# Reliability of Multisim Simulations: Can We Trust the Results?

• Crazymechanic
In summary: The most likely reason is that you changed something in the circuit while it was still in the simulation, and the new simulation doesn't take into account the changes you made.
Crazymechanic
Hi folks I would like to know maybe someone has some insight if you make a circuit in multisim (I have the 12 edition) and u go through everything then you run the simulation and it shows that all is ok and working like you thought it should what are the chances that multisim could be lying? I know it sound stupid but are there any errors or bugs in that program so that when I would build that circuit on real board it would not work?

Thanks.

Usually if you have a problem where the circuit works in the simulation but not in real life, the problem is not with the accuracy of the simulator, but with something you left out of the simulation. For example, in your simulation you usually assume all circuit elements are connected directly to the power supply, but in real life the elements are connected to the power supply through wires which have resistance and inductance. Or perhaps you assume that all elements are at the same temperature when in real life power dissipation in the elements makes them have slightly different temperatures. A very common problem is in statistical variation of the elements. I don't know if you are talking a circuit made with discrete elements or an integrated circuit, but in both cases the elements vary. How robust is your circuit if the elements don't have the values (width, length, resistance, capacitance, etc.) that you assumed, but instead vary by say 20%? What if one is 20% too large and another is 20% too small? Try thinking along these lines and see if you can make your circuit robust enough to tolerate variations.

I actually played pretty much with these things. especially with resistor values i made tolerances like some 30% and it still works atleast the main thing what it has to do it does.
also I tried different voltages in and it worked .
I'm talking about a smps few mosfets driven by astable multivibrator.
The only thing I can't understand is that ok i feed the circuit from a dc power source in multisim everything's ok all measurments real.
Then I put an ac source through a bridge rectifier and some inductors before and nothings happening no matter what diodes i use i get only some 99 volts on the dc side even with a normal size electrolytic capacitor.
I put ground too and all is fine.I can't seem to understand why is multisim making this error?

Crazymechanic said:
...Then I put an ac source ...

"AC source" (VAC) in Spice is for small signal AC analysis (small signal transfer functions). You want to use a sinusoidal source (VSIN) in a transient analysis.

AC into rectifiers and a capacitor will give the peak value of the AC.
AC into rectifiers and a inductor will give the average value of the AC.

One more thing I can't understand is that when I have made a circuit that's working great now I save and close that multisim file and make another one where I experiment with some parts.then when done experimenting I make everything back as it was in my other tested version and in this one the circuit doesn't work.
How come if in the previous simulation the same circuit the same parts everything worked great and in a new one nothing works?

## 1. What factors can affect the accuracy of Multisim simulations?

The accuracy of Multisim simulations can be affected by various factors such as the precision of component models, the complexity of the circuit, the type of analysis being performed, and the quality of the input data.

## 2. How can I improve the accuracy of my Multisim simulations?

To improve the accuracy of Multisim simulations, you can use more precise component models, simplify the circuit design, perform multiple simulations with different input values, and verify the results with physical measurements.

## 3. Is Multisim simulation accurate enough for real-world applications?

Multisim simulations can provide accurate results for many real-world applications, but it is always recommended to verify the results with physical measurements before implementing the circuit design in a real-world setting.

## 4. Can Multisim simulate all types of circuits?

Multisim is capable of simulating a wide range of circuits, including analog, digital, and mixed-signal circuits. However, certain types of circuits, such as high-frequency circuits, may require specialized simulation tools for accurate results.

## 5. How does Multisim handle non-linear components in a circuit?

Non-linear components, such as diodes and transistors, can be accurately simulated in Multisim by using appropriate models and specifying the operating conditions. Multisim also offers advanced simulation options, such as Monte Carlo analysis, to account for the variability of non-linear components.

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