Vortex flowmeter and method for testing a vortex flowmeter

Abstract

The invention relates to a vortex flowmeter (1) comprising: - a measuring tube (10); - a flow obstruction (20) arranged in the measuring tube; - a sensor device (30), wherein the sensor device has a paddle (31), a sensor body (32) and a piezoelectric element (33); and - an electronic operating circuit (40), wherein the electronic operating circuit has a measuring circuit (50) comprising an operational amplifier (51) and a first capacitor (52.1), wherein the first capacitor (52.1) forms a feedback between an output and a measuring input, wherein a reference input (51.2) can be supplied with a first reference voltage (RS1), wherein the measuring circuit has a first switch (53.1), wherein the electronic operating circuit (40) is designed to connect the piezoelectric element to the measuring input of the operational amplifier via the first switch (53.1) by means of a first switch position (53.11) and to charge the piezoelectric element with a first charging voltage by means of a second switch position (53.12), and wherein the electronic operating circuit derives information about the state of the piezoelectric element from a discharge process of the piezoelectric element.

Description

Technical Field

[0001] This invention relates to a vortex flow meter for measuring the flow rate of a medium flowing through a pipeline, and a method for testing the vortex flow meter. Background Technology

[0002] Eddy current flow measurement devices, such as those shown in DE102009001525A1, have a measuring tube in which a flow-resisting fluid is arranged to generate flow eddies and blades for detecting these flow eddies. In this case, the blades are deflected by the flow eddies, causing deformation of the body, which is typically detected by means of a piezoelectric element. The measurement quality in this case depends on the connection and / or condition of the piezoelectric element. Summary of the Invention

[0003] The purpose of this invention is to provide a simple, robust, and verifiable eddy flow meter with device status, and a method for testing the eddy flow meter.

[0004] This objective is achieved through a vortex flowmeter and a method for testing the vortex flowmeter.

[0005] The eddy current flowmeter according to the present invention for measuring the flow rate of a medium flowing through a pipeline comprises:

[0006] A measuring tube for guiding a medium, having a measuring tube wall and a measuring tube cavity formed by the measuring tube wall, the measuring tube wall having an opening;

[0007] A flow barrier is arranged in the measuring tube;

[0008] Sensor devices designed to detect flow eddies caused by resistant fluids;

[0009] The sensor device includes a blade, a sensor body, and a piezoelectric element.

[0010] The sensor body is arranged in the opening and is tightly sealed to the medium in the measuring tube wall;

[0011] The blade extends into the inner cavity of the measuring tube and is designed to deflect from a static position free from force by a flow vortex.

[0012] The piezoelectric element is arranged on the rear side of the sensor body away from the measuring tube and is designed to detect the deformation of the sensor body caused by the deflection of the blade and convert the deformation into an electrical measurement signal.

[0013] The electronic operating circuit is designed to detect and evaluate measurement signals and provide flow measurement values ​​using evaluation circuitry.

[0014] The electronic operating circuit includes a measurement circuit, which comprises an operational amplifier having an inverting input, a non-inverting input, and an output, as well as a first capacitor.

[0015] The first capacitor forms feedback between the output and the inverting or non-inverting input, wherein the corresponding input is a measurement input;

[0016] The corresponding other input is a reference input and can be supplied with a first reference voltage, and the output is connected to the evaluation circuit of the electronic operation circuit.

[0017] The piezoelectric element can be supplied with a second reference voltage on the side away from the operational amplifier;

[0018] The measuring circuit includes a first switch;

[0019] The electronic operating circuit is designed to connect the piezoelectric element to the measurement input of the operational amplifier via a first switch position and to charge the piezoelectric element with a first charging voltage via a second switch position.

[0020] The electronic operating circuit is designed to derive information related to the state of the piezoelectric element and / or the electrical connection between the piezoelectric element and the electronic operating circuit, and / or the mechanical connection to the sensor body from the discharge process of the piezoelectric element by means of an evaluation circuit.

[0021] Therefore, by means of the first switch, information about the state can be obtained in a particularly simple way by discharging the piezoelectric element after charging with the first charging voltage, either from the discharge process or from the output discharge measurement signal via the output of the operational amplifier during the discharge process.

[0022] During the discharge of the piezoelectric element, the input signal at the measurement input consists of the discharge voltage and a high-frequency voltage oscillation, which is caused by switching to the first switch position. The characteristics of the discharge voltage carry information about the capacitance of the piezoelectric element, and the oscillation carries information about the state of the piezoelectric element and / or the electrical connection of the piezoelectric element to the electronic operating circuit and / or the mechanical connection to the sensor body.

[0023] The discharge of the piezoelectric element occurs via the measurement input of the operational amplifier, or, if present, via a resistor connected in parallel with the first capacitor.

[0024] In one embodiment, the measuring circuit has a second capacitor and a second switch;

[0025] The second capacitor can be supplied with a second reference voltage;

[0026] The electronic operating circuit is designed to connect the second capacitor to the measurement input of the operational amplifier via the second switch by means of the first switch position, and to charge the second capacitor with the second charging voltage by means of the second switch position.

[0027] Wherein, the first charging voltage and the second reference voltage define the first differential voltage, and wherein, the second charging voltage and the second reference voltage define the second differential voltage;

[0028] The second differential voltage has the opposite polarity to the first differential voltage.

[0029] The second capacitor and the piezoelectric element can be connected in parallel via a switch.

[0030] This reduces the influence of discharge voltage on the input signal, enabling high-frequency oscillations to be read out with high voltage resolution.

[0031] In one embodiment, the electronic operating circuit is designed to charge the piezoelectric element with a first charge relative to a second reference voltage and to charge the second capacitor with a second charge.

[0032] Among them, the amount of the first charge and the amount of the second charge deviate from the average charge by less than 10%, and in particular less than 5%.

[0033] This allows for a sufficiently high voltage resolution.

[0034] In one embodiment, the operational amplifier has an input voltage range with a first limit value and a second limit value, and an average value, wherein the first reference voltage deviates from the average value by, for example, less than 10%, and particularly less than 5%, preferably less than 3%.

[0035] In this way, the input signal at the measurement input can be mapped to the output with substantially no distortion and with sufficiently high amplification.

[0036] In one embodiment, the piezoelectric element has a maximum capacitance, wherein the second capacitor has a nominal capacitance;

[0037] The nominal capacitance is at least as large as the maximum capacitance, and for example, at least 5% larger than the first maximum capacitance, particularly at least 10% larger, and preferably at least 20% larger.

[0038] For example, the thickness of a disc-shaped piezoelectric element depends on temperature because the materials used to manufacture piezoelectric elements also have a non-zero coefficient of thermal expansion. For instance, a piezoelectric element may experience an increase in capacitance as the temperature rises. The operating temperature limit, dielectric temperature limit, or process temperature limit thus defines the capacitance range or maximum capacitance of the piezoelectric element.

[0039] Using a second capacitor with a nominal capacitance of at least the maximum capacitance ensures that the second capacitor can be charged with a second charge, the magnitude of which is at least equal to the first charge.

[0040] Therefore, capacitance drift in piezoelectric elements, for example, due to temperature changes, does not cause problems.

[0041] In the method according to the invention for testing the piezoelectric element of the eddy current flowmeter according to the invention, in a first method step, a first switch is switched from a first switch position to a second switch position in order to charge the piezoelectric element;

[0042] In the second method step, after charging the piezoelectric element, the first switch is switched to the first switch position to discharge the piezoelectric element.

[0043] The electronic operating circuit uses an operational amplifier to detect the discharge process and derives information about the state of the piezoelectric element and / or the electrical connection of the piezoelectric element from the measurement signal generated by the discharge process.

[0044] In one embodiment, in the first method step, the second switch is switched from the first switch position to the second switch position in order to charge the second capacitor.

[0045] In the second method step, the second switch and the first switch are simultaneously switched to the first switch position in order to discharge the second capacitor.

[0046] This reduces the influence of discharge voltage on the input signal, enabling high-frequency oscillations to be read out with high voltage resolution. Attached Figure Description

[0047] The invention will now be described with reference to exemplary embodiments.

[0048] Figure 1 An exemplary eddy current flow meter is described;

[0049] Figure 2 An exemplary measurement circuit according to the present invention is described in summary;

[0050] Figure 3 An exemplary method according to the present invention is outlined. Detailed Implementation

[0051] Figure 1 A schematic longitudinal section of an exemplary eddy flow meter 1 is outlined, which is mounted in a pipeline R by means of a measuring tube 10. The measuring tube 10 has a measuring tube wall 11 forming a measuring tube cavity 12 and an opening 13 for receiving a sensor body 32 of a sensor device 30, wherein the sensor body tightly seals the opening 13 in a medium-tight manner.

[0052] Arranged in the measuring tube is a choke fluid 20, which generates eddies in the flowing medium and thus local pressure fluctuations, which are detected by the blades 31 of the sensor device arranged downstream. This causes the blades to deflect from a static, unforced position, thereby deforming the sensor body. A piezoelectric element 33 is arranged on the rear side 32.1 of the sensor body and is designed to convert the deformation of the sensor body into a measurement signal in the form of voltage characteristics. The measuring circuit 50 of the electronic operating circuit 40 is designed to tap the voltage via an electrical connection 34. Here, the piezoelectric element can be substantially formed as a disc with two opposing sides, each side having a conductive coating for tapping the voltage generated by the deformation. The evaluation circuit 60 of the electronic operating circuit is designed to evaluate the voltage or voltage characteristics.

[0053] Figure 2 An exemplary embodiment of the invention is described for the electronic operating circuit 40 of an eddy current flowmeter, including the measurement circuit 50 and the piezoelectric element 33 connected thereto. The measurement circuit has an operational amplifier 51 having a non-inverting input 51.1, an inverting input 51.2, and an output 51.3. A first capacitor 52.1 connects the measurement input (here, the inverting input) to the output of the operational amplifier, wherein the piezoelectric element 33 can be connected to the measurement input (here, the inverting input). The piezoelectric element is designed to convert deformation of the sensor body into a measurement signal.

[0054] The operational amplifier provides a reference voltage RS1 via a reference input (here, a non-inverting input), which is preferably within the middle voltage range of the operational amplifier's input voltage range. In this way, the oscillation of the voltage supplying the measurement input can be mapped onto the output 51.3, which has at most low distortion and sufficient amplification because the oscillation therefore does not reach the modulation range of the operational amplifier. In one embodiment, the operational amplifier has an input voltage range with a first limit value and a second limit value, as well as an average value, wherein the deviation of the first reference voltage from the average value is, for example, less than 30%, particularly less than 20%, and preferably less than 10%.

[0055] According to the invention, a first switch 53.1 having a first switch position 53.11 and a second switch position 53.12 is arranged between a piezoelectric element and a measurement input, wherein the piezoelectric element is connected to the measurement input in the first switch position. To test the state of the piezoelectric element and / or the electrical connection of the piezoelectric element to the electronic operating circuit and / or the mechanical connection to the sensor body, the piezoelectric element can be charged with a first charging voltage LS1 by means of the first switch in the second switch position. When switched back to the first switch position, the measurement input of the operational amplifier discharges the piezoelectric element 33 via the measurement input in a specific manner. During the discharge of the piezoelectric element, the input signal of the measurement input consists of a discharge voltage and a high-frequency voltage oscillation caused by switching to the first switch position, wherein the characteristics of the discharge voltage carry information about the capacitance of the piezoelectric element, and wherein the oscillation carries information about the state of the piezoelectric element and / or the electrical connection of the piezoelectric element to the electronic operating circuit and / or the mechanical connection to the sensor body.

[0056] A second reference voltage can be provided to the piezoelectric element on the side away from the operational amplifier, wherein the deviation of the second reference voltage from the first reference voltage is less than 30%, particularly less than 20%, preferably less than 10%, and wherein the second reference voltage can, for example, be equal to the first reference voltage. In this way, the oscillation of the voltage supplying the measurement input can be mapped onto the output 51.3, which has at most low distortion and sufficient amplification because the oscillation therefore does not reach the modulation range of the operational amplifier.

[0057] The resistor element can be connected in parallel with the first capacitor 52.1 (not shown), and is designed to prevent the first capacitor from being fully charged. Here, the resistor element is of high resistance, so that the dynamic characteristics of the input signal to the piezoelectric element are only slightly affected. Those skilled in the art can select such a resistor element without any problem.

[0058] In one embodiment of the invention, the second capacitor 52.2 can be arranged as shown here, and can be connected in parallel to the piezoelectric element via the second switch 53.2. According to the invention, the second capacitor can be supplied with a second reference voltage, wherein the electronic operating circuit 40 is designed to connect the second capacitor to the measurement input of the operational amplifier via the second switch 53.2 at a first switch position 53.21, and to charge it with a second charging voltage LS2 via the second switch position 53.22, wherein the first charging voltage and the second reference voltage define a first differential voltage, and wherein the second charging voltage and the second reference voltage define a second differential voltage, wherein the second differential voltage has the opposite polarity to the first differential voltage. The second capacitor and the piezoelectric element can be connected in parallel via switches 53.1 and 53.2 via corresponding first switch positions 53.11 and 53.21.

[0059] Specifically, the electronic operating circuit 40 is designed to charge the piezoelectric element 33 with a first charge and the second capacitor with a second charge relative to a second reference voltage, wherein the amounts of the first and second charges deviate from the average value of the charges by less than 10%, particularly less than 5%. The electronic operating circuit can determine the charge, for example, by time integration of the charging current. By simultaneously switching the first and second switches in the corresponding first circuit, the piezoelectric element and the second capacitor are connected in parallel, such that the discharge curve of the second capacitor and the discharge curve of the piezoelectric element compensate for each other. In this way, the measurement input of the operational amplifier is essentially provided only by the oscillation of the piezoelectric element, which can therefore be amplified better than without compensation of the discharge curve.

[0060] In one embodiment, the piezoelectric element has a maximum capacitance, wherein the second capacitor has a nominal capacitance, wherein the nominal capacitance is at least as large as the maximum capacitance, and for example at least 5% larger than the first maximum capacitance, particularly at least 10% larger, and preferably at least 20% larger.

[0061] For example, the thickness of a disc-shaped piezoelectric element depends on temperature because the material used to manufacture piezoelectric elements also has a non-zero coefficient of thermal expansion. Typically, the coefficient of thermal expansion is greater than zero, so the piezoelectric element contracts and increases its capacitance as the temperature decreases. Therefore, the minimum operating temperature, medium temperature, or process temperature limits the maximum capacitance of the piezoelectric element.

[0062] Figure 3 The sequence of an exemplary method according to the invention is outlined, wherein in a first method step 101, a first switch 53.1 is switched from a first switch position 53.11 to a second switch position 53.12 to charge the piezoelectric element, wherein after charging the piezoelectric element 33, in a second method step 102, the first switch is switched back to the first switch position to discharge the piezoelectric element, wherein an electronic operating circuit 40 detects the discharge process, and in a third method step 103, information relating to the state of the piezoelectric element 33 and / or the electrical connection 34 of the piezoelectric element is derived from the discharge measurement signal.

[0063] In one embodiment, in the first method step 101, the second switch 53.2 switches from the first switch position 53.21 to the second switch position 53.22 to charge the second capacitor 52.2, wherein in the second method step 102, the second switch 53.2 and the first switch 53.1 are simultaneously switched to their respective first switch positions 53.11 and 53.21 to discharge the second capacitor. By simultaneously switching the first and second switches in the respective first circuits, the piezoelectric element and the second capacitor are connected in parallel, such that the discharge curve of the second capacitor and the discharge curve of the piezoelectric element compensate for each other. In this way, the measurement input of the operational amplifier is essentially provided only by the oscillation of the piezoelectric element, which can therefore be amplified better than without the compensation of the discharge curve.

[0064] List of reference numerals

[0065] 1. Eddy flow meter

[0066] 10 Measuring tubes

[0067] 11. Measuring pipe wall thickness

[0068] 12 Measuring tube inner cavity

[0069] 13 Opening

[0070] 20. Fluid Resistance

[0071] 30 sensor devices

[0072] 31 blades

[0073] 32 Main sensor body

[0074] 32.1 Rear Side

[0075] 33 Piezoelectric elements

[0076] 34 Electrical Connections

[0077] 40 Electronic operating circuit

[0078] 50 Measurement Circuit

[0079] 51 operational amplifier

[0080] 51.1 Inverting Input

[0081] 51.2 Non-inverting input

[0082] 51.3 Output

[0083] 52.1 First capacitor

[0084] 52.2 Second capacitor

[0085] 53.1 First Switch

[0086] 53.11 First switch position

[0087] 53.12 Second switch position

[0088] 53.2 First Switch

[0089] 53.21 First switch position

[0090] 53.22 Second switch position

[0091] 60 Evaluation Circuit

[0092] 80 housing

[0093] 100 methods

[0094] 101 First Method Steps

[0095] 102 Second Method Steps

[0096] 103 Third Method Steps

[0097] MS measurement signal

[0098] LS1 First charging voltage

[0099] LS2 Second Charging Voltage

[0100] RS1 First Reference Voltage

[0101] RS2 Second Reference Voltage

[0102] R pipeline

Claims

1. An eddy current flowmeter (1) for measuring the flow rate of a medium flowing through a pipeline (R), comprising: A measuring tube (10) for guiding the medium, the measuring tube having a measuring tube wall (11) and a measuring tube cavity (12) formed by the measuring tube wall, wherein the measuring tube wall has an opening (13); A flow barrier (20) is arranged in the measuring tube; Sensor device (30), the sensor device being designed to detect flow eddies caused by the resistant fluid; The sensor device includes a blade (31), a sensor body (32), and a piezoelectric element (33); The sensor body is arranged in the opening (13) and is tightly sealed to the medium in the measuring tube wall; The blade (31) extends into the inner cavity of the measuring tube and is designed to deflect from a static position free from force by a flow vortex; The piezoelectric element (33) is arranged on the rear side (32.1) of the sensor body away from the measuring tube, and is designed to detect the deformation of the sensor body caused by the deflection of the blade and convert the deformation into an electrical measurement signal. An electronic operating circuit (40) is designed to detect and evaluate the measurement signal by means of an evaluation circuit (60) and provide a flow measurement value; The electronic operating circuit includes a measurement circuit (50), which comprises an operational amplifier (51) having an inverting input (51.1), a non-inverting input (51.2), and an output (51.3), as well as a first capacitor (52.1). The first capacitor (52.1) forms feedback between the output and the inverting input (51.1) or the non-inverting input (51.2), wherein the corresponding input is a measurement input; The corresponding other input is a reference input and can be supplied with a first reference voltage (RS1), and the output is connected to the evaluation circuit of the electronic operation circuit. The piezoelectric element can be supplied with a second reference voltage (RS2) on the side opposite to the operational amplifier; The measuring circuit is characterized in that it includes a first switch (53.1); The electronic operating circuit (40) is designed to connect the piezoelectric element to the measurement input of the operational amplifier via the first switch (53.1) in a first switch position, and to charge the piezoelectric element with a first charging voltage (LS1) via a second switch position. The electronic operating circuit is designed to derive information related to the state of the piezoelectric element, and / or the electrical connection between the piezoelectric element and the electronic operating circuit, and / or the mechanical connection to the sensor body from the discharge process of the piezoelectric element by means of the evaluation circuit.

2. The eddy current flowmeter according to claim 1, in, The second reference voltage is equal to the first reference voltage.

3. The eddy current flowmeter according to claim 1, in, The measuring circuit (50) has a second capacitor (52.2) and a second switch (53.2); The second capacitor can be supplied with the second reference voltage. The electronic operating circuit (40) is designed to connect the second capacitor to the measurement input of the operational amplifier via the second switch (53.2) by means of a first switch position, and to charge the second capacitor with a second charging voltage (LS2) by means of the second switch position. Wherein, the first charging voltage and the second reference voltage define a first differential voltage, and wherein, the second charging voltage and the second reference voltage define a second differential voltage; The second differential voltage has the opposite polarity to the first differential voltage. The second capacitor and the piezoelectric element can be connected in parallel via the first switch (53.1) and the second switch (53.2) through corresponding first switch positions.

4. The eddy current flowmeter according to claim 3, in, The electronic operating circuit (40) is designed to charge the piezoelectric element (33) with a first charge relative to the second reference voltage and to charge the second capacitor with a second charge. Wherein, the amounts of the first charge and the second charge deviate from the average charge by less than 10%.

5. The eddy current flowmeter according to claim 4, in, The amount of the first charge and the amount of the second charge deviate from the average charge value by less than 5%.

6. The eddy current flowmeter according to any one of claims 3 to 5, in, The operational amplifier has an input voltage range and an average value. The input voltage range has a first limit value and a second limit value, wherein the first reference voltage deviates from the average value by less than 10%.

7. The eddy current flowmeter according to claim 6, in, The first reference voltage deviates from the average value by less than 5%.

8. The eddy current flowmeter according to claim 6, in, The first reference voltage deviates from the average value by less than 3%.

9. The eddy current flowmeter according to any one of claims 3 to 5, in, The piezoelectric element has a maximum capacitance, wherein the second capacitor has a nominal capacitance; The nominal capacitance is at least 5% larger than the first maximum capacitance.

10. The eddy current flowmeter according to claim 9, in, The nominal capacitance is at least 10% larger than the first maximum capacitance.

11. The eddy current flowmeter according to claim 9, in, The nominal capacitance is at least 20% larger than the first maximum capacitance.

12. A method (100) for testing the piezoelectric element (33) of the eddy current flowmeter (1) according to claim 1 or 2, in, In the first method step (101), the first switch (53.1) is switched from the first switch position to the second switch position in order to charge the piezoelectric element; In the second method step (102), after the piezoelectric element (33) is charged, the first switch is switched to the first switch position to discharge the piezoelectric element. The electronic operating circuit (40) detects the discharge process and, in the third method step (103), derives information from the discharge measurement signal relating to the state of the piezoelectric element (33) and / or the electrical connection (34) of the piezoelectric element.

13. A method (100) for testing the piezoelectric element (33) of the eddy current flowmeter (1) according to any one of claims 3 to 11, in, In the first method step (101), the first switch (53.1) is switched from the first switch position to the second switch position in order to charge the piezoelectric element; In the second method step (102), after the piezoelectric element (33) is charged, the first switch is switched to the first switch position to discharge the piezoelectric element. The electronic operating circuit (40) detects the discharge process and, in the third method step (103), derives information from the discharge measurement signal relating to the state of the piezoelectric element (33) and / or the electrical connection (34) of the piezoelectric element.

14. The method according to claim 13, in, In the first method step (101), the second switch (53.2) is switched from the first switch position to the second switch position in order to charge the second capacitor (52.2); In the second method step (102), the second switch (53.2) and the first switch (53.1) are simultaneously switched to the corresponding first switch positions in order to discharge the second capacitor.

Images