(5/30/17) Day 25: Frequency Dependence and Signals with Multiple Frequency Components

Day 25: Frequency Dependence

Lab: 

Signals with Multiple Frequency Components

In this lab, my team and I ran tests on a circuit containing components that were frequency dependent. In particular, these tests were to be under the special circumstance that the signal we were to generate comprised of multiple sinusoidal waves of different frequencies. This also allowed us to test out a feature of the analog discovery that sends out a "Sweep". A Sinusoidal signal that changes over time.

From these tests, we hope to gain a deeper understanding of  impedance, sinusoidal inputs, capacitor behavior, and simple frequency filtering.

Prelab:

We were first asked to determine the magnitude response (ratio of output/input voltage) at frequencies of 500Hz, 1000Hz, and 10kHz.

The parameters we had for theoretical planning were for both resistors to be 680 ohms and the capacitor to be 100nF (.1 microF).

Procedure:

After we had some theoretical values for the ratios, we set out to building the circuit. It's not very complex in its form, but it is definitely interesting behavior wise.

To test the circuit according to the manual, we had to create a custom wave form for optimal data collection.

After setting it up, we input it to the circuit and measure the output at 500Hz

Ratio calculated = 0.451

At 1kHz

Ratio Calculated = 0.412

And at 10kHz

Ratio Calculated = 0.159

 This behavior is actually spot on for our calculated behavior!

As the frequency goes up, the ratio between the two voltages decreases!

 For the next portion of the lab, we tested the same circuit but we used the Sweep function to create a sinusoidal wave that linearly changes frequency with time. The signal is supposed to start at 100Hz and increase up to 10kHz in 20ms.

Then we tested it as an input:

Just as was expected, the frequency cause the voltage to decrease at the output and can be seen as a "squashing" effect of the output waveform.