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8.5: Procedure

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  • 8.5.1: RC Circuit

    1. Using Figure 8.4.1 with Vin = 2 V p-p sine at 10 kHz, R = 1 k\(\Omega\), and C = 10 nF, determine the theoretical capacitive reactance and circuit impedance, and record the results in Table 8.6.1 (the experimental portion of this table will be filled out in step 5). Using the voltage divider rule, compute the resistor and capacitor voltages and record them in Table 8.6.2.

    2. Build the circuit of Figure 8.4.1 using R = 1 k\(\Omega\), and C = 10 nF. Place one probe across the generator and another across the capacitor. Set the generator to a 10 kHz sine wave and 2 V p-p. Make sure that the Bandwidth Limit of the oscilloscope is engaged for both channels. This will reduce the signal noise and make for more accurate readings. Also, consider using Averaging for the acquisition mode, particularly to clean up signals derived using the Math function.

    3. Measure the peak-to-peak voltage across the capacitor and record in Table 8.6.2. Along with the magnitude, be sure to record the time deviation between \(V_C\) and the input signal (from which the phase may be determined). Using the Math function, measure and record the voltage and time delay for the resistor \((V_{in} – V_C)\). Compute the phase angle and record these values in Table 8.6.2.

    4. Take a snapshot of the oscilloscope displaying \(V_{in}\), \(V_C\), and \(V_R\).

    5. Compute the deviations between the theoretical and experimental values of Table 8.6.2 and record the results in the final columns of Table 8.6.2. Based on the experimental values, determine the experimental Z and \(X_C\) values via Ohm’s law \((i = V_R/R, X_C = V_C/i, Z = V_{in}/i)\) and record back in Table 8.6.1 along with the deviations.

    6. Create a phasor plot showing \(V_{in}\), \(V_C\), and \(V_R\). Include both the time domain display from step 4 and the phasor plot with the technical report.

    8.5.2: RL Circuit

    7. Replace the capacitor with the 10 mH inductor (i.e. Figure 8.4.2), and repeat steps 1 through 6 in like manner, using Tables 8.6.3 and 8.6.4.

    8.5.3: RLC Circuit

    8. Using Figure 8.4.3 with both the 10 nF capacitor and 10 mH inductor, repeat steps 1 through 6 in similar manner, using Tables 8.6.5 and 8.6.6. Using a four channel oscilloscope: To obtain proper readings, place the first probe at the input, the second probe between the resistor and inductor, and the third probe between the inductor and capacitor. Probe three yields \(V_C\). Using the Math function, probe two minus probe three yields \(V_L\), and finally, probe one minus probe two yields \(V_R\). Assigning Reference waveforms can be useful to see all of the signals together. Using a two channel oscilloscope: Unfortunately, it will be impossible to see the voltage of all three components simultaneously with the source voltage using a two channel oscilloscope. To obtain proper readings, place the first probe at the input and the second probe across the capacitor in order to see the phase and magnitude of \(V_C\). Then, swap C and L (placing the second probe across the inductor) to see \(V_L\), and finally, swap L and R (with the second probe across R) in order see \(V_R\).

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