Induction type conductivity sensor radiation EMI simulation prediction method

Abstract

The invention discloses a radiation EMI simulation prediction method for an inductive conductivity sensor. The method comprises the following steps: S1, establishing a sensor simulation model; s2, on the basis of the working principle of the inductive conductivity sensor, performing component connection on a probe coil of the sensor simulation model and a PCB (Printed Circuit Board) to obtain an induced voltage prediction model of an output port of the probe coil; importing a preset model file of the PCB into board-level electromagnetic simulation software, and obtaining near-field radiation data when the PCB works; s3, selecting a plurality of corresponding frequency points meeting a preset radiation threshold according to the near-field radiation data, and recording a radiation electric field value corresponding to each frequency point; s4, setting a point radiation source position through three-dimensional electromagnetic field simulation software so as to add an excitation source; s5, based on an induced voltage prediction model of an output port of the probe coil, obtaining predicted induced voltage according to the added excitation source; and S6, taking the predicted induced voltage as an alternating-current equivalent voltage source, and simulating and obtaining the interference of the induced voltage of the output port of the probe coil on an operational amplifier chip according to a pre-constructed operational amplifier working circuit. The problem that in the prior art, interference generated by radiation emission of components and parts on external devices cannot be analyzed, and the influence of the interference on some chips cannot be clearly analyzed is solved.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic simulation technology, and in particular to a simulation prediction method for EMI radiation of an inductive conductivity sensor. Background Art

[0002] With the rapid development of electronic equipment, the severity of electromagnetic interference has become increasingly prominent. As a precision component in electronic equipment, the sensor will be affected by both external and internal electromagnetic radiation, causing a certain deviation in its output.

[0003] The key part of the conductivity sensor is the probe part, which imitates the working principle of the transformer, and the main structure consists of two ring coils. Its essence is to build a magnetic circuit between two adjacent coils through the law of electromagnetic induction to generate an induced electromotive force on the induction coil. In this process, the conductivity of the solution between the coils will greatly affect the induced voltage generated on the induction coil, so the conductivity of the solution can be calculated by measuring the induced voltage on the induction coil.

[0004] There are many simulation technologies that simulate the impact of drastically changing electromagnetic environments on PCBs in different ways. There are also many technologies that simulate and analyze PCB radiation emissions at the circuit board level. However, for inductive conductivity sensors, traditional PCB board-level analysis ignores the easily affected probe part. Pure probe analysis and pure PCB radiation emission analysis are somewhat distant from the real object. The model has a low fit with the real object and lacks combined simulation of the probe and PCB. The difficulty of this simulation technology is mainly concentrated on the coupling interference between the PCB radiation emission and the probe magnetic flux in a certain frequency band.

[0005] The publication number is CN116611255A, and its name is A simulation method of electromagnetic pulse effects of electronic equipment based on field-circuit collaboration. Its design is to generate induced voltage on the chip by simulating the drastic changes in the electromagnetic field in the environment. However, its disadvantage is that this method only simulates the induced voltage generated by the PCB board when it is disturbed by the external electromagnetic field, and does not consider the impact of its own radiation emission on external components.

[0006] The publication number is CN112394255A, and its name is a test method for the electromagnetic radiation sensitivity of a PCB board. Its design uses HFSS to solve the current and voltage generated at a key pin on the PCB when it is interfered by an external electromagnetic field. However, its disadvantage is that it does not take into account the interference caused by the interference current and voltage at the pin entering the components directly connected to it.

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

[0008] The present invention provides an EMI simulation prediction method for an inductive conductivity sensor to overcome the above technical problems.

[0009] In order to achieve the above object, the technical solution of the present invention is:

[0010] A method for simulating and predicting EMI radiation from an inductive conductivity sensor, comprising the following steps:

[0011] S1: A 3D simulation model of the probe coil of the inductive conductivity sensor is established by using the 3D electromagnetic field simulation software Ansys HFSS, and the housing of the inductive conductivity sensor is simplified to obtain a sensor simulation model;

[0012] S2: Import the model file of the preset PCB printed circuit board 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 with 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 preset PCB printed circuit board model file is imported into the board-level electromagnetic simulation software Ansys Siwave to obtain the near-field radiation data of the PCB printed circuit board when it is working;

[0014] S3: Selecting several frequency points corresponding to a preset radiation threshold according to the near-field radiation data, and recording the radiation electric field value corresponding to each frequency point;

[0015] S4: The point radiation source position is set by the three-dimensional electromagnetic field simulation software Ansys HFSS to add the excitation source;

[0016] The frequency and field strength of the excitation source are the frequency point and the corresponding radiation electric field obtained in step S3;

[0017] S5: Based on the induced voltage prediction model of the probe coil output port, the predicted induced voltage is obtained according to the added excitation source;

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

[0019] Furthermore, the 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] And the 3D simulation model includes a coil conductor structure and a coil core structure;

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

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

[0024] S21: defining a model material of the sensor simulation model, and setting corresponding material parameters of the coil conductor, coil core, and housing based on the model material to obtain a model of a preset PCB printed circuit board;

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

[0026] And the basic structure data at least includes the stacking material and 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 an induced voltage prediction model for obtaining the output port of the probe coil;

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

[0029] Call the "Box" tool in the "Create" panel, and use the "Move" tool and the "Rotate" tool 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 connector of the PCB hard 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 “port” according to the preset key circuits, the scattering parameters S of the preset key circuits are obtained;

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

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

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

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

[0035] And through the "Generate Port on Selected Nets" tool in Ansys Siwave, according to the preset PCB printed circuit board model file in the "ODB++" format, the line ports of all lines of the PCB printed circuit board are obtained, and the ExtendedNet tool is called to select the line directly connected to the probe coil wire according to the line port, and the probe coil connection model is obtained;

[0036] S232: Setting the sweep range parameters;

[0037] 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 probe coil connection model is simulated with the "Launch" tool to obtain the scattering parameter S and the probe coil connection model after the scattering parameter simulation is defined as a Siwave model;

[0039] S233: Based on Ansys Siwave software and the working principle of the inductive conductivity sensor, build and obtain the sensor simulation schematic diagram according to the Siwave model file and the preset SPICE models of the crystal oscillator and rectifier diode;

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

[0041] S235: Name the simulation result file as “NearField Simulation 1”;

[0042] And according to the set sweep frequency range parameters, call the "Launch" tool to perform near-field radiation emission simulation to obtain the near-field radiation data of the PCB printed circuit board when it is working.

[0043] Further, in S3, several frequency points corresponding to the preset radiation threshold are selected according to the near-field radiation data, and the radiation electric field value corresponding to each frequency point is recorded, specifically:

[0044] Set preset radiation thresholds;

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

[0046] The relationship data is exported, and based on the "Export to Electronics desktop" tool, several frequency points whose radiation intensity meets the preset radiation threshold within the frequency sweep range are selected, and the radiation electric field value corresponding to each frequency point is recorded.

[0047] Furthermore, S4 sets the point radiation source position through the three-dimensional electromagnetic field simulation software Ansys HFSS to add the excitation source, specifically

[0048] Use the "Create a Point" tool to set the location where a point source can be placed to serve as a point radiation source location;

[0049] Call the "Excitations" tool and select the "Lumped Port" port. According to the property 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 intensity meets the preset radiation threshold, 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 model based on the output port of the probe coil obtains the predicted induced voltage according to the added excitation source, specifically:

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

[0052] Call the input formula in the Calculator function tool

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

[0054] Among them, Integrate is the integral function; Polyline1 is the straight line segment on which the integral function acts;

[0055] To obtain the integral of the electric field where the probe coil is located on the Polyline1 segment, and add it to the namedexpression to obtain the port induced voltage output by the probe coil.

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

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

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

[0059] S63: inputting the port induced voltage output by the probe coil as an input excitation into the operational amplifier chip circuit of the operational amplifier, detecting and acquiring the output voltage of the output port of the operational amplifier chip circuit, and acquiring the noise and interference signal after the port induced voltage output by the probe coil is amplified, so as to simulate the interference caused by the port induced voltage to the operational amplifier chip;

[0060] This can then realize the EMI simulation prediction of the inductive conductivity sensor radiation.

[0061] Beneficial effect: The present invention provides a simulation prediction method for radiated EMI of an inductive conductivity sensor, by establishing a simplified 3D model of the probe coil in electromagnetic simulation software, importing the same PCB board model in board-level electromagnetic simulation software and placing an equivalent excitation source on the PCB board to simulate the near-field radiation emission of the module, and measuring the induced voltage at the output port of the probe coil in the three-dimensional electromagnetic field simulation software, and extracting the induced voltage at the port as an equivalent source and adding it to the circuit simulation software to simulate the interference caused by the induced voltage and induced current to the operational amplifier chip. Not only does it solve the problem of coupling interference between the radiation emission of the PCB and the magnetic flux of the probe, but it also introduces the circuit simulation software to enable it to quickly obtain the influence of this radiation interference on the operational amplifier directly connected thereto, without spending a lot of time to build a hardware platform, and can provide convenient and efficient EMI radiation emission prediction in the early stage of circuit design. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0063] Figure 1 It is a flow chart of the simulation prediction method of EMI radiated by the inductive conductivity sensor of the present invention;

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

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

[0066] Figure 4 The circuit schematic diagram of the simulation software example circuit TI-TINA in this embodiment;

[0067] Figure 5 : is the interference voltage waveform at the output end of the operational amplifier chip in this embodiment. DETAILED DESCRIPTION

[0068] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

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

[0070] S1: The 3D simulation model of the probe coil of the inductive conductivity sensor is established by using the 3D electromagnetic field simulation software Ansys HFSS, and the shell of the inductive conductivity sensor is simplified to obtain the sensor simulation model, such as Figure 2 As shown;

[0071] The specific steps include:

[0072] S11: Establishing a 3D simulation model of the probe coil by using the three-dimensional electromagnetic field simulation software Ansys HFSS; and the 3D simulation model includes a coil wire structure and a coil core structure; Figure 2 As shown, 2 is the coil wire structure; 1 is the shell structure of the inductive conductivity sensor;

[0073] Among them, a 3D simulation model of the probe coil is 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] Helical coil radius: 0.01025 (m), ring radius: 0.0031819 (m)

[0079] Among them, X(_t) represents the coordinate of the curve in the X-axis direction, which changes with the change of _t; Y(_t) represents the coordinate of the curve in the Y-axis direction, which changes with the change of _t; Z(_t) represents the coordinate of the curve in the Z-axis direction, which changes with the change of _t; pi represents the pi, which is approximately equal to 3.14159; _t is a parameter, which represents the change of the curve over time or path progress, and is 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. Setup parameters involved in building a 3D simulation model of the probe coil

[0081]

[0082] After obtaining the conductor structure of the outer layer of the probe coil, it is also necessary to draw the coil core structure of the probe coil. Specifically, draw a cylinder with a diameter of 25mm and a height of 4.5mm with CenterPosition(0, 0, -2.25) as the center, set the direction of the cylinder to be parallel to the z-axis, and name it Cylinder_1; then draw a cylinder with a diameter of 16mm and a height of 4.5mm with Center Position(0, 0, -2.25) as the center, set the direction of the cylinder to be parallel to the z-axis, and name it Cylinder_2; finally, click "Edit" -> "Boolean" -> "Substract", use Cylinder_1 as Blank Parts, use Cylinder_2 as Tool Parts, and subtract Cylinder_2 from Cylinder_1 to obtain a circular iron 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, simplify the housing of the inductive conductivity sensor to obtain a 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, but considering that the connection structure is not regular and has little effect on the result, retaining it during modeling may increase a lot of unnecessary grids, which increases unnecessary calculations to a certain 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 with Center Position (0, 0, -3) as the center, set the direction of the cylinder to be parallel to the z-axis, and name it Cylinder_3. Then draw a cylinder with a diameter of 14mm and a height of 16mm with Center Position (0, 0, -3) as the center, set the direction of the cylinder 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, and you will get a shell structure with an outer diameter of 30mm, an inner diameter of 16mm, and a height of 16mm as shown below. Figure 1 Middle structure 1.

[0085] S2: Import the model file of the preset PCB printed circuit board 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 with 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 preset PCB printed circuit board model file is imported into the board-level electromagnetic simulation software Ansys Siwave to obtain the near-field radiation data of the PCB printed circuit board when it is working;

[0087] The specific steps include:

[0088] S21: defining a model material of the sensor simulation model, and setting corresponding material parameters of the coil conductor, coil core, and housing based on the model material to obtain a model of a preset PCB printed circuit board;

[0089] Define a material named Polyamide in HFSS, set its relative dielectric constant (εr) and loss tangent (tanδ) to εr=2.7 and loss tangent (tanδ) to 0.01 respectively;

[0090] Define another material in HFSS named Silicon Steel, set its material to Relative Permitivity of 12, Bulk conductivity of 0.5 siemens / m, Relative Permeability (μr): 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] And set the volume area attribute of the sensor simulation model, and set the volume area attribute to vacuum;

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

[0096] And the basic structure data at least includes the stacking material and thickness;

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

[0098] In Altium Designer, the drawn PCB board is exported in two forms. One is to export it in the form of STEP 3D file, and then the PCB board model file can be directly imported into HFSS; the other is to export the top, bottom and signal layers of the PCB board in ODB++ file format, and package them into a compressed package for importing the PCB board model into Siwave; the PCB board size involved in this embodiment is x (length) = 83.5mm, y (width) = 50mm, z (height) = 1.6mm;

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

[0100] Specifically, the PCB rigid circuit board is divided into three layers, namely, two copper foil layers, upper and lower layers, and a dielectric layer in the middle. The thickness of the copper foil layer is 35 μm, and the thickness of the dielectric layer is 1.53 mm. The copper foil layer is selected and its material property is set to Copper, and the middle dielectric layer 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 an induced voltage prediction model for obtaining the output port of the probe coil;

[0102] The probe coil of the sensor simulation model is connected to the PCB printed circuit board by using the "line" tool in the 3D Modeler panel of the 3D electromagnetic field simulation software Ansys HFSS to create a straight line, and setting 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 connector of the PCB hard circuit board; select the wire object, set the material properties in the "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 a port "port" according to the preset key circuit, to obtain the scattering parameter S of the preset key circuit; that is, importing the model file of the preset PCB printed circuit board into the board-level electromagnetic simulation software Ansys Siwave at the same time, and adding a port "port" to the preset key circuit of the preset PCB printed circuit board, to obtain the scattering parameter S of the preset key circuit;

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

[0106] S25: Based on the completed sensor simulation schematic diagram, the components of the preset PCB printed circuit board are imported into the SPICE model, and the preset excitation is input into the board-level electromagnetic simulation software Ansys Siwave for near-field radiation simulation to obtain the near-field radiation data of the PCB printed circuit board when it is working;

[0107] Since the high-frequency oscillation of the crystal oscillator during operation will cause the charge in the crystal to move back and forth, thus generating high-frequency electric and magnetic fields in space. These electromagnetic waves will propagate outward in the form of radio electromagnetic waves, forming electromagnetic radiation. In AC-DC circuits, rectifier diodes are usually used as switching elements; when the diode switches from the on state to the off state, or from the off state to the on state, the electric field and current inside it will change rapidly; this rapidly changing electric field and current will generate electromagnetic radiation;

[0108] The S23 specifically includes the following steps:

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

[0110] That is, through the Ansys Siwave software, click "import" and select the "ODB++" format, and import the model file of the preset PCB printed circuit board;

[0111] Select all the lines on the PCB, click "Generate Port on SelectedNets" to create the line port, and check the line directly connected to the probe coil wire in the ExtendedNet interface;

[0112] S232: Setting the sweep range parameters;

[0113] 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 probe coil connection model is simulated with the "Launch" tool to obtain the scattering parameter S and the probe coil connection model after the scattering parameter simulation is defined as a Siwave model;

[0115] That is, click "Simulation" -> "Compute SYZ Parameter" -> set the frequency sweep range, "Frequency Range Setup", "Start Freq" to 0hz, "Stop Freq" to 1Ghz, set the number of breakpoints to 1000, and Distribution to "Linear";

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

[0117] S233: Based on Ansys Siwave software and the working principle of the inductive conductivity sensor, according to the Siwave model file and the preset SPICE model of the crystal oscillator and the rectifier diode, build and obtain the sensor simulation schematic diagram; that is, after completing the simulation of the scattering parameter S in the Ansys Siwave software, import the Siwave model file into the "Circuit Design" 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 completed.

[0120] And the "Board_Siwave.siw" is the Siwave model file;

[0121] After importing the Siwave model file, import the SPICE model of the crystal oscillator and the rectifier diode into the three-dimensional electromagnetic field simulation software Ansys HFSS, and build the sensor simulation schematic diagram in Circuit Design according to the working principle of the inductive conductivity sensor;

[0122] S234: calling the "Project Manager" tool to set the step size Step and the simulation time in Analysis Control, and combining the Circuit Design tool to perform transient simulation of the inductive conductivity sensor to obtain a simulation result file; that is, setting the step size Step and the simulation time in Analysis Control through the "Project Manager", performing transient simulation of the inductive conductivity sensor through Circuit Design, and feeding back the results to the Ansys Siwave software;

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

[0124] In Simulation, click "Compute Near Field" to name the simulation result file "NearField Simulation 1", and set the frequency sweep range "Frequency Range Setup" to "Start Freq" of 0hz, "Stop Freq" of 1Ghz, the number of breakpoints of 1000, and Distribution of "Linear";

[0125] Click "Launch" to perform near-field radiation emission simulation to obtain the near-field radiation data of the PCB when it is working;

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

[0127] Set preset radiation thresholds;

[0128] Double-click "NearField Simulation 1" in the "Result" interface to obtain the relationship between the radiation intensity value and the frequency in "Max.Field.Plot";

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

[0130] S4: The point radiation source position is set by the three-dimensional electromagnetic field simulation software Ansys HFSS to add an excitation source; and the frequency and field strength of the excitation source are the frequency point and the corresponding radiation electric field 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 will be used as a point radiation source location;

[0132] Click "Excitations" and select "Assign"->"LumpedPort" port;

[0133] In the property window of the "LumpedPort" port, set the excitation signal frequency of the port to the frequency point where the near-field radiation intensity meets the preset radiation threshold, make sure 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 through the three-dimensional electromagnetic field simulation software Ansys HFSS. Specifically:

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

[0136] Click and select fileds -> input formula in Calculator Integrate(Line(Polyline1), Real(ScalarX(<Ex,Ey,Ez> ))); The principle is that the induced voltage U = Ex, where Integrate is the integral function; Polyline1 is the straight line segment on 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 the electric field E in the X-axis direction; Ex represents the component of the electric field E in the X-axis direction; Ey represents the component of the electric field E in the Y-axis direction; Ez represents the component of the electric field E in the Z-axis direction;

[0137] By obtaining the integral of the electric field on the Polyline1 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 a pre-built operational amplifier working 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] The specific steps include:

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

[0141] Specifically, the output end of the probe coil is directly connected to the input end of the operational amplifier OPA2134. Any noise and interference in the coil may be amplified by the operational amplifier. To simulate this process, it is necessary to build a circuit in the circuit software and conduct a simulation test; Figure 4 As shown, in this embodiment, the pre-built circuit TI-TINA is selected as the simulation software example circuit;

[0142] The operational amplifier OPA2134 is a chip developed by Texas Instruments. The SPICE model of the chip can be directly called in TI-TINA to build a circuit. The extracted induced voltage is input as input excitation into the working circuit of the operational amplifier chip. A probe is set at the output port to detect the output voltage to measure the amplified noise and interference signal.

[0143] S62: using the port induced voltage as an AC equivalent voltage source, and adding it to an operational amplifier working circuit constructed in the circuit simulation software;

[0144] S63: inputting the port induced voltage output by the probe coil as an input excitation into the operational amplifier chip circuit of the operational amplifier, detecting and acquiring the output voltage of the output port of the operational amplifier chip circuit, and acquiring the noise and interference signal after the port induced voltage output by the probe coil is amplified, so as to simulate the interference caused by the port induced voltage to the operational amplifier chip;

[0145] This can then realize the EMI simulation prediction of the inductive conductivity sensor radiation.

[0146] Specifically, in this embodiment, an AC equivalent voltage source 'voltage Generator' is placed at the input end 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 operational amplifier, such as Figure 5 As shown, Vout in the figure is the interference voltage waveform at the output end of the op amp.

[0147] Compared with the prior art, this embodiment provides a simulation prediction method for radiated EMI of an inductive conductivity sensor, which has the following beneficial effects:

[0148] This embodiment first establishes a simplified 3D model of the probe coil in the electromagnetic simulation software, then imports the same PCB board model in the board-level electromagnetic simulation software and places an equivalent excitation source on the PCB board to simulate the near-field radiation emission of the module, and finally measures and calculates the induced voltage at the output port of the probe coil in the three-dimensional electromagnetic field simulation software, extracts the induced voltage at the port, and then adds it to the circuit simulation software as an equivalent source to simulate the interference caused by the induced voltage and induced current to the operational amplifier chip. It can be seen that this method not only solves the problem of coupling interference between the radiation emission of the PCB and the probe magnetic flux, but also the introduction of the circuit simulation software enables this embodiment to quickly obtain the influence of this radiation interference on the operational amplifier directly connected thereto, without spending a lot of time to build a hardware platform, and can provide convenient and efficient EMI radiation emission prediction in the early stage 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, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 simulation prediction method for radiated EMI of an inductive conductivity sensor, characterized in that: The specific steps include: S1: A 3D simulation model of the probe coil of the inductive conductivity sensor is established by using the 3D electromagnetic field simulation software Ansys HFSS, and the housing of the inductive conductivity sensor is simplified to obtain a sensor simulation model; S2: Import the model file of the preset PCB printed circuit board 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 with 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 preset PCB printed circuit board model file is imported into the board-level electromagnetic simulation software Ansys Siwave to obtain the near-field radiation data of the PCB printed circuit board when it is working; S3: Selecting several frequency points corresponding to a preset radiation threshold according to the near-field radiation data, and recording the radiation electric field value corresponding to each frequency point; S4: The point radiation source position is set by the three-dimensional electromagnetic field simulation software Ansys HFSS to add the excitation source; The frequency and field strength of the excitation source are the frequency point and the corresponding radiation electric field obtained in step S3; S5: Based on the induced voltage prediction model of the probe coil output port, the predicted induced voltage is obtained according to the added excitation source; S6: Using the predicted induced voltage as an AC equivalent voltage source, and based on a pre-built operational amplifier working circuit, simulating and obtaining the interference caused by the induced voltage at the output port of the probe coil to the operational amplifier chip, thereby realizing EMI simulation prediction of the radiation of the inductive conductivity sensor.

2. The method for simulating and predicting EMI radiation of an inductive conductivity sensor according to claim 1, characterized in that: The 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; And the 3D simulation model includes a coil conductor structure and a coil core structure; S12: Based on the 3D simulation model, simplify the housing of the inductive conductivity sensor to obtain a sensor simulation model.

3. The method for simulating and predicting EMI radiation of an inductive conductivity sensor according to claim 2, characterized in that: The S2 specifically includes the following steps: S21: defining a model material of the sensor simulation model, and setting corresponding material parameters of the coil conductor, coil core, and housing based on the model material to obtain a model of a preset PCB printed circuit board; S22: Based on the three-dimensional electromagnetic field simulation software Ansys HFSS, the basic structure data of the PCB printed circuit board is set according to the preset PCB printed circuit board model; And the basic structure data at least includes the stacking material and 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 an induced voltage prediction model for obtaining the output port of the probe coil; The probe coil of the sensor simulation model is connected to the PCB printed circuit board by calling the "line" tool in the 3D Modeler in the three-dimensional electromagnetic field simulation software Ansys HFSS to create a straight line, and setting the type of the straight line to "Circle" to obtain the coil wire; Call the "Box" tool in the "Create" panel, and use the "Move" tool and the "Rotate" tool 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 connector of the PCB hard circuit board; S23: Using the board-level electromagnetic simulation software Ansys Siwave, based on the preset PCB printed circuit board model, add ports "port" according to the preset key circuits to obtain the scattering parameters S of the preset key circuits; S24: Call the Circuit design module, based on the working principle of the inductive conductivity sensor and the scattering parameter S, obtain the sensor simulation schematic diagram; S25: Based on the sensor simulation schematic diagram, the components of the preset PCB printed circuit board model are imported into the SPICE model, and based on the board-level electromagnetic simulation software Ansys Siwave, the preset PCB printed circuit board model imported into the SPICE model is simulated for near-field radiation according to preset excitations to obtain near-field radiation data of the PCB printed circuit board when it is working.

4. The method for simulating and predicting EMI radiation of an inductive conductivity sensor according to claim 3, characterized in that: The S23 specifically includes the following steps: S231: Convert the model file format of the preset PCB printed circuit board into "ODB++" format through Altium Designer software, and import it into Ansys Siwave; And through the "Generate Port on Selected Nets" tool in Ansys Siwave, according to the preset PCB printed circuit board model file in the "ODB++" format, the line ports of all lines of the PCB printed circuit board are obtained, and the Extended Net tool is called to select the line directly connected to the probe coil wire according to the line port, and the probe coil connection model is obtained; S232: Setting the sweep range parameters; 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 probe coil connection model is simulated with the "Launch" tool to obtain the scattering parameter S and the probe coil connection model after the scattering parameter simulation is defined as a Siwave model; S233: Based on Ansys Siwave software and the working principle of the inductive conductivity sensor, build and obtain the sensor simulation schematic diagram according to the Siwave model file and the preset SPICE models of the crystal oscillator and rectifier diode; S234: Call the "ProjectManager" tool to set the step size Step and simulation time in Analysis Control, and use the Circuit Design tool to perform transient simulation of the inductive conductivity sensor to obtain a simulation result file; S235: Name the simulation result file "NearField Simulation 1"; And according to the set frequency sweep range parameters, call the "Launch" tool to perform near-field radiation emission simulation to obtain the near-field radiation data of the PCB printed circuit board when it is working.

5. The method for simulating and predicting EMI radiation of an inductive conductivity sensor according to claim 4, characterized in that: In S3, several frequency points corresponding to the preset radiation threshold are selected according to the near-field radiation data, and the radiation electric field value corresponding to each frequency point is recorded, specifically: Set preset radiation thresholds; According to "NearField Simulation 1" in the "Result" interface, call the "Max.Field.Plot" tool to obtain the relationship data between the radiation intensity value and the frequency; Export the relationship data, and based on the "Export to Electronics desktop" tool, select several frequency points within the frequency sweep range whose radiation intensity meets the preset radiation threshold, and record the radiation electric field value corresponding to each frequency point.

6. The method for simulating and predicting EMI radiation from an inductive conductivity sensor according to claim 5, characterized in that: S4 sets the point radiation source position through the three-dimensional electromagnetic field simulation software Ansys HFSS to add the excitation source, specifically Use the "Create a Point" tool to set the location where a point source can be placed to serve as a point radiation source location; Call the "Excitations" tool to select the "LumpedPort" port, and according to the property 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 intensity meets the preset radiation threshold, 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 simulating and predicting EMI radiation from an inductive conductivity sensor according to claim 6, characterized in that: The induced voltage prediction model based on the output port of the probe coil in S5 obtains the predicted induced voltage according to the added excitation source, specifically: Set the probe position point, and set a straight line segment Polyline1 between the probe position point and the preset ground line; Call the input formula in the Calculator function tool Integrate(Line(Polyline1),Real(ScalarX(<Ex,Ey,Ez> ))); Among them, Integrate is the integral function; Polyline1 is the straight line segment on which the integral function acts; To obtain the integral of the electric field where the probe coil is located on the Polyline1 segment, and add it to the namedexpression to obtain the port induced voltage output by the probe coil.

8. The method for simulating and predicting EMI radiation from an inductive conductivity sensor according to claim 7, characterized in that: The S6 specifically comprises the following steps: S61: directly connect the output end of the probe coil to the input end of the operational amplifier; S62: using the port induced voltage as an AC equivalent voltage source in an operational amplifier working circuit constructed in circuit simulation software; S63: inputting the port induced voltage output by the probe coil as an input excitation into the operational amplifier chip circuit of the operational amplifier, detecting and acquiring the output voltage of the output port of the operational amplifier chip circuit, and acquiring the noise and interference signal after the port induced voltage output by the probe coil is amplified, so as to simulate the interference caused by the port induced voltage to the operational amplifier chip; This can then realize the EMI simulation prediction of the inductive conductivity sensor radiation.

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