An inductive conductivity sensor radiation EMI simulation prediction method

Abstract

The application discloses an inductive conductivity sensor radiation EMI simulation prediction method, comprising the following steps: S1, establishing a sensor simulation model; S2, based on the working principle of the inductive conductivity sensor, connecting the probe coil of the sensor simulation model with the PCB printed circuit board in components, obtaining an induced voltage prediction model of the probe coil output port; importing the model file of the preset PCB printed circuit board into a board-level electromagnetic simulation software, and obtaining near-field radiation data of the PCB printed circuit board during work; S3, selecting a plurality of frequency points corresponding to a preset radiation threshold according to the near-field radiation data, and recording the radiation electric field values corresponding to the frequency points; S4, setting a point radiation source position by using a three-dimensional electromagnetic field simulation software, so as to add an excitation source; S5, obtaining a predicted induced voltage according to the added excitation source based on the induced voltage prediction model of the probe coil output port; S6, taking the predicted induced voltage as an alternating current equivalent voltage source, and simulating and obtaining the interference caused by the induced voltage of the probe coil output port to an operational amplifier chip according to a pre-constructed operational amplifier working circuit. The application solves the problem that the prior art cannot analyze the interference of the radiation emission of its own components on external components and clearly analyze the influence of the interference on certain chips.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic simulation technology, and in particular to a method for simulating and predicting radiated EMI using an inductive conductivity sensor. Background Technology

[0002] With the rapid development of electronic devices, the problem of electromagnetic interference has become increasingly prominent. As a precision component in electronic devices, sensors are susceptible to damage from both external and internal electromagnetic radiation, which can cause deviations in their output.

[0003] The key component of a conductivity sensor is the probe, which mimics the working principle of a transformer. Its main structure consists of two loop coils. Essentially, it uses the law of electromagnetic induction to create a magnetic circuit between two adjacent coils, thereby generating an induced electromotive force (EMF) in the induction coil. During this process, the conductivity of the solution between the coils significantly affects the induced voltage generated in the induction coil. Therefore, the conductivity of the solution can be calculated by measuring the induced voltage in the induction coil.

[0004] Currently, numerous simulation technologies simulate the impact of drastically changing electromagnetic environments on PCB boards in various ways. Many technologies also perform simulation analysis of PCB radiated emissions at the circuit board level. However, for inductive conductivity sensors, traditional PCB-level analysis neglects the susceptible probe component. Pure probe analysis and pure PCB radiated emission analysis are somewhat distant from reality, resulting in low model-to-physical fit and a lack of simulation of the probe-PCB interaction. The main challenge of this simulation technology lies in the coupling interference between PCB radiated emissions and probe magnetic flux at a certain frequency band.

[0005] The publication number CN116611255A, entitled "A Simulation Method for Electromagnetic Pulse Effect of Electronic Devices Based on Field-Circuit Coordination," is designed to simulate the induced voltage generated on a chip by simulating the drastically changing electromagnetic field in the environment. However, its drawback is that this method only simulates the induced voltage generated on the PCB board when it is subjected to external electromagnetic field interference, and does not consider the influence of its own radiation emission on external components.

[0006] The publication number is CN112394255A, and the title is "A Test Method for Electromagnetic Radiation Susceptibility of PCB Boards". The design uses HFSS to calculate the current and voltage generated at a key pin on the PCB when it is subjected to external electromagnetic field interference. However, its drawback is that it does not take into account the interference caused by the interference current and voltage at the pin entering the directly connected components.

[0007] In summary, there is an urgent need to provide a simulation and prediction method for radiated EMI of inductive conductivity sensors, so as to analyze the interference caused by the radiated emission of the sensor itself to external devices and clearly analyze the impact of this interference on certain chips. Summary of the Invention

[0008] This invention provides a method for simulating and predicting radiated EMI using an inductive conductivity sensor to overcome the aforementioned technical problems.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] A method for radiated EMI simulation and prediction using an inductive conductivity sensor, specifically including the following steps:

[0011] S1: A 3D simulation model of the probe coil of the inductive conductivity sensor was established using the three-dimensional electromagnetic field simulation software Ansys HFSS, and the outer shell of the inductive conductivity sensor was simplified to obtain the sensor simulation model.

[0012] S2: Import the preset PCB printed circuit board model file into the three-dimensional electromagnetic field simulation software Ansys HFSS, and based on the working principle of the inductive conductivity sensor, connect the probe coil of the sensor simulation model to the PCB printed circuit board to obtain the induced voltage prediction model for obtaining the output port of the probe coil.

[0013] At the same time, the model file of the preset PCB printed circuit board is imported into the board-level electromagnetic simulation software Ansys Siwave to obtain the near-field radiation data when the PCB printed circuit board is working.

[0014] S3: Select several frequency points that meet the preset radiation threshold based on the near-field radiation data, and record the radiation electric field value corresponding to each frequency point;

[0015] S4: Set the position of the point radiation source using the 3D electromagnetic field simulation software Ansys HFSS to add an excitation source;

[0016] Furthermore, the frequency and field strength of the excitation source are the frequency points and corresponding radiated electric fields obtained in step S3.

[0017] S5: Induced voltage prediction model based on probe coil output port, which obtains the predicted induced voltage according to the added excitation source;

[0018] S6: Using the predicted induced voltage as an AC equivalent voltage source, and based on the pre-constructed operational amplifier operating circuit, simulate and obtain the interference caused by the induced voltage at the probe coil output port to the operational amplifier chip, thereby realizing the EMI simulation prediction of the radiation from the inductive conductivity sensor.

[0019] Furthermore, S1 specifically includes the following steps:

[0020] S11: Establish a 3D simulation model of the probe coil using the 3D electromagnetic field simulation software Ansys HFSS;

[0021] Furthermore, the 3D simulation model includes the coil conductor structure and the coil core structure;

[0022] S12: Based on the 3D simulation model, the housing of the inductive conductivity sensor is simplified to obtain the sensor simulation model.

[0023] Furthermore, S2 specifically includes the following steps:

[0024] S21: Define the model material of the sensor simulation model, and set the corresponding material parameters of the coil wire, coil core and shell based on the model material to obtain the model of the preset PCB printed circuit board.

[0025] S22: Based on the three-dimensional electromagnetic field simulation software Ansys HFSS, set the basic structural data of the PCB printed circuit board according to the preset PCB printed circuit board model.

[0026] Furthermore, the basic structural data includes at least the laminated materials and their thickness;

[0027] Based on the working principle of the inductive conductivity sensor, the probe coil of the sensor simulation model is connected to the PCB printed circuit board to obtain the induced voltage prediction model for obtaining the output port of the probe coil.

[0028] Furthermore, the method for connecting the probe coil of the sensor simulation model to the PCB printed circuit board is as follows: call the "line" tool in the 3D Modeler of the three-dimensional electromagnetic field simulation software Ansys HFSS to create a straight line, and set the Type of the straight line to "Circle" to obtain the coil wire;

[0029] Use the "Box" tool in the "Create" panel, and combine it with the "Move" and "Rotate" tools to adjust the position and direction of the coil wire so that one end of the coil wire is connected to the probe coil port and the other end is connected to the connection port of the PCB rigid circuit board;

[0030] S23: Using the board-level electromagnetic simulation software Ansys Siwave, based on the preset PCB printed circuit board model, and adding ports according to the preset critical lines, the scattering parameters S of the preset critical lines are obtained.

[0031] S24: Call the Circuit design module to obtain the sensor simulation schematic based on the working principle of the inductive conductivity sensor and the scattering parameter S.

[0032] S25: Based on the sensor simulation schematic, the components of the preset PCB printed circuit board model are imported into the SPICE model, and the near-field radiation simulation of the preset PCB printed circuit board model imported into the SPICE model is performed based on the board-level electromagnetic simulation software Ansys Siwave according to the preset excitation, so as to obtain the near-field radiation data of the PCB printed circuit board when it is working.

[0033] Furthermore, S23 specifically includes the following steps:

[0034] S231: Using Altium Designer software, convert the preset PCB printed circuit board model file to "ODB++" format and import it into Ansys Siwave;

[0035] Then, using the "Generate Port on Selected Nets" tool in Ansys Siwave, based on the preset PCB printed circuit board model file in "ODB++" format, the port of all lines on the PCB printed circuit board is obtained. The ExtendedNet tool is then called to select the lines directly connected to the probe coil wires based on the port of the line, and the probe coil connection model is obtained.

[0036] S232: Set the sweep frequency range parameters;

[0037] Furthermore, the frequency sweep range parameters include the start frequency "Start Freq", the stop frequency "Stop Freq", the number of frequency breakpoints "Number", and the frequency description attribute Distribution;

[0038] The scattering parameters of the probe coil connection model were simulated using the "Launch" tool to obtain the scattering parameter S, and the probe coil connection model after the scattering parameter simulation was defined as the Siwave model.

[0039] S233: Based on Ansys Siwave software and the working principle of inductive conductivity sensor, the sensor simulation schematic is built and obtained according to the Siwave model file and the preset crystal oscillator and rectifier diode SPICE model.

[0040] S234: Use the "Project Manager" tool to set the step size and simulation time in Analysis Control, and combine it with the Circuit design tool to perform transient simulation of the inductive conductivity sensor and obtain the simulation result file;

[0041] S235: Name the simulation result file "NearField Simulation 1";

[0042] Based on the set frequency sweep range parameters, the "Launch" tool is called to perform near-field radiated emission simulation and obtain near-field radiation data when the PCB printed circuit board is in operation.

[0043] Furthermore, in S3, several frequency points that meet the preset radiation threshold are selected based on the near-field radiation data, and the radiated electric field value corresponding to each frequency point is recorded. Specifically,

[0044] Set a preset radiation threshold;

[0045] Based on "NearField Simulation 1" in the "Result" interface, call the "Max.Field.Plot" tool to obtain the relationship data between radiation intensity values ​​and frequency;

[0046] Export the relational data, and select several frequency points within the frequency sweep range whose radiation intensity meets the preset radiation threshold based on the "Export to Electronics desktop" tool, and record the radiation electric field value corresponding to each frequency point.

[0047] Furthermore, S4 uses the 3D electromagnetic field simulation software Ansys HFSS to set the location of the point radiation source for adding excitation sources, specifically...

[0048] Use the "Create a Point" tool to set the location where a point source can be placed, and use it as the location of a point radiation source;

[0049] Use the "Excitations" tool to select the "Lumped Port" port. According to the properties window of the "Lumped Port" port, set the excitation signal frequency of the "Lumped Port" port to the frequency point where the near-field radiation field strength meets the preset radiation threshold. Also, set the direction of the excitation source to coincide with the plane normal and set the amplitude intensity to the radiation electric field value corresponding to the frequency point that meets the preset radiation threshold.

[0050] Furthermore, in S5, the induced voltage prediction module based on the probe coil output port obtains the predicted induced voltage according to the added excitation source, specifically as follows:

[0051] Set the probe location point, and set a straight line segment Polyline1 between the probe location point and the preset ground wire;

[0052] Input formula in the Caculator function tool

[0053] Integrate(Line(Polyline1),Real(ScalarX(<Ex,Ey,Ez> )));

[0054] Where Integrate is the integral function; Polyline1 is the line segment through which the integral function acts;

[0055] By obtaining the integral of the electric field of the probe coil on the Polyline1 line segment and adding it to namedexpression, the port induced voltage output by the probe coil can be obtained.

[0056] Furthermore, S6 specifically includes the following steps:

[0057] S61: Connect the output terminal of the probe coil directly to the input terminal of the operational amplifier;

[0058] S62: Use the port-induced voltage as an AC equivalent voltage source in the operational amplifier operating circuit constructed in the circuit simulation software;

[0059] S63: By using the port induced voltage output by the probe coil as the input excitation to the operational amplifier chip circuit, the output voltage of the operational amplifier chip circuit is detected and obtained, and the noise and interference signal after the port induced voltage output by the probe coil is amplified is obtained to simulate the interference caused by the port induced voltage to the operational amplifier chip.

[0060] This enables EMI simulation and prediction of radiation from inductive conductivity sensors.

[0061] Beneficial Effects: This invention provides a method for simulating and predicting radiated EMI from an inductive conductivity sensor. A simplified 3D model of the probe coil is created in electromagnetic simulation software. The same PCB model is imported into board-level electromagnetic simulation software, and an equivalent excitation source is placed on the PCB to simulate near-field radiated emissions from the module. The induced voltage at the output port of the probe coil is measured in 3D electromagnetic field simulation software, and this induced voltage is extracted and added as an equivalent source to the circuit simulation software to simulate the interference caused by the induced voltage and current to the operational amplifier chip. This not only solves the problem of radiated emissions from the PCB and coupling interference from the probe's magnetic flux, but also allows for rapid analysis of the impact of this radiated interference on the directly connected operational amplifier through circuit simulation software. This eliminates the need for extensive hardware platform construction and provides convenient and efficient EMI radiated emission prediction in the early stages of circuit design. Attached Figure Description

[0062] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0063] Figure 1 This is a flowchart of the radiated EMI simulation and prediction method of the inductive conductivity sensor of the present invention.

[0064] Figure 2 This is a schematic diagram of the sensor probe coil simulation model in this embodiment;

[0065] Figure 3 This is a schematic diagram of the connection between the probe coil and the PCB board in this embodiment;

[0066] Figure 4 This is the circuit schematic of TI-TINA, the example simulation software circuit in this embodiment;

[0067] Figure 5 This is a waveform diagram of the interference voltage at the output terminal of the operational amplifier chip in this embodiment. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0069] This embodiment provides a method for simulating and predicting radiated EMI using an inductive conductivity sensor, such as... Figure 1 As shown, the specific steps include:

[0070] S1: A 3D simulation model of the probe coil of the inductive conductivity sensor was created using the 3D electromagnetic field simulation software Ansys HFSS. The outer casing of the inductive conductivity sensor was simplified to obtain the sensor simulation model, such as... Figure 2 As shown;

[0071] Specifically, the following steps are included:

[0072] S11: A 3D simulation model of the probe coil is established using the 3D electromagnetic field simulation software Ansys HFSS; and the 3D simulation model includes the coil conductor structure and the coil core structure; such as Figure 2 As shown, 2 represents the coil wire structure; 1 represents the housing structure of the inductive conductivity sensor.

[0073] Specifically, a 3D simulation model of the probe coil was established in the 3D electromagnetic field simulation software Anyss HFSS.

[0074] In the modeling window of the 3D electromagnetic field simulation software, click Equation Based Curve and set the curve parameters:

[0075] X(_t):(0.01025+0.0031819*sin(_t*2*pi*150)*cos(_t*2*pi))

[0076] Y(_t):(0.01025+0.0031819*sin(_t*2*pi*150)*sin(_t*2*pi))

[0077] Z(_t):0.0031819*cos(_t*2*pi*150)

[0078] Solenoid radius: 0.01025 (m), Ring radius: 0.0031819 (m)

[0079] Where X(_t) represents the coordinate of the curve in the X-axis direction, which changes with _t; Y(_t) represents the coordinate of the curve in the Y-axis direction, which changes with _t; Z(_t) represents the coordinate of the curve in the Z-axis direction, which changes with _t; pi represents pi, approximately equal to 3.14159; _t is a parameter representing the amount of change of the curve with time or path progression, used to control the position of the curve; and the setting parameters involved in establishing the 3D simulation model of the probe coil are shown in Table 1.

[0080] Table 1. Setting parameters involved in establishing the 3D simulation model of the probe coil

[0081]

[0082] Having obtained the outer wire structure of the probe coil, it is also necessary to draw the coil core structure. Specifically: draw a cylinder with a diameter of 25mm and a height of 4.5mm centered at CenterPosition(0, 0, -2.25), and set the cylinder's direction to be parallel to the z-axis, naming it Cylinder_1; then draw a cylinder with a diameter of 16mm and a height of 4.5mm centered at CenterPosition(0, 0, -2.25), and set the cylinder's direction to be parallel to the z-axis, naming it Cylinder_2; finally, click "Edit" -> "Boolean" -> "Substract", set Cylinder_1 as Blank Parts, set Cylinder_2 as Tool Parts, and subtract Cylinder_2 from Cylinder_1 to obtain a ring-shaped core structure with an outer diameter of 25mm, an inner diameter of 16mm, and a height of 4.5mm.

[0083] S12: Based on the 3D simulation model, the housing of the inductive conductivity sensor is simplified to obtain the sensor simulation model. Specifically, the housing structure of the inductive conductivity sensor involved in this embodiment has a connection structure between the coil and the display module. However, considering that this connection structure is not regular and has little impact on the results, retaining it during modeling may add many unnecessary meshes and increase unnecessary computation to some extent. Therefore, this embodiment simplifies the housing of the inductive conductivity sensor into a circular cylindrical structure. The specific implementation process is as follows:

[0084] Draw a cylinder with a diameter of 30mm and a height of 16mm centered at Center Position (0, 0, -3). Set the cylinder's orientation to be parallel to the z-axis and name it Cylinder_3. Then, draw another cylinder with a diameter of 14mm and a height of 16mm centered at Center Position (0, 0, -3). Set the cylinder's orientation to be parallel to the z-axis and name it Cylinder_4. Click "Edit" -> "Boolean" -> "Substract" in sequence. Set Cylinder_3 as BlankParts and Cylinder_4 as Tool Parts. Subtract Cylinder_4 from Cylinder_3 to obtain a shell structure with an outer diameter of 30mm, an inner diameter of 16mm, and a height of 16mm. Figure 1 Middle structure 1.

[0085] S2: Import the preset PCB printed circuit board model file into the three-dimensional electromagnetic field simulation software Ansys HFSS, and based on the working principle of the inductive conductivity sensor, connect the probe coil of the sensor simulation model to the PCB printed circuit board to obtain the induced voltage prediction model for obtaining the output port of the probe coil.

[0086] At the same time, the model file of the preset PCB printed circuit board is imported into the board-level electromagnetic simulation software Ansys Siwave to obtain the near-field radiation data when the PCB printed circuit board is working.

[0087] Specifically, the following steps are included:

[0088] S21: Define the model material of the sensor simulation model, and set the corresponding material parameters of the coil wire, coil core and shell based on the model material to obtain the model of the preset PCB printed circuit board.

[0089] In HFSS, a material is defined as Polyamide, with its relative permittivity (εr) and loss tangent (tanδ) set to εr = 2.7 and tanδ = 0.01, respectively.

[0090] In HFSS, another material is defined as Silicon Steel, with a relative permittivity of 12, a bulk conductivity of 0.5 siemens / m, and a relative permeability (μr) of 1250.

[0091] Select the coil wire and set its material to Copper;

[0092] Select the coil core and set its material to Silicon Steel;

[0093] Select the shell and set its material to Polyamide;

[0094] Furthermore, the volume region attributes of the sensor simulation model are set, and the volume region attributes are set to vacuum;

[0095] S22: Based on the three-dimensional electromagnetic field simulation software Ansys HFSS, set the basic structural data of the PCB printed circuit board according to the preset PCB printed circuit board model.

[0096] Furthermore, the basic structural data includes at least the laminated materials and their thickness;

[0097] Specifically, import the preset PCB printed circuit board model file into HFSS and set the stack-up material and thickness, that is, set the PCB material to FR4 (Flame-Retardant4), and its dimensions to x (length), y (width), z (height); relative permittivity εr = 4.6, tanδ = 0.1;

[0098] In Altium Designer, the drawn PCB board can be exported in two forms. One is as a STEP 3D file, which can then be directly imported into HFSS. The other is as an ODB++ file, exporting the top, bottom, and signal layers of the PCB board and packaging them into a compressed file for importing the PCB board model into Siwave. In this embodiment, the PCB board dimensions are x (length) = 83.5mm, y (width) = 50mm, and z (height) = 1.6mm.

[0099] Set the material properties of each layer of the PCB printed circuit board;

[0100] Specifically, the rigid PCB is divided into three layers: two copper foil layers on the top and bottom and a dielectric layer in the middle. The thickness of the copper foil layer is 35μm and the thickness of the dielectric layer is 1.53mm. The copper foil layer is selected and its material property is set to Copper, and the dielectric layer in the middle is selected and its material property is set to FR4.

[0101] like Figure 3 As shown, based on the working principle of the inductive conductivity sensor, the probe coil of the sensor simulation model is connected to the PCB printed circuit board to obtain the induced voltage prediction model for obtaining the output port of the probe coil.

[0102] Furthermore, the method for connecting the probe coil of the sensor simulation model to the PCB printed circuit board is as follows: use the "line" tool in the 3D Modeler panel of the three-dimensional electromagnetic field simulation software Ansys HFSS to create a straight line and set its Type to "Circle" to create a wire.

[0103] Click the "Box" tool in the "Create" panel, and use the "Move" and "Rotate" tools to adjust the position and direction of the wire so that one end of the wire is connected to the probe coil port and the other end is connected to the connection port of the PCB rigid circuit board; select the wire object, set the material properties in "PropertyManager", and select "Perfect E" as the material;

[0104] S23: Using the board-level electromagnetic simulation software Ansys Siwave, based on the model of the preset PCB printed circuit board, and adding ports according to the preset critical lines, the scattering parameters S of the preset critical lines are obtained; that is, the model file of the preset PCB printed circuit board is imported into the board-level electromagnetic simulation software Ansys Siwave, and ports are added to the preset critical lines of the preset PCB printed circuit board to obtain the scattering parameters S of the preset critical lines.

[0105] S24: Call the Circuit design module to obtain the sensor simulation schematic based on the working principle of the inductive conductivity sensor and the scattering parameter S.

[0106] S25: Based on the completed sensor simulation schematic, import the components of the preset PCB printed circuit board into the SPICE model, and input the preset excitation into the board-level electromagnetic simulation software Ansys Siwave to perform near-field radiation simulation in order to obtain near-field radiation data when the PCB printed circuit board is working.

[0107] During operation, the high-frequency oscillation of a crystal oscillator causes the charge within the crystal to move back and forth, generating high-frequency electric and magnetic fields in space. These electromagnetic waves propagate outward as radio waves, forming electromagnetic radiation. In AC-DC circuits, rectifier diodes are typically used as switching elements. When a diode switches from the on state to the off state, or vice versa, its internal electric field and current change rapidly; this rapid change in electric field and current generates electromagnetic radiation.

[0108] S23 specifically includes the following steps:

[0109] S231: Using Altium Designer software, convert the preset PCB printed circuit board model file to "ODB++" format and import it into Ansys Siwave;

[0110] That is, by clicking "import" in Ansys Siwave software, selecting "ODB++" format, and importing the preset PCB printed circuit board model file;

[0111] Select all the lines on the PCB printed circuit board, click "Generate Port on SelectedNets" to create a line port, and check the lines that are directly connected to the probe coil wires in the ExtendedNet interface;

[0112] S232: Set the sweep frequency range parameters;

[0113] Furthermore, the frequency sweep range parameters include the start frequency "Start Freq", the stop frequency "Stop Freq", the number of frequency breakpoints "Number", and the frequency description attribute Distribution;

[0114] The scattering parameters of the probe coil connection model were simulated using the "Launch" tool to obtain the scattering parameter S, and the probe coil connection model after the scattering parameter simulation was defined as the Siwave model.

[0115] That is, by clicking "Simulation" -> "Compute SYZ Parameter" -> setting the frequency range "Frequency Range Setup", setting "Start Freq" to 0 Hz and "Stop Freq" to 1 GHz, setting the breakpoint number to 1000, and setting the distribution to "Linear";

[0116] Click “Launch” to perform parameter simulation of scattering parameter S, and define the probe coil connection model after scattering parameter simulation as the Siwave model;

[0117] S233: Based on the working principle of Ansys Siwave software and inductive conductivity sensor, the sensor simulation schematic is built and obtained according to the Siwave model file and the preset SPICE model of crystal oscillator and rectifier diode; that is, after simulating the scattering parameter S in Ansys Siwave software, the Siwave model file is imported into the "CircuitDesign" module of the three-dimensional electromagnetic field simulation software Ansys HFSS.

[0118] Open the "Circuit design" module in "Ansys Electrical Desktop";

[0119] Click "Siwave" in the "Model" interface and select the Siwave project file "Board_Siwave.siw" after the simulation is complete.

[0120] Furthermore, the "Board_Siwave.siw" file is the Siwave model file.

[0121] After importing the Siwave model file, the SPICE models of the crystal oscillator and rectifier diodes are imported into the three-dimensional electromagnetic field simulation software Ansys HFSS, and the sensor simulation schematic is built in Circuit design according to the working principle of the inductive conductivity sensor.

[0122] S234: Use the "Project Manager" tool to set the step size and simulation time in Analysis Control, and combine it with the Circuit design tool to perform transient simulation of the inductive conductivity sensor and obtain the simulation result file; that is, set the step size and simulation time in Analysis Control through "Project Manager", perform transient simulation of the inductive conductivity sensor through Circuit design, and feed the results back to Ansys Siwave software.

[0123] S235: Name the simulation result file “NearField Simulation 1”; and according to the set sweep frequency range parameters, call the “Launch” tool to perform near-field radiated emission simulation and obtain near-field radiation data when the PCB printed circuit board is working; that is, open the Siwave project file “Board_Siwave.siw” with Ansys Siwave software.

[0124] In Simulation, click “Compute Near Field” and name the simulation result file “NearField Simulation 1”. Then, in the “Frequency Range Setup”, set “Start Freq” to 0 Hz, “Stop Freq” to 1 GHz, the number of breakpoints to 1000, and “Distribution” to “Linear”.

[0125] Click “Launch” to perform near-field radiated emission simulation to obtain near-field radiation data when the PCB printed circuit board is in operation;

[0126] S3: Select several frequency points that meet the preset radiation threshold based on the near-field radiation data, and record the radiated electric field value corresponding to each frequency point. Specifically:

[0127] Set a preset radiation threshold;

[0128] Double-clicking "NearField Simulation 1" in the "Result" interface will display the relationship between radiation intensity and frequency in "Max.Field.Plot".

[0129] Export the relational data, click "Export to Electronics desktop", select several frequency points within the frequency sweep range where the radiation intensity meets the preset radiation threshold, and record the radiation electric field value corresponding to each frequency point;

[0130] S4: The location of the point radiation source is set using the three-dimensional electromagnetic field simulation software Ansys HFSS for adding an excitation source; and the frequency and field strength of the excitation source are the frequency points and corresponding radiated electric fields obtained in step S3, specifically...

[0131] By clicking the "Create a Point" button and setting the location where the point source can be placed, it can be used as the location of the point radiation source;

[0132] Click “Excitations”, then select “Assign” -> “LumpedPort”.

[0133] Furthermore, in the properties window of the "LumpedPort" port, set the excitation signal frequency of the port to the frequency point where the near-field radiation field strength meets the preset radiation threshold, and determine that the direction of the excitation source coincides with the plane normal, and set the amplitude intensity to the radiation electric field value corresponding to the frequency point that meets the preset radiation threshold.

[0134] S5: Based on the added excitation source, the port induced voltage output by the probe coil is obtained using the 3D electromagnetic field simulation software Ansys HFSS. Specifically:

[0135] Add a point at the location where the probe is set, and obtain a straight line segment Polyline1 between this point and the preset ground line;

[0136] Click and select fields -> Calculator, then enter the formula: Integrate(Line(Polyline1), Real(ScalarX(<Ex,Ey,Ez> Its principle is that the induced voltage U = Ex, where Integrate is the integral function; Polyline1 is the line segment through which the integral function acts; Real(ScalarX(<Ex,Ey,Ez> )) represents the operation of taking the real part of the component of the electric field E in the X-axis direction; ScalarX(<Ex,Ey,Ez> ) represents the component of electric field E in the X-axis direction; Ex represents the component of electric field E in the X-axis direction; Ey represents the component of electric field E in the Y-axis direction; Ez represents the component of electric field E in the Z-axis direction.

[0137] By obtaining the integral of the electric field on the Polyline1 line segment and adding it to the named expression, the port induced voltage output by the probe coil can be obtained.

[0138] S6: The port-induced voltage is used as an AC equivalent voltage source and added to the pre-built operational amplifier circuit in the circuit simulation software to simulate the interference caused by the port-induced voltage to the operational amplifier chip, thereby realizing the EMI simulation prediction of the inductive conductivity sensor radiation.

[0139] Specifically, the following steps are included:

[0140] S61: Connect the output terminal of the probe coil directly to the input terminal of the operational amplifier;

[0141] Specifically, by directly connecting the output of the probe coil to the input of the operational amplifier OPA2134, any noise or interference appearing in the coil could be amplified by the operational amplifier. To simulate this process, a circuit needs to be built in the circuit software and a simulation experiment needs to be conducted; for example... Figure 4 As shown, and in this embodiment, the pre-built circuit TI-TINA is selected as the example circuit for the simulation software;

[0142] The operational amplifier OPA2134 is a chip developed by Texas Instruments. In TI-TINA, the SPICE model of this chip can be directly called to build the circuit. The extracted induced voltage is used as the input excitation to the working circuit of the operational amplifier chip. By setting a probe at the output port to detect the output voltage, the amplified noise and interference signal can be measured.

[0143] S62: Use the port induced voltage as an AC equivalent voltage source and add it to the operational amplifier working circuit built in the circuit simulation software;

[0144] S63: By using the port induced voltage output by the probe coil as the input excitation to the operational amplifier chip circuit, the output voltage of the operational amplifier chip circuit is detected and obtained, and the noise and interference signal after the port induced voltage output by the probe coil is amplified is obtained to simulate the interference caused by the port induced voltage to the operational amplifier chip.

[0145] This enables EMI simulation and prediction of radiation from inductive conductivity sensors.

[0146] Specifically, in this embodiment, an AC equivalent voltage source 'voltage generator' is placed at the input terminal of the operational amplifier OPA2134, the signal waveform is set to 'sine wave', the amplitude 'Amplitude[V](A)' is set to the obtained induced voltage value, and the frequency 'Frequency[Hz](f)' is the operating frequency of the equivalent source; a probe 'Voltage Pin' is set at the output port of the operational amplifier OPA2134 to record the voltage output by the op-amp, such as... Figure 5 As shown in the figure, Vout is the interference voltage waveform at the output of the operational amplifier.

[0147] Compared with existing technologies, this embodiment provides a method for simulating and predicting radiated EMI using an inductive conductivity sensor, which has the following advantages:

[0148] This embodiment first establishes a simplified 3D model of the probe coil in electromagnetic simulation software. Then, it imports the same PCB board model into board-level electromagnetic simulation software and places an equivalent excitation source on the PCB board to simulate the near-field radiated emission of the module. Finally, it measures and calculates the induced voltage at the output port of the probe coil in three-dimensional electromagnetic field simulation software, extracts this induced voltage, and then adds it as an equivalent source to the circuit simulation software to simulate the interference caused by the induced voltage and induced current to the operational amplifier chip. Therefore, this method not only solves the problem of radiated emission from the PCB and coupling interference from the probe flux linkage, but also allows the introduction of circuit simulation software to quickly obtain the impact of this radiated interference on the directly connected operational amplifier without spending a lot of time building a hardware platform. This provides convenient and efficient EMI radiated emission prediction in the early stages of circuit design.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for simulating and predicting radiated EMI using an inductive conductivity sensor, characterized in that, Specifically, the following steps are included: S1: A 3D simulation model of the probe coil of the inductive conductivity sensor was established using the three-dimensional electromagnetic field simulation software Ansys HFSS, and the outer shell of the inductive conductivity sensor was simplified to obtain the sensor simulation model. S2: Import the preset PCB printed circuit board model file into the three-dimensional electromagnetic field simulation software Ansys HFSS, and based on the working principle of the inductive conductivity sensor, connect the probe coil of the sensor simulation model to the PCB printed circuit board to obtain the induced voltage prediction model for obtaining the output port of the probe coil. At the same time, the model file of the preset PCB printed circuit board is imported into the board-level electromagnetic simulation software Ansys Siwave to obtain the near-field radiation data when the PCB printed circuit board is working. S3: Select several frequency points that meet the preset radiation threshold based on the near-field radiation data, and record the radiation electric field value corresponding to each frequency point; S4: Set the position of the point radiation source using the 3D electromagnetic field simulation software Ansys HFSS to add an excitation source; Furthermore, the frequency and field strength of the excitation source are the frequency points and corresponding radiated electric field values ​​obtained in step S3. S5: Induced voltage prediction model based on probe coil output port, which obtains the predicted induced voltage according to the added excitation source; S6: Using the predicted induced voltage as an AC equivalent voltage source, and based on the pre-constructed operational amplifier operating circuit, simulate and obtain the interference caused by the induced voltage at the probe coil output port to the operational amplifier chip, thereby realizing the EMI simulation prediction of the radiation from the inductive conductivity sensor.

2. The method for radiated EMI simulation and prediction using an inductive conductivity sensor according to claim 1, characterized in that, S1 specifically includes the following steps: S11: Establish a 3D simulation model of the probe coil using the 3D electromagnetic field simulation software Ansys HFSS; Furthermore, the 3D simulation model includes the coil conductor structure and the coil core structure; S12: Based on the 3D simulation model, the housing of the inductive conductivity sensor is simplified to obtain the sensor simulation model.

3. The method for radiated EMI simulation and prediction using an inductive conductivity sensor according to claim 2, characterized in that, S2 specifically includes the following steps: S21: Define the model material of the sensor simulation model, and set the corresponding material parameters of the coil wire, coil core and shell based on the model material to obtain the model of the preset PCB printed circuit board. S22: Based on the three-dimensional electromagnetic field simulation software Ansys HFSS, set the basic structural data of the PCB printed circuit board according to the preset PCB printed circuit board model. Furthermore, the basic structural data includes at least the laminated materials and their thickness; Based on the working principle of the inductive conductivity sensor, the probe coil of the sensor simulation model is connected to the PCB printed circuit board to obtain the induced voltage prediction model for obtaining the output port of the probe coil. Furthermore, the method for connecting the probe coil of the sensor simulation model to the PCB printed circuit board is as follows: call the "line" tool in the 3D Modeler of the three-dimensional electromagnetic field simulation software Ansys HFSS to create a straight line, and set the Type of the straight line to "Circle" to obtain the coil wire; Use the "Box" tool in the "Create" panel, and combine it with the "Move" and "Rotate" tools to adjust the position and direction of the coil wire so that one end of the coil wire is connected to the probe coil port and the other end is connected to the connection port of the PCB rigid circuit board; S23: Using the board-level electromagnetic simulation software Ansys Siwave, based on the preset PCB printed circuit board model, and adding ports according to the preset critical lines, the scattering parameters S of the preset critical lines are obtained. S24: Call the Circuit design module to obtain the sensor simulation schematic based on the working principle of the inductive conductivity sensor and the scattering parameter S. S25: Based on the sensor simulation schematic, the components of the preset PCB printed circuit board model are imported into the SPICE model, and the near-field radiation simulation of the preset PCB printed circuit board model imported into the SPICE model is performed based on the board-level electromagnetic simulation software Ansys Siwave according to the preset excitation, so as to obtain the near-field radiation data of the PCB printed circuit board when it is working.

4. The radiated EMI simulation and prediction method for an inductive conductivity sensor according to claim 3, characterized in that, S23 specifically includes the following steps: S231: Using Altium Designer software, convert the preset PCB printed circuit board model file to "ODB++" format and import it into Ansys Siwave; Then, using the "Generate Port on Selected Nets" tool in Ansys Siwave, based on the preset PCB printed circuit board model file in "ODB++" format, the port of all lines on the PCB printed circuit board is obtained. The Extended Net tool is then called to select the lines directly connected to the probe coil wires based on the port, and the probe coil connection model is obtained. S232: Set the sweep frequency range parameters; Furthermore, the frequency sweep range parameters include the start frequency "Start Freq", the stop frequency "Stop Freq", the number of frequency breakpoints "Number", and the frequency description attribute Distribution; The scattering parameters of the probe coil connection model were simulated using the "Launch" tool to obtain the scattering parameter S, and the probe coil connection model after the scattering parameter simulation was defined as the Siwave model. S233: Based on Ansys Siwave software and the working principle of inductive conductivity sensor, the sensor simulation schematic is built and obtained according to the Siwave model file and the preset crystal oscillator and rectifier diode SPICE model. S234: Use the "Project Manager" tool to set the step size and simulation time in Analysis Control, and combine it with the Circuit design tool to perform transient simulation of the inductive conductivity sensor and obtain the simulation result file; S235: Name the simulation result file "Near Field Simulation 1"; Based on the set frequency sweep range parameters, the "Launch" tool is called to perform near-field radiated emission simulation and obtain near-field radiation data when the PCB printed circuit board is in operation.

5. The method for radiated EMI simulation and prediction using an inductive conductivity sensor according to claim 4, characterized in that, In S3, several frequency points that meet the preset radiation threshold are selected based on the near-field radiation data, and the radiated electric field value corresponding to each frequency point is recorded. Specifically, Set a preset radiation threshold; Based on "Near Field Simulation 1" in the "Result" interface, use the "Max.Field.Plot" tool to obtain the relationship data between radiation intensity values ​​and frequency; Export the relational data, and select several frequency points within the frequency sweep range whose radiation intensity meets the preset radiation threshold based on the "Export to Electronics desktop" tool, and record the radiated electric field value corresponding to each frequency point.

6. The radiated EMI simulation and prediction method for an inductive conductivity sensor according to claim 5, characterized in that, S4 uses the 3D electromagnetic field simulation software Ansys HFSS to set the location of the point radiation source for adding excitation sources, specifically... Use the "Create a Point" tool to set the location where a point source can be placed, and use it as the location of a point radiation source; Use the "Excitations" tool to select the "Lumped Port" port. According to the properties window of the "Lumped Port" port, set the excitation signal frequency of the "Lumped Port" port to the frequency point where the near-field radiation field strength meets the preset radiation threshold. Also, set the direction of the excitation source to coincide with the plane normal and set the amplitude intensity to the radiation electric field value corresponding to the frequency point that meets the preset radiation threshold.

7. The method for radiated EMI simulation and prediction using an inductive conductivity sensor according to claim 6, characterized in that, The induced voltage prediction module in S5, based on the probe coil output port, obtains the predicted induced voltage according to the added excitation source, specifically as follows: Set the probe location point, and set a straight line segment Polyline1 between the probe location point and the preset ground wire; Input formula in the Caculator function tool Integrate(Line(Polyline1),Real(ScalarX(<Ex,Ey,Ez> ))); Where Integrate is the integral function; Polyline1 is the line segment through which the integral function acts; Real(ScalarX(<Ex,Ey,Ez> )) represents the operation of taking the real part of the component of the electric field E in the X-axis direction; ScalarX(<Ex,Ey,Ez> ) represents the component of electric field E in the X-axis direction; Ex represents the component of electric field E in the X-axis direction; Ey represents the component of electric field E in the Y-axis direction; Ez represents the component of electric field E in the Z-axis direction. To obtain the integral of the electric field of the probe coil on the Polyline1 line segment, add it to namedexpression to obtain the port induced voltage output by the probe coil.

8. The method for radiated EMI simulation and prediction using an inductive conductivity sensor according to claim 7, characterized in that, S6 specifically includes the following steps: S61: Connect the output terminal of the probe coil directly to the input terminal of the operational amplifier; S62: Use the port-induced voltage as an AC equivalent voltage source in the operational amplifier operating circuit constructed in the circuit simulation software; S63: By using the port induced voltage output by the probe coil as the input excitation to the operational amplifier chip circuit, the output voltage of the operational amplifier chip circuit is detected and obtained, and the noise and interference signal after the port induced voltage output by the probe coil is amplified is obtained to simulate the interference caused by the port induced voltage to the operational amplifier chip. This enables EMI simulation and prediction of radiation from inductive conductivity sensors.

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