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Automate Circuits Analyses with the NI LabVIEW Multisim API Toolkit

Publish Date: Oct 07, 2013

Overview

The NI LabVIEW Multisim API Toolkit has been developed for the LabVIEW environment and provides access to more than 120 funct ions 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:

• Access simulated measurements within the LabVIEW environment for further, domain specific analysis

• Correlate simulated and real measurements in a single LabVIEW environment

• Use simulated measurements as a design under test (DUT), in order to build test/validate cases earlier in the design flow

Table of Contents

1. Introduction

2. What is the LabVIEW Multisim API Toolkit?

3. How to Install the LabVIEW Multisim API Toolkit

4. Example 1: Efficiency Calculation of a Buck Converter

5. Example 2: Automating a Simulation of a Signal Conditioning Circuit with Acquired Heart-Beat Signal

6. Additional Resources

1 . Introduction

Multisim allows engineers to use simulation to optimize the performance of designs earlier in the design flow and ensure circuits meet specifications with fewer prototype iterations. The LabVIEW Multisim API toolkit added in Multisim 13.0 enables designers of analog and mixed-mode circuits to easily create graphical program in LabVIEW that rapidly perform or automate critical design tasks which is impossible in other simulation tools. Some of the critical types of analyses that are available include:

Ev aluating circuit performance with non-ideal signals from real measurements

Visualizing outputs of circuits in custom graphs and interfaces

Automating and iterating through different design scenarios with LabVIEW

2 . 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 the connection status, disconnect from Multisim, query the application location and version.

2. Manage Multisim files (open, create and save files, as well as query file information).

3. Conf igure inputs and outputs, as well as also set data for inputs or get data from outputs.

4. Control and check the state of the simulation (DC, AC, or Transient).

5. Execute analyses and use the SPICE command line.

6. Conf igure component values, switch models, change circuit parameters, and replace variants of a Multisim circuit.

7. Perf orm different utility functions.

8. Check for error messages, get a circuit image or generate reports.

3 . How to Install the LabVIEW Multisim API Toolkit

The LabVIEW Multisim API Toolkit is installed automatically with Multisim 13

4 . Example 1: Efficiency Calculation of a Buck Conv erter

This example uses theLabVIEW Multisim API Toolkit to iterate through multiple critical values in a circuit in an automated fashion to assist us in calculating efficiency. Without a toolkit such as this one in LabVIEW an individual would try to optimize efficiency by manually changing values in a circuit and recording the simulated value in each. This is time consuming and error-prone.

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Our goal f or this example will therefore be to set the switching frequency of parameters on a buck converter based on NXP components and then perform a sweep across several switching f requency, Fsw, values. For each step a transient analysis is run and the efficiency of the circuit is automatically calculated. This can all then be plotted and the best switching frequency will be observ ed through this process. Using the circuit parameters (click here to learn more about circuit parameters) and toolkit we can step through the development of this test.

All the example files are attached to this document in the folder called apidemo.zip

Open the f ile Circuit Parameters.vi in LabVIEW 2013

Go to the block diagram and see the new VIs for the Multisim connectivity. They are under Connectivity>Multisim

Notice how f rom LabVIEW there are now ready to use VIs for establishing a Multisim connection, running simulation files, configuring circuits, and read/write IOs.

On the block diagram there are available explanations on what each of the VIs accomplishes.

Open the Multisim circuit that this VI is supposed to control and notice the DC-DC buck circuit converting 10V to 3.1V (BuckConverter_API.ms13).

Run a quick interactive simulation by pressing the play button to evaluate the circuit operation. The probes should be showing the expected values.

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Go to the LabVIEW front panel and run the VI

LabVIEW is now controlling Multisim and iterating over multiple values of the switching frequency and creating a plot of the circuit efficiency

By using this approach we can clearly see the various efficiency values of our circuit. The best option can be chosen and we have been able to automate what has traditionally been a complex and error-heavy process

5 . Example 2: Automating a Simulation of a Signal Conditioning Circuit with Acquired Heart-Beat Signal

In this example a signal conditioning circuit is designed in Multisim to filter acquired heartbeat signals for the development of a biomedical device application.

The circuit is a single stage active filter using operational amplifiers from Texas Instruments. While the heart beat signals are real-world signals that could be acquired using a sensor device or simulated using the LabVIEW Biomedical Toolkit.

All the design f iles of this example are in the attached file sigcond.rar

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As y ou can see the transient simulation in Multisim could be used to evaluate whether the chosen op-amp will provide the desired filtering response or not for this low-voltage signal. However,

f or

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As y ou can see using this automation code multiple output plots for different op-amps and input signals have been very easily created. Also the table on top of the graph indicates the different corresponding SNR values. Without the automation of LabVIEW this toolkit provides, such calculation would a separate simulation run for each case which is a lengthy process.

6 . Additional Resources

Download Multisim

Learn about more Multisim circuit design applications

the purpose of this design, the LabVIEW Multisim API Toolkit is leveraged to automate multiple simulation runs that:

Iterate over a various selection of op-amp to determine which op-amp provide better conditioning

Iterate over various input heart-beat signals with various noise levels

Calculate the transient responses for each op-amp versus multiple input noise levels

Perf orm advanced signal processing tasks to calculate critical parameters such as the Signal to Noise Ratio (SNR)

The application below is written in LabVIEW. You can simply download and run under the project . main.vi Heart Beat Signal Conditioning.lvproj