Transient analysis frequency estimate

Hi,
I have a simple analog tone generator that produces a sine wave after some short startup delay. Is there a function in Multisim that would allow me to take my transient analysis data and estimate the frequency of oscillation? What I'm looking for is similar to the frequency counter available in the runtime tools.
Specifically, I need to generate a table of results from a Monte carlo transient analysis. Currently, I'm forced to export the 200 or so MC time series and perform an FFT in MATLAB on each series.
I'm not looking for a monte carlo Fourier analysis, because I need much better resolution than this tool provides. Is there something I can do with the post processor to extract a frequency estimate?
-J

Hi Jay,
In Multisim, you can use the probe or frequency counter to read signal frequency, but once you use any of the analysis such as transient, the option to find frequency is not available.
What you can do is use LabVIEW to control Multisim and there is a pre-built function available that can calculate a signal frequency. To make this work, you need LabVIEW and the LabVIEW Multisim API Toolkit which can be downloaded from the links below:
https://lumen.ni.com/nicif/us/evalmultisimtlkt/content.xhtml
https://lumen.ni.com/nicif/us/evaltlktembdes/content.xhtml
Once you install the required software, in LabVIEW you can create a VI (a program) to launch Multisim, run a circuit 200 times and each time change component values and calculate the output frequency for each run.
Attached is a sample circuit and the VI I created. Double click on the Reading Signal Frequency.vi file, click on the folder in the front panel (the screen with the grey background) and select and select the Multisim circuit which is attached. In this program, I am changing a resistor R1 in the Multisim circuit and run the simulation 10 times, once finished, the result will appear in the array in the front panel.
You can use this example and modify the VI for your circuit.
Tien P.
National Instruments
Attachments:
PhaseShiftOscillator_a.ms12 ‏98 KB
Reading signal Frequency.vi ‏69 KB

Similar Messages

RLC circuit AC simulation result does not match transient analysis result at resonant frequency!

Hi,
It is a very basic series RLC circuit. (R=0.1 Ohm, L=10mH, C=100nF) which is excited by a sine wave voltage source (100mV peak, 5032 Hz).
AC analysis is in-line with hand calculations and shows a peak current of 1A at 5032.9 Hz. Once we do a transient analysis at this frequency, the current is way lower; instead if we change the frequency down to 4968 Hz, it gives the maximum current (appx. 1A). Note that all the components are ideal and both amplitudes of the voltage source set at 100mV. I must be missing something very basic.
The attached file shows it clearer.
Thanks,
Attachments:
AC_vs_Transient_at_res.png ‏63 KB

It is basically caused by numerical error in high-Q circuits around resonance.
Here it is the link to similar discussion that I just found.
Click here to open the related post.

Problem in Multisim with transient analysis and initial conditions

Hello everyone,
I have a problem in multisim with transient analysis and initial conditions.
If I do transient analysis with automatically determined initial conditions the circuits works.
If I do transient analysis with user-defined initial conditions the circuits works in cases.
--Working with user-defined---
*## Multisim Component V2 ##*
vV2 3 0 pwl(0 0 0.001 0 {0.001+1e-008} 3 {0.001+1e-008+1} 3)
*## Multisim Component R1 ##*
rR1 3 0 10000 vresR1
.model vresR1 r( )
--Working with user-defined----------
*## Multisim Component V2 ##*
vV2 1 0 pwl(0 0 0.001 0 {0.001+1e-008} 3 {0.001+1e-008+1} 3)
*## Multisim Component U1 ##*
xU1 1 0 MEMRISTOR__MEMS__1__1
--Not Working with user-defined-------
*## Multisim Component V2 ##*
vV2 3 0 pwl(0 0 0.001 0 {0.001+1e-008} 3 {0.001+1e-008+1} -3)
*## Multisim Component R1 ##*
rR1 3 1 10000 vresR1
.model vresR1 r( )
*## Multisim Component U1 ##*
xU1 1 0 MEMRISTOR__MEMS__1__1
The costum component includes something like that:
.subckt MEMRISTOR__MEMS__1__1 plus minus PARAMS:
*Parameters values
+rmin=100 rmax=390 rinit=390 alpha=1E3 beta=0 gamma=0.1 VtR=1.5 VtL=-1.5 yo=0.0001
+m=82 fo=310 Lo=5
blah blah ...
.ends Memristor
Namely, if I combine the resistor and my custom component in one circuit, transient analysis with user defined initial conditions gives an error (timestep too small).

Hi Nik,
If possible, please post the Multisim file. This way, I can get access to all your settings.
Tien P.
National Instruments

Transient Analysis RLC circuit problem?

I am conducting a transient analysis of a series RLC circuit in multisim.
Using a 10VDC power supply, a switch, a 10 Henry inductor, a 10 Ohm resistor, and a 5 nF capacitor.
My calculations show that ILmax is 223uA at 700uS.
When I perform the transient analysis I am having the following problems:
If I choose "Automatically determine input conditions" then IL peaks at 700uS, but it peaks at 35pA instead of 223uA?
If I choose "User defined" as the initial condition then IL peaks at 223uA, but it occurs at 250uS instead of 700uS?
What am I doing wrong here?
I should be getting 223uA at 700uS???
Attachments:
transient analysis.png ‏5 KB
Transient RLC multisim.png ‏31 KB

Hi there,
How did you calculate ILmax (time and current)? What's your Multisim version?
Regards,
Fernando D.
National Instruments

Multisim Transient Analysis Stepsize Issue

Hi All,
I have a 32 second wav file that has a 1 kHz noise on it. I am trying to design a simple circuit that will remove this noise.
I am having problems with the output of the transient analysis of multisim. I have more data points that original. Here are all my steps.
Convert wav file into time domain in MATLAB with
-wavread
Save the time domain data to a txt file with matlab. This data has 1,424,800 points.
Design a notch filter with multisim. Input the data with a piecewise linear voltage source that is linked to the text file.
AC analysis of my circuit reveals that it should work, -30 dB gain at 1 kHz.
Run a transient analysis with multisim. Import the results into .tdm then into Matlab with
http://digital.ni.com/public.nsf/allkb/0EEADA99DC7D00A4862572E30037C3A2
Here is where my problem is. The output of multisim has 6,396,188 data points instead of 1,424,800. When I use wavwrite and create a new wavfile, it is 2 minutes long instead of 32 seconds like the original.
I believe my problem is the step size settings of multisim. I want to specify minimum step size but multisim does not have that option.
Any suggestions?
Thanks

Hi,
I am actually doing the same project I believe the
original poster is doing. I tried using a variety of low-pass filters
in the complete circuit and found that it did not low-pass anything.
All the filter appeared to do was to decrease the voltage of the
signal. When I used Multisim's Bode Plotter on just the low-pass filter
with a generic AC circuit, the Bode Plotter outputted the magnitude and
phase plot of what I expected the low-pass filter should have. However,
when I implemented the same low-pass filter into my circuit and
connected a Bode-Plotter, it did not output anything in the phase and
magnitude plot.
The circuit consists of (from left to right)
1) Comparator to take out a dolphin noise out of the noisy signl (the sound files are too big to attach of course)
2) Low-Pass Filter (1st order RC - while I did other higher order LPFs as well)
3) FET current-source amplifier
Both
#1 and #3 components work. It's just the low-pass filter that doesn't
for some reason in the circuit. I thought that the way I imported the
signal using Matlab's wavread command may have been incorrect. The fact
that the other two comoponents worked though makes me think otherwise.
I attached my signal .wav converter into a txt file Matlab script.
Can anyone shed light on what's going on? I am using the downloaded trial Educational version 10.1.197 of Multisim
Thanks.
Attached:
CompleteCircuit.ms10
LPFonly.ms10
saveWaveFiles.m
Attachments:
CompleteCircuit.ms10 ‏449 KB
LPF - Only.ms10 ‏108 KB

Problem with Multisim Transient Analysis TSTOP

Reference the attached PDF. Page 1 is the circuit. Page 2 is the transient simulation using nothing but default settings (TSTOP=1ms). Not convinced that the result is correct but that is not the issue. At least the result is within the range expected and the circuit is oscillating. Page 3 is the same transient simulation with TSTOP = 100u. Page 3 is with TSTOP=10u.
This is a circuit I simulated with good results in PSpice yesterday. I'm a long time (20yr) pspice user who is converting over to Multisim. I have been playing with this circuit for many hours, changing options, playing with initial conditions, applying a current pulse to the inductor to start the simulation. I get a wide variety of outputs, some in the kV range. After much effort it seems to be related to the TSTOP and TMAX settings. If I alter either of these settings from the defaults I get results outside the power supply rails. I have also tried changing TSTEP, changing initial conditions. Everything I do keeps the results the same or makes it worse.
Suggestions?
Attachments:
Transient Simulations.pdf ‏498 KB

Hi EDL,
If you are getting a large result a KV output you maybe using a three pin opamp model, use a five pin model instead.
http://digital.ni.com/public.nsf/allkb/50638645C2D0D363862571B900646F6E
I built the oscillation circuit and I added a pulse to kick start it, please have a look at it.
Tien P.
National Instruments
Attachments:
Oscillator.ms12 ‏429 KB

Number of cycles using power spectrum for getting frequency

Hi,
I have a square wave that I am getting a frequency estimate from using power and frequency estimate.vi
I was wondering if it mattered how many cycles were inputted for the frequency estimate. Also, the signal may end in between cycles.
Thanks,
Jennifer

Sorry for the vague first post. The software was already written for the device and I am just trying to understand a few things in order to make some changes.
I am measuring the speed of a turning rotor using the square wave signal generated from a pattern on the turning rotor. I need to know the frequency of the square wave in order to determine the speed of the rotor. The pulse pattern is used in power spectrum and estimate frequency icons (appears to be similar to an example program for spectrum analyzer). The speed of the rotor is variable until it reaches steady state which can take minutes or hours. Speeds are not too high (Freq 1-100Hz). Right now the measurement is set up to sample a given number of points at a given scan rate. This means that the data most likely does not end exactly as a pulse cycle ends but somewhere in the middle of a cycle.
We are interested in seeing the transient change in speed from start-up to steady-state. How short of a sampling period (i.e. # of cycles can be put into the power spectrum and estimate frequency.vi's) would give reliable measurments. Right now I just scan for a reasonable time in order to make sure I get enough pulses in order to better estimate the frequency of the pulse signal.
In the future I will work with completing pulse width measurements which most likely would be the fastest I can complete a transient measurement although my data will have a bit more fluctuations. That's due to each pulse not being exactly the same width.
Hope that gives you a better idea what's going on here.

Fourier analysis on phase shift oscillator skewed by initial buildup to oscillation?

Is there a way to start a transient analysis at time t=0, but not save simulation results until after the "transients" have died out for subsequent fourier analysis?
When doing a fourier analysis of the output of a phase shift oscillator, the THD values from simulation are much higher than those from measurements on the same circuit. I am assuming this occurs because it takes a finite length of time for the oscillator output to reach the expected output voltage magnitude and frequency. Including this transient regime in the fourier analysis would skew the results.

Hello,
You can find more information about the transient analysis at this tutorial; Configuring a Transient Analysis in Multisim and you can also find information on fourier analysis here; Configuring a Fourier Analysis in Multisim.
Hope this helps!
Regards,
Sharanya R
Market Development Engineer
National Instruments

Frequency of a Voltage Waveform

I need to analyze the frequency response of a generator set to look for dips, rises and recovery times from load changes. We are acquiring the voltage and current waveforms at 10kHz and recording them directly to a TDMS file. We need to calculate the freguency of the voltage waveform based on the time domain and end up with a file with 10kHz data points that is equivalent to the voltage and current waveforms for analysis. How can I go about doing this in DIAdem?
Many thanks in advance for your help,
Chris Wildmann

Chris
To get frequency information out of voltage/current waveform, would depend on what the voltage or current waveforms looked like. The NI guys may have some other tricks up their sleeves, they usually do.
Options as I see it.
1) Time between Zero crossings and update the frequency from periods measured. (most accurate if is zero crossing.)
2) Look at the slope between points and calculate a very rough frequency estimate. (Very fast but not very accurate)
Would seem that any FFT done would not relate at all to time domain.
Paul

Question regarding tranisent analysis and piecewise linear voltage export data

howdy,
My work with mulitism focuses on the analysis of equivalent circuits. I approach this through a transient analysis over a custom voltage input which I run through the PWL and export the data through excel for analysis, matching up the time of the transient analysis with the voltage through the circuit. Allowing me to observe the I-V performance.
The problem is the the exported data is usually an array of hundred of entries. That may or may not align with the discrete values of my custom voltage input and allow for direct analysis between real world data.
Is there a way to lock the time step (significantly reduce the number of interations) over the transient analysis to allow me to always export the same voltages. I.e only the voltages specified in my custom piecewise power source.
The reason I am interested in doing this is to generate data which directly matches up with the specified custom voltage input and that matches up with my real world experimental data and would not require me to pick through hundreds of iterations at varied voltages and cherry pick the points that compare to my real life measurements for analysis.
many thanks.

SPICE simulations doesn't have a fixed delta time, if the signal is changing rapidly the SPICE engine will slow down and take more samples and if the signal is constant it will automatically speed and take fewer samples. You cannot control the SPICE simulation sampling. One suggestion is to export an .lvm file instead of an Excel file because Multisim will convert the data to have a constant delta t which may be better for you. You can open the .lvm file with Notepad to view the format.
Tien P.
National Instruments
Attachments:
LVM export.PNG ‏46 KB

Need help in multisim 11? I want to get the transient response of RL circuit....

Need help in multisim 11?
I want to get the transient response of RL circuit....i can get the increasing exponential graph in multisim 7 during simulation.....but i am getting a decreasing exponential curve(i.e,decay response) in multisim 11 when i do the same procedure as i did in multisim 7.....how can i get the initial or growth transient response for RL circuit in multisim 11 so that i can get increasing exponential curve....which satisfies time constant = L/R

Hello,
The process is the same for any circuit (in this case it is an RC circuit which you sent me). You can find the response on the voltage (which I think it's what you're looking for) at any point of the circuit, as well as any parameter really (R,V,I,L..etc).
Please refer to the image attached (an analysis on the voltage at an inductor and the wires connected to it).
The way to set it up (once you're in the transient analysis set up) is, select the Output tab, under Variables in circuit, you can select which parameters to take. V(1) and V(2) refer to the voltage in the circuit at Net 1/2 (or wire 1/2).
This differs from the voltage change within the capacitor/inductor/resistor. If you would like to see the voltage change of an inductor/capacitor/resistor/etc, you can select under the More options box, the button Add device/model parameter, which will take you to a window to select the device type, its name (in the circuit) and the parameter which you wish to analyse. Once you click on Simulate, you can select Cursor >> Show Cursors, to view information for y and x axis (like rise time, decay time, voltage difference...etc)
Hope this helps,
Miguel V
National Instruments
Attachments:
untitled.jpg ‏178 KB

SKF for Progress Analysis

Hi,
I have successfully run progress analysis using Estimate method . As my understanding after I run CNE1, system will record POC that I maintained in Estimate table into SKF. Which report I can use to see this SKF value ?
I have checked all SKF report in PS and even in Cost Center Accounting, but the report has no data.

Hi,
Did you check the report CNE5???
Once you run CNE1 accordingly reports on CNE5 will update.
Regards,
SL

Why is my Fourier Analysis failing

Why is my fourier analysis failing? When I select fourier analysis a tab "analysis parameters" allows for "transient analysis."
Attachments:
SP2012DifAmp.ms11 ‏168 KB

Hi,
I was able to get the analysis to work by changing an option in the transient analysis settings inside the fourier analysis. You can take a look at the attached file.
Hope this helps.
Regards,
Tayyab R,
National Instruments.
Attachments:
SP2012DifAmp mod.ms11 ‏171 KB

Microphone's frequency response

Hi,
Is it possible to plot a microphone's frequency response using sound and vibration? If it's possible, can anyone tell me how?
Thanks

Hi popcorn,
If you have the Sound and Vibration Assistant with SignalExpress, there is a step you can add under Analysis - Frequency Domain Measurements called, Frequency Response.
Here's a link to an article that discusses various functions, Sound and Vibration provides. Although the article discusses LabView, many of the same functions are found in SignalExpress as well. The Frequency Response Function can be found at the bottom.
http://zone.ni.com/devzone/cda/tut/p/id/3030
Aki T.

Frequency measurement using multisim

Hi all
i'm new to multisim and i want to ask about how can we measure frequency of analog signal(ecg) using multisim oscilloscope
I will be waiting for you reply
thnx

Hi Rahul,
OK, for a bandpass filter, you should use the AC Analysis under the Simulate menu. Another method is to drag a Bode Plotter and connect it to your circuit.
For the AC Analysis of the filter respnse, this following link might help you.
Configuring an AC Analysis in Multisim
http://www.ni.com/white-paper/12690/en/
NI Multisim: AC Analysis frequency response
http://www.youtube.com/watch?v=tgCPDBtRcso
If using the Bode Plotter,
MultiSim Bode Plotter
http://www.circuitsmadeeasy.com/index.php?option=com_content&task=view&id=105&Itemid=74
Regards,
Chen_T
National Instruments
Attachments:
14Pin_Chip.ms13 ‏87 KB

Transient analysis frequency estimate

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