NI Circuit Design Community Blog
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bikeron
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Henry_Lavery
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Automotive Application: Hall Effect Sensor in Multisim
- GarretF on: LabVIEW-Multisim Co-Simulation with Variants and Hierarchical Blocks (Part 2)
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Control_Dir
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Adding 3D Information in Ultiboard
RLC components are a little different
Questions have come up a few times (1, 2) on the forums about how Multisim handles RLC components. These components are treated a little differently by the software, which is one part of the confusion. So, how exactly are RLC components treated by Multisim? Well, before I explain, I’ll expand on the category. It isn’t just resistors, capacitors and inductors that are a little different. You have to add the electrolytic capacitor, potentiometer, variable capacitor, and variable inductor to the list, but I’ll call them RLC’s for short since the others are really just special types.
Unlike most other components, RLCs are special in that the same functionality is available in a many different packages, with different tolerances, and different instance parameters. In the case of a resistor, the instance parameter is the resistance. The number of combinations is enormous – a search for “resistor” on Digikey showed over 250 000 different through hole and surface mount resistors. In recognition of this variety, Multisim treats RLCs a little differently from other types of components.
One way to understand how RLCs are different is to answer what does it mean to place a resistor on the schematic, and how is that different from placing another component such as an OpAmp. First off, you get a number of choices. In addition to the footprint, you specify the resistance, the type, and tolerance (the blue boxes). Multisim doesn’t restrict your choice. In Multisim, a resistor is the particular combination of these properties.
In the component browser, you see a list of common resistance values, and footprints that you can purchase. But where does this list come from, and more importantly can you add to this list? (I'll give a preview - you can add to the list.) But first, you can see this list in Multisim in the Database Manager on the RLC components tab (select Tools > Database > Database Manager).
So there's the list, and if you want to see new definitions in component browser (additional values, type, tolerance, or footprint), you need to edit this list. To add your own definition, click the Add button and create a new definition. Your choices will show in the Place Component dialog. Alternatively, you can check the Save unique component on placement button in the Place Component dialog and Multisim will create the definition automatically for you.
