ECE 201L Circuit Analysis Laboratory
Lab 5

This lab explores the transient and AC behavior of capacitors and inductors.

Do the following exercises. Report your results by writing a Word document and submitting it in Isidore. Submit one report per group.

  1. Pick two inductors from 1-10 mH. Measure the inductance of two different inductors on the impedance meter, separately, in series, and in parallel. Compare measured values of series and parallel combinations with values calculated from measurements of the individual inductosr.

    ComponentMeasuredCalculated
    L1
    n/a
    L2
    n/a
    L1 + L2

    L1 || L2

  2. Construct the following RC circuit. Use a resistance of 100-500Ω and a capacitance of 1-100μF.

    Use a function generator to produce a square wave and observe the signal on the oscilloscope. Adjust the frequency to produce a waveform something like the example below.

    Display the frequency and rise and fall times on the measurement line. Capture at least one image to include in your report.

    Calculate the time constant from the rise/fall times, trise = 2.2 τ. Also calculate the time constant τ = RC. Explain or discuss any differences between these calculations.

  3. Construct the following LR circuit. Use a resistance of 100-500Ω and an inductance of 1-10 mH. .

    Use the oscillocope as before and display the frequency and rise and fall times on the measurement line. Capture at least one image to include in your report.

    Calculate the time constant from the rise/fall times, trise = 2.2 τ. Also calculate the time constant τ = L/R. Explain or discuss any differences between these calculations.

In each of the following exercises you will need to record the following measurements from the oscilloscope.

  1. Build the circuit shown below, using the same resistor and inductor as in exercise 3 above. In this exercise, set the signal generator for a sine wave.

    Vary the frequency until the phase shift is 45° and record the AC response. The gain is the ratio of output amplitude voltage to input amplitude voltage (Vout / Vin).

  2. Replace the inductor with the capacitor from exercise 2 above, as in the circuit below, and repeat the measurement.

    componentFrequencyVin VoutRatio (gain)Phase
    L




    C




    The frequency recorded above, and the measured value of the resistor can be used to calculate the capacitance or inductance. Verify this calculation by comparing to the value measured on the impedance meter.

    componentcalculated valuemeasured value
    L

    C

  3. Construct the following circuit

    This is a resonant circuit. Adjust the frequency to give maximum output signal. Record the AC response (voltage and phase). Change the frequency higher and lower until the gain (ratio of output to input amplitude) has dropped to 0.707 of the peak gain. Repeat the measurement using a different resistance.

    Case 1

    FrequencyVin VoutRatio (gain)Phase















    Case 2

    FrequencyVin VoutRatio (gain)Phase















    Component Measurements

    CaseRLC
    1


    2


  4. Calculate the resonant frequency, bandwidth and Q values for the two sets of measurements above. Bandwidth is the difference between the higher and lower frequencies where the gain drops by 0.707 of its peak value. Compare with the theoretical expressions for the resonant frequency and Q value:

           

    CaseMeasuredCalculated
    Resonant frequencyBandwidthQResonant frequencyBandwidthQ
    1





    2






Maintained by John Loomis, last updated 22 October 2012