Multisim is a state-of-the-art electronic circuit simulation software that provides a virtual laboratory that includes measuring instruments and extensive libraries electronic components. This article will consider such stages of creating an electrical circuit diagram in the Multisim 12.0 environment, such as connecting component symbols on a diagram, naming circuits, working with a voltage probe indicator.
Connecting Component Symbols on a Diagram
Circuits and buses are used to communicate between components in a circuit. To add a circuit to the circuit, use the “Explorer” command from the “Insert” menu, to add a bus, use the “Bus” command. After selecting the required command from the menu, the cursor will take the form of a cross. In Multisim, connecting component symbols on a schematic using a net can be done in several ways:
- automatic connection;
- abutment connection;
- manual connection.
In order to use a circuit to connect the contacts of the symbols, you need to move the cursor to the selected contact and click on it with the left mouse button, then drag the cursor to the next contact and also click on it with the left mouse button - the circuit is created. In the process of creating a circuit, it may be necessary to connect a symbol pin to a net. In this case, after moving the cursor to the selected contact to which the circuit will be connected, you need to left-click on it and drag the cursor to the connection point with another circuit, then also click in this place with the left mouse button - the system will create a node in the place joining the chain being created with an existing one. Such a connection is called automatic. There is another way of laying circuits - this is the connection of the contacts of the symbols by adjunction. To implement this method, move the connected symbol so that the end of its input contact coincides with the end of the output contact of the symbol of the component to which you are connecting (in this case, a small dot should appear at the connection point, symbolizing that the contacts have successfully docked) and click the left mouse button to place it on the schematic, then drag the symbol to the desired location on the schematic (this will place the net behind the symbol). An example of automatic connection of a component symbol and a conductor is shown in Figure 1.
Rice. 1. Automatic connection of component symbol and conductor.
The sequence of actions in this example is divided into five steps:
- In the first step, the figure shows two symbols already connected by a conductor.
- Step 2 demonstrates how to add a new symbol to the drawing area.
- At the third step, the new symbol is moved to contact with the conductor. In this case, the connection with the conductor is made automatically after left button the mouse is released.
- Select the symbol with the left mouse button and move it to a new location.
Figure 2 shows an example of joining two component symbols by adjacency.
Rice. 2. Connecting the contacts of two component symbols by adjoining.
The sequence of actions in this example is presented in the form of four steps:
- At the first step, the figure shows two component symbols placed in the working area of the drawing.
- In the second step, the second character is moved to contact with the first character. At the same time, a colored dot appears at the junction, symbolizing that the docking of the contacts of the symbols was successful. After the left mouse button is released, the connection is made automatically.
- Move the second component symbol to a new location in the drawing.
- The conductor was laid behind the symbol.
To connect the contacts of two component symbols manually using a circuit, select the “Explorer” item in the “Insert” menu, left-click on the output of the first symbol (the cursor will look like a cross). Drag the cursor towards the next pin, and a wire will appear attached to the cursor. When moving the mouse, control the direction of the connection by clicking the left mouse button at the change points of the connection route. In this case, each click of the left mouse button attaches the conductor to the laid points. Figure 3 shows a manual way of connecting component symbol pins.
Rice. 3. Manual connection of component symbol pins.
When using this connection method, the routed conductor automatically bypasses the symbols of components with which there is no connection (Fig. 4).
Rice. 4. The explorer automatically bypasses the symbols of components with which there is no connection.
The manual method of connecting component symbol pins is recommended for difficult, critical wire paths, as it is more complex. You can also use a combined connection - automatic and manual in one scheme.
For more flexibility in the Multisim connection process, you can start and end a connection in the air, that is, without attaching a wire to a component symbol pin, or starting from a previously established connection point. To place a conductor in the air, select the "Explorer" item from the "Insert" menu, left-click in the drawing area (this action will create the starting point of the connection), move the cursor to lay the conductor, then double-click the left click in the drawing area to complete the wire routing (this action will create the end point of the connection). In some cases, it may be necessary to modify the connection route in the schema. In order to change the location of the conductor, select it with the left mouse button (in this case, several "drag" points will appear on the conductor), left-click on one of them and drag the connection with the mouse, changing its route. Drag points can be added or removed. To do this, press the Ctrl key on the keyboard and left-click on the conductor at the place where you want to add or remove the "drag" point. You can also change the connection route by moving the wire segment. To do this, select the conductor with the left mouse button, place the cursor over the conductor segment (in this case, the cursor will take the form of a double arrow), left-click on the segment and move it with the mouse, changing the connection route.
The color of the conductors in the diagram can be changed. To change the color of a wire or the color of a wire segment, click right click mouse on the conductor and in the context menu that opens, select the "Net color" or "Segment color" item. In the "Palette" window that opens, select the desired color and click the "OK" button. As a result, the conductor on the diagram will be displayed in a new color.
Where multiple circuits follow a common path, busbars are used. A busbar groups nets together, making the diagram easier to read. To add a bus to the circuit, use the "Bus" command from the "Insert" menu.
Circuit naming.
To improve the readability of the diagram, each net in the diagram can be given a name. To name the circuit circuits, double-click on the conductor with the left mouse button, as a result of which the "Circuit Settings" window will open. By default, each circuit is assigned an autoname when it is created, which is displayed in the Circuit Name field on the Circuit tab. A new circuit name can be entered in the Preferred Circuit Name field. The visibility of the circuit name on the diagram is set by checking the box in the "Show name" checkbox. You can also change the color of the chain on the "Chain" tab. This can be done by selecting the desired color in the "Palette" window. This window is called by clicking on the colored icon in the "Chain color" field. In order for the changes made on the “Chain” tab to take effect, click on the “Apply” or “OK” button. Figure 5 shows a circuit with a name assigned to it, as well as the "Chain Settings" window.
Rice. 5. A circuit with a name assigned to it, as well as the "Chain settings" window.
Application of a voltage probe-indicator.
On the toolbar "Virtual measuring components" (this panel can be added to the project using the menu command "View / Toolbar") there are icons of five colored voltage probes: colorless, blue, green, red, yellow. The principle of operation of these indicators is the same, the difference is only in color. The voltage indicator probe determines the voltage at a particular point in the circuit, and if the point under study has a voltage equal to or greater than the response voltage value, which is specified in the settings of this probe indicator, then the indicator lights up in color. You can set the required threshold value for the operation of the indicator probe in the settings window of this device on the "Parameters" tab by setting the required voltage value in the "Threshold voltage (VT)" field. For the changes to take effect, click on the “OK” button. The settings window can be opened by double-clicking the left mouse button on the icon of this device in the diagram. The name of the settings window corresponds to the name of the color of the custom indicator probe. For example, for a green indicator probe, the settings window will be called "PROBE_GREEN", and for a yellow one - "PROBE_YELLOW". In the diagram, the threshold voltage of the probe-indicator is displayed next to its icon. Figure 6 shows an example of connecting several indicator probes to the circuit under study, as well as the green probe settings window.
Rice. 6. An example of connecting several indicator probes to the circuit under study, as well as the green probe settings window.
For example, consider an amplifying stage on a bipolar transistor - included in a circuit with a common emitter. We will build graphs of dependence of the output and input voltage from time, transfer characteristic, amplitude-frequency and phase-frequency characteristics.
1) Let's assemble the circuit under study in the Multisim environment
Note:
-double-clicking on an element with the left mouse button allows you to change its parameters
-for convenience during work, you can change the color of the wires (select the wire with the right mouse button and select Change Color in the context menu that appears)
2) We start the circuit, the oscilloscope automatically plots the dependence of the input and output voltages on time (in order to see them, just left-click on the oscilloscope).
In the active window of the Oscilloscope-XSC1, you can zoom in and out, shift graphs along the ordinate and abscissa axes, use the cursor to view the parameters at each point of the graph (here, the voltage value), using the Save button, you can save the oscilloscope data as a table in a text file .
3) Construction of similar graphs using Transient Analysis.
Using the plotter button display cursors and data, you can see the voltage value at any point. When analyzing graphics for convenience, they are displayed in different colors.
In the Transient Analysis window, on the Output tab, select the values necessary for analysis, and on the Analysis Parameters tab, you can set the start and end times of the analysis (the same actions are performed in any type of analysis).
4) Building transfer characteristic(output voltage versus input voltage) using DC-Sweep Analysis. Work in the plotter (Grapher View) with the graph is carried out in a similar way.
5) Construction of frequency response and phase response (using AC-Analysis).
Multisim's intuitive schematic editor allows you to spend more time designing by saving time on drawing. Multisim is built in such a way that there is no need to switch from the placement mode to the layout mode, as in other similar programs. Multisim comes to the customer with a complete base of 16,000 parts and includes a simulation model, a schematic symbol, electrical parameters, and a layout for wiring. Also available free access to the Design Center, which has over 12 million parts in a searchable database.
Classic circuit simulation programs or SPICE-like programs (where SPICE is English - Simulation Program with Built-in Circuit Expression) have the maximum accuracy and reliability, which include Multisim. The principle of their operation is based on the machine compilation of a system of ordinary differential equations electrical circuit and their solution without applying simplifying assumptions. It uses numerical Runge-Kutta methods or the Geer method to integrate a system of differential equations, the Newton-Raphson method to linearize a system of nonlinear algebraic equations, and the Gauss method or LU-expansion to solve a system of linear algebraic equations. Modifications of these methods aim to improve convergence or computational efficiency without simplifying the original problem.
Multisim uses the following SPICE simulation features: Industry standard SPICE simulation; XSPICE amplification to expand Berkeley SPICE3 capabilities; simulation with VHDL and Verilog connection; interactive modeling; a wide range of sources, including DC, sine, pulse, sawtooth, random, AM, FM; software modeling; mixed analog-digital simulation; modern algorithms to solve problems of crossed circuits, advanced options to get a speed/accuracy trade-off. RF Simulation Features: SPICE gain for high frequency simulation; RF tools and analyses, RF models and a wizard to create your own models.
Multisim is the only general purpose simulation package for use with frequencies above 100 MHz, where SPICE usually becomes inoperable. The Multisim RF suite includes a dedicated parts library, an RF model wizard, RF virtual instruments, and RF analyzers. The VHDL and Verilog functions are an easy way for beginners to use HDLs, which is a tool for modeling complex digital details that cannot be modeled in SPICE. VHDL and Verilog - the ability to model parts without having to understand HDL syntax. VHDL and Verilog - standalone design tool with code editors, simulation project managers, waveform output and debugging, co-simulation with SPICE, full standards compliance.
Multisim allows a team of designers to work on identical circuits in real time via local network or the Internet. WITH using Multisim you can enter special fields to characterize parts, such as cost, delivery time, or preferred supplier.
The combination of Multisim and virtual instrument technology allows circuit board design engineers and electrical engineering educators to achieve a seamless three-step design cycle: theory, simulation, prototype, and test.
Multisim 10.0 and Ultiboard 10.0 have a large number of features for professional design, focused on the most modern facilities modeling, an improved component database, and an expanded user community. The component database includes over 1200 new items and over 500 new SPICE models from leading manufacturers such as Analog Devices, Linear Technology and Texas Instruments, as well as over 100 new models of switching power supplies.
In addition, in new version software the Convergence Assistant was introduced to automatically correct SPICE parameters to correct simulation errors, support for BSIM 4 standards was added, and data display and analysis capabilities were expanded, including a new current probe and updated static probes for differential measurements.
Department of Radio Electronics
T.V. Gordyaskina, S.V. Lebedev
Modeling of radio circuits and signals in the software environment Multisim
Training manual for implementation
laboratory work and course project
for full-time students in the specialty
160905 "Technical operation of transport
radio equipment"
Publishing house FGOU VPO "VGAVT"
N. Novgorod, 2010
UDC 519.876.5
Gordyaskina Tatyana Vyacheslavovna, Lebedeva Svetlana Vladimirovna
Modeling of radio circuits and signals in the software environment Multisim: Educational and methodological manual for the implementation of laboratory work and a course project for full-time students in the specialty 160905 "Technical operation of transport radio equipment." - Nizhny Novgorod: Publishing house of FGOU VPO "VGAVT", 2010. - 62 p.
The teaching aid describes the methodology for performing laboratory work and a course project in the discipline "Radio circuits and signals" using the Multisim software package.
Minutes No. 9 dated May 28, 2010
© FGOU VPO VGAVT, 2010
Brief theoretical information
Multisim is an interactive circuit emulator that allows you to design devices in minimal time. Multisim includes a version of Multicap, making it ideal for programmatic description and immediate post-testing of circuits. Multisim also interfaces with National Instruments' LabVIEW and Signal Express for tight integration of development and test tools.
The Multisim package uses the standard Windows interface. The intuitiveness and simplicity of the interface makes it much easier to use.
Multisim provides the ability to design a circuit and test/emulate it from the same development environment.
In addition to traditional SPICE analysis, Multisim will allow users to connect virtual instruments to the circuit. It's simple and fast way see the result by simulating real events.
When more complex analysis is required, Multisim provides various analysis functions. Multisim includes Grapher, a powerful tool for viewing and analyzing emulation data.
The ability to change the color of the conductors allows you to make the circuit more convenient for perception. You can display different colors and graphics, which is very convenient when exploring several dependencies at the same time.
Fundamentals of working in the Multisim software package
The user interface consists of several main elements, which are shown in Fig. 1.
In the development window (Design Toolbox) there are controls for various elements of the circuit.
Global settings(Figure 2) control the properties of the Multisim environment. They are accessed from the dialog box. Properties (Preferences). Select an item Options / Global Preferences (Options / Global Preferences), a window will open Properties with the following tabs:
Paths– specifies the path to the database files and other settings;
Parts (Components) - selection of the component placement mode and symbol standard (ANSI or DIN);
ANSI or DIN - default emulation settings;
General (General)–Change the behavior of the selection rectangle, mouse wheel, and join and auto join tools.
Component overview
Components are the basis of any circuit, these are all the elements of which it consists, Multisim operates with two categories of components: real (real) and virtual (virtual). Real components, unlike virtual ones, have a specific, unchanging value and their correspondence on the printed circuit board. Virtual components are needed only for emulation, the user can assign arbitrary parameters to them.
Multisim has another classification of components: analog, digital, mixed, animated, interactive (components are controlled using the keys listed under each item), multi-select digital, electromechanical, and RF.
The components panel contains fields sources (place source), basic elements (place basic), diodes (place diode), transistors (place transistor), analog (place analog), indicators (place indicator) and etc.
Component Browser is where components are selected to be placed on the schematic. After double-clicking the mouse, the cursor will take the form of a component while a location on the schematic for the component is selected.
IN component explorer displays the current database in which the displayed items are stored. In Multisim they are organized in groups And families. The explorer also displays a description of the component (field Purpose Function), model and printed circuit board or manufacturer.
In the group of sources, you can select sources of direct and alternating voltage, current, power; dependent sources (for example, voltage and current sources controlled by current or voltage), etc.
In the group of basic elements, switches, transformers, connectors, relays, fixed and variable resistors, capacitors, inductors and other elements are selected.
The group of indicators contains probes, digital indicators, incandescent lamps, voltmeters and ammeters.
After selecting components from the database, they are placed on the diagram and connected to each other. At this time and after installation, the components can be rotated. To select a component, simply click on it with the mouse. To select multiple components, hold down the mouse button and drag to draw a selection box around the desired components. Selected components are indicated by a dotted line.
Components can be replaced by others using their context menu, point Replace Component(s). New components are selected in the additional component explorer window that opens. Multisim will restore component connections after replacement.
Click on the connector to start guiding the connecting wire, click on the end pin to complete the connection. When the explorer appears, Multisim will automatically assign it a number on the network. The numbers increase sequentially, starting at 1. Ground wires are always numbered 0 - this requirement is due to the operation of the hidden SPICE emulator. To change the connection number or give it a logical name, you must double-click on the conductor and enter a new value.
Devices
Virtual Instruments are multisim model components that correspond to real instruments. For example, the VIs in Multisim include oscilloscopes, signal generators, spectrum analyzers, and more.
To add a VI, select it from the panel devices (Instruments), rice. 4. To view the instrument's front panel, double-click the instrument's icon. The device leads are connected to circuit elements in the same way as other components.
Multisim also includes simulated real-life instruments from Agilent and Tektronix.
1.2.1.Signal generator
The XFG1 is an ideal voltage source producing sine, square or triangular waveforms.
The middle terminal of the generator, when connected to the circuit, provides a common point for reading the amplitude of the alternating voltage. To read the voltage relative to zero, the common terminal is grounded. The extreme right and left terminals are used to supply alternating voltage to the circuit. The voltage on the right pin changes in a positive direction relative to the common pin, the voltage on the left pin changes in a negative direction.
Double-clicking on the reduced image opens the enlarged image of the generator (Fig. 5).
1.2.2.Oscilloscope
The XSC1 oscilloscope is an analogue of a dual-beam storage oscilloscope. You can connect the oscilloscope to an already turned on circuit or rearrange the leads to other points while the circuit is running - the image on the oscilloscope screen will change automatically.
You can stop the process of calculating the parameters and characteristics of the circuit at any time by pressing the F9 key or by selecting the item Pause on the menu Circuit. You can continue the calculation by pressing the F9 key again or by selecting the item Summary menu Circuit. By pressing the "Start-Stop" button in the upper corner of the screen, the calculation of the circuit parameters starts or stops.
A reduced image of the oscilloscope is displayed on the diagram. There are four input terminals in this image: the upper right terminal is common; bottom right - synchronization input; the left and right bottom clips are respectively channel A input (channel A) And channel B input (channel B).
Double-clicking on the thumbnail image opens the front panel image of the oscilloscope (Fig. 6).
Directly below the screen is a scroll bar that allows you to observe any time period of the process from the moment the circuit is turned on to the moment the circuit is turned off.
There are two cursors on the oscilloscope screen, designated 1 and 2, with which you can measure the instantaneous voltage values at any point on the oscillogram. To do this, simply move the mouse over the triangles in their upper part to the required position. The coordinates of the points of intersection of the first cursor with the waveform are displayed in the top line, the coordinates of the second cursor - in the middle line. The bottom line displays the values of the differences between the corresponding coordinates of the first and second cursors. The results can be written to a file. To print the received oscillograms, it is convenient to get an image on a white background by pressing the button.
1.2.3. Spectrum Analyzer XSA1
Spectrum analyzer XSA1, designed to determine the signal spectrum at any point radio circuit. You can connect the spectrum analyzer to an already switched on circuit or rearrange the leads to other points while the circuit is running - the image on the spectrum analyzer screen will change automatically.
On fig. Figure 7 shows the front panel of the spectrum analyzer showing the amplitude spectrum of the positive harmonic signal S(t)=1+Sin(2p1000t).
To correctly display the spectrum, you must select a frequency range by setting the initial value of the range in the Start window, the final value in the End field, save the settings by pressing Enter. By moving the marker, at the bottom of the working window we get the values of the frequency and amplitude of the selected harmonic.
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