# Multisim and Ultiboard

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## Simulated results differ from calculated results

Hello!

I have a query regarding the voltage and current results obtained through my test circuit using Multisim.

When I tried calculating the Voltage drop across the LEDs in the attached design, I could see that the calculated Voltage values comes up as 254.41 mV whereas the simulation results for Voltage is found to be 718.62 mV across the parallel combination of LEDs. Also the Right side and the left side current values through the resistors R1 (100 Ohms) and R2 (100 Ohms) came up in calculation as I1 = 28 A and I2 = 33 mA respectively, whereas the simulation results for I1 current (through R1) = 20.814 mA and  I2 current (through R2) = 25.814 mA.

Since I am not sure whether there are any default boundary conditions or tolerance values for resistors that might apply in calculating the results online using the simulator, I thought of getting a better clarification with the forum's help. It will be great if someone could review and clarify me on this question.

Attached is the screen shot of my Test circuit simulated results on Multisim.

Thanks and Regards,
Nandhini Jayapandian

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## 回應： Simulated results differ from calculated results

Hello! Regarding the LED problem, you can get the internal resistance of the LED by the LED component you set. This will find the voltage value on the picture you provided is 718.62 mV. If you choose a 1.83V20mA LED, you can calculate the resistance to 91.5 ohms.
The above information is hopeful to help you. Of course, the node voltage method can be used to calculate the proof.
Ming Ching Lui
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