Fourier analysis black screen

[spirou1314]

Hi,

We have been simulating a sigma delta modulator in Multisim. Transient analysis is working as expected, but when we try Fourier analysis it simulates for some time and when finished there's only a black (or white) screen. No text, no graph. What are we doing wrong?

Thanks! Espen

[ikaiser]

Hi Espen!

I opened your file with my Multisim 14.1. Is that the version you are using as well?

Simulate » Analyses and Simulation » Transient works well for me, too. I used the values the configuration had and got this result:

Is that how you expect it to look?

Regarding Simulate » Analyses and Simulation » Fourier I got the same result as you: One tab per output variable defined in the Grapher, but no content:

When I checked the simulation output (I had to resize it to see everything), I found this:

Looks like the simulation fails. SC11 and SC12 are two of your nets used. Renaming (including lower-/upper-case only) does not make the simulation work. Putting the nets as output parameters instead of these probes does not work either. Removing the nets from the output parameters and putting probes onto "normal" wires instead works. However that's not the signals you want to see. I don't have a solution yet.

[ikaiser]

I found the cause. Looks like the default net names containing a slash ("/") are problematic in Fourier analyses.

I renamed the nets your probes are on from e.g. "SC12/DAC" to "SC12DAC". Seems like special characters like slashes, dashes, and underscores break the simulation. Without them it works:

 To rename, just double-click the net's wire on the diagram; then override the default name by typing in a Preferred net name. Repeat for all nets that have probes / all nets that were shown in the "no such vector" message.

1=double-click wire; 2=new name without special characters; 3=check renaming

[spirou1314]

Hi Ingo!

Thank you! I've tried your solution but I still get the black screen and the same error messages you saw, both with the probes and with adding the nets directly. The nets are now called SC11-BUFFER-IN and SC12-DAC (double checked in the net spreadsheet view).

Those are the two signals I am interested in doing a fourier analysis of, and I am using Multisim 14.1.

Espen

[ikaiser · Accepted solution]

Hi Espen,

Thank you for your quick answer!

Seems like special characters like slashes, dashes, and underscores break the simulation. 

---

Rename your nets to SC11BUFFERIN and SC12DAC and it will work (-;

Attached is the version of your design file that works for me.

P.S.: I filed a bug report with NI

[spirou1314]

Thank you! That solved it 🙂

Have a great day!

Espen