In this lab, we will focus on measuring the phase difference between AC sinusoidal signals at the same frequency. In this lab, we will use an integrated function generator and oscilloscope. In this lab, we will learn how to read the oscilloscope, calculate the phase shift and also the time difference to show which signal lead or lag which.
Experimental
The function generator and the o-scope used is as follow:
Vrms from o-scope = 2.489 V
Vrms from DMM = 2.13V
The complex impedance of the 100 nF capacitor was then calculated:
Z= 1/jwC = -1591j
After the impedance is calculated, this circuit was built:
The graph from the o-scope obtained is as follow:
The data taken is as follow:
Vpk-pk = 5.64V
Vrms from DMM = 1.70V
The value of the voltage doesn't reconcile.
The time difference measured is 81µs
The phase angle between the 2 signals are 39.2 degree which also means that R leads C
Once all the data has been taken the frequency is increased to 10kHz.
The new impedance was calculated to be 159.2 ohm
again the graph is captured as shown below
The data is taken and listed below:
Vpk-pk = 1.06V
Vrms = 0.06V
The value between DMM and o-scope is again off by 0.3
The time difference between peak is 24.32µs
the phase angle between two signals is 87.6 degree
For the next part, the frequency is turned back to 1 kHz and the resistance box is set to 10kohms
The data taken is shown below:
Vpk-pk = 1.21V
Vrms = 0.32V
The value again does not reconcile.
The time difference between peak is 232.43µs with phase angle of 83.7 degree
R = 1.8kohms
Vrms = 1.23V
time difference for this is 135.14µs with phase angle of 48.65 degree.
Conclusion and Questions
When the FG is on high frequency, the amplitude gets smaller while on low frequency, the amplitude gets higher. This is similar a low pass filter where it will pass all the low frequency and as it gets to higher frequency, the signal gets smaller. The resistor leads as frequency gets higher and at high frequency, the phase angle tend to be at 90 degree.
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