major simulation bug with 10.1.197

[NavyJay]

Hi All,

Can anyone confirm the following major simulation bug in Multisim Power Pro 10.1.197?

If I create a new circuit and simulate it, everything appears to behave correctly.  However, when I begin making modifications to the passive component values the circuit is not simulating with the specified values.  The exported netlist shows the incorrect values of R's and C's most likely used in an AC analysis.  The attached ms10 and CIR file show an example.  Note that I'm using 2.0nF caps, but the netlist specifies two 33pF caps and a 220pF cap instead.  What gives???

The spreadsheet view displays the correct passive values, but the exported netlist does not.  The interactive simulation results match the AC analysis, but it does not appear correct.  I'm spending quite a lot of time on this issue that should seem trivial.  Anyone running into similar problems?

-Jason 

[lacy]

I may have found the problem about the export net list being incorrect. I tried this as you suggested and sure enough when I viiewed the net list the capacitors were listed as the wrong value. I then checked to see if you were using a tolerance value for your capacitor and it was set to zero.

I then tried something to see if it would work. I went to SIMULATE>USE TOLERANCES and clicked it so that a check mark was beside it (I am assuming this indicates it is active) and then tried to export the netlist again. This time it put the correct value in the ouput netlist. So I am going to assume that without the tolerances being active Multisim is using a default tolerance when exporting the net list. I do not believe this should be happening and could be a program bug that you have found.

This may also be what is happening on the simulation side. Try doing the above and see if the results are more to your liking. I haven't had time to analyze this portion yet and it may take me a while. So if you try this before I get back to you and it works let me know.

[lacy]

I think that this arbitrary assigning of a tolerance for the capacitors was what was cauising both situations. I tried a bode plot before and after activating the USE TOLERANCE" setting  and my results show that the first bode plot was not correct, but the second one appeared to have the correct plot.

Try it and let me know if I am correct. If so, then this definitely need attention from NI.

[NavyJay]

Hi Lacy,

I think you may have found a temporary "fix" for this bug, but the "Use tolerances" flag isn't intended to work this way.  Simply toggling the flag on and off again will refresh the parts to the correct values. Note that this bug is also repeatable by copying any of the passive parts from the previously attached schematic into a new Multisim circuit.

If you look at the "Description" entered for these components under spreadsheet view, those are the approximate values erroneously being inserted into the netlist, not the numbers entered in the "Value" column.  I'm not quite sure why the description was filled out for these parts, but I suspect it's from initially being imported from an OrCad drawing.

So, for now, toggling the "Use tolerances" appears to force the netlist to use the correct value.  I suppose removing the description for each part may also work, but haven't tried it yet.

Thanks for you quick response.  It's very helpful as usual.

Jason 

[lacy]

Yes, I see what you mean. The problem is that I do not see a way right now of changing the description box. The spreadsheet won't allow you to edit this box for some reason. The only way to rid yourself of this is to replace all the components that have descriptions or use the option I presented in the previous post. If you notice the resistors are also listed wrong in the description box.

I agree this behaviour is not nor should be normal.  I also realize that the option I presented before is not the normal way that should work but it sure beats having to go through a large design and change every part. The description box in the spreadsheet should not take precendent over the set value. The description box should be just a part description that has no bearing on the simulator results.

I do know one thing is the fact that when importing files from another package strange things can occur. This is due, in my opinion, to Multisim not being 100% compatible with these other packages.

Thank you for pointing out this psssible bug as I am sure it will help other users also.

From this point, NI will have to address this. I am interested in their thought on this. I would also like to know how to go about editing the description box if that is possible.