Multisim 14.0 Current Clamp causes convergence problem

[rpdavis]

I search and could not find any comments about the Current Clamp causes convergence problem so I thought I would post this.

A word of warning, I’m using Multisim 14.0 and have noticed in my MOSFET switching circuits the Current Clamp causes convergence problems. This usually happens when I connect it to the source side of the FETs.  But in one case I placed it on the plus side of a capacitor and got a convergence issue.  Then moving to the negative side of the capacitor and it worked fine.  The Current clamp is a nice feature but NI has some work to be done to improve its usability.

I’m not looking for help because there is no solution until NI fixes the convergence problems with the current clamp. I’m just putting info out there in case other run into the problem.  The only help I can suggest is to try move it on the other side of the component and if you are lucky it will work.

[Rscd27]

Hello rpdavis!

Can you guide me in how to reproduce this issue? I checked our internal documentation and I did not found any CARs related to this issue. By doing this I can create one in order correct it for future Multisim versions.

I also will require your OS version and some details about your system. If you want I can create a Service Request to work with you in a better way.

Warm Regards,

Randy

Applications Engineering

[rpdavis]

Randy,

Thanks for your interest in the current clamp convergence problem.  I attached a zip file with the circuit that causes the problem.  With the current clamp on the source of Q3 I get the error and if I move the current clamp on the negative side of C2.  Then start the simulation it runs fine.  Move it back to Q3 and it has the problem. 

I have seen this error with several different circuits and in several different placements of the current clamp. Putting the current clamp in one place and the circuits run fine then moving it causes the convergence problem.

My OS is Windows 7 Enterprise 64 bit with an Intel i7-4770 @ 3.40GHz and 8GB Ram.

Hopefully you can reproduce my problem.

Rpdavis

[rpdavis]

Hello Randy,

Were you able to duplicate the problem with the circuit I uploaded?

Thanks

rpdavis

[Rscd27]

Hello rpdavis,

I was able to reproduce the issue and I founf tha this KB that helped to increase the simulation time and avoud the convergence error:

http://digital.ni.com/public.nsf/allkb/A65253BD02F585CD86257A6B0049945D

As you can see in my screenshot I was able to simulate for more time changing those parameters. I will suggested you to try different values and delete the components that are unwired such as one ground

.

Please let me know if you got better results than me!

Regards

[rpdavis]

Thanks Randy.

Oops, I missed a no connect.  I deleted a bunch of stuff from the circuit that you did not need just to see the current clamp problem.

As stated before I did not need help getting the circuit to work because I know there are workarounds as you have suggested.

What I said is the current clamp tool causes a convergence problem in a working circuit and NI needs to fix their tool.

The current clamp is a great tool I just wish I did not need to do work arounds to get it to function in working circuits.

Thanks again for taking a look at it and duplicating the current clamp convergence issue.

rpdavis

[Rscd27]

Hello,

I am glad that now is working. Usually convergence errors are really annoying and difficult to debug. Please remember to mark the forum as solved!

Let me know if you have more questions!

Warm Regards,

Randy Cespedes

Applications Engineering

National Instruments

www.ni.com/support

[rpdavis]

I’m sorry I guess I was not clear.

The Multisim current clamp should work anywhere users place it in a WORKING circuit and should not cause a convergence problem. If the circuit simulation is running fine and we add any Multisim tool to the circuit it should continue to simulate.  This is the way a well-designed Multisim tool should function and how NI should want it the tools to function.

So until NI corrects how the current clamp tool interacts with the circuit the problem will not be solved.  There are only work arounds, as you pointed out, that users will have to continue to struggle with problems until it is fixed.  In my mind a work around is not a solution just a temporary Band-Aid for the problem.

Please go back and read my first post, the only reason I pointed this problem is so others will know someone else is struggling with the same problem.

Again I thank you for confirming the current clamp tool has a bad interaction with a working and simulating circuit.

rpdavis