Automate Student Assessment Using the NI LabVIEW Multisim API Toolkit

[ExamplePrograms]

Overview

The NI LabVIEW Multisim API Toolkit has been developed for the LabVIEW environment and provides access to more than 120 functions to automate the simulation of a Multisim circuit from LabVIEW. This toolkit is an innovative new connection between the worlds of design and graphical programming. You can for automate simulations easily from a graphical programming language, to do a number of tasks. One of the most innovative tasks that can be automated by the LabVIEW Multisim API Toolkit is for an educator to mark student circuit files as correct or incorrect in a rapid manner.

Introduction

Multisim allows educators and engineers to use and simulation to teach fundamental topics to students in analog, digital and power electronics. With the LabVIEW Multisim API toolkit added in Multisim 13.0 educators can also automate simulation in the LabVIEW environment. This means that applications can be developed that can use Multisim as a source of measurement data. LabVIEW can then be used to acquire, analyze, correlate and present simulated measurements in custom interfaces.

In this tutorial we will learn how to use this capability to take multiple circuits (for example circuit homework completed by students) and compare the output to the solution (as defined by the professor). The automated assessment application will then grade the circuits as incorrect or correct based upon this API toolkit.

What is the LabVIEW Multisim API Toolkit?

Multisim natively provides an Application Programming Interface (API) that allows for the automation of circuit simulation and analyses through a COM interface that designers can use to programmatically control.

The LabVIEW Multisim API Toolkit is a collection of VIs that makes the Multisim API ready-to-use for LabVIEW users. With this API toolkit users can take advantage of over 120 ready-to-use LabVIEW Virtual Instruments (VIs) to:

1. Establish a connection to Multisim, check connection status, disconnect from Multisim, query the application location and version number of Multisim.
2. Manage Multisim files (open, create and save files, as well as query file information).
3. Configure inputs and outputs, as well as  set data for inputs or acquire datafor output.
4. Control and check the state of the simulation (DC, AC, or Transient).
5. Execute analyses and use the SPICE command line.
6. Configure component values, switch models, change circuit parameters, and replace variants of a Multisim circuit.
7. Perform different utility functions.
8. Check for error messages, get a circuit image or generate reports.

How to Install the LabVIEW Multisim API Toolkit

The LabVIEW Multisim API Toolkit is installed automatically with Multisim 13.0.

Automated Student Assessment 

In this fairly simple example we are able to automate a common educator task thanks to NI Multisim, NI LabVIEW and the NI LabVIEW Multisim API Toolkit. Student homework (in the form of Multisim circuit files) have been developed (simple RLC circuit). They are then compared to the professors solution (the correct circuit). 

The output response of each of the students circuits is compared to the professors solution to see if the student was able to calculate and simulate the correct solution.

Based upon the output a mark is assigned of "pass" or "no pass". The application automates this task for multiple circuits to help speed through this common task.

In this example, the application is fairly simple, however it can be modified by educators or students to be able to be more specific and add additional functionality to this assessment process.

Running the Automated Assessment Application

In order to run this application you must:

1. Install NI LabVIEW 2013
2. Install NI Multisim 2013. It is critical that when installing Multisim that you also install the LabVIEW Multisim API Toolkit during the installation process. This is not a default option.
3. Download the attached "Homework Grader.zip" file
4. Unzip the attachment
5. Double-click and run the Homework Grader.lvproj LabVIEW project file

This application will now compare the \\Homework Grader\Files\Professor.ms13 file to the various student files in \\Homework Grader\Files\Students\

The grade is based on at least 0.8 of a correlation coefficient between the professor's circuit transient analysis and the student's circuit transient analysis.

After the files have been analysed, you may select any row in the table representing each student's file and it will be compared in the graph against the professor's plot.

When finished, click EXIT to terminate this VI.

In the following image you can see the professor solution of the circuit.

Next you will see the LabVIEW application along with the code that has been developed using the LabVIEW Multisim API Toolkit. Let us begin by seeing the block diagram and then view the user interface after it has been run.

The user interface as you can see shows the selection of the "professor" file. All of the various student files are presented below with a green mark if their results passed, or red if they failed.

By selecting student 11 we can see the correlation between the professors circuit and students circuit to be almost exact. The student has passed. In the case of student 5 we see that the student has failed.

This code is fully available to a professor (or student) to be able to make their own application based upon Multisim, LabVIEW and LabVIEW Multisim API Toolkit.