An electromagnetic interference immune signal conditioning circuit for industrial flow meters

Abstract

The application relates to an anti-electromagnetic interference signal conditioning circuit for an industrial flowmeter, which comprises a signal output terminal, a power supply positive terminal, a ground terminal and a signal output terminal, the signal output terminal being connected with a rear-end controller of the industrial flowmeter; a power supply input terminal being connected with the industrial flowmeter; a first-stage protection unit being connected in parallel between the power supply positive terminal and the ground terminal; a second-stage protection unit being connected in parallel between the power supply positive terminal and the ground terminal and being located behind the first-stage protection unit; a signal line filtering and isolating unit being arranged between the signal output terminal and the power supply input terminal and being located behind the second-stage protection unit; a power supply line filtering unit being arranged between the signal output terminal and the power supply input terminal; and a third-stage protection unit being connected in parallel between the signal output terminal and the ground terminal and being located behind the signal line filtering and isolating unit. The application can realize wide-spectrum interference coverage through the progressive cooperation of the three-stage protection units and can improve signal precision through independent filtering.

Description

Technical Field

[0001] This application relates to the field of flow meter anti-interference technology, and in particular to an anti-electromagnetic interference signal conditioning circuit for industrial flow meters. Background Technology

[0002] Industrial flow meters, as core equipment for measuring flow parameters in industrial production processes, are widely used in many fields such as petrochemicals, energy and power, and intelligent manufacturing. The accuracy and stability of their measurement data directly affect production process control, energy consumption accounting, and product quality control. In industrial environments, there are numerous sources of electromagnetic interference, including surge voltages generated by the start-up and shutdown of high-power equipment, high-frequency noise radiated by electronic devices such as frequency converters, and transient pulses formed by line coupling. These interferences can intrude into the flow meter through power lines or signal lines, causing flow signal distortion, transmission interruption, or even equipment failure, severely restricting the continuity and reliability of industrial production.

[0003] In existing technologies, electromagnetic interference (EMI) protection measures for industrial flow meters mainly rely on single protection or simple filtering. These include connecting a varistor in parallel at the power input to absorb surge overvoltages, or connecting an RC low-pass filter in series at the signal output to filter out some high-frequency noise. However, these solutions have significant technical limitations: First, the protection spectrum is narrow; a single type of protection device can only cope with interference of specific energy levels and frequency ranges, failing to cover a wide spectrum of interference scenarios ranging from slow high-energy surges to fast low-energy spikes. Second, the filtering effect is insufficient; simple RC filters have a flat filtering slope, limiting their ability to suppress noise in specific frequency bands and easily leading to excessive attenuation of the useful flow signal, affecting measurement accuracy. Third, there is a lack of systematic collaborative design; the various protection and filtering components are often simply stacked together, failing to form a collaborative system with complementary response characteristics and clear protection priorities. This makes it difficult to resist the complex and ever-changing composite interference in industrial environments, leading to problems such as zero-dropping and distortion in the flow meter signal, and failing to meet the requirements for long-term stable operation. It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Utility Model Content

[0004] To address the aforementioned issues, this application provides an electromagnetic interference (EMI) protection signal conditioning circuit for industrial flow meters. This circuit achieves wide-spectrum interference coverage through the progressive synergy of three-level protection units and improves signal accuracy through independent filtering of power lines and signal lines.

[0005] To achieve the objectives of this application, the following technical solution is provided: This application provides an electromagnetic interference protection signal conditioning circuit for industrial flow meters, comprising: The signal output terminal includes a power positive terminal, a ground terminal and a signal output terminal. The signal output terminal is connected to the back-end controller of the industrial flow meter and is used to output the conditioned flow signal to the back-end controller and to provide power. A power input terminal is connected to an industrial flow meter to supply power to the industrial flow meter and to output a flow meter signal. The first-level protection unit is connected in parallel between the positive terminal of the power supply and the ground terminal to absorb and discharge power surge overvoltage; The second-level protection unit is connected in parallel between the positive terminal of the power supply and the ground terminal, and is located after the first-level protection unit. It is used to absorb positive transient pulse interference. A signal line filtering and isolation unit is disposed between the signal output terminal and the power input terminal, after the second-level protection unit, and is used to suppress high-frequency noise in the output signal of the industrial flow meter and isolate the signal path from interference sources. A power line filtering unit is disposed between the signal output terminal and the power input terminal to filter out high-frequency noise that remains on the power line after two levels of protection. The third-level protection unit is connected in parallel between the signal output terminal and the ground terminal, and is located after the signal line filtering and isolation unit. It is used to absorb the voltage spikes remaining on the signal line after filtering.

[0006] In one possible implementation, the signal line filtering and isolation unit includes a first inductor and a first capacitor, wherein the first inductor is connected in series with the signal output terminal of the industrial flow meter, and the first capacitor is connected in parallel between the signal output terminal and the ground terminal.

[0007] In one possible implementation, a variable resistor is also included, connected in parallel between the signal output terminal and the ground terminal, and located after the third-level protection unit.

[0008] In one possible implementation, the resistance of the variable resistor is 250Ω.

[0009] In one possible implementation, the power line filtering unit includes a second inductor and a second capacitor, wherein the second inductor is connected in series with the positive terminal of the power supply, and the second capacitor is connected in parallel between the positive terminal of the power supply and the ground terminal.

[0010] In one possible implementation, the signal line filtering and isolation unit shares the first capacitor with the power line filtering unit, and the first capacitor is also connected in parallel between the positive terminal of the power supply and the ground terminal, and is located before the second capacitor.

[0011] In one possible implementation, the electromagnetic interference protection signal conditioning circuit for industrial flow meters further includes an overcurrent protection unit connected in series with the positive terminal of the power supply and located before the first-stage protection unit for overcurrent protection.

[0012] In one possible implementation, the electromagnetic interference protection signal conditioning circuit for the industrial flow meter further includes a reverse current protection unit connected in series with the positive terminal of the power supply and located before the overcurrent protection unit to prevent reverse current flow.

[0013] In one possible implementation, the power line filtering unit is a π-type filter, and the signal line filtering and isolation unit is a Γ-type filter / or an L-type filter.

[0014] In one possible implementation, the first-stage protection unit is a varistor, and the second-stage and third-stage protection units are both unidirectional TVS diodes.

[0015] The technical solution provided in this application may include the following beneficial effects: The electromagnetic interference (EMI) protection signal conditioning circuit for industrial flow meters provided in this application achieves wide-spectrum interference coverage from high-energy surges and instantaneous pulses to voltage spikes through progressive synergistic protection of three-level protection units, with complementary response characteristics. Furthermore, the independent filtering design of the power line filtering unit and the signal line filtering and isolation unit avoids crosstalk between power line and signal line noise, ensuring the integrity and transmission accuracy of the flow signal, significantly improving the signal-to-noise ratio, and reducing the risk of signal dropping to zero due to interference. At the same time, by using common discrete components and innovative layout, the circuit structure is simplified, and the cost and size are reduced.

[0016] Practical application verification shows that after this circuit was applied to the steam flow meter of the silk-making line, the average number of times the wires dropped per month decreased from 28 to 2, which is a significant effect.

[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0018] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the embodiments of the invention to explain this application and do not constitute a limitation thereof. Obviously, the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0019] Figure 1 This is a schematic diagram of an electromagnetic interference protection signal conditioning circuit for an industrial flow meter, provided as an embodiment of this application.

[0020] Figure label: 100. Power input terminal; 200. Signal output terminal; 300. First-level protection unit; 400. Second-level protection unit; 500. Third-level protection unit; 600. Signal line filtering and isolation unit; 610. First inductor; 620. First capacitor; 700. Power line filtering unit; 710. Second inductor; 720. Second capacitor; 800, Variable resistor; 900, Overcurrent protection unit; 1000, Backflow protection unit; 1100, Flow meter. Detailed Implementation

[0021] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that this disclosure will be more comprehensive and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0022] Furthermore, the accompanying drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted.

[0023] This example implementation first provides an electromagnetic interference protection signal conditioning circuit for industrial flow meters. (Reference) Figure 1 As shown, the electromagnetic interference protection signal conditioning circuit for industrial flow meters includes a signal output terminal 100, a power input terminal 200, a first-level protection unit 300, a second-level protection unit 400, a third-level protection unit 500, a signal line filtering and isolation unit 600, and a power line filtering unit 700.

[0024] The signal output terminal 100 includes a power positive terminal, a ground terminal and a signal output terminal. The signal output terminal is connected to the back-end controller of the industrial flow meter and is used to output the conditioned flow signal to the back-end controller and to provide power. The power input terminal 200 is connected to the industrial flow meter 1100 and is used to supply power to the industrial flow meter 1100 and to output a flow meter signal. The first-level protection unit 300 is connected in parallel between the positive terminal of the power supply and the ground terminal to absorb and discharge power surge overvoltage. The second-level protection unit 400 is connected in parallel between the positive terminal of the power supply and the ground terminal, and is located after the first-level protection unit 300, and is used to absorb positive transient pulse interference. The signal line filtering and isolation unit 600 is disposed between the signal output terminal 100 and the power input terminal 200, after the second-level protection unit 400, and is used to suppress high-frequency noise in the output signal of the industrial flow meter 1100 and isolate the signal path from the interference source. A power line filtering unit 700 is disposed between the signal output terminal 100 and the power input terminal 200 to filter out high-frequency noise that remains on the power line after two levels of protection. The third-level protection unit 500 is connected in parallel between the signal output terminal 200 and the ground terminal, and is located after the signal line filtering and isolation unit 600. It is used to absorb the voltage spikes remaining on the signal line after filtering.

[0025] Optionally, the power line filtering unit 700 is a π-type filter, and the signal line filtering and isolation unit 800 is a Γ-type filter / or an L-type filter.

[0026] It should be noted that the π-type filter used in the power line filtering unit 700 is composed of an inductor and two capacitors, while the Γ-type filter / or L-type filter used in the signal line filtering and isolation unit 600 is composed of an inductor and a single capacitor. The π-type filter achieves a steeper filtering slope by using a series inductor to impede the conduction of high-frequency noise and a parallel capacitor to discharge noise to ground. This results in better suppression of wide-band high-frequency noise in the power line than a single filter structure. The Γ-type or L-type filter has a simpler structure, which reduces the space occupied by components while ensuring effective suppression of high-frequency noise in the signal line. This makes it suitable for the compact installation environment of industrial flow meters and allows for flexible selection based on the actual interference frequency band on site, improving circuit adaptability.

[0027] Optionally, the first-level protection unit 300 is a varistor, and the second-level protection unit 400 and the third-level protection unit 500 are both unidirectional TVS diodes.

[0028] It should be noted that varistors have a large current capacity, which can efficiently absorb the long-lasting and high-energy power surge overvoltages commonly seen in industrial environments, preventing the surge from directly impacting subsequent circuits; unidirectional TVS diodes have a response speed of up to nanoseconds, which can quickly clamp medium-energy positive transient pulses (second stage) and low-energy residual voltage spikes on signal lines (third stage), and the unidirectional conduction characteristic will not affect normal power supply and signal transmission. That is, high-energy surges are discharged first, transient pulses are suppressed, and signal spikes are cleared, covering electromagnetic interference of different energy levels and types.

[0029] In one possible implementation, the signal line filtering and isolation unit 600 includes a first inductor 610 and a first capacitor 620. The first inductor 610 is connected in series with the signal output terminal of the industrial flow meter 1100, and the first capacitor 620 is connected in parallel between the signal output terminal 200 and the ground terminal.

[0030] It should be noted that the first inductor 610 is connected in series at the signal output terminal of the industrial flow meter 1100. It can utilize the inductor's impedance to high-frequency signals to reduce the transmission of high-frequency noise with the flow signal. At the same time, it cuts off the coupling channel between the signal path and the interference source through the electromagnetic isolation effect. The first capacitor 620 is connected in parallel between the signal output terminal 200 and the ground terminal. It can discharge the residual high-frequency noise on the signal line that has penetrated the first inductor 610 to the ground. The two form a "blocking-discharging" synergistic filtering mechanism. While suppressing noise, it can retain the useful low-frequency components in the flow signal to the maximum extent and avoid signal distortion from affecting the measurement accuracy.

[0031] In one possible implementation, the electromagnetic interference protection signal conditioning circuit for the industrial flow meter further includes a variable resistor 800 connected in parallel between the signal output terminal 200 and the ground terminal, and located after the third-level protection unit 500.

[0032] It should be noted that the variable resistor 800 is connected in parallel between the signal output terminal 200 and the ground terminal. It can be used as a signal matching resistor. By adjusting its resistance value, the signal output impedance can be made consistent with the input impedance of the back-end controller, reducing problems such as signal reflection and standing waves caused by impedance mismatch, and further improving the stability of signal transmission. At the same time, its parallel structure can play a certain role in voltage division when the signal fluctuates abnormally, and help protect the signal receiving port of the back-end controller.

[0033] Optionally, the resistance value of the variable resistor 800 is 250Ω.

[0034] In one possible implementation, the power line filtering unit 700 includes a second inductor 710 and a second capacitor 720, wherein the second inductor 710 is connected in series with the positive terminal of the power supply, and the second capacitor 720 is connected in parallel between the positive terminal of the power supply and the ground terminal.

[0035] It should be noted that the second inductor 710 in the power line filtering unit 700 is connected in series with the positive terminal of the power supply, which can prevent the high-frequency noise that remains after the two-stage protection of the first-stage protection unit 300 and the second-stage protection unit 400 from being conducted along the power line; the second capacitor 720 is connected in parallel between the positive terminal of the power supply and the ground terminal, which can discharge the high-frequency noise in the power line to the ground, solve the impact of residual noise in the power line on the power supply stability and signal output accuracy of the industrial flow meter 1100, and ensure the purity of the operating voltage of the core components of the industrial flow meter 1100.

[0036] In one possible implementation, the signal line filtering and isolation unit 600 and the power line filtering unit 700 share the first capacitor 620, which is also connected in parallel between the positive terminal of the power supply and the ground terminal, and is located before the second capacitor 720.

[0037] It should be noted that the first capacitor 620 in the signal line filtering and isolation unit 600 is also shared by the power line filtering unit 700, and the first capacitor 620 is located before the second capacitor 720. This reduces the number of components, simplifies the circuit structure, and reduces cost and size. It also enables a hierarchical filtering logic of "firstly performing preliminary ground filtering on the power line and signal line through the first capacitor 620, and then performing secondary precise filtering on the power line through the second capacitor 720", which avoids crosstalk between power line and signal line noise and improves the overall filtering efficiency.

[0038] In one possible implementation, the electromagnetic interference protection signal conditioning circuit for industrial flow meters further includes an overcurrent protection unit 900, which is connected in series with the positive terminal of the power supply and is located before the first-stage protection unit 300 for overcurrent protection.

[0039] It should be noted that the overcurrent protection unit 900 is connected in series with the positive terminal of the power supply and is located before the first-stage protection unit 300. The overcurrent protection unit 900 can be equipped with a self-resetting fuse. When the circuit experiences abnormal conditions such as short circuit or overload, resulting in excessive current, it can quickly cut off the power supply path to prevent the excessive current from burning out the first-stage protection unit 300, the industrial flow meter 1100, and subsequent conditioning circuits. After the fault is cleared, the path can be automatically restored without the need for manual component replacement, thus improving the durability and maintenance convenience of the circuit.

[0040] In one possible implementation, the electromagnetic interference protection signal conditioning circuit for industrial flow meters further includes a reverse current protection unit 1000, which is connected in series with the positive terminal of the power supply and is located before the overcurrent protection unit 900 to prevent reverse current flow.

[0041] It should be noted that the reverse current protection unit 1000 is a unidirectional TVS diode. Utilizing the unidirectional conductivity of a diode, it can prevent reverse current from flowing into the industrial flow meter 1100 and the conditioning circuit when the positive and negative terminals of the external power supply are reversed or when other modules in the circuit generate reverse current abnormally. This avoids irreversible damage to the sensor, chip and other core components of the industrial flow meter 1100 caused by reverse current, and provides basic power polarity protection for the circuit.

[0042] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0044] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0045] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0046] In the description of this specification, references to terms such as "one possible implementation," "further," "exemplary," "specific example," or "optional," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. The illustrative expressions of the above terms in this specification do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0047] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention filed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not claimed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the appended claims.

Claims

1. An electromagnetic interference protection signal conditioning circuit for industrial flow meters, characterized in that, include: The signal output terminal includes a power positive terminal, a ground terminal and a signal output terminal. The signal output terminal is connected to the back-end controller of the industrial flow meter and is used to output the conditioned flow signal to the back-end controller and to provide power. A power input terminal is connected to an industrial flow meter to supply power to the industrial flow meter and to output a flow meter signal. The first-level protection unit is connected in parallel between the positive terminal of the power supply and the ground terminal to absorb and discharge power surge overvoltage; The second-level protection unit is connected in parallel between the positive terminal of the power supply and the ground terminal, and is located after the first-level protection unit. It is used to absorb positive transient pulse interference. A signal line filtering and isolation unit is disposed between the signal output terminal and the power input terminal, after the second-level protection unit, and is used to suppress high-frequency noise in the output signal of the industrial flow meter and isolate the signal path from interference sources. A power line filtering unit is disposed between the signal output terminal and the power input terminal to filter out high-frequency noise that remains on the power line after two levels of protection. The third-level protection unit is connected in parallel between the signal output terminal and the ground terminal, and is located after the signal line filtering and isolation unit. It is used to absorb the voltage spikes remaining on the signal line after filtering.

2. The electromagnetic interference protection signal conditioning circuit for industrial flow meters according to claim 1, characterized in that, The signal line filtering and isolation unit includes a first inductor and a first capacitor. The first inductor is connected in series with the signal output terminal of the industrial flow meter, and the first capacitor is connected in parallel between the signal output terminal and the ground terminal.

3. The electromagnetic interference protection signal conditioning circuit for industrial flow meters according to claim 2, characterized in that, It also includes a variable resistor, connected in parallel between the signal output terminal and the ground terminal, and located after the third-level protection unit.

4. The electromagnetic interference protection signal conditioning circuit for industrial flow meters according to claim 3, characterized in that, The resistance of the variable resistor is 250Ω.

5. The electromagnetic interference protection signal conditioning circuit for industrial flow meters according to claim 2, characterized in that, The power line filtering unit includes a second inductor and a second capacitor. The second inductor is connected in series with the positive terminal of the power supply, and the second capacitor is connected in parallel between the positive terminal of the power supply and the ground terminal.

6. The electromagnetic interference protection signal conditioning circuit for industrial flow meters according to claim 5, characterized in that, The signal line filtering and isolation unit shares the first capacitor with the power line filtering unit. The first capacitor is also connected in parallel between the positive terminal of the power supply and the ground terminal, and is located before the second capacitor.

7. The electromagnetic interference protection signal conditioning circuit for industrial flow meters according to claim 5, characterized in that, Also includes: An overcurrent protection unit is connected in series with the positive terminal of the power supply and is located before the first-stage protection unit for overcurrent protection.

8. The electromagnetic interference protection signal conditioning circuit for industrial flow meters according to claim 7, characterized in that, Also includes: A reverse current protection unit is connected in series with the positive terminal of the power supply and is located before the overcurrent protection unit to prevent current from flowing in the opposite direction.

9. The electromagnetic interference protection signal conditioning circuit for industrial flow meters according to claim 1, characterized in that, The power line filtering unit is a π-type filter, and the signal line filtering and isolation unit is a Γ-type filter / or an L-type filter.

10. The electromagnetic interference protection signal conditioning circuit for industrial flow meters according to claim 1, characterized in that, The first-level protection unit is a varistor, while the second-level and third-level protection units are both unidirectional TVS diodes.

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