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Transient Analysis not happening in real time

Dear Community.  The circuit I am attaching is a discharge of a Non-ideal-battery in real time, it takes about one hour.  I use Analysis and Simulation Transient, User Defined parameters.  The Grapher shows the output at the digital-to-analog converter however it is not in real time.  I just want one data point per second because the discharge is rather slow, however the simulation keeps occurring in micro seconds steps.  What would be the correct parameters in Transient to make it happen in real time in one second steps? Is perhaps Transient analysis not the correct way to go about it?  Any help would be appreciated.  Thank you.    

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Message 1 of 7
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Hi erielake,

 

 

I can't view the attached file because I don't have Multisim (Desktop). Nevertheless, your problem is about configuration, not specific to the attached circuit, and applicable to Multisim Live as well.

 

"Real time" might not be the appropriate term for what you want to obtain. In fact, in Multisim Live, this sentence

 

"Simulation does not occur in real time."

 

can be read in Configuration pane under Start time and End time with Transient simulation selected and when you highlight the [?] icon.

 

You might be able to run a Transient simulation that you desire by doing these:

 

  • To simulate how your circuit behaves in 1 hour, set End time to 3600 s.
  • To get "one data point per second" check Manual time step then try setting Time step to 1 s.

 

 

Best regards,

G. Goodwin

 

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Dear Goodwin.

Thank you for taking the time.  I already have the parameters you say, or at least that is what I think.  I am in Analyses and Simulation>Transient>User Defined, TSTART=0, End Time TSTOP=3600, TMAX=1, TSTEP=1.  Are the above mentioned parameters the ones you advised?

 

The system keeps taking the data in incredible small steps, less than one micro second and approximately 1 mili second correspond to one actual second, so I am still puzzled.

 

Sincerely,

Erielake    

Message 3 of 7
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...I am in Analyses and Simulation>Transient>User Defined, TSTART=0, End Time TSTOP=3600, TMAX=1, TSTEP=1.  Are the above mentioned parameters the ones you advised?

Those are what I intend to convey but I forgot that (in Multisim Live) there are limitations imposed on time step.

 

For Maximum time step:

Maximum time step must be a number between 1e-12 and 1e-5.

 

For Initial time step:

Time step must be greater than 1e-12 and less than or equal to the maximum time step.

 

Verify if these are the same in Multisim (Desktop).

 

With these limitations alone you may still be able to properly simulate the circuit. You can just use the largest allowable time step of 1e-5 s. This will just make the simulation slower and require 100,000 times memory for data storage than what you need. You can tolerate the slowing down of simulation if you are eager to get the result. You will need 360,000,000 memory locations (1,440,000,000 bytes using single-precision floating-point data type) per quantity probed.

 

What perplexes me now is the "scaling of time" that you mentioned in your reply:

 

The system keeps taking the data in incredible small steps, less than one micro second and approximately 1 mili second correspond to one actual second, so I am still puzzled.


I haven't encountered that yet in Multisim Live. I hope other members, especially those with Multisim (Desktop) application, can help you regarding that.

 

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Message 4 of 7
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The system keeps taking the data in incredible small steps, less than one micro second and approximately 1 mili second correspond to one actual second, so I am still puzzled.

A possible cause of the problem above, is this:

 

...  I am in Analyses and Simulation>Transient>User Defined, TSTART=0, End Time TSTOP=3600, TMAX=1, TSTEP=1.  Are the above mentioned parameters the ones you advised?

Notice that the values for the parameters don't have units. Try to search from Multisim (e. g., Help) the default units for these parameters. It's likely that the default is microseconds. If that is the case, multiplying those values by 1,000,000 is supposed to give the simulation parameters that you need (e.g., TSTOP=3600000000, TMAX=1000000). Alternatively, find how to change the default unit so that you can use the values you posted in your reply and it's also possible that values with explicit units can override the default (e.g., 3600 s, 1 s). I stated above that this is "supposed" to get you to the correct parameters, this is because of the limitations on Maximum time step and Initial time step. The limitations are in my reply preceding this one.

 

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Message 5 of 7
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Dear GGoodwin,

 

Thank you again for helping me out.  I tried your idea of changing times by a factor of thousands and millions but the time is still not actual, in fact it does not seem to change anything.  The Transient window shows the units for TSTOP, TSTEP, etc are in seconds, your idea that maybe behind the scenes the time unit were micro seconds was clever but it seems that is not the case.

 

It is unfortunate you can not see my circuit in Multisim Live.

 

Sincerely,

erielake

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Have you solved this problem already? If not, can you post an image of the graph (preferably in PNG format)?

 

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