Multisim and Ultiboard

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Is there any difference between AC_POWER source and AC_VOLTAGE source?

Recently, I bumped into a very weird problem when I worked on this example file (please check the attached file).  I can use the original 50mVpp to get the correct v_out value around 490mVpp.  But I looked at the setting, where the rms value is 13.3mV, which I believe corresponds to 2*sqrt(2)*13.3=37.62mVpp.  Then I noticed that NI Multisim provides AC_POWER source and AC_VOLTAGE source. Therefore, I wonder whether this dilemma is due to this.


Any input will be highly appreciated. 



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Привет! Это один и тот же источник с разницей по амплитуде в 1.414213562 (2^0.5)



SPICE-параметры только перепутал, экскюз ми... А приборами не советую пользоваться, они очень замедляют счёт и вносят неточности. Пользуйтесь анализами и постпроцессорной обработкой.



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Hi Lvloverlv,


I don't have Multisim (Desktop) application, I am only a Free Subsciption user of Multisim Live. There is only one AC (Voltage) Source available to me in Multisim Live so my answer is based on my observation of the previous posts from other participants who have Multisim (Desktop) application.


When it comes to functionality there is no difference between AC_POWER source and AC_VOLTAGE source. The difference is just in the default settings (which can be later altered) for the component placed in the circuit. For AC_POWER source the default rating is in rms while for AC_VOLTAGE source the default rating is in peak voltage.


Also try to observe the default values for amplitude and frequency. I think for AC_POWER source the amplitude is high but the frequency is low while for AC_VOLTAGE source the amplitude is low but the frequency is high. Possibly, for AC_POWER source VA/Voltage (RMS) = 120 Vrms and Frequency = 60 Hz while for AC_VOLTAGE source VA/Voltage (Pk) = 1 V and Frequency = 1 kHz.


Thus, these two AC sources are the same, the presence of two variants is just for convenience to the user. It is preferable to choose AC_POWER source when working with electrical fixtures or AC machineries while it is preferable to choose AC_VOLTAGE source when working with electronic signals such as analog audio, analog video, and simulated transducer output. The reason is simply fewer settings/values to edit for initial configuration of AC source component placed in the circuit.


Feel free to inform me if this reply contains false supposition(s).




Best regards,


G. Goodwin


Message 3 of 4

Thank both of you for the kind help and efforts!


I figured out the issue with that Multisim Example from the companion CD of the textbook. Indeed as both of you have mentioned, there is no differenece between these two sources. 

The problem was that the 600 Ohm resistor is shorted and the soure was wrongly configured with 13.3mVrms, which should be 25mVp or 25/sqrt(2)mVrms. Somehow, the two negatives combination ended up with a correct solution.

Have a nice one!

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