High-precision electromagnetic flowmeter with high stability

Abstract

The utility model provides a high-precision electromagnetic flowmeter with high stability, which comprises a fluid passage structure, the fluid passage structure is connected to an external pipeline and is used for fluid to pass through, and the fluid passage structure comprises an inner pipeline; the sensor is used for measuring the flow of fluid passing through the inner pipeline, the sensor comprises a magnet exciting coil and an electrode, and the magnet exciting coil and the electrode are both fixed to the inner pipeline; the converter is electrically connected with the sensor and used for processing the input current and the input current of the sensor, the converter comprises a power supply module, an excitation module, a signal processing module and a control module, and the excitation module outputs three-direct-wave excitation current; according to the electromagnetic flowmeter, zero point dynamic compensation can be carried out, signal drift is reduced, and the signal stability degree and the measurement precision of the electromagnetic flowmeter are improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to flowmeter field especially relates to high-precision electromagnetic flowmeter with high stability. BACKGROUND

[0002] With the continuous improvement of industrial automation level, in the industrial production process, the flow of fluid in the pipeline needs to be accurately measured and controlled, and at the same time, in order to further do a good job in energy saving, emission reduction, consumption reduction and environmental protection, the importance of flow measurement is increasingly prominent.

[0003] The electromagnetic flowmeter applies a magnetic field to the measured fluid through the excitation coil, and the measured fluid moves in the magnetic field to induce an induced electromotive force. The flow rate of the fluid can be obtained by detecting and processing the electromotive force signal, thereby realizing flow measurement.

[0004] Because the sensor signal is very weak, the electrode receiving and transmitting the signal may be polarized in the solution, and the electromagnetic flowmeter is more susceptible to environmental noise, so the electromagnetic flowmeter on the current market often has flow drift and unstable measurement. INVENTION CONTENTS

[0005] Therefore, it is necessary to provide a high-precision electromagnetic flowmeter with high stability.

[0006] The utility model provides a high-precision electromagnetic flowmeter with high stability, which comprises

[0007] A fluid passage structure is connected to an external pipeline for fluid to pass through, and comprises an inner pipeline.

[0008] A sensor is used to measure the flow of fluid passing through the inner pipeline, and comprises an excitation coil and an electrode, both of which are fixed on the inner pipeline.

[0009] A converter is electrically connected to the sensor, and is used to process the output signal of the sensor and inject excitation current into the sensor. The converter comprises a power supply module, an excitation module, a signal processing module and a control module, and the excitation module outputs three straight wave excitation currents.

[0010] Preferably, the sensor further comprises a shell with a wall thickness of less than or equal to 1.5 mm, which is made of high-impedance stainless steel material, and the coil is located between the shell and the inner pipeline.

[0011] As preferred, the excitation coil has two, the two excitation coils are symmetrically arranged, the excitation coil is wound according to the cosine law, the first end of the excitation coil is close to the electrode, and the second end of the excitation coil is away from the electrode, and the first end is wound more tightly than the second end.

[0012] As preferred, the electrode includes two detection electrodes and a ground electrode, the two detection electrodes and the ground electrode are located on the same circumference of the inner pipeline, the two detection electrodes are symmetrically arranged with the central axis of the inner pipeline as the symmetric axis, the ground electrode is arranged at 90° with the detection electrode, and is located at the lower part of the inner pipeline.

[0013] As preferred, the control module includes a timer, so that the excitation module outputs mutually symmetrical PWM waves, so that the excitation module outputs stable excitation current.

[0014] As preferred, the excitation module outputs three straight wave low frequency excitation currents, and the frequency of the excitation current includes multiple, which are 1 / 16 power frequency, 1 / 20 power frequency and 1 / 25 power frequency, and the multiple frequencies can be switched.

[0015] As preferred, the signal processing module includes an instrument amplifier, a low-pass filter and a differential amplifier, a double-channel analog switch is arranged between the instrument amplifier and the low-pass filter, and the double-channel analog switch can reduce the interference on the signal when the excitation current commutates.

[0016] As preferred, the power module is a low electromagnetic interference switching power supply.

[0017] As preferred, the electromagnetic flowmeter further comprises a display module, the control module comprises an analog-digital converter, the analog-digital converter continuously samples, and then calculates the flow rate and flow through Kalman filtering and displays on the display module.

[0018] As preferred, the electromagnetic flowmeter further comprises

[0019] The empty pipe detection module is used for detecting whether flow passes through the pipeline.

[0020] The excitation detection module is used for detecting whether the excitation module works normally, and correcting the measurement deviation caused by excitation correction.

[0021] The wireless transmission module is used for receiving and transmitting signals.

[0022] The utility model compared with prior art has the advantages of:

[0023] 1. The electromagnetic flowmeter of the utility model adopts low-frequency three straight wave excitation mode, can carry out zero point dynamic compensation, reduces signal drift, improves signal stability degree and measurement precision of the electromagnetic flowmeter;

[0024] 2. The electrode and excitation coil of the sensor are geometrically symmetrical in the installation structure, the coil ensures uniform distribution of the magnetic field and potential balance, the magnetic field induction intensity is large, the magnetic resistance loss is small, and the three-electrode structure effectively offsets external interference;

[0025] 3. The winding form of the magnetic circuit system adopts sectional winding, the excitation coil is wound according to the cosine law, the coil near the electrode is close, the coil away from the electrode is sparse, and the uniformity of the magnetic field is ensured;

[0026] 4. The signal acquisition and processing is composed of four parts of an instrument amplifier, a signal input controller, a low-pass filter and a differential amplifier, and the signal-to-noise ratio is effectively improved;

[0027] 5. The signal passes through the analog switch and enters the double-path analog switch, and the low-pass filter circuit of the utility model can effectively suppress high-frequency noise. BRIEF DESCRIPTION OF DRAWINGS

[0028] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description of preferred embodiments of the present application, taken in conjunction with the accompanying drawings. In the drawings, like reference numerals refer to like elements throughout. The drawings have not been drawn to scale, emphasis instead being placed upon illustrating the principles of the present application. The drawings are as follows:

[0029] Figure 1 It is a structural schematic view of the electromagnetic flowmeter of the utility model;

[0030] Figure 2 It is a structural schematic view of the electromagnetic flowmeter of the utility model;

[0031] Figure 3 It is a structural block diagram of the electromagnetic flowmeter of the utility model;

[0032] Figure 4 It is a circuit diagram of the power module of the utility model;

[0033] Figure 5 It is a circuit diagram of the excitation module of the utility model;

[0034] Figures 6(1)-6(3) It is a circuit diagram corresponding to the signal processing module of the utility model.

[0035] In the drawing, 1 is an inner pipeline, 2 is a sensor, 3 is an excitation coil, 4 is an electrode, 5 is a detection electrode, 6 is a grounding electrode, 7 is a connecting seat, 8 is an outer shell, and 9 is a flange. DETAILED DESCRIPTION

[0036] For the convenience of understanding the utility model, the utility model will be described more fully below with reference to the relevant drawings.

[0037] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element and integrated as a whole, or a middle element can exist at the same time. The terms "mount", "one end", "the other end" and similar expressions used herein are only for illustrative purposes.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the utility model belongs. The terms used in the specification are only for the purpose of describing specific embodiments and are not intended to limit the utility model. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0039] Reference Figure 1 -6, the embodiment of the utility model provides a high-precision electromagnetic flowmeter with high stability, including fluid passage structure, sensor 2 and converter. Fluid passage structure is connected on external pipeline, is used for supplying fluid to pass, fluid passage structure includes inner pipe 1, and inner pipe 1 and external pipeline are fixedly connected by flange 9. Reference Figure 2 , sensor 2 is used to measure the flow of fluid through inner pipe 1, and sensor 2 includes excitation coil 3 and electrode 4, and excitation coil 3 and electrode 4 are fixed on inner pipe 1. Converter is electrically connected with sensor 2, and converter is used to process the output signal of sensor 2 and inject excitation current to sensor 2, in one embodiment, converter and sensor 2 are fixedly connected through connecting seat 7, and in another embodiment, sensor 2 and converter are only connected through soft cable, and in this embodiment, converter can be fixed at a position away from sensor 2. Reference Figure 3 , converter includes power module, excitation module, signal processing module and control module, and excitation module outputs three straight wave excitation current. Electromagnetic flowmeter adopts low-frequency three straight wave excitation mode, can carry out zero point dynamic compensation, reduces signal drift, improves the signal stability degree and measurement precision of electromagnetic flowmeter.

[0040] Reference Figure 2 In a preferred embodiment, sensor 2 further includes shell 8, the wall thickness of shell 8 is less than or equal to 1.5 mm, shell 8 is made of high-impedance stainless steel material, and the coil is located between shell 8 and inner pipe 1. The liner of sensor 2 adopts polytetrafluoroethylene, which has the characteristics of corrosion resistance, wear resistance and high temperature resistance.

[0041] Reference Figure 2In the preferred embodiment, the excitation coil 3 has two, two excitation coil 3 symmetrical arrangement, it should be noted that the "up and down" refers to the position in the use state. Excitation coil 3 according to the cosine law winding, the excitation coil 3 close to the electrode 4 one end of the first end, away from the electrode 4 one end of the second end, in the utility model, the first end of the excitation coil 3 than the second end winding more closely, ensure uniform magnetic field.

[0042] Reference Figure 2 In the preferred embodiment, the electrode 4 includes two detection electrodes 5 and a ground electrode 6, two detection electrodes 5 and ground electrode 6 are located on the same circumference of the inner pipeline 1 (the center point is on the same circumference), and the two detection electrodes 5 are symmetrically arranged with the central axis of the inner pipeline 1 as the axis of symmetry, it should be noted that the "left and right" refers to the position in the use state. The ground electrode 6 and the detection electrode 5 are arranged at 90° and located in the lower part of the inner pipeline 1. In this way, the external grounding ring can be eliminated, the entire measurement average speed process is limited within the balance electrode 4 plane, and the electrical noise interference is completely eliminated.

[0043] Reference Figure 4 - Figure 6, in the preferred embodiment, the control module includes a timer, so that the excitation module outputs mutually symmetrical PWM wave, so that the excitation module output stable excitation current. Excitation control uses the timer of MCU, so that two pins output mutually symmetrical PWM wave, directly drive chip DRV8870, so as to output stable excitation current. Pulse output is calculated according to the cumulative flow of pulse number per 100ms, output by high precision timer in the form of PWM; Current output function according to the instantaneous flow corresponding to 4-20mA current output according to the proportion.

[0044] In the preferred embodiment, the excitation module outputs three straight wave low frequency excitation current, the frequency of excitation current includes a variety, respectively 1 / 16 power frequency, 1 / 20 power frequency and 1 / 25 power frequency, a variety of frequency can be switched. The electromagnetic flowmeter generates excitation current which can be divided by power frequency (50hz), and the excitation current can be adjusted according to the pipe diameter. The excitation mode is three straight wave low frequency excitation, which can dynamically compensate the zero point and improve the measurement accuracy.

[0045] In the preferred embodiment, the signal processing module comprises an instrument amplifier, a low-pass filter and a differential amplifier. A two-way analog switch is arranged between the instrument amplifier and the low-pass filter, which can reduce the interference on the signal when the excitation current commutates. The utility model discloses a signal processing through instrument amplifier, low-pass filter, differential amplifier, common-mode rejection ratio reaches 86.5db, utilizes 24 bit ADC chip to carry out sampling, and the sampling rate is more than 1kHz Multistage digital filter, effectively eliminates power frequency interference and slurry noise. Specifically, the signal is first amplified by the instrument amplifier AD620, and the amplification factor is equal to 49.4K / Rg+1, which can be adjusted by changing Rg. After the signal is amplified by the instrument amplifier, the on-off is controlled by the two-way analog switch, and the interference on the signal when the excitation current commutates is reduced. After the signal passes through the analog switch, it enters the two-way analog switch, and the low-pass filter circuit can effectively suppress high-frequency noise. After low-pass filtering, the signal passes through the last differential amplification circuit, removes the common-mode interference, and enters the high-speed ADC input port after amplification. The ADC continuously samples, and the sampling frequency is greater than 1kHz, and then the MCU carries out digital filtering processing to the sampling, obtains the effective signal data of the forward and reverse and the non-excitation, and calculates the flow rate and flow by Kalman filtering. The combination of digital filtering and Kalman filtering ensures the stability of the signal output.

[0046] In a further preferred embodiment, the electromagnetic flowmeter further comprises a display module, and the control module comprises an analog-to-digital converter. The analog-to-digital converter continuously samples, and then calculates the flow rate and flow by Kalman filtering, and displays on the display module. The display module adopts a tree menu to facilitate user understanding and operation, and leaves a signal monitoring and debugging interface for manufacturer personnel.

[0047] In the preferred embodiment, the power module is a low electromagnetic interference switching power supply. The power supply can be 220V AC power supply or 24V DC power supply, and the power supply is designed as a low electromagnetic interference switching power supply with low ripple and low noise.

[0048] In the preferred embodiment, the electromagnetic flowmeter further comprises a pipe empty detection module and an excitation detection module, which are used to detect whether there is flow in the pipeline; to detect whether the excitation module is working normally, and to correct the measurement deviation caused by excitation correction; to facilitate troubleshooting during use. Without increasing the electrode 4 and without affecting the flow signal, the utility model detects the empty pipe according to the principle that the resistance between the two electrodes 4 is different when there is liquid and no liquid in the pipeline.

[0049] In the preferred embodiment, the flow meter further comprises a wireless transmission module for receiving and transmitting signals.

[0050] The converter part of the utility model realizes modularized processing and production, the coil is arranged between the inner pipeline 1 and the shell 8, the structure is symmetrical, the sealing performance is good, and the magnetic resistance loss is small.

[0051] The electromagnetic flow meter adopts a low-frequency three straight wave excitation mode, can perform zero dynamic compensation, reduces signal drift, and improves the signal stability degree and measurement precision of the electromagnetic flow meter.

[0052] The sensor 2, the electrode 4 and the excitation coil 3 are geometrically symmetrical in the mounting structure, the coil ensures uniform distribution of the magnetic field and balance of the electric potential, the magnetic field induction intensity is large, the magnetic resistance loss is small, and the three-electrode 4 structure effectively offsets external interference.

[0053] The winding form of the magnetic circuit system adopts a segmented winding type, the excitation coil 3 is wound according to the cosine law, the coil close to the electrode 4 is dense, the coil away from the electrode 4 is sparse, and the uniformity of the magnetic field is ensured.

[0054] The signal acquisition and processing are composed of four parts of an instrument amplifier, a signal input controller, a low-pass filter and a differential amplifier, and the signal-to-noise ratio is effectively improved.

[0055] The signal enters the double-path analog switch after passing through the analog switch, and the low-pass filter circuit of the utility model can effectively suppress high-frequency noise.

[0056] The technical features of the above embodiments can be combined arbitrarily, and in order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0057] The above examples only express the specific implementation manners of the utility model, and the description is relatively specific and detailed, but it cannot be understood as the limitation of the utility model patent scope. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the utility model, a number of modifications and improvements can be made, which belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent should be subject to the appended claims.

Claims

1. A high-precision electromagnetic flowmeter with high stability, characterized in that, include A fluid passage structure, which is connected to an external pipeline for the passage of fluid, includes an inner pipe (1); Sensor (2) is used to measure the flow rate of fluid through the inner pipe (1). The sensor (2) includes an excitation coil (3) and an electrode (4), both of which are fixed on the inner pipe (1). The converter is electrically connected to the sensor (2). The converter is used to process the output signal of the sensor (2) and inject excitation current into the sensor (2). The converter includes a power supply module, an excitation module, a signal processing module and a control module. The excitation module outputs three direct wave excitation currents. There are two excitation coils (3), which are arranged symmetrically above and below each other. The excitation coils (3) are wound according to the cosine law. The end of the excitation coil (3) closer to the electrode (4) is the first end, and the end farther away from the electrode (4) is the second end. The first end is wound more tightly than the second end. The excitation module outputs three direct-wave low-frequency excitation currents, and the frequencies of the excitation currents include multiple types, namely 1 / 16 power frequency, 1 / 20 power frequency and 1 / 25 power frequency, and the multiple frequencies can be switched between each other.

2. The high-precision electromagnetic flowmeter with high stability as described in claim 1, characterized in that, The sensor (2) also includes a housing (8) with a wall thickness of less than or equal to 1.5 mm. The housing (8) is made of high-resistivity stainless steel. The coil is located between the housing (8) and the inner pipe (1).

3. The high-precision electromagnetic flowmeter with high stability as described in claim 2, characterized in that, The electrode (4) includes two detection electrodes (5) and a grounding electrode (6). The two detection electrodes (5) and the grounding electrode (6) are located on the same circumference of the inner pipe (1), and the two detection electrodes (5) are arranged symmetrically about the central axis of the inner pipe (1). The grounding electrode (6) is arranged at 90° to the detection electrodes (5) and is located at the lower part of the inner pipe (1).

4. The high-precision electromagnetic flowmeter with high stability as described in claim 1, characterized in that, The control module includes a timer, which causes the excitation module to output symmetrical PWM waves, thereby enabling the excitation module to output a stable excitation current.

5. A high-precision electromagnetic flowmeter with high stability as described in claim 1, characterized in that, The signal processing module includes an instrumentation amplifier, a low-pass filter, and a differential amplifier. A dual-channel analog switch is provided between the instrumentation amplifier and the low-pass filter to reduce interference to the signal during excitation current commutation.

6. The high-precision electromagnetic flowmeter with high stability as described in claim 1, characterized in that, The power module is a low electromagnetic interference switching power supply.

7. A high-precision electromagnetic flowmeter with high stability as described in claim 1, characterized in that, The electromagnetic flowmeter also includes a display module. The control module includes an analog-to-digital converter. The analog-to-digital converter continuously samples the data and then calculates the flow velocity and flow rate through Kalman filtering, which are then displayed on the display module.

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