How do I do worst case analysis?

[ronquan]

How do I do worst case analysis.  The set-up parameters make no sense to me. 

Thank you,

ronquan

[Tayyab_R]

Hi ronquan,

If you would like to see an example of a worst case analyses, you can open the examples folder by clicking the blue open button in the toolbar and selecting the example called SpeechFilter. This example demonstrates a worst case analysis.

Hope this helps.

[ronquan]

Hello Tayyab:

Thanks for the info.  I did a Worst case analysis on a Wein bridge circuit as it is shown one of the NI tutorials.  The d-c w.c. simulation seemed to work OK except the output d-c voltage was different from that shown the tutorial, but still seemed reasonable, although I didn't try determine what it should be.  The output showed two runs, a nominal one and a worst case run with the values required for the worst case run listed in the table.

Then I tried to do the same for our circuit, which is also fairly simple, containing a 555 timer, some transistors, an a-c source and some more passive components.

The simulation showed only one run, a nominal run with all components unchanged in value.  It is not computing any worst-case values.

I cannot show the circuit.

What could be wrong?

Thanks, again,

ronquan

[Tayyab_R]

Hi ronquan,

It is not possible to determine what is causing this behaviour without having a look at your circuit. Is it possible for you to send us the circuits.

[ronquan]

Hello again Tayyab R.

It turns out that I am able to send the circuit.  I can't get worst case to work and also I can't get monte carlo to work.  If you can get these to work that would be appreciated and let me know, if you can, what I need to do to get them to work.  Assume the input frequency range is from 100 Hz to 3,000 Hz.  I'm analyzing monte carlo out to about 25 mSec per run and doing 15 runs.

I will want to do both the d-c and a-c worst case analysis.  I tried the a-c worst case and that didn't seem to work either.  I may not have understood what I needed to do there though.  Any light you or someone can shed on this would be appreciated.

Thank you, again.

We have MultiSim 11.0.458 with at first major update (from the "About MultiSim" Help menu).

ronquan

[ronquan]

To Tayyag an Tien:

Actually I want to do the monte carlo analysis out to about .25 seconds.

Thanks,

Ron Quanrude

[Tayyab_R]

Hi ronquan,

I looked into your circuit and why the analysis was not yielding any results and it turns out that the 555 timer was causing a fatal memory allocation error. I got a new spice model for the 555 timer from the internet and made a new 555 timer component and then the simulation seems to be working.

I have attached the modified circuit with this post. Just right-click the 555 timer and select Save Component to DB and add this new timer to your User Database.

Hope this helps.

[ronquan]

Hello Tayyab:

My MultiSim wasn't able to open the file you sent.  A couple of pictures are attached showing the message and my MultiSim version.  Can you save it so I can open it?

Thanks,

ronquan

[Tayyab_R]

Hi ronquan,

As long as you are running Multisim 11, you should be able to open the file. I downloaded and opened the file again just to make sure it didn't get corrupted somehow when I uploaded but it seems to work. I would suggest try to download again and open it.

I dont see the screen shots you were mentioning so if the issue is still there, please post the screen shot as well.

[ronquan]

Ok, It opened this time.

Thanks,

ronquan