Coriolis flow meter and method for determining a signal difference in cabling and first and second pickoff sensors

Background of the invention

1. Field of the Invention

The present invention relates to a Coriolis flow meter and a method for determining the difference of signals in cabling and first and second shift sensors.

2. Presentation of the problem

Vibrating conduit sensors, such as Coriolis mass flow meters, usually detect movement of the vibrating conduit that contains flowing material. Material properties in the conduit, such as mass flow, density and the like, can be determined by processing the measurement signals received from motion transducers associated with the conduit. Vibration modes of the oscillating system, filled with material, are usually modified by the combined characteristics of mass, stiffness and attenuation of the conductor and the material contained in it.

A typical Coriolis mass flow meter includes one or more lines that are connected in series with a pipeline or other transport system and carry material, e.g. fluids, sludges, and the like in the system. Each cable can be treated as having a set of natural vibration modes, including, for simple bending, torsional, radial modes and in a typical mass flowmeter application

Coriolis conductor is excited to one or more vibration modes, while material flows through the conductor and the movement of the conductor is measured at points along the conductor. Excitation is usually performed by an actuator, e.g., coupled, electromagnetic device, such as speaker coil drive, transducers. displacement) which periodically stimulates the cable. The mass flow rate can be determined by measuring the delay or phase difference between movements at the attachment points. Two such transducers (or sensors are usually used to measure the oscillatory response of a flow conduit or wires and are usually located in front of and behind the actuator. Two displacement sensors are connected to the device electronic by means of cabling, for example, two independent pairs of wires. The device receives signals from both displacement sensors and processes the signals to measure the mass flow rate.

When the Coriolis flowmeter tube or leads are empty, the phase difference between the two offset signals is perfectly zero. On the contrary, during normal operation, the flow through the flow meter causes a phase shift between two shift signals under the influence of the Coriolis effect. The phase shift is directly proportional to the flow of material through the wires. Thus, by measuring the exact difference between the signals, the flow meter can accurately measure the mass flow rate.

Determining the difference between the signals from the shift sensors is an important activity of the flow meter. Signal determination must be accurate, although the wiring between devices affects the measurement signals, they are characterized by natural and the devices must be made with sensors and all cables have distributed inductive, capacitive resistive characteristics. In addition, the shift sensors can have natural characteristics that further affect the difference between the signals. Each offset signal must travel through the cabling, and therefore signal accuracy can be reduced before the signal reaches the flowmeter measuring device.

Typical flowmeter wiring can vary in length depending on the environment and installation method. Meter wiring can reach 304.8 m (1000 ft). Distributed cable parameters, such as natural inductance, capacitance and resistance, introduce some signal differences to the sinusoidal signal running through the cabling. As a result, at the end of the cable, two independent measurement signals running through the cables may show a signal difference introduced by the cables if the signals are not subjected to exactly the same cable parameters. Because the measuring devices relate the difference between the signals to the mass flow, the wiring and sensors layout introduces an undesirable error in the flow measurement.

In addition to the mismatch between two pairs of cables, the distributed parameters of the cabling system and sensors change with temperature. Temperature changes may require a reset operation when, for example, a flow meter is installed, or when the ambient temperature changes more than a certain amount. During a reset operation (i.e. under no-flow conditions), the device captures the signal difference generated by the system (including travel measurement mismatch, wiring mismatch, measurement device mismatch) and subtracts this offset from all subsequent phase measurements. However, one-time zeroing does not guarantee proper operation, as the cabling / sensor characteristics can and usually change over time.

Known flow meters do not autonomously and continuously compensate for signal differences resulting from the natural characteristics of cabling and travel sensors. Known flow meters do not compensate outside the meter electronics.

The essence of the invention

The present invention helps to solve problems related to the natural characteristics of the cabling and flowmeter travel sensors.

A Coriolis flow meter is shown according to an embodiment of the invention. The Coriolis flow meter includes first and second travel sensors, wiring connected to first and second travel sensors, and a signal input device connected to the wiring. The signal input device is configured to generate one or more reference signals, the one or more reference signals having a substantially identical phase. The signal input device is further adapted to communicate with one or more reference signals in the cabling and with first and second travel sensors. The Coriolis flow meter further includes a signal conditioning circuit connected to the cabling. The signal conditioning circuit is further adapted to receive first and second response signals from the cabling and the first and second travel sensors in response to one or more reference signals and to determine the signal difference between the first and second response signals.

A method for determining the difference of signals in cabling and first and second pickoff sensors in a Coriolis flow meter is shown according to an embodiment of the invention. The method includes generating one or more reference signals, the one or more reference signals having a substantially identical phase, transmitting one or more reference signals to the cabling and the first and second pickoff sensors, and determining the signal difference between the first and second response signals that returned from the wiring and first and second feed sensors in response to one or more reference signals.

ASPECTS

In one aspect, the signal input device includes a digital-to-analog (D / A) converter adapted to receive a digital frequency command and generate an input frequency signal, a reference signal generator that receives the input frequency signal from the D / A converter and generates a single reference signal frequency determined by the input frequency signal and transformer, which converts a single reference signal into one or more reference signals.

In another aspect, the transformer is an iron core transformer.

In yet another aspect, the transformer comprises a primary winding and first and second secondary windings, wherein the ratio of the primary windings to the first and second secondary windings is basically 7: 1: 1.

In yet another aspect, the D / A converter receives a digital frequency command from the signal conditioning circuit.

In yet another aspect, the one or more reference signals have substantially identical phases and amplitude.

In yet another aspect, the signal difference is substantially removed from the first and second measurement signals by the signal conditioning circuit, the first and second measurement signals being generated by first and second pickoff sensors in response to flow conduit vibrations.

In yet another aspect, the signal conditioning circuit is further adapted to compensate for the cabling and the first and second pickoff sensors, using the signal difference.

In yet another aspect, the signal conditioning circuit is further adapted to periodically compensate the cabling and the first and second pickoff sensors using the signal difference.

In yet another aspect, the first and second response signals have a different frequency from the first and second measurement signals, wherein the first and second measurement signals are generated by first and second pickoff sensors in response to flow conduit vibrations.

In yet another aspect, the first and second response signals have substantially the same frequency as the first and second measurement signals, the first and second measurement signals being generated by first and second pickoff sensors in response to flow conduit vibrations.

In yet another aspect, the signal conditioning circuit is further adapted to use the first and second response signals to detect openings in the cabling and in the first and second pickoff sensors.

In yet another aspect, the signal conditioning circuit is further adapted to use the first and second response signals to detect a short circuit in the cabling and in the first and second pickoff sensors.

In yet another aspect, the signal conditioning circuit is further adapted to use the first and second response signals for automatic gain control.

In yet another aspect, the signal conditioning circuit receives one or more reference signals together with the first and second response signals, wherein the signal conditioning circuit is further adapted to remove one or more reference signals.

Description of drawings

Fig. 1 shows a Coriolis flow meter comprising a flow meter assembly and meter electronics.

Fig. 2 is a schematic of a Coriolis flow meter according to an embodiment of the invention.

Fig. 3 shows the algorithm of the method for determining the signal difference in cabling and first and second pickoff sensors in a Coriolis flow meter according to an embodiment of the invention.

Fig. 4 shows a Coriolis flow meter according to another embodiment of the invention.

Fig. 5 shows an algorithm of the method for determining the signal difference according to another embodiment of the invention.

Detailed description of the invention

Figures 1-5 and the following description show selected examples to show those skilled in the art how to make and use the best embodiment of the invention. In order to present the principles of the invention, certain traditional aspects have been simplified or omitted.

those skilled in the art will recognize these modifications are within the scope of the invention, and those skilled in the art will recognize that the properties described below can be combined in a variety of ways to achieve many modifications of the invention. As a result, the invention is not limited to the specific examples described below by the claims and their equivalents.

Fig. 1 shows a flow meter comprising the flow meter assembly 10 and the meter electronics 20. The meter 20 electronics are connected to the flow meter assembly 10 through wires 100 to

Experts in examples, Experts in given data but only

Coriolis 5, providing information on density, mass flow rate, volumetric flow rate, total flow rate, temperature and more over a link

26. It should be apparent to those skilled in the art that the present invention can be used in any type of Coriolis flow meter regardless of the number of actuators, travel sensors, flow conduits, or operating vibration mode.

The flow meter assembly 10 includes a pair of orifices 101 and 101 ', manifolds 102 and 102', actuator 104, travel sensors 105-105 ', and flow lines 103A and 103B. Actuator 104 and travel sensors 105 and 105 'are connected to flow lines 103A and 103B.

The flanges 101 and 101 'are attached to the manifolds 102 and 102'. Pipe branches 102 and 102 'are attached to opposite ends of the distance 106. The distance 106 maintains the distance between the pipe branches 102 and 102', preventing unwanted vibrations in the flow conduits 103A and 103B. When the flowmeter assembly 10 is installed in a pipeline system (not shown) through which the measured material is sent, the material is introduced into the flowmeter assembly 10 through the orifice 101, passing the input manifold 102, where the total amount of material is directed to the flow conduits 103A and 103B , flows through the flow conduits 103A and 103B and returns to the outlet manifold 102 'in which it exits the meter assembly 10 through the orifice 101'.

The flow conduits 103A and 103B are selected and properly mounted on the input pipe manifold 102 and the output pipe manifold 102 'so that they have essentially the same mass distribution, moments of inertia, and elastic modules around the bending axis WW and W'-W, respectively. The flow conduits extend outwardly from the pipe branches in a substantially parallel manner.

The flow conduits 103A-B are moved by the actuator 104 in opposite directions around their respective bending axes W and W 'and according to the so-called first flow meter bending mode. Actuator 104 may be one of many known devices such as a magnet mounted on flow conduit 103A and an opposite coil mounted on flow conduit 103B. Alternating current is passed through the coil to cause both wires to oscillate. The appropriate control signal is supplied by the meter electronics 20 via a 110 wire to the actuator 104.

The meter electronics 20 receive sensor signals through wires 111 and 111 'respectively. The meter electronics 20 generate a control signal in the conduit 110, which causes the actuator 104 to cause oscillations of the flow conduits 103A and 103B. The meter electronics 20 process the left and right speed signals from the travel sensors 105 and 105 'to calculate the mass flow rate. Link 26 provides input and output means that allow meter electronics 20 to communicate with the operator. The description of Fig. 1 is given only as an example of the operation of a Coriolis flow meter and is not intended to limit the scope of the present invention.

Fig. 2 shows a schematic of a Coriolis flow meter 200 according to an embodiment of the invention. The flow meter 200 includes a first travel sensor 201a, a second travel sensor 201b, a signal conditioning circuit 202 and a signal input device 203. The circuit 202 is connected and the second 20b signal device 203 is also connected to the wiring 205. In one embodiment, the signal input device 203 and the signal conditioning circuit 202 are components of the meter electronics 20 (see Fig. 1).

conditioning the first shift signals 201a cabling 205. In addition, with sensors using introductory

The first travel sensors 201a and the second 201b are connected to the signal conditioning circuit 202 via wiring 205. Wiring 205 may include any form of wires, wires, fibers etc. that electrically connect the first and second travel sensors 201a and the signal conditioning circuit 201b. Wiring 205 in one embodiment is the wires 100 of Fig. 1. Consequently, signal conditioning circuit 202 receives first and second measurement signals from the first and second travel sensors 201a and 201b through wiring 205 in response to vibrations of the flow conduit or flow conduits 5.

The signal input device 203 generates first and second reference signals. The first and second reference signals have substantially identical phases. Alternatively, the first and second reference signals may be substantially identical in both phase and amplitude. It should be noted that the signal input device 203 can generate one reference signal, the one reference signal being transmitted to both the travel sensor 201a and 201b, as the signal input device 203 of Fig. 4. The signal input device 203 transmits the first reference signals and a second for wiring 205 and first travel sensors 201a and second 201b. The signal input device 203 may therefore introduce first and second reference signals into the wiring 205 and the first and second pickoff sensors 201a and 201b. Consequently, the first and second response signals are generated by the first and second pickoff sensors 201a and 201b in response to reference signals. The response signals are reflections of the reference signals, whereby the response signals may show a signal difference between the first and second response signals as a result of the different natural characteristics of the cabling 205 and the travel sensors 201. The signal difference may be the phase difference, the time delay, the shift difference caused by the Coriolis effect etc. . Natural characteristics may include, for example, distributed inductance, capacitance and resistance characteristics of cabling 205 and travel sensors 201. The signal difference may be received, detected and measured by signal conditioning circuit 202. Note that the signal difference can be any value, including zero, if the sensor system is in perfect balance. The signal difference generated by the cabling 205 and travel sensors 201 can therefore be determined and measured.

Signal conditioning circuit 202 processes the first and second measurement signals to generate mass flow rate measurement results. In addition, the signal conditioning circuit 202 determines the difference of signals between the first and second response signals that are returned from the wiring 205 and the first and second pickoff sensors 201a and 201b in response to the first and second reference signals. Signal conditioning circuit 202 may remove the first and second reference signals from the first and second response signals to then process the first and second response signals. The signal conditioning circuit 202 in one embodiment filters the first and second reference signals from the first and second response signals, for example using digital filters. The removal of reference signals is discussed in more detail with reference to Fig. 5 and accompanying text.

The signal difference in one embodiment is used to compensate for the flow meter 5. The signal difference may be subtracted from or otherwise removed from the measurement signals in the signal conditioning circuit 202. In this way, the flow meter 5 can zero the effects on the flow meter 5, resulting from types of cabling and sensors, cabling length, temperature effects on cabling and sensors, can detect breaks and / or defects in the production of cabling and sensors, etc.

Because the introduced reference signals have zero phase difference, any signal differences, measured by the signal conditioning circuit 202, result from a mismatch between the two signal paths, including phenomena caused by temperature. Because the compensation signal is introduced into the wires, any offsets caused by the cables are also measured. Thus, the signal conditioning circuit 202 can regulate the actual measurement made by the shift sensors by any signal difference measured in the system compensation signal. The final result is a flow-compensated flow measurement, including phase-compensated flow measurement.

In one embodiment, the signal difference is subtracted from the measurement signals. In another embodiment, the signal difference value is a multiplier or ratio. Consequently, the measurement signals can be multiplied by a signal difference multiplier or a signal difference ratio to perform compensation. It should be understood that other compensation methods may be used and fall within the scope of the description and claims.

It should be noted that the first and second reference signals may have a higher or lower frequency than the measurement signals (the frequency of the measurement signal depends on the frequency of the vibrations of the flow conduit or wires and the response of the flow meter 5 to material flow). Alternatively, the first and second reference signals may have the same frequency as the measurement signals.

The first and second reference signals may be generated in a substantially continuous manner and the signal conditioning circuit 202 may thus continuously receive the response signals and perform compensation. Alternatively, the first and second reference signals may be generated periodically and may be used to perform compensation at specific intervals.

The signal conditioning circuit 202 may include a processor (not shown) and software procedures for determining signal difference and compensation. Consequently, the processor can perform the procedure, can control the generation of the first and second reference signals, can receive the first and second response signals, and can determine the signal difference between the first and second response signals. Alternatively, the signal conditioning circuit 202 may include equivalent circuit and / or specialized circuit components that perform the above operations.

Fig. 3 illustrates an algorithm 300 for determining the signal difference in cabling 205 and first travel sensors 201a and second 201b according to an embodiment of the invention. At 301, the signal input device 203 generates first and second reference signals. The first and second reference signals have substantially identical phases. The first and second reference signals in one embodiment have substantially identical phases and amplitudes. However, it should be noted that the amplitudes of the first and second reference signals need not be the same.

At step 302, the first and second reference signals are input to the wiring 205 and to the first and second travel sensors 201a and 201b through the signal input device 203. The first and second reference signals introduced will generate first and second response signals. The first and second response signals may be received by the signal conditioning circuit 202.

At step 303, the signal difference between the first and second response signals is determined. Determining the signal difference may be performed, for example, by signal conditioning circuit 202. The signal difference may be due to sensor system characteristics, such as inductance, capacitance and resistance, occurring, for example, in wiring 205 and first travel sensors 201a and second 201b. The signal difference may be phase difference, time delay, shift difference caused by the Coriolis effect etc.

At step 304, compensation is performed using the determined signal difference. This compensation may be performed, for example, by signal conditioning circuit 202. Compensation may be performed to substantially remove the signal difference caused by the cabling 205 and the first and second pickoff sensors 201a and 201b. The compensation can be, for example, phase compensation.

In addition, the reference signal input can also be used for other purposes. In one embodiment, the first and second response signals may be used to automatically adjust the gain in the flow meter 5. Consequently, the first and second response signals may be used to determine the amplitudes of the first and second reference signals to generate the first and second reference signals by , basically, the same amplitudes.

In one embodiment, the first and second response signals may be used to detect open and / or short-circuit conditions in the travel sensors 201. In this embodiment, if the first or second response signal is not received, the signal conditioning circuit 202 may determine that the appropriate the feed sensor and / or some wiring are short-circuited. Alternatively, if the first or second response signal is immediately and substantially completely reflected, the signal conditioning circuit 202 may determine that the corresponding travel sensor and / or some wiring are open. In any case, the signal conditioning circuit 202 may determine an abnormal condition and take appropriate action, such as, for example, generating an alarm or sending a malfunction message. In addition, the perimeter 202 sets the distance less than the response length first and

The D / A converter of the signal conditioning can optionally measure the reflection time and determine the length of the cabling 205. Furthermore, the signal conditioning circuit 202 can optionally determine the location of the break or damage in the wiring 205 through to the reflection site which is wiring 205. In addition, the second signals can be used to detect faulty wiring or incorrect installation at the flow meter user's 5.

In one embodiment, the first and second response signals may be used to detect errors in electronic circuits. For example, the first and second response signals may be used to detect communication problems between the signal input device 203 and the signal conditioning circuit 202.

Fig. 4 illustrates a Coriolis flow meter 400 according to another embodiment of the invention. The common components of Fig. 2 have the same reference numerals. The flow meter 400 includes a first travel sensor 201a, a second travel sensor 201b and a signal conditioning circuit 202. In this embodiment, the signal input device 203 includes a digital-to-analog (D / A) converter 408, a generator

406 signal and transformer 407. D / A converter 408 is connected to signal conditioning circuit 202 and to reference signal generator 406. The reference signal generator 406 is further connected to a transformer 407.

The D / A 408 converter receives a digital frequency command from the signal conditioning circuit 202.

408 converts the digital command to a frequency input signal introduced into the reference signal generator 406, the frequency input signal specifying the frequency of the (one) reference signal to be generated. The reference signal generator 406 generates a reference signal and sends this reference signal to the primary windings 410 of transformer 407.

Transformer 407 creates first and second reference signals using the separated secondary transformer windings, with the secondary windings 411 of the transformer 407 being essentially a pair of identical secondary windings. In this way, the reference signal from the primary windings 410 of the transformer 407 is converted into first and second reference signals on the secondary windings 411. Transformer 407 is preferably suitably constructed to ensure phase matching as a function of temperature between the first and second secondary windings 411. Both secondary windings 411 are connected to the wiring 205 and to the first travel sensors 201a and the second 201b, with the first and second reference signals being input to the travel sensors. As before, the signal conditioning circuit 202 receives the first and second response signals, which arise from the introduction of the first and second reference signals. In one embodiment, the ratio of the primary windings to the first and second secondary windings is substantially 7: 1: 1. As a result, in this embodiment, the primary windings may contain 140 turns, while the first and second secondary windings may contain 20 turns. It should be noted that other winding ratios can be used if desired. In one embodiment, the windings are made of wire # 36 AWG.

In one embodiment, the transformer 407 is an iron core transformer 407. The iron core may contain iron, ferrite material or any iron alloy or iron compound. In one embodiment, the transformer comprises an iron core with a diameter of 7 millimeters. However, it should be noted that any transformer configuration can be used, and all transformer configurations and constructions will fall within the scope of the description and claims.

In one embodiment, the primary windings are made so that they have an inductance of about 25 milliHenra (mH), while the first and second secondary windings are made so that they have an inductance of about 500 microHenra (μΗ). A relatively low inductance can be selected if the flow meter 5 is intended for "intrinsically safe" use of the flow meter. The transformer 407 may further be designed to have an insulation breakdown voltage of about 50 volts RMS (effective value) between the secondary windings and about 100 volts RMS (effective value) between the primary winding and the secondary windings.

Fig. 5 shows an algorithm 500 for a method of determining the signal difference according to another embodiment of the invention. At step 501, the signal input device 203 generates first and second reference signals as previously described.

At step 502, the first and second reference signals are input to the wiring 205 and the first and second pickoff sensors 201a and 201b as previously shown.

At step 503, the first and second reference signals and the first and second response signals are detected by the signal conditioning circuit 202. It should be noted that the first and second reference signals are simultaneously input to the shift sensors 105 and 105 'and are sent to the signal conditioning circuit 202.

At step 504, the signal conditioning circuit 202 removes the first and second reference signals. The first and second reference signals are not needed for signal conditioning circuit 202, and are only needed to generate the first and second response signals. Signal conditioning circuit 202 may filter the first and second reference signals. Signal conditioning circuit 202 may use any type of filter or filters to remove first and second reference signals. In one embodiment, the signal conditioning circuit 202 uses digital filtering to remove first and second reference signals. In one embodiment, the signal conditioning circuit 202 may include a specialized signal processor for such digital filtering, for example a Digital Signal Processor (DSP).

At step 505, the signal difference is determined between the first and second response signals, as described above.

At step 506, compensation is performed, including phase compensation, as outlined above.

The Coriolis flow meter and method of the invention can be used according to any of the embodiments to provide a number of advantages if desired. The invention relates to a flow meter that performs automatic and autonomous zeroing of the sensor system. The invention can autonomously reset the influence of various cabling characteristics and travel sensors. The invention can zero the flow meter influence on different types of cabling and sensors, cabling length, temperature influence on cabling and sensors, manufacturing defects in the cabling and sensor characteristics of each conduct flowmeter detection. The invention required as a result of changes including compensation etc. The invention can detect a separate meter and can and compensation for a given can perform environmental, phase compensation and time-varying compensation.

The invention can perform advanced system diagnostics. The invention may use a known reference signal introduced into the travel sensors to perform automatic gain control, to detect open and short conditions in the travel sensors and in the cabling, to detect electronic errors and to detect faulty cabling by the user or during installation.

The invention can reduce the total cost of the flowmeter system. The invention eliminates the need for expensive cabling with precisely defined tolerances. The invention eliminates the need for precise passive components in the signal conditioning circuit. The invention can reduce the cost of the flowmeter by enabling the use of less expensive components with greater tolerance.