This lab provides experience with capacitors, and the bench function generator and oscilloscope.
No suggested report format is provided.
Do the following exercises. Report your results in a Word document. Submit a printed copy (and the Word file to Isidore).
Use a multimeter set to AC volts to measure the rms voltage. Compare the results to the oscilloscope reading.
nominal | impedance meter | bench meter |
---|---|---|
Which measured value seems more precise?
Measure each capacitance on the impedance meter and from the rise time measurement described below. Tabulate the values and the nominal value.
# | nominal | impedance meter | calc from rise time |
---|---|---|---|
C1 | |||
C2 | |||
C3 |
Set the signal generator for a square wave. Adjust the oscilloscope to obtain a display similar to that shown below. The top trace is the signal generator output (node 1), and the bottom trace is the voltage across the capacitor (node 2).
Display the 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.
A | B | C | D |
---|---|---|---|
Calculate the expected value using the capacitance values for individual capacitors that you determined previously. Tabulate measured and calculated values.
group | impedance meter | calc from rise time | calculated from theory |
---|---|---|---|
A | |||
B | |||
C | |||
D |
Measure the AC response (as described below) using the same frequency as for the square wave measurements previously. Then vary the frequency until the phase shift is 45° and record the AC response again. The gain is the ratio of output amplitude voltage to input amplitude voltage (Vout / Vin).
capacitor | Frequency | Vin | Vout | Ratio (gain) | Phase |
---|---|---|---|---|---|
C1 | |||||
C2 | |||||
C3 | |||||
To determine the AC response, you will need to record the following measurements from the oscilloscope.
These measurements can all be made using the electronic tools in the oscilloscope.
The image below shows a sample measurement. The input waveform is on the top and
the output waveform is on the bottom.
Maintained by John Loomis, last updated 18 October 2012