However, it should be understood that steps 402 and 404 may be performed for both response signals from the detection sensors 201a and 201 b.

Fig. 5 is a flow chart 500 of a method for detecting a cable fault in the cabling 205 of a flow meter according to one embodiment of the invention. In the method, a driver open wire fault determination is made. The driver open wire fault test may detect an open wire fault, such as a broken or unconnected wire.

In step 501, a drive signal is transmitted into one or more driver wires of cabling 205 and to driver 204. The driving signal may be generated by the driving circuit 220, as previously described. The drive signal may comprise a normal operation drive signal or may comprise any signal suitable for open wire fault testing.

Referring back to fig. 2, the driving circuit 220 includes a driving resistor R in an output terminal_D. Operational amplifier 221 is connected across driving resistor R_D. In one embodiment, the operational amplifier 221 amplifies across the drive resistor R_DAnd outputs a driving resistance voltage. The drive resistor voltage may comprise an analog voltage signal that may be compared to a predetermined voltage threshold.

Ginseng to radix et rhizoma RheiReferring to FIG. 5, in step 502, a resistor R is driven across_DIs compared to a predetermined voltage threshold. If the drive resistor voltage at the output of the operational amplifier 221 exceeds a predetermined voltage threshold, a desired level of current flows through the cabling 205 to the driver 204.

In step 503, if the drive resistor voltage does not exceed the predetermined voltage threshold, the method proceeds to step 504. Otherwise, if the drive resistor voltage exceeds the predetermined voltage threshold, then it may be determined that an open wire condition does not exist, and the method branches around step 504.

In step 504, it may be determined that a driver open wire condition exists in the cabling 205 to the driver 204 because the drive resistor voltage does not exceed the predetermined voltage threshold. This step may include generating an alarm condition, as previously described.

Alternatively, the operational amplifier 221 may include a comparator device that will drive the resistor R_DThe voltage on the side of the cabling is compared to a certain voltage (i.e., a predetermined voltage threshold) and a true or false digital output is produced. Thus, the digital output includes a first digital output level if the drive resistor voltage exceeds the predetermined voltage and a second digital output level if the drive resistor voltage does not exceed the predetermined voltage. The comparison of step 502 may thus comprise an internal comparison of the comparator means, wherein the predetermined voltage threshold comprises a voltage input to the comparator means.

FIG. 6 is a flow chart 600 of a method for detecting a cable fault in a cabling of a flow meter according to one embodiment of the invention. In the method, a drive connection orientation fault determination is made.

In step 601, the driver circuit 220 generates and transmits a drive signal to the driver 204 via the cabling 205, as previously described. Thus, the driver 204 uses the drive signal to generate a physical stimulus in the flow conduits 103A and 103B. Thus, the signal conditioning circuit 202 receives the first and second response signals from the first and second pickoff sensors 201a and 201b via cabling 205 in response to vibration of the flow conduit caused by the driver 204.

In step 602, the response signal phase difference is compared to a predetermined driver phase difference threshold. The response signal phase difference comprises a difference between the response signal phase and the drive signal phase. The drive signal phase is a phase characteristic provided to drive circuit 220, i.e., the drive signal phase is the drive phase to be achieved by drive circuit 220 and driver 204. The actual phase of the response should be close to this phase and generally differs in the mass flow rate of the flowing substance in the flow conduit 103.

In step 603, if the response signal phase difference exceeds a predetermined driver phase difference threshold, then a driver connection orientation fault is determined to be in the driver wires, and the method proceeds to step 604. Otherwise, if the response signal phase difference does not exceed the predetermined drive phase difference threshold, then the drive connection orientation is determined to be correct and the method branches around step 604.

In step 604, it is determined that a drive connection orientation fault exists in the drive wires because the response signal phase difference exceeds the predetermined drive phase difference threshold. For example, the phase difference may have a phase difference of about 180 degrees, plus or minus a relatively small portion of the phase difference caused by the response to the flow material in the flow conduit 103. As previously described, an alarm condition may be generated if it is determined that a connection orientation fault exists. In addition, the meter electronics 20 may invert the drive signal. For example, the drive signal may be inverted before it is sent to the driver 204. In this way, improper drive connection orientation can be corrected.

It should be appreciated that either of the methods of fig. 6 or 7 may be used to make the drive connection orientation fault determination.

FIG. 7 is a flow chart 700 of a method for detecting a cable fault in a cabling of a flow meter according to one embodiment of the invention. In the method, a drive connection orientation fault determination is made.

In step 701, the vibrational response amplitude is determined. The vibrational response amplitude may comprise the amplitude of the response signal from either sensor.

In step 702, the vibrational response amplitude is compared to the drive signal amplitude. The comparison may be a comparison of two amplitudes at one or more instantaneous points in time. Alternatively, the comparison may be of an average or filtered value, or the like.

In step 703, if the vibrational response amplitude substantially tracks the drive signal amplitude, the method exits. If the vibrational response amplitude does not substantially track the drive signal amplitude, the method proceeds to step 704.

In step 704, a determination is made that a driver connection orientation fault exists in the driver wires because the vibrational response amplitude does not substantially track the drive signal amplitude. As previously described, an alarm condition may be generated if it is determined that a drive connection orientation fault exists. In addition, the meter electronics 20 may invert the drive signal. For example, the drive signal may be inverted before it is sent to the driver 204. In this way, improper drive connection orientation can be corrected.

Fig. 8 shows a flow meter 5 according to an embodiment of the invention. The same components as in fig. 2 have the same reference numerals. In this embodiment, the signal injection device 203 includes a digital-to-analog (D/a) converter 808, an injection signal generator 806, and a transformer 807. The D/a 808 is connected to the signal conditioning circuit 202 and to the injection signal generator 806. The injection signal generator 806 is also connected to a transformer 807.

D/a 808 receives digital frequency instructions from signal conditioning circuitry 202. D/a 808 converts the digital frequency command into a frequency input into injection signal generator 806, where the frequency input specifies the frequency of the (single) injection signal to be generated. Injection signal generator 806 generates an injection signal and transmits the injection signal to primary winding 810 of transformer 807.

The transformer 807 generates the first and second injection signals by utilizing separate transformer secondaries, wherein the secondary windings 811 of the transformer 807 comprise substantially equal pairs of secondary windings. Thus, the injection signal at the primary winding 810 of the transformer 807 is converted into first and second injection signals at the secondary winding 811. The two secondary windings 811 are connected to the cabling 205 and to the first and second pickoff sensors 201a and 201b, into which signals can be injected. As previously described, the signal conditioning circuit 202 receives the first and second response signals resulting from injecting the first and second injection signals.

Claims (3)

1. A method for detecting a cable fault in a cabling of a flow meter, the method characterized by:

comparing a phase difference between a first pickoff response phase of a first pickoff response signal and a second pickoff response phase of a second pickoff response signal to a predetermined pickoff phase difference threshold, the first pickoff response signal and the second pickoff response signal being received from the first pickoff sensor and the second pickoff sensor via the cabling; and

determining that a connection orientation fault is detected if the phase difference exceeds the predetermined detected phase difference threshold.

2. The method of claim 1, further comprising: an alarm is generated if it is determined that there is a detected connection orientation fault.

3. The method of claim 1, further comprising: after the determining, if it is determined that there is a detected connection orientation fault, a response signal received from one of the detecting sensors is inverted.