Self-adaptive signal amplifying and filtering circuit of electromagnetic flowmeter

Abstract

The invention belongs to the technical field of circuits, and particularly relates to a self-adaptive signal amplification and filter circuit of an electromagnetic flowmeter, which comprises a signal acquisition module, a photoelectric isolation module, a self-adaptive gain amplification module, a self-adaptive filter module, a signal output module and a stable power supply module for supplying power to each module, the self-adaptive gain amplification module is in bidirectional communication with the self-adaptive filtering module, and the stabilized power supply module is also connected with the self-adaptive gain amplification module. According to the invention, the signal acquisition module, the photoelectric isolation module, the adaptive gain amplification module, the adaptive filtering module and the signal output module are connected in sequence, and the stable power supply module and the collaborative design of bidirectional communication between the adaptive gain amplification module and the adaptive filtering module are matched. The problems that a signal processing link of an existing electromagnetic flowmeter is split, and the measurement adaptability is poor and the stability is insufficient due to the fact that linkage does not exist between modules are effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of circuit technology, and particularly relates to an adaptive signal amplification and filtering circuit for an electromagnetic flowmeter. Background Technology

[0002] Electromagnetic flow meters, as flow measurement devices based on the principle of electromagnetic induction, are widely used in chemical, water treatment, metallurgical, and petroleum industries due to their advantages such as no throttling components, wide measurement range, and strong adaptability. They are used to monitor the flow of conductive media (such as acid and alkali solutions, sewage, and slurry). Their core working principle is as follows: by applying an alternating magnetic field to both sides of the measuring pipe, the conductive medium flowing through the pipe cuts the magnetic lines of force, generating an induced electromotive force. This induced electromotive force is converted into an electrical signal output by the sensor, and after being conditioned by the signal processing circuit, it is finally converted into the corresponding flow rate value.

[0003] However, the complex operating conditions in industrial settings (such as strong electromagnetic interference, power supply voltage fluctuations, and large ranges in medium flow velocity) pose numerous technical challenges to the signal processing of electromagnetic flowmeters. The induced electrical signal output by the sensor exhibits significant characteristics of being "weak" (typically in the millivolt range), "dynamically fluctuating" (the signal amplitude fluctuates significantly with changes in medium flow velocity and concentration; the signal strength can be as low as below 1mV at low flow rates and rise to above 1V at high flow rates), and "susceptible to interference" (easily affected by common industrial interferences such as power frequency interference (50Hz / 60Hz), electromagnetic coupling interference, and ground loop interference). This places stringent requirements on the adaptability, anti-interference capability, and stability of the signal processing circuit.

[0004] The signal processing circuits of existing electromagnetic flowmeters still have the following prominent problems in practical applications: Poor gain adaptability: Most circuits use a fixed-gain amplification design, which cannot dynamically match the signal amplitude changes under different flow rates. At low flow rates, weak signals are easily drowned out by background noise, making it difficult to extract effective signals; at high flow rates, strong signals are prone to exceed the linear operating range of the circuit, causing saturation distortion, ultimately leading to a decrease in measurement accuracy across the entire range.

[0005] Insufficient anti-interference capability: Existing filtering mechanisms mostly use filters with single fixed parameters (such as single high-pass filters or band-stop filters), the filter channels cannot be switched, and the response is lagging. Faced with the complex and ever-changing interference in industrial environments (such as power frequency interference, harmonic interference, electromagnetic pulse interference generated by equipment start-up and shutdown, etc.), it is impossible to achieve targeted and rapid suppression. The interference signal will be directly superimposed on the effective signal, resulting in large fluctuations in the measurement data.

[0006] Inadequate or missing signal isolation design: When high-voltage electrical equipment (such as frequency converters, motors, pumps, etc.) is deployed close to electromagnetic flowmeters in industrial settings, high-voltage interference and ground loop interference can easily intrude into the core processing unit through the signal link. Some existing circuits lack isolation modules or only use simple resistor isolation, which cannot achieve effective electrical isolation, leading to interference contamination of the signal link and affecting measurement stability.

[0007] Poor power supply adaptability: Industrial power supply systems suffer from voltage fluctuations (such as wide fluctuations from 12V to 24V) and voltage spikes. Existing signal processing circuit power supply modules are mostly simple voltage regulation designs, lacking adaptive adjustment capabilities. When the supply voltage exceeds the rated range, it can easily cause the operating parameters of core components (such as operational amplifiers, detectors, analog switches, etc.) to drift, or even break down and be damaged, resulting in circuit instability or shutdown.

[0008] Poor module coordination: The existing circuit's amplification, filtering, and power supply modules are mostly designed independently, lacking a linkage mechanism. For example, when the filtering module detects interference, it cannot feed back to the amplification module for gain adjustment, resulting in the interference signal being amplified synchronously. The power supply module uses a uniform power supply method for all functional modules, without prioritizing the power supply needs of core modules (such as the amplification module), further reducing the overall stability of the circuit performance.

[0009] The aforementioned problems directly result in existing electromagnetic flowmeters exhibiting low measurement accuracy, large data fluctuations, insufficient reliability, and high maintenance costs in complex industrial scenarios, making it difficult to meet the core requirements of industrial production for "high precision, high stability, and wide adaptability" in flow measurement. Therefore, developing a signal processing circuit with adaptive gain adjustment, rapid anti-interference filtering, effective isolation protection, and stable power supply capabilities has become a key technological breakthrough for improving the industrial applicability of electromagnetic flowmeters. Summary of the Invention

[0010] The purpose of this invention is to address the aforementioned technical problems by providing an adaptive signal amplification and filtering circuit for an electromagnetic flowmeter.

[0011] In view of this, the present invention provides an adaptive signal amplification and filtering circuit for an electromagnetic flowmeter, comprising a signal acquisition module, an opto-isolation module, an adaptive gain amplification module, an adaptive filtering module, and a signal output module connected in sequence, and a stable power supply module for supplying power to each module; the adaptive gain amplification module communicates bidirectionally with the adaptive filtering module, and the stable power supply module is also connected to the adaptive gain amplification module.

[0012] Furthermore, the signal acquisition module includes a precision instrumentation amplifier and current-limiting resistors R1 and R2; one end of the current-limiting resistor R1 is connected to the positive differential output terminal (V_s+) of the electromagnetic flowmeter sensor, and the other end is connected to the non-inverting input terminal (IN+) of the precision instrumentation amplifier; one end of the current-limiting resistor R2 is connected to the negative differential output terminal (V_s-) of the electromagnetic flowmeter sensor, and the other end is connected to the inverting input terminal (IN-) of the precision instrumentation amplifier; the power supply input terminal of the precision instrumentation amplifier is connected to the power supply output terminal of the stable power supply module, and the output terminal of the precision instrumentation amplifier is connected to the input terminal of the opto-isolation module, which is used to perform preliminary conditioning on the weak differential signal output by the sensor and then transmit it to the opto-isolation module.

[0013] Furthermore, the opto-isolation module includes an optocoupler U1 and current-limiting resistors R3 and R4; the optocoupler U1 includes a photodiode and a phototransistor coupled to each other, the anode of the photodiode is connected to the output terminal of the signal acquisition module through the current-limiting resistor R3, and the cathode of the photodiode is grounded; the collector of the phototransistor is connected to the power supply output terminal of the stable power supply module through the current-limiting resistor R4, the emitter of the phototransistor is grounded, and the collector of the phototransistor serves as the output terminal of the opto-isolation module, connected to the signal input terminal of the adaptive gain amplifier module.

[0014] Furthermore, the adaptive gain amplification module includes a gain adjustment unit, a signal amplitude detection unit, and a control unit. The gain adjustment unit consists of a transistor Q1, a base coupling resistor R5, a voltage divider network, a controllable voltage divider component, and an accelerating capacitor C1. The base of the transistor Q1 is connected to the output terminal of the opto-isolation module through the base coupling resistor R5. The accelerating capacitor C1 is connected in parallel across the base coupling resistor R5. The power supply terminal of the voltage divider network is connected to the power supply output terminal of the stable power supply module. The pull-up voltage divider arm of the voltage divider network is connected to the collector of the transistor Q1 through a voltage divider resistor R6. The pull-down voltage divider arm of the voltage divider network is connected to the emitter of the transistor Q1. The emitter of the transistor Q1 is grounded. The signal input terminal of the signal amplitude detection unit is connected to the collector of the transistor Q1. The electrode connections are as follows: the output terminal of the signal amplitude detection unit is connected to the input terminal of the control unit; the power supply input terminal of the control unit is connected to the dedicated power supply output terminal of the stable power supply module; the control signal output terminal of the control unit is connected to the control terminal of the voltage divider resistor network; and the interference feedback input terminal of the control unit is connected to the interference detection signal output terminal of the adaptive filter module, used to adjust the voltage division ratio of the voltage divider resistor network according to the signal amplitude feedback and interference feedback signals.

[0015] Furthermore, the adaptive filtering module includes a main branch and a coupling branch; the input terminal of the main branch is connected to the signal output terminal (collector of transistor Q1) of the adaptive gain amplification module, and the main branch sequentially connects a 2-to-1 switch A, a high-pass filter, a 2-to-1 switch B, a band-stop filter, and a 2-to-1 switch C, with the output terminal of the 2-to-1 switch C connected to the input terminal of the signal output module; the coupler input terminal of the coupling branch is connected to the input terminal of the 2-to-1 switch A in the main branch, and the output terminal of the coupler is connected to the band-stop filter... The input terminals of filter A and bandpass filter B are connected, and the output terminals of both bandpass filters A and B are connected to the input terminal of the high-speed detection circuit. The power supply input terminal of the high-speed detection circuit is connected to the power supply output terminal of the stable power supply module. The output terminal of the high-speed detection circuit serves as the control signal output terminal of the coupling branch and is connected to the control terminals of the 2-to-1 switch A, 2-to-1 switch B, and 2-to-1 switch C of the main branch. It is also connected to the interference feedback input terminal of the adaptive gain amplifier module to control the switching of the main branch filter channels.

[0016] Furthermore, the stable power supply module includes a constant current power supply, a power supply voltage detection circuit, and a voltage divider adjustment circuit. The input terminal of the voltage divider adjustment circuit is connected to an industrial DC power supply, and the output terminal of the voltage divider adjustment circuit is connected to the input terminal of the constant current power supply. The detection input terminal of the power supply voltage detection circuit is connected to the input terminal of the voltage divider adjustment circuit, and the output terminal of the power supply voltage detection circuit is connected to the control terminal of the voltage divider adjustment circuit to generate first and second control voltages to control the voltage division ratio of the voltage divider adjustment circuit. The output terminal of the constant current power supply is divided into a general power supply output terminal and a dedicated power supply output terminal. The general power supply output terminal is connected to the power supply input terminal of the signal acquisition module, the opto-isolation module, the adaptive filtering module, and the signal output module. The dedicated power supply output terminal is connected to the power supply input terminal of the control unit of the adaptive gain amplification module. The output voltage range of the constant current power supply is 5~24V.

[0017] Furthermore, the signal output module includes a buffer operational amplifier and an output current-limiting resistor R7; the non-inverting input of the buffer operational amplifier is connected to the main branch output of the adaptive filter module (the output of the 2-to-1 switch C), and the inverting input of the buffer operational amplifier is connected to its own output through a feedback resistor to form a voltage follower; the power supply input of the buffer operational amplifier is connected to the general power supply output of the stable power supply module, and the output of the buffer operational amplifier is connected through the output current-limiting resistor R7 for interfacing with the display unit or control unit of the electromagnetic flowmeter to achieve impedance-matched signal output.

[0018] The beneficial effects of this invention are: This invention effectively solves the problems of poor measurement adaptability and insufficient stability caused by the fragmented signal processing link and lack of linkage between modules in existing electromagnetic flowmeters. It constructs a sequentially connected structure of a signal acquisition module, an opto-isolation module, an adaptive gain amplification module, an adaptive filtering module, and a signal output module, coupled with a stable power supply module and a collaborative design of "bidirectional communication between the adaptive gain amplification module and the adaptive filtering module." This adapts to the wide-range measurement requirements of electromagnetic flowmeters, covering signal processing scenarios from low to high flow rates. It avoids the phenomenon of effective signals being submerged by noise at low flow rates and signal saturation distortion at high flow rates, ensuring the continuity and effectiveness of full-range measurement. When the adaptive filtering module detects power frequency interference or electromagnetic coupling interference in the industrial environment, it can feed back to the adaptive gain amplification module to synchronously adjust the gain to prevent excessive amplification of the interference signal, significantly enhancing the interference suppression capability of the entire link and ensuring the stability of measurement data under complex working conditions such as chemical, water treatment, and metallurgy. The stable power supply module provides targeted power supply guarantees for each module, especially prioritizing the power supply requirements of the adaptive gain amplification module, resisting the influence of industrial power supply voltage fluctuations, ensuring the continuous and stable operation of the core signal processing unit of the electromagnetic flowmeter, and meeting the monitoring needs of continuous industrial production. Attached Figure Description

[0019] Figure 1 This is an overall schematic diagram of an adaptive signal amplification and filtering circuit for an electromagnetic flowmeter proposed in this invention. Figure 2 This is a schematic diagram of the signal acquisition module of an adaptive signal amplification and filtering circuit for an electromagnetic flowmeter proposed in this invention; Figure 3 This is a schematic diagram of the opto-isolation module of the adaptive signal amplification and filtering circuit of an electromagnetic flowmeter proposed in this invention; Figure 4 This is a schematic diagram of the adaptive gain amplification module of the adaptive signal amplification and filtering circuit of an electromagnetic flowmeter proposed in this invention. Figure 5 This is a schematic diagram of the adaptive filtering module of an adaptive signal amplification and filtering circuit for an electromagnetic flowmeter proposed in this invention. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0021] In the description of this application, it should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. For ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0022] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and are not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0023] It should be noted that in the description of this application, the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not 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 on the scope of protection of this application. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0024] It should be noted that, in this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0025] Reference Figures 1 to 5An adaptive signal amplification and filtering circuit for an electromagnetic flowmeter includes a signal acquisition module, an opto-isolation module, an adaptive gain amplification module, an adaptive filtering module, and a signal output module connected in sequence, as well as a stable power supply module that supplies power to each module; the adaptive gain amplification module communicates bidirectionally with the adaptive filtering module, and the stable power supply module is also connected to the adaptive gain amplification module to achieve priority power supply and voltage stabilization control for the adaptive gain amplification module.

[0026] This invention effectively solves the problems of poor measurement adaptability and insufficient stability caused by the fragmented signal processing link and lack of linkage between modules in existing electromagnetic flowmeters. It constructs a sequentially connected structure of a signal acquisition module, an opto-isolation module, an adaptive gain amplification module, an adaptive filtering module, and a signal output module, coupled with a stable power supply module and a collaborative design of "bidirectional communication between the adaptive gain amplification module and the adaptive filtering module." This adapts to the wide-range measurement requirements of electromagnetic flowmeters, covering signal processing scenarios from low to high flow rates, avoiding the phenomenon of effective signals being submerged by noise at low flow rates and signal saturation distortion at high flow rates, ensuring the continuity and effectiveness of full-range measurement. When the adaptive filtering module detects industrial site conditions... In the event of frequency interference or electromagnetic coupling interference, feedback can be sent to the adaptive gain amplifier module to synchronously adjust the gain to avoid excessive amplification of the interference signal, significantly enhancing the end-to-end interference suppression capability and ensuring the stability of measurement data of the electromagnetic flowmeter under complex working conditions such as chemical, water treatment, and metallurgy. The stable power supply module provides targeted power supply protection for each module, especially prioritizing the power supply requirements of the adaptive gain amplifier module, resisting the influence of industrial power supply voltage fluctuations, ensuring the continuous and stable operation of the core signal processing unit of the electromagnetic flowmeter, and meeting the monitoring needs of continuous industrial production. At the same time, the integrated design of each module eliminates the need for additional signal conversion and adaptation circuits, simplifying the overall assembly process and reducing equipment integration and on-site deployment costs.

[0027] In one embodiment of the present invention, the signal acquisition module includes a precision instrumentation operational amplifier, a feedback resistor Rf, and current-limiting resistors R1 and R2. One end of the current-limiting resistor R1 is connected to the positive differential output terminal (V_s+) of the electromagnetic flowmeter sensor, and the other end is connected to the non-inverting input terminal (IN+) of the precision instrumentation operational amplifier. One end of the current-limiting resistor R2 is connected to the negative differential output terminal (V_s-) of the electromagnetic flowmeter sensor, and the other end is connected to the inverting input terminal (IN-) of the precision instrumentation operational amplifier. A feedback resistor Rf is connected in parallel between the inverting input terminal (IN-) and the output terminal of the precision instrumentation operational amplifier to adjust the fixed amplification factor of the precision instrumentation operational amplifier, thereby achieving preliminary amplification and conditioning of the weak differential signal. The power supply input terminal of the precision instrumentation operational amplifier is connected to the general power supply output terminal of the stable power supply module, and the output terminal of the precision instrumentation operational amplifier is connected to the input terminal of the opto-isolation module, for preliminary conditioning and amplification of the weak differential signal (usually at the millivolt level) output by the sensor before transmission to the opto-isolation module. Among them, the current-limiting resistors R1 and R2 can limit the sensor output current within a safe range (preferably 0.1~1mA), avoiding sensor damage caused by abnormal circuit load or short circuit, extending the service life of the electromagnetic flowmeter sensor, and reducing equipment maintenance costs; the precision instrumentation amplifier has a high common-mode rejection ratio (CMRR≥100dB) and low input offset voltage, which can effectively suppress common-mode interference caused by equipment grounding differences and cable coupling in the industrial environment, accurately conditioning the weak differential signal output by the sensor into a stable differential signal, providing a clean input signal for the subsequent amplification module, and laying the foundation for measurement accuracy; the module directly adapts to the differential output interface of the electromagnetic flowmeter sensor, without the need for additional signal conversion circuits, simplifying the overall assembly process of the electromagnetic flowmeter and reducing equipment integration costs.

[0028] In one embodiment of the present invention, the opto-isolation module includes an optocoupler U1, current-limiting resistors R3 and R4, and a clamping diode D1. The optocoupler U1 comprises a photodiode and a phototransistor coupled to each other, and adopts a linear optocoupler to ensure linearity during signal isolation transmission and reduce signal distortion. The anode of the photodiode is connected to the output terminal of the signal acquisition module through the current-limiting resistor R3, and the cathode of the photodiode is grounded. The collector of the phototransistor is connected to the general power supply output terminal of the stable power supply module through the current-limiting resistor R4, and the emitter of the phototransistor is grounded. The collector of the phototransistor serves as the output terminal of the opto-isolation module and is connected to the signal input terminal of the adaptive gain amplifier module. The clamping diode D1 is connected in parallel between the collector and emitter of the phototransistor to clamp the collector output voltage, prevent peak voltage from breaking down the phototransistor, and improve the stability of the module. Optocoupler U1 achieves electrical isolation between the signal acquisition side and the subsequent signal processing circuit, completely blocking strong electrical interference and ground loop interference from entering the core processing unit of the electromagnetic flowmeter through the signal link, avoiding measurement data jumps and false alarms caused by interference; current-limiting resistor R3 controls the operating current of the photodiode in optocoupler U1 (5~10mA), and R4 stabilizes the current transfer ratio of the phototransistor, ensuring linear correspondence of signal amplitude before and after isolation, with minimal signal distortion during isolation (distortion ≤0.5%), which does not affect the measurement accuracy of the electromagnetic flowmeter; it improves the adaptability of the electromagnetic flowmeter to harsh electromagnetic environments, reduces the probability of equipment downtime caused by electromagnetic interference in industrial sites, and is especially suitable for strong electromagnetic interference scenarios such as metallurgy and chemical industries, ensuring the continuity of flow measurement.

[0029] In one embodiment of the present invention, the adaptive gain amplification module includes a gain adjustment unit, a signal amplitude detection unit, and a control unit; the gain adjustment unit consists of a transistor Q1, a base coupling resistor R5, a voltage divider network, a controllable voltage divider (using a digital potentiometer U2), and an accelerating capacitor C1. The transistor Q1 is an NPN high-frequency transistor, adapted to transient signal transmission requirements; the base of the transistor Q1 is connected to the output terminal of the opto-isolation module through the base coupling resistor R5, and the accelerating capacitor C1 is connected in parallel. At both ends of the base coupling resistor R5 (with a preferred capacitance of 100pF~1nF), the signal rise and fall times are accelerated, improving signal response efficiency. The voltage divider network consists of pull-up resistors R6 and R7. The power supply terminal of the voltage divider network is connected to the dedicated power supply output terminal of the stable power supply module. The pull-up voltage divider arm of the voltage divider network is connected to the collector of the transistor Q1 through the voltage divider resistor R6, and the pull-down voltage divider arm of the voltage divider network is connected to the emitter of the transistor Q1. The emitter of transistor Q1 is grounded. The digital potentiometer U2 is connected in series in the pull-down resistor R7 branch to adjust the voltage division ratio. The signal amplitude detection unit consists of a peak detector and a voltage comparator, used to acquire the peak value of the output signal from the collector of transistor Q1 in real time and compare it with preset thresholds (low flow threshold V1, high flow threshold V2), outputting an amplitude detection signal. The signal input terminal of the signal amplitude detection unit is connected to the collector of transistor Q1, and the output terminal of the signal amplitude detection unit is connected to the input terminal of the control unit. The control unit adopts a microcontroller or a dedicated logic chip. The power supply input terminal of the control unit is connected to the dedicated power supply output terminal of the stable power supply module. The control signal output terminal of the control unit is connected to the control terminal of the digital potentiometer U2. The interference feedback input terminal of the control unit is connected to the interference detection signal output terminal of the adaptive filtering module, used to adjust the resistance value of the digital potentiometer U2 according to the signal amplitude feedback and interference feedback signals, thereby adjusting the voltage division ratio of the voltage divider network to achieve adaptive gain adjustment.The above design enables dynamic gain adjustment of 10 to 100 times. At low flow rates, when the signal amplitude detection unit detects a weak signal (below V1), the control unit drives the digital potentiometer U2 to decrease its resistance and increase the voltage division ratio, adjusting the gain to a high level to fully amplify the millivolt-level signal to the volt level, preventing noise from masking the effective signal. At high flow rates, when the signal amplitude detection unit detects a signal amplitude higher than V2, the control unit drives the digital potentiometer U2 to increase its resistance and decrease the voltage division ratio, automatically reducing the gain to a low level to avoid signal saturation distortion and ensure effective amplification of the full-range signal. The accelerating capacitor C1 and resistor R5 are connected in parallel to effectively accelerate the signal rise time, adapting to the electromagnetic flowmeter's monitoring needs for transient flow changes (such as sudden changes in medium velocity in pipelines), improving the device's measurement response speed. Simultaneously, the control unit feeds back the current gain adjustment parameters to the adaptive filtering module, achieving bidirectional collaboration and assisting the filtering module in optimizing filtering parameters. The closed-loop control logic requires no manual intervention for calibration, reducing the on-site maintenance cost of the electromagnetic flowmeter. Through precise gain adjustment, the measurement accuracy of the device is further improved.

[0030] In one embodiment of the present invention, the adaptive filtering module includes a main branch, a coupling branch, and a control logic unit; the input terminal of the main branch is connected to the signal output terminal (collector of transistor Q1) of the adaptive gain amplifier module; the main branch is connected in series with a 2-to-1 switch A, a high-pass filter, a 2-to-1 switch B, a band-stop filter, and a 2-to-1 switch C; the output terminal of the 2-to-1 switch C is connected to the input terminal of the signal output module; the input terminal of the coupler (preferably capacitive coupler C2) of the coupling branch is connected to the input terminal of the 2-to-1 switch A in the main branch; the function of the coupler is to extract the interference signal in the main branch and separate the interference signal from the effective signal; the output terminal of the coupler is connected to the input terminals of band-pass filter A and band-pass filter B, respectively; the center frequency of band-pass filter A is 50Hz (adapted to industrial power frequency interference); the center frequency of band-pass filter B is... The center frequency is 100Hz (adapted to power frequency second harmonic interference) for targeted extraction of interference signals at different frequencies. The outputs of bandpass filters A and B are both connected to the input of the high-speed detection circuit, which uses a peak detection circuit to convert the AC interference signal output by the bandpass filters into a DC control signal. The power supply input of the high-speed detection circuit is connected to the general power supply output of the stable power supply module. The output of the high-speed detection circuit serves as the control signal output of the coupling branch and is connected to the control terminals of the 2-to-1 switches A, B, and C of the main branch. It is also connected to the interference feedback input of the adaptive gain amplifier module to control the switching of the main branch filter channels. The control logic unit is connected to the output of the high-speed detection circuit to analyze the control signal, determine the interference type, and control the switch switching logic. The coupling branch, through a coupler, bandpass filters A / B, and a high-speed detection circuit, can quickly identify common industrial interference signals. A control signal drives a 2-to-1 switch in the main branch to switch the filtering channel. The specific switching logic is as follows: when there is no significant interference, switch A switches to direct-through mode, skipping the filtering stage and ensuring signal transmission speed; when 50Hz power frequency interference is detected, switch A switches to filtering mode, and switch B switches to the band-stop filter branch to attenuate the power frequency interference; when high-frequency electromagnetic coupling interference is detected, switch B switches to the high-pass filter branch to attenuate the high-frequency interference; switch C is used to achieve the final switching between the filtered signal and the direct-through signal, ensuring the integrity of the output signal.The "straight-through / filtered" switching function of the main branch maintains signal transmission speed in scenarios without strong interference and provides precise filtering when interference occurs, balancing the "measurement response speed" and "anti-interference capability" of the electromagnetic flowmeter, and avoiding signal delay or excessive attenuation caused by a single filtering circuit. It can adapt to the interference characteristics of different industrial scenarios (such as factory power frequency interference and metallurgical scenarios with prominent electromagnetic coupling interference) without replacing the filtering module, improving the environmental adaptability of the electromagnetic flowmeter and expanding the application range of the equipment. At the same time, the interference detection signal is fed back to the adaptive gain amplification module to achieve full-link collaborative anti-interference.

[0031] In one embodiment of the present invention, the stable power supply module includes a constant voltage power supply, a power supply voltage detection circuit, a voltage divider adjustment circuit, and a protection diode D2. The voltage divider adjustment circuit consists of an adjustable resistor R8 and voltage divider resistors R9 and R10. The input terminal of the voltage divider adjustment circuit is used to connect to an industrial DC power supply (preferably with an input voltage range of 12~48V DC, suitable for commonly used industrial DC power supply systems). The output terminal of the voltage divider adjustment circuit is connected to the input terminal of the constant voltage power supply. The power supply voltage detection circuit consists of a voltage comparator and a voltage divider sampling resistor. It is used to collect the power supply voltage at the input terminal of the voltage divider adjustment circuit in real time and compare the collected voltage signal with a preset safe voltage range (upper limit Vmax, lower limit Vmin). The detection input terminal of the power supply voltage detection circuit is connected to the input terminal of the voltage divider adjustment circuit, and the output terminal of the power supply voltage detection circuit is connected to the control terminal of the voltage divider adjustment circuit. It is used to generate first and second control voltages to control the voltage divider adjustment circuit. Adjust the resistance value of resistor R8 to adjust the voltage division ratio (increase the voltage division ratio when the input voltage is higher than Vmax; decrease the voltage division ratio when it is lower than Vmin); the output terminals of the constant voltage power supply are divided into a general power supply output terminal and a dedicated power supply output terminal. The general power supply output terminal outputs a stable voltage (preferably 5V or 12V) and connects to the power supply input terminals of the signal acquisition module, opto-isolation module, adaptive filtering module, and signal output module. The dedicated power supply output terminal outputs a stable voltage (preferably 5V) and connects to the power supply input terminal of the control unit of the adaptive gain amplification module. The output voltage accuracy of the constant voltage power supply is ≤ ±0.5% to ensure power supply stability. The constant voltage power supply outputs a stable voltage, precisely matching the rated power requirements of core components such as instrument operational amplifiers, detectors, and analog switches in the electromagnetic flowmeter's signal processing unit. This avoids circuit parameter drift caused by voltage fluctuations and ensures the stability of measurement accuracy. The power supply voltage detection circuit monitors the supply voltage in real time, and the voltage divider adjustment circuit responds quickly. When the input voltage is abnormal, it can quickly adjust the voltage division ratio to protect core components from overvoltage breakdown and extend the overall service life of the electromagnetic flowmeter. The protection diode D2 is connected in series at the input of the voltage divider adjustment circuit to prevent reverse power supply damage to the circuit. The wide input voltage range directly adapts to commonly used industrial DC power supply systems, eliminating the need for an additional power adapter. This simplifies the on-site installation and wiring process of the electromagnetic flowmeter and reduces engineering deployment costs.

[0032] In one embodiment of the present invention, the signal output module includes a buffer operational amplifier, a feedback resistor R11, and an output current-limiting resistor R7. The non-inverting input of the buffer operational amplifier is connected to the main branch output (output of the 2-to-1 switch C) of the adaptive filter module, and the inverting input of the buffer operational amplifier is connected to its own output through the feedback resistor R11 to form a voltage follower. The feedback resistor R11 is used to stabilize the gain of the buffer operational amplifier, suppress temperature drift, and improve the stability of the output signal. The power supply input of the buffer operational amplifier is connected to the general power supply output of the stable power supply module, and the output of the buffer operational amplifier is connected to an industrial standard output interface (e.g., a 4-20mA current interface or a 0-5V voltage interface, conforming to IEC 60381 industrial standard) through the output current-limiting resistor R7 (resistance value 100Ω~1kΩ) for interfacing with the display unit, PLC control unit, or data acquisition terminal of the electromagnetic flowmeter to achieve impedance-matched signal output. The buffered operational amplifier forms a voltage follower with high input impedance and low output impedance, effectively avoiding the influence of impedance load in subsequent circuits on the filtered pure signal, ensuring stable output signal amplitude, and guaranteeing the signal reception accuracy of the electromagnetic flowmeter display unit and control unit. The current-limiting resistor R7 limits the output current, preventing damage to the output module due to short circuits in subsequent circuits, thus improving the safety and reliability of the electromagnetic flowmeter circuit. It has strong signal driving capability, enabling long-distance signal transmission without significant attenuation, and is suitable for scenarios where the electromagnetic flowmeter sensor and display terminal are installed separately (such as deploying the sensor and processing unit on-site, and installing the display terminal in the control room), ensuring the integrity of flow data transmission. Simultaneously, the output interface is compatible with industrial standards, improving the equipment's versatility and compatibility.

[0033] In addition, it should be noted that all resistors in this invention are metal film resistors (accuracy ±1%), and capacitors are ceramic capacitors or electrolytic capacitors, selected according to circuit requirements; all semiconductor devices (transistors, diodes, operational amplifiers, etc.) are industrial-grade devices (operating temperature range -40℃~85℃), suitable for harsh industrial conditions such as chemical and metallurgical industries; each module adopts a single-point grounding design, with signal ground and power ground arranged separately to further suppress ground loop interference and improve circuit stability.

[0034] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. An adaptive signal amplification and filtering circuit for an electromagnetic flowmeter, characterized in that, It includes a signal acquisition module, an opto-isolation module, an adaptive gain amplification module, an adaptive filtering module, and a signal output module connected in sequence, as well as a stable power supply module that supplies power to each module; the adaptive gain amplification module communicates bidirectionally with the adaptive filtering module, and the stable power supply module is also connected to the adaptive gain amplification module.

2. The adaptive signal amplification and filtering circuit of the electromagnetic flowmeter according to claim 1, characterized in that, The signal acquisition module includes a precision instrumentation amplifier and current-limiting resistors R1 and R2. One end of the current-limiting resistor R1 is connected to the positive differential output terminal of the electromagnetic flowmeter sensor, and the other end is connected to the non-inverting input terminal of the precision instrumentation amplifier. One end of the current-limiting resistor R2 is connected to the negative differential output terminal of the electromagnetic flowmeter sensor, and the other end is connected to the inverting input terminal of the precision instrumentation amplifier. The power supply input terminal of the precision instrumentation amplifier is connected to the power supply output terminal of the stable power supply module, and the output terminal of the precision instrumentation amplifier is connected to the input terminal of the opto-isolation module. This module is used to perform preliminary conditioning on the weak differential signal output by the sensor before transmitting it to the opto-isolation module.

3. The adaptive signal amplification and filtering circuit for the electromagnetic flowmeter according to claim 1, characterized in that, The opto-isolation module includes an optocoupler U1 and current-limiting resistors R3 and R4. The optocoupler U1 includes a light-emitting diode (LED) and a phototransistor coupled to each other. The anode of the LED is connected to the output terminal of the signal acquisition module through the current-limiting resistor R3, and the cathode of the LED is grounded. The collector of the phototransistor is connected to the power supply output terminal of the stable power supply module through the current-limiting resistor R4, and the emitter of the phototransistor is grounded. The collector of the phototransistor serves as the output terminal of the opto-isolation module and is connected to the signal input terminal of the adaptive gain amplifier module.

4. The adaptive signal amplification and filtering circuit of the electromagnetic flowmeter according to claim 1, characterized in that, The adaptive gain amplification module includes a gain adjustment unit, a signal amplitude detection unit, and a control unit. The gain adjustment unit consists of a transistor Q1, a base coupling resistor R5, a voltage divider network, a controllable voltage divider component, and an accelerating capacitor C1. The base of transistor Q1 is connected to the output terminal of the opto-isolation module through the base coupling resistor R5. The accelerating capacitor C1 is connected in parallel across the base coupling resistor R5. The power supply terminal of the voltage divider network is connected to the power supply output terminal of the stable power supply module. The pull-up voltage divider arm of the voltage divider network is connected to the collector of transistor Q1 through a voltage divider resistor R6. The pull-down voltage divider arm of the voltage divider network is connected to one end of the controllable voltage divider component. The other end is connected to the emitter of transistor Q1, and the emitter of transistor Q1 is grounded; the signal input terminal of the signal amplitude detection unit is connected to the collector of transistor Q1, the output terminal of the signal amplitude detection unit is connected to the input terminal of the control unit, the power supply input terminal of the control unit is connected to the dedicated power supply output terminal of the stable power supply module, the control signal output terminal of the control unit is connected to the control terminal of the controllable voltage divider, and the interference feedback input terminal of the control unit is connected to the interference detection and control signal output terminal of the adaptive filtering module. This is used to adjust the resistance value of the controllable voltage divider according to the signal amplitude feedback and interference feedback signals, thereby adjusting the voltage division ratio of the voltage divider resistor network to achieve adaptive gain adjustment.

5. The adaptive signal amplification and filtering circuit for the electromagnetic flowmeter according to claim 1, characterized in that, The adaptive filtering module includes a main branch and a coupling branch. The input of the main branch is connected to the signal output of the adaptive gain amplification module. The main branch connects in series a 2-to-1 switch A, a high-pass filter, a 2-to-1 switch B, a band-stop filter, and a 2-to-1 switch C. The other inputs of 2-to-1 switches A, B, and C are all direct paths. The output of 2-to-1 switch C is connected to the input of the signal output module. The coupler input of the coupling branch is connected to the input of 2-to-1 switch A in the main branch. The output of the coupler is connected to the band-pass filter. The input terminals of the circuit are connected to the input terminals of the high-speed detection circuit. The output terminals of the bandpass filters A and B are both connected to the input terminal of the high-speed detection circuit. The power supply input terminal of the high-speed detection circuit is connected to the power supply output terminal of the stable power supply module. The output terminal of the high-speed detection circuit serves as the interference detection and control signal output terminal of the coupling branch. It is connected to the control terminals of the 2-to-1 switches A, B, and C of the main branch, and also to the interference feedback input terminal of the adaptive gain amplifier module. This is used to detect interference signals in the main branch signal and control the switching between the main branch filtering channel and the direct path according to the type of interference signal to achieve adaptive filtering.

6. The adaptive signal amplification and filtering circuit for the electromagnetic flowmeter according to claim 1, characterized in that, The stable power supply module includes a linear regulated power supply, a power supply voltage detection circuit, and a voltage divider adjustment circuit. The input terminal of the voltage divider adjustment circuit is connected to an industrial DC power supply, and the output terminal of the voltage divider adjustment circuit is connected to the input terminal of the linear regulated power supply. The detection input terminal of the power supply voltage detection circuit is connected to the input terminal of the voltage divider adjustment circuit, and the output terminal of the power supply voltage detection circuit is connected to the control terminal of the voltage divider adjustment circuit. This control circuit generates first and second control voltages based on voltage fluctuations in the industrial DC power supply, controlling the voltage division ratio of the voltage divider adjustment circuit to ensure stable voltage input to the linear regulated power supply. The output terminal of the linear regulated power supply is divided into a general-purpose power supply output terminal and a dedicated power supply output terminal. The general-purpose power supply output terminal is connected to the power supply input terminals of the signal acquisition module, opto-isolation module, adaptive filtering module, and signal output module. The dedicated power supply output terminal is connected to the power supply input terminal of the control unit of the adaptive gain amplification module. The output voltage of the linear regulated power supply is a stable DC voltage.

7. The adaptive signal amplification and filtering circuit for the electromagnetic flowmeter according to claim 1, characterized in that, The signal output module includes a buffer operational amplifier and an output current-limiting resistor R7. The non-inverting input of the buffer operational amplifier is connected to the main branch output of the adaptive filter module, and the inverting input of the buffer operational amplifier is directly shorted to its own output to form a voltage follower. The power supply input of the buffer operational amplifier is connected to the general power supply output of the stable power supply module, and the output of the buffer operational amplifier is used as a signal output through the output current-limiting resistor R7 to interface with the display unit or control unit of the electromagnetic flowmeter to achieve impedance-matched signal output.

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