# Multisim simulation; need help

Discussion in 'Homework Help' started by beachjustice, Dec 12, 2012.

1. ### beachjustice Thread Starter New Member

Dec 12, 2012
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Hello!

Anyone have any experience with Multisim?

I'm simulating a circuit using Multisim. The details of the circuit come from a lab we're doing in class, although it's instructions are for actual hardware components.

Anyway, it was something about designing a 't-type' low pass filter. I attached a picture to this post, containing what I did in multisim and what the lab asks for beneath it.

According to the lab, the power source has to be a '5V (p-p) AC-signal'. I found the AC voltage signal generator component thingy (all the way on the left in the diagram). But in its properties there's nowhere to specify peak-to-peak value (I presume that's what p-p means?), but I did find V_(rms) field, which I set to1.7857V (peak to peak voltage divided by approx 2.8 = V_(rms) to my knowledge). So, I figure it's all the same. Otherwise, the capacitors, inductors, and resistors are just right according to what the lab asks for.

Anyway, we have to measure the voltage gain (output voltage / input voltage) at different frequencies of the input voltage signal. But the lab specifies using an oscilloscope to measure the output voltage. I wasn't sure how to read those thingies, because it didn't give me a number but a sinusoidal wave! So instead I just connected a basic voltmeter (resistance set to 10MOhm, AC mode) and it appears to give me a number that stays constant after a while, so that's more helpful to me.

As you can see in my multisim setup, with the input Vrms value set to 1.7857 and the input frequency set to 10000Hz, I get an output voltage (I presume Vrms value?) of 6.896, which I presume I need to multiply by approx 2.8 to convert to peak to peak value, and use that to calculate the gain.

I have the lab sheet below the setup i made in multisim in the image.

Anyone see anything wrong with my setup?

thx

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2. ### beachjustice Thread Starter New Member

Dec 12, 2012
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OP here. Just wanted to make a correction... as you can see in the image I uploaded with the input Vrms value set to 1.7857 and the input frequency set to 10000Hz, I get an output voltage (I presume Vrms value?) of 6.896mV. I forgot to specify the 'mV' part (I didn't in my first post).

3. ### JoeJester AAC Fanatic!

Apr 26, 2005
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1,738
When it mentioned 5V pk to pk, I think you will be using an oscilloscope in the lab.

At 10 kHz, the voltage across the load is that low.

Last edited: Dec 13, 2012
4. ### beachjustice Thread Starter New Member

Dec 12, 2012
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I see; thank you.

5. ### JoeJester AAC Fanatic!

Apr 26, 2005
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You do realize your table is the beginings of a bode plot of that filter's response.

Dec 12, 2012
4
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yes indeed

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