Using A Phasor Diagram With NI Multisim Simulations

Overview

This example program is part of a series of LabVIEW based virtual instruments that can be used from inside Multisim.  All instruments are based on the virtual instruments templates you can find in your Multisim’s sample folder. There are two main categories of instruments:

1. Input Instrument; takes simulation data from your schematic and processes them in the virtual instrument (e.g. custom display, specific analysis, output to real world)
2. Output Instrument; inputs signals to a Multisim schematic to drive a simulation (e.g. acquire data from real world I/O, custom and arbitrary waveforms)

 

Note for using real world I/Os

Due to the nature of SPICE, all real world data that will be used to drive a circuit need to be acquired before a simulation is started. Data output to a real world device can be done while simulation is running, however continuous updates can’t happen in real-time, as SPICE simulations don’t have a real-time time-base.

 

Purpose Of This Instrument

Using the Multisim virtual instruments is key to success both when doing design validation, as well as teaching electronic circuit theory. Visualizing simulation data helps to reinforce understand of complex electric behavior easier and faster.

For certain applications, you may require a Multisim virtual instrument to identify various other design behavior. For example a designer or educator, you may wish to use a phasor diagram representation of AC voltage rather than a Bode plot. 

For this application, we have created a custom LabVIEW based instrument for use in Multisim. In this instrument the oscilloscope projects the phase measurements for visualization and analysis.

 

Installation Instruction

Unpack the archive to the Multisim installation directory. The table illustrates the files that will be copied to your computer.

 

Type	Name	Location	Application
Instrument	Phasor_Diagram.llb	...\Build	Multisim
Instrument	gettoneinformation.llb	Multisim	Multisim
Support	lvanlys.dll	...\Build\Phasor	Multisim
Example	Test Phasor Diagram.ms10	...	Multisim
Project	Phasor.lvproj	...	LabVIEW
Source	Phasor Diagram.llb	...	LabVIEW
Support	gettoneinformation.dll	...	LabVIEW

 

Instrument Features

The GPIB Terminal features tip strips for all controls. Hover with your mouse cursor over any of the controls and specific information will be displayed.

• There are two main controls to this Phasor Diagram
  • Sampling Rate [Hz] sets the frequency at which samples are taken from the simulation.
    • Decrease the value, if you like to run the Phasor diagram faster.
    • Default value is 10000 Hz
    • If your signal is undersampeled, amplitude/phase may not be measured correctly. To avoid undersampling, increase the sampling rate.
  • History Size set the number of points shown on the Y axes of the XY plot and the number of points used to calculate the magnitude and phase of the signal.
  • XY plot need to display at least one full period of the signal, to calculate the correct amplitude
• Right click on the controls to reinitialize to default value
• Control values will be saved with the circuit

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How To Use This Instrument

1. Open Multisim and create your circuit
2. Add the Phasor Diagram to your circuit
   1. Access the Phasor Diagram from the instruments toolbar
   2. Place it on your schematic
   3. Wire the desired input pins
3. Double click the instrument symbol to open the interface
4. Start the simulation
   1. Adjust Sampling Rate [Hz] and History Size if necessary

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Additional Resources

1. Search ni.com for more LabVIEW based instruments for NI Multisim
2. Tutorial on how to create a LabVIEW based instrument for NI Multisim"
3. Tutorial on assuring compatibility of LabVIEW based Instruments across different NI Multisim versions

 

Note: You only require NI LabVIEW to create or edit an instrument. NI LabVIEW does not need to be installed on the machine where you intend to run Multisim.

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