Electrical and electronic components available in national instruments

Components

Components overview

Components comprise the basis for any schematic. A component is any part that can be placed onto theschematic. Multisim defines two broad categories of parts: real and virtual. It is important to understand the difference between theseparts, in order to fully utilize their advantages.

Real components can be differentiated from virtual parts because real components have a specific value thatcannot be changed, and a PCB footprint.

Virtual components are simulation-only components, which can be assigned user-defined characteristics. Forexample, a virtual resistor can take on any resistance (such as 3.86654 Ohms). Virtual components help designers to checkcalculations by simulating designs with precise component values. Virtual components can also be idealized components such as the4-pin Hex display shown in Figure 1.

Multisim also provides other classifications of components: analog, digital, mixed-mode, animated, interactive,multi-section digital, electromechanical, and radio-frequency (RF) components.

Interactive components

Multisim provides a method for interacting with certain components that are placed on the schematic. Changesto these components will affect the simulation results on-the-fly. Components are controlled by pressing the key listed beside thecomponent.

For the components shown in Figure 2 below, pressing the A keywill increase the resistance of the potentiometertoward 100% of the shown value (1kΩ); to decrease the resistance, hold the Shift key then press the A key. Pressing the Spacebar willtoggle the switch to be either closed or open.

The keyboard shortcut key can be changed by double-clicking on the component, and choosing the desired key fromthe drop-down box as shown below.

Component characteristics

The following fields are visible from the Component Browser.

The component browser

The Component Browser is used to select components for placement onto the schematic. To access theComponent Browser, click on any icon in the parts bin, or select Place/Component. The default keyboard shortcut to place a componentis Ctrl-W.Double-click on the desired component to place it on the schematic. The component will“ghost”the mouse cursor until the left mouse button is clicked again to place the component.

To search this view, simply start typing the name of the desired component, and the browser will automaticallydisplay matching candidate parts. Optionally, for a more detailed search, click on the Search button.

The Component Browser shows the current database in which the displayed parts are stored. Multisimorganizes the parts by group, and family. The browser also shows the symbol, a description of the component in the Function field,the model, and the footprint / manufacturer.

The wildcard character‘*’can be used to match any set of characters. For example“LM*78”would match components“LM*AD”would return both“LM101AD”and“LM108AD”, among others.

Note:Any component may have multiple models associated with it. Each model may account for varying physicalcharacteristics of the component. For example, the LM358M opamp has five visible pins, but only three of them are used in one model,ignoring the power supply terminals. More information about models can be found by selecting the desired model from the ModelManuf.\ID field, and click on the Model button.

Databases

There are three levels of database provided by Multisim:

• The Master Database is read-only, and contains components supplied by Electronics Workbench.
• The User Database is private to the individual user logged onto the computer. It is used for components built by an individualthat are not intended to be shared.
• The Corporate Database is used to store custom components that are intended to be shared across an organization. TheCorporate Database can be shared on a network.

Database management tools are supplied in order to move components between databases, merge databases, andedit them. All the databases are divided into groups and then into families within those groups. When a designer chooses a componentfrom the database and drops it onto the circuit, a copy of the component is placed onto the circuit. Any edits made to thecomponent in the circuit do not affect the original database copy.

Edits made to the component in the database do not affect the previously placed components, but will affect allsubsequently placed components of that type. When a circuit is saved, component information is saved in the Multisim file. Onload, the user has the option to keep the loaded parts as is, to make copies to place into their user or corporate database, or toupdate similarly-named components with the latest values from the database. Note: The Database Manager can be opened by selecting Tools/Database/Database Manager. To edit Master Database parts,copy them to the User or Corporate Database.

Creating custom components

Multisim includes the ability to create and edit components to satisfy the needs of any design. The two methodsavailable are the Component Wizard, and the Component Properties dialog box.

To access the Component Wizard, select Tools/Component Wizard. The component wizard allows designers toenter all pertinent component information, such as symbol, and SPICE model (Figure 7).

To access the Component Properties dialog box, double-click on a placed component, click on the Value tab, andclick the Edit Component in DB button (Figure 8).

More details on creating custom components are available in the helpfiles.